A fluorine-doped ZnIn2S4 photocatalyst, its preparation method and application

Abstract

This invention provides a fluorine-doped ZnIn2S4 photocatalyst, its preparation method, and its application. The fluorine-doped ZnIn2S4 photocatalyst has a spherical nanoflower structure, which is composed of nanosheets arranged in an array. The preparation method includes the following steps: (1) adding ZnCl2, InCl3·4H2O, and thioacetamide to water and stirring to obtain a mixture A; (2) adding a fluorine source to mixture A and mixing thoroughly to obtain mixture B; (3) subjecting mixture B to a hydrothermal reaction, separating the product after the reaction, washing, and drying to obtain the F-ZnIn2S4 photocatalyst. The fluorine-doped ZnIn2S4 photocatalyst exhibits highly efficient photocatalytic activity.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic degradation, specifically to a fluorine-doped ZnIn2S4 photocatalyst (F-ZnIn2S4) for photocatalytic degradation of volatile organic pollutants (VOCs) in the air, its preparation method, and its application. Background Technology

[0002] Over the past few decades, rapid industrialization and urbanization have led to a dramatic increase in VOC emissions into the air. VOCs not only pose serious threats to human health but also contribute to environmental problems such as photochemical smog and ozone layer depletion. Therefore, developing efficient and environmentally friendly VOC degradation technologies is of great significance. In recent years, photocatalysis technology, due to its ability to degrade pollutants using solar energy at ambient temperature and pressure, has been considered one of the effective methods for solving the VOC pollution problem.

[0003] ZnIn2S4, a typical layered sulfide semiconductor material, shows great promise for application in photocatalysis due to its suitable bandgap structure, excellent light absorption performance, and good chemical stability. However, the high recombination rate of photogenerated carriers generated under photoexcitation conditions limits its photocatalytic performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide a fluorine-doped ZnIn2S4 photocatalyst, its preparation method and application, wherein the fluorine-doped ZnIn2S4 photocatalyst has high photocatalytic activity.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a fluorine-doped ZnIn2S4 photocatalyst, which has a morphology of a spherical nanoflower structure, wherein the spherical nanoflower structure is composed of an arrangement of nanosheets.

[0006] Preferably, the diameter of the spherical nanoflower structure is 4~10 μm.

[0007] Secondly, the present invention provides a method for preparing the fluorine-doped ZnIn2S4 photocatalyst, comprising the following steps: (1) Add ZnCl2, InCl3·4H2O and thioacetamide (TAA) to water and stir to obtain mixture A; (2) Add a fluoride source to mixture A and mix well to obtain mixture B; (3) The mixture B was subjected to a hydrothermal reaction. After the reaction was completed, the separation product was separated, washed and dried to obtain F-ZnIn2S4 photocatalyst.

[0008] Preferably, the fluorine source is ammonium fluoride (NH4F).

[0009] Furthermore, the ratio of fluorine source to ZnCl2 is (0.01~0.1) g: 1 mmol.

[0010] Preferably, the hydrothermal reaction temperature is 160~200 ℃ and the time is 10~14 h.

[0011] Preferably, the molar ratio of ZnCl2, InCl3·4H2O and TAA is 1:1:2.

[0012] Preferably, in step (1), the mixture is stirred at room temperature for 30 to 60 minutes.

[0013] Preferably, in step (3), the washing is performed by washing with deionized water and ethanol 3 to 5 times respectively.

[0014] Preferably, in step (3), the drying is performed under vacuum at 60~80 °C for 6~12 h.

[0015] Thirdly, the present invention provides the application of the fluorine-doped ZnIn2S4 photocatalyst in the photocatalytic degradation of VOCs.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention involves doping F in ZnIn2S4. - On the one hand, F - It has unique electronic modulation capabilities, F - The strong electronegativity of F reconfigures the electron cloud distribution of the ZnIn2S4 semiconductor by forming FS / FO bonds, and narrows the band gap by introducing impurity energy levels below the conduction band; on the other hand, F - Doping-induced sulfur / oxygen vacancies act as electron trapping centers, which is beneficial for carrier separation; furthermore, F - Induced surface reconstruction can expose more active sites. In summary, F - The introduction of [a specific ingredient] can modulate the band structure of ZnIn2S4, improve the separation efficiency of photogenerated carriers, and thus enhance its photocatalytic activity.

