A SnS 2 / KNbO 3 Composite photocatalyst, preparation method and application thereof

Abstract

The present invention belongs to the technical field of photocatalytic materials, specifically a SnS2 / KNbO3 composite photocatalyst and its preparation method and application. The preparation method of the SnS2 / KNbO3 composite photocatalyst is as follows: Potassium niobate microblocks are prepared by a hydrothermal method, and then tin disulfide nanosheets are tightly coated on the outer surface of KNbO3 through a simple low-temperature water bath method to obtain a SnS2 / KNbO3 heterojunction with a three-dimensional hierarchical structure. The SnS2 / KNbO3 composite photocatalytic material prepared by the present invention greatly improves the photocatalytic activity for decomposing methylene blue, solves the problem of poor photocatalytic activity of KNbO3 in the prior art, and moreover, the preparation process provided by the present invention is simple, the experimental conditions are easy to control, the cost is low, and it is safe and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a SnS 2 / KNbO 3 composite photocatalyst and its preparation method and application. Background Art

[0002] Wastewater generated in industrial production processes has become the main source of water pollution; among them, printing and dyeing wastewater is one of the recognized major industrial pollution sources. Due to its high toxicity, complex composition, and difficult degradation characteristics, printing and dyeing wastewater has become the focus of attention.

[0003] Methylene blue (MB) is the most common component in printing and dyeing wastewater. It is worth noting that as a typical azo dye, MB is toxic and can cause cancer and gene mutations; in addition, even at very low dye concentrations, water will be colored, thus affecting the living environment of aquatic organisms; once these untreated wastewater are discharged into the water environment, it will pose a serious threat to the ecosystem and human health. Therefore, removing dyes from water is crucial for restoring the ecological environment and human health. To eliminate these pollutants in the aquatic environment, scholars have proposed many methods, such as physical adsorption, biological treatment, photocatalytic oxidation, and electrochemical oxidation. Among them, photocatalytic technology has been widely applied to the purification of wastewater and air due to its advantages of good economy, environmental friendliness, and high efficiency.

[0004] Potassium niobate (KNbO 3 ) has potential application value in the fields of photocatalytic degradation of printing and dyeing wastewater, photocatalytic water splitting for hydrogen production, etc. due to its non-toxicity, good chemical stability, low cost, etc.; moreover, KNbO 3 has a perovskite structure, which helps the migration and separation of photo-generated carriers. However, due to its relatively large band gap (~3.2 eV), it can only respond to ultraviolet light, and the single KNbO 3 photo-generated electron-hole pairs (e - -h + ) are prone to recombination. These factors greatly limit its photocatalytic activity; therefore, a material that can expand the spectral response range of KNbO 3 and reduce the recombination rate of its photo-generated carriers is needed to solve the technical defects existing in KNbO 3 itself. Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a SnS 2 / KNbO 3 composite photocatalyst and its preparation method and application. In the present invention, in order to expand KNbO 3Spectral response range and reduce its photogenerated carrier recombination rate, on KNbO 3 Load a narrow-bandgap semiconductor SnS with a band alignment on the surface 2 material to obtain SnS 2 / KNbO 3 composite photocatalyst, and use SnS 2 / KNbO 3 composite photocatalyst in the photocatalytic degradation of methylene blue.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A preparation method of SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0008] Prepare KNbO 3 microblocks;

[0009] Prepare a SnCl 4 solution and prepare a thioacetamide solution, using SnCl 4 as the Sn source and thioacetamide as the S source;

[0010] Mix the KNbO 3 microblocks with the SnCl 4 solution to obtain a mixed solution, drop the thioacetamide solution into the mixed solution, and then carry out a reaction using a low-temperature water bath method. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain SnS 2 / KNbO 3 composite photocatalyst;

[0011] Preferably, the KNbO 3 microblocks are prepared by a hydrothermal method, and the specific steps are:

[0012] Disperse Nb 2 O 5 in a KOH solution, stir and mix for 1 h to obtain a suspension, carry out a hydrothermal reaction on the suspension, and after the reaction is completed, centrifuge, wash, and dry to obtain KNbO 3 microblocks.

