A method for rapidly preparing doped graphene by Joule heating and doped graphene

Abstract

The present invention belongs to the field of preparation of nanomaterials, and particularly relates to a method for rapidly preparing doped graphene by Joule heat and the doped graphene. This method generates Joule heat through pulsed discharge, causing the mixture composed of graphene and a compound containing a doping element to rapidly heat up and cool down, thereby obtaining the doped graphene. The method of the present invention can produce modified graphene doped with different elements at low cost and high efficiency, and can better meet the requirements for adding graphene to different substrates.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial preparation, and particularly relates to a method for rapidly preparing doped graphene by Joule heat and doped graphene. Background Art

[0002] Graphene is a two-dimensional nanomaterial composed of single-layer honeycomb carbon atoms. It is the thinnest, lightest, strongest, and hardest material, with excellent electrical and thermal conductivity, and is known as the "king of new materials". Currently, the large-scale production of graphene powder mainly includes the graphite oxidation-reduction method, the graphite liquid-phase exfoliation method, and the carbon powder flash Joule heating method. These production processes can all obtain graphene powder with a carbon content of more than 99%. In industrial applications, graphene is mainly used as an additive to the substrate. In order to ensure the compatibility between graphene and the substrate, it is often necessary to modify graphene, and element doping of graphene is one of the common means of modification.

[0003] In order to dope elements into graphene, the chemical solution method is generally used. Various highly active chemical reagents are used to oxidize, nitride, fluorinate, and chlorinate graphene, so as to obtain modified graphene doped with different elements. This chemical solution method generally requires the use of a large amount of solution, and the modified graphene also needs to be dried again. The process is complex and consumes a large amount of energy. In recent years, the rapid Joule heating method that directly passes an electric current through the reactants to generate Joule heat has been used to prepare new metastable materials such as high-entropy alloys and single-atom catalysts. This method does not use a solvent. By rapidly heating the mixed raw material powder at high temperature with multiple rapid pulses, the required new nanomaterial can be obtained. The element doping of graphene is similar to the preparation of high-entropy alloys in principle, and there is currently no report on the preparation of element-doped graphene using the rapid Joule heating method. In view of this, there is an urgent need to develop a method based on pulsed rapid Joule heating to prepare modified graphene doped with various elements. Summary of the Invention

[0004] To solve the above technical problems existing in the prior art, the present invention provides a method for rapidly preparing doped graphene by Joule heat and doped graphene.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] The present invention provides a method for rapidly preparing doped graphene by Joule heat, which generates Joule heat through pulsed discharge, so that the mixture composed of graphene and a compound containing a doping element is rapidly heated and cooled, and the doped graphene is obtained.

[0007] Further, the compound containing a doping element is at least one of boric anhydride, boric acid, boron carbide, boron nitride, sodium borohydride, potassium borohydride, borax, sucrose, glucose, sodium carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, alumina powder, silica powder, urea, and melamine.

[0008] Further, the mass content of the compound containing a doping element in the mixture is 0.5% to 50%.

[0009] Further, the current of the pulsed discharge is 20 to 100 amperes.

[0010] Further, the maximum temperature generated by the joule heat is 400 to 2200 °C.

[0011] Further, the single discharge time of the pulsed discharge is 0.2 to 10 seconds.

[0012] Further, the number of times of the pulsed discharge is 1 to 20 times.

[0013] Further, the power supply used for the pulsed discharge is a DC power supply or an AC power supply.

[0014] The present invention also provides a doped graphene prepared by the foregoing method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The rapid joule heat quickly heats the compound containing a doping element added in the graphene mixed powder to a high temperature, causing these compounds to react with graphene, so that other elements enter the graphene lattice to obtain doped graphene. (2) This pulsed discharge heating causes the temperature of the graphene mixed powder method to rise to a high temperature and then rapidly drop, avoiding the volatilization of the doping element compound and reducing the secondary decomposition of the doped graphene into pure graphene, thereby achieving the purpose of effective doping. (3) Since the pulsed rapid joule heat method for graphene doping only uses electricity, the process is simple, there is no obvious pollution, and the cost is very low. Combining the above three aspects, the method for preparing doped graphene by rapid joule heat of the present invention can complete the doping of graphene with low cost and high efficiency, thereby obtaining various modified graphenes, better meeting the requirements of adding graphene to different substrates. Description of the Drawings

[0017] Figure 1 is a schematic diagram of the reaction device for preparing doped graphene by rapid joule heat of the present invention. Detailed Embodiments

[0018] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below.

