A method for preparing highly stable two-dimensional black phosphorus

Abstract

The present invention provides a method for preparing high-stability two-dimensional black phosphorus. First, a phosphorus source and an iodine source are introduced into a reaction system for preliminary preheating and activation. After being fully activated in the raw material area of ​​the reaction system, they are slowly transferred to the crystal growth area of ​​the reaction system. The phosphorus source and the transport agent flow through the liquid to the catalyst and are fully converted in the intermediate formation area. The converted intermediate slowly moves to the crystal nucleation growth area to begin crystal nucleation and growth. After further sufficient reaction, the crystal nucleation growth point continues to extend and grow, and finally the black phosphorus crystal slowly nucleates and grows in blocks. After the crystal growth is completely cooled to room temperature, the unconverted raw materials are reused until they are finally converted into black phosphorus crystals and tail gas. The tail gas is absorbed and converted into other by-products. The use of high-temperature and high-pressure resistant pipelines can achieve efficient transportation of gaseous phosphorus, thereby extending the growth time of black phosphorus crystals and improving the growth efficiency of black phosphorus crystals.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of a novel two-dimensional material black phosphorus, and in particular to a method for preparing high-stability two-dimensional black phosphorus. Background Art

[0002] The research and development and application of emerging materials are one of the mainstream directions of scientific development in the 21st century. In 2014, the successful preparation of two-dimensional black phosphorus field-effect transistors attracted widespread attention from scientists. Because of its energy gap, layered structure and excellent physical properties, it started a new round of black phosphorus research. However, at that time, the research on black phosphorus in nanomaterials was far from enough. Further research found that by regulating the energy band layer number of black phosphorus (0.3~0.2eV), it is possible to switch between insulating and conductive states, and the electron migration speed of black phosphorus is fast (greater than 1000 cm 2 V -1 s -1 ), the closure is more significant (10 5 ), which has greatly promoted its widespread application in electronic and optoelectronic devices. Black phosphorus, due to its unique mechanical properties, electrochemical performance, and thermal anisotropy, has shown promising applications not only in field-effect transistors but also in new energy batteries, high-efficiency catalysis, optoelectronic communications, and biomedicine.

[0003] Compared with other two-dimensional materials such as graphene and molybdenum disulfide, the preparation conditions of black phosphorus are more stringent, and there is great resistance to industrial scale-up production. Currently, the methods for preparing black phosphorus worldwide include mineralization, high-pressure method, mechanical ball milling, mercury reflux method and bismuth melting method, among which the mineralization method is more common. The conversion of red phosphorus into black phosphorus through chemical vapor transport has received widespread attention from scientists and plays a vital role in promoting the application of black phosphorus. However, the current mineralization method for preparing black phosphorus still has the following problems: Because the experimental parameters of temperature and pressure are not precisely controlled, crystal formation in a closed reaction system is achieved only by controlling temperature. This causes the raw materials to be in a multiphase mixed single system solid-phase transport phase during heating. This leads to insufficient dissolution of phosphorus vapor during intermediate formation and uncoordinated phosphorus vapor migration, resulting in insufficient conversion to black phosphorus crystals during crystal growth or difficulty in further conversion. Inaccurate temperature field control leads to incomplete reaction and unstable crystal nucleation, making it difficult to fully explain the black phosphorus crystal growth mechanism. After the reaction, the byproducts are difficult to recycle and are highly reactive, making them prone to flash explosions. These factors lead to high black phosphorus preparation costs, low raw material utilization, and reduced safety factors, making them unsuitable for industrial mass production. Therefore, a method for preparing highly stable two-dimensional black phosphorus was developed. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing highly stable two-dimensional black phosphorus.

