CN107311157A - One kind is with CO2For the method for carbon source low temperature preparation graphene - Google Patents

Abstract

The invention provides one kind with CO₂For the method for carbon source low temperature preparation graphene, this method is with CO₂As gaseous carbon source, in Ar and H₂Under atmosphere, using plasma enhancing chemical vapour deposition technique grows graphene in substrate；In the plasma enhanced chemical vapor deposition method, reaction temperature is 300 500 DEG C.The present invention provide with CO₂For the method for carbon source low temperature preparation graphene, the CO of safety non-toxic is employed₂Graphene is prepared as carbon source, and under the conditions of relatively low temperature, this industrialized production to graphene opens new approach.

Description

A method for preparing graphene at low temperature with CO2 as carbon source

technical field

The invention belongs to the field of graphene preparation, in particular to a method for preparing graphene at low temperature using _CO2 as a carbon source.

Background technique

Graphene is a new type of carbon material with a single-layer two-dimensional honeycomb lattice structure closely packed with carbon atoms. The basic unit of three-dimensional graphite). Graphene's unique two-dimensional nanocrystal structure makes it have the advantages of high electron transfer rate, excellent electrical conductivity, high thermal conductivity, excellent mechanical properties, and good chemical stability and light transmission. It is expected to be used in nanoelectronic devices, transparent Conductive films, composite materials, catalytic materials, field emission materials, solar cell electrodes, photoelectric converters and other fields have been widely used. For this, graphene won the 2010 Nobel Prize in Physics just 6 years after its discovery in 2004.

At present, there are many methods for preparing graphene, such as mechanical exfoliation, chemical exfoliation, SiC epitaxial growth, chemical vapor deposition (CVD) and so on. Among them, although the graphene obtained by the mechanical exfoliation method is of high quality, the output is extremely low, the efficiency is low, and the randomness is large, which is only suitable for laboratory research. Due to the existence of a strong oxidation process in the chemical exfoliation method, the prepared graphene has many defects, poor quality and small size (micron order). The SiC epitaxial growth method has low efficiency, poor controllability, high cost and the prepared graphene is difficult to transfer. In contrast, CVD is one of the most promising methods for preparing graphene. The CVD method is to heat a carbon source such as methane to a specific temperature in a vacuum container to decompose it, and then form graphite on transition metal foils such as Ni and Cu. film technology. However, the commonly used carbon sources for graphene preparation by CVD are flammable and explosive gas sources such as methane, ethylene, and acetylene, which not only bring unsafe factors to the industrial production of graphene, but also cause air pollution due to exhaust gas, which cannot be achieved. Green and environmental protection production demand.

Moreover, at present, when graphene is prepared by CVD method, the preparation temperature is as high as about 1000°C, and the preparation time is generally about 30 minutes, which greatly limits the practical application of graphene materials in microelectronic devices. Therefore, it is necessary to carry out in-depth research in this area, and the breakthrough in this direction is of great significance to the practical application and industrial production of graphene.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a method for preparing graphene at low temperature with _CO2 as carbon source.

In order to achieve the above object, the present invention provides a method for preparing graphene at low temperature with _CO2 as a carbon source, the method is to use _CO2 as a gaseous carbon source, under Ar and _H2 atmosphere, using plasma enhanced chemical vapor deposition method to grow graphene on the substrate; in the plasma enhanced chemical vapor deposition method, the reaction temperature is 300-500°C.

