A sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction, its preparation method and application

Abstract

This invention discloses a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction. The tungsten oxide / indium zinc sulfide heterojunction consists of tungsten trioxide located within a central sphere and indium zinc sulfide distributed as nanosheets on the sphere's surface, forming a three-dimensional sunflower shape. Using glucose as a raw material, this invention first prepares uniformly sized carbon spheres via a hydrothermal method. Then, using the synthesized carbon spheres as a template and WCl6 as a precursor, hollow WO3 spheres are obtained through in-situ hydrolysis combined with high-temperature calcination. Finally, using the synthesized hollow WO3 spheres, indium chloride, indium chloride, and thioacetamide as starting materials, the three-dimensional sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction is prepared using a water bath method. The WO3 / ZnIn2S4 heterojunction material of this invention has a larger specific surface area than pure WO3, which is beneficial for exposing more active sites. The three-dimensional heterojunction constructed in this invention can effectively inhibit the free diffusion of CO2 molecules, increase the local CO2 concentration on the catalyst surface, and is more conducive to the adsorption and activation of CO2 molecules.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation technology, and specifically relates to a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction, its preparation method and application. Background Technology

[0002] To address the global challenges posed by climate change, the resource-based conversion of CO2 has become a crucial research topic. Photocatalytic CO2 reduction technology, driven directly by clean sunlight and operating under mild reaction conditions, is considered an ideal approach. Although abundant materials have demonstrated the catalytic ability of sunlight to reduce CO2, the high C=O bond dissociation energy (750 kJ / mol), the complex multi-proton coupled electron transfer process involved in the photocatalytic CO2 reduction reaction, and the tendency for photogenerated carriers to recombine lead to low efficiency. Therefore, designing a composite material to promote the separation of photogenerated carriers and provide more reactive sites is currently key to improving the efficiency of photocatalytic CO2 reduction.

[0003] The design of hollow spherical structures is of great significance for promoting the chemisorption and activation of CO2 molecules on the catalyst surface. Chinese Patent Application No. CN201911347513.9 discloses a hollow mesoporous defect-type tungsten trioxide nanosphere, its preparation method, and its application in photothermal catalytic reduction of CO2 to methane. The preparation method includes the following steps: dissolving a tungsten precursor in glacial acetic acid to obtain a precursor solution; subjecting the precursor solution to a hydrothermal reaction at 160-180℃ for 16-18 hours; allowing the reaction to proceed naturally after cooling; ultrasonicating the resulting reaction solution for 12-16 hours; centrifuging, washing, drying, calcining at 500-550℃, and allowing natural cooling to obtain tungsten trioxide powder; and reducing the tungsten trioxide powder with H2 / Ar at 400-450℃ to obtain the hollow mesoporous defect-type tungsten trioxide nanospheres. These hollow mesoporous defect-type tungsten trioxide nanospheres are formed by the self-assembly and stacking of WO3 nanorods, with the molecular formula WO3. 3x Where 2.5 < x < 3, and the particle size is 200-500 nm. Irradiated with a full-spectrum light source, the hollow mesoporous defect-type tungsten trioxide nanospheres exhibit excellent photocatalytic reduction performance of CO2. However, the photocatalytic CO2 reduction product is mainly CO, with poor selectivity for the multi-electron reduction product CH4. Therefore, to improve the selectivity of WO3 photocatalytic CO2 reduction to CH4, designing a composite heterojunction based on WO3 hollow spheres is crucial.

[0004] ZnIn2S4, a typical layered ternary chalcogenide compound, has attracted widespread attention due to its excellent visible light absorption and tunable morphology. More importantly, the matched band structure of ZnIn2S4 and WO3 provides the driving force for charge migration and separation at the interface, which can effectively promote the separation efficiency of photogenerated carriers and thus improve the selectivity for the multi-electron reduction product CH4.

[0005] While heterojunctions constructed from ZnIn2S4 and WO3 have been used for photocatalytic CO2 reduction, sunflower-shaped heterojunctions constructed from three-dimensional hollow WO3 and ultrathin two-dimensional ZnIn2S4 nanosheets have not yet been reported. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction, its preparation method, and its application.

