CN114560459B

CN114560459B - Method for directly synthesizing graphene nanoribbon through surface catalysis of salt microcrystal

Info

Publication number: CN114560459B
Application number: CN202210061502.XA
Authority: CN
Inventors: 胡宝山; 付长啸; 金燕
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2022-01-19
Filing date: 2022-01-19
Publication date: 2023-08-15
Anticipated expiration: 2042-01-19
Also published as: CN114560459A

Abstract

The invention discloses a method for directly synthesizing graphene nanoribbons by surface catalysis of salt microcrystals, which comprises the following steps: preparing salt microcrystalline powder; uniformly mixing an organic compound and salt microcrystalline powder, wherein the organic compound is an organic compound which can generate naphthalene ring or perylene ring free radicals through pyrolysis at the temperature of 450-650 ℃; and (3) introducing a mixed gas of protective gas and hydrogen, calcining at 450-650 ℃ until the reaction is finished, and purifying the reacted product to obtain the graphene nanoribbon. The method breaks through the limitation of the existing method for synthesizing the graphene nanoribbon by using the noble metal substrate, selects NaCl which has large reserve and is easy to obtain as a synthesis substrate and a catalytic inducer, does not need high vacuum equipment, and has the advantages of environmental friendliness and resource conservation; and the method has the advantages of simple raw materials, low cost, good repeatability and high industrial feasibility, and is expected to realize large-scale preparation.

Description

Method for directly synthesizing graphene nanoribbon through surface catalysis of salt microcrystal

Technical Field

The invention belongs to the technical field of preparation of carbon nano materials, relates to a method for directly synthesizing a graphene nanoribbon by surface catalysis of salt microcrystals, and particularly relates to a novel technology for synthesizing the graphene nanoribbon at a specified temperature and under normal pressure by taking a solid organic compound as a precursor through induction catalysis of the salt microcrystals.

Background

Since the discovery of graphene by two scientists, k.novoselov and a.geim, university of manchester, england in 2004 (Novoselov K S, et al science,2004,306,666.), it has been the focus and focus of research in the scientific community, with excellent nanostructure and optical, electrical, thermal, mechanical properties, making it exhibit significant scientific significance and application value in theoretical and experimental research. However, compared to a general semiconductor material, the band gap of two-dimensional graphene is zero, and it is difficult to be directly applied to an electronic device requiring a high on/off ratio. Several schemes have been proposed to open the bandgap of graphene, such as applying mechanical stress (Daniel E.P, et al Phys.rev.lett.,2021,127,027601.), atomic (ion) bombardment (Pradhan J, et al carbon,2021,184,322 ～ 330.), chemical modification (zrbib, et al carbon,2019, 153:557-564.), adding a vertical electric field to the bilayer graphene surface (Prasad N, et al J. Phys.chem.c.,2020,124 (39): 21874-21885.), and preparing one-dimensional graphene nanostructures (Zhou X H, et al adv.mater, 2020,32 (6), 1905957).

Studies have shown that quasi-one-dimensional Graphene Nanoribbons (GNRs) are capable of opening a band gap using quantum confinement effects, and that the size of the band gap depends on the edge type of the GNRs (i.e., the zigzag or armchair type) and the width of the GNRs. GNRs inherit excellent physical and chemical properties of graphene and have better regulation and control property in terms of electronic structure, so that the graphene has wider application prospect. For example, high performance (high on-off ratio and high field effect mobility) field effect transistors are prepared as channel materials, silicon-based material transistors are replaced, doped catalytic materials are applied to the field of electro (opto) chemistry and the like. In addition, GNRs are also promising for applications in the field of biological and chemical sensors because of their extremely small size and ultra-fast electron transfer rates that can meet the requirements of high sensor sensitivity and rapid response. Thus, large scale preparation of GNRs and regulation of their band gap is a research hotspot.

