A Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material and its preparation method and application

Abstract

The present invention relates to the technical field of photocatalytic H2O2 production, and in particular to a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material and its preparation method and application. Melamine, cyanuric acid and water are mixed, and then dried and calcined in sequence to obtain a g-C3N4 photocatalytic material; the g-C3N4 photocatalytic material is dispersed in water to obtain a photocatalytic material solution; bismuth nitrate, polyvinyl pyrrolidone and D-mannitol solution are mixed to obtain a bismuth nitrate-containing solution; the photocatalytic material solution, the bismuth nitrate-containing solution and the potassium selenate solution are mixed, subjected to a hydrothermal reaction, and dried to obtain a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material. The preparation process of the present invention is simple, easy to control and has low production cost. The obtained Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material has the characteristics of high activity, good selectivity and excellent cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic H2O2 production, and in particular to a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is an important and widely used environmentally friendly and harmless oxidant. Its oxidation reaction produces only water as a byproduct. It is also an ideal energy storage material, boasting a high energy density and being easier to store and transport than hydrogen. As a chemical product, H2O2 is widely used in fields such as organic synthesis and environmental protection, playing a crucial role in chemical production. Current industrial methods for producing H2O2 include the anthraquinone (AQ) method or by directly mixing H2 with O2. However, the former requires high temperature and pressure, resulting in high energy consumption and the generation of polluting waste, while the latter carries a significant explosion hazard and requires the use of precious metals as co-catalysts. In contrast, photosynthetic H2O2 involves the oxidation and reduction of water and oxygen to H2O2 using photocatalysts under sunlight. Solar energy is inexhaustible, and the photocatalytic process produces virtually no waste. Therefore, photosynthetic H2O2 is considered a highly promising green route for H2O2 synthesis. At present, the research on photosynthetic H2O2 system is still in its preliminary stage, and the development of new, efficient, stable and inexpensive photocatalysts is the research focus of scientists.

[0003] Polymeric carbon nitride (PCN) is a two-dimensional, graphite-like layered material composed primarily of carbon and nitrogen. Its unique electronic and optical properties, excellent chemical stability, easily tunable structure, and non-toxicity and low cost have made it a research hotspot in the field of photocatalysis. In recent years, the use of PCN for photosynthesis of H₂O₂ has attracted widespread attention worldwide. However, the narrow spectral response range of PCN, the easy recombination of photogenerated charges, poor electron conductivity, and the low specific surface area caused by aggregation and adhesion during the synthesis process have severely restricted the widespread application of PCN photocatalysts. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, its preparation method and application. The preparation process of the present invention is simple, easy to control and has low production cost. The prepared Bi-Bi2Sn2O7 / g-C3N4 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 present invention provides a method for preparing a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, comprising the following steps:

[0007] 1) mixing melamine, cyanuric acid and water, and then drying and calcining in sequence to obtain a g-C3N4 photocatalytic material;

[0008] 2) dispersing the g-C3N4 photocatalytic material obtained in step 1) in water to obtain a photocatalytic material solution;

[0009] mixing bismuth nitrate, polyvinyl pyrrolidone and D-mannitol solution to obtain a bismuth nitrate-containing solution;

[0010] 3) The photocatalytic material solution obtained in step 2), the bismuth nitrate solution and the potassium selenate solution are mixed, the pH value is adjusted to 10.0-12.0, and then a hydrothermal reaction is carried out. After drying, a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material is obtained.

[0011] Preferably, in step 1), the mass ratio of melamine, cyanuric acid and water is 1:1:40.

[0012] Preferably, the drying conditions in step 1) include: a temperature of 60° C. and a drying time of 12 h;

[0013] The calcination conditions include: heating to 500-600° C. at a heating rate of 5-10° C. / min and keeping the temperature for 1-3 hours.

[0014] Preferably, in step 2), the mass ratio of the g-C3N4 photocatalytic material to water is 1 to 3:20.