[0007] The technical solution of the present invention is as follows:

[0008] One of the objectives of this invention is to provide a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction, wherein the tungsten oxide / indium zinc sulfide heterojunction is composed of tungsten trioxide located in a central sphere and indium zinc sulfide distributed on the surface of the sphere in the form of nanosheets, and the tungsten oxide / indium zinc sulfide heterojunction is three-dimensional sunflower-shaped.

[0009] The second objective of this invention is to provide a method for preparing a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction. The tungsten oxide / indium zinc sulfide heterojunction uses glucose as a raw material. First, uniformly sized carbon spheres are prepared by hydrothermal method. Then, using the synthesized carbon spheres as templates and WCl6 as a precursor, WO3 hollow spheres are obtained by in-situ hydrolysis combined with high-temperature calcination. Finally, using the synthesized WO3 hollow spheres, indium chloride, indium chloride, and thioacetamide as starting materials, a three-dimensional sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction is prepared by water bath method.

[0010] Furthermore, the preparation method specifically includes the following steps:

[0011] S1: Glucose was dissolved in ultrapure water and then hydrothermally reacted in a high-pressure reactor at 180°C for 12 hours. After washing and drying, carbon spheres were obtained.

[0012] S2: Mix carbon spheres with surfactant and dissolve them in an organic solvent to obtain solution A, which is then set aside.

[0013] S3: Dissolve WCl6 in an organic solvent to obtain solution B, which is then set aside.

[0014] S4: Under the action of ultrasound, solution B is slowly added dropwise to solution A. After the addition is completed, ultrasound treatment is performed again to obtain a mixture of AB.

[0015] S5: Add ultrapure water dropwise to the AB mixture and stir at room temperature for 24 hours. After washing and drying, place it in a muffle furnace and heat it to 450°C at a heating rate of 2°C / min and calcine for 2 hours to obtain WO3 hollow spheres, which are labeled as WO3.

[0016] S6: Adjust the pH of 8 mL of ultrapure water to 2.5 with HCl, add 2 mL of glycerol and stir well, then add zinc chloride, indium chloride and thioacetamide, and sonicate until homogeneous;

[0017] S7: Add the WO3 obtained in step S5 to the solution that has been ultrasonically treated in step S6, stir at room temperature for 30 min, and then continue stirring and reacting in an 80℃ water bath for 2 h. Finally, wash with ultrapure water and anhydrous ethanol by centrifugation and vacuum drying to obtain the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction material.

[0018] Furthermore, in step S2, the surfactant is hexadecyltrimethylammonium bromide.

[0019] Furthermore, in steps S2 and S3, the organic solvent is N,N-dimethylformamide.

[0020] Furthermore, in step S6, the molar ratio of zinc chloride, indium chloride, and thioacetamide is 1:2:8.

[0021] The third objective of this invention is to provide an application of a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction in the photocatalytic selective reduction of CO2 to CH4.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention provides a novel three-dimensional sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material and its preparation method, and for the first time applies this three-dimensional sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material to the photocatalytic selective reduction of CO2 to CH4. In the composite structure synthesized in this invention, WO3 is located inside the central sphere, while ZnIn2S4 is distributed on the surface of the sphere in the form of nanosheets. This WO3 / ZnIn2S4 heterojunction material has a larger specific surface area than pure WO3, which is beneficial for exposing more active sites. The three-dimensional heterojunction constructed in this invention can effectively inhibit the free diffusion of CO2 molecules, increase the local CO2 concentration on the catalyst surface, and is more conducive to the adsorption and activation of CO2 molecules.

[0024] 2. The sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction provided by the present invention is more conducive to carrier migration and separation at the interface.

[0025] 3. The sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction provided by this invention, due to its excellent catalytic performance and selectivity for CH4 products, can be applied to the photocatalytic selective reduction of CO2 to CH4. Attached Figure Description

[0026] Figure 1 This is a transmission electron microscope (TEM) image of the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction prepared in Example 3.