In recent years, a plurality of preparation methods are developed by a plurality of scientific groups at home and abroad aiming at the related research of the GNRs with controllable edges and widths. At present, the preparation of GNRs can be divided into two major categories, top-down and bottom-up. "top-down" methods include the usual photolithography (Arjmandi-Tash H, et al adv. Mater. Interfaces,2021,8 (20), 2100293.), the decompressed carbon nanotube method (Li H, et al ACS appl. Mater. Interfaces,2021,13,52892-52900.), the sonochemical method (Yoon W, et al Carbon,2015,81 (1): 629-638), and the metal assisted etching method (Sarawat V, et al J. Phys. Chem. C,2019,123,18445 ～ 18454.). The GNRs produced by such methods are long with relatively narrow bandwidth distributions, but generally have low yields, irregular strip edges, may introduce many defects, and complex processing procedures. The "bottom-up" rule is largely divided into two classes, solution synthesis (Narita a, et al chem. Sci.,2019,10,964.) and surface synthesis (Chen Z P, et al adv. Mater.,2020,32 (45), 2001893.), wherein the surface synthesis (On-surface synthesis) technique has attracted extensive attention and research since 2010, enabling precise regulation of GNRs edges and bandwidths by means of sophisticated organic precursor molecular design. However, the surface of the selected Au, ag and other substrates has strong interaction with GNR, so that the transfer is relatively difficult, the noble metal cost is high, the reserves are limited, and the large-scale preparation is not easy to realize. In order to overcome the problems and achieve the aims of environmental friendliness and resource conservation, a reaction substrate which has similar functions of Au and Ag and hopefully replaces noble metals such as Au and Ag needs to be searched, and the efficiency of a surface synthesis strategy is further improved.

The metal salt is simple and easy to obtain,The method has the characteristics of good water solubility, good thermal stability and the like, and is used for assisting in synthesizing various novel materials, and has the advantages of rapidness, high yield and low cost, and at present, a method for assisting in synthesizing the carbon material by taking metal salt crystals as a catalytic template has been reported. For example, hu et al heat 1, 5-diphenylcarbohydrazide and MgCl ₂ Two-dimensional porous carbon nanoplatelets having an average pore size of 8.69nm (Hu W, et al acs maintenance chem. Li et al utilize FeCl ₃ ·6H ₂ O is used as an activator and a structure guiding template to successfully synthesize the two-dimensional porous nitrogen-doped carbon nano-sheet (Li S, et al Adv. Mater, 2017,29,1700707.). Huang et al, 2-methylimidazole and Co (NO ₃ ) ₂ ·6H ₂ O is a precursor, naCl is a salt template, and an ultrathin Co-based organic framework (Huang L, et al J. Mater. Chem. A,2017,5,18610.) with a thickness of 4.5nm is prepared by pyrolysis. The researches provide a new thought for preparing the carbon material, wherein the metal salt crystals play a critical role, and the metal salt crystals are particularly in template effect, activation effect and induction catalysis effect on the reaction. However, no report has been made so far on the direct synthesis of graphene nanoribbons by the surface catalysis of metal salt crystals.

Disclosure of Invention

In order to develop a method suitable for large-scale industrial production, the invention provides a method for directly synthesizing graphene nanoribbons based on surface catalysis of salt microcrystals. The method is mainly characterized in that solid organic compounds which are cheap and commercially available, such as 3,4,9, 10-perylene tetracarboxylic dianhydride (PTCDA) and the like are used as precursors, microcrystals which are abundant and easy to obtain, such as NaCl, liCl, KCl and the like, are used as reaction substrates, and the graphene nanoribbon can be obtained through a one-step calcination mode under normal pressure, specified atmosphere and temperature conditions.

The technical scheme adopted for solving the technical problems is as follows:

1) Salt microcrystalline powder was prepared. Weighing commercial NaCl, liCl or KCl to prepare saturated solution, slowly dripping solvent into the saturated solution under the conditions of water bath temperature control and magnetic stirring, controlling the dripping rate, filtering the mixed solution while the mixed solution is hot after the dripping of ethanol is finished, and transferring the product into a vacuum drying oven for drying to obtain the recrystallized salt microcrystalline powder. The commercial NaCl, liCl or KCl is recrystallized to adjust the size distribution, ethanol, liquid ammonia, acetone, DMF or water is used as a solvent, and the crystallization temperature, concentration, rotating speed, ethanol dropping speed and other factors are controlled to realize the controllable preparation of the NaCl, liCl or KCl particles. Preferably, the solvent may be absolute ethanol in consideration of green and economical factors.

