Two-dimensional Cr2Se3 nano material and preparation method and application thereof

Abstract

The invention particularly relates to a two-dimensional Cr2Se3 nano material as well as a preparation method and application thereof, and belongs to the technical field of functional nano materials. Aiming at the technical problem that the morphology and the size of a Cr2Se3 nano-material in the prior art are uncontrollable, the invention provides the hexagonal crystal phase Cr2Se3 nano-material, the nano-material is observed to be a hexagonal or polygonal flaky material under a transmission electron microscope, a multilevel structure can be formed through self-assembly, and the morphology and the size of the Cr2Se3 nano-material are not controllable. As a photocatalytic material, the photocatalyst provides abundant reaction sites and high specific surface area for the reaction process, and promotes substance and electron transport. The nanomaterial is prepared through solvothermal reaction, the steps are simple and convenient, and the nanomaterial has a good industrial prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional nanomaterials, and in particular relates to a two-dimensional Cr2Se3 nanomaterial, a preparation method of the nanomaterial and an application of the nanomaterial as a photocatalytic degradation material. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Two-dimensional nanomaterials have great application prospects in clean energy conversion, sensors and information storage due to their adjustable optical / electrical / thermal properties and structural changes, as well as thickness-dependent ferromagnetism / antiferromagnetism. Among many materials, chromium-based selenides, due to their diversity in crystal structure and elemental composition, have aroused widespread research enthusiasm in the fields of photoelectric and thermoelectric conversion, environmental pollutant purification, information storage and magnetic sensing.

[0004] At present, some studies have reported that Cr2Se3 can be prepared by mixing chromium powder and selenium powder, heating them to 1000℃ for 2 days, and then reacting them at 250℃ for 7 days using a high-temperature solid-phase reaction method. However, the high-temperature solid-phase reaction method for synthesizing Cr2Se3 not only consumes a lot of energy and takes a long time, but also the resulting product often exhibits the disadvantages of uncontrollable size and non-uniform morphology. Therefore, this greatly affects or limits the performance of Cr2Se3 and its application and industrial development in micro / nano devices. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a two-dimensional sheet-like Cr2Se3 nanomaterial, which is a hexagonal crystal phase, has high crystallinity, and has excellent light absorption ability and stable performance, and the preparation method is simple. Based on the above technical achievements, the present invention provides the following solutions: In a first aspect, the present invention provides a two-dimensional Cr2Se3 nanomaterial, which is a hexagonal crystal, and the main diffraction peaks in its XRD diffraction spectrum are respectively located at 30.8±0.1°, 32.6±0.1°, 42.6±0.1°, 50.7±0.1°, 56.1±0.1°, 61.7±0.1°, and 64.3±0.1°; the microscopic morphology is nano-scale flakes with a thickness of 2~5nm and a side length of 20~100nm.

[0006] Through transmission electron microscopy observation, the above Cr2Se3 nanomaterials are hexagonal or polygonal sheet materials. The advantage of this configuration is that during the preparation of the nanomaterial and the crystal growth process, the crystals are less likely to agglomerate, and the sheet nanomaterial can easily form a multi-level spatial structure through self-assembly, thereby increasing the specific surface area.

[0007] The second aspect of the present invention provides a method for preparing the two-dimensional Cr2Se3 nanomaterial according to the first aspect, comprising the following steps: The soluble chromium source and selenium source are added into a high-boiling-point reaction medium to carry out a solvent thermal reaction, and a solid reaction product is separated to obtain the product.

[0008] In the above solvent thermal reaction system, the molar ratio of Cr:Se elements should be close to 2:3, wherein the Se element can be appropriately excessive, and therefore, the preferred ratio is 1:1.5-3.

[0009] The above-mentioned soluble chromium source and selenium source are substances that are soluble in the reaction medium and can dissociate into chromium ions and selenium ions, including organic and inorganic compounds; feasible chromium sources include but are not limited to one or a combination of chromium acetylacetonate, chromium trichloride, chromium nitrate or chromium acetate; feasible selenium sources are one or a combination of diphenyl diselenide, dibenzyl diselenide, selenium dioxide or selenium powder.

[0010] In one embodiment provided by the present invention, the chromium source is chromium acetylacetonate, and the selenium source is diphenyl diselenide.

[0011] In another feasible embodiment, the chromium source is chromium acetate, and the selenium source is diphenyl diselenide.

[0012] In another feasible implementation manner, the chromium source is chromium trichloride, and the selenium source is diphenyl diselenide.

