A tungsten phosphide nanoparticle-loaded nitrogen-phosphorus co-doped carbon nanosheet composite material, a preparation method therefor and applications thereof

Abstract

The application provides a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles and a preparation method and application thereof. The preparation method comprises the following steps: (1) adding phytic acid or sodium phytate and a tungsten source into deionized water, stirring to dissolve them at room temperature; then adding a nitrogen-containing material, continuing to stir to uniformly disperse them, to obtain a dispersion liquid; (2) drying the obtained dispersion liquid to obtain a precursor; calcining the obtained precursor to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles. The composite material can prevent the agglomeration of tungsten phosphide particles, improve the active sites and conductivity of the material, and is effectively applied in lithium-sulfur batteries, and exhibits excellent catalytic performance. The preparation process is simple, the cost is low, the production efficiency is greatly improved, the needs of industrial production can be better met, large-scale production can be realized, and the application prospect is excellent.

Description

Technical Field

[0001] This invention relates to a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles, its preparation method and application, belonging to the fields of new energy and nanomaterials technology. Background Technology

[0002] In recent years, with the increasingly severe depletion of fossil fuels, the global energy demand and environmental crisis have intensified, stimulating researchers' interest in various advanced technologies. On the one hand, researchers are striving to find green and renewable energy sources to replace traditional fossil fuels, with hydrogen, as a clean and renewable high-quality energy source, receiving widespread attention. On the other hand, researchers are dedicated to developing high-energy-density, low-cost, and long-life energy storage systems to store solar, wind, geothermal, and tidal energy, and to meet the needs of advanced electric devices such as laptops, mobile phones, and electric vehicles. Lithium-sulfur batteries, for example, boast an energy density as high as 2552 Wh / kg. -1 Or 2800Wh L -1 This figure is more than five times the energy density of commercial lithium-ion batteries. Furthermore, the abundance, environmental friendliness, and low cost of sulfur in the Earth's crust make Li-S batteries a promising low-cost battery technology for widespread application.

[0003] The rapid capacity decay problem caused by the severe "shuttle effect" of lithium polysulfides in lithium-sulfur batteries is considered to stem from the slow conversion process between soluble long-chain lithium polysulfides and insoluble discharge products Li₂S during charging and discharging. Therefore, researchers have designed appropriate catalytic materials to promote the conversion between lithium polysulfides and Li₂S, which is considered a fundamental way to completely overcome the "shuttle effect" and maximize the energy output of lithium-sulfur batteries. For example, Chinese patent document CN110504414A provides a defect metal oxide / porous carbon nanomaterial composite material, which includes nitrogen-sulfur dual-doped porous carbon nanomaterials and oxygen-deficient metal oxides supported on these porous carbon nanomaterials. This improves the conductivity of lithium ions in the solid phase and the heterogeneous catalytic conversion ability of polysulfides, thereby achieving high efficiency utilization and high cycle life of the sulfur cathode when applied as an electrode, exhibiting superior electrochemical performance and enabling rapid charging and discharging.

[0004] Phosphates, as novel catalytic materials, possess metallic-level conductivity and suitable adsorption capacity for lithium polysulfides, attracting widespread attention from researchers. Tungsten phosphide, in particular, has demonstrated excellent performance in electrocatalytic hydrogen production and electrocatalytic water splitting, but its application in lithium-sulfur batteries is relatively rare. From a synthetic perspective, phosphide preparation typically involves multiple steps, including the preparation of precursors (oxides / hydroxides), and requires large amounts of phosphorus sources (such as sodium hypophosphite), hindering large-scale phosphide production. Furthermore, current phosphides suffer from issues such as easy aggregation and low catalytic activity. Therefore, how to fully expose the active sites of phosphides through structural design and achieve structural stability during the catalytic process is an urgent problem to be solved. This provides important reference value for developing low-cost, convenient, environmentally friendly, and highly catalytically active phosphide synthesis strategies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles, its preparation method, and its applications. Compared with existing technologies, this invention uses water as a dispersant at room temperature, employs phytic acid or sodium phytate as a phosphorus source and metal ion immobilizer, and fixes metal ions on a nitrogen-containing material template. During the subsequent calcination process, the metal ions are phosphated in situ by phytic acid or sodium phytate and dispersed on the nitrogen-phosphorus co-doped carbon nanosheets derived from the nitrogen-containing material template. The nitrogen-phosphorus co-doped carbon nanosheet composite material prepared by this invention has abundant active sites and high conductivity, exhibiting excellent lithium-sulfur battery performance.

