Bi-bi2sn2o7 / ZnIn2S4 composite photocatalytic material and preparation method and application thereof

Abstract

The application relates to the technical field of wave-absorbing materials, in particular to a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material and a preparation method and application thereof. The Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material is composed of Bi clusters and Bi2Sn2O7 nanoparticles loaded on two-dimensional ultrathin ZnIn2S4 nanosheets. The Bi-Bi2Sn2O7 / ZnIn2S4 heterojunction developed by the application realizes selective oxidation of toluene to benzaldehyde (2362 mu mol g ‑ 1 h ‑1 ) under visible light irradiation, and has enhanced photocatalytic activity.

Description

TECHNICAL FIELD

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

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

[0003] In recent years, due to the diversity of components and structures, multi-element two-dimensional materials have attracted extensive attention. 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 capacity, good chemical / thermal stability, environmental friendliness, and adjustable band gap. Due to the double-layer structure of the interlayer interaction force in the ZnIn2S4 single crystal cell, several two-dimensional structures including the double-layer of the single crystal cell are relatively easy to obtain in experiments, and have been proved to be superior to the corresponding bulk materials in terms of photocatalytic performance. Especially after reasonably coupling with multi-metal oxide semiconductors with suitable energy band structures, the potential gradient between the heterojunctions can effectively accelerate the separation and transfer of photo-generated electrons, and improve the activity of the photocatalyst in the catalytic reaction. To realize the oxidation of toluene, the photocatalyst must have sufficient valence band potential to meet the required thermodynamic potential and kinetic overpotential. Constructing a heterojunction composed of two visible light responsive semiconductors is a very promising solution. SUMMARY

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

[0005] To achieve the above object, the present application provides the following technical solutions.

[0006] The present application provides a kind of Bi-Bi2Sn2O7 / ZnIn2S4 Composite photocatalytic material, it is by Bi cluster and Bi2Sn2O7 Nanoparticle is loaded to two-dimensional ultrathin ZnIn2S4 Nanosheet composition.

[0007] The present application also provides a kind of Bi-Bi2Sn2O7 / ZnIn2S4 Composite photocatalytic material described in the above technical solutions Preparation method, comprising the following steps:

[0008] 1) after mixing zinc acetate, water, indium chloride, thioacetamide, hydrothermal reaction is carried out, after drying, ZnIn2S4 Nanometer material is obtained;

[0009] 2) the ZnIn2S4 Nanometer material of step 1) is mixed with water, bismuth nitrate, polyvinylpyrrolidone, mannitol, to obtain A solution;

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

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

[0012] 3) the suspension of step 2) is reacted, dried, to obtain Bi-Bi2Sn2O7 / ZnIn2S4 Composite photocatalytic material.

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

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

[0015] Preferably, the mass of ZnIn2S4 Nanometer material, the volume of water, the molar of bismuth nitrate, the molar of polyvinylpyrrolidone and the molar of mannitol in step 2) are 0.2-0.5 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

[0016] Preferably, the mass of ZnIn2S4 Nanometer material, the volume of water, the molar of bismuth nitrate, the molar of polyvinylpyrrolidone and the molar of mannitol in step 2) are 0.3-0.4 g:20 mL:1 mmol:0.2 mmol:1.5 mmol.

[0017] Preferably, the molar of sodium stannate and the volume of water in step 2) are 1 mmol:10 mL.

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

[0019] Preferably, the drying conditions of the step 1) and the step 3) both include: temperature of 80℃, and time of 12h.

[0020] The application further provides application of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material in catalyzing toluene to generate benzaldehyde.

[0021] The application has the following beneficial effects:

[0022] 1. Firstly, zinc acetate dihydrate is dissolved in distilled water, then indium chloride and thioacetamide (TAA) are added to prepare ZnIn2S4 nanomaterial by assisted hydrothermal method, then Bi elemental clusters and Bi2Sn2O7 are loaded on the ZnIn2S4 nanosheet by in-situ growth to form the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, the preparation process of the precursor is simple, the morphology is unique, the cost is low, and the operation can be repeated.