[0013] The high boiling point reaction medium is selected from one or a combination of organic amines, oleic acid, and octadecene, wherein the organic amine is selected from one or more of oleylamine, octadecylamine, or hexadecylamine; further, the high boiling point reaction medium is a mixture of organic amines and oleic acid in a volume ratio of 1 to 7:1.

[0014] The solvent thermal reaction includes a first stage and a second stage: in the first stage, the chromium source and selenium source are added to the reaction medium under an inert gas atmosphere, and then heated to 130-180°C for 30-90 minutes. The purpose of heating in this stage is to dissolve the chromium source and selenium source and remove oxygen, moisture and low-boiling impurities in the reaction system; in the second stage, the reaction system is heated to a temperature between 260-350°C, and the reaction time is controlled between 5-180 minutes. After the solvent thermal reaction is completed, the solid product in the reaction solution is separated by centrifugation or filtration, and then the solid product is washed with an organic reagent in turn to obtain the target product. Examples of the organic reagent are anhydrous ethanol and / or cyclohexane.

[0015] The two-dimensional Cr2Se3 nanomaterial has a self-assembled multi-level structure, which provides a larger specific surface area and more abundant active reaction sites than the Cr2Se3 in the prior art, which is conducive to improving the electron transmission in the catalytic reaction. The polygonal flakes self-assemble in space, increase the absorption of light from different directions, and improve the light absorption capacity of the material. The present invention has verified that under light conditions, the above nanomaterial has a good degradation ability for methylene blue in the water environment.

[0016] Therefore, the third aspect of the present invention is the use of the two-dimensional Cr2Se3 nanomaterial described in the first aspect as a photocatalytic degradation material.

[0017] Furthermore, the application is the degradation of dye pollutants in water environments, such as natural environments such as rivers, lakes, and seas, and also industrial and domestic water such as drinking water and treated sewage. The dyes include methyl blue, methylene blue, Sudan red, and the like.

[0018] In a fourth aspect, the present invention provides a method for degrading methylene blue in an aqueous environment, comprising dispersing the two-dimensional Cr2Se3 nanomaterial described in the first aspect into the aqueous environment to be treated.

[0019] The steps of the above-mentioned degradation method are as follows: the two-dimensional Cr2Se3 nanomaterial described in the first aspect is surface modified by mercaptopropionic acid to enhance its water solubility; the treated nanomaterial is dispersed into the water environment to be treated, dissolved by stirring, and then irradiated with light for a period of time.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The Cr2Se3 nanomaterial synthesized by the method of the present invention is a hexagonal crystal phase with high crystallinity and a hexagonal or polygonal sheet structure. The two-dimensional Cr2Se3 nanomaterial and its self-assembled multi-level structure can absorb the scattered or reflected incident light multiple times, thereby improving the light absorption capacity of the material.

[0021] 2. The two-dimensional Cr2Se3 nanomaterials are in the form of polygonal sheets and can self-assemble to form a multi-level structure, which can not only provide a larger specific surface area and accelerate mass transfer and electron transfer during the catalytic reaction, but also effectively avoid the problem of easy stacking and agglomeration between nanomaterials.

[0022] 3 Hexagonal Cr2Se3 is a non-layered crystal structure. When its morphology is a two-dimensional structure, it can provide abundant catalytic active sites due to the presence of surface dangling bonds.

[0023] 4. While exploring the light absorption performance of Cr2Se3 nanomaterials, the present invention also found that the above nanomaterials have good degradation ability for methylene blue dye. Based on the above performance, the nanomaterial can also be used as a photocatalyst to degrade dye pollutants in water environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is the X-ray diffraction pattern (XRD) of the target product of Example 1.

[0026] Figure 2 This is a transmission electron microscope (TEM) photograph of the target product of Example 1.

[0027] Figure 3 It is the ultraviolet visible near infrared (UV-vis-NIR) absorption spectrum of the target product of Example 1.

[0028] Figure 4 This is a curve chart of the photocatalytic degradation of methylene blue by the target product of Example 1.

[0029] Figure 5 This is the X-ray diffraction pattern (XRD) of the target product of Example 2.

[0030] Figure 6 This is a transmission electron microscope (TEM) photograph of the target product of Example 3.

[0031] Figure 7 This is the X-ray diffraction pattern (XRD) of the target product of Example 4. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0035] Example 1 In this embodiment, a two-dimensional Cr2Se3 nanomaterial is provided, and the preparation method thereof is as follows: (1) In a 100 ml three-necked flask, add 0.2 mmol of chromium acetylacetonate, 0.3 mmol of diphenyl diselenide, 4.0 ml of oleylamine and 4.0 ml of oleic acid to obtain a mixed solution.