[0006] Terminology Explanation:

[0007] Room temperature: as is known in the art, refers to 25±5℃.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0010] (1) Add phytic acid or sodium phytate and tungsten source to deionized water and stir at room temperature to dissolve them; then add nitrogen-containing material and continue stirring to disperse it evenly to obtain a dispersion.

[0011] (2) The dispersion obtained in step (1) is dried to obtain a precursor; the precursor is calcined to obtain a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0012] According to a preferred embodiment of the present invention, the tungsten source in step (1) is one or a combination of two or more of ammonium metatungstate, sodium tungstate, calcium tungstate, tungsten trioxide, tungsten pentachloride, and tungsten hexachloride; more preferably, ammonium metatungstate and / or sodium tungstate.

[0013] According to a preferred embodiment of the present invention, the molar ratio of phytic acid or sodium phytate to tungsten source in step (1) is 1-15:1; preferably, the molar ratio of phytic acid or sodium phytate to tungsten source is 3-9:1.

[0014] According to a preferred embodiment of the present invention, the mass ratio of the tungsten source to the volume of deionized water in step (1) is 0.001-0.05 g: 1 mL.

[0015] According to a preferred embodiment of the present invention, the nitrogen-containing material in step (1) is one or a combination of two or more of melamine, dicyandiamide, urea, pyrrole, and p-phenylenediamine; preferably, the nitrogen-containing material is melamine and / or dicyandiamide.

[0016] According to a preferred embodiment of the present invention, the mass ratio of the nitrogen-containing material to the tungsten source in step (1) is 10-60:1, and more preferably 12-50:1.

[0017] According to the present invention, in step (1), the stirring time after adding the nitrogen-containing material is 0.5-5 hours; preferably, the stirring time is 1-2 hours.

[0018] According to the present invention, the drying temperature in step (2) is preferably 60-100°C; preferably, the drying temperature is 80°C; the drying is performed until the moisture is completely evaporated.

[0019] According to a preferred embodiment of the present invention, the calcination in step (2) is carried out under an argon atmosphere; the calcination temperature is 500-1000℃, more preferably 600-800℃.

[0020] According to a preferred embodiment of the present invention, the calcination time in step (2) is 2-8 hours, and more preferably 4-6 hours.

[0021] The present invention also provides a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared by the above preparation method.

[0022] According to the present invention, the above-mentioned nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles is used in the cathode of lithium-sulfur batteries.

[0023] The present invention also provides a lithium-sulfur battery cathode material, wherein the lithium-sulfur battery cathode material comprises the above-mentioned nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0024] According to the present invention, the preparation method of the above-mentioned lithium-sulfur battery cathode material is prior art; preferably, the preparation method of the lithium-sulfur battery cathode material includes the following steps:

[0025] (1) The nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles was mixed and ground with sulfur powder at a mass ratio of 3:7. The resulting powder was placed in a tube furnace and calcined at 155°C for 12 hours under argon protection to obtain the sulfur-loaded composite material.

[0026] (2) The sulfur-loaded composite material obtained above is mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 7:2:1, and N-methylpyrrolidone is added and ball milled.

[0027] (3) The ball-milled slurry is coated onto aluminum foil and dried in a vacuum oven at 60°C for 12 hours to obtain the positive electrode material.

[0028] This invention also provides a lithium-sulfur battery, wherein the positive electrode material of the lithium-sulfur battery is the aforementioned lithium-sulfur battery positive electrode material. This invention does not impose special requirements on other components or assembly methods in the lithium-sulfur battery; battery components and assembly methods well-known to those skilled in the art can be used.