[0023] 2. The Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material with 1D / 2D structure is prepared by two-step hydrothermal method, the unique 1D / 2D structure design not only provides a larger specific surface area and rich reaction sites for photocatalytic reaction, but also ensures the sufficient contact of ZnIn2S4 and Bi2Sn2O7 with visible light activity, and the existence of Bi clusters has the ability of carbon dioxide adsorption / activation, thereby effectively promoting the separation and transfer of photo-generated electrons and holes; the developed Bi-Bi2Sn2O7 / ZnIn2S4 heterojunction realizes the selective oxidation of toluene to benzaldehyde (2362μmol g - 1 h -1 ) under visible light irradiation, and has enhanced photocatalytic activity. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

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

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

[0029] Figure 5 is a cycle stability curve diagram of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material prepared in Example 3 under visible light irradiation for oxidation of toluene into benzaldehyde. DETAILED DESCRIPTION

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

[0031] The present application also provides a preparation method of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, which comprises the following steps:

[0032] 1) mixing zinc acetate, water, indium chloride and thioacetamide, and then performing hydrothermal reaction, and drying to obtain ZnIn2S4 nanomaterials;

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

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

[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 the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material.

[0037] The present application mixes zinc acetate, water, indium chloride and thioacetamide, and then performs hydrothermal reaction, and dries to obtain ZnIn2S4 nanomaterials.

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

[0039] The ZnIn2S4 nanomaterial obtained in the present application is mixed with water, bismuth nitrate, polyvinylpyrrolidone and mannitol to obtain solution A; sodium stannate and water are mixed to obtain solution B; the solutions A and B are mixed to obtain a suspension.

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

[0041] The suspension obtained in the present application is reacted and dried to obtain a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material. In the present application, the conditions of the reaction preferably include: heating to 160℃ at a heating rate of 5℃ / min, and keeping for 12h. The present application preferably cools to room temperature after the reaction, and the reaction product is washed with anhydrous ethanol and distilled water alternately for three times, and then filtered to obtain a dark gray solid product, which is dried. In the present application, the conditions of the drying preferably include: temperature of 80℃, and time of 12h.

[0042] The present application also provides the use of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material in the catalysis of toluene to benzaldehyde.

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

[0044] Example 1

[0045] A preparation method of a one-dimensional rod-like structure Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, the steps are:

[0046] (1) 0.4 mmol Zn(CH3COO)2·2H2O was dissolved in 30 mL of deionized water, and after the solution was stirred at room temperature for 10 min, 0.8 mmol of InCl3 and 1.6 mmol of thioacetamide (TAA) were added to obtain a colorless solution. Then, the mixed solution was transferred to a reaction kettle, the reaction kettle was placed in an electric heating air drying oven, and the temperature was raised to 180℃ at a heating rate of 5℃ / min, and the reaction was kept for 24 h. After the reaction was completed, it was cooled to room temperature, and the reaction product was washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a yellow solid product. After drying at 80℃ for 12 h, ZnIn2S4 nanomaterial was obtained;

[0047] (2) 0.5 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by adding 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinylpyrrolidone) and 1.5 mmol of D-mannitol, and stirring to obtain a homogeneous mixture as A solution; then, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water as B solution. The B solution was slowly added to the A solution, and after stirring for 1 h, a white suspension was formed.

[0048] (3) The white suspension was transferred to a reaction kettle, the reaction kettle was placed in an electric heating air drying oven, and the temperature was raised to 160℃ at a heating rate of 5℃ / min, and the reaction was kept for 12 h. After the reaction was completed, it was cooled to room temperature, and the reaction product was washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a dark gray solid product. After drying at 80℃ for 12 h, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; denoted as B-BSO / ZIS-1.

