Few-layer amorphous MoO3-x nanosheet and preparation method thereof

Abstract

The invention discloses a few-layer amorphous MoO3-x nanosheet and a preparation method thereof, and belongs to the technical field of preparation of amorphous molybdenum oxide nanomaterials. Molybdenite or molybdenum disulfide powder is subjected to microwave roasting, and molybdenum oxide crystals are obtained; mixing the molybdenum oxide crystal with a mixed solution of water, ethanol and hydrogen peroxide, and stirring in an ice-water bath to form a suspension; and carrying out microwave hydrothermal reaction on the turbid liquid, simultaneously applying ultrasonic waves, cooling and centrifugally separating to obtain an amorphous few-layer MoO3-x nanosheet dispersion liquid after the reaction is finished, and then drying to obtain the few-layer amorphous MoO3-x nanosheet. The amorphous molybdenum oxide nanosheet is obtained, and the number of layers can be controlled within two. The method disclosed by the invention has the advantages of simplicity in operation, short synthesis period, low cost, environment friendliness, high product quality and the like.

Description

Technical Field

[0001] The present invention relates to a few-layer amorphous MoO 3-x The invention discloses a nanosheet and a preparation method thereof, belonging to the technical field of preparation of amorphous molybdenum oxide nanomaterials. Background Art

[0002] Two-dimensional layered transition metal oxide nanomaterials have been widely used in sensing, catalysis, optoelectronics and other fields due to their excellent performance. Molybdenum oxide nanosheets have shown broad application prospects in photocatalysis, electrochemical energy storage, gas sensors and flexible electronic devices due to their unique two-dimensional layered structure, high specific surface area and adjustable electronic properties. There are a large number of unsaturated coordination sites on the surface of amorphous two-dimensional MoO3, which can significantly improve the catalytic activity (such as photocatalytic degradation of organic pollutants and electrocatalytic hydrogen evolution). In addition, the amorphous layered structure is conducive to the rapid insertion / extraction of ions, which is suitable for high-performance lithium-ion batteries or supercapacitor electrode materials.

[0003] However, existing technologies are mainly aimed at the synthesis of crystalline MoO3 nanosheets, and the direct synthesis of amorphous MoO3 nanosheets is relatively limited. For example, although 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 high temperature conditions easily lead to material agglomeration and it is difficult to control the thickness of nanosheets. Although amorphous structures can be obtained by reducing crystalline MoO3 with strong reducing agents (such as ascorbic acid), the reduction process is uncontrollable and it is easy to introduce impurities or over-reduction to generate low-valent molybdenum oxides (such as MoO2). Other processes involve toxic reagents (such as concentrated nitric acid) or complex post-processing steps (such as light treatment), 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, restricting industrial applications.

[0004] The existing technology for the synthesis of amorphous MoO3 two-dimensional nanosheets is often limited to relatively thick thickness, the process is complicated, and the high-purity raw materials, high temperature, and strong reducing agent conditions increase the difficulty and cost of preparation. In view of the above problems, it is urgent to develop a method for preparing amorphous MoO3 nanosheets with few layers of raw materials that are easy to obtain and simple to control, so as to achieve the simultaneous regulation of amorphous structure and few-layer nanosheets under mild conditions, so as to meet the demand for high-performance materials in the fields of catalysis, energy storage, and sensing. Summary of the invention

[0005] In order to overcome the problems in the background technology, the present invention aims to provide a few-layer amorphous MoO 3-x Nanosheets and methods for preparing the same.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions: A few-layer amorphous MoO3-x The method for preparing the nanosheets comprises the following steps: (1) subjecting molybdenite or molybdenum disulfide powder to microwave roasting to obtain molybdenum oxide crystals; (2) mixing the molybdenum oxide crystals with a mixed solution of water, ethanol and hydrogen peroxide solution, and stirring in an ice water bath to form a suspension; (3) The suspension is subjected to a hydrothermal reaction while being subjected to ultrasound. After the reaction, it is cooled and centrifuged to obtain amorphous few-layer MoO 3-x Nanosheet dispersion, and then dried to obtain few-layer amorphous MoO 3-x Nanosheets, where x<3.

[0007] Compared with common roasting, the microwave roasting in the present invention can ensure that the molybdenum oxide obtained from the raw material of molybdenite or molybdenum disulfide powder has high purity and avoids the generation of impurities.