[0027] Figure 2 This is a schematic diagram of the WO3 hollow sphere synthesis process in Example 1;

[0028] Figure 3 This is a schematic diagram of the synthesis process of the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction in Examples 1-5;

[0029] Figure 4 Scanning electron microscope (SEM) images of the WO3 hollow spheres prepared in Example 1 and W / ZIS-1, W / ZIS-2, W / ZIS-3, W / ZIS-4, and W / ZIS-5 prepared in Examples 1-5;

[0030] Figure 5 Transmission electron microscope image and corresponding elemental distribution diagram of the sunflower-shaped WO3 / ZnIn2S4 heterojunction material prepared in Example 3;

[0031] Figure 6 The image shows the photocatalytic CO2 reduction activity of the WO3 hollow spheres prepared in Example 1 and the W / ZIS-1, W / ZIS-2, W / ZIS-3, W / ZIS-4, and W / ZIS-5 prepared in Examples 1-5. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, specific embodiments of this application will be described below, with reference to the accompanying drawings. Figure 1-6 The technical solution of the present invention will be clearly and completely described.

[0033] Example 1

[0034] This embodiment provides a method for preparing a sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction. The tungsten oxide / indium zinc sulfide heterojunction uses glucose as a raw material. First, uniformly sized carbon spheres are prepared by hydrothermal method. Then, using the synthesized carbon spheres as templates and WCl6 as a precursor, WO3 hollow spheres are obtained by in-situ hydrolysis combined with high-temperature calcination. Finally, using the synthesized WO3 hollow spheres, indium chloride, indium chloride, and thioacetamide as starting materials, a three-dimensional sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction is prepared by water bath method.

[0035] Specifically, such as Figure 3 As shown, the preparation method of this embodiment includes the following steps:

[0036] S1: Dissolve 6g of glucose in 60ml of ultrapure water and then hydrothermally react it in a high-pressure reactor at 180℃ for 12h. After washing and drying, carbon balls are obtained.

[0037] S2: Mix 0.25g of carbon spheres with 0.1g of hexadecyltrimethylammonium bromide and dissolve in 50ml of N,N-dimethylformamide. After sonication for 30min, obtain solution A for later use.

[0038] S3: Dissolve 0.1g of WCl6 in 10ml of N,N-dimethylformamide to obtain solution B, which is ready for use.

[0039] S4: Under the action of ultrasound, solution B is slowly added dropwise to solution A. After the addition is complete, the solution is ultrasonically treated again for 30 minutes to obtain a mixture of A and B.

[0040] S5: Add 1 ml of ultrapure water dropwise to the AB mixture to hydrolyze WCl6, then sonicate for 1 h, stir the resulting mixture at room temperature for 24 h, centrifuge and wash with anhydrous ethanol and ultrapure water until the ion concentration is below 10 ppm, then freeze dry in a freeze dryer, finally grind and disperse the dried solid, place it in a muffle furnace and heat it to 450℃ at a heating rate of 2℃ / min and calcine for 2 h to obtain the product WO3 hollow spheres, labeled as WO3;

[0041] In this embodiment, the synthesis process of WO3 hollow spheres is as follows: Figure 2 As shown;

[0042] S6: Adjust the pH of 8 mL of ultrapure water to 2.5 with HCl, add 2 mL of glycerol and stir well, then add 0.04 mmol zinc chloride, 0.08 mmol indium chloride and 0.32 mmol thioacetamide, and sonicate until homogeneous;

[0043] S7: Add 30 mg of the WO3 hollow spheres obtained in step S5 to the solution that has been ultrasonically treated in step S6. After stirring at room temperature for 30 min, continue stirring and reacting in an 80℃ water bath for 2 h. After the reaction is completed, wash with ultrapure water and anhydrous ethanol by centrifugation until the ion concentration is below 10 ppm, and dry in a 60℃ vacuum oven to obtain the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction material, which is labeled as W / ZIS-1.