In the method for preparing graphene at low temperature using _CO2 as a carbon source provided by the present invention, safe and non-toxic _CO2 is used as a carbon source, and graphene needs to be prepared at a lower temperature (300-500° C.). In the prior art, CO ₂ is a carbon source that is more difficult to crack than methane. Therefore, CO ₂ is generally not considered when preparing graphene by CVD, because it will mean that a higher reaction temperature is required, and high temperature environment Not only does it mean increased operational difficulty and cost, but more importantly, graphene is more prone to defects at high temperatures. Therefore, no technology has been found in the prior art to use _CO2 as a carbon source to prepare graphene by CVD. In addition, there is also a technology (CN103183344A) using methane as a carbon source in the prior art to prepare graphene by PECVD (plasma enhanced chemical vapor deposition). Due to the auxiliary effect of plasma, the reaction temperature for preparing graphene However, according to the conventional knowledge of those skilled in the art, if _CO2 is used as the carbon source and PECVD is used to prepare graphene, in order to crack _CO2 , a higher reaction temperature is necessarily required. The present invention also is to try towards the direction of raising reaction temperature in the initial stage of exploration, but all fails; However, after repeated failures, it is accidentally found that under PECVD conditions, it is at a lower temperature (300° C.-500° C. °C) was able to utilize refractory _CO2 to prepare graphene with good properties, which greatly exceeded the original expectations. Moreover, studies have found that graphene is difficult to obtain when the temperature exceeds 500°C, and it is difficult to obtain graphene when the temperature is lower than 300°C due to the difficulty in cracking. We speculate after analysis that it may be due to the fact that 300°C-500°C is the temperature at which _CO2 reacts easily with reducing gas _H2 . In addition, a very important point of the present invention is the use of safe and non-toxic CO ₂ , which is safer and more environmentally friendly than alkanes in the prior art due to its low cost and greenhouse gas. Therefore, the present invention provides a very realistic Significance and application value of the method for preparing graphene.

In the method for preparing graphene at low temperature using _CO2 as a carbon source, after the substrate on which graphene is grown is obtained, conventional operations in the art can be used to separate the graphene from the substrate to obtain graphene.

In the above-mentioned method for preparing graphene at low temperature with _CO2 as a carbon source, the plasma-enhanced chemical vapor deposition method can use conventional PECVD equipment, or can use the equipment formed after the CVD equipment is equipped with a radio frequency transmitter, as long as it can It is sufficient to meet the conditions required for the experiment. In the specific experiment, there is no special requirement on the operation, and it can be carried out according to the routine procedures in the art.

In the above method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, the reaction temperature is 350-450°C; more preferably 400°C.

In the above-mentioned method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, in the plasma-enhanced chemical vapor deposition method, the radio frequency emission power is 50-200W, more preferably 200W.

In the above-mentioned method for preparing graphene at low temperature with _CO as a carbon source, preferably, in the plasma-enhanced chemical vapor deposition method, the volume flow ratio of H and _CO during the deposition reaction is 5-20: ₁ ; Preferably 10-20:1; more preferably 10:1. The volume flow rate of the carrier gas Ar can be adjusted according to conventional operations in the art. In a preferred embodiment provided by the present invention, the gas volume flow ratio during the deposition reaction is Ar:H ₂ :CO ₂ =100:100:10.

In the method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, in the plasma-enhanced chemical vapor deposition method, the reaction time is 60s-10min. The reaction time refers to the time during which carbon dioxide is introduced and plasma (plasma) acts on it.

In the above-mentioned method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, in the plasma-enhanced chemical vapor deposition method, the material of the substrate is Cu, Ni, Co or Pt.

In the method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, in the plasma-enhanced chemical vapor deposition method, the reaction pressure is 0-1000Pa, preferably 100-200Pa. The reaction pressure is mainly set according to the working pressure of the equipment.

In the above-mentioned method for preparing graphene at a low temperature with _CO as a carbon source, preferably, the plasma-enhanced chemical vapor deposition method comprises the following steps:

(1) Under vacuum conditions, place the cleaned substrate in a plasma-enhanced chemical vapor deposition reaction device;

(2) under the Ar and _H2 atmosphere, the reaction chamber is heated to the reaction temperature, and then _CO2 is introduced, and the feed amount of Ar, _H2 and _CO2 is adjusted to the ratio required for the reaction;

(3) Turn on the plasma radio frequency transmitter, and the deposition reaction begins;

(4) After reaching the reaction time, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained;

(5) Etching the substrate deposited with graphene to obtain graphene.

In the above-mentioned method for preparing graphene at low temperature using _CO2 as a carbon source, preferably, in step (1), the substrate is copper foil, aluminum foil, or the like. The substrate can be cleaned according to conventional methods, for example, the substrate is sequentially soaked in acetic acid, water and ethanol for cleaning.