[0029] Preferably, the electrolyte of the lithium-sulfur battery is 1,3-dioxolane (DOL), ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene carbonate (DEC), diethyl carbonate (EMC), biphenyl (BP), vinylene carbonate (VC), ethylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), 1,4-butanesulfonyl lactone (BS), 1,3-(1-propene)sulfonyl lactone (PST), vinyl sulfite (ESI), or vinyl sulfate (ESA). The electrolyte is a mixture of one or more of cyclohexylbenzene (CHB), tert-butylbenzene (TBB), tert-amylbenzene (TPB), and succinic anhydride (SN) with a lithium salt; wherein the lithium salt is one or more of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium bis(SO2CF3)2, lithium bis(fluorosulfonamide) (LiFSI), lithium dioxoborate (LiBOB), and lithium trifluoromethanesulfonate (LiSO3CF3); and the concentration of the lithium salt in the electrolyte is 0.5-20 mol / L.

[0030] Preferably, the negative electrode of the lithium-sulfur battery is a lithium sheet, graphite, silicon carbide material, or lithium titanate; more preferably, it is a lithium sheet or graphite.

[0031] The technical features and beneficial effects of this invention are as follows:

[0032] 1. This invention uses nitrogen-containing materials as self-sacrificing templates and phytic acid or sodium phytate as phosphorus source and metal ion immobilizer to phosphate and disperse metal atoms in situ on the surface of carbon materials. This effectively prevents the agglomeration of the prepared phosphide, allowing the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this invention to expose more active sites and exhibit high catalytic performance. By designing this superior structure, more three-phase interfaces of active material / carbon substrate material / electrolyte can be provided, which can enhance the adsorption of lithium polysulfides and provide unobstructed electron / ion channels for the conversion of lithium polysulfides, thereby accelerating its conversion. Thanks to these structural and compositional advantages, the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles can effectively overcome the "shuttle effect," enabling the assembled lithium-sulfur battery to have excellent electrochemical performance.

[0033] 2. The preparation process of this invention is simple and low-cost, which greatly improves production efficiency and can better meet the needs of industrial production, realize large-scale production, and has great application prospects.

[0034] 3. The catalyst prepared by this invention has multiple active sites, high conductivity, and strong practicality, and can be effectively applied to high-performance lithium-sulfur batteries. Attached Figure Description

[0035] Figure 1 The image shows the XRD pattern of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1.

[0036] Figure 2 This is a transmission electron microscope (TEM) image of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1.

[0037] Figure 3 This is a mapping spectrum of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1.

[0038] Figure 4 The image shows the Raman spectrum of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1.

[0039] Figure 5 The image shows the TGA spectrum of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1.

[0040] Figure 6 This is a rate performance diagram of a lithium-sulfur battery assembled from nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1, with values ​​from right to left being 0.2C, 0.5C, 1C, 2C, 3C, 5C, and 6C.

[0041] Figure 7 The cycling performance of the lithium-sulfur battery assembled from the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 1 at a current of 0.5C is shown.

[0042] Figure 8 This is a scanning electron microscope image of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 2.

[0043] Figure 9 The cycling performance of the lithium-sulfur battery assembled from the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Example 4 is shown at a current of 0.5C.

[0044] Figure 10 This is a transmission electron microscope (TEM) image of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in Comparative Example 1.

[0045] Figure 11 This is a transmission electron microscope (TEM) image of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide prepared in Comparative Example 2. Detailed Implementation

[0046] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0048] As introduced in the background section, the preparation of tungsten phosphide catalytic materials in the prior art suffers from problems such as complex processes and material agglomeration. In order to solve the above problems, the present invention provides a strategy of template self-sacrifice combined with in-situ self-phosphorization to prepare nitrogen-phosphorus co-doped carbon nanosheet composite materials loaded with tungsten phosphide nanoparticles. The present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0051] Weigh 0.1g of sodium tungstate (Na2WO4) and dissolve it in 40mL of deionized water. Add 1mL of phytic acid and continue stirring for 10 minutes. Add 5g of melamine and stir for 1 hour. Dry the mixture in an oven at 80℃ to obtain the precursor. Place the precursor in a tube furnace and calcine it at 600℃ for 4 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0052] The XRD pattern of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this embodiment is as follows: Figure 1 As shown, from Figure 1 As can be seen, the XRD peaks of the sample correspond to those of the standard PDF card in WP, and there are no extraneous peaks present; its TEM image is shown below. Figure 2 As shown, from Figure 2 As can be seen, its microstructure consists of nanoparticles uniformly distributed on the surface of the nanosheets without aggregation, and the size of the nanoparticles is around 5 nm; its mapping spectrum is as follows. Figure 3 As shown, from Figure 3 As can be seen, the C, N, P and W elements are uniformly distributed in the obtained product, and the distribution of W element is consistent with the distribution of nanoparticles, thus indicating that the product obtained by the present invention is a composite material in which pure phase tungsten phosphide nanoparticles are uniformly loaded on nitrogen and phosphorus co-doped carbon nanosheets.

