High-entropy metal phosphide nanowires, methods of making and applications thereof

Abstract

The application discloses high-entropy metal phosphide nanowires and a preparation method and application thereof. The preparation method comprises the following steps: high-temperature treatment is performed on carbon nanotubes, the high-temperature treated carbon nanotubes and metal chlorides are mixed and ball milled to obtain a mixture, the metal chlorides comprise chlorides of more than five metal elements; in a protective atmosphere, the mixture is placed in a reaction chamber, heated to perform a first reaction, and then cooled; a phosphorus source and a product obtained in the first reaction are respectively placed in different areas of the reaction chamber, heated to perform a second reaction, and high-entropy metal phosphide nanowires are prepared. The preparation method of the high-entropy metal phosphide nanowires provided by the application utilizes carbon nanotubes as a template to construct, fills multiple chlorides, and then reacts with a phosphorus source under high-temperature conditions to obtain one-dimensional high-entropy metal phosphide, and the prepared high-entropy metal phosphide nanowires can be used as an electrocatalyst with excellent activity and stability, applied to electrocatalytic water splitting, and has a wide prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a high-entropy metal phosphide nanowire, its preparation method, and its application. Background Technology

[0002] Developing clean energy is an effective strategy for addressing the energy crisis and environmental pollution. Electrocatalytic water splitting is a highly efficient and cost-effective energy conversion technology that is expected to play an important role in reducing environmental pollution. The key issue is the development of electrocatalysts with excellent activity and stability.

[0003] High-entropy materials are a new class of multi-principal-element materials composed of multiple elements in equimolar or near-equimolar ratios. Due to their unique structure and elemental diversity, they are considered potential high-performance electrocatalysts. High-entropy materials can be divided into high-entropy alloys and high-entropy compounds. The former contains five or more metallic elements, while the latter contains both metallic and non-metallic elements. Compared to high-entropy alloys, research on high-entropy compounds is relatively limited. Due to the incompatibility between different metals and non-metals, the synthesis and structural control of high-entropy compounds, especially high-entropy metal phosphides, remain extremely difficult. Furthermore, due to the complexity of the structure of high-entropy compounds, their growth process is highly uncontrollable, making it difficult to obtain high-entropy compounds with specific morphologies (such as nanowire structures).

[0004] For example, patent CN113151856A discloses the preparation of a high-entropy alloy phosphide nanoparticle catalyst and its application in hydrogen production by water electrolysis. First, four or more metal sources are placed together with a phosphorus source in oleylamine, with a molar ratio of metal source to phosphorus source of 1:2. A buffer reagent is added, and the mixture is stirred until homogeneous. Under an inert atmosphere, the mixture is heated to 150°C and stirred to react. After the reaction is complete, the mixture is cooled, washed, centrifuged, and dissolved in n-hexane to obtain a high-entropy alloy phosphide nanoparticle solution. The nanoparticle solution is then loaded onto activated carbon via ultrasonic carbon loading and calcined to obtain a carbon-loaded high-entropy alloy phosphide nanoparticle catalyst. Patent CN111333079A discloses a method for preparing a high-entropy metal phosphide FeCoNiCrMnPx, comprising: weighing equal molar masses of FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CrCl3·6H2O, MnCl2·4H2O, and phytic acid, and forming a eutectic solvent (DESs) in an oil bath at 60°C; transferring the formed DESs to a reaction vessel and reacting it in an oven. xThe preparation method includes: weighing polyethylene glycol 200 and urea in a molar ratio of 2:1 and forming a eutectic solvent in an oil bath at 60°C; weighing equal molar masses of FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CrCl3·6H2O, and MnCl2·4H2O, and adding DESs to form a eutectic solvent system; transferring the formed DESs system to a reaction vessel, placing it in an oven for reaction, and after the reaction is complete, naturally cooling to room temperature, filtering, collecting the solid, and drying; placing the dried product in a tube furnace, heating the upstream region with sodium metaphosphate, calcining under an inert atmosphere, and cooling with the furnace. The literature (ChemSusChem 2020, 13, 2038-2042) reports CoCrFeMnNiP x The synthesis method is as follows: First, equimolar amounts (1 mmol) of CoCl₂·6H₂I, CrCl₃·6H₂O, FeCl₃·6H₂O, MnCl₂·4H₂O, and NiCl₂·6H₂O, 10 mmol of tetrabutylphosphine chloride, and 30 mmol of ethylene glycol were mixed. The mixture was then stirred at room temperature to form a homogeneous eutectic solvent. The resulting eutectic solvent was then incubated at 5 °C for 1 minute under an inert N₂ atmosphere. -1 The heating rate was increased from 25°C to 400°C for calcination, and the temperature was maintained at 400°C for 3 hours. Then it was cooled to room temperature to obtain the target product.