In a preferred embodiment provided by the invention, _CO2 is the method for preparing graphene at a low temperature of carbon source comprising the following steps:

(1) Before the reaction, the substrate (copper foil, nickel foil, etc.) is soaked and cleaned in acetic acid, water and ethanol in sequence;

(2) Under vacuum conditions, place the cleaned substrate in plasma-enhanced chemical vapor deposition reaction equipment (also can be the equipment formed by CVD with a radio frequency transmitter), and adjust the temperature control program of the equipment;

(3) Operating the equipment under the atmosphere of Ar and H ₂ starts to heat up. After the temperature of the reaction chamber rises to 300-500°C (preferably 350-450°C, more preferably 400°C), start to introduce CO ₂ , and adjust Ar, The feed rate of _H2 and _CO2 is such that the volume flow ratio of _H2 to _CO2 is 5-20:1 (preferably 10-20:1, more preferably 10:1);

(4) Turn on the plasma radio frequency transmitter, and the deposition reaction begins;

(5) After reacting for 60s-10min, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained;

(6) Etching the substrate deposited with graphene to obtain graphene.

The method provided by the invention takes _CO2 as carbon source low temperature preparation graphene, has the following advantages:

1. The carbon source used in the method provided by the present invention is CO ₂ , which is clean, safe, non-toxic and environmentally friendly;

2. The method provided by the present invention uses low-temperature growth technology to save costs;

3. The process flow of the method provided by the present invention is simple, does not require a catalyst, and grows directly through carbon dioxide;

4. The graphene prepared by the method provided by the present invention has good film-forming properties and good continuity, and large-area graphene can be prepared.

Description of drawings

Fig. 1 is the schematic diagram of the equipment used in embodiment 1-3;

Fig. 2 is the low magnification transmission electron microscope figure of the graphene product that embodiment 1 makes;

Fig. 3 is the high-magnification transmission electron microscope figure of the graphene product that embodiment 1 makes;

Fig. 4 is the Raman spectrogram of the graphene product that embodiment 1 makes;

Fig. 5 is the Raman spectrogram of the graphene product that embodiment 2 makes.

detailed description

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Example 1

Present embodiment provides a kind of method (using equipment is shown in Fig. 1) that is carbon source low temperature preparation graphene with _CO , this comprises the following steps:

(1) Before the reaction, the metal base nickel foil is sequentially placed in acetic acid, water and ethanol to soak and clean;

(2) Under vacuum conditions, place the cleaned substrate in plasma-enhanced chemical vapor deposition reaction equipment, and adjust the temperature control program of the equipment;

(3) Operate the equipment under the atmosphere of Ar and H ₂ and start to heat up. After the temperature of the reaction chamber rises to 400°C, start to introduce CO ₂ , and adjust the amount of Ar, H ₂ and CO ₂ to Ar:H ₂ :CO ₂ = 100:200:10 (sccm);

(4) Turn on the plasma radio frequency transmitter (the transmission power is 200W), and the deposition reaction starts (the working pressure of the equipment is 100Pa);

(5) After reacting for 10 minutes, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained;

(6) Etching the substrate deposited with graphene to obtain graphene.

Graphene is carried out corresponding test, and the transmission electron microscope figure of this graphene is shown in Fig. 2 and Fig. 3, and the Raman spectrum test result of this graphene is shown in Fig. 4 (from Fig. 4, graphene D, G and 2D can be seen The characteristic position of the peak).

From the above test results, it can be seen that the graphene prepared in this embodiment has good continuity and a large area, which can reach centimeter level.

Example 2

Present embodiment provides a kind of method (using equipment is shown in Fig. 1) that is carbon source low temperature preparation graphene with _CO , this comprises the following steps:

(1) Before the reaction, the base copper foil is soaked and cleaned in acetic acid, water and ethanol in sequence;

(2) Under vacuum conditions, place the cleaned substrate in plasma-enhanced chemical vapor deposition reaction equipment, and adjust the temperature control program of the equipment;

(3) Operate the equipment under the atmosphere of Ar and H ₂ and start to heat up. After the temperature of the reaction chamber rises to 300°C, start to introduce CO ₂ , and adjust the amount of Ar, H ₂ and CO ₂ to Ar:H ₂ :CO ₂ = 100:200:10 (sccm);

(4) Turn on the plasma radio frequency transmitter (transmission power is 100W), and the deposition reaction begins;

(5) After reacting for 10 minutes, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained;

(6) Etching the substrate deposited with graphene to obtain graphene.