[0053] The Raman spectrum of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this embodiment is as follows: Figure 4 As shown, from Figure 4 As can be seen from this, the I of the sample D / I G The value of 1.03 indicates that the incorporation of nitrogen and phosphorus introduces defects into the carbon substrate.

[0054] The TGA spectrum of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this embodiment is as follows: Figure 5 As shown, from Figure 5 As can be seen, the mass ratio of WP in the sample is approximately 85.2%.

[0055] The nitrogen-phosphorus co-doped carbon nanosheet composite material with tungsten phosphide nanoparticles prepared in this embodiment was then loaded with sulfur and used as the positive electrode material for lithium-sulfur batteries. The specific steps are as follows:

[0056] (1) The nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles was ground with sulfur powder in an agate mortar for 30 minutes at a mass ratio of 3:7; the mixed powder was placed in a tube furnace and calcined at 155°C for 12 hours under argon protection to obtain the sulfur-loaded composite material.

[0057] (2) The sulfur-loaded composite material (0.1g) obtained above was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 7:2:1, and 1mL of N-methylpyrrolidone was added. The mixed material was placed in an agate ball mill jar and ball milled on a planetary ball mill for 2 hours.

[0058] (3) The mixed slurry is coated onto aluminum foil with a scraper and dried in a vacuum oven at 60°C for 12 hours to obtain the positive electrode material; then it is punched into a positive electrode sheet with a diameter of 12mm using a punching machine.

[0059] (4) Assemble the battery in a glove box protected by argon atmosphere. The assembly sequence is: positive electrode shell - positive electrode plate - separator - electrolyte - negative electrode plate - stainless steel gasket - spring plate - negative electrode shell. After sealing the assembled battery with a sealing machine, let it stand for 12 hours. The electrolyte solvent is a DOL / DME (volume ratio of 1:1) mixed solvent, the lithium salt in the electrolyte is LiTFSI, and the concentration of lithium salt in the electrolyte is 1 mol / L. The negative electrode plate is a lithium plate, and the separator is Celgard 2400.

[0060] The assembled battery was tested on a battery charge / discharge tester with a charge / discharge voltage range of 1.7-2.8V. Its rate performance is shown in the graph below. Figure 6 As shown, from Figure 6 As can be seen, the assembled lithium-sulfur battery still has a capacity of 712.5 mAh g⁻¹ at a current density of 6C. -1 The specific capacity was measured. The assembled battery was subjected to cycle performance testing on a battery charge / discharge tester. The charge / discharge voltage range was 1.7-2.8V, and the current was 0.5C. The results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the assembled lithium-sulfur battery still retains 786mAh g after 600 cycles. -1 The specific capacity corresponds to a capacity decay of 0.05% per revolution.

[0061] Example 2

[0062] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0063] Weigh 0.15g of ammonium metatungstate ((NH4)2WO4) and dissolve it in 40mL of deionized water. Add 2mL of phytic acid and continue stirring for 10 minutes. Add 3g of melamine and stir for 1.5 hours. Dry the mixture in a 70℃ oven to obtain the precursor. Place the precursor in a tube furnace and calcine it at 800℃ for 3 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0064] Scanning electron microscope (SEM) images of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this embodiment are shown below. Figure 8 As shown, from Figure 8 The sample shows a distinct sheet-like structure with WP particles evenly dispersed on it.

