Preparation method of hexagonal bismuth phosphate modified indium zinc sulfide composite catalyst and application of photocatalytic synthesis of hydrogen peroxide

Abstract

The invention discloses a hexagonal bismuth phosphate modified indium zinc sulfide (ZIS / HBIP) composite catalyst and a preparation method thereof. The catalyst is applied to photocatalytic synthesis of HO. The indium zinc sulfide (ZIS) nano flower balls in the catalyst are prepared by a hydrothermal method, and then hexagonal bismuth phosphate (HBIP) is loaded on the surface of the ZIS by a room temperature precipitation method to obtain a series of ZIS / HBIP composite catalysts. ZIS and HBIP can effectively improve photo-induced electron-hole separation and transmission, improve the selectivity of direct two-electron oxygen reduction reaction (2eORR) and inhibit HO decomposition. Experimental results show that when the theoretical dosage of HBIP is 0.01 mmol, the prepared ZIS / HBIP 0.01 has the optimal photocatalytic activity, the HO yield within 1 h can reach about 955 [mu] mol.g.h, and efficient synthesis of HO in pure water is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and specifically to a photocatalyst for modifying zinc indium sulfide (ZIS) with bismuth hexaphosphate (HBIP), its preparation method and application, mainly for highly efficient photocatalytic synthesis of hydrogen peroxide (H2O2). Background Art

[0002] As an efficient and environmentally friendly oxidant, H2O2 has a wide range of applications in the fields of chemical industry, environmental protection and medicine. However, the traditional methods for synthesizing H2O2 have problems such as high energy consumption and environmental pollution. In recent years, photocatalytic synthesis of H2O2 has attracted extensive attention due to its green and low energy consumption characteristics. Nevertheless, the current photocatalytic synthesis of H2O2 technology still faces some challenges, such as insufficient absorption of visible light by photocatalytic materials, rapid recombination of photo-generated electron-hole pairs, and poor selectivity in the generation of H2O2, etc.

[0003] Zinc indium sulfide (ZIS) is a semiconductor material with good photocatalytic performance, especially responsive to visible light, but its photocatalytic efficiency is limited by the rapid recombination of photo-generated electrons and holes, and the synthesized H2O2 is easily decomposed. In order to improve the efficiency of its photocatalytic synthesis of H2O2, researchers have tried to modify ZIS by various methods, including doping, compounding and other methods.

[0004] Bismuth phosphate (BiPO4) is an excellent ultraviolet-visible light responsive photocatalyst. Combining it with ZIS to form a heterojunction structure can effectively improve the photocatalytic performance of ZIS, inhibit the decomposition of H2O2, and improve the synthesis efficiency. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a bismuth hexaphosphate modified zinc indium sulfide composite catalyst and its preparation method, and is applied to photocatalytic synthesis of H2O2. This method loads bismuth hexaphosphate on the surface of zinc indium sulfide through a simple room temperature precipitation method, effectively improving the visible light absorption ability of the photocatalyst, the separation efficiency of photo-generated electron-hole pairs, as well as the selectivity and stability of the synthesized H2O2.

[0006] The technical solution of the present invention is as follows: The ZIS / HBIP composite catalyst is prepared by loading bismuth hexaphosphate (HBIP) on the surface of ZnIn2S4 nanoflower spheres (ZIS), improving the selectivity of the direct two-electron oxygen reduction reaction (2e − ORR), while inhibiting the decomposition of the product H2O2, thereby realizing the efficient photocatalytic synthesis of H2O2 in pure water.

[0007] According to the present invention, the preparation method of the above-mentioned bismuth phosphate-modified zinc indium sulfide photocatalyst comprises the following steps: (1) Dissolve Zn(Ac)2·2H2O and InCl3·4H2O in deionized water, and then add CH3CSNH2 (TAA) and stir evenly; (2) Transfer the solution obtained in step (1) to a polytetrafluoroethylene high-pressure hydrothermal reactor for hydrothermal reaction. After the reaction is completed and cooled to room temperature, take out the solution from the hydrothermal reactor; (3) Centrifuge the solution obtained in step (2) to remove the supernatant, wash it 3 times with deionized water / ethanol respectively, and then dry it overnight. Grind the dried solid into powder, and finally collect the obtained yellow powder as ZnIn2S4 nanoflower spheres (ZIS); (4) Ultrasonically disperse the ZIS obtained in step (3) in 30 mL of deionized water to make ZIS evenly dispersed in water; (5) Add Bi(NO3)3·5H2O and Na3PO4·12H2O to the ZIS dispersion obtained in step (4) in sequence, and stir slowly; (6) Wash the solution obtained in step (5) 3 times with deionized water / ethanol respectively, and then dry it overnight at 80 °C. Grind the dried solid into powder, and finally collect the obtained powder as ZIS / HBIP; (7) By controlling the addition of different amounts of Bi(NO3)3·5H2O and Na3PO4·12H2O, a series of ZIS / HBIP x composite catalysts are prepared.