[0013] Preferably, the mass ratio of KOH to Nb 2 O 5 is 55:2 - 7, and the conditions for the hydrothermal reaction are: carry out the hydrothermal reaction at 140 - 180 °C for 10 - 16 h.

[0014] Preferably, the preparation method of the SnCl 4 solution is: dissolve SnCl 4 ·5H 2O is mixed with absolute ethanol to obtain SnCl 4 solution;

[0015] The preparation method of thioacetamide solution is: mixing thioacetamide powder with absolute ethanol to obtain thioacetamide solution.

[0016] Preferably, the molar ratio of thioacetamide to SnCl 4 ·5H 2 O is 2-6:1.

[0017] Preferably, the conditions of the low-temperature water bath method are: reacting at a water bath temperature of 60-90 °C for 2-5 h.

[0018] Preferably, in the SnS 2 / KNbO 3 composite photocatalyst, the mass ratio of SnS 2 to KNbO 3 is 400:10-30.

[0019] Preferably, in the SnS 2 / KNbO 3 composite photocatalyst, the mass ratio of SnS 2 to KNbO 3 is 400:20, and the best photocatalytic degradation performance is obtained at the ratio of 400:20.

[0020] The present invention also protects the SnS 2 / KNbO 3 composite photocatalyst prepared by the above preparation method.

[0021] The present invention also protects the application of the SnS 2 / KNbO 3 composite photocatalyst in the preparation of a photocatalyst for degrading methylene blue.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. Tin disulfide (SnS 2 ) is a typical two-dimensional material with a relatively narrow bandgap (~2.1 eV), strong visible light absorption ability and good chemical stability, and has good visible light activity in aspects such as pollutant degradation, Cr(VI) reduction and water splitting; in addition, the conduction band potential and valence band potential of SnS 2 are more negative than the energy levels of KNbO 3 , and the energy band structure shows an interleaved type. When SnS 2 is combined with KNbO 3 , SnS is formed at the interface of SnS 2 and KNbO 3 materials interface to form SnS2 / KNbO 3 heterojunction, in which band bending occurs, helping to promote the separation and migration of photo-generated electron-hole pairs; and SnS 2 loaded on the surface of KNbO 3 will also broaden the light absorption range of KNbO 3 . As far as we know, so far, there are almost no reports on coupling SnS 2 with KNbO 3 . We prepared a SnS 2 / KNbO 3 composite photocatalyst by a simple method and applied it to the photocatalytic degradation of methylene blue.

[0024] 2. In the present invention, SnS 2 nanosheets are wrapped on the surface of KNbO 3 microblocks to obtain a SnS 2 / KNbO 3 heterojunction with a three-dimensional hierarchical structure, increasing the specific surface area of the catalyst, broadening the light absorption range of KNbO 3 , and promoting the separation and migration of photo-generated electron-hole pairs. Compared with the SnS 2 catalyst and the KNbO 3 catalyst, the SnS 2 / KNbO 3 composite photocatalyst obtained in the present invention has significantly enhanced photocatalytic activity.

[0025] 3. The preparation method of the SnS 2 / KNbO 3 composite photocatalyst in the present invention is as follows: Potassium niobate microblocks are prepared by a hydrothermal method, and then tin disulfide nanosheets are tightly coated on the outer surface of KNbO 3 by a simple low-temperature water bath method to obtain a SnS 2 / KNbO 3 heterojunction with a three-dimensional hierarchical structure. The SnS 2 / KNbO 3 composite photocatalytic material prepared in the present invention greatly improves the activity of photocatalytic decomposition of methylene blue, solves the problem of poor photocatalytic activity of KNbO 3 in the prior art, and moreover, the synthesis method of this application is simple, the experimental conditions are easy to control, the cost is low, safe and reliable; the prepared SnS 2 / KNbO 3 composite photocatalyst has good application prospects and industrialization prospects in the fields of environmental remediation and energy. Brief Description of the Drawings