[0036] (2) Nitrogen was introduced into the three-necked flask in step (1), and the mixed solution was heated to 130° C. under magnetic stirring for 90 min to remove moisture and low-boiling impurities in the reaction system.

[0037] (3) The mixed solution was heated to 320°C for 30 min. After the reaction was completed, the mixture was cooled to room temperature and the solid product in the reaction solution was separated by centrifugation. The solid product was then washed three times by centrifugation with cyclohexane and anhydrous ethanol respectively. The obtained solid product was the target product.

[0038] Example 2 In this embodiment, another two-dimensional Cr2Se3 nanomaterial is provided, and its preparation method is as follows: (1) In a 100 ml three-necked flask, add 0.2 mmol of chromium acetylacetonate, 0.3 mmol of diphenyl diselenide, 6.0 ml of oleylamine and 2.0 ml of oleic acid to obtain a mixed solution.

[0039] (2) Nitrogen was introduced into the three-necked flask in step (1), and the mixed solution was heated to 180° C. under magnetic stirring and kept reacting for 30 min to remove moisture and low-boiling impurities in the reaction system.

[0040] (3) The mixed solution was heated to 260°C for 180 min. After the reaction was completed, the mixture was cooled to room temperature and the solid product in the reaction solution was separated by centrifugation. The solid product was then washed three times by centrifugation with cyclohexane and anhydrous ethanol respectively. The obtained solid product was the target product.

[0041] Example 3 In this embodiment, another two-dimensional Cr2Se3 nanomaterial is provided, and its preparation method is as follows: (1) In a 100 ml three-necked flask, add 0.2 mmol of chromium acetylacetonate, 0.3 mmol of diphenyl diselenide, 7.0 ml of oleylamine and 1.0 ml of oleic acid to obtain a mixed solution.

[0042] (2) Nitrogen was introduced into the three-necked flask in step (1), and the mixed solution was heated to 160° C. under magnetic stirring for 60 min to remove moisture and low-boiling impurities in the reaction system.

[0043] (3) The mixed solution was heated to 350°C for 15 min. After the reaction was completed, the mixture was cooled to room temperature and the solid product in the reaction solution was separated by centrifugation. The solid product was then washed three times by centrifugation with cyclohexane and anhydrous ethanol respectively. The obtained solid product was the target product.

[0044] Example 4 In this embodiment, another two-dimensional Cr2Se3 nanomaterial is provided, which is different from the embodiment 1 in that: step (1) is performed as follows: 0.2 mmol chromium acetate, 0.3 mmol dibenzyl diselenide, 6.0 ml octadecylamine and 2.0 ml oleic acid are added to a 100 ml three-necked flask to obtain a mixed solution. The rest of the settings are the same as those in the embodiment 1.

[0045] Example 5 In this embodiment, another two-dimensional Cr2Se3 nanomaterial is provided, which is different from the embodiment 1 in that: step (1) is performed as follows: 0.2 mmol chromium trichloride, 0.3 mmol dibenzyl diselenide, 6.0 ml hexadecylamine and 2.0 ml oleic acid are added to a 100 ml three-necked flask to obtain a mixed solution. The rest of the settings are the same as those in the embodiment 1.

[0046] Composition, structure characterization and performance testing Figure 1 This is the X-ray diffraction pattern of the target product obtained in Example 1. It can be seen from the figure that all diffraction peaks indicate the corresponding crystal planes in Cr2Se3 (JCPDS Card No. 40-1404) well, and no other impurity peaks appear, indicating that the target product prepared in this example is a hexagonal Cr2Se3 crystal. Similarly, Figure 5 , Figure 7 The results also show that the target products prepared in Example 2 and Example 4 have Figure 1 Similar results.

[0047] Figure 2The transmission electron microscope (TEM) photo of the target product obtained in Example 1 shows that the prepared Cr2Se3 is a nanomaterial with a flaky structure, with a thickness of about 2-5 nm and a length of about 20-100 nm. Figure 6 The results also show that the target product prepared in Example 3 has Figure 2 Similar results.

[0048] In addition, the Figure 2 and Figure 6 The results also show that the target product exhibits a multi-level structure formed by the self-assembly of several two-dimensional Cr2Se3 porous nanomaterials. As shown in the figure, the multi-level structure refers to a structure similar to a "nanoflower" formed by the cross-self-assembly of multiple nanosheets. Compared with a single nanosheet, the multi-level nanostructure has the following advantages: (1) It can reflect or scatter the incident light multiple times, thereby improving the light absorption efficiency. (2) It can solve the problem of easy stacking and agglomeration between nanosheets.