[0015] Preferably, in step 2), the volume ratio of the mass of bismuth nitrate, the mass of polyvinyl pyrrolidone and the D-mannitol solution is 0.48 g:0.4 g:30 mL;

[0016] The concentration of the D-mannitol solution is 0.5 mol / L.

[0017] Preferably, in step 3), the volume ratio of the photocatalytic material solution, the bismuth nitrate-containing solution, and the potassium selenate solution is 4:6:1;

[0018] The concentration of the potassium selenate solution is 0.06 g / mL.

[0019] Preferably, the conditions of the hydrothermal reaction in step 3) include: temperature of 160-200° C. and time of 12-24 h;

[0020] The drying temperature is 80°C.

[0021] The present invention provides a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared by the preparation method described in the above technical solution.

[0022] The present invention also provides the use of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material described in the above technical solution in photocatalytic production of H2O2.

[0023] Preferably, the application includes: photocatalytic production of H2O2 under visible light or sunlight.

[0024] Beneficial effects of the present invention:

[0025] (1) The present invention disperses melamine and cyanuric acid in a mixed solution of water and ethanol, stirs and mixes them evenly, calcines and anneals them in a closed tube furnace after drying, and cools them naturally to obtain thinner g-C3N4 sheets as a carrier. Subsequently, g-C3N4 is dispersed in deionized water, bismuth nitrate, PVP and mannitol are added as solution A, and potassium selenate is dissolved in deionized water as solution B. Solution B is then slowly added dropwise to solution A while stirring continuously, mixing evenly, and adjusting the pH of the solution with KOH. Finally, the solution is transferred to a polytetrafluoroethylene autoclave for hydrothermal heating, and then cooled to room temperature to obtain a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material. The method of the present invention has a simple process, short preparation time, low energy consumption, and the prepared Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material has a rich pore structure and a large specific surface area.

[0026] (2) The photocatalytic performance of the Bi-Bi2Sn2O7 / g-C3N4 composite material prepared by the present invention was evaluated by photocatalytic H2O2 production in an oxygen atmosphere. The test results showed that under visible light irradiation, the Bi-Bi2Sn2O7 / g-C3N4 composite material produced a cumulative H2O2 of 780.5 μmol L-1 within 5 hours. -1 , with an average rate of 156.1 μmol L -1 h -1 Under simulated sunlight, the Bi-Bi2Sn2O7 / g-C3N4 composite material produced a cumulative H2O2 of 955.5 μmol L-1 within 5 hours. -1 , with an average rate of 191.1 μmol L -1 h -1 The photocatalytic activity of Bi-Bi2Sn2O7 / g-C3N4 was enhanced by 8.5 times and 7.5 times under visible light and simulated sunlight, respectively, compared to pure g-C3N4. In addition, Bi-Bi2Sn2O7 / g-C3N4 maintained high photocatalytic activity after multiple cycles.

[0027] (3) The Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared by the present invention can effectively enhance the activity and cyclic stability of photocatalytic H2O2 production, and has broad development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0029] Figure 1 is an X-ray diffraction (XRD) pattern of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared in Example 1 of the present invention;

[0030] Figure 2 is a scanning electron microscope (SEM) image of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared in Example 2 of the present invention;

[0031] Figure 3 Schematic diagram of the activity of Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4 (X=1, 2, 3) composite photocatalytic materials for producing H2O2 prepared in Example 1 of the present invention;

[0032] Figure 4 Schematic diagram of the activity of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material in producing H2O2 under different external conditions prepared in Example 2 of the present invention;

[0033] Figure 5 Schematic diagram of the H2O2 production activity of Bi-Bi2Sn2O7 prepared in Example 2 of the present invention under different external conditions;

[0034] Figure 6 Schematic diagram of the activity of g-C3N4 in producing H2O2 under different external conditions prepared in Example 2 of the present invention;

[0035] Figure 7 Schematic diagram of the cyclic stability of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material producing H2O2 under light irradiation prepared in Example 2 of the present invention;

[0036] Figure 8 Schematic diagram of the cyclic stability of g-C3N4 producing H2O2 under light irradiation prepared in Example 2 of the present invention;

