Preparation method of germanium phosphide nanosheets and application of germanium phosphide thin films

Abstract

The present invention provides a method for preparing germanium phosphide nanosheets, belonging to the technical field of electrode material preparation. The method comprises the steps of: 1) pre-compacting a mixed powder of red phosphorus powder and germanium powder to obtain a pre-compacted body; 2) sintering the pre-compacted body prepared in step 1) at high temperature and high pressure to obtain bulk germanium phosphide; 3) placing the bulk germanium phosphide prepared in step 2) as an electrode in an electrolytic cell; 4) applying a voltage or current to the electrode in step 3) to intercalate and dissociate the germanium phosphide; and 5) centrifuging the electrolyte after electrochemical dissociation in step 4) and collecting the supernatant to obtain germanium phosphide nanosheets. The present invention utilizes high-temperature and high-pressure technology combined with electrochemical dissociation technology to produce a large number of high-purity, micron-sized germanium phosphide nanosheets.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode material preparation, and in particular to a method for preparing germanium phosphide nanosheets and the application of germanium phosphide thin films prepared from the germanium phosphide nanosheets prepared by the preparation method in electrodes of supercapacitor energy storage devices. Background Art

[0002] In recent years, two-dimensional GeP3 crystals have attracted widespread attention in the field of materials science. Related research has progressed rapidly and has shown attractive prospects in the fields of energy storage, gas sensing and catalysis. GeP3 crystals have an arsenic honeycomb structure, and the atomic layers are stacked in an ABC manner by van der Waals forces. Its structure is similar to that of orthorhombic black phosphorus under high pressure. Each Ge atom in the GeP3 crystal layer is bonded to three P atoms. The introduction of excess valence electrons of Ge atoms greatly improves the conductivity of the system. At a temperature of 25K, the conductivity of GeP3 is 1×10 6 Sm -1 , nearly a million times higher than black phosphorus. According to bond energy calculations, the P-Ge bond (bond energy: ~-5.3540eV) is weaker than the PP bond (bond energy: ~-7.0235eV), indicating that GeP3 crystals have a lower bulk modulus than black phosphorus and GeP5, and can more effectively alleviate the structural deformation caused by the charge and discharge process, thereby enhancing the cycling stability of the electrode material. In addition, weak interlayer interactions help two-dimensional materials to be obtained by mechanical or liquid phase exfoliation of the corresponding layered bulk materials.

[0003] In the field of electrochemical energy storage, GeP3 crystals, when used as electrode materials for lithium / sodium ion batteries, exhibit excellent energy storage performance due to their metallic conductivity and dual-active energy storage components. Theoretical calculations show that the maximum theoretical capacity of a single-layer GeP3 is 648 mAhg -1 When combined with C material, it has an ultra-high reversible capacity of 1109 mAh g -1 , and exhibits excellent cycle characteristics and high rate capability.

[0004] Currently, the main methods for synthesizing GeP3 compounds are high-temperature and high-pressure technology and high-energy ball milling. Although high-temperature and high-pressure technology alone can produce high-crystal quality, millimeter-scale germanium-phosphorus compounds, there is the problem of multiphase coexistence. In recent years, multiple research groups at home and abroad have successfully prepared GeP3 nanopowders with uniform physical phases by using solid-phase reactions during high-energy ball milling. However, during the high-energy ball milling process, repeated collisions can cause the sample lattice to relax, easily destroying the crystal structure, and making it impossible to obtain high-quality, large-scale GeP3 single crystals. Since most existing two-dimensional materials are separated from bulk layered materials, the quality and scale of single crystals of bulk layered materials are important guarantees for the preparation of two-dimensional materials. Currently, due to the lack of high-quality, large-scale GeP3 bulk materials, two-dimensional GeP3 materials are difficult to obtain using mechanical or liquid-phase exfoliation methods, which greatly hinders the research progress on the application of two-dimensional GeP3 crystals. Summary of the Invention

[0005] In view of this, in order to solve the technical problems of low purity and small grain size of bulk germanium phosphide materials prepared by existing technology, on the one hand, the present invention provides a method for preparing germanium phosphide nanosheets, which utilizes high temperature and high pressure technology combined with electrochemical dissociation technology to prepare a large number of high-purity germanium phosphide nanosheets with centimeter-level single crystal phase.

