CN107354446B - A kind of method that chemical gaseous phase synthesizes ultra-thin carbon nanosheet - Google Patents

Abstract

The invention discloses a kind of methods that chemical gaseous phase synthesizes ultra-thin carbon nanosheet.The present invention uses solid catalyst template, and gas phase carbon source synthesizes ultra-thin carbon nanosheet, and carbon nanosheet size is big, thickness is small.Ultra-thin carbon nanosheet can be used for the energy storages device such as lithium ion battery and sodium-ion battery.

Description

A method for chemical vapor phase synthesis of ultrathin carbon nanosheets

technical field

The invention relates to a method for preparing ultra-thin carbon nanosheets by using chemical vapor phase synthesis technology, in particular to a method for synthesizing ultrathin carbon nanosheets by using a solid catalyst template and a gas phase carbon source, and belongs to the field of carbon material synthesis.

Background technique

Two-dimensional carbon materials have unique structures and excellent physical and chemical properties, such as large specific surface area, good electrical and thermal conductivity, and mechanical properties. They have huge applications in optoelectronic devices, composite materials, biosensors, and especially energy storage devices. prospect. At present, the preparation methods of two-dimensional carbon materials mainly include mechanical exfoliation, chemical redox technology and chemical vapor deposition technology. Although the mechanical exfoliation method can obtain high-quality graphene and has excellent electrical properties, the yield is low and it is not suitable for large-scale preparation; although the graphite redox technology can be prepared in large quantities, the two-dimensional material produced has many structural defects and graphitization. The degree is low, the mechanical properties and electrical conductivity are poor, and strong acids, strong oxidants and reducing agents are used in the process, the process is cumbersome and the pollution is large; the use of metals such as copper foil as catalyst template chemical vapor deposition preparation process is harsh and needs to be transferred. Low, not suitable for mass production; while using metal oxides as templates to prepare two-dimensional carbon nanomaterials, it is also necessary to prepare nanostructured oxides through a series of chemical reactions in advance, and then synthesize two-dimensional carbon materials [vertical graphene nanosheets Porous hierarchical carbon microrods and their applications in lithium-ion batteries, "Journal of Materials Chemistry A", 2015, Volume 3, Page 19800]; using diatomaceous earth as a template to grow two-dimensional carbon materials, the process requires not only silicon Nitric acid and sulfuric acid are used for pre-etching of algae, and hydrofluoric acid or strong alkali is needed to remove the template after growth at a high temperature of 1000 °C [Bio-template CVD preparation of three-dimensional graphene powder: leading to efficient solution processing, "Nature Communications ", 2016, Volume 7, Page 13440], the process is complicated and the pollution is large. The development of simple, low-cost and green two-dimensional carbon material preparation methods is the key to its application in various fields.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a two-dimensional ultra-thin carbon nanosheet powder that is pollution-free, low-cost, simple in process and easy to prepare in batches.

The invention adopts a solid catalyst template and a gas-phase carbon source to synthesize ultra-thin carbon nanosheets, and the obtained carbon nanosheets have large size and small thickness, and can be prepared in a large scale.

A method for chemical vapor phase synthesis of ultra-thin carbon nanosheets, characterized in that the method synthesizes ultrathin carbon nanosheets in a vacuum tube furnace, the vacuum tube furnace is mainly composed of a vacuum system, a gas supply system, and a temperature rise control system, and the specific process is as follows: :

1) Place the solid catalyst template in a vacuum tube furnace;

2) Vacuumize the vacuum tube furnace to below 200Pa, feed inert gas or argon-hydrogen mixed gas to atmospheric pressure, heat up to the synthesis temperature, and feed gas phase carbon source, after the synthesis is completed, cool to room temperature under the protection of the atmosphere to obtain a solid product ;

3) Washing, suction filtering and drying the above solid to obtain ultra-thin carbon nanosheet powder.

The solid catalyst template of the present invention is lithium carbonate, sodium carbonate, potassium carbonate, potassium chloride, sodium chloride, sodium sulfate or potassium sulfate.

The gas phase carbon source described in the present invention is selected from acetylene, ethylene or methane.

The synthesis temperature of the present invention is 600-900° C., and the synthesis time is 1-150 min.

