Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of wave-absorbing materials, in particular to a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material as well as a preparation method and application thereof. The Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material is prepared by loading Bi clusters and Bi2Sn2O7 nano particles on a two-dimensional ultrathin ZnIn2S4 nano sheet, and the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material is prepared by loading the Bi clusters and the Bi2Sn2O7 nano particles on the two-dimensional According to the Bi-Bi2Sn2O7 / ZnIn2S4 heterojunction developed by the invention, selective oxidation (2362 [mu] mol g <-1 > h <-1 >) from toluene to benzaldehyde is realized under the irradiation of visible light, and the Bi-Bi2Sn2O7 / ZnIn2S4 heterojunction has enhanced photocatalytic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of wave absorbing materials, and in particular to a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material and a preparation method and application thereof. Background Art

[0002] Benzaldehyde is an important chemical raw material, widely used in fine chemical fields such as flavors and fragrances, dyes, medicines, pesticides, additives and synthetic materials industries. At present, the industrial synthesis of benzaldehyde mainly includes the following three processes: toluene chlorination and hydrolysis, benzene direct carbonylation, and toluene gas phase oxidation. The first two methods not only have high requirements on the acid and pressure resistance of production equipment, but the residual chloride ions in the products limit the application of benzaldehyde (especially in the fields of flavors and medicines), and produce a large amount of wastewater, causing environmental pollution. Although the toluene gas phase oxidation method avoids the use of chlorine, has a short process flow and a fast reaction speed, it has the disadvantages of low benzaldehyde selectivity (many deep oxidation by-products) and high energy consumption. Therefore, it is committed to the research and development of efficient and green synthesis processes for benzaldehyde. The preparation of benzaldehyde by photocatalytic toluene oxidation has the advantages of mild reaction conditions, green environmental protection, atom economy and high selectivity of target products, which has attracted great attention from researchers.

[0003] In recent years, multi-layer two-dimensional materials have received extensive attention due to their diversity of components and structures. Among them, ZnIn2S4 is a layered ternary bimetallic sulfide with a direct band gap, which has a series of advantages such as strong light absorption ability, good chemical / thermal stability, environmental friendliness, and adjustable band gap. Due to the existence of a double-layer structure with interlayer interaction forces in ZnIn2S4 single crystal cells, several layers of two-dimensional structures including the double layer of single crystal cells are relatively easy to obtain in experiments and have been shown to be superior to the corresponding bulk materials in terms of photocatalytic performance. In particular, after the reasonable coupling of multi-metal oxide semiconductors with suitable band structures, the potential gradient between the heterogeneous interfaces can effectively accelerate the separation and transfer of photogenerated electrons and improve the activity of photocatalysts in catalytic reactions. To achieve toluene oxidation, the photocatalyst must have sufficient valence band potential to meet the required thermodynamic potential and kinetic overpotential. Constructing a heterojunction consisting of two visible light responsive semiconductors is a promising solution. Summary of the invention

[0004] In view of the problems that the existing technology can effectively improve the photocatalytic oxidation of toluene by transition metal sulfides, the activity is weak, the selectivity is low, and the cyclic stability is poor, the present invention provides a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material and its preparation method and application. The preparation process is simple, easy to control and the production cost is low. The prepared Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material has the characteristics of high activity, good selectivity and excellent cyclic stability.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The invention provides a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, which is composed of Bi clusters and Bi2Sn2O7 nanoparticles loaded on two-dimensional ultra-thin ZnIn2S4 nanosheets.

[0007] The present invention also provides a method for preparing the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material described in the above technical solution, comprising the following steps:

[0008] 1) mixing zinc acetate, water, indium chloride and thioacetamide, and performing a hydrothermal reaction, and obtaining a ZnIn2S4 nanomaterial after drying;

[0009] 2) mixing the ZnIn2S4 nanomaterial obtained in step 1) with water, bismuth nitrate, polyvinyl pyrrolidone and mannitol to obtain solution A;

[0010] Mix sodium stannate and water to obtain solution B;

[0011] Mixing the A solution and the B solution to obtain a suspension;

[0012] 3) reacting and drying the suspension obtained in step 2) to obtain a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material.

[0013] Preferably, in step 1), the molar ratio of zinc acetate, the volume of water, the molar ratio of indium chloride and thioacetamide is 0.4 mmol:30 mL:0.8 mmol:1.6 mmol.