2) And mixing the organic compound and the salt microcrystalline powder uniformly. The mixing of the organic compound as a precursor with the salt microcrystalline powder may take the form of dry mixing or wet mixing. The dry mixing achieves the aim of uniform mixing by mechanically grinding the mixture of the two; the wet mixing is carried out by transferring the mixture into proper absolute ethyl alcohol, and then magnetic stirring, vacuum drying, grinding and the like to obtain the evenly mixed mixture. For example, for dry mixing may include: weighing a certain amount of PTCDA, mixing with a proper amount of NaCl microcrystalline powder prepared in the step 1), grinding uniformly in an agate mortar, transferring to a clean porcelain boat, spreading uniformly, and covering the porcelain boat with a corundum porcelain boat cover for later use.

3) The mixture of organic compound and salt microcrystalline powder is calcined, for example, in a high temperature tube furnace. Argon (100-200 sccm) is used as shielding gas and carrier gas, hydrogen (10-50 sccm) is added to etch and modify the graphene nanoribbon, the temperature is increased to a specified temperature (450-650 ℃) at a heating rate of 5-20 ℃/min, and the temperature is kept constant for 10-240 min, so that the multi-step reaction processes of slow pyrolysis of organic compounds, free radical release, free radical polymerization into the ribbon and the like are realized. And cooling to room temperature after the completion of the preparation, and obtaining a mixture of the graphene nanoribbons and the salt. The prepared graphene nanoribbon has the bandwidth distribution of 50-1000 nm, and has obvious characteristic peaks of Raman RBLM signals, D, G, 2D and the like. Cooling to room temperature after finishing can be rapid cooling to room temperature or natural cooling to room temperature, preferably natural cooling is selected to cool to room temperature. For example, pushing the porcelain boat carrying the mixture obtained in the step 2) into a quartz tube, placing the quartz tube in the central position of a heating zone of a tube furnace, connecting the device, and ensuring sealing; ar gas is introduced for a period of time to remove air in the quartz tube, ar (100-200 sccm) and H are regulated ₂ (10-50 sccm) gas mixtureThe indication of the volume flow to the flowmeter is stable; setting parameters such as heating time, heating rate, reaction temperature and the like, and calcining the mixture; and after the reaction is finished, naturally cooling to room temperature, taking out the porcelain boat, and collecting the product, namely the mixture of the graphene nanoribbon and NaCl.

According to the invention, a solid organic matter containing a benzene ring is used as a precursor, and a graphene nanoribbon is synthesized on a metal salt base template. In the reaction process, the organic compound plays roles of serving as a raw material, pyrolyzing out free radicals and polymerizing the free radicals into bands; the metal salt plays roles of capturing free radicals, inducing free radical nucleation and catalyzing free radical polymerization growth in the reaction.

Compared with the prior art, the invention has the beneficial effects that at least one of the following is included:

1. compared with gaseous carbon sources such as methane and ethylene, the invention adopts low-cost solid organic matters as precursors, can greatly reduce the pyrolysis temperature and reduce the energy consumption.

2. The invention selects NaCl as a catalytic reaction growth substrate, does not use a metal catalyst, and has the advantages of large reserve, easy acquisition, convenient transfer, easy recycling and low price.

3. The reactions involved in the invention are all carried out under normal pressure, and expensive high-vacuum equipment is not needed.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a graph showing the temperature-time relationship of the calcination process in the method of the present invention.

Fig. 2 is an SEM image and a raman spectrum image of the graphene nanoribbons prepared in example 1.

Fig. 3 is an SEM image of graphene nanoribbons prepared in a different hybrid manner of example 2.

Fig. 4 is an SEM image of graphene nanoribbons prepared from the mixture of example 3 at different mass ratios.

Detailed Description

The present invention provides a typical but non-limiting preparation method, and in order to facilitate understanding of the technical solution of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings and specific examples.