[0026] Figure 1 For KNbO of Comparative Example 13 Photocatalyst, SnS of Comparative Example 2 2 Photocatalyst, SnS of Example 1 2 / KNbO 3 Composite photocatalyst, and SnS of Examples 4 - 5 2 / KNbO 3 X-ray diffraction pattern spectrum of the composite photocatalyst;

[0027] Figure 2 is KNbO 3 Photocatalyst, SnS 2 Photocatalyst and SnS 2 / KNbO 3 Scanning electron microscope morphology map of the composite photocatalyst; among them, (a) is SnS of Comparative Example 2 2 Morphology map of the photocatalyst sample, (b) is KNbO of Comparative Example 1 3 Morphology map of the photocatalyst sample, (c) is SnS of Example 1 2 / KNbO 3 Morphology map of the composite photocatalyst sample; (d) is SnS of Comparative Example 4 2 / KNbO 3 Morphology map of the composite photocatalyst sample;

[0028] Figure 3 among them, (a) is SnS of Example 1 2 / KNbO 3 Transmission electron microscope (TEM) image of the composite photocatalyst; (b) is SnS of Example 1 2 / KNbO 3 High-resolution transmission electron microscope (HRTEM) image of the composite photocatalyst;

[0029] Figure 4 is SnS of Example 1 2 / KNbO 3 Energy dispersive (EDS) spectrum of the composite photocatalyst;

[0030] Figure 5 is SnS of Example 1 2 / KNbO 3 XPS spectrum of the composite photocatalyst; among them, (a) is the full spectrum; (b) is the Sn3d spectrum; (c) is the O1s spectrum; (d) is the Nb 3d spectrum; (e) is the K 2p spectrum; (f) is the S2p spectrum;

[0031] Figure 6 is KNbO of Comparative Example 1 3 Photocatalyst, SnS of Comparative Example 2 2 Photocatalyst, SnS of Example 12 / KNbO 3 Composite photocatalyst and SnS of Comparative Examples 4-5 2 / KNbO 3 UV-visible absorption diagram of the composite photocatalyst;

[0032] Figure 7 For KNbO of Comparative Example 1 3 Photocatalyst, SnS of Comparative Example 2 2 Photocatalyst, KNbO of Comparative Example 3 3 Microblocks and SnS 2 Mixture, SnS of Example 1 2 / KNbO 3 Composite photocatalyst and SnS of Comparative Examples 4-5 2 / KNbO 3 Photodegradation activity comparison diagram of methylene blue by the composite photocatalyst; among them, (a) is the photocatalytic efficiency comparison diagram; (b) is the photocatalytic kinetics comparison diagram. Detailed Description of the Invention

[0033] The following is a detailed description of the specific embodiments of the present invention, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. The experimental methods described in each embodiment of the present invention are conventional methods unless otherwise specified.

[0034] The present invention provides a preparation method of a SnS 2 / KNbO 3 composite photocatalyst, in which SnS 2 nanosheets are wrapped on the surface of KNbO 3 microblocks, including the following steps: preparing KNbO 3 microblocks by hydrothermal method; preparing SnCl 4 solution and thioacetamide solution; adding KNbO 3 microblocks into the SnCl 4 solution for ultrasonic treatment, then slowly dropping the thioacetamide ethanol solution into the above mixed solution, then performing stirring treatment at low temperature, and finally obtaining the SnS 2 / KNbO 3 composite photocatalyst after centrifugation, washing, and vacuum drying.