[0008] According to the present invention, a preferred embodiment of the preparation method of the above-mentioned ZIS / HBIP composite photocatalyst comprises the following steps: Dissolve 1 mmol of Zn(Ac)2·2H2O and 2 mmol of InCl3·4H2O in 60 mL of deionized water, then add 6 mmol of CH3CSNH2 (TAA) and stir evenly. Then transfer the solution to a 100 mL polytetrafluoroethylene high-pressure hydrothermal reactor and perform hydrothermal treatment at 160 °C for 12 h. After the reaction is completed and cooled to room temperature, take out the solution from the hydrothermal reactor, centrifuge for 5 min to remove the supernatant, wash it 3 times with deionized water / ethanol respectively, and then dry it overnight at 80 °C. Grind the dried solid into powder, and finally collect the obtained yellow powder as ZIS.

[0009] Disperse 0.1 g of ZIS ultrasonically in 30 mL of deionized water to make ZIS uniformly dispersed in water. Then, add Bi(NO3)3·5H2O and Na3PO4·12H2O to the ZIS dispersion successively, and stir slowly at room temperature for 24 h to obtain the ZIS / HBIP series of materials. Wash the reacted solution three times with deionized water / ethanol each, and then dry it overnight at 80 °C. Grind the dried solid into powder, and finally collect the obtained powder as ZIS / HBIP. Fix the molar ratio of Bi(NO3)3·5H2O and Na3PO4·12H2O at 1:1, and add different contents of Bi(NO3)3·5H2O and Na3PO4·12H2O respectively to prepare the ZIS / HBIP x series of materials (x represents the amount of substance of Bi(NO3)3·5H2O and Na3PO4·12H2O added, namely 0.005 mmol, 0.01 mmol, 0.2 mmol, and 1 mmol). Name the products according to the amount of substance of Bi(NO3)3·5H2O and Na3PO4·12H2O added theoretically, and the corresponding products are named ZIS / HBIP 0.005 、ZIS / HBIP 0.01 、ZIS / HBIP 0.2 、ZIS / HBIP1.

[0010] According to the present invention, the above ZIS / HBIP composite photocatalyst is used for photocatalytic synthesis of H2O2.

[0011] According to the present invention, preferably, the application method is as follows: Under a 300 W xenon lamp equipped with a 420 nm cut-off filter, the photocatalytic synthesis performance of H2O2 of the catalyst was tested. Weigh 10 mg of the catalyst and put it into a photocatalytic tube, and then add 50 mL of deionized water. Stir in the dark for 30 min to establish the adsorption-desorption equilibrium, and at the same time, introduce oxygen into the system. Then turn on the xenon lamp and irradiate for 1 h. Take 1 mL of the solution every 15 min, and then filter it with a 0.45 μm filter to remove the powder sample. The iodine titration method was used to measure the concentration of H2O2 in the experiment. Take 0.5 mL of the filtrate, dilute it by 1 time, add 2 mL of 0.1 M KI solution and 0.05 mL of 0.01 M ammonium molybdate solution. Mix the solution well, and after color development for 10 min, measure the absorbance at 350 nm. Calculate the concentration of H2O2 according to the standard curve.

[0012] According to the above experimental application, ZIS / HBIP 0.01 shows the highest H2O2 yield.

[0013] The beneficial effects of the present invention: 1. Without a sacrificial agent, the novel photocatalytic material of the present invention enables efficient photocatalytic synthesis of H2O in pure water. 2； 2. By loading HBIP on ZIS, a novel photocatalyst ZIS / HBIP is constructed. Due to its unique confined adsorption effect, oxygen and water molecules can smoothly pass through the pores of HBIP on its surface and reach the surface of ZIS. Then, the photo-generated electrons directly react with the adsorbed oxygen through 2e − ORR to generate H2O 2； 3. Since the concentration of H2O2 near ZIS is higher than that in the solution, the product H2O2 passes through the hydrate cavity of the HBIP coating along the concentration gradient. Benefiting from the low affinity of ZIS / HBIP for H2O2, the product H2O2 quickly detaches from the material surface, avoiding decomposition by ZIS, thus achieving effective accumulation in aqueous solution. Description of the Drawings

[0014] Figure 1 Flower-like microspheres of zinc indium sulfide (ZnIn2S4, ZIS) obtained in Example 1.