[0017] The method for preparing fluorine-doped ZnIn2S4 photocatalyst of this invention is achieved through a simple hydrothermal reaction and is easy to scale up for production.

[0018] Furthermore, the fluorine source used in this invention is ammonium fluoride. Choosing ammonium fluoride as the dopant for the ZnIn2S4 photocatalyst provides both nitrogen and fluorine dopants, compared to other fluorine sources (such as hydrofluoric acid HF and sodium fluoride NaF). The introduction of nitrogen helps to narrow the band gap of the catalyst and enhance its response to visible light; the introduction of fluorine creates oxygen vacancies and inhibits carrier recombination. The synergistic effect of both significantly improves the photocatalytic activity of the catalyst, resulting in superior photocatalytic performance compared to single fluorine doping (such as using hydrofluoric acid or sodium fluoride). In addition, the strong corrosiveness and high toxicity of hydrofluoric acid cause inconvenience and safety hazards in experimental operations; while sodium fluoride is more expensive than ammonium fluoride. Considering all these reasons, choosing ammonium fluoride as the dopant not only reduces cost but also yields a catalyst with superior catalytic performance.

[0019] Furthermore, by controlling the ratio of fluorine source to ZnCl2, the catalytic activity of fluorine-doped ZnIn2S4 photocatalyst can be adjusted. As the ratio of fluorine source to ZnCl2 increases, the catalytic activity of fluorine-doped ZnIn2S4 photocatalyst first increases and then decreases. When the ratio of fluorine source to ZnCl2 is (0.01~0.1) g:1 mmol, better catalytic activity can be obtained.

[0020] The fluorine-doped ZnIn2S4 photocatalyst of this invention can be used for the photocatalytic degradation of VOCs in the air. Catalytic results show that it can degrade 93.6% of formaldehyde within 3 hours, exhibiting excellent photocatalytic activity. Furthermore, after the reaction, the F-ZnIn2S4 photocatalyst exhibits good stability and reusability, reducing costs in practical applications. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 For comparative example 1, pure ZnIn2S4 and different F in Examples 1-5 - SEM images of F-ZnIn2S4 with doping ratios (1%~10%): (a1)~(a3) are ZnIn2S4; (b1)~(b3) are F-ZIS-1%; (c1)~(c3) are F-ZIS-3%; (d1)~(d3) are F-ZIS-5%; (e1)~(e3) are F-ZIS-7%; (f1)~(f3) are F-ZIS-10%.

[0023] Figure 2These are TEM images of F-ZIS-7% at different magnifications in Example 4.

[0024] Figure 3 For comparative example 1, pure ZnIn2S4 and different F in Examples 1-5 - XRD pattern of F-ZnIn2S4 with different doping ratios.

[0025] Figure 4 To compare the pure ZnIn2S4 in Comparative Example 1 with the different F in Examples 1-7 - Electrochemical test results of F-ZnIn2S4 with varying doping ratio: It curve.

[0026] Figure 5 To compare the pure ZnIn2S4 in Comparative Example 1 with the different F in Examples 1-7 - Conversion curve of formaldehyde degradation by photocatalysis using F-ZnIn2S4 with doping ratio. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0029] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0030] Comparative Example 1 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide (TAA), dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture. Transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally react at 180 °C for 12 h. After the reaction, allow it to cool to room temperature naturally, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product alternately with deionized water and ethanol 5 times. Place the washed product in a vacuum drying oven at 70 °C and dry for 8 h to obtain a light yellow powder ZnIn2S4 (ZIS).

[0031] Example 1 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.01 g ammonium fluoride (NH4F) to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 180 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product with deionized water and ethanol alternately 5 times. Place the washed product in a vacuum drying oven at 70 ℃ and dry for 8 h to obtain a light yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-1.

[0032] Example 2 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.03 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 180 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product with deionized water and ethanol alternately 5 times. Place the washed product in a vacuum drying oven at 70 ℃ and dry for 8 h to obtain a light yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-3.

[0033] Example 3 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.05 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 180 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product with deionized water and ethanol alternately 5 times. Place the washed product in a vacuum drying oven at 70 ℃ and dry for 8 h to obtain a light yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-5.

[0034] Example 4 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.07 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 180 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product with deionized water and ethanol alternately 5 times. Place the washed product in a vacuum drying oven at 70 ℃ and dry for 8 h to obtain a light yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-7.

