Carbon-coated tungsten oxide quantum dot material as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to a carbon-coated tungsten oxide quantum dot material and a preparation method and application thereof.The preparation method comprises the steps that a tungsten source is added into a polyhydric alcohol solution to obtain a mixed solution, the mixed solution is placed in a microwave reactor, heat preservation is conducted for the first time at the first reaction power and the first temperature, the tungsten source is heated and decomposed into tungsten oxide, and the tungsten oxide is obtained; performing coordination bonding on oxygen atoms of tungsten oxide and hydroxyl groups of the polyol solution to obtain a reaction precursor solution; carrying out heat preservation on the reaction precursor solution at a second reaction power and a second temperature for a second time, so that the crystal nucleus of tungsten oxide grows in the polyol solution, and obtaining a polyol solution of tungsten oxide quantum dots; the preparation method comprises the following steps: in an inert atmosphere, performing spray pyrolysis on a polyol solution of tungsten oxide quantum dots, so that the outer surfaces of the tungsten oxide quantum dots are coated with carbonized polyol, and the carbon-coated tungsten oxide quantum dot material is obtained.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a carbon-coated tungsten oxide quantum dot material, its preparation method, and its applications. Background Technology

[0002] Carbon-coated tungsten oxide, as a composite material with excellent properties, has broad application prospects in water electrolysis for hydrogen production, capacitor deionization, energy storage, and other fields. However, existing technologies commonly employ complex preparation methods for carbon-coated tungsten oxide, involving multiple operational steps, making it difficult to strictly control product quality. Furthermore, the preparation time is long, the timeliness is low, and the production cost is high, hindering mass production. Moreover, all existing technologies cannot obtain carbon-coated tungsten oxide materials with a particle size smaller than 10 nm. For example, Chinese patent CN111974377B uses a hydrothermal method to prepare the precursor in the process of preparing carbon-coated defective tungsten oxide, with a maximum concentration of carbon and tungsten sources of only 2 mg / ml during the hydrothermal process. The hydrothermal reaction is carried out at 150°C, generating significant pressure and posing substantial safety hazards. The low reactant concentration results in extremely low yield, high energy consumption, and a substantial increase in cost. After obtaining the precursor, further filtration, washing, and low-temperature drying are required, which undoubtedly increases the complexity of the process, generates a large amount of waste liquid, increases the preparation time, and increases production costs. Chinese patent CN112044429B uses polystyrene microspheres as a reaction template in the preparation of oxygen-vacancy-rich carbon-doped tungsten oxide hollow microspheres. The addition of the template undoubtedly increases the cost of the reaction raw materials, and the removal of the template also complicates the process. Chinese patent CN115636480B, in the preparation of carbon-coated tungsten oxide composite electrode materials, uses hexachloride as a reaction raw material and ethanol as a reaction solvent to achieve a special morphological characteristic for tungsten oxide, reacting at 160°C for 24 hours. Hexachloride is extremely corrosive and reacts readily with water, even in humid air, producing a large amount of hydrogen chloride fumes. Meanwhile, ethanol, as a reaction solvent, has a lower boiling point than water, generating greater pressure at the same temperature, and is also a highly flammable liquid. As mentioned above, the entire reaction process poses significant safety hazards. The raw materials can corrode equipment, excessive pressure can cause injury or death, and the large-scale use of ethanol also presents a significant fire hazard. Furthermore, the yield of this method is extremely low, making industrial-scale production difficult. Chinese patent CN110563043B utilizes a hydrothermal method to prepare carbon-coated tungsten oxide nanospheres in a one-step process. While this simplifies the experimental procedure, the use of hydrothermal technology and the hydrothermal temperature exceeding 160°C generate enormous pressure during the reaction, creating safety risks. Additionally, the extremely low concentration of reactants significantly increases production costs. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a carbon-coated tungsten oxide quantum dot material, its preparation method, and its applications. This preparation method is simple and efficient, without complex reaction processes and steps, and does not involve repeated washing, thus reducing waste liquid discharge, lowering environmental pollution, and having low preparation costs, making it easy to achieve mass production.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing carbon-coated tungsten oxide quantum dot materials, the method comprising:

[0005] A tungsten source is added to a polyol solution to obtain a mixture. The mixture is then placed in a microwave reactor and kept at a first reaction power and a first temperature for a first time, causing the tungsten source to decompose into tungsten oxide. The oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the polyol solution to obtain a reaction precursor solution.