[0005] However, the existing technologies described above have the following drawbacks: Patents CN113151856A, CN114920222A, and CN114735667A all use large amounts of organic solvents or organic additives, such as oleylamine, ethylene glycol, and phytic acid, in the preparation of high-entropy metal phosphides, requiring subsequent washing of the products and causing contamination. Literature (ChemSusChem 2020, 13, 2038-2042) also uses a significant amount of organic solvents in the reaction process. More importantly, none of the above methods can control the growth of high-entropy metal phosphides in a single direction, making it impossible to obtain nanowire structures.

[0006] Currently, there are no reports on high-entropy phosphide nanowire structures. Summary of the Invention

[0007] The main objective of this invention is to provide a high-entropy metal phosphide nanowire and its preparation method, thereby overcoming the shortcomings of the prior art.

[0008] Another object of the present invention is to provide applications of the aforementioned high-entropy metal phosphide nanowires.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing high-entropy metal phosphide nanowires, comprising:

[0011] High-temperature treatment of carbon nanotubes;

[0012] High-temperature treated carbon nanotubes and metal chlorides are mixed and then ball-milled to obtain a mixture, wherein the metal chlorides include chlorides of five or more metal elements;

[0013] In a protective atmosphere, the mixture is placed in a reaction chamber and heated to 700-1050°C to carry out a first reaction, followed by cooling.

[0014] In a protective atmosphere, the phosphorus source and the product obtained from the first reaction are placed in different regions of the reaction chamber, and the temperature is raised to 250-400℃ to carry out a second reaction to obtain high-entropy metal phosphide nanowires. The phosphorus source and the product obtained from the first reaction are placed sequentially along the direction of the protective gas flow.

[0015] In some embodiments, the preparation method includes: subjecting carbon nanotubes to high-temperature treatment in air at a temperature of 450-650°C for 0.5-4 hours.

[0016] This invention also provides a high-entropy metal phosphide nanowire prepared by the aforementioned method.

[0017] This invention also provides the application of the aforementioned high-entropy metal phosphide nanowires in the preparation of electrocatalysts for electrocatalytic water splitting.

[0018] Accordingly, embodiments of the present invention also provide an electrocatalyst for electrocatalytic water splitting, which includes the aforementioned high-entropy metal phosphide nanowires.

[0019] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0020] The method for preparing high-entropy metal phosphide nanowires provided by this invention utilizes carbon nanotubes as templates for construction. After filling with various chlorides, the nanowires react with a phosphorus source under high-temperature conditions to obtain one-dimensional high-entropy metal phosphides. The preparation process is environmentally friendly. The high-entropy metal phosphide nanowires prepared by this invention can be used as electrocatalysts with excellent activity and stability, and have broad application prospects in electrocatalytic water splitting. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a TEM image of the high-entropy metal phosphide nanowires prepared in Example 1 of the present invention.

[0023] Figure 2 Aberration-corrected electron microscope image of the high-entropy metal phosphide nanowires prepared in Example 1 of this invention;

[0024] Figure 3 This is a high-resolution TEM mapping image of the high-entropy metal phosphide nanowires prepared in Example 1 of the present invention;

[0025] Figure 4 TEM image of the product obtained in Comparative Example 1;

[0026] Figure 5 TEM image of the product obtained in Comparative Example 2;

[0027] Figure 6 TEM image of the product obtained in Comparative Example 3;

[0028] Figure 7 Linear scanning voltammetry of the samples prepared in Example 1 and Comparative Example 1 of this invention during the oxygen evolution reaction of water electrolysis. Detailed Implementation

[0029] In view of the shortcomings of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. This invention utilizes carbon nanotubes as templates to construct a compound, filling it with various chlorides, and then reacting it with a phosphorus source under high-temperature conditions to obtain a one-dimensional high-entropy metal phosphide. To further understand this invention, the technical solution, its implementation process, and principles will be further explained below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of this invention, and not for limiting the scope of the claims.