[0019] AsFigure 1 As shown in the figure, in the present invention, a reaction device for rapidly preparing doped graphene by Joule heat includes a quartz insulating tube 2. The quartz insulating tube 2 contains graphene mixed powder 1. Both ends of the quartz insulating tube 2 are blocked by graphite electrode rods 3 and 4, and the whole is placed in a vacuum chamber 5. The electrode rods 3 and 4 are respectively connected to the positive electrode 7 and the negative electrode 8 of a DC power supply 6 to form a discharge circuit. An ammeter 9 is added to the circuit to measure the discharge current; at the same time, a contact switch 10 is added to control the discharge time through a PLC. In addition, an infrared temperature probe 11 (temperature measurement range: 400 - 3600 °C) is placed in the vacuum chamber to measure the reaction temperature.

[0020] In the experimental methods described in the following embodiments, unless otherwise specified, the power supply uses a constant voltage power supply of 80V 250A, and the discharge time is controlled by controlling the switch through a PLC (programmable logic controller). The raw materials and materials used, unless otherwise specified, can all be obtained from commercial channels.

[0021] Example 1

[0022] Add 0.1 g of boric anhydride powder to 0.9 g of graphene powder, mix and stir to obtain 1 g of graphene and boric anhydride mixture powder. Take 0.1 g of the above mixture powder and put it into a quartz tube with an inner diameter of 8 mm. Block both ends of the quartz tube with graphite electrode rods with a diameter of 8 mm, gently compress and measure the resistance at both ends until the resistance is about 1.0 ohm, then stop compressing. Install the temperature probe, close the vacuum chamber, evacuate, and make the air pressure in the chamber as low as 0.02 atmospheres.

[0023] Turn on the PLC, set the discharge voltage to 60V, set the discharge time to 1 second, with an interval of 3 seconds, repeat the discharge 10 times, and monitor the temperature inside the quartz tube. During the discharge, the mixture powder emits a dazzling white light, the maximum current is 60 amperes, and the highest temperature reaches 1600 °C. After 10 discharges, cool to room temperature, take out the quartz tube, pour out the reacted graphene mixture powder in it, and the color of the powder changes from black to slightly gray.

[0024] Raman spectroscopy is an important means for the structural analysis of graphene. For the Raman spectrum of graphene, its typical peaks appear at 1350 wavenumbers, 1580 wavenumbers, and 2700 wavenumbers. Among them, the 1350 wavenumber peak is called the D peak, and its intensity corresponds to the defect degree of graphene; the 1580 wavenumber peak is called the G peak, and its intensity corresponds to the integrity of graphene; researchers often use ID / IG (or IG / ID) to characterize the defect degree of graphene. If heteroatoms are doped into the lattice of graphene, resulting in an increase in the structural defects of graphene, then the D peak will be significantly enhanced, while the G peak remains basically unchanged. Therefore, in the structural analysis of graphene, the ratio ID / IG of the intensities of the D peak and the G peak can be used as a semi-quantitative standard for the doping degree.

[0025] The products after the reaction of graphene raw materials and mixture powders were respectively subjected to laser Raman spectroscopy detection. The ID / IG of the graphene raw materials was 0.12, proving that the graphene raw materials had fewer structural defects and were graphene powders with relatively good quality. The intensity ratio ID / IG of the slightly gray product obtained by the reaction was 0.74, which was significantly greater than the ID / IG of the graphene raw materials. Therefore, laser Raman spectroscopy indicated that boron and oxygen elements had been effectively doped into the lattice of graphene, and the rapid Joule heating method completed the modification of the graphene raw materials.

[0026] Example 2

[0027] 0.1 grams of boric acid, boron carbide, boron nitride, sodium borohydride, potassium borohydride, borax, sucrose, glucose, sodium carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, alumina powder, silica powder, urea, and melamine powder were respectively taken and added to 0.9 grams of graphene powder, and the mixture was stirred to obtain 15 kinds of graphene mixture powders. In these graphene mixture powders, the mass content of graphene was 90%, and the mass content of the doping element compound was 10%. Using the process method of Example 1, the rapid Joule heating method was used to pulse-discharge heat the above graphene mixture powders to obtain 15 corresponding reaction products.