[0006] The reaction precursor solution is kept at a second reaction power and a second temperature for a second time, so that the tungsten oxide nuclei grow in the polyol solution to obtain a polyol solution of tungsten oxide quantum dots.

[0007] Under an inert atmosphere, the polyol solution of the tungsten oxide quantum dots is spray-pyrolyzed, so that the polyol is carbonized and coated on the outer surface of the tungsten oxide quantum dots, thus obtaining carbon-coated tungsten oxide quantum dot material.

[0008] Preferably, the tungsten source includes one or more of ammonium tungstate, tungstic acid, ammonium metatungstate, and ammonium paratungstate.

[0009] Preferably, the polyol includes one or more of ethylene glycol, propylene glycol, and glycerol.

[0010] Preferably, the concentration of the tungsten source in the mixture is 0.5 mol / L to 4 mol / L.

[0011] Preferably, the first reaction power is 300W-500W, the first temperature is 80℃-120℃, and the first time is 0.5h-2h; the second reaction power is 600W-1000W, the second temperature is 140℃-180℃, and the second time is 5h-8h.

[0012] Preferably, the spray pyrolysis pressure is 0.1MPa-0.6MPa, the temperature is 300℃-800℃, and the flow rate of the polyol solution containing tungsten oxide quantum dots is 5L / h-20L / h.

[0013] In a second aspect, the present invention provides a carbon-coated tungsten oxide quantum dot material, wherein the carbon-coated tungsten oxide quantum dot material is prepared by any of the preparation methods described in the first aspect above; the structure of the carbon-coated tungsten oxide quantum dot material includes an outer shell and a core; the outer shell is a carbon coating layer, and the core is located inside the carbon coating layer, wherein the core is a tungsten oxide quantum dot.

[0014] Preferably, the thickness of the carbon coating layer is 1nm-8nm, and the size of the tungsten oxide quantum dots is 1nm-5nm.

[0015] Thirdly, the present invention provides a catalytic and electrode material, the catalytic and electrode material comprising the carbon-coated tungsten oxide quantum dot material described in any of the second aspects above.

[0016] Fourthly, the present invention provides an application of the catalytic and electrode materials described in the third aspect above, wherein the catalytic material is used for photocatalysis and thermocatalysis; and the electrode material is used for electrochemical catalysis and electrochemical energy storage devices.

[0017] This invention provides a method for preparing carbon-coated tungsten oxide quantum dot materials. When a tungsten source is heated and decomposes into tungsten oxide, the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of a polyol solution, confining the tungsten oxide seed crystals within the polyol solution, thus obtaining a reaction precursor solution. Further heating of the reaction precursor solution allows the tungsten oxide nuclei to grow further. However, the combined effect of the hydroxyl groups of the polyol and the viscosity of the polyol solution limits the continued growth of the nuclei, resulting in a polyol solution of tungsten oxide quantum dots. Subsequently, the polyol solution of tungsten oxide quantum dots is subjected to spray pyrolysis. This spray pyrolysis process allows the polyol to be directly carbonized and coated onto the surface of the tungsten oxide quantum dots. This carbon coating restricts the further growth of the tungsten oxide quantum dots at high temperatures, ultimately yielding carbon-coated tungsten oxide quantum dots with good dispersibility and small particle size.

[0018] In summary, the preparation method of this application is simple and efficient, without complicated reaction processes and steps, uses inexpensive and readily available raw materials, does not involve repeated washing, reduces waste liquid discharge, lowers environmental pollution, and has low preparation cost, making it easy to achieve mass production.