[0037] Figure 9 This is a schematic diagram of the cyclic stability of the Bi-Bi2Sn2O7 material prepared in Example 2 of the present invention in producing H2O2 under light. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, comprising the following steps:

[0039] 1) mixing melamine, cyanuric acid and water, and then drying and calcining in sequence to obtain a g-C3N4 photocatalytic material;

[0040] 2) dispersing the g-C3N4 photocatalytic material obtained in step 1) in water to obtain a photocatalytic material solution;

[0041] mixing bismuth nitrate, polyvinyl pyrrolidone and D-mannitol solution to obtain a bismuth nitrate-containing solution;

[0042] 3) The photocatalytic material solution obtained in step 2), the bismuth nitrate solution and the potassium selenate solution are mixed, the pH value is adjusted to 10.0-12.0, and then a hydrothermal reaction is carried out. After drying, a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material is obtained.

[0043] The present invention comprises mixing melamine, cyanuric acid, and water, followed by drying and calcining to obtain a g-C3N4 photocatalytic material. In the present invention, the mass ratio of melamine, cyanuric acid, and water is preferably 1:1:40. In the present invention, the drying conditions preferably include: a temperature of 60°C for 12 hours. In the present invention, the calcining conditions preferably include: heating to 500-600°C at a rate of 5-10°C / min and maintaining the temperature for 1-3 hours.

[0044] The present invention disperses the obtained g-C3N4 photocatalytic material in water to obtain a photocatalytic material solution; and mixes bismuth nitrate, polyvinyl pyrrolidone, and D-mannitol solution to obtain a bismuth nitrate-containing solution. In the present invention, the mass ratio of the g-C3N4 photocatalytic material to water is preferably 1 to 3:20. In the present invention, the volume ratio of the mass of the bismuth nitrate, the mass of the polyvinyl pyrrolidone, and the D-mannitol solution is preferably 0.48g:0.4g:30mL. In the present invention, the concentration of the D-mannitol solution is preferably 0.5mol / L.

[0045] The present invention mixes the obtained photocatalytic material solution, bismuth nitrate-containing solution and potassium selenate solution, adjusts the pH value to 10.0-12.0, performs a hydrothermal reaction, and obtains a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material after drying. In the present invention, the volume ratio of the photocatalytic material solution, the bismuth nitrate-containing solution and the potassium selenate solution is preferably 4:6:1. In the present invention, the concentration of the potassium selenate solution is preferably 0.06 g / mL. In the present invention, the conditions of the hydrothermal reaction preferably include: a temperature of 160-200°C and a time of 12-24h. In the present invention, the drying temperature is preferably 80°C.

[0046] The present invention provides a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared by the preparation method described in the above technical solution.

[0047] The present invention also provides the use of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material described in the above technical solution in photocatalytic production of H2O2. In the present invention, the use preferably includes: photocatalytic production of H2O2 under visible light or sunlight.

[0048] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] A method for preparing a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, comprising the following steps:

[0051] S1. Disperse 5.0 g of melamine and 5.0 g of cyanuric acid into 200 ml of deionized water and stir to mix well.

[0052] S2. Transfer the thoroughly mixed melamine and cyanuric acid solution to a vacuum drying oven, maintain it at 60°C for 12 hours, and then cool it to room temperature after drying; then transfer the obtained melamine and cyanuric acid composite precursor to a closed tubular furnace, heat it to 550°C at a heating rate of 5°C / min, and maintain it for 2 hours; cool it naturally to obtain a g-C3N4 photocatalytic material with a thinner nanosheet layer.

[0053] S3. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml autoclave and maintain it at 180°C for 24 hours. After the reaction is completed, cool naturally to room temperature, centrifuge and wash, and dry the mixture at 80°C to obtain the Bi-Bi2Sn2O7 photocatalytic material, designated B-BSO.