[0044] In the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction material prepared in this embodiment, the tungsten oxide / indium zinc sulfide heterojunction is composed of tungsten trioxide located in the central sphere and indium zinc sulfide distributed on the surface of the sphere in the form of nanosheets, and the tungsten oxide / indium zinc sulfide heterojunction is three-dimensional sunflower-shaped.

[0045] Example 2

[0046] The process is basically the same as in Example 1, except that in step S6 of this example, the zinc chloride is 0.08 mmol, the indium chloride is 0.16 mmol, and the thioacetamide is 0.64 mmol. The resulting sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material is labeled as W / ZIS-2.

[0047] Example 3

[0048] The process is basically the same as in Example 1, except that in step S6 of this example, the amount of zinc chloride is 0.12 mmol, the amount of indium chloride is 0.24 mmol, and the amount of thioacetamide is 0.96 mmol. The resulting sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material is labeled as W / ZIS-3.

[0049] Example 4

[0050] The process is basically the same as in Example 1, except that in step S6 of this example, zinc chloride is 0.15 mmol, indium chloride is 0.3 mmol, and thioacetamide is 1.2 mmol. The resulting sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material is labeled as W / ZIS-4.

[0051] Example 5

[0052] The process is basically the same as in Example 1, except that in step S6 of this example, the zinc chloride is 0.2 mmol, the indium chloride is 0.4 mmol, and the thioacetamide is 1.6 mmol. The resulting sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction material is labeled as W / ZIS-5.

[0053] Figure 1 The image shows a transmission electron microscope (TEM) image of the sunflower-shaped tungsten oxide / zinc indium sulfide heterojunction prepared in Example 3. As can be seen from the image, Example 3 successfully prepared a sunflower-shaped WO3 / ZnIn2S4 heterojunction material. The ZnIn2S4 nanosheets exhibit an ultrathin morphology and are uniformly grown on the hollow spherical WO3 surface. In the high-resolution TEM image, two sets of lattice fringes with spacings of 0.369 nm and 0.294 nm are attributed to the (200) crystal plane of monoclinic WO3 and the (104) crystal plane of hexagonal ZnIn2S4, respectively.

[0054] Figure 2 This is a schematic diagram of the synthesis process of the WO3 hollow spheres in Example 1.

[0055] Figure 3 This is a schematic diagram of the synthesis process of the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction in Examples 1-5.

[0056] Figure 4Scanning electron microscope (SEM) images of the WO3 hollow spheres prepared in Example 1 and W / ZIS-1, W / ZIS-2, W / ZIS-3, W / ZIS-4, and W / ZIS-5 prepared in Examples 1-5 show that the number of ZnIn2S4 nanosheets grown in situ on the WO3 hollow spheres varies depending on the amount of ZnIn2S4 precursor (ZnCl2, InCl3·4H2O, CH3CSNH2). When the amount of precursor added is small, only a small number of ZnIn2S4 nanosheets can be observed on the WO3 surface. As the amount of precursor added increases, the coverage of ZnIn2S4 on the surface of the WO3 hollow spheres increases. When an appropriate amount of precursor is added, the WO3 is completely encapsulated by ZnIn2S4 nanosheets, exhibiting a three-dimensional sunflower-like morphology.

[0057] Figure 5 The images show the transmission electron microscope (TEM) image and elemental distribution diagram of the sunflower-shaped WO3 / ZnIn2S4 heterojunction material prepared in Example 3. The images demonstrate the successful preparation of the sunflower-shaped WO3 / ZnIn2S4 heterojunction material. The ZnIn2S4 nanosheets exhibit an ultrathin morphology and are uniformly grown on the surface of the hollow WO3 sphere structure. In the high-resolution TEM image, two sets of lattice fringes with spacings of 0.369 nm and 0.294 nm are attributed to the (200) crystal plane of monoclinic WO3 and the (104) crystal plane of hexagonal ZnIn2S4, respectively. Furthermore, the elemental distribution diagram shows that the composite heterojunction material comprises W, O, S, In, and Zn, with W and O distributed within the central sphere, and S, In, and Zn distributed on the nanosheets surrounding the sphere. This further confirms the successful synthesis of the sunflower-shaped structure consisting of ZnIn2S4 nanosheets encapsulating a hollow WO3 sphere.