[0019] The carbon-coated tungsten oxide quantum dot material prepared by this method exhibits a small particle size and narrow particle size distribution, while achieving uniform carbon coating on the tungsten oxide surface. The small particle size and narrow particle size distribution significantly increase the specific surface area and reactive sites of the carbon-coated tungsten oxide quantum dot material. When applied in energy storage devices, this can improve the electrode reactivity and cycle life of the energy storage device. The significantly increased carbon coating amount and direct contact between particles through the carbon coating layer enhance electronic conductivity. In energy storage devices, this can reduce internal resistance, improve rate performance, and enhance cycle life. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation method of carbon-coated tungsten oxide quantum dot material provided in this embodiment of the invention.

[0021] Figure 2 This is a schematic diagram of a carbon coating device provided in an embodiment of the present invention;

[0022] Figure 3 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Embodiment 1 of the present invention.

[0023] Figure 4 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Embodiment 2 of the present invention.

[0024] Figure 5 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Example 3 of the present invention.

[0025] Figure 6 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Example 4 of the present invention.

[0026] Figure 7 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Embodiment 5 of the present invention.

[0027] Figure 8 This is a transmission electron microscope (TEM) image of the carbon-coated tungsten oxide quantum dot material provided in Embodiment 6 of the present invention.

[0028] Figure 9 This is a transmission electron microscope image of the carbon-coated tungsten oxide quantum dot material provided in Comparative Example 1 of the present invention;

[0029] Figure 10 This is a transmission electron microscope image of the carbon-coated tungsten oxide quantum dot material provided in Comparative Example 2 of the present invention;

[0030] Figure 11 This is a nanoparticle size distribution diagram of the carbon-coated tungsten oxide quantum dot material provided in Example 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] This invention provides a method for preparing carbon-coated tungsten oxide quantum dot materials, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0034] Step 110: Add the tungsten source to the polyol solution to obtain a mixture, and place the mixture in a microwave reactor. Keep it at the first reaction power and first temperature for a first time so that the tungsten source is decomposed into tungsten oxide. The oxygen atoms of the tungsten oxide coordinate and bond with the hydroxyl groups of the polyol solution to obtain the reaction precursor solution.

[0035] Specifically, the tungsten source may include one or more of ammonium tungstate, tungstic acid, ammonium metatungstate, and ammonium paratungstate. Ammonium tungstate and tungstic acid are preferred. The polyol may include one or more of ethylene glycol, propylene glycol, and glycerol. Ethylene glycol and glycerol are preferred. The concentration of the tungsten source in the mixture can be 0.5 mol / L to 4 mol / L. The first reaction power can be 300 W to 500 W, preferably 350 W to 450 W. The first temperature can be 80 °C to 120 °C, preferably 90 °C to 110 °C. The first reaction time can be 0.5 h to 2 h, preferably 1 h to 1.5 h.

[0036] When the tungsten source is heated and decomposes into tungsten oxide, the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the polyol solution, thus confining the tungsten oxide seed crystals within the polyol solution and yielding the reaction precursor solution. This process eliminates the need for a reaction template, reducing preparation costs and eliminating the template removal process, thus facilitating mass production.

[0037] Step 120: The reaction precursor solution is kept at the second reaction power and second temperature for a second time, so that the tungsten oxide nuclei grow in the polyol solution to obtain a polyol solution of tungsten oxide quantum dots.

[0038] Specifically, the second reaction power can be 600W-1000W, preferably 700W-900W; the second temperature can be 140℃-180℃, preferably 150℃-170℃; and the second time can be 5h-8h, preferably 6h-7h.

[0039] This step involves further heating of the precursor solution, which allows the tungsten oxide crystal nuclei to grow further. However, the bonding between the hydroxyl groups of the polyol and the oxygen in the tungsten oxide, along with the viscosity of the polyol solution, limits the continued growth of the crystal nuclei, resulting in a polyol solution of tungsten oxide quantum dots. This process eliminates the need for filtration, washing, and drying of the precursor solution, reducing the number of reaction steps and processes. It also eliminates repeated washing, reducing wastewater discharge and environmental pollution.

[0040] Step 130: Under an inert atmosphere, the polyol solution of tungsten oxide quantum dots is spray-pyrolyzed, so that the polyol is carbonized and coated on the outer surface of the tungsten oxide quantum dots, thus obtaining carbon-coated tungsten oxide quantum dot material.