The invention provides a method for directly synthesizing graphene nanoribbons by salt microcrystal surface catalysis, which comprises the following steps:

s01, preparing salt microcrystalline powder;

the preparation of salt microcrystalline powder can comprise the steps of preparing salt into saturated solution, adding solvent under the condition of stirring at 20-50 ℃, carrying out suction filtration and drying to obtain salt microcrystalline powder. The salt may be a metal salt, for example, naCl, liCl or KCl. For example, when the salt is NaCl, a proper amount of commercial NaCl (0.3-2.0 g) is weighed and placed in a 250ml round bottom flask to prepare a saturated solution, the water bath temperature is set to be 20-50 ℃, absolute ethyl alcohol (20-100 ml) is slowly added dropwise into the saturated solution under the stirring of a polytetrafluoroethylene magnetic stirrer (300-700 rpm), and the dropping rate is controlled to ensure that NaCl particles are evenly precipitated. And after the absolute ethyl alcohol is added dropwise, continuously maintaining stirring and water bath for 0.5-2 h, carrying out suction filtration on the obtained mixed solution while hot after the stirring is finished, transferring the product into a vacuum drying oven, drying at 60 ℃, and obtaining NaCl microcrystal particles, and grinding for later use.

S02, mixing an organic compound with salt microcrystalline powder;

mixing organic compound and salt microcrystalline powder uniformly. For example, a proper amount of PTCDA (20-100 mg) was weighed, mixed with NaCl prepared in step S01, and then ground and mixed in an agate mortar. And transferring the mixture into a clean porcelain boat for uniform paving, and covering the porcelain boat for later use.

S03, synthesizing a graphene nanoribbon;

and (3) pushing the porcelain boat carrying the mixture obtained in the step S02 into a quartz tube, and placing the porcelain boat in the central position of a heating zone of a tube furnace. The device is then connected, ensuring a seal. Firstly, introducing Ar for a certain time to remove air in the quartz tube, and then regulating Ar (100-200 sccm) and H ₂ (10-50 sccm) and then calcining at 450-650 deg.C, for example, the calcining temperature may be 500 deg.C.

S04, purifying and collecting graphene nanoribbons;

collecting the product obtained in the step S03, placing the product in a 100ml beaker, adding a proper amount of mixed solution of deionized water and absolute ethyl alcohol according to the volume ratio of 1:1, and carrying out ultrasonic treatment for 10-60 min to uniformly disperse the product. Transferring the dispersion liquid into a 10ml centrifuge tube, removing salt particles mixed in the product through centrifugal washing, and washing 3-5 groups through interaction of deionized water and ethanol. And filtering residual water from the product after centrifugal washing through vacuum filtration, transferring to a plastic culture dish, and freeze-drying for 12-24 hours to obtain purified graphene nanoribbon black powder.

Further, the organic compound may be an organic compound capable of generating a naphthalene ring or a perylene ring radical by pyrolysis at 450 to 650 ℃ and further performing a polymerization reaction. For example, the organic compound may be 3,4,9, 10-perylenetetracarboxylic dianhydride (PTCDA), 3,4,9, 10-perylenetetracarboxylic acid, N-bis (2, 6-xylene) perylene-3, 4,9, 10-tetracarboxylic acid diimide, 1,4,5, 8-naphthalene tetracarboxylic acid dianhydride (NTCDA), 1,4,5, 8-naphthalene tetracarboxylic acid, or 1,4,5, 8-naphthalene tetracarboxylic acid diimide.

Further, the salt microcrystalline powder is a cubic system, and atoms are stacked in a face-centered cubic manner, so that a nucleation site for free radicals can be provided. For example, the salt microcrystalline powder may be NaCl, liCl, and KCl microcrystalline powder.

Further, after the organic compound is mixed with the salt microcrystalline powder by a dry method, a layer of salt microcrystalline powder may be further coated on the surface thereof. For example, the organic compound may be coated with a thin layer of NaCl after being mixed with NaCl; the organic compound may be coated with a thin layer of KCl after mixing with KCl.

Further, the size of the salt crystallite powder may be 1 μm to 300 μm. The size of the salt microcrystalline powder is related to the width of the graphene nanoribbon, and the smaller the size of the salt microcrystalline powder is, the narrower the prepared graphene nanoribbon is; the larger the salt crystallite size is, the wider the graphene nanoribbon prepared by the salt crystallite size is. However, the size of the salt microcrystalline powder is not more than 300 μm, and the graphene nanoribbon may not be obtained after the salt microcrystalline powder is exceeded.

