A few-layer amorphous MoO 3-x Nanosheets and their preparation methods

Abstract

This invention discloses a few-layer amorphous MoO 3‑x This invention relates to nanosheets and their preparation methods, belonging to the technical field of amorphous molybdenum oxide nanomaterial preparation. The invention involves microwave calcination of molybdenite or molybdenum disulfide powder to obtain molybdenum oxide crystals; then, the molybdenum oxide crystals are mixed with a mixed solution of water, ethanol, and hydrogen peroxide, and stirred in an ice-water bath to form a suspension; the suspension is subjected to a microwave hydrothermal reaction while simultaneously applying ultrasound, followed by cooling and centrifugation to obtain amorphous few-layer MoO₂. 3‑x Nanosheet dispersion, then dried to obtain few-layer amorphous MoO 3‑x Nanosheets. Amorphous molybdenum oxide nanosheets can be obtained, with the number of layers controllable to within two. The method used in this invention has the advantages of simple operation, short synthesis cycle, low cost, environmental friendliness, and high product quality.

Description

Technical Field

[0001] This invention relates to a few-layer amorphous MoO 3-x The nanosheets and their preparation methods belong to the field of amorphous molybdenum oxide nanomaterial preparation technology. Background Technology

[0002] Two-dimensional layered transition metal oxide nanomaterials have been widely used in sensing, catalysis, and optoelectronics due to their excellent properties. Molybdenum oxide nanosheets, with their unique two-dimensional layered structure, high specific surface area, and tunable electronic properties, show great promise for applications in photocatalysis, electrochemical energy storage, gas sensors, and flexible electronic devices. Amorphous two-dimensional MoO3 has numerous unsaturated coordination sites on its surface, which can significantly enhance catalytic activity (such as photocatalytic degradation of organic pollutants and electrocatalytic hydrogen evolution). Furthermore, the amorphous layered structure facilitates rapid ion insertion / extraction, making it suitable as an electrode material for high-performance lithium-ion batteries or supercapacitors.

[0003] However, existing technologies mainly focus on the synthesis of crystalline MoO3 nanosheets, with relatively limited research on the direct synthesis of amorphous MoO3 nanosheets. For example, while hydrothermal synthesis and chemical vapor deposition can prepare crystalline MoO3 nanosheets, they have limitations in the preparation of amorphous structures. Amorphous MoO3 can be obtained by high-temperature pyrolysis of molybdate precursors, but the high temperatures easily lead to material agglomeration, making it difficult to control the nanosheet thickness. Reducing crystalline MoO3 with strong reducing agents (such as ascorbic acid) can yield amorphous structures, but the reduction process is uncontrollable and easily introduces impurities or excessive reduction to generate low-valence molybdenum oxides (such as MoO2). Other processes involve toxic reagents (such as concentrated nitric acid) or complex post-processing steps (such as phototreatment), which do not meet the requirements of green chemistry. Moreover, the reliance on high-purity raw materials (such as metallic molybdenum powder) significantly increases production costs, hindering industrial applications.

[0004] Existing technologies for synthesizing amorphous MoO3 two-dimensional nanosheets are often limited to relatively thick layers, involve complex processes, and require high-purity raw materials and high-temperature, strong reducing agent conditions, which increase the difficulty and cost of preparation. To address these issues, there is an urgent need to develop a simple and controllable method for preparing few-layer amorphous molybdenum oxide nanosheets using readily available raw materials, achieving simultaneous control of the amorphous structure and few-layer nanosheets under mild conditions to meet the demands for high-performance materials in fields such as catalysis, energy storage, and sensing. Summary of the Invention

[0005] To overcome the problems in the prior art, the present invention aims to provide a few-layer amorphous MoO. 3-x Nanosheets and their preparation methods.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A few-layer amorphous MoO 3-x The preparation method of nanosheets includes the following steps:

[0008] (1) Microwave roasting of molybdenite or molybdenum disulfide powder to obtain molybdenum oxide crystals;

[0009] (2) Mix molybdenum oxide crystals with a mixture of water, ethanol and hydrogen peroxide solution, and stir in an ice-water bath to form a suspension;

[0010] (3) The suspension was subjected to a hydrothermal reaction while being sonicated. After the reaction was completed, the suspension was cooled and centrifuged to obtain amorphous few-layer MoO. 3-x Nanosheet dispersion, then dried to obtain few-layer amorphous MoO 3-x Nanosheets, where x < 3.

[0011] Compared to conventional roasting, the microwave roasting method used in this invention ensures high purity of molybdenum oxide obtained from molybdenite or molybdenum disulfide powder, while avoiding the generation of impurities.

[0012] More preferably, in step (1), the microwave power of microwave roasting is 800-1600W, the microwave frequency is 2.45GHz, and the time is 30-60min.