[0005] The purpose of the present invention is to provide a method for preparing high-stability two-dimensional black phosphorus to address the problems existing in the above mineralization method for preparing black phosphorus. The method can realize the preparation of green, circular, high-quality products, and is safe, efficient and easy to control. The method can not only prepare high-purity black phosphorus crystals, but also significantly improve the utilization rate of raw materials, save crystal preparation costs, and also provide a research path for further exploring the growth mechanism of black phosphorus crystals. Moreover, it can be assembled and connected with current industrial yellow phosphorus production equipment to realize the preparation of black phosphorus crystals by adopting an integrated production process based on the yellow phosphorus industry.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-stability two-dimensional black phosphorus reaction system includes a heating system, a feeding system, a flow system, and a reaction system, wherein the feeding system includes a phosphorus source feeding system, an iodine feeding system, and a tin feeding system;

[0008] The outlet of the phosphorus source feeding system and the outlet of the iodine feeding system are respectively connected to the inlet of the flow system;

[0009] The outlet of the tin feeding system is connected to the inlet of the reaction system;

[0010] The outlet of the flow system is connected to the inlet of the reaction system.

[0011] The reaction system is provided with a cleaning system and a waste liquid recovery system; the cleaning system is used to clean the product after the reaction of the reaction system, and the waste liquid recovery system is used to recover the waste liquid after the reaction.

[0012] The reaction system is connected to the top inlet of the phosphorus source feeding system via the filtering system; and the top outlet of the phosphorus source feeding system is connected to the inlet of the phosphine collecting system.

[0013] The flow system, reaction system, cleaning system and waste liquid recovery system are respectively connected to the heating system; and the temperature control inside the flow system and the reaction system is realized.

[0014] The phosphorus source feeding system, iodine feeding system and tin feeding system are respectively provided with a phosphorus vapor pressure relief system, an iodine vapor pressure relief system and a tin pressure relief system for controlling the pressure inside the system.

[0015] The outlets of the phosphorus source feeding system and the iodine source feeding system are directly connected to the raw material area of ​​the reaction system respectively;

[0016] The outlet of the tin source feeding system is directly connected to the catalyst area of ​​the reaction system;

[0017] A supercharger is provided at the outlet of the reaction system for supercharging the pressure in the supercharging zone of the reaction system to change the pressure in the reaction system.

[0018] The entire reaction system is placed on a heating device, and the temperature of the reaction system is regulated by a temperature control program on the heating device.

[0019] A pressure detection and packaging area is provided on the side of the crystal nucleation and growth area for detecting the crystal nucleation and growth pressure and packaging the nucleation end of the reaction system.

[0020] The reactor can be connected to an external tail gas emission absorption device to recycle a small amount of phosphine tail gas.

[0021] The entire reaction system can be connected to an external pipeline to recycle unreacted raw materials into black phosphorus.

[0022] The phosphorus source feeding system, iodine source feeding system and tin source feeding system are respectively provided with a phosphorus vapor pressure relief system, an iodine vapor pressure relief system and a tin pressure relief system for regulating the pressure inside the device.

[0023] The present invention provides a method for preparing high-stability two-dimensional black phosphorus, comprising the following steps:

[0024] (S1) Under a protective gas atmosphere, the three raw materials of red phosphorus, tin and iodine are preheated and activated, that is, they are respectively transported into the reaction system at a certain temperature and then the heating system is turned on for activation and preheating;

[0025] (S2) After the red phosphorus and iodine are preheated and activated; the gaseous red phosphorus and gaseous iodine are directed to flow from the raw material area to the intermediate formation area in the reaction system; the gaseous red phosphorus and iodine are flowed through the liquid catalyst and continuously converted in the intermediate formation area of ​​the reaction system and directed to flow to the crystal nucleation and growth area; finally, the intermediate is gradually converted into black phosphorus crystals under cooling conditions, which nucleate and grow uniformly and precipitate iodine vapor and liquid catalyst.

[0026] (S3) The reaction system is heat-treated by a heating device for continuous black phosphorus crystal preparation, and black phosphorus crystals are prepared after the crystals are fully grown.

[0027] Unreacted red phosphorus is recycled through a circulation pipeline to produce secondary black phosphorus crystals. After the crystals are fully grown, the iodine and unreacted red phosphorus are recycled, a small amount of phosphine vapor is recovered as tail gas, and other by-products are recovered and converted into other by-products.