[0035] Example 5 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.10 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 180 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product with deionized water and ethanol alternately 5 times. Place the washed product in a vacuum drying oven at 70 ℃ and dry for 8 h to obtain a light yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-10.

[0036] Example 6 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O, and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.07 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 160 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product alternately with deionized water and ethanol 5 times. Dry the washed product in a vacuum drying oven at 70 ℃ for 8 h to obtain a pale yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-7%. (160) .

[0037] Example 7 Weigh 1 mmol ZnCl2, 1 mmol InCl3·4H2O, and 2 mmol thioacetamide, dissolve them in 100 mL deionized water, and stir with a magnetic stirrer at room temperature for 30 min to obtain a homogeneous mixture A. Add 0.07 g ammonium fluoride to mixture A and stir for 30 min until completely dissolved to obtain mixture B. Transfer mixture B to a 100 mL polytetrafluoroethylene-lined reactor and perform a hydrothermal reaction at 200 ℃ for 12 h. After the reaction, allow it to cool naturally to room temperature, and separate the product by centrifugation (8000 rpm, 5 min). Wash the separated product alternately with deionized water and ethanol 5 times. Dry the washed product in a vacuum drying oven at 70 ℃ for 8 h to obtain a pale yellow powdery F-ZnIn2S4 photocatalyst, named F-ZIS-7%. (200) .

[0038] The pure ZnIn2S4 and F-ZnIn2S4 photocatalysts prepared in Comparative Examples 1 and Examples 1-7 were used for the photocatalytic degradation of formaldehyde in the air (initial concentration 50 ppm). The photocatalytic degradation performance of ZnIn2S4 and F-ZnIn2S4 on formaldehyde was tested in a custom-designed photocatalytic reactor. The test procedure was as follows: 20 mg of ZnIn2S4 or F-ZnIn2S4 photocatalyst was placed on a disc at the center of the photocatalytic reaction in the photocatalytic reactor, the reactor was sealed with quartz glass, and a xenon lamp was selected as the light source to degrade the formaldehyde in the reactor. The concentration change of formaldehyde was recorded using gas chromatography (GC). Photoelectric testing and photocatalytic effects showed that the sample F-ZIS-7% prepared at a ratio of 0.07 g:1 mmol of NH4F to ZnCl2 at 180℃ had the best performance, with a formaldehyde degradation rate of 93.6% after 3 hours; the degradation rates of samples prepared at ratios of 0.05 g:1 mmol of NH4F to ZnCl2 and 0.1 g:1 mmol of ZnCl2 were 85.2% and 89.7%, respectively.

[0039] like Figure 1 As shown, pure ZnIn2S4 ( Figure 1 (a1)~(a3)) and F-ZnIn2S4 ( Figure 1 SEM images of (b1)~(b3), (c1)~(c3), (d1)~(d3), (e1)~(e3), (f1)~(f3) show that its morphology is a spherical nanoflower structure. - The morphology of F-ZnIn2S4 did not change significantly after doping. The ZnIn2S4 spherical nanoflowers consist of a multi-level structure composed of randomly arranged nanosheets, and the nanosheet surfaces are smooth. Figure 1 (a1)~(a3)). After F - After doping, the nanoflower-like morphology and multilevel structure of the material remain unchanged, but with the increase of F - As the doping concentration increases, the nanosheets become more tightly packed, resulting in more dense spherical nanoflowers.

[0040] like Figure 2 As shown, the TEM image of F-ZIS-7% obtained in Example 4 shows a spherical structure. Figure 2 In (a), the size is approximately 4 μm. With increasing TEM magnification, the gray-black wrinkled edges of the spherical nanoflowers can be observed. Combined with SEM, this further illustrates that the F-ZIS nanoflower structure is composed of many thin-layered petal-like nanosheets. Figure 2 (b)~(c)).

[0041] like Figure 3As shown, the X-ray diffraction (XRD) spectra of pure ZnIn2S4 and F-ZnIn2S4 obtained from Comparative Example 1 and Examples 1-5 were analyzed to determine the crystallization characteristics of the samples. The characteristic peaks at 21.5°, 27.8°, 30.3°, 39.9°, 47.4°, 52.4°, and 55.8° correspond to the (006), (102), (104), (108), (110), (116), and (202) lattice planes of ZnIn2S4 (JCPDS No. 72-0773). With the increase in F... - The crystal phase of ZnIn2S4 did not change with the increase of doping amount, indicating that the doping did not produce other crystallization impurities and the crystal structure of ZnIn2S4 was well preserved.