[0054] S4. Disperse 1g of g-C3N4 nanosheets in 20ml of deionized water. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml high-pressure reactor and maintain it at 180°C for 24h. After the reaction is completed, cool naturally to room temperature, wash by centrifugation, and dry the mixture at 80°C to obtain a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, designated B-BSO / g-CN-1.

[0055] Example 2

[0056] A method for preparing a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, comprising the following steps:

[0057] S1. Disperse 5.0 g of melamine and 5.0 g of cyanuric acid into 200 ml of deionized water and stir to mix well.

[0058] S2. Transfer the thoroughly mixed melamine and cyanuric acid solution to a vacuum drying oven, maintain it at 60°C for 12 hours, and then cool it to room temperature after drying; then transfer the obtained melamine and cyanuric acid composite precursor to a closed tubular furnace, heat it to 550°C at a heating rate of 5°C / min, and maintain it for 2 hours; cool it naturally to obtain a g-C3N4 photocatalytic material with a thinner nanosheet layer.

[0059] S3. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml autoclave and maintain it at 180°C for 24 hours. After the reaction is completed, cool naturally to room temperature, centrifuge and wash, and dry the mixture at 80°C to obtain the Bi-Bi2Sn2O7 photocatalytic material, designated B-BSO.

[0060] S4. Disperse 2g of g-C3N4 nanosheets in 20ml of deionized water. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml high-pressure reactor and maintain it at 180°C for 24h. After the reaction is completed, cool naturally to room temperature, wash by centrifugation, and dry the mixture at 80°C to obtain a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, designated B-BSO / g-CN-2.

[0061] Example 3

[0062] A method for preparing a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, comprising the following steps:

[0063] S1. Disperse 5.0 g of melamine and 5.0 g of cyanuric acid into 200 ml of deionized water and stir to mix well.

[0064] S2. Transfer the thoroughly mixed melamine and cyanuric acid solution to a vacuum drying oven, maintain it at 60°C for 12 hours, and then cool it to room temperature after drying; then transfer the obtained melamine and cyanuric acid composite precursor to a closed tubular furnace, heat it to 550°C at a heating rate of 5°C / min, and maintain it for 2 hours; cool it naturally to obtain a g-C3N4 photocatalytic material with a thinner nanosheet layer.

[0065] S4. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml high-pressure reactor and maintain it at 180°C for 24 hours. After the reaction is completed, cool naturally to room temperature, wash by centrifugation, and dry the mixture at 80°C to obtain the Bi-Bi2Sn2O7 photocatalytic material, designated B-BSO.

[0066] S4. Disperse 3g of g-C3N4 nanosheets in 20ml of deionized water. Add 0.48g of Bi(NO3)3-5H2O and 0.4g of PVP to 30ml of 0.5M D-mannitol solution, referred to as Solution A. Subsequently, dissolve 0.3g of K2SnO3-3H2O in 5ml of deionized water to obtain Solution B. Slowly add Solution B dropwise to Solution A, stirring ultrasonically to mix thoroughly. Adjust the pH to 10.0 with 2M KOH solution. Finally, transfer the mixed solution to a 100ml high-pressure reactor and maintain it at 180°C for 24h. After the reaction is completed, cool naturally to room temperature, wash by centrifugation, and dry the mixture at 80°C to obtain a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material, designated B-BSO / g-CN-3.

[0067] Performance testing:

[0068] 1. The phase structure of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared in Examples 1-3 was analyzed using an XRD instrument.

[0069] Figure 1 The XRD spectra of Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic materials prepared in Examples 1-3 are used to characterize the crystal structures of different materials. Figure 1 As shown in the figure, the characteristic peaks at 13.2° and 27.2° are attributed to the (110) and (002) crystal planes of graphitic carbon nitride, while the characteristic peaks at 28.2° and 48.8° correspond to the (222) and (440) crystal planes of BSO, respectively, which are consistent with the standard card of BSO (JCPDSNO:87-0284). In addition, the peaks at 22.5°, 27.2°, 38.0°, 39.6°, 44.5°, 45.9°, 56.1°, 59.4°, 62.1°, 64.7°, 70.6°, and 71.9° belong to the (003), (012), (104), (110), (015), (006), (024), (107), (116), (122), (214), and (300) crystal planes of Bi, which are consistent with the standard chart of Bi (JCPDS NO: 44-1246). It is worth noting that in the Bi-Bi2Sn2O7 / g-C3N4 composite material, some characteristic peaks of Bi, Bi2Sn2O7, and g-C3N4 appear simultaneously, indicating that it is a composite composed of Bi, Bi2Sn2O7, and g-C3N4.