[0008] More preferably, in step (1), the microwave power of the microwave roasting is 800-1600 W, the microwave frequency is 2.45 GHz, and the time is 30-60 min.

[0009] 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%.

[0010] The present invention adopts a mixed solution of water, ethanol and hydrogen peroxide solution as a solvent, which can realize the formation of few-layer MoO 3-x The formation of nanosheets and the simultaneous formation of amorphous MoO 3-x If any one of them is missing, amorphous few-layer two-dimensional MoO 3-x If the mixed solution of water, ethanol and hydrogen peroxide solution is replaced by a mixed solution of acetonitrile, water and ethanol, amorphous MoO 3-x Generation of nanosheets.

[0011] More preferably, the mass volume ratio of the molybdenum oxide crystals to the mixed solution is (30-80) mg: (80-150) mL.

[0012] More preferably, the temperature of the ice-water bath is 0-10° C., and the stirring time of the ice-water bath is 20-40 min.

[0013] The present invention adopts ice water bath treatment to facilitate the MoO 3-x Subsequent exfoliation of nanosheets, especially exfoliation into few-layer or single-layer materials.

[0014] More preferably, the heating time of the hydrothermal reaction is 5-10 min, the temperature is 130-150° C., the insulation time is 3-9 h, and the microwave power is regulated by the system in real time according to the temperature, generally fluctuating between 0-500 W.

[0015] More preferably, the power of the ultrasound is 500-1500W.

[0016] More preferably, the centrifugal speed is 8000-1000 rpm and the time is 10-30 min.

[0017] More preferably, the drying temperature is 60-100° C. and the drying time is 2-3 hours.

[0018] The present invention also protects the few-layer amorphous MoO 3-x Few-layer amorphous MoO prepared by the method for preparing nanosheets 3-x Nanosheets.

[0019] Preferably, the few-layer amorphous MoO 3-x The number of nanosheets is within 3 molecular layers and the thickness is 1.4-3nm.

[0020] More preferably, the few-layer amorphous MoO 3-x The thickness of the nanosheets is 1.4-1.6nm and the number of layers is a monomolecular layer.

[0021] Beneficial effects of the present invention: The present invention uses microwave method, ice-water bath dispersion and hydrothermal ultrasonic treatment to treat the molybdenum-containing precursor to obtain amorphous molybdenum oxide nanosheets, and the number of layers can be controlled within 3 layers, and even a single-molecule layer material can be prepared. The few-layer amorphous molybdenum oxide nanosheets of the present invention have a good effect on Ag + It exhibits strong reductive adsorption, and further adsorbs silver ions in water. The method adopted by the present invention has the advantages of simple operation, short synthesis cycle, low cost, environmental protection, greenness, high product quality, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Few-layer amorphous MoO 3-x Flow chart of the preparation of nanosheets.

[0023] Figure 2 The single-layer amorphous MoO prepared in Example 1 3-x AFM image of the nanosheets.

[0024] Figure 3 The single-layer amorphous MoO prepared in Example 1 3-x XRD patterns of nanosheets.

[0025] Figure 4 The single-layer amorphous MoO prepared in Example 1 3-xXPS (Mo element) image of nanosheets.

[0026] Figure 5 The single-layer amorphous MoO prepared in Example 1 3-x XPS (O element) image of nanosheets. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto. Example 1

[0028] like Figure 1 As shown, a few-layer amorphous MoO 3-x The method for preparing the nanosheets comprises the following steps: (1) Preparation of crystalline molybdenum oxide: Grind the dried molybdenite to 200 mesh, take 5 g and place it in an alumina crucible with a thickness of 2 cm. Place the crucible in a dual-frequency microwave cavity and calcine it in ambient air for 30 min at a microwave power of 800 W and a frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of more than 99.5%.

[0029] (2) Stirring and dispersing: Mix 30 mg of the molybdenum oxide crystals prepared in step (1) with water, ethanol, and hydrogen peroxide in a volume ratio of 40 mL:40 mL:5 mL, and stir in a 5°C ice-water bath for 20 min to form a milky white suspension.

[0030] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor, and the microwave power was fluctuated within the range of 0-500 W. The temperature was raised to 130 °C in 5 min and maintained for 9 h. During this process, ultrasound with a power of 500 W was added to promote the reaction. After the reaction was completed, the reaction was cooled for 40 min.

[0031] (4) Centrifugation: The dispersion obtained in step (3) was centrifuged at 9000 rpm for 15 minutes, and 2 / 3 of the upper layer was taken to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0032] (5) Drying: The dispersion was dried at 80 °C for 2 h to obtain dark blue amorphous few-layer MoO3-x nanosheet solids.