[0028] As a preferred technical solution, the heating devices in (S1), (S2) and (S3) are steam heating or electric heating;

[0029] As a preferred technical solution, the temperature control of the reaction system described in (S1), (S2) and (S3) adopts segmented heating temperature control to enable the raw materials to be transported in a directional manner within the reaction system.

[0030] As a preferred technical solution, the pressure control of the reaction system described in (S1), (S2) and (S3) adopts a one-way pressurization method to enable the raw materials to be transported in a direction within the reaction system.

[0031] As a preferred technical solution, the secondary recycling described in (S4) can be carried out through an external reaction pipeline, and the recovery of tail gas and by-products can be achieved through an external pressure relief discharge pipeline.

[0032] As a preferred technical solution, the red phosphorus in S1) is preheated to a temperature of 590-650° C. in its transport device.

[0033] As a preferred technical solution, the iodine is preheated to a temperature of 45-80°C in its transport device.

[0034] As a preferred technical solution, the preheating temperature of tin in its transport device is 235~300℃.

[0035] As a preferred technical solution, the temperature of the raw material zone in the reaction system is 600~650℃.

[0036] As a preferred technical solution, the temperature of the intermediate formation zone in the reaction system is 550-580°C.

[0037] As a preferred technical solution, the temperature of the crystal nucleation and growth zone in the reaction system is 480-530°C.

[0038] As a preferred technical solution, the pressure range of the pressurized zone is 0-100 MPa.

[0039] As the preferred technical solution, all pipelines are connected to an external emergency pressure relief and emptying system.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1) The present invention prepares black phosphorus crystals through a method for preparing highly stable two-dimensional black phosphorus, ensuring that highly stable two-dimensional black phosphorus crystals are prepared under appropriate temperature and pressure.

[0042] 2) This preparation method uses a pressurizing device and a heating device to control the pressure and temperature so that the raw materials can flow fully under the action of the transport agent, and then fully react in the reaction device and finally convert into black phosphorus crystals. This can solve the current problem of insufficient reaction in the preparation of black phosphorus crystals and can obtain high-quality black phosphorus crystals.

[0043] 3) The use of high-temperature and high-pressure resistant pipelines can achieve efficient transportation of gaseous phosphorus, thereby extending the growth time of black phosphorus crystals and improving the growth efficiency of black phosphorus crystals.

[0044] 4) This method is simple and efficient, the conditions are easy to control, and it has good safety and stability. It can reduce the amount of transport agents and catalysts used and fully improve the utilization rate of raw materials, significantly reducing the cost of preparing high-quality black phosphorus crystals.

[0045] 5) This method can be assembled and connected with current industrial yellow phosphorus production equipment to achieve continuous production and preparation of black phosphorus crystals by adopting an integrated production process based on the yellow phosphorus industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a process flow chart for Example 1 of the present invention. The diagram includes a heating system 1, a feeding system 2, a flow system 3, a reaction system 4, a filtration system 5, a phosphine collection system 6, a cleaning system 7, and a waste liquid recovery system 8. The diagram also includes a phosphorus source feeding system 201, an iodine feeding system 202, a tin feeding system 203, a phosphorus vapor pressure relief system 204, an iodine vapor pressure relief system 205, and a tin pressure relief system 206.

[0047] Figure 2 Schematic diagram of the preparation method of Example 2 of the present invention.

[0048] Figure 3 This is a physical picture of the black phosphorus prepared in Example 2.

[0049] Figure 4 This is a physical picture of the black phosphorus prepared in Example 3.

[0050] Figure 5 This is a physical picture of the black phosphorus prepared in Example 4.

[0051] Figure 6 This is the XRD pattern of black phosphorus prepared in Example 2.

[0052] Figure 7 This is the XRD pattern of black phosphorus prepared in Example 3.

[0053] Figure 8 This is the XRD pattern of black phosphorus prepared in Example 4.

[0054] Figure 9 This is the Raman pattern of black phosphorus prepared in Example 2.

[0055] Figure 10 This is the Raman pattern of black phosphorus prepared in Example 3.

[0056] Figure 11 This is the Raman pattern of black phosphorus prepared in Example 3.

[0057] Figure 12 This is the SEM image of black phosphorus prepared in Example 2.