[0014] Preferably, the conditions for the hydrothermal reaction in step 1) include: heating to 180° C. at a heating rate of 5° C. / min and keeping the temperature for 24 hours.

[0015] Preferably, in step 2), the molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the mole of mannitol is 0.2-0.5 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

[0016] Preferably, the molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the mole of mannitol is 0.3-0.4 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

[0017] Preferably, in step 2), the volume ratio of the mole of sodium stannate to water is 1 mmol:10 mL.

[0018] Preferably, the reaction conditions of step 3) include: heating to 160° C. at a heating rate of 5° C. / min and keeping the temperature for 12 h.

[0019] Preferably, the drying conditions in step 1) and step 3) include: a temperature of 80° C. and a drying time of 12 hours.

[0020] The present invention also provides the use of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material described in the above technical solution in catalyzing toluene to generate benzaldehyde.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention first dissolves zinc acetate dihydrate in distilled water, then adds indium chloride and thioacetamide (TAA) as auxiliary hydrothermal preparation of ZnIn2S4 nanomaterials, and then prepares Bi single substance clusters and Bi2Sn2O7-loaded ZnIn2S4 nanosheets by in-situ growth to form Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials. The preparation process of the precursor of the present invention is simple, the morphology is unique, the cost is low, and the operation can be repeated.

[0023] 2. The present invention prepares a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material with a 1D / 2D structure by a two-step hydrothermal method. This unique 1D / 2D structural design not only provides a larger specific surface area and abundant reaction sites for the photocatalytic reaction, but also ensures sufficient contact between ZnIn2S4 and Bi2Sn2O7 with visible light activity. The presence of Bi clusters has the ability to adsorb / activate carbon dioxide, thereby effectively promoting the separation and transfer of photogenerated electrons and holes. The developed Bi-Bi2Sn2O7 / ZnIn2S4 heterojunction achieves selective oxidation of toluene to benzaldehyde (2362 μmol g - 1 h -1 ), with enhanced photocatalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0025] Figure 1 X-ray diffraction patterns of ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2 of the present invention;

[0026] Figure 2is a scanning electron microscope image of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material prepared in Example 2 of the present invention;

[0027] Figure 3 is a rate curve diagram of oxidation of toluene to benzaldehyde under visible light irradiation of different samples prepared in Example 1 of the present invention;

[0028] Figure 4 is a rate curve of oxidation of toluene to benzaldehyde under visible light irradiation of Bi-Bi2Sn2O7 (x%) / ZnIn2S4 composite photocatalytic materials with different Bi-Bi2Sn2O7 contents prepared in Example 2;

[0029] Figure 5 This is a cyclic stability curve of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material prepared in Example 3 of the present invention, which is oxidized from toluene to benzaldehyde under visible light irradiation. DETAILED DESCRIPTION

[0030] The invention provides a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, which is composed of Bi clusters and Bi2Sn2O7 nanoparticles loaded on two-dimensional ultra-thin ZnIn2S4 nanosheets.

[0031] The present invention also provides a method for preparing the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material described in the above technical solution, comprising the following steps:

[0032] 1) mixing zinc acetate, water, indium chloride and thioacetamide, performing a hydrothermal reaction, and obtaining a ZnIn2S4 nanomaterial after drying;

[0033] 2) mixing the ZnIn2S4 nanomaterial obtained in step 1) with water, bismuth nitrate, polyvinyl pyrrolidone and mannitol to obtain solution A;

[0034] Mix sodium stannate and water to obtain solution B;

[0035] Mixing the A solution and the B solution to obtain a suspension;

[0036] 3) reacting and drying the suspension obtained in step 2) to obtain a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material.

[0037] The invention mixes zinc acetate, water, indium chloride and thioacetamide, performs hydrothermal reaction, and obtains ZnIn2S4 nanometer material after drying.

[0038] In the present invention, the molar ratio of the zinc acetate, the volume of water, the molar ratio of indium chloride and thioacetamide is preferably 0.4mmol:30mL:0.8mmol:1.6mmol. In the present invention, the zinc acetate is preferably zinc acetate dihydrate. In the present invention, the conditions of the hydrothermal reaction preferably include: heating to 180°C at a heating rate of 5°C / min and keeping warm for 24h. The present invention preferably cools to room temperature after the hydrothermal reaction, washes the reaction product alternately with anhydrous ethanol and distilled water three times, obtains a yellow solid product after filtering, and then dries to obtain a ZnIn2S4 nanomaterial. In the present invention, the drying conditions preferably include: a temperature of 80°C and a time of 12h.