[0058] Figure 6 The figures show the photocatalytic CO2 reduction activity of the WO3 hollow spheres prepared in Example 1 and the W / ZIS-1, W / ZIS-2, W / ZIS-3, W / ZIS-4, and W / ZIS-5 prepared in Examples 1-5. The photocatalytic CO2 reduction product of the pure WO3 hollow spheres is mainly CO, with only a small amount of CH4 produced. The WO3 / ZnIn2S4 heterojunction material, however, exhibits significantly improved CO2 reduction performance, with both CH4 and CO generation rates markedly increased. Furthermore, the CH4 selectivity curves also show that the composite WO3 / ZnIn2S4 heterojunction exhibits significantly improved selectivity for CH4, reaching a maximum of 82.1%, which is 13 times that of WO3.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. Application of a solar sunflower-like tungsten oxide / indium zinc sulfide heterojunction in the photocatalytic selective reduction of CO2 to CH4, characterized in that, The tungsten oxide / indium zinc sulfide heterojunction is composed of tungsten trioxide located in the center of the sphere and indium zinc sulfide distributed in the form of nanosheets on the surface of the sphere, and the tungsten oxide / indium zinc sulfide heterojunction is a three-dimensional sunflower-shaped structure. The tungsten oxide / indium zinc sulfide heterojunction is prepared by using glucose as a raw material, preparing uniform carbon spheres by a hydrothermal method, using the synthesized carbon spheres as a template, using WCl6 as a precursor, and obtaining WO3 hollow spheres by in-situ hydrolysis combined with high-temperature calcination, and finally using the synthesized WO3 hollow spheres, indium chloride, zinc chloride and thioacetamide as starting materials to prepare the three-dimensional sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction by a water bath method. The preparation method of the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction specifically comprises the following steps: S1: Dissolve glucose in ultrapure water, and then perform hydrothermal reaction at 180℃ in a high-pressure reaction kettle for 12h, and then wash and dry to obtain carbon spheres; S2: Mix the carbon spheres with a surfactant and dissolve them in an organic solvent to obtain solution A for standby; S3: Dissolve WCl6 in an organic solvent to obtain solution B for standby; S4: Under the action of ultrasonic, slowly add solution B to solution A, and then perform ultrasonic treatment again after the addition is completed to obtain AB mixed solution; S5: Add ultrapure water to the AB mixed solution, and stir at room temperature for 24h, and then wash and dry, and then place in a muffle furnace and heat to 450℃ at a heating rate of 2℃ / min and calcine for 2h to obtain WO3 hollow spheres, marked as WO3; S6: Adjust the pH of 8mL of ultrapure water to 2.5 with HCl, add 2mL of glycerol and stir uniformly, and then add zinc chloride, indium chloride and thioacetamide and perform ultrasonic treatment until uniform; S7: Add WO3 obtained in step S5 to the solution treated by ultrasonic in step S6, stir for 30min at room temperature, and then continuously stir in a water bath at 80℃ for 2h, and finally wash and centrifuge with ultrapure water and anhydrous ethanol and vacuum dry to obtain the sunflower-shaped tungsten oxide / indium zinc sulfide heterojunction material.

2. The use of a solar flower-like tungsten oxide / indium zinc sulfide heterojunction according to claim 1 in the photocatalytic selective reduction of CO2 to CH4, characterized in that, In step S2, the surfactant is cetyltrimethylammonium bromide.

3. The use of a solar flower-like tungsten oxide / indium zinc sulfide heterojunction according to claim 1 in the photocatalytic selective reduction of CO2 to CH4, characterized in that, In steps S2 and S3, the organic solvent is N,N-dimethylformamide.

4. The use of a solar flower-like tungsten oxide / indium zinc sulfide heterojunction according to claim 1 in the photocatalytic selective reduction of CO2 to CH4, characterized in that, In step S6, the molar ratio of zinc chloride, indium chloride and thioacetamide is 1:2:8.

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