[0058] Figure 13 This is the SEM image of black phosphorus prepared in Example 3.

[0059] Figure 14 This is the SEM image of black phosphorus prepared in Example 4. DETAILED DESCRIPTION

[0060] Example 1

[0061] like Figure 1 A green and efficient system for preparing black phosphorus by mobile phase includes a heating system 1, a feeding system 2, a flow system 3, and a reaction system 4. The feeding system 2 includes a phosphorus source feeding system 201, an iodine feeding system 202, and a tin feeding system 203.

[0062] The outlet of the phosphorus source feeding system 201 and the outlet of the iodine feeding system 202 are respectively connected to the inlet of the flow system 3;

[0063] The outlet of the tin feeding system 203 is connected to the inlet of the reaction system 4;

[0064] The outlet of the flow system 3 is connected to the inlet of the reaction system 4 .

[0065] The reaction system 4 is provided with a cleaning system 7 and a waste liquid recovery system 8; the cleaning system 7 is used to clean the product after the reaction of the reaction system 4, and the waste liquid recovery system 8 is used to recover the waste liquid after the reaction.

[0066] The reaction system 4 is connected to the top inlet of the phosphorus source feeding system 201 via the filtering system 5 ; the top outlet of the phosphorus source feeding system 201 is connected to the inlet of the phosphine collecting system 6 .

[0067] The flow system 3 , the reaction system 4 , the cleaning system 7 , and the waste liquid recovery system 8 are respectively connected to the heating system 1 , and realize temperature control inside the flow system 3 and the reaction system 4 .

[0068] The phosphorus source feeding system 201 , the iodine feeding system 202 , and the tin feeding system 203 are respectively provided with a phosphorus vapor pressure relief system 204 , an iodine vapor pressure relief system 205 , and a tin pressure relief system 206 for controlling the pressure inside the systems.

[0069] The feeding system is connected to a temperature control cabinet, etc., which is used to safely place red phosphorus into the material tank and preheat and control the temperature. The flow system is connected to an infrared thermometer and a temperature control cabinet to detect phase changes in the device and control phase changes. A multi-stage temperature-controllable metal stainless steel reactor is placed in the reaction system. The reaction system is connected to a speed-controlled anti-corrosion steel pipe and a vacuum system and other safety protection systems to ensure safe feeding, product transfer and preparation of high-purity black phosphorus crystals.

[0070] In a preferred embodiment, the feeding system 2 and the flow system 3 are both provided with a heating and heat-insulating layer.

[0071] In a preferred embodiment, a micro-pressurization device is provided in the flow system, which can make the transport of gaseous red phosphorus combined with iodine vapor flow in a directional manner in the circulation system through micro-pressurization.

[0072] In a preferred embodiment, the flow system is provided with a controllable multi-channel pipeline for regulating the flow rate of the gaseous red phosphorus. The controllable multi-channel pipeline of the flow system can be disposed within the flow system and equipped with a high-temperature resistant controllable flow meter valve for regulating the flow rate of the gaseous red phosphorus, such as a multi-channel microreactor pipeline.

[0073] In a preferred solution, the tin feeding system is provided with a liquid flow meter for regulating the flow rate of the liquid tin.

[0074] In a preferred embodiment, the feed system pipeline and the flow system pipeline are both high temperature, high pressure and corrosion resistant metal pipelines.

[0075] In a preferred embodiment, the iodine material system is provided with a gas flow meter for regulating the flow rate of the liquid tin.

[0076] In a preferred embodiment, the cleaning system 7 has a built-in heating and insulation layer that can be heated by the heating system. The heating and insulation layer is made of ceramic material and can contain an alkaline solution, which is one of a KOH solution, a Ca(OH)2 solution, and a NaOH solution. The alkaline solution is used to react with the residual red phosphorus during heating, thereby playing a cleaning role in the reaction system.

[0077] In a preferred embodiment, the waste liquid recovery system includes a filtration system and a waste liquid conversion system, wherein the filtration system can be used to clean the reaction system and the catalyst can be recycled after the filter residue is precipitated, and the precipitated phosphate fertilizer and other raw materials can be used directly, and the filtrate can be calcined at high temperature to prepare low-concentration phosphoric acid.