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

[0007] A method for preparing germanium triphosphide nanosheets comprises the following steps:

[0008] Step 1) pre-pressing a mixed powder formed by red phosphorus powder and germanium powder to obtain a pre-pressed body;

[0009] Step 2) sintering the pre-pressed body prepared in step 1) at high temperature and high pressure to obtain bulk germanium triphosphide;

[0010] Step 3), the bulk germanium phosphide prepared in step 2) is used as an electrode and placed in an electrolytic cell;

[0011] Step 4), applying voltage or current to the electrode in step 3) to perform intercalation dissociation of germanium triphosphide;

[0012] Step 5) centrifuging the electrolyte after electrochemical dissociation in step 4) and collecting the supernatant to obtain germanium triphosphide nanosheets.

[0013] Preferably, in step 2), the high temperature and high pressure sintering conditions are: high pressure of 2 GPa, and sintering temperature of 600-1000°C.

[0014] Preferably, in step 4), the applied voltage is 3-10 V or the applied current is 0.1-3 mA, and the treatment time is 0.2-1 h.

[0015] Preferably, in step 1), the molar ratio of germanium powder to red phosphorus powder is 1:3 to 3.2.

[0016] Preferably, in step 3), bulk germanium triphosphide is used as an electrode, a platinum sheet is used as a counter electrode, and an alkaline solution is used as an electrolyte to form an electrolytic cell.

[0017] Preferably, the concentration of the electrolyte is 0.3-1M.

[0018] Preferably, after step 4) and before step 5), the method further comprises:

[0019] Step 41) dispersing the electrolyte after electrochemical dissociation in step 4) into an organic solvent.

[0020] Preferably, the organic solvent is one or two of dimethyl sulfoxide, N-methylpyrrolidone, N-dimethylformamide, and dimethylacetamide.

[0021] Preferably, in step 1), the red phosphorus powder and the germanium powder are both ground powders.

[0022] On the other hand, the present invention also provides the use of a germanium phosphide thin film prepared from germanium phosphide nanosheets prepared by the above-mentioned method for preparing germanium phosphide nanosheets in electrodes of supercapacitor energy storage devices.

[0023] The method for preparing germanium phosphide nanosheets provided by the present invention utilizes high-temperature and high-pressure technology combined with electrochemical dissociation technology to produce a large number of high-purity, micron-sized germanium phosphide nanosheets. Compared with existing technologies, it has the following advantages:

[0024] (1) This invention utilizes a high-temperature, high-pressure sintering method to produce centimeter-scale single crystals of Germanium Phosphide (GP). Subsequent electrochemical dissociation technology yields two-dimensional GP nanosheets with an average thickness of 4.5 nanometers and a maximum radial dimension of 0.8 micrometers. This high-temperature, high-pressure technique combined with electrochemical dissociation technology can produce large-scale, high-quality two-dimensional GP nanosheets.

[0025] (2) The present invention overcomes the technical defect that it is difficult to prepare high-purity, large-size germanium phosphide single crystals, and realizes the preparation of high-purity germanium phosphide single crystals with a crystal size of up to 0.4 cm, providing raw materials for subsequent research on the physical properties of germanium phosphide crystals.

[0026] (3) The present invention adopts high temperature and high pressure technology to realize the preparation of germanium triphosphide single crystal. Compared with the traditional gas phase method and ball milling method, its production cycle is short, the crystal size is large, and the crystal purity is high.

[0027] (4) The present invention can prepare germanium phosphide crystals in large quantities. By expanding the high-temperature and high-pressure cavity, the preparation of gram-level germanium phosphide crystals can be achieved at one time, which is of great significance for the subsequent research on germanium phosphide crystals.

[0028] (5) The present invention uses high-quality, large-sized germanium phosphide crystals prepared at high temperature and high pressure as a precursor for electrochemical dissociation, which can ensure the preparation of micron-level two-dimensional germanium phosphide nanosheets.