[0042] like Figure 4 As shown, the electrochemical It curves of pure ZnIn2S4 and F-ZnIn2S4 obtained in Comparative Examples 1 and Examples 1-7 compare the interfacial charge transfer of the samples. The photoelectrode of each sample was measured in Na2SO4 solution with a switching interval of 50 s. - The photocurrent intensity of the doped F-ZnIn2S4 (Examples 1-5) was higher than that of pure ZnIn2S4 (Comparative Example 1). Further comparison of Examples 4, 6, and 7 showed that the catalyst synthesized at 180 °C exhibited the strongest photocurrent response intensity. The F-ZIS-7% obtained in Example 4 showed the best photocurrent response performance. Therefore, appropriate F... - Doping enhances the separation of photogenerated carriers, thereby significantly improving photocatalytic performance. However, excessive F... - Doping can hinder the effective separation of electron-hole pairs, thus negatively impacting the photocatalytic process.

[0043] like Figure 5 As shown, the photocatalytic degradation efficiency of formaldehyde by pure ZnIn2S4 and F-ZnIn2S4 samples was evaluated in a photocatalytic system (simulated sunlight under Xenon lamp illumination, UV-VIS Light) (expressed as normalized concentration (C0-C10)). t The degradation rate of formaldehyde by pure ZnIn2S4 was 59.5%, with F-ZIS-X% (X=1, 3, 5, 7, 10) in Examples 1-5 and F-ZIS-7% in Examples 6 and 7. (160) and F-ZIS-7% (200) The activity of [the substance] is significantly higher than that of pure ZnIn2S4, and the degradation rate of formaldehyde increases with F. -The photocatalyst activity increased with increasing dopant dosage, and the catalyst prepared at a reaction temperature of 180 °C showed superior performance, indicating that fluorination is an effective method to enhance the photocatalytic activity of ZnIn2S4. In particular, F-ZIS-7% exhibited the highest degradation rate (93.6%), approximately twice that of pure ZnIn2S4. However, excessive F... - With doping, for example in the F-ZIS-10% obtained in Example 5, the efficiency of formaldehyde degradation begins to decrease, compared to... Figure 4 This indicates that the recombination efficiency of photogenerated carriers in F-ZIS-10% increases, which is detrimental to the improvement of its photocatalytic activity.

[0044] This invention prepares a fluorine-doped ZnIn2S4 photocatalyst via a hydrothermal method. The fluorine-doped ZnIn2S4 photocatalyst exhibits enhanced photocatalytic activity and can effectively degrade VOCs in the air within a short reaction time.

[0045] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A fluorine-doped ZnIn2S4 photocatalyst, characterized in that, The morphology of the fluorine-doped ZnIn2S4 photocatalyst is a spherical nanoflower structure, which is composed of an arrangement of nanosheets.

2. The fluorine-doped ZnIn2S4 photocatalyst according to claim 1, characterized in that, The diameter of the spherical nanoflower structure is 4~10 μm.

3. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 1 or 2, characterized in that, Includes the following steps: (1) Add ZnCl2, InCl3·4H2O and thioacetamide to water and stir to obtain mixture A; (2) Add a fluoride source to mixture A and mix well to obtain mixture B; (3) The mixture B was subjected to a hydrothermal reaction. After the reaction was completed, the product was separated, washed and dried to obtain F-ZnIn2S4 photocatalyst.

4. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, The fluorine source is ammonium fluoride.

5. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, The ratio of fluorine source to ZnCl2 is (0.01~0.1) g: 1 mmol.

6. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, The hydrothermal reaction temperature is 160~200 ℃, and the time is 10~14 h.

7. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, The molar ratio of ZnCl2, InCl3·4H2O and thioacetamide is 1:1:

2.

8. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, In step (3), the washing involves rinsing with deionized water and ethanol 3 to 5 times respectively.

9. The method for preparing the fluorine-doped ZnIn2S4 photocatalyst according to claim 3, characterized in that, In step (3), the drying is performed under vacuum at 60-80 °C for 6-12 h.

10. The application of the fluorine-doped ZnIn2S4 photocatalyst according to claim 1 or 2 in the photocatalytic degradation of VOCs.

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