[0035] Aiming at the technical defects of narrow spectral response range and high recombination rate of photo-generated carriers existing in the single KNbO 3 in the prior art, the present application adopts SnS 2 and KNbO 3Compound SnS 2 with KNbO 3 After the compounding, the energy levels of SnS 2 and KNbO 3 match well, and a heterojunction is formed at the contact interface between the two. The heterojunction helps to promote the separation and migration of photo-generated electron-hole pairs, and solves the problem of high recombination rate of photo-generated carriers;

[0036] SnS 2 is a two-dimensional sheet structure. After compounding with KNbO 3 microblocks, a three-dimensional hierarchical structure is obtained, increasing the specific surface area of the catalyst and broadening the light absorption range of KNbO 3 ; The three-dimensional structure and the heterojunction improve the catalytic activity at the same time, and the SnS 2 / KNbO 3 composite photocatalyst with a three-dimensional hierarchical structure and containing a heterojunction solves the technical defects existing in single KNbO 3 .

[0037] In order to verify the influence of the amount of KNbO 2 in the SnS 3 / KNbO 3 composite photocatalyst on the catalytic performance, a comparative study of different amounts of KNbO 3 microblocks was also carried out. The results show that the amount of KNbO 3 microblocks in the SnS 2 / KNbO 3 composite photocatalyst is not the more the better. An excessive amount of KNbO 3 microblocks will instead lead to a decrease in the photocatalytic performance. The comparison results show that in the SnS 2 / KNbO 3 composite photocatalyst, the best photocatalytic degradation performance of methylene blue is obtained at a mass ratio of SnS 2 to KNbO 3 of 400:20.

[0038] The following is an in-depth study using examples and comparative examples, as shown below:

[0039] Example 1

[0040] A preparation method of a SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0041] S1. Prepare KNbO 3 microblocks by hydrothermal method;

[0042] Add 55 g of KOH to 50 mL of deionized water, stir to dissolve, and then disperse 5.32 g of Nb 2 O 5 in the KOH solution, and stir magnetically for 1 h to obtain a suspension;

[0043] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature is 160 °C and the reaction time is 12 h. After the reaction, centrifuge, wash and collect it in a blast drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks;

[0044] S2. Prepare the SnCl 4 solution: Add 0.766 g of SnCl 4 ·5H 2 O to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain the SnCl 4 solution;

[0045] Prepare the thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain the thioacetamide solution;

[0046] S3. Add 20 mg of the KNbO 3 microblocks from step S1 to the SnCl 4 solution in step S2, stir and mix for 20 min to obtain a mixed solution. Subsequently, drop the thioacetamide solution from step S2 into the mixed solution, then stir and mix at 75 °C for 3 h, wash and collect the product with deionized water and ethanol. Finally, dry the product in vacuo at 60 °C for 12 h and then grind it to obtain the SnS 2 / KNbO 3 composite photocatalyst. Since the mass of the added KNbO 3 microblocks is 20 mg, the SnS 2 / KNbO 3 obtained under this condition is labeled as SK-20.

[0047] Example 2

[0048] A preparation method of an SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0049] S1. Prepare KNbO 3 microblocks by the hydrothermal method;

[0050] Add 55 g of KOH to 50 mL of deionized water, stir to dissolve, and then add 2 g of Nb 2 O 5Disperse it in KOH solution and stir magnetically for 1 h to obtain a suspension;

[0051] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature is 180 °C and the reaction time is 10 h. After the reaction, centrifuge, wash and collect it in a forced-air drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks;

[0052] S2. Prepare SnCl 4 solution: Add 0.766 g of SnCl 4 ·5H 2 O to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain SnCl 4 solution;

[0053] Prepare thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain thioacetamide solution;

[0054] S3. Add 10 mg of the KNbO 3 microblocks in step S1 to the SnCl 4 solution in step S2, stir and mix for 20 min to obtain a mixed solution. Then, drop the thioacetamide solution in step S2 into the mixed solution, and then stir and mix at 75 °C for 3 h. Wash and collect the product with deionized water and ethanol. Finally, dry the product in vacuum at 60 °C for 12 h and then grind it to obtain SnS 2 / KNbO 3 composite photocatalyst.