[0029] (6) The two-dimensional germanium phosphide nanosheet electrode material prepared based on the present invention has high conductivity and high ion mobility, and thus has excellent energy storage performance, and its volume capacitance can reach 46.67F cm -3 , which is higher than the volume capacitance of black phosphorus nanosheets (17.8F cm -3 ), and the two-dimensional germanium phosphide nanosheet supercapacitor can withstand 1000V s -1 The voltage sweep rate is higher than that of black phosphorus supercapacitors (which can only withstand 10V s -1 ), showing excellent fast charge and discharge capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 XRD patterns of samples obtained when the sintering temperatures are 600°C, 800°C and 1000°C in Examples 1-3, respectively;

[0031] Figure 2 The optical photographs and scanning electron microscope images of the high-quality, large-sized germanium triphosphide crystal obtained in Example 1 are shown; (a) is an optical photograph of the high-quality, large-sized germanium triphosphide crystal obtained; (b) is a scanning electron microscope image;

[0032] Figure 3 Atomic force microscope image (a) and thickness (b) and radial scale statistics (c) of germanium phosphide nanosheets dissociated using electrochemical dissociation technology in Example 5;

[0033] Figure 4 Atomic force microscopy images (a), (d), (g), thickness (b), (e), (h), and radial scale statistics (c), (f), (i) of germanium triphosphide nanosheets dissociated using N-methylpyrrolidone solvent acetone and ethanol solution in Example 7;

[0034] Figure 5 (a) transmission image, (b) high-resolution image, and (c) diffraction spot image of the two-dimensional germanium triphosphide nanosheet in Example 5;

[0035] Figure 6 This is a graph showing the change in volume capacitance of the two-dimensional germanium triphosphide nanosheets as a function of scan rate in Example 5. DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing germanium triphosphide nanosheets, comprising the following steps:

[0037] Step 1) Pre-compacting a mixed powder of red phosphorus powder and germanium powder to obtain a pre-compacted body. In this step, both the red phosphorus powder and the germanium powder are ground. Specifically, the red phosphorus powder and the germanium powder can be manually ground in a vacuum glove box. The ground particles are preferably in the micrometer range.

[0038] This step can be accomplished using any conventional method. For example, a manually ground mixture of red phosphorus and germanium powder is placed in a steel mold and pressed into a block using a tablet press. The pressing pressure used during the slab-forming process can be any pressure sufficient to compact the manually ground powder into a dense block; considering factors such as cost, a pressure of 1-20 MPa is typically sufficient. The pre-pressed block is preferably a cylinder with a diameter of 14 mm.

[0039] In this step, the molar ratio of germanium powder to red phosphorus powder is preferably 1:3 to 3.2.

[0040] Step 2) Fill the pre-pressed body prepared in step 1) into a high-temperature and high-pressure reaction chamber, and perform high-temperature and high-pressure sintering to obtain bulk germanium triphosphide. In this step, the high-temperature and high-pressure sintering conditions are: the high pressure is 2Gpa, and the sintering temperature is 600-1000°C. The sintering temperature is a key factor affecting the purity and grain size of bulk germanium triphosphide; under a sintering pressure of 2GPa, the optimal temperature for obtaining high-purity, large-sized germanium triphosphide is 600°C; and a slow cooling method is adopted. As the temperature increases, germanium triphosphide decomposes into black phosphorus, GeP and GeP5, while as the temperature decreases, the germanium triphosphide grains cannot grow. In this step, in order to increase the size of the germanium triphosphide single crystal, the cooling rate can be controlled to 1-50°C / min.

[0041] Step 3) The bulk germanium phosphide prepared in step 2) is placed in an electrolytic cell as an electrode. In this step, the electrolytic cell preferably comprises bulk germanium phosphide as the electrode, a platinum sheet as the counter electrode, and an alkaline solution as the electrolyte. The concentration of the electrolyte is preferably 0.3-1M.

