Liquid catalysis-based graphene and preparation method thereof

Abstract

The application relates to the technical field of carbon materials, in particular to a liquid catalysis-based graphene and a preparation method thereof. The method comprises the following steps: providing a mixture of a metal catalyst and a preset glass material, heating the mixture to a preset temperature in an inert atmosphere environment, so that the metal catalyst and the preset glass material are both in a molten state, a molten catalysis mixture is obtained, and the temperature of the molten catalysis mixture is ensured to be greater than or equal to a preset growth temperature; a carbon-containing gas is introduced from the bottom of the molten catalysis mixture, so as to form bubbles in the molten catalysis mixture; in the process of rising of the bubbles, graphene is generated on the surface of the bubbles based on the catalysis of the molten catalysis mixture; and the graphene rising above the molten catalysis mixture is collected, so that graphene powder is obtained. The application can significantly improve the crystallization quality and conductivity of the graphene powder, and cooperatively improve the product yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon materials, in particular to a graphene based on liquid catalysis and a preparation method thereof. BACKGROUND

[0002] Chemical vapor deposition is the main method for preparing high-quality graphene and studying the growth mechanism of graphene at present. However, due to the limitations of substrate area and product recovery, the unit time yield and yield of this method are too low, and the application is poor. In order to realize the mass production of graphene, the existing technology uses a stripping method for graphene production. However, whether chemical stripping or physical stripping, there are too many product defects, which cannot meet the mass production and quality requirements of graphene. Therefore, an improved preparation method is needed to improve the yield while ensuring the quality of graphene products. SUMMARY

[0003] In view of the above problems of the prior art, the present application provides a graphene based on liquid catalysis and a preparation method thereof. The specific technical solutions are as follows:

[0004] In one aspect, the present application provides a preparation method of graphene powder, which comprises:

[0005] S11: providing a mixture of a metal catalyst and a predetermined glass material, and heating to a predetermined temperature under an inert atmosphere to make the metal catalyst and the predetermined glass material reach a molten state, to obtain a molten catalytic mixture, and to ensure that the temperature of the molten catalytic mixture is greater than or equal to a predetermined growth temperature;

[0006] S12: introducing a carbon-containing gas from the bottom of the molten catalytic mixture to form bubbles in the molten catalytic mixture. In the process of rising of the bubbles, based on the catalytic action of the molten catalytic mixture, graphene is generated on the surface of the bubbles;

[0007] S13: collecting graphene rising above the molten catalytic mixture along with the bubbles to obtain graphene powder.

[0008] Specifically, the predetermined glass material comprises Na2SiO3, and at least one of SiO2 and CaSiO3, and the mass fraction of Na2SiO3 in the predetermined glass material is 47% to 56%.

[0009] Specifically, the mass ratio between the metal catalyst and the predetermined glass material is (97% to 99%) : (1% to 3%).

[0010] Specifically, the viscosity of the molten predetermined glass material is (10 to 100) Pa.S; the viscosity of the molten catalytic mixture is 10.3 x 10 -3 32.1 x 10-3 Pa.s.

[0011] Specifically, the carbon-containing gas is introduced from the bottom of the molten catalytic mixture through a gas pipe, and the distance between the gas outlet of the gas pipe and the liquid surface of the molten catalytic mixture is 30-50 cm.

[0012] Specifically, the carbon-containing gas comprises inert gas and preset carbon source gas, and the volume ratio between the inert gas and the preset carbon source gas is 100%: (3%-20%).

[0013] Specifically, the preset growth temperature is 1150-1350°C.

[0014] Specifically, the preset carbon source gas in the carbon-containing gas comprises at least one of methane, ethane, propane, butane, ethylene, propylene, natural gas, liquefied gas, acetylene, propyne, coal bed methane, and biogas.

[0015] Specifically, the metal catalyst comprises copper, an alloy composed of one or more of copper and lead, germanium, nickel, iron, cobalt, tin, chromium, bismuth, silver, gallium, and palladium.

[0016] In another aspect, the application provides a liquid catalysis-based graphene, which is prepared based on the above preparation method.

[0017] In another aspect, the application provides a liquid catalysis-based graphene, which is prepared based on the above preparation method.

