Composite photocatalyst, preparation method and application thereof

Abstract

This invention discloses a composite photocatalyst, its preparation method, and its application in the field of photocatalysis technology. The method includes: indium chloride and thioacetamide are sequentially added to a mixed solution of deionized water and ethylene glycol and stirred until homogeneous. Cobalt tungstate is then added and stirring continues. Following a hydrothermal reaction, the mixture is washed and dried to obtain an In2S3 / CoWO4 composite photocatalyst with high photocatalytic performance. The In2S3 / CoWO4 obtained by this invention exhibits good dispersibility and structural stability. The In2S3 / CoWO4 catalyst obtained using this method achieves a formaldehyde degradation efficiency of up to 75.4% within one hour under visible light irradiation, and maintains good formaldehyde degradation performance even after 8 hours of continuous reaction. Simultaneously, the In2S3 / CoWO4 catalyst obtained using this method achieves a TC degradation efficiency of up to 83.5% within one hour under 5W LED light irradiation.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, and more specifically to a composite photocatalyst, its preparation method, and its application. Background Technology

[0002] The growing demand for clean energy and the escalating pollution problem are urgently driving the development of energy conversion and persistent pollutant removal technologies. Volatile organic compounds (VOCs), due to their high toxicity, easy diffusion, and volatility, constitute a key factor in air pollution. Formaldehyde (HCHO), a key member of aldehyde VOCs, is considered a major indoor air pollutant. Furthermore, tetracycline (TC) residues in water bodies can contribute to bacterial resistance and the spread of related genes, threatening public health.

[0003] In recent years, visible light-driven photocatalysis technology has become a promising strategy for addressing these challenges due to its high cost-effectiveness, strong environmental sustainability, and efficient degradation capabilities for pollutants such as HCHO and TC. Developing efficient and stable photocatalysts is a fundamental prerequisite for the practical application of photocatalysis technology. Summary of the Invention

[0004] The purpose of this invention is to address the problem that gaseous formaldehyde molecules are difficult to treat efficiently, quickly and thoroughly in traditional technologies, and to provide a highly efficient CoWO4 / In2S3 composite photocatalyst, its preparation method and application. This composite photocatalyst exhibits highly efficient photocatalytic degradation performance for both gaseous formaldehyde molecules and tetracycline, achieving the dual function of photocatalytic degradation of formaldehyde and TC.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A composite photocatalyst, wherein the composite photocatalyst is CoWO4 / In2S3, is obtained based on electrospinning technology combined with hydrothermal method; The composite photocatalyst was obtained by modifying micron-sized spherical In2S3 with nanorod-shaped CoWO4.

[0007] Furthermore, the diameter of the composite photocatalyst is 3.5-5 μm.

[0008] Furthermore, the mass ratio of the nanorod-shaped CoWO4 to the microsphere-shaped In2S3 is 2:10.

[0009] A method for preparing a composite photocatalyst includes the following steps: 1) Add ammonium metavanadate, cobalt nitrate hexahydrate, citric acid and polyvinylpyrrolidone to methanol and N,N-dimethylformamide in sequence, mix and stir until homogeneous to obtain a suspension; 2) The obtained precursor solution is loaded onto an electrospinning apparatus to obtain the precursor; 3) The precursor was calcined to obtain CoWO4 photocatalyst; 4) Add indium chloride and thioacetamide to a mixed solution of ethylene glycol and deionized water, stir for 1 h to form a transparent suspension, then add the CoWO4 photocatalyst obtained in step 3), and stir thoroughly to obtain a suspension; 5) The suspension undergoes a hydrothermal reaction to obtain a precipitate, which is the CoWO4 / In2S3 composite photocatalyst.

[0010] Furthermore, in step 1), the mass-to-volume ratio of ammonium metatungstate, cobalt nitrate hexahydrate, citric acid, polyvinylpyrrolidone, methanol, and N,N-dimethylformamide is 2.4535 g: 2.9105 g: 5 g: 9 g: 30 mL: 70 mL.

[0011] Furthermore, in step 2), the electrospinning conditions are: applying a high voltage of 15 kV and a spinning rate of 0.4 mL / h.

[0012] Furthermore, in step 3), the precursor calcination conditions are a heating rate of 2℃ / min and calcination at 600℃ for 120 min.