The ultra-thin carbon nano sheet prepared by the invention is a two-dimensional layered structure with a size of 5-50 μm and a thickness of 2-30 nm.

The present invention has the following advantages:

1) The solid catalyst template used is cheap and does not require pretreatment;

2) The synthesis temperature is low, the operation is simple and controllable, and the repeatability is good;

3) Use deionized water for cleaning, no strong acid/alkali is used in the process, which is environmentally friendly and pollution-free.

Effects and benefits of the present invention: a method for preparing ultra-thin carbon nanosheets on a simple scale is provided, the raw materials used for the preparation are abundant, cheap and easy to obtain, environmentally friendly, repeatable, and the product quality is stable and reliable; it opens up a new two-dimensional The invention discloses a method for preparing ultrathin carbon nanosheets, and the prepared ultrathin carbon nanosheets can be used in energy storage devices such as lithium ion batteries and sodium ion batteries.

Description of drawings

Figure 1 is a TEM photo of the ultrathin carbon nanosheets obtained in Example 4 of the present invention.

Figure 2 is the Raman spectrum of the ultra-thin carbon nanosheets obtained in Example 4 of the present invention.

Detailed ways

Example 1

Put the sodium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, pass in argon to atmospheric pressure, and pass in hydrogen (20% of the volume of argon), raise the temperature of the tube furnace to 750°C, and pass in Acetylene (20% of the volume of hydrogen gas), keep warm for 40min, stop feeding acetylene, cool down to room temperature naturally, take out the sample, wash the above solid sample with deionized water, suction filter and dry at 60°C to obtain ultra-thin carbon Nanosheet powder. Scanning electron microscopy (SEM) results showed that the samples had larger sizes.

Example 2

Put the sodium chloride powder in a vacuum tube furnace, evacuate to below 200Pa, pass in argon to atmospheric pressure, raise the temperature of the tube furnace to 700°C, pass in acetylene (5% of the volume of argon), and keep it warm for 40min , stop feeding acetylene, and cool down to room temperature naturally, then take out the solid sample. The above solid sample was washed with deionized water, suction filtered and dried at 60°C to obtain ultrathin carbon nanosheet powder.

Example 3

Put the potassium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, pass in argon to atmospheric pressure, and then pass in hydrogen (20% of the volume of argon), raise the temperature of the tube furnace to 850°C, and pass in Acetylene (20% of the hydrogen volume), keep warm for 40min, stop feeding acetylene, cool to room temperature naturally, and take out the solid sample. The above solid sample was washed with deionized water, suction filtered and dried at 60°C to obtain ultrathin carbon nanosheet powder.

Example 4

Weigh the sodium carbonate powder and place it in a vacuum tube furnace, evacuate it to below 200Pa, pass in argon to atmospheric pressure, and then pass in hydrogen (20% of the volume of argon), raise the temperature of the tube furnace to 800°C, pass Add acetylene (20% of the volume of hydrogen gas), keep warm for 40 minutes, stop feeding acetylene, cool down to room temperature naturally, and take out the solid sample. The above solid sample was washed with deionized water, suction filtered and dried at 60°C to obtain ultrathin carbon nanosheet powder. Figure 1 is a transmission electron microscope (TEM) image, and the results show that the thickness of the sample is small. It can be seen that the thickness is 4nm through the atomic force microscope test, and it has certain crystallization characteristics through the Raman spectrum (Raman, Figure 2) test.

Example 5

Put the potassium sulfate powder in a vacuum tube furnace, evacuate to below 200Pa, pass in argon to atmospheric pressure, and then pass in hydrogen (20% of the volume of argon), raise the temperature of the tube furnace to 800°C, and pass in Acetylene (20% of the hydrogen volume), keep warm for 40min, stop feeding acetylene, cool to room temperature naturally, and take out the solid sample. The above solid samples were washed with deionized water, suction filtered and dried at 80°C to obtain ultra-thin carbon nanosheet powders. TEM results showed that they had an obvious two-dimensional sheet structure.