[0018] Based on the above technical solution, the application has the following beneficial effects:

[0019] The application uses molten metal and preset glass material as the catalytic matrix, introduces carbon-containing gas into the catalytic matrix, forms graphene in the bubbles under the action of high temperature and catalysis of the molten mixture, and then the graphene rises above the liquid surface for collection. The preset glass material is used to increase the viscosity of the catalytic matrix, slow down the rising speed of the bubbles, prolong the residence time of the bubbles in the matrix, ensure more complete cracking of the gaseous carbon source, and improve the conversion rate, thereby improving the yield of graphene, prolonging the growth time, reducing the defects of the graphene film, and improving the crystalline quality of the product. In addition, by increasing the viscosity of the matrix, the stability of the bubbles can be improved, the contact between the gaseous carbon source and the catalyst can be ensured, and the yield can be further improved. Furthermore, the scheme is simple in operation, controllable in process, easy to expand, and suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0021] Figure 1 The flowchart of the liquid catalysis-based graphene powder preparation method provided by the embodiments of the present application;

[0022] Figure 2 The structure diagram of the crucible and the gas pipe in the liquid catalysis-based graphene powder growth device provided by the embodiments of the present application;

[0023] Figure 3 The Raman spectrum of the graphene powder of Example 1 of the present application;

[0024] Figure 4 The SEM image of the graphene powder of Example 1 of the present application;

[0025] Figure 5 The TEM image of the graphene powder of Example 1 of the present application;

[0026] Figure 6 The Raman spectrum of the graphene powder of Comparative Example 1 of the present application;

[0027] Figure 7 The Raman spectrum of the graphene powder of Comparative Example 2 of the present application

[0028] Figure 8 The TEM image of the graphene powder of Comparative Example 3 of the present application;

[0029] Figure 9 The TEM image of the graphene powder of Comparative Example 4 of the present application;

[0030] Figure 10 The Raman spectrum of the graphene powder of Comparative Example 3 of the present application;

[0031] Figure 11 The Raman spectrum of the graphene powder of Comparative Example 4 of the present application;

[0032] The drawings show that: 10-melted catalysis mixture, 20-gas pipe, 21-gas outlet. DETAILED DESCRIPTION

[0033] With reference to the drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work shall fall within the scope of the present application.

[0034] For the following defined terms, these definitions shall be applied even if these terms are used in the description of the claims or in the specification. All numbers indicating numerical values are defined as being modified in all instances by the term "about," unless indicated otherwise in the specification or claims. The term "about" generally means a range of values that one of ordinary skill in the art would consider as a substantially equivalent value to produce the same property, function, result, etc. A numerical range expressed by a low value and a high value is defined to include all numerical values falling within the range, and all sub-ranges included within the range.

[0035] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above drawings are used to distinguish similar objects and are not necessarily used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged, where appropriate, so that the embodiments of the present application described herein can be carried out in other than the order illustrated or described herein. Furthermore, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion.

[0036] The liquid catalysis based graphene preparation method provided by the embodiments of the present application is described below in combination with the drawings. Please refer to Figure 1 , Figure 1 is a flowchart of the preparation method. The present specification provides method operation steps such as embodiments or flowcharts, but more or less operation steps can be included based on conventional or non-creative work. The order of steps listed in the embodiments is only one of the many execution orders of the steps, and does not represent the only execution order. In actual preparation method execution, the method can be executed in sequence or in parallel as shown in the embodiments or drawings. The method includes:

[0037] S11: Provide a mixture of a metal catalyst and a predetermined glass material, and heat it to a predetermined temperature in an inert atmosphere environment, so that the metal catalyst and the predetermined glass material both reach a molten state, to obtain a molten catalytic mixture 10, and ensure that the temperature of the molten catalytic mixture 10 is greater than or equal to a predetermined growth temperature.

[0038] In the embodiments of the present application, the metal catalyst and the preset glass material can be cleaned and then placed in a crucible to be mixed uniformly. The crucible is placed in a heating furnace, the heating furnace body is sealed, the pressure in the furnace cavity is extracted to a certain pressure, such as 20 Pa or less, and then inert gas is introduced to normal pressure. The above gas exchange operation is repeatedly performed, such as repeated vacuum extraction-inert gas filling 2 times, so that the air in the furnace cavity is completely replaced. Then the exhaust valve of the heating furnace is opened, inert gas is continuously introduced, the crucible is heated by the heating coil, the metal catalyst and the preset glass material are heated to a molten state, and the temperature of the molten catalyst mixture 10 is ensured to be above the preset growth temperature.