[0070] 2. The microstructure of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared in Example 1 was analyzed using SEM.

[0071] Figure 2 The SEM images of Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic materials prepared in Example 1 are shown in FIG. Figure 2 Middle (A) and Figure 2 (B) shows SEM images of different monomers, Bi-Bi2Sn2O7 and g-C3N4. It can be seen that B-BSO has nanoparticles of varying sizes, with a particle size of approximately 10 nm and an aggregated state. Pure g-C3N4 exhibits a relatively thin nanosheet structure with numerous wrinkles at the edges and numerous macropores. The presence of pores provides more active sites and optimal loading locations. When the Bi-Bi2Sn2O7 / g-C3N4 composite material is formed, g-C3N4 still exhibits a nanosheet structure with wrinkles at the edges and numerous macropores and pores on the sheet surface. In addition, the surface of the nanosheet is loaded with Bi-Bi2Sn2O7 nanoparticles with particle sizes ranging from 30 nm to 200 nm. Compared to pure Bi-Bi2Sn2O7, this may have caused aggregation and agglomeration. This heterojunction constructed between OD / 2D can effectively shorten the charge transfer distance. The thinner sheets and pore structures can enhance the absorption and utilization of light and accelerate the transfer of charges, ultimately enhancing the activity of photocatalytic H2O2 production.

[0072] 3. The photocatalytic H2O2 production performance of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material prepared in Examples 1-3 was analyzed with the help of a liquid ultraviolet spectrometer (UV-1800PC).

[0073] Figure 3The photocatalytic H2O2 production performance of Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4-X (X=1, 2, 3) nanomaterials prepared in Example 1 was evaluated. Specifically, the activity of the prepared photocatalysts in producing H2O2 was evaluated by 30 minutes of O2 exposure using saturated deionized water at normal pressure and room temperature under visible light and simulated solar radiation conditions. The specific experimental conditions are that the photocatalytic reaction is carried out in a gas-sealed system and the reactor is made of quartz. The photocatalytic instrument used is the Labsolar-6a all-glass automatic online trace gas analysis system of Beijing Perfect Light Technology Co., Ltd. The light source is a 300W xenon lamp, using a filter with a wavelength of (420nm<λ<780nm) and an AnalogueSunlight AM1.5G filter. In a typical experiment, 0.1 g of Bi-Bi2Sn2O7 / g-C3N4-2 was added to a photoreactor, followed by 10 mL of C2H5OH and 190 mL of deionized water. The mixture was then ultrasonically stirred for 10 minutes to ensure uniform mixing. Oxygen was then bubbled through the suspension for 30 minutes. After evacuating the gas-tight system, the suspension was irradiated. Furthermore, the rate of H2O2 evolution was measured after 5 hours of irradiation under different monochromatic light sources. The catalyst was separated by centrifugal filtration, and 2 mL of 100 mM potassium iodide and 25 μL of 20 mM ammonium molybdate were added to 20 mL of the supernatant. The mixture was stirred for 5 minutes, and the iodine absorbance at 352 nm was measured using UV-visible spectroscopy. The pure Bi-Bi2Sn2O7 sample produced negligible H2O2 after 5 hours of simulated sunlight / visible light irradiation. In addition, under simulated sunlight and visible light irradiation, the total amount of H2O2 produced by the pure g-C3N4 photocatalyst within 5 h was 127.0 μmol L -1 and 91.5 μmol L -1 , with an average rate of 25.4 μmol L -1 h -1 and 18.3 μmol L -1 h -1 , showing lower activity, which is attributed to the easy recombination of carriers generated by photoexcitation of pure g-C3N4. When the Bi-Bi2Sn2O7 / g-C3N4-X composite material is formed, the photocatalytic activity shows a volcanic trend, and the activity of Bi-Bi2Sn2O7 / g-C3N4-2 reaches the best. Under visible light and simulated sunlight irradiation, the total amount of H2O2 produced by Bi-Bi2Sn2O7 / g-C3N4-2 photocatalyst within 5 hours is 955.5μmol L -1 and 780.5 μmol L -1 , with an average rate of 191.1 μmol L -1 h -1and 156.1 μmol L -1 h -1 , which are 7.5 and 8.5 times that of pure g-C3N4, respectively, showing excellent photocatalytic H2O2 production activity.