Graphene is carried out corresponding test (the Raman spectrum test result of graphene sees Fig. 5), test result shows, the graphene size that makes in this example is big, but defect is more than in embodiment 1, and structural slightly worse.

Example 3

Present embodiment provides a kind of method (using equipment is shown in Fig. 1) that is carbon source low temperature preparation graphene with _CO , this comprises the following steps:

(1) Before the reaction, the base nickel foil is sequentially placed in acetic acid, water and ethanol to soak and clean;

(2) Under vacuum conditions, place the cleaned substrate in plasma-enhanced chemical vapor deposition reaction equipment, and adjust the temperature control program of the equipment;

(3) Operate the equipment under the atmosphere of Ar and H ₂ and start to heat up. After the temperature of the reaction chamber rises to 500°C, start to introduce CO ₂ , and adjust the amount of Ar, H ₂ and CO ₂ to Ar:H ₂ :CO ₂ = 100:150:10 (sccm);

(4) Turn on the plasma radio frequency transmitter (transmission power is 150W), and the deposition reaction begins;

(5) After reacting for 60 seconds, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained;

(6) Etching the substrate deposited with graphene to obtain graphene.

Corresponding tests are carried out on graphene, and the test results show that the graphene prepared in this example has a thinner thickness, smaller size and fewer defects.

Claims (10)

1. A method for preparing graphene at a low temperature with _CO2 as a carbon source, wherein the method is to use _CO2 as a gaseous carbon source, and under Ar and _H2 atmosphere, the plasma-enhanced chemical vapor deposition method is used to grow on the substrate Graphene; In the plasma enhanced chemical vapor deposition method, the reaction temperature is 300-500°C. 2. the method for preparing graphene at low temperature with _CO2 as a carbon source according to claim 1, wherein the reaction temperature is 350-450°C. 3. the method for preparing graphene at low temperature with _CO2 as a carbon source according to claim 2, wherein the reaction temperature is 400°C. 4. use CO according to claim ₁ as the method for low-temperature preparation of graphene as a carbon source, wherein, in the plasma-enhanced chemical vapor deposition method, the radio frequency emission power is 50-200W, preferably 200W. 5. according to any one of claim 1-4 with CO ₂ as the method for carbon source low temperature preparation of graphene, wherein, in the plasma enhanced chemical vapor deposition method, during the deposition reaction H ₂ and CO ₂ The volume flow ratio is 5-20:1. 6. use CO according to claim ₅ be the method for carbon source low temperature preparation graphene, wherein, in described plasma-enhanced chemical vapor deposition method, H during deposition reaction and _{CO The} volume flow ratio is 10 - 20:1, preferably 10:1. 7. the method for preparing graphene at low temperature with _CO2 as carbon source according to claim 1, wherein, in the plasma-enhanced chemical vapor deposition method, the reaction time is 60s-10min. 8. the method for preparing graphene at low temperature with _CO2 as a carbon source according to claim 1, wherein, in the plasma-enhanced chemical vapor deposition method, the material of the substrate is Cu, Ni, Co or Pt. 9. The method for preparing graphene at low temperature with _CO as a carbon source according to claim 1, wherein, in the plasma-enhanced chemical vapor deposition method, the reaction pressure is 0-1000Pa, preferably 100-200Pa. 10. according to any one of claim 1-9 with _CO Be the method for carbon source low temperature preparation graphene, wherein, described plasma-enhanced chemical vapor deposition method comprises the following steps: (1) Under vacuum conditions, place the cleaned substrate in a plasma-enhanced chemical vapor deposition reaction device; (2) under the atmosphere of Ar and _H2 , the reaction chamber of the equipment is heated to the reaction temperature, then _CO2 is introduced, and the feed amount of Ar, _H2 and _CO2 is adjusted to the ratio required for the reaction; (3) Turn on the plasma radio frequency transmitter, and the deposition reaction begins; (4) After reaching the reaction time, turn off the plasma radio frequency transmitter, stop feeding CO ₂ , and open the reaction chamber to lower the temperature. After cooling to room temperature, a substrate deposited with graphene is obtained; (5) Etching the substrate deposited with graphene to obtain graphene.