[0039] It can be understood that, in the case that the melting point of the metal catalyst or the preset glass material is higher than the above-mentioned preset growth temperature, after the formation of the molten catalyst mixture 10, the temperature of the mixture does not need to be raised again to ensure that it is in a molten state; if the melting points of the metal catalyst and the preset glass material are both lower than the preset growth temperature, after the molten catalyst mixture 10 is heated, the molten catalyst mixture 10 is heated to a temperature reaching the preset growth temperature.

[0040] In some embodiments, the preset growth temperature is 1150-1350°C.

[0041] In some embodiments, the metal catalyst includes copper, an alloy of copper and lead, germanium, nickel, iron, cobalt, tin, chromium, bismuth, silver, gallium, palladium, or one or more of the above.

[0042] In some embodiments, before the gas is introduced, the molten catalyst mixture 10 can be stirred to improve the uniformity of the mixture. After the mixture is uniform, it is left to stand, and then the gas introduction process is performed.

[0043] S12: Introduce the carbon-containing gas from the bottom of the molten catalyst mixture 10 to form bubbles in the molten catalyst mixture 10. In the process of rising of the bubbles, based on the catalytic action of the molten catalyst mixture 10, graphene is generated on the surface of the bubbles.

[0044] S13: Collect the graphene that rises above the molten catalyst mixture 10 with the bubbles to obtain a graphene powder.

[0045] In the embodiments of the present application, after the crucible containing the molten catalytic mixture 10 is covered, the carbon-containing gas is introduced into the molten catalytic mixture 10 through the air pipe 20 to form bubbles in the lower part of the molten catalytic mixture 10, and the bubbles rise based on the buoyancy. During the rising process, due to the high temperature heating of the molten catalytic mixture 10 and the catalytic action of the metal catalyst therein, the carbon source gas in the bubbles undergoes a cracking reaction to generate graphene and tail gas. The light graphene adheres to the surface of the bubbles, and rises to the liquid surface of the molten catalytic mixture 10 with the bubbles, breaks and obtains graphene above the molten catalytic mixture 10, and the tail gas is discharged upward.

[0046] In some embodiments, the graphene can be blown into a powder collecting device by using air flow to directly obtain graphene powder. In other embodiments, the graphene is blown into a container containing a washing agent by using air flow to remove impurities, and then filtered, washed, and dried to obtain pure graphene powder. In one embodiment, the washing agent can be an HNO3 / HCl / HF aqueous solution, wherein the molar concentration ratio of HNO3, HCl and HF can be 4:2:1. In this way, continuous production and purification of graphene are realized, metal powder and glass powder particles carried on the graphene powder are removed by the acidic washing agent, the purity of the graphene is improved, and the application performance of the graphene is optimized.

[0047] In the embodiments of the present application, the viscosity of the molten preset glass material is higher than the viscosity of the molten metal catalyst. In this way, the viscosity of the molten mixture is increased by the preset glass material to improve the stability of the bubbles and regulate the rising speed of the bubbles, and balance the length of the cracking reaction in the bubbles, the thickness of the graphene and the quality demand of the graphene.

[0048] In some embodiments, the preset glass material includes Na2SiO3, and at least one of SiO2 and CaSiO3, and the mass fraction of Na2SiO3 in the preset glass material is 47% to 56%. In one embodiment, the preset glass material includes Na2SiO3, CaSiO3 and SiO2. In this way, by using the glass material with the above-mentioned SiO2 mass fraction range, ordinary glass or tempered glass can be used as the above-mentioned preset glass material, thereby effectively utilizing waste glass resources, and at the same time realizing material recycling and utilization, obtaining a molten mixture with ideal viscosity, thereby improving the stability of the carbon-containing bubbles, controlling the rising speed of the carbon-containing bubbles to an ideal range, ensuring the reaction length of the graphene generation process, thereby ensuring sufficient gas cracking, improving the graphene yield, and reducing product defects.