[0074] like Figures 4-6 As shown in the figure, in order to study the effects of various atmospheres on the photocatalytic production of H2O2, experiments on the photocatalytic production of H2O2 by Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4 were carried out under saturated O2, N2 and air conditions, respectively. Under simulated sunlight conditions, the photocatalytic activities of Bi-Bi2Sn2O7, g-C3N4 and Bi-Bi2Sn2O7 / g-C3N4 all exceeded the photocatalytic activity observed under visible light conditions, which may be due to the presence of higher energy ultraviolet rays in simulated sunlight. In addition, in a pure O2 atmosphere, the photocatalytic yield of H2O2 of the three photocatalysts was the highest, indicating that O2 is one of the necessary conditions for the efficient production of H2O2. It is worth noting that O2 in the aqueous solution and the reactor plays a key role in the photocatalytic reaction of H2O2. Specifically, under an air atmosphere, the photocatalytic activity of Bi-Bi2Sn2O7 / g-C3N4 was reduced to 46.8 μmol L -1 h -1 and 31.5 μmol L -1 h -1 This finding indicates that Bi-Bi2Sn2O7 / g-C3N4-2 is able to oxidize oxygen in water and then produce H2O2 through a series of reactions. However, in a N2 atmosphere, the photocatalytic activity of H2O2 production was greatly reduced, with a rate of only 8.2 μmol L -1 h -1 and 5.6 μmol L -1 h -1 This is because there is only a small amount of O2 in the solution. After it is consumed, it is difficult to react further. In the air atmosphere, the photocatalytic activity of pure g-C3N4 is reduced to 8.9μmol L -1 h -1 and 6.4 μmol L -1 h -1 This finding suggests that g-C3N4 can also oxidize oxygen in water and then produce H2O2 through a series of reactions. However, in a N2 atmosphere, the photocatalytic activity of g-C3N4 in producing H2O2 was greatly reduced, with a rate of only 1.8 μmol L -1 h -1 and 1.32 μmol L -1 h -1In addition, for pure Bi-Bi2Sn2O7, the photocatalytic activity of Bi-Bi2Sn2O7 decreased to 8.3 μmol L -1 h -1 and 5.7 μmol L -1 h -1 This finding indicates that Bi-Bi2Sn2O7 can also oxidize oxygen in water and then produce H2O2 through a series of reactions. However, in a N2 atmosphere, the photocatalytic activity of Bi-Bi2Sn2O7 in producing H2O2 is greatly reduced, with a rate of only 0.2 μmol L -1 h -1 and 0.1 μmol L -1 h -1 . The above results demonstrate that Bi-Bi2Sn2O7 / g-C3N4-2 has the best photocatalytic activity for H2O2 production, and is most active in oxygen. More importantly, cyclic stability experiments were conducted under visible light and simulated sunlight to evaluate the stability of Bi-Bi2Sn2O7, g-C3N4, and Bi-Bi2Sn2O7 / g-C3N4 in the photocatalytic production of H2O2. Under simulated sunlight, the average rate of photocatalytic H2O2 production by Bi-Bi2Sn2O7 / g-C3N4-2 reached 191.1 μmol L in the first cycle. -1 h -1 After five cycles, it stabilized at 175.2 μmol L -1 h -1 , which is 91.7% of the initial cycle yield. In addition, under visible light irradiation, the average rate of photocatalytic H2O2 production of Bi-Bi2Sn2O7 / g-C3N4-2 in the first cycle was 156.1 μmol L - 1 h -1 , which remained at 143.8 μmol L after five cycles. -1 h -1 The average rate of photocatalytic H2O2 production by pure g-C3N4 under simulated sunlight reached 46.6 μmol L in the first cycle. -1 h -1 After five cycles, it stabilized at 42.3 μmol L -1 h -1 , which is 90.8% of the initial cycle yield. Under visible light irradiation, the average rate of photocatalytic H2O2 production in the first cycle was 31.5 μmol L -1 h -1 , which remained at 27.2 μmol L after five cycles. -1 h -1The rate of photocatalytic H2O2 production in the first cycle is 86.3% of the first cycle performance. For pure Bi-Bi2Sn2O7, the average rate of photocatalytic H2O2 production in the first cycle under simulated sunlight is 8.3 μmol L -1 h -1 , which remained at 4.1 μmol L after five cycles. -1 h -1 The average photocatalytic rate of H2O2 production in the first cycle under visible light irradiation was 5.6 μmol L -1 h -1 , which remained at 2.4 μmol L after five cycles. -1 h -1 The rate is 42.8% of the first cycle performance. Therefore, according to the above analysis, Bi-Bi2Sn2O7 / g-C3N4-2 not only has a high photocatalytic H2O2 production activity, but also shows excellent cycle durability, so it is expected to become one of the candidate photocatalysts for the generation of H2O2, such as Figures 7-9 shown.