[0041] Specifically, the inert atmosphere can be nitrogen and / or argon. The spray pyrolysis pressure can be 0.1 MPa-0.6 MPa, preferably 0.2 MPa-0.4 MPa, the temperature can be 300℃-800℃, preferably 400℃-600℃, and the flow rate of the polyol solution containing tungsten oxide quantum dots is 5 L / h-20 L / h, preferably 10 L / h-15 L / h.

[0042] More specifically, the polyol solution of tungsten oxide quantum dots is transported to, for example... Figure 2 The process is carried out in the spray pyrolysis apparatus shown. The atomization driving force of the spray pyrolysis apparatus is gas pressure, and it mainly includes an atomization section, a pyrolysis furnace, a collection section, and a tail gas treatment section. The atomization section mainly includes a compressor and a storage bottle. The collection section includes a cyclone collector and a collection bottle.

[0043] The process involves storing a polyol solution containing tungsten oxide quantum dots in a storage bottle. An inert gas, pressurized by a compressor, atomizes the polyol solution and transports it to a pyrolysis furnace. The pyrolysis furnace further heats the atomized polyol solution, causing the polyol to decompose and carbonize. The resulting powder, carbon-coated tungsten oxide quantum dot powder, is collected by a collection bottle and a cyclone collector. The gas generated during pyrolysis is then treated in the exhaust gas treatment section.

[0044] The spray pyrolysis process allows polyols to be directly carbonized and coated on the surface of tungsten oxide quantum dots. The carbon coating restricts the further growth of tungsten oxide quantum dots at high temperatures, ultimately resulting in carbon-coated tungsten oxide quantum dots with good dispersibility and small particle size.

[0045] This step allows for direct spray pyrolysis of the polyol solution containing tungsten oxide quantum dots, eliminating the need for additional carbon sources or solidification of the solution into particles before carbonization. This simplifies the preparation process, enables in-situ carbonization of the polyol, and improves the uniformity of carbon coating.

[0046] The structure of carbon-coated tungsten oxide quantum dot materials consists of an outer shell and a core. The outer shell is a carbon coating layer, and the core, which is a tungsten oxide quantum dot, is located inside the carbon coating layer. The thickness of the carbon coating layer is 1 nm-8 nm, and the size of the tungsten oxide quantum dots is 1 nm-5 nm.

[0047] In summary, the present invention provides a method for preparing carbon-coated tungsten oxide quantum dot materials. When a tungsten source is heated and decomposes into tungsten oxide, the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of a polyol solution, confining the tungsten oxide seed crystals within the polyol solution, thus obtaining a reaction precursor solution. Further heating of the reaction precursor solution allows the tungsten oxide nuclei to grow further. However, the combined effect of the hydroxyl groups of the polyol and the viscosity of the polyol solution limits the continued growth of the nuclei, resulting in a polyol solution of tungsten oxide quantum dots. Subsequently, the polyol solution of tungsten oxide quantum dots is subjected to spray pyrolysis. This spray pyrolysis process allows the polyol to be directly carbonized and coated onto the surface of the tungsten oxide quantum dots. This carbon coating restricts the further growth of the tungsten oxide quantum dots at high temperatures, ultimately yielding carbon-coated tungsten oxide quantum dots with good dispersibility and small particle size.

[0048] In summary, the preparation method of this application is simple and efficient, without complicated reaction processes and steps, uses inexpensive and readily available raw materials, does not involve repeated washing, reduces waste liquid discharge, lowers environmental pollution, and has low preparation cost, making it easy to achieve mass production.

[0049] The carbon-coated tungsten oxide quantum dot material prepared by this method exhibits a small particle size and narrow particle size distribution, while achieving uniform carbon coating on the tungsten oxide surface. The small particle size and narrow particle size distribution significantly increase the specific surface area and reactive sites of the carbon-coated tungsten oxide quantum dot material. When applied in energy storage devices, this can improve the electrode reactivity and cycle life of the energy storage device. The significantly increased carbon coating amount and direct contact between particles through the carbon coating layer enhance electronic conductivity. In energy storage devices, this can reduce internal resistance, improve rate performance, and enhance cycle life.