[0049] In some embodiments, the viscosity of the molten preset glass material is (10-100) Pa.s, and the viscosity of the molten catalytic mixture 10 is 10.3x10 -3 ~ 32.1x10 -3Pa.s. Specifically, the upper limit of the viscosity of the preset glass material can be 100 Pa.s, 95 Pa.s, 90 Pa.s, 85 Pa.s, 80 Pa.s, etc., and the lower limit of the viscosity of the preset glass material can be 10 Pa.s, 15 Pa.s, 20 Pa.s, 25 Pa.s, 30 Pa.s, etc.; specifically, the upper limit of the viscosity of the molten catalytic mixture 10 can be 32.1 x 10 -3 Pa.s, 30.1 x 10 -3 Pa.s, 28.1 x 10 -3 Pa.s, 26.1 x 10 -3 Pa.s, the lower limit of the viscosity of the molten catalytic mixture 10 can be 10.3 x 10 -3 Pa.s, 12.3 x 10 -3 Pa.s, 14.3 x 10 -3 Pa.s, 16.3 x 10 -3 Pa.s. It can be understood that simply melting the metal catalyst has too large a density and too low a viscosity, which not only causes the internal expansion pressure of the bubble generated under the liquid surface to be too large, but also causes the bubble to rise too fast, such as the density of liquid copper being 8.920 g / cm 3 , the viscosity at 1150°C being 2.61 x 10 - 3 Pa.s, about 3 times the viscosity of water (25°C), the speed of the bubble rising in the liquid copper being very fast, about 14 times the speed of the bubble rising in water (about 3.5 m / s), thereby increasing the risk of the bubble breaking in the liquid, and the speed of the bubble rising being too fast, the time of the cracking reaction being too short, which cannot meet the sufficient time for the graphene to nucleate and grow on the surface of the bubble, resulting in the graphene powder having many defects, poor electrical conductivity, and low yield (less than or equal to 25 wt% in copper); at the same time, due to the bubble rising too fast and being unstable, the bubbles are easy to converge, thereby reducing the contact area of the overall bubble and the metal catalyst, thereby reducing the yield. By controlling the viscosity of the preset glass material and the molten catalytic mixture 10 in the above range, the viscosity of the preset glass material is much higher than that of the metal catalyst, the viscosity of the molten catalytic mixture 10 is adjusted to an appropriate range, which can improve the stability of the bubble in the molten catalytic mixture 10, prevent the bubble from aggregating or breaking, ensure the contact area of the bubble and the metal catalyst, reduce the rising speed of the bubble, prolong the residence time of the bubble in the molten mixture, make the cracking reaction more sufficient, improve the conversion rate, thereby improving the yield of graphene, and reducing the number of defects of the graphene product, thereby improving the yield and quality of the graphene. In addition, by adjusting the viscosity range, it is avoided that the viscosity is too high to cause the bubble to stay for too long, resulting in the graphene having too many layers and the production efficiency being too low, and it is avoided that the viscosity is too low to meet the reaction time requirement, and the bubble aggregation is improved.

[0050] In some embodiments, the density of the molten pre-set glass material is 2.2-2.6 g / cm 3 In some embodiments, the density of the molten catalytic mixture 10 is 8.2-8.4 g / cm 3 In this way, the density of the molten catalytic mixture is reduced, and the rising speed of the bubbles is slowed down.

[0051] In some embodiments, the rising speed of the bubbles in the molten catalytic mixture 10 is 1.51 m / s-2.50 m / s.

[0052] In some embodiments, the carbon-containing gas is introduced into the molten catalytic mixture 10 from the bottom thereof through the air pipe 20, and the distance between the air outlet 21 of the air pipe 20 and the liquid surface of the molten catalytic mixture 10 is 30-50 cm. Please refer to the drawing, which shows a schematic view of the distance L between the air outlet 21 of the air pipe 20 and the liquid surface of the molten catalytic mixture 10.

[0053] Specifically, the upper limit of the distance can be 50 cm, 48 cm, 45 cm, 42 cm, etc., and the lower limit of the distance can be 30 cm, 32 cm, 35 cm, 38 cm, etc. In this way, the distance is controlled within the above range, the residence time of the bubbles can be controlled in conjunction with the viscosity range, and through the above viscosity setting, the height requirement of the molten catalytic mixture 10 can be reduced, thereby reducing the equipment volume and production cost, avoiding excessive liquid surface height, excessive air resistance, and excessive damage to the control instruments, etc.