[0033] according to Figure 2 It can be seen that the thickness of the MoO3-x nanosheets prepared in Example 1 is uniform, being a monolayer material with a thickness of 1.4-1.6 nm, the structure is complete, and the lateral size of the nanosheets is about 400-1000 nm.

[0034] Figure 3This is the X-ray diffraction pattern of the MoO3-x nanosheet prepared in Example 1 of the present invention. It can be seen that there is no sharp peak of the crystalline state, only a broad peak of the amorphous state, indicating that the nanosheet has an amorphous structure.

[0035] Figure 4 The XPS (Mo element) diagram of MoO3-x nanosheets prepared in Example 1 of the present invention shows that the two characteristic peaks of the high-resolution XPS spectrum of Mo 3d at 236.2 and 233.0 eV represent Mo 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 there are two valence states of molybdenum in MoO nanosheets, which is attributed to the formation of oxygen vacancies during the preparation process.

[0036] Figure 5 This is the XPS (O element) graph of the MoO3-x nanosheets prepared in Example 1 of the present invention. The characteristic peak of O 1s at 522.0 eV confirms the formation of oxygen vacancies.

[0037] 30 mg of amorphous few-layer MoO3-x nanosheet solid prepared in Example 1 was put into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm, and oscillated on an oscillator at a speed of 150 times / min for 10 h. After the end, the liquid was separated using a 20 nm filter membrane, and the filtrate concentration was detected using ICP-MS.

[0038] The amorphous few-layer MoO3-x nanosheets prepared in this example have a strong affinity for Ag. + The adsorption rate of the amorphous few-layer MoO3-x nanosheets prepared by the present invention can be used as an adsorbent for Ag + It exhibits strong reductive adsorption and can adsorb and reduce silver ions on the adsorbent MoO 3-x The nanosheets absorb silver ions in the water. Example 2

[0039] A few-layer amorphous MoO 3-x The method for preparing the nanosheets comprises the following steps: (1) Preparation of crystalline molybdenum oxide: Grind dried molybdenum disulfide to 200 mesh, take 10 g and place it in an alumina crucible with a thickness of 4 cm. Place the crucible in a dual-frequency microwave cavity and calcine it in ambient air for 40 min at a microwave power of 1200 W and a frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of more than 99.5%.

[0040] (2) Stirring and dispersing: Mix 50 mg of the molybdenum oxide crystals prepared in step (1) with water, ethanol, and hydrogen peroxide in a volume ratio of 50 mL: 50 mL: 20 mL, and stir in an ice-water bath at 0°C for 30 min to form a milky white suspension.

[0041] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor, the microwave power fluctuated within the range of 0-500 W, the temperature was raised to 140 °C in 10 min, and maintained for 3 h. During this process, 500 W of ultrasound was added to promote the reaction, and the reaction was cooled for 60 min after the reaction was completed.

[0042] (4) Centrifugation: The dispersion obtained in step (3) was centrifuged at 8000 rpm for 30 minutes, and 2 / 3 of the upper layer was taken to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0043] (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 thickness of 2 molecular layers, and a lateral size of 700-1200 nm.

[0044] 30 mg of amorphous few-layer MoO3-x nanosheet solid prepared in Example 2 was put into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm, and oscillated on an oscillator at a speed of 150 times / min for 10 h. After the end, the liquid was separated using a 20 nm filter membrane, and the filtrate concentration was detected using ICP-MS.

[0045] The amorphous few-layer MoO3-x nanosheets prepared in this example have a strong affinity for Ag. + The adsorption rate reached 90.43%. Example 3

[0046] A few-layer amorphous MoO 3-x The method for preparing the nanosheets comprises the following steps: (1) Preparation of crystalline molybdenum oxide: Grind the dried molybdenite to 200 mesh, take 15 g and place it in an alumina crucible with a thickness of 4 cm. Place the crucible in a dual-frequency microwave cavity and calcine it in ambient air for 60 min at a microwave power of 1600 W and a frequency of 2.45 GHz to obtain molybdenum oxide crystals with a purity of more than 99.5%.

[0047] (2) Stirring and dispersing: Mix 80 mg of the molybdenum oxide crystals prepared in step (1) with water, ethanol, and hydrogen peroxide in a volume ratio of 60 mL: 60 mL: 30 mL, and stir in an ice-water bath at 10°C for 40 min to form a milky white suspension.