[0015] Figure 2 Scanning electron microscope photograph of bismuth hexaphosphate modified ZnIn2S4 composite material (ZIS / HBIP).

[0016] Figure 3 Comparison of H2O2 yields of ZIS and ZIS / HBIP series samples obtained in Examples 1 and 2 in pure water (10 mg catalyst, 50 mL pure water, λ>420 nm). Detailed Embodiments

[0017] To better understand the present invention, the following is further illustrated by specific examples and drawings, but not limited thereto.

[0018] Example 1: Preparation of ZnIn2S4 Flower-like Microspheres The ZnIn2S4 flower-like microspheres (ZIS) were synthesized by a simple hydrothermal method. 1 mmol of Zn(Ac)2·2H2O and 2 mmol of InCl3·4H2O were dissolved in 60 mL of deionized water, and then 6 mmol of CH3CSNH2 (TAA) was added and stirred evenly. Then the solution was transferred to a 100 mL polytetrafluoroethylene high-pressure hydrothermal autoclave and hydrothermally treated at 160 °C for 12 h. After the reaction ended and cooled to room temperature, the solution was taken out from the hydrothermal autoclave, centrifuged for 5 min to remove the supernatant, washed 3 times with deionized water / ethanol respectively, and then dried overnight at 80 °C. The dried solid was ground into powder, and the finally collected yellow powder was ZIS.

[0019] Example 2: Preparation of Bismuth Hexaphosphate Modified ZnIn2S4 The ZIS / HBIP series of materials were prepared by depositing bismuth hexaphosphate (HBIP) on the surface of ZnIn2S4 flower-like microspheres through a room-temperature precipitation method. First, 0.1 g of ZIS was ultrasonically dispersed in 30 mL of deionized water to uniformly disperse ZIS in water. Then, Bi(NO3)3·5H2O and Na3PO4·12H2O were successively added to the ZIS dispersion, and the mixture was slowly stirred at room temperature for 24 h to obtain the ZIS / HBIP series of materials. The reaction solution was washed three times with deionized water / ethanol each, and then dried overnight at 80 °C. The dried solid was ground into a powder, and the finally collected powder was ZIS / HBIP. Fixing the molar ratio of Bi(NO3)3·5H2O and Na3PO4·12H2O at 1:1, different amounts of Bi(NO3)3·5H2O and Na3PO4·12H2O were added respectively to prepare the ZIS / HBIP x series of materials (x represents the amount of substance of Bi(NO3)3·5H2O and Na3PO4·12H2O added, i.e., 0.005 mmol, 0.01 mmol, 0.2 mmol, and 1 mmol). The products were named according to the theoretically added amount of substance of Bi(NO3)3·5H2O and Na3PO4·12H2O, and the corresponding products were named ZIS / HBIP 0.005 、ZIS / HBIP 0.01 、ZIS / HBIP 0.2 、ZIS / HBIP1. The scanning electron microscope photos of the indium zinc sulfide (ZnIn2S4, ZIS) flower-like microspheres and the bismuth hexaphosphate modified indium zinc sulfide photocatalyst obtained in this example are as Figure 1-2 shown. As can be seen from Figure 1-2 this, ZIS is a tightly packed nano-flower ball formed by the interweaving of two-dimensional nanosheets. After HIBP is deposited on the surface of ZIS, the material changes from the original flower-like microspheres to an irregular shape, and rod-like structures exist on the surface