[0054] In some embodiments, the mass ratio between the metal catalyst and the pre-set glass material is (97%-99%):(1%-3%). Specifically, the mass ratio between the pre-set glass material and the metal catalyst can be 1%:99%, 2%:99%, 3%:99%, 4%:99%, etc., or 5%:97%, 4%:97%, 3%:97%, 2%:97%, etc. In this way, by setting the above mass ratio, the excessive viscosity caused by the excessive proportion of the glass material can be avoided, the contact area between the metal catalyst and the bubbles can be reduced, and the viscosity requirement of the molten mixture can be met when the proportion of the glass material is too low. Moreover, the glass material and the metal catalyst are mutually inert and do not react chemically, thereby avoiding the reduction of the catalytic performance.

[0055] In some embodiments, the carbon-containing gas comprises inert gas and preset carbon source gas, and the standard state volume ratio between the inert gas and the preset carbon source gas is 100%:(3%-20%); specifically, the lower limit of the volume ratio can be 100%:3%, 100%:5%, 100%:7%, 100%:10%, etc., and the upper limit of the volume ratio can be 100%:20%, 100%:18%, 100%:17%, 100%:15%, etc. In this way, by controlling the volume ratio between the inert gas and the preset carbon source gas to the above range, the concentration of the preset carbon source gas in the bubbles can be diluted, so as to avoid too high content causing too many defects and too thick layers of graphene, or even forming carbon black, or too low content causing graphene unable to nucleate and grow or too low yield.

[0056] In some embodiments, the preset carbon source gas is non-oxygen-containing carbon-containing gas; in this way, compared with using oxygen-containing carbon source with lower activation energy, the generation of H2O byproduct by cracking can be avoided, and the carbon consumption caused by the reaction of the byproduct in the gaseous carbon source can be avoided, and at the same time, the etching of part of graphene by the byproduct CO2 can be avoided, thereby avoiding the reduction of yield.

[0057] Specifically, the preset carbon source gas can include but is not limited to at least one of methane, ethane, propane, butane, ethylene, propylene, natural gas, liquefied gas, acetylene, propyne, coal bed methane, and biogas.

[0058] In some embodiments, the inert gas in the carbon-containing gas can include but is not limited to nitrogen or helium, etc.

[0059] Specifically, in the preparation process of the graphene, the pressure in the heating furnace can be normal pressure.

[0060] In addition, the catalytic activity of the metal catalyst to the preset carbon source gas is much greater than the catalytic activity of the chemically composed molten preset glass material, for example, at 1200℃, the catalytic efficiency of liquid copper to methane is 0.3 s / mol, and the catalytic efficiency of the molten preset glass material to methane is 30 s / mol, so the catalytic activity of the metal catalyst is dominant, the preset carbon source gas is cracked by the metal catalyst, and after the preset carbon source gas grows and covers the graphene film on the surface of the bubble, the growth is terminated due to the loss of catalytic activity on the surface, so although the residence time of the bubble in the metal composite substrate with the added glass material is prolonged, the crystalline quality of the graphene is improved while the thickness of the graphene product is not increased, thereby obtaining a high-quality thin-layer graphene product.

[0061] Through Raman test and electron microscope test, please refer to Figures 3-5 , the I D / I Gless than 0.15, the yield is greater than or equal to 80%, the proportion of graphene with 5 layers or less in the graphene powder is higher than 85%, and the conductivity of the graphene powder at 200 MPa is greater than or equal to 1.49 x 10 4 S / m.

[0062] The following describes specific embodiments of the present application in combination with the above liquid catalysis-based graphene powder preparation method. The embodiments use the following method to prepare graphene powder.

[0063] 1) Fix the graphite crucible in the induction heating coil of the heating furnace, add ordinary glass with a chemical composition of Na2SiO3, CaSiO3, and SiO2 and a metal catalyst into the graphite crucible at a first preset mass ratio (A), and the amount of addition is that when the gas pipe 20 is inserted below the liquid surface for gas growth after melting, the outlet 21 of the gas pipe 20 is at a preset distance (L) from the liquid surface; wherein A = ordinary glass: metal catalyst, the second preset mass ratio B between Na2SiO3, CaSiO3, and SiO2 = Na2SiO3: CaSiO3: SiO2;

[0064] 2) Use nitrogen to replace the gas in the furnace cavity of the heating furnace, then open the exhaust valve of the heating furnace and continuously introduce nitrogen, open the heating system, and heat the metal catalyst and ordinary glass in the crucible to a molten state, and make the temperature of the molten catalyst mixture 10 reach a preset growth temperature (T);