[0075] Although the above embodiment provides a detailed description of the present invention, 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 scope of protection of the present invention.

Claims

1. Application of Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic materials in photocatalytic H2O2 production; The preparation method of the Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material comprises the following steps: 1) Melamine, cyanuric acid and water are mixed, and then dried and calcined in sequence to obtain g-C3N4 photocatalytic material; 2) dispersing the g-C3N4 photocatalytic material obtained in step 1) in water to obtain a photocatalytic material solution; mixing bismuth nitrate, polyvinyl pyrrolidone and D-mannitol solution to obtain a bismuth nitrate-containing solution; 3) The photocatalytic material solution obtained in step 2), the bismuth nitrate solution and the potassium selenate solution are mixed, the pH value is adjusted to 10.0-12.0, and then a hydrothermal reaction is carried out. After drying, a Bi-Bi2Sn2O7 / g-C3N4 composite photocatalytic material is obtained.

2. The use according to claim 1, characterized in that In the step 1), the mass ratio of melamine, cyanuric acid and water is 1:1:

40.

3. The use according to claim 1, characterized in that The drying conditions in step 1) include: a temperature of 60° C. and a drying time of 12 hours; The calcination conditions include: heating to 500-600° C. at a heating rate of 5-10° C. / min and keeping the temperature for 1-3 hours.

4. The use according to claim 1, characterized in that In the step 2), the mass ratio of the g-C3N4 photocatalytic material to water is 1-3:

20.

5. The use according to claim 1, characterized in that In step 2), the volume ratio of bismuth nitrate, polyvinyl pyrrolidone, and D-mannitol solution is 0.48 g:0.4 g:30 mL; The concentration of the D-mannitol solution is 0.5 mol / L.

6. The use according to claim 1, characterized in that In step 3), the volume ratio of the photocatalytic material solution, the bismuth nitrate solution and the potassium selenate solution is 4:6:1; The concentration of the potassium selenate solution is 0.06 g / mL.

7. The use according to claim 1, characterized in that The conditions of the hydrothermal reaction in step 3) include: temperature of 160-200° C. and time of 12-24 hours; The drying temperature is 80°C.

8. The use according to claim 1, characterized in that The application includes: photocatalytic production of H2O2 under visible light or sunlight.

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