[0030] One aspect of this invention provides a method for preparing high-entropy metal phosphide nanowires, comprising:

[0031] Carbon nanotubes are provided and subjected to high-temperature treatment;

[0032] High-temperature treated carbon nanotubes and metal chlorides are mixed and then ball-milled to obtain a mixture, wherein the metal chlorides include chlorides of five or more metal elements;

[0033] In a protective atmosphere, the mixture is placed in a reaction chamber and heated to 700-1050°C to carry out a first reaction, followed by cooling.

[0034] In a protective atmosphere, the phosphorus source and the product obtained from the first reaction are placed in different regions of the reaction chamber, and the temperature is raised to 250-400℃ to carry out a second reaction to obtain high-entropy metal phosphide nanowires. The phosphorus source and the product obtained from the first reaction are placed sequentially along the direction of the protective gas flow.

[0035] In some embodiments, the preparation method specifically includes: subjecting carbon nanotubes to high-temperature treatment in air at a temperature of 450-650°C for 0.5-4 hours. The mechanism of this invention's high-temperature treatment of carbon nanotubes lies in the fact that the two ends of carbon nanotubes are closed, making it difficult for external substances to enter their cavities. The purpose of the high-temperature treatment is to open the two ends of the carbon nanotubes, preparing them for filling with a host material. Limiting the high-temperature treatment temperature to the range of 450-650°C achieves both opening the two ends of the carbon nanotubes and limiting the damage to the nanotube walls caused by high temperatures, thus reducing the loss of carbon nanotubes.

[0036] Furthermore, the preparation method includes heating to the required high-temperature treatment temperature, i.e., 450-650℃, at a rate of 5-20℃ / min. This invention limits the heating rate to 5-20℃ / min, which is relatively fast and can reduce the loss of carbon nanotubes during the heating process.

[0037] In some embodiments, the carbon nanotubes used in this invention may be at least one of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), etc., but are not limited to this.

[0038] In some embodiments, the metal chlorides used in this invention contain five or more of the following metal elements: Mn, Fe, Co, Cu, Zn, Cr, Ni, Ag, Eu, Sm, Sr, and Dy, but are not limited to these.

[0039] Furthermore, the metal chloride may specifically be a combination of five or more of the following: MnCl2, FeCl2, FeCl3, CoCl2, CuCl2, ZnCl2, CrCl3, NiCl2, AgCl, EuCl3, SmCl3, SrCl2, and DyCl3, but is not limited to these.

[0040] In some embodiments, the mass ratio of carbon nanotubes to metal chloride is 1:5 to 1:1000. Limiting the aforementioned mass ratio range ensures that the carbon nanotubes are fully submerged when the metal chloride melts into a liquid state at high temperatures, thereby increasing the carbon nanotube filling rate.

[0041] In some embodiments, the preparation method specifically includes: mixing high-temperature treated carbon nanotubes with metal chlorides, and ball milling them in a vibratory ball mill (such as a vibratory ball mill) for 2-20 hours. The vibration frequency used in the ball milling is 500-2000 rpm, and the particle size of the mixture after ball milling is 50-200 mesh. The advantages of ball milling in this invention are: 1. Ball milling allows for thorough mixing of the various metal chlorides, which is beneficial for obtaining a uniformly distributed molten salt under high-temperature conditions and for forming a high-entropy structure; 2. Ball milling allows for sufficient contact between the metal chlorides and carbon nanotubes, which is beneficial for the metal chlorides to continuously enter the interior of the carbon nanotube cavities through capillary action, forming a continuous nanowire structure.

[0042] In some embodiments, the preparation method specifically includes: placing the mixture in a tube furnace, introducing a protective gas, heating to 700-1050°C, and moving the mixture to the central temperature region of the tube furnace for rapid heating and a first reaction for 5-20 hours, followed by natural cooling to room temperature. The mechanism of the first reaction step of the present invention is that this step includes two stages: high-temperature treatment and cooling. 1. High-temperature treatment stage: The mixture is placed in a tube furnace and heated to 700-1050°C for a first reaction for 5-20 hours; during this stage, the metal chloride melts from a solid block to a liquid state, i.e., a molten metal chloride salt is obtained, which continuously fills the cavities of the carbon nanotubes under capillary action. 2. Cooling stage: The tube furnace is removed, and the mixture is allowed to cool naturally to room temperature; during this stage, the liquid molten metal chloride salt filling the cavities of the carbon nanotubes solidifies into a solid state, resulting in a continuous nanowire structure. This cooling stage is necessary and is one of the key steps in obtaining the nanowire structure.