[0039] The invention mixes the obtained ZnIn2S4 nano material with water, bismuth nitrate, polyvinyl pyrrolidone and mannitol to obtain solution A; mixes sodium stannate and water to obtain solution B; and mixes solution A and solution B to obtain a suspension.

[0040] In the present invention, the molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the molar ratio of mannitol is preferably 0.2-0.5g:20mL:1mmol:0.2mmol:1.5mmol. In the present invention, the molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the molar ratio of mannitol is preferably 0.3-0.4g:20mL:1mmol:0.2mmol:1.5mmol. In the present invention, the mole of sodium stannate and the volume ratio of water are preferably 1mmol:10mL. In the present invention, the bismuth nitrate is preferably bismuth nitrate pentahydrate, and the sodium stannate is preferably sodium stannate trihydrate.

[0041] The present invention reacts and dries the obtained suspension to obtain a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material. In the present invention, the reaction conditions preferably include: heating to 160°C at a heating rate of 5°C / min and keeping warm for 12 hours. The present invention preferably cools to room temperature after the reaction is completed, washes the reaction product alternately with anhydrous ethanol and distilled water three times, obtains a dark gray solid product after filtering, and then dries. In the present invention, the drying conditions preferably include: temperature of 80°C and time of 12 hours.

[0042] The present invention also provides the use of Bi-Bi2Sn2O7 / ZnIn2S4 described in the above technical solution in catalyzing toluene to produce benzaldehyde.

[0043] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing a one-dimensional rod-shaped Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, comprising the following steps:

[0046] (1) Take 0.4mmol Zn(CH3COO)2·2H2O and dissolve it in 30mL deionized water. After stirring the solution at room temperature for 10min, add 0.8mmol InCl3 and 1.6mmol thioacetamide (TAA) to obtain a colorless solution. Then, transfer the mixed solution to a reactor, place the reactor in an electric heating blast drying oven, heat it to 180℃ at a heating rate of 5℃ / min, keep it warm for 24h, cool it to room temperature after the reaction is completed, wash the reaction product with anhydrous ethanol and distilled water alternately for 3 times, filter it to obtain a yellow solid product, and dry it at 80℃ for 12h to obtain ZnIn2S4 nanomaterials;

[0047] (2) 0.5 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by the addition of 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinyl pyrrolidone) and 1.5 mmol of D-mannitol, and the mixture was stirred to obtain solution A. Subsequently, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water to obtain solution B. Solution B was slowly added to solution A and stirred for 1 h to form a white suspension.

[0048] (3) The white suspension was transferred to a reactor, and the reactor was placed in an electric heated forced air drying oven. The temperature was raised to 160°C at a heating rate of 5°C / min, and the reaction was kept warm for 12 hours. After the reaction was completed, it was cooled to room temperature. The reaction product was washed alternately with anhydrous ethanol and distilled water for three times, and a dark gray solid product was obtained after filtration. After drying at 80°C for 12 hours, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; it was recorded as B-BSO / ZIS-1.

[0049] Example 2

[0050] A preparation method of a one-dimensional rod-shaped Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material and the steps thereof are:

[0051] (1) Take 0.4mmol Zn(CH3COO)2·2H2O and dissolve it in 30mL deionized water. After stirring the solution at room temperature for 10min, add 0.8mmol InCl3 and 1.6mmol thioacetamide (TAA) to obtain a colorless solution. Then, transfer the mixed solution to a reactor, place the reactor in an electric heating blast drying oven, heat it to 180℃ at a heating rate of 5℃ / min, keep it warm for 24h, cool it to room temperature after the reaction is completed, wash the reaction product with anhydrous ethanol and distilled water alternately for 3 times, filter it to obtain a yellow solid product, and dry it at 80℃ for 12h to obtain ZnIn2S4 nanomaterials;

[0052] (2) 0.4 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by the addition of 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinyl pyrrolidone) and 1.5 mmol of D-mannitol, and the mixture was stirred to obtain solution A. Subsequently, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water to obtain solution B. Solution B was slowly added to solution A and stirred for 1 h to form a white suspension.