[0048] (3) Microwave hydrothermal treatment: The suspension obtained in step (2) was transferred to a polytetrafluoroethylene high-pressure reactor, and the microwave power was fluctuated within the range of 0-500 W. The temperature was raised to 150 °C in 10 min and maintained for 7 h. During this process, ultrasound with a power of 1500 W was added to promote the reaction. After the reaction was completed, the reaction was cooled for 30 min.

[0049] (4) Centrifugation: The dispersion obtained in step (3) was centrifuged at 1000 rpm for 10 minutes, and 2 / 3 of the upper layer was taken to obtain an amorphous few-layer MoO rich in oxygen defects. 3-x Nanosheet dispersion.

[0050] (5) Drying: The dispersion was dried at 100 °C for 2 h to obtain dark blue amorphous few-layer MoO3-x nanosheet solids.

[0051] Example 3 obtains an amorphous few-layer MoO3-x nanosheet solid with a thickness of 2-3 nm (2 molecular layers) and a lateral size of 600-1000 nm.

[0052] 30 mg of amorphous few-layer MoO3-x nanosheet solid prepared in Example 3 was put into 200 mL of AgNO3 aqueous solution with a concentration of 1 ppm, and oscillated on an oscillator at a speed of 150 times / min for 10 h. After the end, the liquid was separated using a 20 nm filter membrane, and the filtrate concentration was detected using ICP-MS.

[0053] The amorphous few-layer MoO3-x nanosheets prepared in this example have a strong affinity for Ag. + The adsorption rate reached 95.75%.

[0054] Comparative Example 1 The few-layer amorphous MoO 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, the volume of ethanol is 80 mL, and the volume of hydrogen peroxide solution is 10 mL.

[0055] AFM characterization showed that the material prepared in Comparative Example 1 was thicker, with a thickness of 16-20 nm.

[0056] 30 mg of the material prepared in Comparative Example 1 was put into 200 mL of an AgNO3 aqueous solution with a concentration of 1 ppm, and oscillated on an oscillator at a speed of 150 times / min for 10 h. After the oscillation, the liquid was separated using a 20 nm filter membrane, and the concentration of the filtrate was detected using ICP-MS.

[0057] The material prepared in Comparative Example 1 was effective for 1 ppm Ag + The adsorption rate of aqueous solution is 63.37%.

[0058] Comparative Example 2 The few-layer amorphous MoO 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, the volume of ethanol is 40 mL, and the volume of water is 40 mL.

[0059] Using AFM characterization, the thickness of the material prepared in Comparative Example 2 was 4-6 nm, and only a portion of it was converted into amorphous.

[0060] 30 mg of the material prepared in Comparative Example 2 was put into 200 mL of an AgNO3 aqueous solution with a concentration of 1 ppm, and oscillated on an oscillator at a speed of 150 times / min for 10 h. After the oscillation, the liquid was separated using a 20 nm filter membrane, and the concentration of the filtrate was detected using ICP-MS.

[0061] The material prepared in Comparative Example 2 was effective for 1 ppm Ag + The adsorption rate of aqueous solution is 29.64%.

[0062] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than 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 in form and details 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: The steps include: (1) subjecting molybdenite or molybdenum disulfide powder to microwave roasting to obtain molybdenum oxide crystals; (2) mixing the molybdenum oxide crystals with a mixed solution of water, ethanol and hydrogen peroxide solution, and stirring in an ice water bath to form a suspension; (3) The suspension was subjected to microwave hydrothermal reaction and ultrasonic treatment, and then cooled and centrifuged to obtain amorphous few-layer MoO 3-x Nanosheet dispersion, and then dried to obtain few-layer amorphous MoO 3-x Nanosheets, where x<3.

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

3. The few-layer amorphous MoO according to claim 1 3-x The method for preparing nanosheets is characterized by: In the step (2), the volume ratio of water, ethanol and hydrogen peroxide solution is (40-60): (40-60): (5-30); 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 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°C, and the stirring time of 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° C., and a heat preservation 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 centrifugal 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 to 8 3-x Few-layer amorphous MoO prepared by the method for preparing nanosheets 3-x Nanosheets.

10. The few-layer amorphous MoO according to claim 9 3-x Nanosheets, characterized in that: The few-layer amorphous MoO 3-x The thickness of the nanosheet is within 3 molecular layers.

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