[0043] In some more specific embodiments, the preparation method specifically includes: transferring the mixture into a quartz boat and placing it into the quartz tube of a portable tube furnace, and introducing a protective gas. When the tube furnace is heated to 700-1050°C, the tube furnace is moved horizontally so that the quartz boat is located in the central temperature region for rapid heating. After 5-20 hours, the tube furnace is removed, and the quartz boat is allowed to cool naturally to room temperature. Further, the preparation method also includes: washing the product three times with water under ultrasonic vibration and freeze-drying for 24 hours.

[0044] Furthermore, the preparation method of the present invention further includes: after the first reaction and cooling steps are completed, the product obtained from the first reaction is washed with water to remove excess metal chlorides. The metal chlorides inside the carbon nanotubes are protected by the carbon nanotube walls and will not be dissolved by water; the excess metal chlorides remaining outside the tubes are dissolved by water and removed. After washing with water, the sample is freeze-dried to obtain the first reaction product, namely, high-entropy metal chloride nanowires confined within carbon nanotubes.

[0045] The purpose of freeze drying is to remove water, with a temperature range of -40 to -10°C and a time of 24-72 hours.

[0046] In some embodiments, the preparation method specifically includes:

[0047] The product obtained from the first reaction and the phosphorus source are placed in a tube furnace and a protective gas is introduced. The phosphorus source is close to the inlet of the protective gas, and the product obtained from the first reaction is far away from the inlet of the protective gas.

[0048] The tube furnace is heated to 250-400℃ at a heating rate of 0.5-5℃ / min to carry out the second reaction for 2-10 hours, and then cooled to room temperature to obtain high-entropy metal phosphide nanowires continuously embedded inside carbon nanotubes.

[0049] The reaction mechanism of the second reaction in this invention is as follows: This step is a phosphating reaction, in which a phosphorus source is placed upstream of the gas flow direction, and the product obtained from the first reaction is placed downstream. The phosphorus source decomposes at high temperature, producing PH3 gas, which reacts with the product of the first reaction to convert chloride into phosphide, yielding high-entropy metal phosphide nanowires. Limiting the temperature of the second reaction to 250-400°C allows the phosphorus source to decompose slowly and safely into PH3, converting chloride into phosphide.

[0050] In some embodiments, the phosphorus source includes at least one of NaH2PO2 and KH2PO2, but is not limited to this.

[0051] In some embodiments, the mass ratio of the phosphorus source to the product obtained from the first reaction is 20:1 to 500:1. This range of mass ratios ensures a sufficient phosphorus source to continuously decompose and release enough PH3 gas, achieving complete conversion of the first product to the second product.

[0052] In some more specific embodiments, the preparation method specifically includes: loading the product obtained from the first reaction and a phosphorus source onto two quartz boats respectively, and placing them in a tube furnace under a protective atmosphere, wherein the phosphorus source is placed on the upstream side and the product obtained from the first reaction is placed on the downstream side. The tube furnace is heated to 250-400°C at a heating rate of 0.5-5°C / min and held at that temperature for 2-10 hours, and then cooled to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0053] Furthermore, the protective gas used in this invention includes, but is not limited to, inert gases such as argon.

[0054] Another embodiment of the present invention also provides high-entropy metal phosphide nanowires prepared by the aforementioned method.

[0055] Furthermore, the high-entropy metal phosphide nanowires are one-dimensional structures with a diameter of 0.6-2.5 nm.

[0056] Another embodiment of the present invention also provides the application of the above-described high-entropy metal phosphide nanowires in the preparation of electrocatalysts for electrocatalytic water splitting.

[0057] Accordingly, another aspect of the present invention provides an electrocatalyst for electrocatalytic water splitting, which includes the aforementioned high-entropy metal phosphide nanowires.

[0058] In summary, the method for preparing high-entropy metal phosphide nanowires provided by this invention utilizes carbon nanotubes as templates and simultaneously fills them with a mixture of metal chlorides, thereby preparing ultrafine one-dimensional high-entropy metal phosphide nanowire structures, and the preparation process is environmentally friendly.

[0059] The technical solutions of the present invention will be described in detail below with reference to the specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0061] All processes and equipment in this invention are conventional names in the field, and each name is clear and unambiguous in its relevant application. Those skilled in the art can understand the conventional process steps and corresponding equipment used based on the name.