[0053] (3) The white suspension was transferred to a reactor, and the reactor was placed in an electric heated forced air drying oven. The temperature was raised to 160°C at a heating rate of 5°C / min, and the reaction was kept warm for 12 hours. After the reaction was completed, it was cooled to room temperature. The reaction product was washed alternately with anhydrous ethanol and distilled water for 3 times, and a dark gray solid product was obtained after filtration. After drying at 80°C for 12 hours, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; it was recorded as B-BSO / ZIS-2.

[0054] Example 3

[0055] A method for preparing a one-dimensional rod-shaped Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, comprising the following steps:

[0056] (1) Take 0.4mmol Zn(CH3COO)2·2H2O and dissolve it in 30mL deionized water. After stirring the solution at room temperature for 10min, add 0.8mmol InCl3 and 1.6mmol thioacetamide (TAA) to obtain a colorless solution. Then, transfer the mixed solution to a reactor, place the reactor in an electric heating blast drying oven, heat it to 180℃ at a heating rate of 5℃ / min, keep it warm for 24h, cool it to room temperature after the reaction is completed, wash the reaction product with anhydrous ethanol and distilled water alternately for 3 times, filter it to obtain a yellow solid product, and dry it at 80℃ for 12h to obtain ZnIn2S4 nanomaterials;

[0057] (2) 0.3 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by the addition of 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinyl pyrrolidone) and 1.5 mmol of D-mannitol, and the mixture was stirred to obtain solution A. Subsequently, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water to obtain solution B. Solution B was slowly added to solution A and stirred for 1 h to form a white suspension.

[0058] (3) The white suspension was transferred to a reactor, and the reactor was placed in an electric heated forced air drying oven. The temperature was raised to 160°C at a heating rate of 5°C / min, and the reaction was kept warm for 12 hours. After the reaction was completed, it was cooled to room temperature. The reaction product was washed alternately with anhydrous ethanol and distilled water for 3 times, and a dark gray solid product was obtained after filtration. After drying at 80°C for 12 hours, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; it was recorded as B-BSO / ZIS-3.

[0059] Example 4

[0060] A method for preparing a one-dimensional rod-shaped Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, comprising the following steps:

[0061] (1) Take 0.4mmol Zn(CH3COO)2·2H2O and dissolve it in 30mL deionized water. After stirring the solution at room temperature for 10min, add 0.8mmol InCl3 and 1.6mmol thioacetamide (TAA) to obtain a colorless solution. Then, transfer the mixed solution to a reactor, place the reactor in an electric heating blast drying oven, heat it to 180℃ at a heating rate of 5℃ / min, keep it warm for 24h, cool it to room temperature after the reaction is completed, wash the reaction product with anhydrous ethanol and distilled water alternately for 3 times, filter it to obtain a yellow solid product, and dry it at 80℃ for 12h to obtain ZnIn2S4 nanomaterials;

[0062] (2) 0.2 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by the addition of 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinyl pyrrolidone) and 1.5 mmol of D-mannitol, and the mixture was stirred to obtain solution A. Subsequently, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water to obtain solution B. Solution B was slowly added to solution A and stirred for 1 h to form a white suspension.

[0063] (3) The white suspension was transferred to a reactor, and the reactor was placed in an electric forced air drying oven. The temperature was raised to 160°C at a heating rate of 5°C / min, and the reaction was kept warm for 12 hours. After the reaction was completed, it was cooled to room temperature. The reaction product was washed alternately with anhydrous ethanol and distilled water for 3 times, and a dark gray solid product was obtained after filtration. After drying at 80°C for 12 hours, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; it was recorded as B-BSO / ZIS-4.

[0064] Performance Test:

[0065] 1. The phase structure of the Bi-Bi2Sn2O7 / ZnIn2S4 material of Example 3 was analyzed by X-ray diffractometer (XRD).