[0055] Example 3

[0056] A preparation method of SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0057] S1. Prepare KNbO 3 microblocks by hydrothermal method;

[0058] Add 55 g of KOH to 50 mL of deionized water, stir and dissolve it, and then add 7 g of Nb 2 O 5 Disperse it in KOH solution and stir magnetically for 1 h to obtain a suspension;

[0059] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature is 140 °C and the reaction time is 16 h. After the reaction, centrifuge, wash and collect it in a forced-air drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks;

[0060] S2. Prepare SnCl 4 solution: Add 0.766 g of SnCl 4 ·5H 2 O to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain SnCl 4 solution;

[0061] Prepare thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain thioacetamide solution;

[0062] S3. Add 30 mg of the KNbO 3 microblocks in step S1 to the SnCl 4 solution in step S2, stir and mix for 20 min to obtain a mixed solution. Then, drop the thioacetamide solution in step S2 into the mixed solution, and then stir and mix at 75 °C for 3 h. Wash and collect the product with deionized water and ethanol. Finally, dry the product in vacuum at 60 °C for 12 h and then grind it to obtain SnS 2 / KNbO 3 composite photocatalyst.

[0063] Comparative Example 1

[0064] Preparation method of KNbO 3 microblocks, including the following steps:

[0065] Add 55 g of KOH to 50 mL of deionized water, stir to dissolve it, and then disperse 5.32 g of Nb 2 O 5 in the KOH solution, and stir magnetically for 1 h to obtain a suspension;

[0066] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature is 160 °C, and the reaction time is 12 h. After the reaction, centrifuge, wash, and collect it in a blast drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks.

[0067] Comparative Example 2

[0068] Preparation method of SnS 2 , including the following steps:

[0069] S1. Prepare SnCl 4 solution: Add 0.766 g of SnCl 4 ·5H 2 O to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain SnCl 4 solution;

[0070] Prepare thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain thioacetamide solution;

[0071] S2. Drop the thioacetamide solution into the SnCl 4 solution, then stir at 75 °C for 3 h, wash and collect the reaction product with deionized water and ethanol, and finally place the product in a vacuum and dry it at 60 °C for 12 h and then grind it to obtain SnS 2 .

[0072] Comparative Example 3

[0073] KNbO 3 microblocks and SnS 2 Preparation method of the mixture, comprising the following steps:

[0074] Mix 400 mg of SnS obtained in Comparative Example 2 2 with 20 mg of KNbO obtained in Comparative Example 1 3 microblocks evenly to obtain a mixture, denoted as mixture.

[0075] Comparative Example 4

[0076] This comparative example has the same preparation steps as Example 1, except that the amount of KNbO 3 microblocks is replaced with 70 mg from 20 mg;

[0077] A preparation method of SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0078] S1. Prepare KNbO 3 microblocks by hydrothermal method;

[0079] Add 55 g of KOH to 50 mL of deionized water, stir to dissolve, and then disperse 5.32 g of Nb 2 O 5 in the KOH solution, and stir magnetically for 1 h to obtain a suspension;

[0080] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction, the reaction temperature is 160 °C, the reaction time is 12 h, after the reaction is completed, centrifuge, wash and collect it in a blast drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks;

[0081] S2. Prepare SnCl 4 solution: Add 0.766 g of SnCl 4·5H 2 O was added to 30 mL of absolute ethanol and stirred for 20 min to completely dissolve it, obtaining a SnCl 4 solution;

[0082] Prepare a thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, obtaining a thioacetamide solution;

[0083] S3. Add 70 mg of the KNbO 3 microblocks from step S1 to the SnCl 4 solution, stir and mix for 20 min to obtain a mixed solution. Subsequently, drop the thioacetamide solution from step S2 into the mixed solution, then stir and mix at 75 °C for 3 h. Wash and collect the reaction product with deionized water and ethanol. Finally, dry the product in vacuo at 60 °C for 12 h and then grind it to obtain the SnS 2 / KNbO 3 composite photocatalyst. Since the mass of the added KNbO 3 microblocks is 70 mg, the SnS 2 / KNbO 3 obtained under this condition is labeled as SK-70.