[0013] Furthermore, in step 4), the mass-to-volume ratio of indium chloride, thioacetamide, ethylene glycol, and deionized water is 339.37 mg: 172.85 mg: 5 mL: 25 mL.

[0014] Furthermore, in step 5), the hydrothermal reaction is carried out at 150°C for 12 hours. The precipitate was washed sequentially with deionized water and anhydrous ethanol, and the washed precipitate was dried at 80°C for 12 hours.

[0015] Application of composite photocatalysts in the photodegradation of formaldehyde and tetracycline.

[0016] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: The CoWO4 / In2S3 composite photocatalyst of the present invention has a stable structure, good dispersibility and adsorption properties, which are beneficial to electron transport; the CoWO4 / In2S3 composite photocatalyst of the present invention also has the characteristics of easy recovery and convenient operation.

[0017] The preparation method of this invention is simple and low in cost. The prepared In2S3 / CoWO4 composite photocatalyst has excellent formaldehyde degradation performance under visible light irradiation, with a degradation efficiency of up to 75.4% in one hour; under 5 W LED lamp irradiation, it has excellent TC degradation performance, with a degradation efficiency of up to 83.5% in one hour.

[0018] Photocatalysis is an advanced technology that utilizes sunlight as a driving force to convert inexhaustible solar energy into chemical energy. It can also transform many demanding chemical reactions into reactions that can occur under mild conditions at room temperature and pressure. It boasts advantages such as high photocatalytic degradation efficiency, complete degradation of organic pollutants, and no residue or secondary pollution after the reaction. Attached Figure Description

[0019] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 SEM image of the CoWO4 / In2S3 composite photocatalyst; Figure 2 The XRD pattern of the CoWO4 / In2S3 composite photocatalyst; Figure 3 The graph shows the formaldehyde degradation performance of the CoWO4 / In2S3 composite photocatalyst. Figure 4 Cyclic graph showing the formaldehyde degradation performance of the CoWO4 / In2S3 composite photocatalyst; Figure 5 XRD comparison images of formaldehyde degradation before and after by the CoWO4 / In2S3 composite photocatalyst; Figure 6 SEM comparison images of formaldehyde degradation before and after using CoWO4 / In2S3 composite photocatalyst. Figure 7 The graph shows the degradation performance of TC by the CoWO4 / In2S3 composite photocatalyst. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for preparing a CoWO4 / In2S3 composite photocatalyst includes the following steps: Example 1 (1) Preparation of CoWO4 photocatalyst: 2.4535g (NH4)6H2W 12 O 40 xH2O (ammonium metatungstate), 2.9105g Co(NO3)2 6H₂O (cobalt nitrate hexahydrate), 5g C₆H₈O₇ (citric acid), and 9g PVP (polyvinylpyrrolidone) were dissolved in a mixed solution containing 30mL methanol and 70mL DMF (N,N-dimethylformamide) and continuously stirred to form a uniformly dispersed solution. (The molar ratio of ammonium metatungstate, cobalt nitrate hexahydrate, citric acid, polyvinylpyrrolidone, methanol, and N,N-dimethylformamide was 8:10000:260:810:7425:9046.) Next, the precursor solution was loaded onto an electrospinning apparatus, and a high voltage of 15 kV was applied at a spinning rate of 0.4 mL / h. The distance between the needle tip and the collector was 15 cm. Finally, the mixture was calcined at 600 °C for 120 min at a heating rate of 2 °C / min to obtain the CoWO4 photocatalyst.

[0023] (2) Preparation of a 20% CoWO4 / In2S3 composite photocatalyst: 339.37 mg InCl3 (indium chloride) and 172.85 mg TAA (thioacetamide) were dissolved in a mixed solution of 5 mL ethylene glycol and 25 mL deionized water. The solution was stirred for 1 h to form a transparent suspension. Then, 50 mg of CoWO4 photocatalyst was weighed out, thoroughly stirred, and the solution was transferred to a 50 mL reaction vessel. The reaction was carried out in an oven at 150 °C for 12 h. (The molar ratio of indium chloride, thioacetamide, ethylene glycol, and deionized water was 153:230:8970:138800.) After the reaction vessel cooled to room temperature, it was washed with deionized water and anhydrous ethanol, and then the obtained product was dried in a vacuum oven at 80°C for 12 hours to obtain a 20% high-efficiency CoWO4 / In2S3 composite photocatalyst. The composite photocatalyst is nanorod-shaped CoWO4 modified with micron-sized spherical In2S3, wherein the mass ratio of CoWO4 to In2S3 is 2:10.