[0062] Example 1

[0063] (1) SWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 550°C at a rate of 5°C / min, holding for 2 hours, and then naturally cooling to room temperature.

[0064] (2) 30 mg of SWCNTs after high temperature treatment was mixed with 126 mg MnCl2, 127 mg FeCl2, 130 mg CoCl2, 134 mg CuCl2 and 136 mg ZnCl2 and ball milled in a vibrating ball mill for 4 hours at a vibration frequency of 1000 rpm.

[0065] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 700°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 6 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0066] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0067] (5) Load 0.1g of the dried product from step (4) and 2g of NaH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with NaH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 300℃ at a heating rate of 2℃ / min and hold for 3 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes (denoted as "MnFeCoCuZnP"). x @SWCNTs”).

[0068] The inventors of this case characterized the high-entropy metal phosphide nanowires prepared in this embodiment. Figure 1 This is a TEM image of the prepared high-entropy metal phosphide nanowires. As can be seen from the image, the high-entropy metal phosphide nanowires are continuously embedded inside the carbon nanotubes.

[0069] Figure 2 This is a spherical aberration electron microscope image of the high-entropy metal phosphide nanowires prepared in this embodiment. As can be seen from the image, the metal phosphide exhibits low crystallinity and a width of 1 nm to 2 nm.

[0070] Figure 3 This is a high-resolution TEM mapping image of the high-entropy metal phosphide nanowires prepared in this embodiment. The image shows that the Mn, Fe, Co, Cu, Zn, and P elements are uniformly distributed, consistent with the C element distribution of carbon nanotubes. This further confirms that the sample in this embodiment is MnFeCoCuZnP. x @SWCNTs.

[0071] Table 1 shows the ICP-OES of the high-entropy metal phosphide nanowires prepared in this embodiment. The table shows the synthesized MnFeCoCuZnP... x In @SWCNTs, the relative molar fractions of the metallic elements Mn, Fe, Co, Cu, and Zn in the total metal content are 19%, 24%, 16%, 26%, and 15%, respectively. The near-equal molar ratios of these metallic elements confirm that MnFeCoCuZnP x @SWCNTs have a high-entropy structure.

[0072] Table 1 ICP-OES of high-entropy metal phosphide nanowires

[0073]

[0074] Figure 7 The solid black line represents the linear sweep voltammogram of the high-entropy metal phosphide nanowires prepared in this embodiment during the oxygen evolution reaction in water electrolysis. A three-electrode system was used: a glassy carbon electrode loaded with the high-entropy metal phosphide nanowires served as the working electrode, an Ag / AgCl electrode as the reference electrode, and a carbon rod as the counter electrode. The electrolyte was 1.0 M KOH. Figure 7 As can be seen, the sample prepared in Example 1 has excellent electrocatalytic oxygen evolution performance at 10 mA emin. -2 The overpotential is 235mV.

[0075] Example 2

[0076] (1) SWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 550°C at a rate of 5°C / min, holding for 1 hour, and then naturally cooling to room temperature.

[0077] (2) 50 mg of SWCNTs after high temperature treatment was mixed with 214 mg MnCl2, 216 mg FeCl2, 221 mg CoCl2, 228 mg CuCl2 and 231 mg ZnCl2 and ball milled in a vibrating ball mill for 6 hours at a vibration frequency of 1200 rpm.

[0078] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 750°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 8 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0079] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0080] (5) Load 0.1g of the dried product from step (4) and 3g of NaH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with NaH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 300℃ at a heating rate of 1℃ / min and hold for 4 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0081] Example 3

[0082] (1) SWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 650°C at a rate of 10°C / min, holding for 2 hours, and then naturally cooling to room temperature.

[0083] (2) 50 mg of SWCNTs after high temperature treatment was mixed with 214 mg MnCl2, 216 mg FeCl2, 221 mg CoCl2, 228 mg CuCl2 and 231 mg ZnCl2 and ball milled in a vibrating ball mill for 6 hours at a vibration frequency of 1000 rpm.

[0084] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 850°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 8 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0085] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0086] (5) Load 0.1g of the dried product from step (4) and 5g of NaH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with NaH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 350°C at a heating rate of 2°C / min and hold for 8 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0087] Example 4

[0088] (1) SWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 550°C at a rate of 5°C / min, holding for 3 hours, and then naturally cooling to room temperature.