[0042] Step 4) applies voltage or current to the electrodes of step 3) to perform intercalation dissociation on germanium phosphide. This step is the electrochemical dissociation step, in which the applied voltage is 3-10V or the current is 0.1-3mA, and the processing time is 0.2-1h. The choice of electrolyte mainly depends on whether the ions in the solution can be inserted into the interlayer of germanium phosphide and cause it to expand to achieve dissociation. The choice of voltage is determined by the thickness and radial size of the final product, two-dimensional germanium phosphide nanosheets. When a voltage of 3V is used, the average thickness of the prepared two-dimensional germanium phosphide nanosheets is 4.5 nanometers, and the maximum radial dimension can reach 0.8 microns; when a voltage of 5V is used, the thickness of the prepared two-dimensional germanium phosphide nanosheets is mostly above 10 nanometers, and the radial size is in the range of hundreds of nanometers.

[0043] Step 5) high-speed centrifugation is performed on the electrolyte after electrochemical dissociation in step 4), and the supernatant is collected to screen out germanium phosphide nanosheets with uniform size, which are two-dimensional germanium phosphide nanosheets.

[0044] Step 6) Prepare a germanium phosphide thin film using vacuum filtration technology, and apply it to a two-dimensional germanium phosphide nanosheet electrode of a supercapacitor energy storage device.

[0045] In the present invention, after step 4) and before step 5), the method further comprises:

[0046] Step 41) dispersing the electrolyte after electrochemical dissociation in step 4) into an organic solvent.

[0047] The organic solvent is preferably one or two of dimethyl sulfoxide, N-methylpyrrolidone, N-dimethylformamide, and dimethylacetamide.

[0048] In the present invention, after step 4) and before step 41), the method further includes filtering and washing the germanium triphosphide electrolyte after electrochemical dissociation in step 4).

[0049] In another aspect, the present invention also provides the use of a germanium phosphide thin film prepared from germanium phosphide nanosheets prepared using the above-mentioned method for preparing germanium phosphide nanosheets in electrodes for supercapacitor energy storage devices. Specifically, the present invention first uses the method for preparing germanium phosphide nanosheets to prepare two-dimensional germanium phosphide nanosheets, then uses vacuum filtration technology to convert the two-dimensional germanium phosphide nanosheets into a germanium phosphide thin film, and then uses the germanium phosphide thin film in electrodes for supercapacitor energy storage devices.

[0050] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods.

[0051] Example 1

[0052] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 60 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0053] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0054] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 600℃, and the sintering temperature is maintained at 600℃ for 30 minutes; a dense block is obtained.

[0055] (4) Bulk germanium phosphide synthesized under high pressure is used as an electrode.

[0056] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed for 1 hour at a voltage of 5 V. Germanium phosphide nanosheets were thus obtained.

[0057] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets.

[0058] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0059] Figure 2 (a) is an optical image of a high-quality, large-size germanium triphosphide crystal obtained in Example 1. Figure 2 (b) Scanning electron microscope image, from which a clear layered structure can be seen. The largest Germanium Phosphide flake is as high as 0.3 cm, which is much larger than the hundred-nanometer-level Germanium Phosphide particles prepared by ball milling.

[0060] Example 2

[0061] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 60 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0062] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0063] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 800℃, and the sintering temperature is maintained at 800℃ for 30 minutes; a dense block is obtained.

[0064] (4) Bulk germanium phosphide synthesized under high pressure is used as an electrode.

[0065] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed for 1 hour at a voltage of 5 V. Germanium phosphide nanosheets were thus obtained.

[0066] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets.

[0067] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0068] Example 3

[0069] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 60 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0070] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0071] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 1000℃, and the sintering temperature is maintained at 1000℃ for 30 minutes; a dense block is obtained.

[0072] (4) Bulk germanium phosphide synthesized under high pressure is used as an electrode.

[0073] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed for 1 hour at a voltage of 5 V. Germanium phosphide nanosheets were thus obtained.

[0074] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets.

[0075] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0076] The XRD patterns of the samples sintered at 600℃, 800℃ and 1000℃ are shown in Figure 2. Figure 1 At a sintering temperature of 600°C, the sample is pure germanium triphosphide. When the temperature rises to 800°C, a small amount of germanium phosphorus precipitates in the sample. When the temperature rises to 1000°C, a large amount of germanium phosphide (GeP) and black phosphorus (BP) appear in the sample. Therefore, we subsequently selected the sample synthesized at 2GPa and 600°C for electrolysis.