[0024] Figure 1 This is a SEM image of the CoWO4 / In2S3 composite photocatalyst.

[0025] Comparative Examples 1-4 The same preparation method and parameters as in Example 1 were used, except that the amounts of indium chloride and thioacetamide were changed, while the other conditions remained the same, thus changing the mass ratio of CoWO4 to In2S3.

[0026] In Comparative Example 1, 678.75 mg InCl3 and 345.70 mg TAA were added; in the CoWO4 / In2S3 composite photocatalyst prepared in Comparative Example 1, the mass ratio of CoWO4 to In2S3 was 1:10. In Comparative Example 2, 452.47 mg InCl3 and 230.45 mg TAA were added; in the CoWO4 / In2S3 composite photocatalyst prepared in Comparative Example 2, the mass ratio of CoWO4 to In2S3 was 1.5:10. In Comparative Example 3, 271.5 mg InCl3 and 138.28 mg TAA were added; in the CoWO4 / In2S3 composite photocatalyst prepared in Comparative Example 3, the mass ratio of CoWO4 to In2S3 was 2.5:10. In Comparative Example 4, 226.25 mg InCl3 and 115.23 mg TAA were added; in the CoWO4 / In2S3 composite photocatalyst prepared in Comparative Example 4, the mass ratio of CoWO4 to In2S3 was 3:30.

[0027] Preparation of pure In2S3 (Comparative Example 5): 221 mg InCl3 and 30 mg TAA were added to 30 mL of a 1:5 (V:V=1:5) mixture of ethylene glycol (EG) and water. The mixture was stirred at room temperature for 30 minutes to form a homogeneous solution. The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave and subjected to hydrothermal treatment at 150 °C, followed by heating in a convection oven for 12 hours. After natural cooling to room temperature, the solution was centrifuged and washed repeatedly (≥3 times) with deionized water and ethanol to remove impurities. The resulting product was then dried in a vacuum oven at 80 °C for 12 hours to obtain pure In2S3.

[0028] Verification of formaldehyde photodegradation efficiency using different catalysts: Grouping: 1) The 20% CoWO4 / In2S3 composite photocatalyst prepared in Example 1; 2) 15% CoWO4 / In2S3 composite photocatalyst of Comparative Example 2; 3) 25% CoWO4 / In2S3 composite photocatalyst of Comparative Example 3; 4) The CoWO4 photocatalyst prepared in step (1) of Example 1; 5) Pure In2S3 (Comparative Example 5); 20 mg of different catalysts were placed in 20 μL of formaldehyde gas with a concentration of 200 ppb and irradiated with a 300 W xenon lamp with a 420 nm filter for 60 min.

[0029] Figure 2 The images show the XRD patterns of different catalysts.

[0030] Figure 3 The graph shows the formaldehyde degradation efficiency of different catalysts. It can be seen that the 20% composite photocatalyst in Example 1 has excellent formaldehyde degradation performance, with a formaldehyde removal efficiency of up to 75.4% after the reaction.

[0031] Formaldehyde degradation cycle test: After a single photocatalytic degradation experiment of formaldehyde was completed, the reactor was opened, the formaldehyde source bottle was removed, and an equal volume of 37% formaldehyde solution was injected back into the glass bottle inside the reactor. The quartz window was sealed, the catalyst film was kept in its original state without being replaced, and the light source, temperature, nitrogen atmosphere, and water vapor conditions were kept consistent with the first experiment.

[0032] In each round of experiments, the formaldehyde was first adsorbed in the dark for 20 minutes, followed by photodegradation for 60 minutes. Samples were taken every 10 minutes, and the absorbance at 630 nm was measured using the phenol reagent spectrophotometric method to calculate the formaldehyde removal rate.

[0033] The degradation efficiency of each cycle was obtained by conducting eight consecutive cyclic tests.

[0034] Figure 4 The figure shows the formaldehyde degradation performance cycle of the 20% CoWO4 / In2S3 composite photocatalyst prepared in Example 1. As can be seen from the figure, the prepared composite photocatalytic membrane can still maintain good degradation performance after eight cycles under the same test method.