[0065] 3) Cover the crucible cover, introduce N2 and CH4 with a preset volume ratio (C) of volume flow rate through the gas pipe 20 in the molten catalyst mixture 10, and the graphene grown on the surface of the gas bubble is separated on the liquid surface of the molten catalyst mixture 10 and discharged to the collection device with the gas flow to obtain graphene powder, C = N2: CH4;

[0066] 4) Use an acidic washing agent to remove impurities from the graphene powder, remove the metal catalyst and glass impurity particles, wash with water for 2 times or more, and dry at 100°C for 5h to obtain pure graphene powder. The acidic washing agent can be an aqueous solution of HNO3 / HCl / HF with a molar concentration ratio of 4:2:1.

[0067] In addition, the rising speed (V) of the gas bubble in the molten catalyst mixture 10 is obtained by shooting with a high-speed camera for bubble speed calculation, and the Raman spectrum, SEM image, and TEM image of the graphene product are obtained by Raman, SEM, and TEM tests to obtain the I D / I GThe ratio is the mass ratio of the graphene powder within 5 layers in the product; the graphene yield is determined by the ratio of the product mass obtained by weighing the purified graphene to the carbon mass in the reaction gas CH4 passed in under the corresponding growth time; and the conductivity of the graphene powder after purification is tested by a powder conductivity tester when the pressure is 200 MPa.

[0068] The difference between Comparative Example 1 and Example 1 is that pure metal catalyst copper is added in the crucible instead of ordinary glass; the difference between Comparative Example 2 and Example 1 is that ordinary glass with the same chemical composition as in Example 1 is added in the crucible instead of metal catalyst; the difference between Comparative Example 3 and Example 1 is that the mass ratio of ordinary glass to metal copper is 0.5%:99.5%; and the difference between Comparative Example 4 and Example 1 is that the mass ratio of ordinary glass to metal copper is 4%:96%.

[0069] The related parameters of Examples 1-11 and Comparative Examples 1-4 are shown in Table 1 and Table 2.

[0070] Table 1

[0071]

[0072] In the examples 1-11 and comparative examples 1-4, the nitrogen flow rate is 100 L / min, 75 L / min, 78 L / min, 95 L / min, 70 L / min, 95 L / min, 98 L / min, 90 L / min, 92 L / min, 87 L / min, 85 L / min, 100 L / min, 100 L / min, 100 L / min, 100 L / min, respectively, and the methane flow rate is 20 L / min, 3.75 L / min, 5.46 L / min, 14.25 L / min, 2.10 L / min, 8.55 L / min, 11.76 L / min, 13.50 L / min, 15.64 L / min, 12.18 L / min, 13.60 L / min, 20 L / min, 20 L / min, 20 L / min, 20 L / min, respectively, according to the order from top to bottom in the table.

[0073] Table 2

[0074]

[0075] Figures 3-5 The Raman spectrum, SEM and TEM images of the graphene powder in Example 1 are shown as examples, the Raman spectrum shows that the graphene powder obtained in Example 1 has obvious graphene characteristic 2D peak signal, I D / I G=0.138, indicating that the graphene has very few defects and high crystal quality. The SEM image shows that the graphene powder has a large number of obvious wrinkles and a low bulk density, which can further reflect the thickness of the graphene, indicating that the graphene powder is very thin. Further statistical data based on the TEM characterization results show that the graphene powder has less than 5 layers, accounting for 87%, and has excellent conductive properties and a yield of more than 80%. It should be noted that the result characterization diagrams of other examples are not shown, but the method for obtaining the performance parameters is the same as that of Example 1.

[0076] Further, combined with Figures 6-11 It can be seen that the graphene powder 1 prepared only by liquid metal catalyst in Comparative Example 1 D / I G The results show that the conductivity of the graphene in Comparative Example 1 is lower than that in Example 1, indicating that the conductivity is poor. In addition, the graphene yield in Comparative Example 1 is only 24%, which is significantly lower than that in Example 1, resulting in waste of carbon source and low production efficiency. Figure 7 As shown, the 2D peak signal of the graphene powder in Comparative Example 2 is very weak, indicating that the graphene structure has a large number of defects, and the graphene is relatively thick, with graphene with more than 5 layers accounting for about 90%, and the yield is extremely low, indicating that the catalytic activity of molten glass alone is poor and is not conducive to graphene growth; in Comparative Examples 3 and 4, although the molten catalytic mixture 10 is used as a catalyst, since the mass ratio between the two exceeds the preset range, when the glass ratio is too low (Comparative Example 3), there is no obvious improvement in the quality and yield of graphene; when the glass ratio is too high (Comparative Example 4), the defects and thickness in the graphene increase significantly, and the conductivity and yield are significantly lower than the graphene in Example 1.