[0065] Example 3

[0066] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0067] Weigh 0.3g of tungsten trichloride and dissolve it in 50mL of deionized water. Add 3mL of phytic acid and continue stirring for 10 minutes. Add 4g of melamine and stir for 4 hours. Dry the mixture in an oven at 80℃ to obtain the precursor. Place the precursor in a tube furnace and calcine it at 900℃ for 5 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0068] Example 4

[0069] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0070] Weigh 0.5g of tungsten pentachloride and dissolve it in 40mL of deionized water. Add 2mL of phytic acid and continue stirring for 5 minutes. Add 6g of melamine and stir for 5 hours. Dry the mixture in a 90℃ oven to obtain the precursor. Place the precursor in a tube furnace and calcine it at 1000℃ for 2 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0071] The nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles was then loaded with sulfur and used as the cathode material for lithium-sulfur batteries. The method is as described in Example 1. The assembled battery was subjected to cycle performance testing on a battery charge-discharge instrument. The charge-discharge voltage range was 1.7-2.8V, and the current was 0.5C. The results are as follows: Figure 9 As shown, from Figure 9 As can be seen, the assembled lithium-sulfur battery still retains 512.5 mAh g after 100 cycles. -1 Specific capacity.

[0072] Comparative Example 1

[0073] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles includes the following steps:

[0074] Weigh 1.3g of sodium tungstate and dissolve it in 40mL of deionized water. Add 1mL of phytic acid and continue stirring for 10 minutes. Add 5g of melamine and stir for 1 hour. Dry the mixture in an oven at 80℃ to obtain the precursor. Place the precursor in a tube furnace and calcine it at 600℃ for 4 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles.

[0075] Transmission electron microscopy (TEM) images of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles prepared in this comparative example are shown below. Figure 10 As shown, from Figure 10 As can be seen, after excessively increasing the amount of tungsten source, the size of WP particles on the sample surface increases significantly.

[0076] Comparative Example 2

[0077] A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide includes the following steps:

[0078] Weigh 0.03g of sodium tungstate and dissolve it in 40mL of deionized water. Add 1mL of phytic acid and continue stirring for 10 minutes. Add 5g of melamine and stir for 1 hour. Dry the mixture in an oven at 80℃ to obtain the precursor. Place the precursor in a tube furnace and calcine it at 600℃ for 4 hours under an argon atmosphere to obtain the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide.

[0079] Transmission electron microscopy (TEM) images of the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide prepared in this comparative example are shown below. Figure 11 As shown, from Figure 11 As can be seen, after using an excessive amount of tungsten source, no obvious WP particles were observed on the sample surface.

[0080] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles, comprising the following steps: (1) Add phytic acid or sodium phytate and tungsten source to deionized water and stir at room temperature to dissolve them; then add nitrogen-containing material and continue stirring to disperse them evenly to obtain a dispersion; the tungsten source is ammonium metatungstate and / or sodium tungstate; the molar ratio of phytic acid or sodium phytate to tungsten source is 3-9:1; the nitrogen-containing material is one or more of melamine, dicyandiamide, urea, pyrrole, and p-phenylenediamine, and the mass ratio of nitrogen-containing material to tungsten source is 12-50:1; (2) The dispersion obtained in step (1) is dried to obtain a precursor; the precursor is calcined to obtain a nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles; the calcination is carried out under argon atmosphere protection; the calcination temperature is 500-1000℃ and the calcination time is 2-8 hours.

2. The method for preparing the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles according to claim 1, characterized in that, The ratio of the mass of the tungsten source to the volume of deionized water in step (1) is 0.001-0.05 g: 1 mL.

3. The method for preparing the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles according to claim 1, characterized in that, The nitrogen-containing material mentioned in step (1) is melamine and / or dicyandiamide; the stirring time after adding the nitrogen-containing material is 0.5-5 hours.

4. The method for preparing the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles according to claim 1, characterized in that, The drying temperature in step (2) is 60-100℃.

5. The method for preparing the nitrogen-phosphorus co-doped carbon nanosheet composite material loaded with tungsten phosphide nanoparticles according to claim 1, characterized in that, The calcination temperature in step (2) is 600-800℃; the calcination time is 4-6 hours.

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