[0035] Figure 5 and Figure 6 The figures show XRD and SEM comparisons of the 20% CoWO4 / In2S3 composite photocatalyst prepared in Example 1 before and after formaldehyde degradation. As can be seen from the figures, there is no significant change in the XRD and SEM of the composite photocatalyst before and after the reaction, indicating that the composite photocatalyst has good stability.

[0036] Verification of the photodegradation efficiency of TC by different photocatalysts: 20 mg of photocatalyst from groups 1)-5) was placed in a reactor containing 20 mL of TC solution with a concentration of 40 ppm, and then reacted for 60 min under the irradiation of a 5 W LED lamp. Figure 7The graph shows the TC degradation efficiency of the CoWO4 / In2S3 composite photocatalyst prepared in Example 1. It can be seen that it has excellent TC removal performance, with a TC removal efficiency of up to 83.5% after the reaction.

[0037] The composite photocatalysts prepared in Example 1 and Comparative Examples 1-4 were tested under the same conditions using the same formaldehyde and TC removal performance testing methods described above. The degradation efficiency comparison is shown in Table 1 below. The degradation efficiency comparison is shown in Table 2 below using the same TC removal performance testing methods described above. Table 1. Test results of formaldehyde degradation performance of CoWO4 / In2S3 composite photocatalysts with other ratios.

[0038] Table 2. Test results of TC degradation performance of CoWO4 / In2S3 composite photocatalysts with other ratios.

[0039] As shown in the table above, when the mass ratio of CoWO4 to In2S3 is not within the 20% protected ratio of this invention, the degradation performance of formaldehyde and TC will be significantly reduced.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite photocatalyst, characterized by, The composite photocatalyst is CoWO4 / In2S3, which is obtained based on electrospinning technology combined with hydrothermal method; The composite photocatalyst was obtained by modifying micron-sized spherical In2S3 with nanorod-shaped CoWO4.

2. The composite photocatalyst according to claim 1, wherein The composite photocatalyst has a diameter of 3.5-5 μm.

3. The composite photocatalyst according to claim 1, wherein The mass ratio of the nanorod-shaped CoWO4 to the micron-shaped spherical In2S3 is 2:

10.

4. The method for preparing a composite photocatalyst according to any one of claims 1 to 3, characterized by, Includes the following steps: 1) Ammonium metavanadate, cobalt nitrate hexahydrate, citric acid and polyvinylpyrrolidone were added sequentially to methanol and N,N-dimethylformamide and mixed and stirred until a suspension was obtained; 2) The obtained precursor solution is loaded onto an electrospinning apparatus to obtain the precursor; 3) The precursor was calcined to obtain CoWO4 photocatalyst; 4) Add indium chloride and thioacetamide to a mixed solution of ethylene glycol and deionized water, stir for 1 h to form a transparent suspension, then add the CoWO4 photocatalyst obtained in step 3), and stir thoroughly to obtain a suspension; 5) The suspension undergoes a hydrothermal reaction to obtain a precipitate, which is the CoWO4 / In2S3 composite photocatalyst.

5. The preparation method according to claim 4, characterized in that, In step 1), the mass-to-volume ratio of ammonium metatungstate, cobalt nitrate hexahydrate, citric acid, polyvinylpyrrolidone, methanol, and N,N-dimethylformamide is 2.4535 g: 2.9105 g: 5 g: 9 g: 30 mL: 70 mL.

6. The preparation method according to claim 4, characterized in that, In step 2), the electrospinning conditions are: applying a high voltage of 15 kV and a spinning rate of 0.4 mL / h.

7. The preparation method according to claim 4, characterized in that, In step 3), the precursor calcination conditions are a heating rate of 2℃ / min and calcination at 600℃ for 120 min.

8. The preparation method according to claim 5, characterized in that, In step 4), the mass-to-volume ratio of indium chloride, thioacetamide, ethylene glycol, and deionized water is 339.37 mg: 172.85 mg: 5 mL: 25 mL.

9. The preparation method according to claim 5, characterized in that, In step 5), the hydrothermal reaction is carried out at 150°C for 12 hours. The precipitate was washed sequentially with deionized water and anhydrous ethanol, and the washed precipitate was dried at 80°C for 12 hours.

10. The application of the composite photocatalyst according to any one of claims 1-3 in the photodegradation of formaldehyde and tetracycline.

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