[0050] The carbon-coated tungsten oxide quantum dot material provided by this invention can be used in photocatalysis, thermocatalysis, and as electrode material in electrochemical catalysis and electrochemical energy storage devices. The carbon-coated tungsten oxide quantum dot material has high electronic and ionic conductivity, which can improve catalytic reaction activity and improve the rate performance and cycle performance of energy storage devices.

[0051] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing carbon-coated tungsten oxide quantum dot materials using the method provided in the above embodiments of the present invention.

[0052] Example 1

[0053] The first step is to add ammonium tungstate to the ethylene glycol solution to obtain a 1 mol / L mixture.

[0054] The second step involves placing the mixture in a microwave reactor and maintaining the temperature at 100°C and 300W for 0.5 hours, allowing ammonium tungstate to decompose into tungsten oxide. The oxygen atoms of the tungsten oxide then coordinate with the hydroxyl groups of the ethylene glycol solution to obtain the precursor solution.

[0055] The third step involves increasing the microwave reaction power to 700W and the temperature to 150℃, and then keeping the precursor solution at this temperature for 6 hours. This allows the tungsten oxide nuclei to grow in the ethylene glycol solution, resulting in an ethylene glycol solution of tungsten oxide quantum dots.

[0056] The fourth step involves spray-pyrolyzing an ethylene glycol solution containing tungsten oxide quantum dots under a nitrogen atmosphere, thereby carbonizing the ethylene glycol to obtain carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.3 MPa, the temperature is 600 °C, and the flow rate of the ethylene glycol solution containing tungsten oxide quantum dots is 10 L / h.

[0057] The prepared carbon-coated tungsten oxide quantum electric material was then tested.

[0058] First, the average particle size and particle size distribution width are tested using a Malvern laser particle size analyzer. The specific testing method involves ultrasonically dispersing carbon-coated tungsten oxide quantum electric material powder in ethanol, and then placing it into the instrument for testing.

[0059] Secondly, the conductivity was tested using the four-probe method, following the standard GB / T24521-2018 Method for Determination of Resistivity of Carbon Raw Materials and Coke, with a pressure of 3.9 MPa ± 0.03 MPa. The powder mold inner diameter was 16 mm-16.3 mm. The height measurement range was 15-17 mm. The test current was 500 mA. The following examples and comparative examples used the same methods for testing average particle size, particle size distribution width, and conductivity as in Example 1, and will not be repeated here.

[0060] Example 2

[0061] The first step is to add ammonium tungstate to the propylene glycol solution to obtain a 2 mol / L mixture.

[0062] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 300W and a temperature of 90℃ for 1 hour. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the propylene glycol solution to obtain the reaction precursor solution.

[0063] The third step involves increasing the microwave reaction power to 800W and the temperature to 160℃, and then keeping the precursor solution at this temperature for 7 hours. This allows the tungsten oxide nuclei to grow in the propylene glycol solution, resulting in a propylene glycol solution of tungsten oxide quantum dots.

[0064] The fourth step involves spray-pyrolyzing a propylene glycol solution containing tungsten oxide quantum dots under a nitrogen atmosphere to carbonize the propylene glycol, thereby obtaining carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.5 MPa, the temperature is 700 °C, and the flow rate of the propylene glycol solution containing tungsten oxide quantum dots is 10 L / h.

[0065] Example 3

[0066] The first step is to add ammonium tungstate to the glycerol solution to obtain a 4 mol / L mixture.

[0067] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 500W and a temperature of 120℃ for 2 hours. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the glycerol solution to obtain the reaction precursor solution.

[0068] The third step involves increasing the microwave reaction power to 1000W and the temperature to 180℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the glycerol solution, resulting in a glycerol solution of tungsten oxide quantum dots.

[0069] The fourth step involves spray-pyrolyzing the glycerol solution of tungsten oxide quantum dots under a nitrogen atmosphere to carbonize the glycerol, thereby obtaining carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.6 MPa, the temperature is 800 °C, and the flow rate of the glycerol solution for the tungsten oxide quantum dots is 15 L / h.

[0070] Example 4

[0071] The first step is to add ammonium tungstate to the glycerol solution to obtain a 2 mol / L mixture.