[0084] Comparative Example 5

[0085] This comparative example has the same preparation steps as Example 1, except that the amount of KNbO 3 microblocks is replaced from 20 mg to 120 mg;

[0086] A preparation method of a SnS 2 / KNbO 3 composite photocatalyst, comprising the following steps:

[0087] S1. Prepare KNbO 3 microblocks by a hydrothermal method;

[0088] Add 55 g of KOH to 50 mL of deionized water, stir and dissolve it, then disperse 5.32 g of Nb 2 O 5 in the KOH solution, and stir magnetically for 1 h to obtain a suspension;

[0089] Transfer the suspension to a reaction kettle lined with polytetrafluoroethylene for reaction. The reaction temperature is 160 °C, the reaction time is 12 h. After the reaction, centrifuge, wash and collect it in a blast drying oven, and dry it at 80 °C for 12 h to obtain KNbO 3 microblocks;

[0090] S2. Prepare SnCl 4Solution: Add 0.766 g of SnCl 4 ·5H 2 O to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain SnCl 4 solution;

[0091] Prepare thioacetamide solution: Add 0.657 g of thioacetamide to 30 mL of absolute ethanol, stir for 20 min to completely dissolve it, and obtain thioacetamide solution;

[0092] S3. Add 120 mg of the KNbO 3 microblocks in step S1 to the SnCl 4 solution in step S2, stir and mix for 20 min to obtain a mixed solution. Then, drop the thioacetamide solution in step S2 into the mixed solution, and then stir at 75 °C for 3 h. Wash and collect the reaction product with deionized water and ethanol. Finally, place the product in a vacuum and dry it at 60 °C for 12 h and then grind it to obtain the SnS 2 / KNbO 3 composite photocatalyst. Since the mass of the added KNbO 3 microblocks is 120 mg, the SnS 2 / KNbO 3 obtained under this condition is labeled as SK-120.

[0093] In Examples 1-3 of the present invention, SnS 2 / KNbO 3 composite photocatalysts with excellent photocatalytic degradation of methylene blue were all prepared. Below, taking the SnS 2 / KNbO 3 composite photocatalyst prepared in Example 1 as an example, it was compared and studied with Comparative Examples 1-5. The specific research methods and results are as follows:

[0094] I. Structure confirmation:

[0095] Figure 1 For KNbO 3 , SnS 2 , the SnS 2 / KNbO 3 composite photocatalyst in Example 1, and the SnS 2 / KNbO 3 composite photocatalysts in Comparative Examples 4-5, the X-ray diffraction patterns (XRD) were obtained. XRD is used to characterize the phase and composition of the materials. As can be seen from Figure 1 , all the diffraction peaks of pure KNbO 3 can be completely attributed to orthorhombic KNbO 3(PDF No. 08 - 0212). The diffraction peaks at 22.18°, 31.70°, 45.21°, 50.88°, 56.12°, 65.78° and 74.64° correspond to the (100), (110), (200), (210), (211), (220) and (310) crystal planes respectively. For pure SnS 2 material, four diffraction peaks located at 15.02°, 28.27°, 32.21° and 50.12° were observed, corresponding to the (001), (100), (101) and (110) crystal planes of hexagonal SnS 2 (JCPDS No. 022 - 0951). In the XRD pattern of the SnS 2 / KNbO 3 composite photocatalyst, the diffraction peaks of both SnS 2 and KNbO 3 exist, and the diffraction peak intensity of potassium niobate gradually becomes stronger with the increase of potassium niobate content.