[0078] Figure 2 Schematic diagram of the reaction system during the green and efficient preparation of black phosphorus using mobile phase.

[0079] In the preferred embodiment, the gaseous transport agent and gaseous red phosphorus flowing out of the flow system enter the reaction system and react with the liquid catalyst flowing into the reaction system, are converted into intermediates and continuously focus toward the intermediate formation area, and finally continuously nucleate and crystallize in the crystal nucleation and growth area.

[0080] Example 2

[0081] like Figure 1 、 2 In the present invention, a method for preparing two-dimensional black phosphorus with high stability is used to prepare black phosphorus crystals. The specific steps are as follows:

[0082] 1) Under a protective gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of catalyst Sn, and 20.5 kg of transport agent I in a ratio of 100:10:5. Preheat the red phosphorus, iodine, and tin in the transport device to 600°C, 60°C, and 250°C, respectively.

[0083] 2) Keep the heating device closed, turn on the booster control switch, and regulate the pressure in the reaction system. The temperature of the raw material zone of the reaction system is 25°C (room temperature without heating), the temperature of the intermediate formation zone of the reaction system is 25°C (room temperature without heating), and the temperature of the crystal nucleation and growth zone of the reaction system is 25°C (room temperature without heating).

[0084] 3) After the pipeline is completely preheated, open the pipeline valve and flow red phosphorus and iodine into the reaction system in the order of flow. At the same time, start the supercharger to slowly increase the pressure, so that red phosphorus and iodine are slowly transported in the supercharged zone (the supercharged zone is set before the raw material zone to increase the pressure in advance rather than during the reaction, which is easier to control and stabilize). The pressure gradually increases to 90Mpa. At the same time, open the tin feeding device and pipeline valve to flow into the reaction system and start to transfer to the intermediate. Finally, when the pressure in the supercharged zone reaches 90MPa, the crystal begins to nucleate and grow.

[0085] Control the valve switch of the pipeline channel to open and close the pipeline;

[0086] After the reaction is completed, open the valve of the filtration system and the valve switch of the phosphine collection system to allow the phosphine gas to flow to the collection system and release the pressure at the same time. After the pressure is completely released, close the valve, remove the pipe flange, and use the sampler to take out the sample to finally obtain the black phosphorus crystal block.

[0087] Example 3

[0088] Black phosphorus crystals were prepared using the method for preparing high-stability two-dimensional black phosphorus described in Example 1, with the following specific steps:

[0089] 1) Under a protective gas atmosphere, weigh 1 kg of red phosphorus, 100 g of catalyst Sn, and 250 g of transport agent I in a ratio of 100:10:5. Preheat the red phosphorus, iodine, and tin in the transport device to 600°C, 60°C, and 250°C, respectively.

[0090] 2) Turn on the heating device and the booster control switch respectively, and adjust the temperature and pressure in the reaction system respectively. The temperature of the raw material zone of the reaction system is 520℃, the temperature of the intermediate formation zone of the reaction system is 500℃, and the temperature of the crystal nucleation and growth zone of the reaction system is 480℃.

[0091] 3) After the preheating pipeline is completely opened, the pipeline valve is opened, and red phosphorus and iodine are flowed into the flow reaction system in the order of red phosphorus and iodine, and the supercharger is started to slowly increase the pressure at the same time, so that red phosphorus and iodine are slowly transported under the condition that the pressure in the supercharging zone is gradually increased from 0.5 MPa / min to 5 MPa; then the tin feeding device and the pipeline valve are opened to flow into the reaction system and start to transfer to the intermediate formation zone. Finally, the crystal begins to nucleate and grow in the crystal nucleation and growth zone when the supercharging pressure reaches 5 MPa.

[0092] To achieve directional flow of gaseous red phosphorus combined with iodine vapor, the pressure required to completely volatilize a unit amount of iodine must be determined. This directional flow of the gas phase is achieved through the complete volatilization of both the gaseous red phosphorus and the iodine. Multichannel piping is used to control gaseous red phosphorus, similar to microchannel reactor piping.