[0013] More preferably, in step (2), the volume ratio of water, ethanol and hydrogen peroxide solution is (40~60):(40~60):(5~30); and the mass fraction of hydrogen peroxide solution is 30%.

[0014] This invention uses a mixed solution of water, ethanol, and hydrogen peroxide as a solvent, which enables the formation of few-layer MoO₂. 3-x The formation of nanosheets, on the other hand, simultaneously generates amorphous MoO. 3-x Nanosheets. Without any one of these components, amorphous few-layer two-dimensional MoO₂ cannot be obtained. 3-x Nanosheets. If the mixed solution of water, ethanol, and hydrogen peroxide is replaced with a mixed solution of acetonitrile, water, and ethanol, amorphous MoO cannot be achieved. 3-x The formation of nanosheets.

[0015] More preferably, the mass-to-volume ratio of the molybdenum oxide crystals to the mixed solution is (30-80) mg:(80-150) mL.

[0016] More preferably, the temperature of the ice-water bath is 0-10°C, and the stirring time in the ice-water bath is 20-40 min.

[0017] This invention uses ice-water bath treatment, which is beneficial to MoO2. 3-x Subsequent exfoliation of nanosheets, especially exfoliation into few-layer or single-layer materials.

[0018] More preferably, the heating time of the hydrothermal reaction is 5-10 minutes, the temperature is 130-150°C, the holding time is 3-9 hours, and the microwave power is adjusted by the system in real time according to the temperature, generally fluctuating between 0-500 W.

[0019] More preferably, the power of the ultrasound is 500-1500W.

[0020] More preferably, the centrifugation speed is 8000-1000 rpm and the time is 10-30 min.

[0021] More preferably, the drying temperature is 60-100°C and the time is 2-3 hours.

[0022] This invention also protects the few-layer amorphous MoO 3-x Few-layer amorphous MoO prepared by nanosheet preparation method 3-x Nanosheets.

[0023] Preferably, the few-layer amorphous MoO 3-x The nanosheets have no more than 3 molecular layers and a thickness of 1.4-3 nm.

[0024] More preferably, the few-layer amorphous MoO 3-x The nanosheets are 1.4-1.6 nm thick and consist of a single layer.

[0025] The beneficial effects of this invention are as follows: This invention uses microwave, ice-water bath dispersion, and hydrothermal ultrasonic treatment to process molybdenum-containing precursors to obtain amorphous molybdenum oxide nanosheets, with the number of layers controllable to within 3 layers, and even to prepare monolayer materials. The few-layer amorphous molybdenum oxide nanosheets of this invention have a positive effect on Ag... + It exhibits strong reducing adsorption, thereby adsorbing silver ions in water. The method used in this invention has the advantages of simple operation, short synthesis cycle, low cost, environmental friendliness, and high product quality. Attached Figure Description

[0026] Figure 1 It is a few-layer amorphous MoO 3-x Flowchart of nanosheet preparation.

[0027] Figure 2 The monolayer amorphous MoO prepared in Example 1 3-x AFM image of nanosheets.

[0028] Figure 3 The monolayer amorphous MoO prepared in Example 1 3-x XRD pattern of nanosheets.

[0029] Figure 4 The monolayer amorphous MoO prepared in Example 1 3-xXPS (Mo element) plot of nanosheets.

[0030] Figure 5 The monolayer amorphous MoO prepared in Example 1 3-x XPS (O element) plot of nanosheets. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Example 1

[0032] like Figure 1 As shown, a few-layer amorphous MoO 3-x The preparation method of nanosheets includes the following steps:

[0033] (1) Preparation of molybdenum oxide crystals: dry molybdenite was ground to 200 mesh, 5 g was placed in an alumina crucible with a thickness of 2 cm, the crucible was placed in a dual-frequency microwave cavity, and calcined in ambient air for 30 min under microwave power of 800 W and frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of over 99.5%.

[0034] (2) Stirring and dispersing: Mix 30 mg of molybdenum oxide crystals prepared in step (1) with water, ethanol and hydrogen peroxide in a volume ratio of 40 mL: 40 mL: 5 mL, stir in an ice-water bath at 5°C for 20 min to form a milky white suspension.

[0035] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor. The microwave power fluctuated within 0-500 W, and the temperature was raised to 130 °C in 5 min and maintained for 9 h. During this process, 500 W of ultrasonic power was added to promote the reaction. After the reaction was completed, the mixture was cooled for 40 min.

[0036] (4) Centrifugation: After centrifuging the dispersion obtained in step (3) at 9000 rpm for 15 minutes, take 2 / 3 of the upper layer to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0037] (5) Drying: The dispersion was dried at 80°C for 2 h to obtain a deep blue amorphous few-layer MoO3-x nanosheet solid.