[0096] Figure 2 For pure SnS 2 material, pure KNbO 3 material, SEM images of the SnS 2 / KNbO 3 composite photocatalyst of Example 1 and Comparative Example 4. Figure 2 a shows the morphology of pure SnS 2 material. SnS 2 is a flower - like structure composed of nanosheets and has a tendency to agglomerate; Figure 2 b shows the morphology of pure KNbO 3 material, which is an irregular cubic block structure. Their size distribution ranges from 2 μm to 6 μm, and the surface is smooth and clean; When SnS 2 is combined with KNbO 3 , the SnS 2 nanosheets tightly wrap around the surface of KNbO 3 micro - blocks (as shown in Figure 2 c and 2d), obtaining a three - dimensional hierarchical structure of SnS 2 / KNbO 3 heterojunction. The results show that the SnS 2 nanosheets and KNbO 3 micro - blocks are well combined, which is beneficial to the separation and migration of photo - generated carriers.

[0097] As Figure 3 a shows, the SnS 2 nanosheets tightly wrap around the surface of KNbO 3 micro - blocks, which is consistent with the results observed by SEM.Figure 3 The HRTEM image of b shows that the lattice fringe spacings are 0.274 nm and 0.283 nm, corresponding to the (101) crystal plane of SnS 2 and the (110) crystal plane of KNbO 3 respectively.

[0098] As Figure 4 shown, EDS elemental mapping clearly shows that the Nb, O, K, S, and Sn elements are uniformly distributed in the SnS 2 / KNbO 3 composite photocatalyst. These results indicate the successful construction of the three-dimensional SnS 2 / KNbO 3 heterojunction.

[0099] XPS was used to study the surface elemental composition of the photocatalyst. Figure 5 The full spectrum in a shows the presence of Nb, O, K, S, and Sn elements, indicating the successful combination of SnS 2 and KNbO 3 . In the high-resolution XPS spectra, the two peaks at 485.93 eV and 494.38 eV ( Figure 5 b) belong to Sn 3d 5 / 2 and Sn 3d 3 / 2 respectively, indicating that Sn exists in the form of Sn 4+ . Figure 5 In c, the peak at 529.19 eV corresponds to O 2- 1s; Figure 5 In d - 5e, the peaks at binding energies of 206.17 eV, 208.89 eV, 290.86 eV, and 293.64 eV correspond to Nb 5+ 3d 5 / 2 , Nb 5+ 3d 3 / 2 , K + 2p 3 / 2 and K + 2p 1 / 2 respectively. Figure 5 In f, the two peaks at 160.94 eV and 162.40 eV belong to S2p 3 / 2 and S2p 1 / 2 respectively, indicating that S exists in the form of S 2- .

[0100] Figure 6 shows that pure KNbO 3 has strong light absorption only in the ultraviolet region, while SnS 2 has strong light absorption in the visible light range. It is worth noting that SnS 2 / KNbO 3The composite photocatalyst also exhibits strong light absorption in the visible light range. Therefore, loading SnS 3 nanosheets on the surface of KNbO 2 helps to enhance the light absorption and photocatalytic activity of KNbO 3 .

[0101] II. Performance Study:

[0102] The SnS 2 / KNbO 3 composite photocatalysts prepared in Example 1 and Comparative Examples 4 - 5 were subjected to a verification experiment on the photocatalytic degradation of methylene blue. Specifically: under the irradiation of a 500W xenon lamp, by using the SnS 2 / KNbO 3 composite photocatalyst to degrade methylene blue, the photocatalytic activities of KNbO 3 , SnS 2 and SnS 2 / KNbO 3 composite photocatalysts with different ratios were studied.

[0103] The specific operating steps of the photocatalytic degradation experiment are as follows: First, 20 mg of the sample was placed into 100 mL of methylene blue (MB) solution (20 mg / L), and stirred for 1 h in the dark to achieve adsorption - desorption equilibrium. Subsequently, it was placed into a photoreaction device for illumination. 4 mL of the suspension was taken every 10 min. Finally, the suspension was placed into a high - speed centrifuge to remove the catalyst, and the supernatant was taken and put into a UV - Vis spectrophotometer to detect the change in the absorbance of methylene blue at 664 nm over time.