[0049] Example 2

[0050] A preparation method of a one-dimensional rod-like structure Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, the steps are:

[0051] (1) 0.4 mmol Zn(CH3COO)2·2H2O was dissolved in 30 mL deionized water, after the solution was stirred at room temperature for 10 min, 0.8 mmol InCl3 and 1.6 mmol thioacetamide (TAA) were added to obtain a colorless solution. Then, the mixed solution was transferred to a reaction kettle, the reaction kettle was placed in an electric heating drying oven, and the temperature was raised to 180℃ at a rate of 5℃ / min, and the reaction was kept for 24 h. After the reaction was completed, it was cooled to room temperature, and the reaction product was washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a yellow solid product. After drying at 80℃ for 12 h, ZnIn2S4 nanomaterial was obtained;

[0052] (2) 0.4 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by adding 1 mmol Bi(NO3)3·5H2O, 0.2 mmol PVP (polyvinylpyrrolidone) and 1.5 mmol D-mannitol, and stirring to obtain a homogeneous mixture as an A solution; then, 1 mmol Na2SnO3·3H2O was dissolved in 10 mL of distilled water as a B solution. The B solution was slowly added to the A solution, and stirred for 1 h to form a white suspension.

[0053] (3) The white suspension was transferred to a reaction kettle, and the reaction kettle was placed in an electric heating drying oven, and the temperature was raised to 160℃ at a rate of 5℃ / min, and the reaction was kept for 12 h. After the reaction was completed, it was cooled to room temperature, and the reaction product was washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a dark gray solid product. After drying at 80℃ for 12 h, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained; denoted as B-BSO / ZIS-2.

[0054] Example 3

[0055] A preparation method of a one-dimensional rod-like structure Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, comprising the following steps:

[0056] (1) 0.4 mmol Zn(CH3COO)2·2H2O was dissolved in 30 mL deionized water, after the solution was stirred at room temperature for 10 min, 0.8 mmol InCl3 and 1.6 mmol thioacetamide (TAA) were added to obtain a colorless solution. Then, the mixed solution was transferred to a reaction kettle, the reaction kettle was placed in an electric heating drying oven, and the temperature was raised to 180℃ at a rate of 5℃ / min, and the reaction was kept for 24 h. After the reaction was completed, it was cooled to room temperature, and the reaction product was washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a yellow solid product. After drying at 80℃ for 12 h, ZnIn2S4 nanomaterial was obtained;

[0057] (2) 0.3 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by adding 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinylpyrrolidone) and 1.5 mmol of D-mannitol, and stirring to mix uniformly as an A solution; then, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water as a B solution. The B solution was slowly added to the A solution, and a white suspension was formed after stirring for 1 h.

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

[0059] Example 4

[0060] A preparation method of a one-dimensional rod-like structure Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material, the steps are:

[0061] (1) 0.4 mmol of Zn(CH3COO)2·2H2O was dissolved in 30 mL of deionized water, and the solution was stirred at room temperature for 10 min. Then, 0.8 mmol of InCl3 and 1.6 mmol of thioacetamide (TAA) were added to obtain a colorless solution. Then, the mixed solution was transferred to a reaction kettle, the reaction kettle was placed in an electric heating drying oven, and the temperature was raised to 180℃ at a temperature raising rate of 5℃ / min, and the reaction was kept for 24 h. After the reaction was completed, the reaction product was cooled to room temperature, and washed with anhydrous ethanol and distilled water alternately for 3 times. After filtration, a yellow solid product was obtained. After drying at 80℃ for 12 h, a ZnIn2S4 nanomaterial was obtained;

[0062] (2) 0.2 g of ZnIn2S4 was dissolved in 20 mL of distilled water, followed by adding 1 mmol of Bi(NO3)3·5H2O, 0.2 mmol of PVP (polyvinylpyrrolidone) and 1.5 mmol of D-mannitol, and stirring to mix uniformly as an A solution; then, 1 mmol of Na2SnO3·3H2O was dissolved in 10 mL of distilled water as a B solution. The B solution was slowly added to the A solution, and a white suspension was formed after stirring for 1 h.