[0072] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 400W and a temperature of 100℃ for 1 hour. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the glycerol solution to obtain the reaction precursor solution.

[0073] The third step involves increasing the microwave reaction power to 900W and the temperature to 180℃, and then keeping the precursor solution at this temperature for 7 hours. This allows the tungsten oxide nuclei to grow in the glycerol solution, resulting in a glycerol solution of tungsten oxide quantum dots.

[0074] The fourth step involves spray-pyrolyzing a glycerol solution containing tungsten oxide quantum dots under a nitrogen atmosphere to carbonize the glycerol, thereby obtaining carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.6 MPa, the temperature is 700 °C, and the flow rate of the glycerol solution containing tungsten oxide quantum dots is 20 L / h.

[0075] Example 5

[0076] The first step is to add ammonium tungstate to the propylene glycol solution to obtain a 4 mol / L mixture.

[0077] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 400W and a temperature of 120℃ for 2 hours. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the propylene glycol solution to obtain the reaction precursor solution.

[0078] The third step involves increasing the microwave reaction power to 1000W and the temperature to 180℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the propylene glycol solution, resulting in a propylene glycol solution of tungsten oxide quantum dots.

[0079] The fourth step involves spray-pyrolyzing a propylene glycol solution containing tungsten oxide quantum dots under an argon atmosphere to carbonize the propylene glycol, yielding carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.4 MPa, the temperature is 800 °C, and the flow rate of the propylene glycol solution containing tungsten oxide quantum dots is 15 L / h.

[0080] Example 6

[0081] The first step is to add ammonium tungstate to the ethylene glycol solution to obtain a 3 mol / L mixture.

[0082] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 500W and a temperature of 120℃ for 0.5 hours. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the ethylene glycol solution to obtain the reaction precursor solution.

[0083] The third step involves increasing the microwave reaction power to 900W and the temperature to 160℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the ethylene glycol solution, resulting in an ethylene glycol solution of tungsten oxide quantum dots.

[0084] The fourth step involves spray-pyrolyzing an ethylene glycol solution containing tungsten oxide quantum dots under a nitrogen atmosphere, thereby carbonizing the ethylene glycol to obtain carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.5 MPa, the temperature is 800 °C, and the flow rate of the ethylene glycol solution containing tungsten oxide quantum dots is 15 L / h.

[0085] Comparative Example 1

[0086] The first step is to add ammonium tungstate to the ethylene glycol solution to obtain a 3 mol / L mixture.

[0087] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 500W and a temperature of 120℃ for 0.5 hours. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the ethylene glycol solution to obtain the reaction precursor solution.

[0088] The third step involves increasing the microwave reaction power to 900W and the temperature to 160℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the ethylene glycol solution, resulting in an ethylene glycol solution of tungsten oxide quantum dots.

[0089] The fourth step involves placing the ethylene glycol solution of tungsten oxide quantum dots in an oven and heating it at 200°C for 5 hours to obtain a clay-like solid.

[0090] The fifth step involves placing the clay-like solid in an air atmosphere and heating it at 600°C for 2 hours. After cooling, carbon-coated tungsten oxide quantum dot material is obtained.

[0091] Comparative Example 2

[0092] The first step is to add ammonium tungstate to the glycerol solution to obtain a 3 mol / L mixture.

[0093] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 500W and a temperature of 120℃ for 0.5 hours. This allows ammonium tungstate to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide coordinate with the hydroxyl groups of the glycerol solution to obtain the reaction precursor solution.

[0094] The third step involves increasing the microwave reaction power to 1000W and the temperature to 180℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the glycerol solution, resulting in a glycerol solution of tungsten oxide quantum dots.

[0095] The fourth step involves placing the glycerol solution of tungsten oxide quantum dots in an oven and heating it at 250°C for 5 hours to obtain a clay-like solid.

[0096] The fifth step involves placing the clay-like solid in an air atmosphere and heating it at 700°C for 2 hours. After cooling, carbon-coated tungsten oxide quantum dot material is obtained.

[0097] Table 1 shows the test data of carbon-coated tungsten oxide quantum dot materials in Examples 1-6 and Comparative Examples 1-2.