Further, the temperature of calcination is set to 450-650 ℃. Preferably, the calcination temperature of 1,4,5, 8-naphthalene tetracarboxylic dianhydride (NTCDA), 1,4,5, 8-naphthalene tetracarboxylic acid, or 1,4,5, 8-naphthalene tetracarboxylic acid diimide may be set in the range of 200 to 300 ℃. For example, for the organic compound PTCDA, the sublimation temperature of PTCDA is 450 ℃, and the pyrolysis to free radicals is 500 ℃ to 650 ℃. Too low a temperature (< 450 ℃) PTCDA cannot sublimate and pyrolyze, and the polymerization to a band reaction cannot occur; too high temperatures (> 650 ℃) PTCDA pyrolyzes too rapidly, which is detrimental to slow, stable, uniform reactions.

Further, the mass ratio of the organic compound to the salt microcrystalline powder is 1 (0.6-7). For example, the mass ratio may be 1:0.8 or 1:3 or 1:5. Preferably, the mass ratio is 1:1, and the graphene ribbon prepared by the method has the best quality under the mass ratio.

Further, in the step S03, the temperature is raised to 450-650 ℃ at a heating rate of 5-20 ℃ per minute, and the calcination time is 10-240 minutes. For example, the temperature is raised to 500 ℃ at a heating rate of 15 ℃/min, and the calcination time is 100min.

Further, for step S03, after the mixed gas of the protective gas and the hydrogen gas is introduced, the temperature-raising reaction may be performed according to the procedure shown in fig. 1 until the reaction is completed. Specifically, in the heating stage, the temperature is raised to the growth temperature (450-650 ℃ C.) at the speed of 5-20 ℃ C./min, the temperature is kept for 10-240 min, then the temperature is raised to the annealing temperature (700-800 ℃ C., annealing stage), the reaction is finished, the ceramic boat is naturally cooled to the room temperature (cooling stage), the ceramic boat is taken out, and the product is collected, wherein the obtained product is the mixture of the graphene nanoribbons and the salt. The annealing time may be 30min to 120min. Calcining at 450-650 ℃ to synthesize graphene nanoribbons and lock the ribbon-shaped graphene morphology; by providing annealing, crystallinity of the nanoribbon can be further promoted and improved, and physical and chemical properties such as conductivity and electron mobility can be further improved.

For a better understanding of the present invention, the content of the present invention is further elucidated below in connection with the specific examples, but the content of the present invention is not limited to the examples below.

Example 1

(1) 1g of NaCl sold in the market is weighed and placed in a 250ml round bottom flask to prepare saturated solution, the water bath temperature is set to be 30 ℃, 100ml of absolute ethyl alcohol is slowly added dropwise into the saturated solution under the stirring of a polytetrafluoroethylene magnetic stirrer at 500rpm, and the dropping speed is controlled to ensure that NaCl particles are evenly separated out. And after the ethanol is added dropwise, continuously maintaining stirring and water bath for 1h, filtering the obtained mixed solution while hot after the ethanol is added dropwise, transferring the product into a vacuum drying oven, drying at 60 ℃ to obtain NaCl microcrystalline powder, and grinding for later use.

(2) 50mg of PTCDA is weighed, mixed with 100mg of NaCl prepared in the step (1) and then ground and uniformly mixed in an agate mortar. And transferring the mixture into a clean porcelain boat for uniform paving, and covering the porcelain boat for later use.

(3) Pushing the porcelain boat carrying the mixture obtained in the step (2) into a quartz tube, and placing the porcelain boat in the central position of a heating zone of a tube furnace. Then the device is connected, the sealing is ensured, ar is firstly led for a certain time to remove air in the quartz tube, and then Ar (150 sccm) and H are regulated ₂ (30 sccm) the flow of the mixed gas to the flowmeter showed stable. Heating to a growth temperature of 550 ℃ at a speed of 15 ℃/min, preserving heat for 2 hours, heating to an annealing temperature of 750 ℃ at a speed of 15 ℃/min, naturally cooling to room temperature after the reaction is finished, taking out a porcelain boat, and collecting a product, wherein the obtained product is a mixture of graphene nanoribbons and NaCl.