[0077] Example 4

[0078] (1) Germanium powder and red phosphorus powder were used as raw materials and ground in a glove box. The molar ratio of germanium powder to red phosphorus powder was 1:3, and the grinding time was 60 min.

[0079] (2) The mixed powder was placed in a steel mold and pressed into a 14 mm cylinder using a tablet press; the pressure used in the pressing process was 10 MPa.

[0080] (3) The pressed cylinder is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powder of germanium powder and red phosphorus powder is 1:3, the sintering pressure is 2GPa, the sintering temperature is 600℃, the heating rate is controlled at 10℃ / min, and the sintering time is 30min.

[0081] (4) Bulk germanium phosphide synthesized under high pressure was used as the electrode, platinum sheet was used as the counter electrode, and sodium hydroxide with a concentration of 0.6 M was used as the electrolyte.

[0082] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed for 1 hour at a voltage of 3 V. Germanium phosphide nanosheets were thus obtained.

[0083] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets of uniform size.

[0084] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous filter membrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0085] Example 5

[0086] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 30 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0087] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0088] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 600℃, and the sintering temperature is maintained at 600℃ for 30 minutes; a dense block is obtained.

[0089] (4) Bulk germanium phosphide synthesized under high pressure is used as an electrode.

[0090] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed for 1 hour at a voltage of 5 V. Germanium phosphide nanosheets were thus obtained.

[0091] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets.

[0092] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0093] Figure 6 The volume capacitance of the two-dimensional germanium phosphide nanosheet prepared under the synthesis conditions of Example 5 is plotted as a function of the scan rate. -1 At the scan rate, the volume capacitance of germanium triphosphide nanosheets is as high as 46.67F cm -3 , which is much higher than the volumetric capacitance of black phosphorus nanosheets and graphene (black phosphorus: 17.8Fcm -3 , graphene: 1F cm -3 Supercapacitors based on germanium phosphide nanosheets have excellent energy storage performance and fast charge and discharge capabilities, showing excellent commercial value.

[0094] The atomic force microscope image of the electrochemically dissociated germanium triphosphide nanosheets under the conditions of Example 5 is as follows: Figure 3 In (a), the thicknesses of the two nanosheets are 4.4 nm and 3.9 nm respectively. The thicknesses and radial dimensions of 100 nanosheets are calculated as follows: Figure 4 In (b) and (c), the average thickness of the nanosheets is 4.5 nm and the average radial size is 0.8 μm, indicating that two-dimensional germanium triphosphide nanosheets can be effectively obtained by electrochemical dissociation technology.

[0095] Transmission image of two-dimensional germanium triphosphide nanosheets dissociated using electrochemical dissociation technology, such as Figure 5 From the image (a), we can clearly see the nanosheets. The corresponding high-resolution image (b) and diffraction spot image (c) Figure 5 Clear interference fringes can be seen in (b), and the lattice spacing from (c) corresponds to the (110), (210), and (120) planes respectively.

[0096] Example 6

[0097] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 60 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0098] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0099] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 600℃, and the sintering temperature is maintained at 600℃ for 30 minutes; a dense block is obtained.

[0100] (4) Bulk germanium phosphide synthesized under high pressure is used as an electrode.

[0101] (5) Germanium phosphide was placed in 40 ml of electrolyte and electrolyzed at 10 V for 1 hour. Germanium phosphide nanosheets were thus obtained.

[0102] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional germanium triphosphide nanosheets.

[0103] (7) The supernatant after centrifugation was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional germanium triphosphide nanosheet film.

[0104] Example 7

[0105] (1) Using germanium powder and red phosphorus powder as raw materials, grind them in a glove box. Preferably, the molar ratio of germanium powder to red phosphorus powder is 1:3. Preferably, the grinding time is 60 minutes to fully grind and evenly mix the germanium powder and red phosphorus powder.

[0106] (2) The mixed powder was placed in a steel mold and pressed into a block using a tablet press; the pressure used in the pressing process was 10 MPa.