[0038] according to Figure 2 It can be seen that the MoO3-x nanosheets prepared in Example 1 have a uniform thickness, are monolayer materials with a thickness of 1.4-1.6 nm, have a complete structure, and have a lateral size of about 400-1000 nm.

[0039] Figure 3The X-ray diffraction pattern of MoO3-x nanosheets prepared in Example 1 of this invention shows that no sharp peaks of crystalline state are observed, only broad peaks of amorphous state are present, indicating that the nanosheets have an amorphous structure.

[0040] Figure 4 This is the XPS (Mo elemental) spectrum of MoO3-x nanosheets prepared in Example 1 of this invention. The two characteristic peaks of the high-resolution XPS spectrum of Mo 3d at 236.2 and 233.0 eV represent Mo, respectively. 6+ 3D 3 / 2 and Mo 6+ 3D 5 / 2 The two characteristic peaks at 234.9 and 231.2 eV correspond to Mo. 5+ 3D 3 / 2 and Mo 5+ 3D 5 / 2 This result indicates that molybdenum oxide nanosheets exhibit two valence states of molybdenum, which is attributed to the formation of oxygen vacancies during the preparation process.

[0041] Figure 5 This is the XPS (O element) image of the MoO3-x nanosheets prepared in Example 1 of this invention. The characteristic peak of O 1s at 522.0 eV confirms the formation of oxygen vacancies.

[0042] Take 30 mg of the amorphous few-layer MoO3-x nanosheet solid prepared in Example 1 and put it into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm. Shake at 150 times / min for 10 h on an oscillator. After the shaking is completed, separate the liquid using a 20 nm filter membrane and detect the concentration of the filtrate using ICP-MS.

[0043] The amorphous few-layer MoO3-x nanosheets prepared in this embodiment are effective against Ag. + The adsorption rate reached 99.25%. This indicates that the amorphous few-layer MoO3-x nanosheets prepared in this invention can be used as an adsorbent for Ag. + It exhibits strong reducing adsorption properties, capable of adsorbing and reducing silver ions in the adsorbent MoO2. 3-x On the nanosheets, silver ions in the water are adsorbed. Example 2

[0044] A few-layer amorphous MoO 3-x The preparation method of nanosheets includes the following steps:

[0045] (1) Preparation of molybdenum oxide crystals: dry molybdenum disulfide was ground to 200 mesh, 10 g was placed in an alumina crucible with a thickness of 4 cm, the crucible was placed in a dual-frequency microwave cavity, and calcined in ambient air for 40 min under microwave power of 1200 W and frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of over 99.5%.

[0046] (2) Stirring and dispersing: Mix 50 mg of molybdenum oxide crystals prepared in step (1) with water, ethanol and hydrogen peroxide in a volume ratio of 50 mL: 50 mL: 20 mL, stir in an ice-water bath at 0°C for 30 min to form a milky white suspension.

[0047] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor. The microwave power fluctuated within 0-500 W, and the temperature was raised to 140 °C in 10 min and maintained for 3 h. During this process, 500 W of ultrasonic power was added to promote the reaction. After the reaction was completed, the mixture was cooled for 60 min.

[0048] (4) Centrifugation: After centrifuging the dispersion obtained in step (3) at 8000 rpm for 30 minutes, take 2 / 3 of the upper layer to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0049] (5) Drying: Dry the dispersion at 70°C for 3 h to obtain amorphous few-layer MoO3-x nanosheet solids with a thickness of 2-3 nm, a molecular layer thickness of 2, and a transverse dimension of 700-1200 nm.

[0050] Take 30 mg of the amorphous few-layer MoO3-x nanosheet solid prepared in Example 2 and put it into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm. Shake at 150 times / min for 10 h on an oscillator. After the oscillation, separate the liquid using a 20 nm filter membrane and detect the concentration of the filtrate using ICP-MS.

[0051] The amorphous few-layer MoO3-x nanosheets prepared in this embodiment are effective against Ag. + The adsorption rate reached 90.43%. Example 3

[0052] A few-layer amorphous MoO 3-x The preparation method of nanosheets includes the following steps:

[0053] (1) Preparation of molybdenum oxide crystals: dry molybdenite was ground to 200 mesh, 15 g was placed in an alumina crucible with a thickness of 4 cm, the crucible was placed in a dual-frequency microwave cavity, and calcined in ambient air for 60 min under microwave power of 1600 W and frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of over 99.5%.

[0054] (2) Stirring and dispersing: 80 mg of molybdenum oxide crystals prepared in step (1) are mixed with water, ethanol and hydrogen peroxide in a volume ratio of 60 mL: 60 mL: 30 mL, and stirred in an ice-water bath at 10°C for 40 min to form a milky white suspension.

[0055] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor. The microwave power fluctuated within 0-500 W, and the temperature was raised to 150 °C in 10 min and maintained for 7 h. During this process, ultrasonic power of 1500 W was added to promote the reaction. After the reaction was completed, the mixture was cooled for 30 min.