[0093] The temperature raising procedure in the reaction system is as follows: the raw material zone is heated to 520°C over 30 minutes, the intermediate formation zone is heated to 500°C, and the crystal nucleation and growth zone is heated to 480°C. After 24 hours of heat preservation, the system is naturally cooled to room temperature. The valve is heated according to the same procedure.

[0094] Turn on the temperature probe and temperature control cabinet to adjust the reaction temperature program respectively, and control the opening and closing of the valve and pressure relief valve;

[0095] Control the valve switch of the pipeline channel to open and close the pipeline;

[0096] After the reaction is complete, the valves in the filtration system and the phosphine collection system are opened to allow the phosphine gas to flow to the collection system and release the pressure. After the pressure is completely released, the valves are closed, the pipe flange is removed, and a sample is taken using a sampler, ultimately obtaining a two-dimensionally stable black phosphorus crystal block. The yield of black phosphorus crystals is 97.1%, and the byproducts are mainly Sn3P4 and a small amount of unconverted red phosphorus.

[0097] Example 3

[0098] Black phosphorus crystals were prepared using the method for preparing high-stability two-dimensional black phosphorus described in Example 1, with the following specific steps:

[0099] 1) Under a protective gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of catalyst Sn, and 20.5 kg of transport agent I in a ratio of 100:10:5. Preheat the red phosphorus, iodine, and tin in the transport device to 600°C, 60°C, and 250°C, respectively.

[0100] 2) Turn on the heating device control switch, keep the supercharger in the closed state, and regulate the temperature in the reaction system. The temperature of the raw material zone of the reaction system is 600°C, the temperature of the intermediate formation zone of the reaction system is 560°C, and the temperature of the crystal nucleation and growth zone of the reaction system is 500°C.

[0101] 3) After the pipeline is completely preheated, open the pipeline valve and flow red phosphorus and iodine into the reaction system in sequence without increasing the pressure, so that red phosphorus and iodine are slowly transported under the condition of rising temperature; at the same time, open the tin feeding device and pipeline valve to flow into the reaction system to start transferring to the intermediate formation, and finally when the temperature reaches the set temperature, the crystal begins to nucleate and grow.

[0102] The temperature raising procedure in the reaction system is as follows: the raw material zone is heated to 600°C over 30 minutes, the intermediate formation zone is heated to 560°C, and the crystal nucleation and growth zone is heated to 480°C. After 24 hours of heat preservation, the system is naturally cooled to room temperature. The valve is heated according to the same procedure.

[0103] Turn on the temperature probe and temperature control cabinet to adjust the reaction temperature program respectively, and control the opening and closing of the valve and pressure relief valve;

[0104] Control the valve switch of the pipeline channel to open and close the pipeline;

[0105] After the reaction is complete, the valves in the filtration system and the phosphine collection system are opened to allow the phosphine gas to flow to the collection system while simultaneously releasing pressure. After complete pressure relief, the valves are closed, the pipe flange is removed, and a sample is taken out using a sampler, ultimately yielding a two-dimensionally stable black phosphorus crystal block. The resulting black phosphorus crystal yield is 60.1%, with the majority of byproducts being Sn3P4, PI-Sn that has not been fully converted to black phosphorus, and unconverted red phosphorus.

[0106] Figure 1 Schematic diagram of the reaction system for preparing black phosphorus using a method for preparing highly stable two-dimensional black phosphorus.

[0107] Figure 2 This is a photo of the black phosphorus crystal obtained in Example 1. It can be seen from the figure that the crystal quality is high, but the surface

[0108] There is obviously a small layer of unreacted red phosphorus that has not been converted and other by-products and impurities attached to the surface.

[0109] Figure 3 This is a real picture of the black phosphorus crystal obtained in Example 2. It can be seen from the figure that the crystal quality is high.

[0110] There is a small amount of red phosphorus on the surface that has not been completely converted into black phosphorus and there are no obvious by-products or impurities attached.

[0111] Figure 4This is a real picture of the black phosphorus crystal obtained in Example 3. It can be seen from the figure that the crystal quality is high.