[0089] (2) 10 mg of SWCNTs after high temperature treatment was mixed with 214 mg MnCl2, 216 mg FeCl2, 221 mg CoCl2, 228 mg CuCl2 and 231 mg ZnCl2 and ball milled in a vibrating ball mill for 3 hours at a vibration frequency of 1500 rpm.

[0090] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 800°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 8 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0091] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0092] (5) Load 0.05g of the dried product from step (4) and 1g of NaH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with NaH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 320℃ at a heating rate of 0.5℃ / min and hold for 3 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0093] Example 5

[0094] (1) SWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 550°C at a rate of 5°C / min, holding for 1 hour, and then naturally cooling to room temperature.

[0095] (2) 80 mg of SWCNTs after high temperature treatment were mixed with 642 mg MnCl2, 648 mg FeCl2, 663 mg CoCl2, 684 mg CuCl2 and 693 mg ZnCl2 and ball milled in a vibrating ball mill for 20 hours at a vibration frequency of 500 rpm.

[0096] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 1000°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 12 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0097] (4) The product obtained in step (3) was washed with water three times under ultrasonic vibration and then freeze-dried for 40 hours.

[0098] (5) Load 0.1g of the dried product from step (4) and 8g of NaH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with NaH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 350°C at a heating rate of 1°C / min and hold for 7 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0099] Example 6

[0100] (1) MWCNTs were subjected to high temperature treatment in air. Specifically, the high temperature reaction was carried out by heating to 650°C at a rate of 20°C / min, holding for 0.5 hours, and then naturally cooling to room temperature.

[0101] (2) The MWCNTs after high temperature treatment were mixed with FeCl3, CrCl3, NiCl2, AgCl and EuCl3. The mass ratio of MWCNTs to the five metal chlorides was 1:5. The mixture was then ball-milled in a vibrating ball mill for 2 hours at a vibration frequency of 2000 rpm.

[0102] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 1050°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 5 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0103] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0104] (5) Load 0.1g of the dried product from step (4) and 20g of KH2PO2 onto two quartz boats respectively, and place them into a tube furnace under an Ar atmosphere, with KH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 400℃ at a heating rate of 5℃ / min and hold for 2 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0105] Example 7

[0106] (1) MWCNTs were subjected to high-temperature treatment in air. Specifically, the high-temperature reaction was carried out by heating to 450°C at a rate of 5°C / min, holding for 4 hours, and then naturally cooling to room temperature.

[0107] (2) The MWCNTs after high temperature treatment were mixed with FeCl3, CrCl3, SmCl3, SrCl2 and DyCl3. The mass ratio of MWCNTs to the five metal chlorides was 1:1000. The mixture was then ball-milled in a vibrating ball mill for 20 hours at a vibration frequency of 800 rpm.

[0108] (3) Transfer the obtained mixture to a quartz boat and place it in the quartz tube of a portable tube furnace, then introduce Ar gas. When the tube furnace is heated to 900°C, move the tube furnace horizontally so that the quartz boat is in the central temperature region for rapid heating. After 20 hours, remove the tube furnace and allow the quartz boat to cool naturally to room temperature.

[0109] (4) The product obtained in step (3) is washed three times with water under ultrasonic vibration and then freeze-dried for 24 hours.

[0110] (5) Load 0.1g of the dried product from step (4) and 50g of KH2PO2 onto two quartz boats respectively, and place them in a tube furnace under an Ar atmosphere, with KH2PO2 on the upstream side and the product on the downstream side. Heat the tube furnace to 250°C at a heating rate of 3°C / min and hold for 10 hours, then cool to room temperature to obtain high-entropy metal phosphide nanowires embedded in carbon nanotubes.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that the high-temperature treatment in step (1) was not performed.

[0113] Figure 4 This is a TEM image of the product obtained in this comparative example. It can be seen that there is no continuous nanowire structure inside the carbon nanotube. This is because step (1) is missing, and the two ends of the carbon nanotube are closed, which makes it impossible to confine the guest material. The metal chloride completely leaves the carbon nanotube during the water washing process.

[0114] Figure 7 The gray dashed line data represents the linear sweep voltammogram of the sample prepared in this comparative example during the oxygen evolution reaction in water electrolysis. The reaction employed a three-electrode system: a glassy carbon electrode loaded with high-entropy metal phosphide nanowires as the working electrode, an Ag / AgCl electrode as the reference electrode, and a carbon rod as the counter electrode; the electrolyte was 1.0 M KOH. From... Figure 7 As can be seen, some of the samples in Comparative Example 1 exhibited very poor electrocatalytic oxygen evolution performance at 10 mA cm⁻¹. 2 The overpotential is 460mV.