[0020] Example 3: Photocatalytic Synthesis of H2O2 Experiment The photocatalytic H2O2 production performance of the catalyst was tested under a 300 W xenon lamp equipped with a 420 nm cut-off filter. Weighed 10 mg of the catalyst and put it into the photocatalytic tube, then added 50 mL of deionized water. Stirred for 30 min in the dark to establish the adsorption-desorption equilibrium, and at the same time, oxygen was introduced into the system. Then the xenon lamp was turned on for irradiation for 1 h. 1 mL of the solution was taken every 15 min and then filtered through a 0.45 μm filter to remove the powder sample. In this experiment, the iodine titration method was used to determine the H2O2 concentration. Dilute 0.5 mL of the filtrate by 1 time, add 2 mL of 0.1 M KI solution and 0.05 mL of 0.01 M ammonium molybdate solution. Mix the solution well, after color development for 10 min, measure the absorbance at 350 nm. Calculate the H2O2 concentration according to the standard curve. The photocatalytic synthesis performance of H2O2 of the ZIS and ZIS / HBIP series materials was tested under saturated oxygen conditions in pure water. As Figure 3 shown, compared with the ZIS / HBIP series materials, the photocatalytic activity of ZIS is very low, which is attributed to the easy recombination of photo-generated carriers in ZIS and the easy decomposition of the product H2O2. After loading HBIP on the surface of ZIS to form a heterojunction, the yield of H2O2 increased significantly. When the theoretical loading amount of HBIP is 0.01 mmol, the formed ZIS / HBIP 0.01 has the strongest H2O2 production activity, reaching about 191 μmol / L after 1 h. The deposition of an appropriate amount of HBIP on the surface of ZIS to form a heterojunction is beneficial to the separation and transfer of electrons and holes on the one hand, and to the accumulation of the product H2O2 on the other hand, thus significantly improving the production efficiency of H2O2. When the loading amount of HBIP is large, the excessive deposition of HBIP on the surface is not conducive to the contact between ZIS and oxygen, resulting in a decrease in the generation rate. However, it can be seen that the generation rate curve of ZIS / HBIP1 is closer to a straight line, confirming that HBIP effectively inhibits the decomposition of the product H2O2.

Claims

1. A catalyst for photocatalytic synthesis of hydrogen peroxide (H2O2) by bismuth hexaphosphate modified indium zinc sulfide (ZIS), characterized in that, The catalyst includes ZIS flower-like microspheres and bismuth hexaphosphate (HBIP) loaded on the surface of ZIS, and a composite structure is formed between ZIS and HBIP by the room-temperature precipitation method.

2. The catalyst according to claim 1, characterized in that, The molar ratio of ZIS to HBIP is 1:1, and the HBIP loading amount of the composite material ranges from 0.005 mmol to 1 mmol.

3. The catalyst according to claim 1, characterized in that, ZIS is synthesized by the hydrothermal method. The specific steps include dissolving Zn(Ac)2·2H2O and InCl3·4H2O in deionized water, adding thioacetamide (TAA) as a reaction precursor, and performing a hydrothermal reaction at 160 °C for 12 hours to obtain ZIS with a flower-like microsphere structure.

4. The catalyst according to claim 1, characterized in that, Bismuth hexaphosphate (HBIP) is loaded on the surface of ZIS by the room-temperature precipitation method. The steps include mixing the ZIS solution with Bi(NO3)3·5H2O and Na3PO4·12H2O solutions, and stirring at room temperature for 24 hours to obtain the ZIS / HBIP composite material.

5. The catalyst according to claim 1, characterized in that, The HBIP loaded on the surface of ZIS promotes the synthesis of H2O2 and effectively inhibits the decomposition of the generated H2O2.

6. The catalyst according to claim 1, wherein Under the illumination condition of λ > 420 nm, the photocatalytic synthesis efficiency of H2O2 of the catalyst is such that, compared with pure ZIS, the photocatalytic H2O2 yield of the ZIS / HBIP composite material is significantly improved.

7. The catalyst according to claim 6, characterized in that, The synthesis rate of H2O2 increases with the increase of the HBIP loading amount, and in the case of using sacrificial agents such as ethanol, methanol or isopropanol, the yield of H2O2 is further improved.

8. The catalyst according to claim 1, characterized in that, The photoelectrochemical performance and electron-hole separation efficiency of the catalyst are significantly improved by the HBIP loading, which can effectively promote the generation of H2O2.

9. The application of the ZIS / HBIP photocatalytic material according to any one of claims 1-4 for photocatalytic synthesis of H2O2.

10. The application according to claim 9, characterized in that, The application method is as follows: Add the catalyst to pure water, stir and perform a photocatalytic reaction under xenon lamp irradiation; Sample at regular intervals and use the iodometric method to measure the H2O2 concentration.

11. The method according to claim 9, characterized in that, The illumination wavelength of the photocatalytic reaction is λ > 420 nm, the reaction time is 1 hour, and the catalyst concentration is 0.2 g L -1 .

12. The method according to claim 9, wherein The catalyst has excellent cyclic use stability and can still maintain a high H2O2 yield after multiple reactions.

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