[0077] In summary, the present application has the following beneficial effects: the present application adopts molten metal and preset glass material as catalytic matrix, and introduces carbon-containing gas therein, so as to form graphene in bubbles under the high temperature and catalytic action of the molten mixture, and then rises to above the liquid level for easy collection, and the viscosity of the catalytic matrix is ​​increased by the preset glass material to slow down the rising speed of the bubbles, prolong the residence time of the bubbles in the matrix, ensure that the cracking of the gaseous carbon source is more sufficient, the conversion rate is higher, and thus the yield of graphene is increased, while by extending the growth time, the defects of the graphene film are reduced and the crystallization quality of the product is improved. Moreover, by increasing the viscosity of the matrix, the stability of the bubbles can be improved, a large number of bubbles are avoided from converging, and thus the full contact of the gaseous carbon source with the catalyst is ensured, further improving the yield. In addition, the scheme is simple to operate, the process is controllable, and it is easy to expand, and is suitable for large-scale industrial production.

[0078] The foregoing description has been set forth in terms of specific embodiments of the application. It is to be understood that modifications which do not depart from the scope of the application will occur to those skilled in the art upon a reading of the foregoing description. Accordingly, it is intended that the scope of the application be governed by the following claims.

Claims

1. A method for preparing graphene based on liquid catalysis, characterized in that: The method comprises: S11: Providing a mixture of a metal catalyst and a preset glass material, and heating the mixture to a preset temperature in an inert atmosphere so that the metal catalyst and the preset glass material are both molten to obtain a molten catalytic mixture, and ensuring that the temperature of the molten catalytic mixture is greater than or equal to a preset growth temperature; the mass ratio of the metal catalyst to the preset glass material is (97% to 99%):(1% to 3%); S12: introducing a carbon-containing gas from the bottom of the molten catalytic mixture to form bubbles in the molten catalytic mixture, wherein graphene is generated on the surface of the bubbles due to the catalytic effect of the molten catalytic mixture during the rising process of the bubbles; the carbon-containing gas includes an inert gas and a preset carbon source gas, and the preset carbon source gas is a non-oxygen-containing carbon-containing gas; S13: collecting the graphene that rises with the bubbles to above the molten catalytic mixture to obtain graphene powder, wherein the electrical conductivity of the graphene powder at 200 MPa is greater than or equal to 1.49×10 4 S / m.

2. The preparation method according to claim 1, characterized in that The preset glass material includes Na2SiO3 and at least one of SiO2 and CaSiO3, and the mass proportion of Na2SiO3 in the preset glass material is 47% to 56%.

3. The preparation method according to claim 1, characterized in that The viscosity of the molten glass material is (10-100) Pa.S; the viscosity of the molten catalytic mixture is 10.3×10 -3 ~32.1×10 -3 Pa.s.

4. The preparation method according to any one of claims 1 to 3, characterized in that The carbon-containing gas is introduced from the bottom of the molten catalytic mixture through a vent pipe, and the distance between the gas outlet of the vent pipe and the upper liquid surface of the molten catalytic mixture is 30 cm to 50 cm.

5. The preparation method according to any one of claims 1 to 3, characterized in that The volume ratio between the inert gas and the preset carbon source gas is 100%:(3%-20%).

6. The preparation method according to any one of claims 1 to 3, characterized in that The preset growth temperature is 1150-1350°C.

7. The preparation method according to any one of claims 1 to 3, characterized in that The preset carbon source gas in the carbon-containing gas includes at least one of methane, ethane, propane, butane, ethylene, propylene, natural gas, liquefied gas, acetylene, propyne, coalbed methane, and biogas.

8. The preparation method according to any one of claims 1 to 3, characterized in that The metal catalyst includes copper, or an alloy of copper and one or more of lead, germanium, nickel, iron, cobalt, tin, chromium, bismuth, silver, gallium, and palladium.

9. A graphene based on liquid catalysis, characterized in that, The graphene is prepared based on the preparation method according to any one of claims 1 to 8.

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