[0066] Figure 1 XRD patterns of ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 prepared in Example 2. Figure 1 The successful preparation of Bi-Bi2Sn2O7 / ZnIn2S4 composite can be demonstrated. Figure 1 The diffraction peaks of Bi, Bi2Sn2O7 and ZnIn2S4 can be observed simultaneously. The diffraction peaks at 2θ=28.6° and 48.7° belong to Bi2Sn2O7, and the corresponding standard PDF card (JCPDS No.87-0284) has crystal plane indices of (222) and (440) respectively. Meanwhile, the diffraction peaks of Bi are at diffraction angles of 2θ=27.1°, 38.0°, 39.7°, 45.9°, 56.0°, 62.1°, 64.5° and 70.8°, and the corresponding standard PDF card (JCPDS No.44-1246) of Bi has crystal plane indices of (011), (101), (111), (211), (002), (031), (131) and (240) respectively. In addition, the diffraction peaks of ZIS are at diffraction angles 2θ = 21.4°, 27.5°, 30.4°, 39.1°, 47.1°, 52.1°, 55.8° and 76.2°, and the crystal plane indices corresponding to the standard PDF card of ZIS (JCPDS No.65-2023) are (006), (102), (104), (108), (110), (116), (022) and (213). In the composite material, the diffraction peaks of Bi, Bi2Sn2O7 and ZnIn2S4 exist at the same time. The results show that the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was successfully prepared.

[0067] 2. The microstructure of Bi-Bi2Sn2O7, ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2 was analyzed using a scanning electron microscope (SEM).

[0068] Figure 2 SEM images of Bi-Bi2Sn2O7, ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2. Figure 2 (A) is the SEM image of ZnIn2S4. It can be seen that ZnIn2S4 presents a nanosheet structure of different sizes, ranging from nanometers to micrometers, with thin sheets and smooth surfaces. Figure 2 (B) is the SEM image of Bi-Bi2Sn2O7. It can be clearly seen from the figure that Bi-Bi2Sn2O7 is in a nanoparticle state and some particles are aggregated. The particle size is 4 to 7 nm and the average size is about 6 nm. Figure 2 (C) and (D) are SEM images of Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials. It can be clearly seen from the figure that the composite presents a thinner sheet structure with a size ranging from nanometers to micrometers, which is consistent with the size of pure ZnIn2S4 nanosheets. In addition, a layer of nanoscale granular Bi-Bi2Sn2O7 is uniformly loaded on the surface of the sheet, with a size of 5.5nm±1.5nm, which is consistent with the size of pure Bi-Bi2Sn2O7 nanoparticles. Bi-Bi2Sn2O7 nanoparticles are uniformly loaded on the surface of ZnIn2S4 nanosheets, which can not only produce more heterogeneous interfaces, thereby promoting the separation and transfer of interfacial charges, but also provide more reactive sites, enhancing the photocatalytic oxidation of toluene.

[0069] 3. The photocatalytic toluene oxidation performance of the sample was analyzed by a photocatalytic reaction system, and the analysis results are shown below.

[0070] Figure 3 Schematic diagram of the toluene oxidation performance results of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material prepared in Example 2. Toluene oxidation first produces benzyl alcohol, which further produces benzaldehyde. Therefore, the selective production of benzaldehyde from toluene is the primary goal. Photocatalytic toluene oxidation measurements were performed on a laboratory Solar-IIIAG system (Beijing Perfectlight Co., Ltd.). In the toluene photocatalytic process, the synthesized B-BSO / ZIS product was first dispersed in water to obtain about 2 mg ml -1The concentration was 200 μL, and 2 ml of toluene was added as a reactant. Light irradiation was provided by a Microsolar 300 xenon lamp (Microsolar 300 xenon light source, from Beijing Perfectlight Technology Co., Ltd.) with a 420 nm cutoff filter to simulate visible light. The output light power was approximately 50 mW cm -2 . Note that the distance from the light source to the reactor sample is about 10 cm. During the photoluminescence process, the final product of the reaction was characterized by identifying the chromatographic peaks using a Techcomp GC7900 gas chromatograph (FID detector, TDX-01 column). During the irradiation process, the solution temperature was controlled in the range of 298 ± 0.2 K by a circulating cooling water system. It can be seen from the figure that pure Bi-Bi2Sn2O7 exhibits low photocatalytic oxidation activity for toluene. Due to its low self-oxidation activity, the rate of generating benzyl alcohol reached 225 μmol g within 5 h. -1 h -1 , while the generation rate of benzaldehyde was only 163 μmol g -1 h -1 Monomer ZnIn2S4 also showed low activity in the photocatalytic oxidation of toluene, with the rate of producing benzyl alcohol reaching 153 μmol g in 5 h. -1 h -1 , while the generation rate of benzaldehyde was 326 μmol g -1 h -1 The low toluene oxidation activity and selectivity of Bi-Bi2Sn2O7 and ZnIn2S4 may be attributed to the rapid recombination of the generated photogenerated carriers and the problem of photocorrosion. When Bi-Bi2Sn2O7 nanoparticles were loaded onto the surface of ZnIn2S4 nanosheets, the activity and selectivity of photocatalytic toluene oxidation were greatly enhanced. The rate of generating benzyl alcohol in 5 hours was only 48 μmol g -1 h -1 , while the generation rate of benzaldehyde was 2362 μmol g -1 h -1 The selectivity reached 98%. The enhanced photocatalytic activity is attributed to the construction of the S-type charge transfer mechanism between Bi-Bi2Sn2O7 and ZnIn2S4, which maintains the spatial separation of electrons and holes and the strongest redox potential.