[0098] Average particle size Particle size distribution width electrical conductivity Example 1 2.5nm 2nm 0.016S / cm Example 2 2.3nm 2.2nm 0.015S / cm Example 3 3.1nm 2.8nm 0.018S / cm Example 4 3.4nm 3.5nm 0.013S / cm Example 5 3.5nm 3.3nm 0.021S / cm Example 6 4.1nm 4.1nm 0.011S / cm Comparative Example 1 80nm 100nm 0.005S / cm Comparative Example 2 105nm 90nm 0.003S / cm

[0099] Table 1

[0100] As shown in Table 1, Examples 1-6 all yielded carbon-coated tungsten oxide quantum dot materials with small particle size and narrow particle size distribution, while Comparative Examples 1 and 2 had larger particle size and wider particle size distribution. This is because the comparative examples first heated and dried the polyol solution of tungsten oxide quantum dots, followed by high-temperature heat treatment to obtain the carbon coating layer. This caused the tungsten oxide quantum dots to agglomerate and grow in size during heating, resulting in a larger particle size and wider particle size distribution of the carbon-coated tungsten oxide material. In contrast, Examples 1-6 directly spray-pyrolyzed the tungsten oxide quantum dot solution, causing the polyol to carbonize in situ and distribute evenly on the outside of the tungsten oxide quantum dots. The preparation method of carbon-coated tungsten oxide quantum dots used in these examples is advanced.

[0101] Depend on Figure 3-8 It can be seen that the carbon-coated tungsten oxide quantum dot material obtained in the embodiments of the present invention has small particle size and good dispersibility. Figure 9-10 As can be seen, the carbon-coated tungsten oxide quantum dot material obtained in the comparative example of this invention has large particles and exhibits obvious agglomeration. This is because the carbon coating in the embodiments of this invention is performed by spray pyrolysis, resulting in higher uniformity.

[0102] Depend on Figure 11 It can be seen that the carbon-coated tungsten oxide quantum dots of Example 1 of the present invention have a narrow particle size distribution, concentrated between 1.5nm and 3.5nm, and there are no excessively small or large particles.

[0103] Example 7

[0104] The first step is to add tungstic acid to the ethylene glycol solution to obtain a 0.5 mol / L mixture.

[0105] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 350W and a temperature of 80℃ for 1.5 hours. This allows the tungstic acid to decompose into tungsten oxide, and the oxygen atoms of the tungsten oxide to coordinate with the hydroxyl groups of the ethylene glycol solution to obtain the reaction precursor solution.

[0106] The third step involves increasing the microwave reaction power to 600W and the temperature to 140℃, and then keeping the precursor solution at this temperature for 5 hours. This allows the tungsten oxide nuclei to grow in the ethylene glycol solution, resulting in an ethylene glycol solution of tungsten oxide quantum dots.

[0107] The fourth step involves spray-pyrolyzing an ethylene glycol solution containing tungsten oxide quantum dots under a nitrogen atmosphere, thereby carbonizing the ethylene glycol to obtain carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.1 MPa, the temperature is 300 °C, and the flow rate of the ethylene glycol solution containing tungsten oxide quantum dots is 5 L / h.

[0108] Example 8

[0109] The first step is to add ammonium metatungstate to a propylene glycol solution to obtain a 1 mol / L mixture.

[0110] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 450W and a temperature of 110℃ for 1 hour, allowing ammonium metatungstate to decompose into tungsten oxide. The oxygen atoms of the tungsten oxide then coordinate with the hydroxyl groups of the propylene glycol solution to obtain the reaction precursor solution.

[0111] The third step involves increasing the microwave reaction power to 700W and the temperature to 150℃, and then keeping the precursor solution at this temperature for 7 hours. This allows the tungsten oxide nuclei to grow in the propylene glycol solution, resulting in a propylene glycol solution of tungsten oxide quantum dots.

[0112] The fourth step involves spray-pyrolyzing a propylene glycol solution containing tungsten oxide quantum dots under a nitrogen atmosphere to carbonize the propylene glycol, thereby obtaining carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.2 MPa, the temperature is 400 °C, and the flow rate of the propylene glycol solution containing tungsten oxide quantum dots is 20 L / h.