Example 6

Put the sodium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, pass in argon to atmospheric pressure, and then pass in hydrogen (10% of the volume of argon), raise the temperature of the tube furnace to 650°C, and pass in Acetylene (5% of the hydrogen volume), keep warm for 150min, stop feeding acetylene, cool to room temperature naturally, and take out the solid sample. The above solid sample was washed with deionized water, suction filtered and dried at 80°C to obtain ultrathin carbon nanosheet powder. SEM results showed that the sample had a good lamellar structure.

Example 7

Place the lithium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, feed nitrogen to atmospheric pressure, and then feed hydrogen (10% of the volume of nitrogen), raise the temperature of the tube furnace to 600°C, and feed acetylene ( 5% of the volume of hydrogen), keep warm for 10 minutes. Subsequently, the acetylene was stopped, and after cooling to room temperature naturally, the solid sample was taken out. The above solid sample was washed with deionized water, suction filtered and dried at 80°C to obtain ultrathin carbon nanosheet powder. Scanning electron microscopy (SEM) results showed that the sample had a good lamellar structure.

Example 8

Put the potassium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, pass nitrogen to atmospheric pressure, and then pass hydrogen (20% of the nitrogen volume), raise the temperature of the tube furnace to 900°C, and pass acetylene ( 20% of the hydrogen volume), keep warm for 2 minutes, stop feeding acetylene, cool to room temperature naturally, and take out the solid sample. The above solid samples were washed with deionized water, suction filtered and dried at 80°C to obtain ultrathin carbon nanosheet powders. TEM results showed that they had an obvious ultrathin two-dimensional sheet structure.

Example 9

Put the potassium chloride powder in a vacuum tube furnace, evacuate to below 200Pa, pass nitrogen to atmospheric pressure, and then pass hydrogen (20% of the nitrogen volume), raise the temperature of the tube furnace to 880°C, and pass methane (50% of the hydrogen volume), keep warm for 10 minutes, stop feeding methane, cool to room temperature naturally, and take out the solid sample. The above solid samples were washed with deionized water, suction filtered and dried at 80°C to obtain ultrathin carbon nanosheet powders. TEM results showed that they had an obvious ultrathin two-dimensional sheet structure.

Example 10

Put the sodium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, feed nitrogen to atmospheric pressure, and then feed hydrogen (30% of the nitrogen volume), raise the temperature of the tube furnace to 880°C, and feed ethylene ( 20% of the hydrogen volume), keep warm for 2 minutes. Subsequently, the feeding of ethylene was stopped, and after natural cooling to room temperature, the solid sample was taken out. The above solid samples were washed with deionized water, suction filtered and dried at 80°C to obtain ultrathin carbon nanosheet powders. TEM results showed that they had an obvious ultrathin two-dimensional sheet structure.

Example 11

Put the potassium carbonate powder in a vacuum tube furnace, evacuate to below 200Pa, feed nitrogen to atmospheric pressure, raise the temperature of the tube furnace to 880°C, feed ethylene (10% of the volume of nitrogen gas), keep it warm for 60 minutes, and stop the ventilation. Add ethylene, cool to room temperature naturally, and take out the solid sample. The above solid samples were washed with deionized water, suction filtered and dried at 80°C to obtain ultra-thin carbon nanosheet powders. TEM results showed that they had an obvious two-dimensional sheet structure.

Claims (1)

1. A method for chemical vapor phase synthesis of ultra-thin carbon nanosheets, characterized in that the method synthesizes ultrathin carbon nanosheets in a vacuum tube furnace, and the vacuum tube furnace is mainly composed of a vacuum system, a gas supply system, and a temperature rise control system, specifically The process is: 1) placing the solid catalyst template in a vacuum tube furnace; the solid catalyst template is lithium carbonate, sodium carbonate, potassium carbonate, potassium chloride, sodium chloride, sodium sulfate or potassium sulfate; 2) Vacuumize the vacuum tube furnace to below 200Pa, feed inert gas or argon-hydrogen mixed gas to atmospheric pressure, heat up to 600-750°C, and feed gaseous carbon source, cool to room temperature under atmosphere protection after 1-150min, Obtain solid product; Described gas phase carbon source is selected from acetylene, ethylene or methane; 3) Washing, suction filtering and drying the above solid to obtain ultra-thin carbon nanosheet powder.