[0107] (3) The pressed block is sintered at high temperature and high pressure: the molar ratio of the sintered mixed powders of germanium powder and red phosphorus powder is 1:3, the medium sintering pressure is 2GPa, the heating rate is controlled to be 10℃ / min, and the heating is stopped when the sintering temperature reaches 600℃, and the sintering temperature is maintained at 600℃ for 30 minutes; a dense block is obtained.

[0108] (4) The bulk tin phosphide synthesized under high pressure was ground into powder in a glove box.

[0109] (5) Tin phosphide was placed in 20 ml of N-methylpyrrolidone, ethanol or acetone organic solvent and subjected to ultrasonic liquid phase dissociation for 5 hours to obtain tin phosphide nanosheets.

[0110] (6) The stripped solution was subjected to high-speed centrifugation at a centrifugal rate of 5000 rpm for 30 minutes to screen out two-dimensional tin triphosphide nanosheets.

[0111] (7) The mixed suspension was vacuum filtered using an organic microporous micromembrane with a diameter of 0.2 μm, washed with deionized water, and then vacuum dried to obtain a two-dimensional tin triphosphide nanosheet film.

[0112] Atomic force microscopy images of germanium phosphide nanosheets dissociated using liquid phase dissociation and N-methylpyrrolidone solvent, acetone and ethanol solution respectively. Figure 4 In the figure, (a), (b) and (c) are atomic force microscopy images and thickness and radial scale statistics in N-methylpyrrolidone solvent solution; (d), (e) and (f) are atomic force microscopy images and thickness and radial scale statistics in acetone solvent solution; (g), (h) and (i) are atomic force microscopy images and thickness and radial scale statistics in ethanol solution; the thickness of the nanosheets dissociated in the three solutions is above 9 nm, and the radial size is relatively small.

Claims

1. A method for preparing germanium triphosphide nanosheets, characterized in that: The steps include: Step 1) pre-pressing a mixed powder formed by red phosphorus powder and germanium powder to obtain a pre-pressed body; Step 2) sintering the pre-pressed body prepared in step 1) at high temperature and high pressure to obtain bulk germanium triphosphide; Step 3), the bulk germanium phosphide prepared in step 2) is used as an electrode and placed in an electrolytic cell; Step 4), applying voltage or current to the electrode in step 3) to perform intercalation dissociation of germanium triphosphide; Step 5), centrifuging the electrolyte after electrochemical dissociation in step 4), collecting the supernatant to obtain germanium triphosphide nanosheets; In step 2), the high temperature and high pressure sintering conditions are: high pressure of 2 GPa, and sintering temperature of 600°C.

2. The method for preparing germanium triphosphide nanosheets according to claim 1, wherein: In step 4), the applied voltage is 3-10 V or the applied current is 0.1-3 mA, and the treatment time is 0.2-1 h.

3. The method for preparing germanium triphosphide nanosheets according to claim 1, wherein: In step 1), the molar ratio of germanium powder to red phosphorus powder is 1:3 to 3.

2.

4. The method for preparing germanium triphosphide nanosheets according to claim 1, wherein: In step 3), bulk germanium triphosphide is used as an electrode, a platinum sheet is used as a counter electrode, and an alkaline solution is used as an electrolyte to form an electrolytic cell.

5. The method for preparing germanium triphosphide nanosheets according to claim 4, wherein: The concentration of the electrolyte is 0.3-1M.

6. The method for preparing germanium triphosphide nanosheets according to claim 1, wherein: After step 4) and before step 5), the method further includes: Step 41) dispersing the electrolyte after electrochemical dissociation in step 4) into an organic solvent.

7. The method for preparing germanium triphosphide nanosheets according to claim 6, wherein: The organic solvent is one or two of dimethyl sulfoxide, N-methylpyrrolidone, N-dimethylformamide and dimethylacetamide.

8. The method for preparing germanium triphosphide nanosheets according to any one of claims 1 to 7, characterized in that: In step 1), the red phosphorus powder and the germanium powder are both ground into powders with a particle size of micrometer level.

9. Use of a germanium phosphide thin film prepared from germanium phosphide nanosheets prepared by the method for preparing germanium phosphide nanosheets according to any one of claims 1 to 8 in electrodes for supercapacitor energy storage devices.

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