[0071] Figure 4This is a schematic diagram of the photocatalytic toluene oxidation activity of Bi-Bi2Sn2O7 nanoparticles with different contents loaded on the surface of ZnIn2S4 nanosheets. As can be seen from the figure, as the Bi-Bi2Sn2O7 content gradually increases, its photocatalytic toluene oxidation activity shows a volcano-like trend of first increasing and then decreasing. This may be because an appropriate amount of Bi-Bi2Sn2O7 helps promote the separation and rapid transfer of photogenerated charges, while an excessive amount of Bi-Bi2Sn2O7 may become the center of electron recombination, resulting in rapid recombination of electron-hole pairs and a decrease in the photocatalytic toluene oxidation activity.

[0072] Figure 5 This is a cyclic stability test of Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalyst. The stability of the catalyst is also one of the indicators for evaluating its large-scale industrial application (Note: the photocatalytic cyclic stability test, each cycle is 5 hours, a total of 5 cycles are tested.) The test results show that in the first cycle, the generation rate of benzaldehyde within 5 hours is 2364μmol g -1 h -1 After five cycles, the generation rate of benzaldehyde still reached 2272 μmol g -1 h -1 , which is only 3.9% lower than the first cycle. This result further shows that the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalyst not only has strong photocatalytic toluene oxidation activity, but also has excellent cycle stability. It can be used as one of the candidate catalysts for the selective oxidation of toluene to benzaldehyde, with excellent practical value and broad industrial application prospects.

[0073] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, characterized in that: It is composed of Bi clusters and Bi2Sn2O7 nanoparticles loaded into two-dimensional ultrathin ZnIn2S4 nanosheets.

2. A method for preparing the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material according to claim 1, characterized in that: The following steps are involved: 1) mixing zinc acetate, water, indium chloride and thioacetamide, performing a hydrothermal reaction, and obtaining a ZnIn2S4 nanomaterial after drying; 2) mixing the ZnIn2S4 nanomaterial obtained in step 1) with water, bismuth nitrate, polyvinyl pyrrolidone and mannitol to obtain solution A; Mix sodium stannate and water to obtain solution B; Mixing the A solution and the B solution to obtain a suspension; 3) reacting and drying the suspension obtained in step 2) to obtain a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material.

3. The preparation method according to claim 2, characterized in that: In the step 1), the molar ratio of zinc acetate, the volume of water, the molar ratio of indium chloride and thioacetamide is 0.4mmol:30mL:0.8mmol:1.6mmol.

4. The preparation method according to claim 2, characterized in that: The conditions of the hydrothermal reaction in step 1) include: heating to 180° C. at a heating rate of 5° C. / min and keeping the temperature for 24 hours.

5. The preparation method according to claim 2, characterized in that: In the step 2), the molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the mole of mannitol is 0.2-0.5 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

6. The preparation method according to claim 2 or 5, characterized in that: The molar ratio of the mass of the ZnIn2S4 nanomaterial to the volume of water, the mole of bismuth nitrate, the mole of polyvinyl pyrrolidone, and the mole of mannitol is 0.3-0.4 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

7. The preparation method according to claim 2, characterized in that: In the step 2), the volume ratio of the mole of sodium stannate to water is 1 mmol:10 mL.

8. The preparation method according to claim 2, characterized in that: The reaction conditions of step 3) include: heating to 160° C. at a heating rate of 5° C. / min and keeping the temperature for 12 hours.

9. The preparation method according to claim 2, characterized in that: The drying conditions in step 1) and step 3) both include: a temperature of 80° C. and a drying time of 12 hours.

10. Use of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material according to claim 1 in catalyzing toluene to produce benzaldehyde.

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