[0028] These reaction products were subjected to laser Raman spectroscopy detection, and their ID / IG was calculated to be 0.45, 0.38, 0.56, 0.37, 0.39, 0.52, 0.60, 0.61, 0.59, 0.74, 0.64, 0.45, 0.48, 0.55, 0.49 respectively. These ratios were all significantly greater than the ID / IG (0.12) of the graphene raw materials, indicating that these products were all doped graphene, and the graphene had been modified by boron and oxygen doping, boron doping, boron and nitrogen doping, boron doping, boron doping, boron and oxygen doping, oxygen doping, oxygen doping, oxygen doping, fluorine doping, fluorine doping, aluminum and oxygen doping, silicon and oxygen doping, nitrogen doping, and nitrogen doping respectively.

[0029] Example 3

[0030] 0.002 g, 0.005 g, 0.01 g, 0.05 g, 0.1 g, 0.3 g, 0.5 g, and 0.6 g of sucrose were respectively taken and mixed with 0.998 g, 0.995 g, 0.99 g, 0.95 g, 0.9 g, 0.7 g, 0.5 g, and 0.4 g of graphene to obtain graphene mixture powders containing 0.2%, 0.5%, 1%, 5%, 10%, 30%, 50%, and 60% of doped compounds. Using the process method of Example 1, the above graphene mixture powders were pulse-discharged and heated by the rapid Joule heating method to obtain 8 corresponding reaction products.

[0031] These reaction products were detected by laser Raman spectroscopy, and their ID / IG values were calculated to be 0.15, 0.24, 0.33, 0.53, 0.74, 0.80, 0.82, and 0.81 respectively. When the content of the doped compound was 0.2%, the ID / IG only increased to 0.15, which was close to 0.12 of the graphene raw material, and the doping effect was not obvious. When the content of the doped compound was from 0.5% to 50%, the ID / IG was significantly greater than 0.12 of pure graphene, indicating that a large amount of doped elements entered the lattice of graphene and effectively modified the graphene. When the content of the doped compound was 60%, the ID / IG did not increase significantly, indicating that there was too much doped compound. Therefore, through comprehensive analysis, it can be known that the optimal mass content of the doped compound in the graphene mixture is from 0.5% to 50%.

[0032] Example 4

[0033] 0.1 g of boric anhydride powder was added to 0.9 g of graphene powder, and the mixture was stirred to obtain a graphene and boric anhydride mixture powder, in which the graphene content was 90% and the content of the doped element compound was 10%. Using the process method of Example 1, the current was set at 10 A, 20 A, 40 A, 100 A, and 120 A for 10 pulse discharges, and the highest reaction temperatures reached about 200°C, 400°C, 1200°C, 2200°C, and 2600°C respectively. The above graphene mixture powders were pulse-discharged and heated by the rapid Joule heating method to obtain 5 corresponding reaction products.

[0034] The laser Raman spectroscopy was used to detect these reaction products, and their ID / IG values were calculated to be 0.13, 0.22, 0.75, 0.85, and 0.65 respectively. When the discharge current was 10 amperes, the temperature was relatively low, only about 200 °C, and the ID / IG was only 0.13, which was basically the same as that of the graphene raw material. Therefore, the doping compound hardly reacted with graphene. When the current was relatively large, from 20 amperes to 100 amperes, the temperature was relatively high, reaching 400 to 2200 °C, and the doping compound underwent a chemical reaction with graphene, and the ID / IG was significantly greater than the ID / IG value of the graphene raw material. When the current was 120 amperes, the current was relatively large, the temperature reached about 2600 °C, which had reached the graphitization temperature of the carbon material, and the doped graphene would be graphitized again, and the ID / IG became smaller instead. Therefore, through comprehensive analysis, it can be known that the optimal current for rapid Joule heat discharge is 20 to 100 amperes, and the optimal heating temperature is 400 to 2200 °C.