(4) Collecting the product obtained in the step (3), and placing the product in a 100ml beaker according to the volume ratio of 1:1 adding a proper amount of mixed solution of deionized water and absolute ethyl alcohol, and carrying out ultrasonic treatment for 30min to uniformly disperse the mixed solution. The dispersion was transferred to a 10ml centrifuge tube, the mixed NaCl in the product was removed by centrifugal washing, and 4 groups were washed alternately with deionized water and ethanol. And filtering residual water from the washed product by vacuum filtration, transferring to a plastic culture dish, and freeze-drying for 12 hours to obtain purified graphene nanoribbon black powder. Fig. 2 is an SEM image (a)) and a raman spectrum image (b)) of a graphene nanoribbon, which shows that the width of the prepared graphene nanoribbon is distributed between 50nm and 1000nm, and the graphene nanoribbon has significant raman RBLM signals and characteristic peaks of D, G, 2D and the like.

Example 2: the effect of different modes of mixing PTCDA and NaCl on graphene nanoribbon growth was compared.

Preparing NaCl microcrystalline powder according to the step (1) of the example 1, drying and grinding for later use.

50mg PTCDA and 350mg NaCl are accurately weighed, and are respectively and uniformly mixed in a mixing mode I (dry mixing) and a mixing mode II (wet mixing), and a corundum porcelain boat cover is used for covering the porcelain boat for later use.

Mixing mode I: the weighed PTCDA and NaCl are mixed and then placed in an agate mortar, ground for 15min and uniformly mixed, and then the mixture is transferred into a clean porcelain boat for paving.

Mixing mode II: the weighed PTCDA and NaCl were dispersed in 25ml of absolute ethanol under ice water bath conditions, stirred using a polytetrafluoroethylene magnetic stirrer, and the rotation speed was controlled at 300rpm, and stirring was continued for 1 hour. Filtering the mixed solution, transferring to a glass culture dish, vacuum drying for 12h, grinding to obtain a PTCDA and NaCl mixture, and transferring to a porcelain boat for paving.

And (3) carrying out a nano belt growth procedure according to the step (3). Ar flow is regulated to 100sccm, H ₂ The flow rate is 20sccm, the temperature is firstly increased to 525 ℃ at the heating rate of 5 ℃/min, and the temperature is maintained for 60min, so that the PTCDA is pyrolyzed and the free radicals are polymerized into a belt. And then heating to 700 ℃ at a heating rate of 5 ℃/min, and maintaining for 90min to promote the crystallization of the graphene nanoribbon. And after the reaction is finished, naturally cooling to room temperature, stopping ventilation, disassembling the device, and collecting the product.

Fig. 3 is a field emission Scanning Electron Microscope (SEM) image of graphene nanoribbons prepared in different hybrid ways as observed in situ on NaCl particles. From the figure, it can be seen that the graphene strips can be grown in both mixing modes, but the dry mixing mode has better induction promotion effect on the growth of the graphene nanoribbons, and is characterized by more strips, larger coverage and more complete morphology (as shown in fig. 3 (b)). Thus, preferably, a dry mixing approach may be used, which is more suitable for the growth of graphene nanoribbons.

Example 3: the effect of different mass ratios of PTCDA and NaCl on graphene nanoribbon growth was compared.

Accurately weighing 50mg of PTCDA and a certain mass of NaCl, mixing the PTCDA and the NaCl by adopting a dry mixing mode, putting the mixture into an agate mortar, grinding the mixture for 15min and uniformly mixing the mixture. Transferring the mixture to a clean porcelain boat for paving, and then covering the porcelain boat with a corundum porcelain boat cover for standby. This step sets 4 comparative experimental parameters: the mass of the weighed NaCl is respectively as follows: 15mg, 50mg, 150mg, 350mg, the products were marked in sequence as: GNR-15 (fig. 4 (d)), GNR-50 (fig. 4 (c)), GNR-150 (fig. 4 (b)), GNR-350 (fig. 4 (a)).