[0063] (3) The white suspension was transferred to a reaction kettle, which was placed in an electric heating drying oven and heated to 160°C at a heating rate of 5°C / min, and kept for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, washed with anhydrous ethanol and distilled water alternately for 3 times, and then filtered to obtain a dark gray solid product. After drying at 80°C for 12 h, a Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material was obtained, which was denoted as B-BSO / ZIS-4.

[0064] Performance test:

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

[0066] Figure 1 XRD patterns of ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 prepared in Example 2. From the XRD pattern of the composite material, it can be seen that 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, corresponding to the standard PDF card (JCPDS No. 87-0284), and the crystal face indices are (222) and (440), respectively. At the same time, the diffraction peaks of Bi are at diffraction angles 2θ = 27.1°, 38.0°, 39.7°, 45.9°, 56.0°, 62.1°, 64.5° and 70.8°, corresponding to the standard PDF card of Bi (JCPDS No. 44-1246), and the crystal face indices are (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°, corresponding to the standard PDF card of ZIS (JCPDS No. 65-2023), and the crystal face indices are (006), (102), (104), (108), (110), (116), (022) and (213), respectively. In the composite material, the diffraction peaks of Bi, Bi2Sn2O7 and ZnIn2S4 exist simultaneously. The results show that the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material is successfully prepared. Figure 1 Figure 1

[0067] ​​2. The microstructure of Bi-Bi2Sn2O7, ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2 were analyzed by scanning electron microscopy (SEM).

[0068] Figure 2 SEM images of Bi-Bi2Sn2O7, ZnIn2S4 and Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2. Figure 2 The SEM image of (A) is ZnIn2S4, which can be seen that ZnIn2S4 presents different size nanosheet structure, size is in nanometer to micrometer level, sheet is thin and surface is smooth. Figure 2 The SEM image of (B) is Bi-Bi2Sn2O7, which can be clearly seen from the figure that Bi-Bi2Sn2O7 presents nanometer particle state and part of the particles presents aggregate state, particle size is 4-7 nm, average size is about 6 nm. Figure 2 The SEM images of (C) and (D) are Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials, which can be clearly seen from the figure that the composite presents thin sheet structure, size is in nanometer to micrometer level, which is consistent with the size of pure ZnIn2S4 nanosheet. In addition, a layer of nanometer particle Bi-Bi2Sn2O7 is uniformly loaded on the surface of the sheet, size is 5.5 nm ± 1.5 nm, which is consistent with the size of pure Bi-Bi2Sn2O7 nanometer particle. Bi-Bi2Sn2O7 nanometer particles are uniformly loaded on the surface of ZnIn2S4 nanosheet, which not only can produce more heterojunction interfaces, thereby promoting the separation and transmission of interface charge, but also can provide more reaction active sites to enhance the photocatalytic oxidation of toluene.