[0035] Example 5

[0036] 0.1 g of boric anhydride powder was added to 0.9 g of graphene powder, and the mixture was stirred to obtain a graphene and boric anhydride mixture powder, in which the graphene content was 90% and the content of the doping element compound was 10%. Using the process method of Example 1, the single discharge time of the pulsed discharge was set to 0.1 s, 0.2 s, 1 s, 10 s, and 15 s respectively, the intermittent time was 3 s, and the pulsed discharge was carried out 10 times. The above graphene mixture powder was heated by the rapid Joule heat method to obtain 5 corresponding reaction products.

[0037] The laser Raman spectroscopy was used to detect these reaction products, and their ID / IG values were calculated to be 0.15, 0.38, 0.74, 0.85, and 0.65 respectively. When the single discharge time was 0.1 s, the heating time was too short, the temperature was relatively low, only 230 °C, and the ID / IG was only 0.15, which was basically the same as that of the graphene raw material. Therefore, the doping compound hardly reacted with graphene. When the discharge time was relatively long, from 0.2 s to 10 s, the temperature was relatively high, and the doping compound underwent a chemical reaction with graphene, and the ID / IG was significantly greater than the ID / IG value of the graphene raw material. When the single discharge time was too long, the heating time was too long, and many doping compounds were evaporated, and the ID / IG became smaller instead. Therefore, through comprehensive analysis, it can be known that the optimal single discharge time for rapid Joule heat pulsed discharge is 0.2 to 10 s.

[0038] Example 6

[0039] Add 0.1 g of boric anhydride powder to 0.9 g of graphene powder, mix and stir to obtain a graphene and boric anhydride mixture powder, where the graphene content is 90% and the content of the doped element compound is 10%. Using the process method of Example 1, set the discharge current to 60 amperes, the single discharge time to 1 second, and the intermittent time to 3 seconds. Perform 1, 5, 10, 20, and 30 discharges respectively, and use the rapid Joule heating method to pulse-discharge heat the above graphene mixture powder to obtain 5 corresponding reaction products.

[0040] Perform laser Raman spectroscopy detection on these reaction products, and calculate their ID / IG values, which are 0.44, 0.57, 0.74, 0.85, and 0.84 respectively. When the number of discharges is from 1 to 20 times, the ID / IG of the product is significantly greater than that of the graphene raw material, indicating that the doped compound has undergone a chemical reaction with graphene. The ID / IG of the products with 30 and 20 pulse discharges is basically the same, but the time is extended by 50%, reducing the production efficiency. Therefore, through comprehensive analysis, it can be known that the optimal number of rapid Joule heating pulse discharges is from 1 to 20 times.

[0041] Example 7

[0042] Add 0.1 g of boric anhydride powder to 0.9 g of graphene powder, mix and stir to obtain a graphene and boric anhydride mixture powder, where the graphene content is 90% and the content of the doped element compound is 10%. Using the process method of Example 1, change the power supply to a 60V AC power supply for rapid Joule heating reaction, and the above graphene compound powder reacts to obtain the corresponding reaction product.

[0043] Perform Raman spectroscopy detection on the reaction product, and calculate its ID / IG value, which is 0.69, basically the same as the ratio of 0.74 of the doped graphene obtained using a DC power supply. Therefore, for the rapid Joule heating reaction to prepare doped graphene from graphene mixture powder, either a DC power supply or an AC power supply can be used.

[0044] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing doped graphene by rapid Joule heating, characterized in that: Joule heat is generated by pulsed discharge to rapidly heat up and cool down a mixture composed of graphene and a compound containing a doping element, thereby obtaining the doped graphene; The maximum temperature generated by the Joule heat is 400 to 1600 °C; The single discharge time of the pulsed discharge is 0.2 to 10 seconds; The number of times of the pulsed discharge is 1 to 20 times.

2. The method for rapidly preparing doped graphene by Joule heat according to claim 1, wherein, The compound containing a doping element is at least one of sucrose, glucose, sodium carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, alumina powder, silica powder, urea, and melamine.

3. The method for preparing doped graphene by rapid Joule heating according to claim 1, wherein, The mass content of the compound containing a doping element in the mixture is 0.5% to 50%.

4. A method for rapidly preparing doped graphene by Joule heating according to claim 1, characterized in that, The current of the pulsed discharge is 20 to 100 amperes.

5. A method for rapidly preparing doped graphene by Joule heating according to claim 1, characterized in that, The power supply used for the pulsed discharge is a DC power supply or an AC power supply.

6. A doped graphene prepared by the method according to any one of claims 1 to 5.

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