[0049] Figure 3 This is the ultraviolet-visible-near-infrared (UV-vis-NIR) absorption spectrum of the product obtained in Example 1, which proves that the two-dimensional Cr2Se3 nanosheet material has a strong absorption capacity in the visible-near-infrared light range, indicating that the two-dimensional Cr2Se3 nanosheet material can be used as a light-absorbing material in research fields such as photocatalysis and photoelectric conversion.

[0050] Figure 4 The photocatalytic degradation result of methylene blue by the product obtained in Example 1. First, the surface of the two-dimensional Cr2Se3 nanosheet material was modified by mercaptopropionic acid to enhance its water solubility, that is, the two-dimensional Cr2Se3 nanosheet material was dispersed in a mixed solution of cyclohexane and mercaptopropionic acid with a volume ratio of 3:1 under ultrasound, left to stand for 24 hours, and then washed by centrifugation with anhydrous ethanol three times. Secondly, 50 mg of the target product was weighed and dispersed into 50 mL of a 10 mg / L methylene blue aqueous solution, and stirred for 30 minutes in a dark place to reach adsorption / desorption equilibrium. Then, a 300W xenon lamp was used for irradiation, and 1.0 mL of the mixed solution was centrifuged every 10 minutes. The supernatant was taken, and the absorbance at a wavelength of 664 nm was measured by a UV-visible spectrophotometer to calculate the degradation rate. Figure 4 As shown, the two-dimensional Cr2Se3 nanosheets have good degradation ability for methylene blue dye.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A two-dimensional Cr2Se3 nanomaterial, characterized in that: The material is a hexagonal crystal, and the main diffraction peaks in its XRD diffraction pattern are located at 30.8±0.1°, 32.6±0.1°, 42.6±0.1°, 50.7±0.1°, 56.1±0.1°, 61.7±0.1°, and 64.3±0.1°, respectively; the microscopic morphology is nano-scale flakes with a thickness of 2~5nm and a side length of 20~100nm.

2. The method for preparing the two-dimensional Cr2Se3 nanomaterial according to claim 1, characterized in that: The method comprises the following steps: adding a soluble chromium source and a selenium source into a high-boiling-point reaction medium to carry out a solvent thermal reaction, and separating a solid reaction product to obtain the product.

3. The preparation method according to claim 2, characterized in that: In the solvent thermal reaction system, the molar ratio of Cr:Se elements is 1:1.5-3.

4. The preparation method according to claim 2, characterized in that: The chromium source includes but is not limited to one or a combination of chromium acetylacetonate, chromium trichloride, chromium nitrate or chromium acetate; the selenium source includes one or a combination of diphenyl diselenide, dibenzyl diselenide, selenium dioxide or selenium powder.

5. The preparation method according to claim 2, characterized in that: The high boiling point reaction medium is selected from one or a combination of organic amines, oleic acid, and octadecene, wherein the organic amine is selected from one or a combination of oleylamine, octadecylamine, or hexadecylamine.

6. The preparation method according to claim 5, characterized in that: The high boiling point reaction medium is a mixture of organic amine and oleic acid in a volume ratio of 1 to 7:

1.

7. The preparation method according to claim 2, characterized in that: The solvent thermal reaction includes a first stage and a second stage: in the first stage, the chromium source and the selenium source are added to the reaction medium under an inert gas atmosphere, and the reaction is heated to 130-180° C. for 30-90 minutes; in the second stage, the reaction system is continuously heated to keep the temperature between 260-350° C., and the reaction time is controlled between 5-180 minutes.

8. The use of the two-dimensional Cr2Se3 nanomaterial as claimed in claim 1 as a photocatalytic degradation material, characterized in that: The application is to degrade dye pollutants in water environments; the dyes include but are not limited to methyl blue, methylene blue or Sudan red.

9. A method for degrading methylene blue in an aquatic environment, characterized in that: The method comprises dispersing the two-dimensional Cr2Se3 nanomaterial described in claim 1 into a water environment that needs to be treated.

10. The method for degrading methylene blue in an aquatic environment as claimed in claim 9, characterized in that: The steps of the degradation method are as follows: using mercaptopropionic acid to modify the surface of the two-dimensional Cr2Se3 nanomaterial described in claim 1; dispersing the modified nanomaterial into the water environment to be treated to dissolve it, and then irradiating it with light.

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