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

[0070] Figure 3 The toluene oxidation performance results of Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic materials prepared in Example 2 are shown in the schematic diagram. Toluene oxidation first generates benzyl alcohol, and further generates benzaldehyde. Therefore, the selective generation of benzaldehyde from toluene is the primary goal. The photocatalytic toluene oxidation measurement was carried out on a laboratory Solar-III AG system (Beijing Perfectlight Co., Ltd.). In the process of photocatalytic toluene, the synthesized B-BSO / ZIS product was first dispersed in water to obtain about 2 mg·ml -1concentration, and 2 ml of toluene was added as a reactant. Light irradiation was provided by a Microsolar 300 xenon light (Microsolar 300 xenon light source from Beijing Perfectlight Technology Co., Ltd.) with a 420 nm cut-off filter to simulate visible light. The output optical power was about 50 milliwatts centimeter -2 . Please note that the distance from the light source to the reactor sample was about 10 centimeters. During the photoluminescence process, the final product of the reaction was characterized by identifying the chromatographic peaks with a Techcomp GC7900 gas chromatograph (FID detector, TDX-01 column). During irradiation, the solution temperature was controlled in the range of 298 ± 0.2 k by a circulating cooling water system. As can be seen from the figure, pure Bi-Bi2Sn2O7 exhibited lower photocatalytic activity for the oxidation of toluene, and due to its own low oxidation activity, the rate of benzyl alcohol generated in 5 hours reached 225 μmol g -1 h -1 , and the rate of benzaldehyde generated was only 163 μmol g -1 h -1 . Monomer ZnIn2S4 also exhibited lower photocatalytic activity for the oxidation of toluene, and the rate of benzyl alcohol generated in 5 hours reached 153 μmol g -1 h -1 , and the rate of benzaldehyde generated was 326 μmol g -1 h -1 . The lower toluene oxidation activity and selectivity of Bi-Bi2Sn2O7 and ZnIn2S4 may be attributed to the rapid recombination of photo-generated carriers and the problem of photo-corrosion. After loading Bi-Bi2Sn2O7 nanoparticles onto the surface of ZnIn2S4 nanosheet layers, the photocatalytic activity and selectivity of toluene oxidation were greatly enhanced. The rate of benzyl alcohol generated in 5 hours reached only 48 μmol g -1 h -1 , and the rate of benzaldehyde generated was 2362 μmol g -1 h -1 , with a selectivity of 98%. The enhancement of photocatalytic activity is attributed to the construction of an 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 4is a schematic diagram of photocatalytic activity of toluene oxidation of ZnIn2S4 nanosheet layer surface loaded with different contents of Bi-Bi2Sn2O7 nanoparticles. As can be seen from the figure, with the gradual increase of Bi-Bi2Sn2O7 content, the photocatalytic activity of toluene oxidation presents a volcano trend of first increasing and then decreasing, which may be that the appropriate Bi-Bi2Sn2O7 helps to promote the separation and rapid transfer of photo-generated charges, while excessive Bi-Bi2Sn2O7 may become the center of electron recombination, leading to the rapid recombination of electron-hole pairs, resulting in the decrease of photocatalytic activity of toluene oxidation.

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

[0073] Although the above embodiment describes the present application in detail, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. Application of Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalyst in the catalytic production of benzaldehyde from toluene; The preparation method of the Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material includes the following steps: 1) Zinc acetate, water, indium chloride, and thioacetamide were mixed and subjected to a hydrothermal reaction. After drying, ZnIn2S4 nanomaterials were obtained. 2) Mix the ZnIn2S4 nanomaterial obtained in step 1) with water, bismuth nitrate, polyvinylpyrrolidone, and mannitol to obtain solution A; Sodium stannate and water are mixed to obtain solution B; The A solution and the B solution are mixed to obtain a suspension; 3) The suspension obtained in step 2) is reacted and dried to obtain Bi-Bi2Sn2O7 / ZnIn2S4 composite photocatalytic material; In step 1), the molar ratio of zinc acetate, water, indium chloride, and thioacetamide is 0.4 mmol: 30 mL: 0.8 mmol: 1.6 mmol. The conditions for the hydrothermal reaction in step 1) include: heating to 180°C at a heating rate of 5°C / min and holding at that temperature for 24 hours; In step 2), the mass ratio of ZnIn2S4 nanomaterial to water volume, bismuth nitrate molar, polyvinylpyrrolidone molar, and mannitol molar is 0.2–0.5 g: 20 mL: 1 mmol: 0.2 mmol: 1.5 mmol. The mass ratio of the ZnIn2S4 nanomaterial to the volume of water, the molar amount of bismuth nitrate, the molar amount of polyvinylpyrrolidone, and the molar amount of mannitol is 0.3–0.4 g: 20 mL: 1 mmol: 0.2 mmol: 1.5 mmol. In step 2), the molar ratio of sodium stannate to water is 1 mmol: 10 mL. The reaction conditions in step 3) include: heating to 160°C at a heating rate of 5°C / min and holding at that temperature for 12 hours; The drying conditions for both steps 1) and 3) include: a temperature of 80°C and a time of 12 hours.

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