[0112] There is a small amount of unreacted red phosphorus on the surface, but there are no obvious by-products or impurities attached.

[0113] Figure 5 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 1. As can be seen from the figure, the sample mainly exhibits typical characteristic peaks of black phosphorus, and there are relatively low impurity peaks. This shows that the low temperature and high pressure method can be used to prepare a good black phosphorus crystal form with high purity. The three strong characteristic peaks correspond to the (020), (040) and (060) of the black phosphorus crystal.

[0114] Figure 6 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 2. As can be seen from the figure, the sample mainly exhibits typical characteristic peaks of black phosphorus, and no other impurity peaks appear. This shows that the use of appropriate temperature and pressure can produce a good black phosphorus crystal form with high purity. The three strong characteristic peaks correspond to the (020), (040) and (060) of the black phosphorus crystal.

[0115] Figure 7 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 3. As can be seen from the figure, the sample mainly exhibits typical characteristic peaks of black phosphorus, and a few impurity peaks appear. This shows that the high temperature and low pressure method can be used to prepare a good black phosphorus crystal form with high purity. The three strong characteristic peaks correspond to the (020), (040) and (060) of the black phosphorus crystal.

[0116] Figure 8 、 Figure 9 and Figure 10 The Raman images of black phosphorus prepared in Example 1, Example 2 and Example 3 respectively show the presence of the A1g peak caused by the out-of-plane vibration of phosphorus atoms and the B2g and A2g peaks caused by the in-plane vibration of phosphorus atoms, indicating that black phosphorus crystals with relatively high purity are prepared.

[0117] Figure 11 、 Figure 12 and Figure 13 SEM images of black phosphorus prepared in Examples 1, 2, and 3 are shown. The stacked black phosphorus crystals are clearly visible, demonstrating the high quality of the prepared black phosphorus crystals. Visual inspection also reveals no crystalline residue other than black phosphorus, demonstrating that the crystals are both pure and highly crystalline.

Claims

1. A method for preparing highly stable two-dimensional black phosphorus, characterized in that: The following steps are involved: S1) Under a protective gas atmosphere, red phosphorus, tin and iodine are activated and preheated respectively; S2) after preheating and activating red phosphorus and iodine, the gaseous red phosphorus and gaseous iodine are directed to flow from the raw material area to the intermediate formation area in the reaction system; the gaseous red phosphorus and iodine are flowed through the liquid-phase catalyst and continuously converted in the intermediate formation area of ​​the reaction system and directed to flow to the crystal nucleation and growth area; finally, the intermediate is gradually converted into black phosphorus crystals under cooling conditions, uniformly nucleated and grown, and iodine vapor and liquid-phase catalyst are precipitated; By regulating the temperature of red phosphorus transported into the reaction system to 590-650°C, it is converted into a gas phase and transferred to the reaction system; by regulating the temperature of iodine transported into the reaction system to 45-80°C, it is converted into a gas phase and transferred to the reaction system; by regulating the temperature of tin transported into the reaction system to 235-300°C, it is converted into a liquid phase and transferred to the reaction system; S3) The reaction system is subjected to heat treatment by a heating device for continuous preparation of black phosphorus crystals, and two-dimensional black phosphorus is obtained after the crystals are fully grown.

2. The method for preparing high-stability two-dimensional black phosphorus according to claim 1, characterized in that: The raw material delivery ratio is red phosphorus: tin: iodine = 100:10:3~100:10:

7.

3. The method for preparing high-stability two-dimensional black phosphorus according to claim 1, characterized in that: By controlling the temperature of the raw material zone in the reaction system to 600-650°C and the temperature of the intermediate formation zone in the reaction system to 550-580°C, gaseous red phosphorus and iodine flow through the liquid catalyst and are continuously converted in the intermediate formation zone of the reaction system and finally flow directionally to the crystal nucleation and growth zone; by regulating the temperature of the crystal nucleation and growth zone in the reaction system to 480-530°C.

4. The method for preparing high-stability two-dimensional black phosphorus according to claim 2, characterized in that: The order of conveying raw materials is as follows: first convey the phosphorus source, then convey the iodine source, and finally convey the tin source.

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