[0056] (4) Centrifugation: After centrifuging the dispersion obtained in step (3) at 1000 rpm for 10 minutes, take 2 / 3 of the upper layer to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0057] (5) Drying: The dispersion was dried at 100℃ for 2 h to finally obtain a deep blue amorphous few-layer MoO3-x nanosheet solid.

[0058] Example 3 yielded amorphous few-layer MoO3-x nanosheets with a thickness of 2-3 nm (2 molecular layers) and a lateral dimension of 600-1000 nm.

[0059] Take 30 mg of the amorphous few-layer MoO3-x nanosheet solid prepared in Example 3 and put it into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm. Shake at 150 times / min for 10 h on an oscillator. After the shaking is completed, separate the liquid using a 20 nm filter membrane and detect the concentration of the filtrate using ICP-MS.

[0060] The amorphous few-layer MoO3-x nanosheets prepared in this embodiment are effective against Ag. + The adsorption rate reached 95.75%.

[0061] Comparative Example 1

[0062] The few-layer amorphous MoO2 described in this comparative example 3-x The only difference between the preparation method of the nanosheets and Example 1 is that in step (2), the mixed solution is ethanol and hydrogen peroxide solution, with the volume of ethanol being 80 mL and the volume of hydrogen peroxide solution being 10 mL.

[0063] Characterized by AFM, the material prepared in Comparative Example 1 was thicker, with a thickness of 16-20 nm.

[0064] Take 30 mg of the material prepared in Comparative Example 1 and put it into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm. Shake at a speed of 150 times / min for 10 h on a shaker. After the shaking is completed, separate the liquid using a 20 nm filter membrane and detect the concentration of the filtrate using ICP-MS.

[0065] The material prepared in Comparative Example 1 was effective against 1 ppm Ag + The adsorption rate of the aqueous solution was 63.37%.

[0066] Comparative Example 2

[0067] The few-layer amorphous MoO2 described in this comparative example 3-x The only difference between the preparation method of the nanosheets and Example 1 is that in step (2), the mixed solution is ethanol and water, with ethanol having a volume of 40 mL and water having a volume of 40 mL.

[0068] Characterized by AFM, the material prepared in Comparative Example 2 had a thickness of 4-6 nm, with only a portion being converted to amorphous.

[0069] Take 30 mg of the material prepared in Comparative Example 2 and add it to 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm. Shake the solution at a speed of 150 times / min for 10 h. After the shaking is completed, separate the liquid using a 20 nm filter membrane and detect the concentration of the filtrate using ICP-MS.

[0070] The material prepared in Comparative Example 2 was effective against 1 ppm Ag + The adsorption rate of the aqueous solution was 29.64%.

[0071] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A few-layer amorphous MoO 3-x The method for preparing nanosheets is characterized by: Includes the following steps: (1) Microwave roasting of molybdenite or molybdenum disulfide powder to obtain molybdenum oxide crystals; (2) Mix molybdenum oxide crystals with a mixture of water, ethanol and hydrogen peroxide solution, and stir in an ice-water bath to form a suspension; wherein the volume ratio of water, ethanol and hydrogen peroxide solution is (40~60):(40~60):(5~30); (3) The suspension was subjected to microwave hydrothermal reaction while being sonicated. After the reaction was completed, the suspension was cooled and centrifuged to obtain amorphous few-layer MoO. 3-x Nanosheet dispersion, then dried to obtain few-layer amorphous MoO 3-x Nanosheets, where x < 3; The few-layer amorphous MoO 3-x The thickness of the nanosheets is less than 3 molecular layers.

2. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: In step (1), the microwave power of microwave roasting is 800-1600W, the microwave frequency is 2.45 GHz, the temperature is 800-1200℃, and the time is 30-60min.

3. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: In step (2), the mass fraction of the hydrogen peroxide solution is 30%.

4. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: The mass-to-volume ratio of the molybdenum oxide crystals to the mixed solution is (30-80) mg:(80-150) mL.

5. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: The temperature of the ice-water bath is 0-10℃, and the stirring time in the ice-water bath is 20-40 minutes.

6. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: The microwave hydrothermal reaction has a heating time of 5-10 minutes, a temperature of 130-150℃, and a holding time of 3-9 hours.

7. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: The power of the ultrasound is 500-1500W.

8. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: The centrifugation speed is 8000-1000 rpm, and the time is 10-30 min.

9. The few-layer amorphous MoO according to any one of claims 1-8 3-x Few-layer amorphous MoO prepared by nanosheet preparation method 3-x Nanosheets.

10. The few-layer amorphous MoO according to claim 9 3-x Nanosheets, characterized by: The few-layer amorphous MoO 3-x The thickness of the nanosheets is less than 3 molecular layers.

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