Fig. 4 is a field emission Scanning Electron Microscope (SEM) image of graphene nanoribbons obtained from four control experiments in situ on NaCl particles. It can be seen that the change in mass ratio shows a significant effect on the growth of graphene nanoribbons. The concrete steps are as follows: as the NaCl quality is reduced from 350mg to 50mg, the quality (quantity, coverage and morphology) of the grown graphene nanoribbons is greatly improved; there was some degradation in nanoribbon quality as the NaCl mass was reduced from 50mg to 15 mg. Therefore, the quality control and optimization of the graphene nanoribbon can be realized by adjusting the mixing ratio of PTCDA and NaCl, and the quality of the prepared graphene nanoribbon is the best when the mass ratio of PTCDA to NaCl is 1:1.

Finally, it is noted that the above description is only a basic description of the inventive concept, and the above embodiments are only for illustrating the technical solution of the present invention, not limited to the above method, and any equivalent transformation made according to the technical solution of the present invention falls within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for directly synthesizing graphene nanoribbons by surface catalysis of salt microcrystals, which is characterized by comprising the following steps:

s01, preparing salt microcrystalline powder, wherein the size of the salt microcrystalline powder is l mu m-300 mu m;

s02, uniformly mixing an organic compound and salt microcrystalline powder, wherein the organic compound is an organic compound which can generate naphthalene ring or perylene ring free radicals through pyrolysis at the temperature of 450-650 ℃;

s03, introducing a mixed gas of protective gas and hydrogen, calcining at 450-650 ℃ until the reaction is finished, and purifying the reacted product to obtain the graphene nanoribbon.

2. The method for directly synthesizing graphene nanoribbons by salt microcrystal surface catalysis according to claim 1, wherein the organic compound is 3,4,9, 10-perylenetetracarboxylic dianhydride, 3,4,9, 10-perylenetetracarboxylic acid diimide, N-bis (2, 6-xylene) perylene-3, 4,9, 10-tetracarboxylic acid diimide, 1,4,5, 8-naphthalene tetracarboxylic acid dianhydride, 1,4,5, 8-naphthalene tetracarboxylic acid, or 1,4,5, 8-naphthalene tetracarboxylic acid diimide.

3. The method for directly synthesizing graphene nanoribbons by surface catalysis of salt micro-products according to claim 1 or 2, wherein the salt micro-crystal powder is NaCl micro-crystal powder, liCl micro-crystal powder or KCl micro-crystal powder.

4. The method for surface-catalyzed direct synthesis of graphene nanoribbons with salt crystallites according to claim 1 or 2, wherein uniformly mixing the organic compound with the salt crystallite powder comprises: mixing the organic compound with the salt microcrystalline powder and mechanically milling to mix uniformly, or mixing the organic compound with the salt microcrystalline powder uniformly comprises: mixing the organic compound with salt microcrystalline powder, adding into absolute ethyl alcohol, stirring, vacuum drying, and grinding to obtain uniform mixture.

5. The method for directly synthesizing graphene nanoribbons by surface catalysis of salt microcrystals according to claim 1 or 2, wherein the mass ratio of the organic compound to the salt microcrystal powder is 1 (0.6-7).

6. The method for directly synthesizing graphene nanoribbons by surface catalysis of salt microcrystals according to claim 5, wherein the mass ratio of the organic compound to the salt microcrystal powder is 1:1.

7. The method for directly synthesizing the graphene nanoribbon by surface catalysis of salt microcrystals according to claim 1, 2 or 6, wherein the flow rate of the shielding gas is 100 sccm-200 sccm, and the flow rate of the hydrogen gas is 10 sccm-50 sccm.

8. The method for directly synthesizing the graphene nanoribbon by surface catalysis of salt microcrystals according to claim 1, 2 or 6, wherein in the step S03, the temperature is raised to 450-650 ℃ at a temperature raising rate of 5-20 ℃ per minute, and the calcination time is 10-240 minutes.

9. The method for directly synthesizing the graphene nanoribbon by surface catalysis of salt microcrystals according to claim 8, wherein the method further comprises the steps of heating to 700-800 ℃ at a heating rate of 5-20 ℃/min after the completion of calcination, and cooling to room temperature after annealing for 30-240 min.