[0113] Example 9

[0114] The first step is to add ammonium paratungstate to the glycerol solution to obtain a 2 mol / L mixture.

[0115] The second step involves placing the mixture in a microwave reactor and maintaining it at a microwave reaction power of 400W and a temperature of 100℃ for 2 hours. This allows ammonium paratungstate to decompose into tungsten oxide upon heating. The oxygen atoms of the tungsten oxide then coordinate with the hydroxyl groups of the glycerol solution to obtain the reaction precursor solution.

[0116] The third step involves increasing the microwave reaction power to 900W and the temperature to 170℃, and then keeping the precursor solution at this temperature for 8 hours. This allows the tungsten oxide nuclei to grow in the glycerol solution, resulting in a glycerol solution of tungsten oxide quantum dots.

[0117] The fourth step involves spray-pyrolyzing a glycerol solution containing tungsten oxide quantum dots under an argon atmosphere to carbonize the glycerol, thereby obtaining carbon-coated tungsten oxide quantum dot material. The spray-pyrolysis pressure is 0.6 MPa, the temperature is 500 °C, and the flow rate of the glycerol solution containing the tungsten oxide quantum dots is 13 L / h.

[0118] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-coated tungsten oxide quantum dot material, characterized in that, The preparation method comprises: adding a tungsten source into a polyol solution to obtain a mixed solution, and placing the mixed solution in a microwave reactor, and keeping the mixed solution at a first temperature under a first reaction power for a first time, so that the tungsten source is decomposed into tungsten oxide under heat, and the oxygen atoms of the tungsten oxide are coordinated with the hydroxyl groups of the polyol solution to obtain a reaction precursor solution; keeping the reaction precursor solution at a second temperature under a second reaction power for a second time, so that the crystal nucleus of the tungsten oxide grows in the polyol solution to obtain a polyol solution of tungsten oxide quantum dots; under an inert atmosphere, the polyol solution of tungsten oxide quantum dots is subjected to spray pyrolysis, so that the polyol is carbonized and coated on the outer surface of the tungsten oxide quantum dots to obtain a carbon-coated tungsten oxide quantum dot material.

2. The production method according to claim 1, characterized by, The tungsten source comprises one or more of ammonium tungstate, tungstic acid, ammonium metatungstate, and ammonium paratungstate.

3. The production method according to claim 1, characterized by, The polyol comprises one or more of ethylene glycol, propylene glycol, and glycerol.

4. The method of claim 1, wherein, The concentration of the tungsten source in the mixed solution is 0.5 mol / L-4 mol / L.

5. The preparation method according to claim 1, characterized in that, The first reaction power is 300 W-500 W, the first temperature is 80℃-120℃, and the first time is 0.5 h-2 h; the second reaction power is 600 W-1000 W, the second temperature is 140℃-180℃, and the second time is 5 h-8 h.

6. The method of claim 1, wherein, The pressure of the spray pyrolysis is 0.1 MPa-0.6 MPa, the temperature is 300℃-800℃, and the flow rate of the polyol solution of tungsten oxide quantum dots is 5 L / h-20 L / h.

7. A carbon-coated tungsten oxide quantum dot material, characterized in that, The carbon-coated tungsten oxide quantum dot material is prepared by the preparation method of any one of claims 1-6; the structure of the carbon-coated tungsten oxide quantum dot material comprises an outer shell and a core; the outer shell is a carbon coating layer, the core is located inside the carbon coating layer, and the core is a tungsten oxide quantum dot. 8.The carbon-coated tungsten oxide quantum dot material of claim 7, wherein, The thickness of the carbon coating layer is 1 nm-8 nm, and the size of the tungsten oxide quantum dot is 1 nm-5 nm.

9. A catalytic and electrode material, characterized in that The catalytic and electrode materials comprise the carbon-coated tungsten oxide quantum dot material of any one of claims 7-8.

10. Use of a catalytic and electrode material as claimed in claim 9, characterized in that The catalytic material is used for photocatalysis and thermal catalysis, and the electrode material is used for electrochemical catalysis and electrochemical energy storage devices.

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