[0115] Comparative Example 2

[0116] The difference between this comparative example and Example 1 is that the ball milling process in step (2) was not performed.

[0117] Figure 5 This is a TEM image of the product obtained in this comparative example. It can be seen that there are many amorphous particles attached to the outside of the carbon nanotubes, and there is no obvious nanowire structure inside the carbon nanotubes. This is because step (2) is missing, the carbon nanotubes cannot be fully mixed with the metal salt, and it is difficult to confine the metal salt inside the tube through capillary action; and due to the uneven mixing of reactants, the reaction process causes agglomeration and produces by-products.

[0118] Comparative Example 3

[0119] The difference between this comparative example and Example 1 is that the mass ratio of carbon nanotubes to metal chlorides in step (2) exceeds the maximum value of the limited mass ratio range, which is 1:1.

[0120] Figure 6This is a TEM image of the product obtained in this comparative example. It can be seen that continuous nanowire structures are difficult to observe inside the carbon nanotubes. This is because the mass ratio of carbon nanotubes to metal chlorides is too large; after the metal chlorides melt, they are insufficient to impregnate the carbon nanotubes, making it difficult to form capillary action.

[0121] In addition, the inventors of this case also conducted experiments with other raw materials and conditions listed in this specification, referring to Examples 1-7, and obtained relatively ideal results in all of them.

[0122] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-entropy metal phosphide nanowires, characterized in that, include: Carbon nanotubes are subjected to high-temperature treatment in air at a temperature of 450-650°C for 0.5-4 hours. High-temperature treated carbon nanotubes are mixed with metal chlorides and ball-milled in a vibratory ball mill for 2-20 hours to obtain a mixture. The vibration frequency used in the ball milling process is 500-2000 rpm, and the particle size of the mixture after ball milling is 50-200 mesh. The metal chloride contains five or more metal elements selected from Mn, Fe, Co, Cu, Zn, Cr, Ni, Ag, Eu, Sm, Sr, and Dy. The mass ratio of carbon nanotubes to metal chlorides is 1:5 to 1:1000. The mixture is placed in a tube furnace and a protective gas is introduced. The temperature is raised to 700-1050°C, and the mixture is moved to the central temperature zone of the tube furnace for rapid heating and the first reaction for 5-20 hours. After the reaction is completed, the mixture is allowed to cool naturally to room temperature. The product obtained from the first reaction and the phosphorus source are placed in a tube furnace and a protective gas is introduced. The phosphorus source is close to the inlet of the protective gas, and the product obtained from the first reaction is far away from the inlet of the protective gas. The tube furnace is heated to 250-400℃ at a heating rate of 0.5-5℃ / min to carry out the second reaction for 2-10 h, and then cooled to room temperature to obtain high-entropy metal phosphide nanowires continuously embedded inside carbon nanotubes; the mass ratio of the phosphorus source to the product obtained from the first reaction is 20:1-500:

1.

2. The preparation method according to claim 1, characterized in that, include: Heat to the required temperature for high-temperature treatment at a rate of 5-20℃ / min.

3. The preparation method according to claim 1, characterized in that: The carbon nanotubes are selected from at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

4. The preparation method according to claim 1, characterized in that: The metal chloride is selected from five or more combinations of MnCl2, FeCl2, FeCl3, CoCl2, CuCl2, ZnCl2, CrCl3, NiCl2, AgCl, EuCl3, SmCl3, SrCl2, and DyCl3.

5. The preparation method according to claim 1, characterized in that: The phosphorus source is selected from at least one of NaH2PO2 and KH2PO2.

6. The preparation method according to claim 1, characterized in that: The protective gas is argon.

7. High-entropy metal phosphide nanowires prepared by any one of claims 1-6, wherein the high-entropy metal phosphide nanowires are one-dimensional structures with a diameter of 0.6-2.5 nm.

8. The application of the high-entropy metal phosphide nanowires of claim 7 in the preparation of electrocatalysts for electrocatalytic water splitting.

9. An electrocatalyst for electrocatalytic water splitting, characterized in that, Including the high-entropy metal phosphide nanowires as described in claim 7.

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