[0104] Figure 7 In a, pure KNbO 3 could hardly remove methylene blue, which was similar to that of the blank control group (blank) without a catalyst. This was because the light absorption ability of pure KNbO 3 was too poor to generate photocarriers almost. The photocatalytic activities of pure SnS 2 and the mixture were both poor and similar. Only about 16.6% of methylene blue could be decomposed within 60 min, which was due to the rapid recombination of photogenerated charges. Compared with the pure KNbO 3 catalyst, the pure SnS 2 catalyst, and the mixture, the removal rates of methylene blue by the prepared SnS 2 / KNbO 3 composite photocatalysts were all improved. As shown in Figure 7As shown in a, after 60 min of photocatalytic reaction, the removal rates of methylene blue by SK-20, SK-70, and SK-120 were 87.34%, 26.44%, and 26.62%, respectively. Therefore, SK-20 exhibited the best photocatalytic activity.

[0105] In addition, Figure 7 b shows that SnS 2 / KNbO 3 The reaction kinetic behavior of the composite photocatalyst conforms to pseudo-first-order kinetics. Among them, SK-20 has the largest rate constant, which is 0.0301 min -1 , which are 10 and 60 times that of SnS 2 (0.0030 min -1 ) and KNbO 3 (0.0005 min -1 ), respectively.

[0106] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations. The above-described embodiments are merely preferred embodiments given to fully illustrate the present invention, and the scope of protection thereof is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

Claims

1. A method for preparing a SnS2 / KNbO3 composite photocatalyst, characterized in that: The steps include: Preparation of KNbO3 microblocks; Prepare SnCl4 solution and prepare thioacetamide solution; The KNbO3 microblocks and SnCl4 solution are uniformly mixed to obtain a mixed solution, the thioacetamide solution is dropped into the mixed solution, and then a low-temperature water bath method is used for reaction. After the reaction is completed, the SnS2 / KNbO3 composite photocatalyst is obtained by centrifugation, washing, and vacuum drying. The conditions of the low-temperature water bath method are: reacting at a water bath temperature of 60-90°C for 2-5h. In the SnS2 / KNbO3 composite photocatalyst, the mass ratio of SnS2 to KNbO3 is 400:10-30.

2. The method for preparing a SnS2 / KNbO3 composite photocatalyst according to claim 1, characterized in that: The KNbO3 microblock is prepared by a hydrothermal method, and the specific steps are as follows: Nb2O5 was dispersed in KOH solution, stirred and mixed for 1 hour to obtain a suspension, and the suspension was subjected to hydrothermal reaction. After the reaction was completed, KNbO3 microblocks were obtained after centrifugation, washing and drying.

3. The method for preparing a SnS2 / KNbO3 composite photocatalyst according to claim 2, characterized in that: The mass ratio of KOH to Nb2O5 is 55:2-7, and the conditions of the hydrothermal reaction are: hydrothermal reaction at 140-180°C for 10-16h.

4. The method for preparing a SnS2 / KNbO3 composite photocatalyst according to claim 1, characterized in that: The SnCl4 solution is prepared by mixing SnCl4·5H2O in anhydrous ethanol to obtain a SnCl4 solution; The preparation method of the thioacetamide solution is as follows: thioacetamide powder is mixed in anhydrous ethanol to obtain the thioacetamide solution.

5. The method for preparing a SnS2 / KNbO3 composite photocatalyst according to claim 4, characterized in that: The molar ratio of thioacetamide to SnCl4·5H2O is 2-6:

1.

6. The method for preparing a SnS2 / KNbO3 composite photocatalyst according to claim 1, characterized in that: In the SnS2 / KNbO3 composite photocatalyst, the mass ratio of SnS2 to KNbO3 is 400:

20.

7. A SnS2 / KNbO3 composite photocatalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the SnS2 / KNbO3 composite photocatalyst according to claim 7 in the preparation of a catalyst for photodegradation of methylene blue.

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