A method for preparing and applying a ZnSe / MnWO4 heterojunction photocatalyst

Abstract

This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing and applying a ZnSe / MnWO4 heterojunction photocatalyst. The ZnSe / MnWO4 heterojunction photocatalyst, synthesized by further solvothermal reaction of ZnSe prepared via a solvothermal reaction in a solution of MnWO4 prepared via a solvothermal reaction, can be applied to the photocatalytic reduction of CO2. Compared to existing photocatalysts, the ZnSe / MnWO4 heterojunction of this invention exhibits superior structural properties and stability. The built-in electric field at the heterojunction interface not only accelerates carrier separation and transfer but also enhances CO2 adsorption and activation, thereby increasing the photocatalytic reduction activity of CO2.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing and applying a ZnSe / MnWO4 heterojunction photocatalyst. Background Technology

[0002] Rapid societal development has led to a continuous increase in demand for fossil fuels, resulting in a significant increase in CO2 emissions. Current scientific research primarily focuses on developing efficient methods to convert CO2, which has high dissociation energy, into valuable chemical products. Among the many proposals, the solar-powered catalytic CO2 conversion scheme holds great potential. However, current photocatalysts for the photocatalytic reduction of CO2 using solar energy are relatively inefficient, making it difficult to meet humanity's energy demands.

[0003] ZnSe is widely used in the photocatalytic reduction of CO2 due to its excellent conductivity, stability, narrow bandgap, and low resistivity. However, pure ZnSe faces challenges such as low solar energy utilization and high carrier recombination rate. Therefore, synthesizing heterojunctions is an effective method to improve the solar energy utilization of ZnSe and reduce electron-hole recombination. This invention introduces a ZnSe / MnWO4 heterojunction to improve the separation efficiency of photogenerated electrons and holes, thereby enhancing photocatalytic activity. Furthermore, there are no previous reports on the use of ZnSe / MnWO4 heterojunctions as photocatalysts for CO2 reduction. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing and applying a ZnSe / MnWO4 heterojunction photocatalyst.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a ZnSe / MnWO4 heterojunction photocatalyst includes the following steps:

[0007] 1) Selenium powder, zinc chloride, and sodium hydroxide were placed in beakers containing equal amounts of deionized water and stirred thoroughly until they were evenly dispersed. Then, the zinc chloride solution was slowly poured into the beaker containing the selenium powder and stirred continuously until it was fully stirred. Then, the sodium hydroxide solution was slowly poured into the mixture of selenium powder and zinc chloride and stirred thoroughly. The mixture was then placed in an autoclave for hydrothermal reaction. After the reaction was completed, a yellow precipitate was obtained. The sample was washed and dried to obtain ZnSe.

[0008] 2) Dissolve manganese acetate and sodium tungstate separately in equal volumes of deionized water, stir until completely dissolved, then stir continuously, add sodium tungstate solution to manganese acetate solution, put the mixed solution into an autoclave for hydrothermal reaction, obtain a brown precipitate, wash the sample and dry to obtain MnWO4;

[0009] 3) Disperse the ZnSe obtained in step 1) in deionized water and stir until light yellow. Place the MnWO4 obtained in step 2) in a high-pressure reactor containing ZnSe solution for hydrothermal reaction. After the reaction is completed, wash the sample and dry it to obtain the ZnSe / MnWO4 heterojunction photocatalyst.

[0010] Furthermore, in the above preparation method, in step 1), the amount of selenium powder used is 0.158g, the amount of zinc chloride used is 0.271g, the amount of sodium hydroxide used is 0.64g, and the total amount of deionized water used is 60mL.

[0011] Furthermore, in the above preparation method, in step 1), the hydrothermal reaction temperature is 180℃ and the reaction time is 24h.

[0012] Furthermore, in the above preparation method, in step 2), the amount of manganese acetate is 0.491g, the amount of sodium tungstate is 0.6597g, and the total amount of deionized water is 60mL.

[0013] Furthermore, in the above preparation method, step 2), the hydrothermal reaction temperature is 150°C and the reaction time is 6 hours.

[0014] Furthermore, in the above preparation method, in step 3), the molar ratio of ZnSe to MnWO4 is 50%.

[0015] Preferably, in the above preparation method, in step 3), the amount of ZnSe is 0.145g, the amount of MnWO4 is 0.303g, and the amount of deionized water is 60mL.

[0016] Furthermore, in the above preparation method, step 3), the hydrothermal reaction temperature is 180℃ and the reaction time is 12h.

[0017] Furthermore, in the above preparation method, steps 1), 2), and 3), the stirring is performed using a magnetic stirrer.

[0018] Furthermore, in the above preparation method, in steps 1), 2), and 3), the drying temperature is 60°C and the drying time is 6 hours.

[0019] Application of ZnSe / MnWO4 heterojunction photocatalyst prepared by any of the above methods in photocatalytic reduction of CO2.

[0020] Furthermore, the above applications are implemented as follows:

[0021] 1) Spread the ZnSe / MnWO4 heterojunction photocatalyst evenly on a petri dish, add deionized water, and then dry it to make the catalyst evenly spread on the petri dish;

[0022] 2) Pour deionized water into the bottom of a transparent glass reaction vessel, then transfer the dried petri dish into the glass reaction vessel and seal the glass reaction vessel with a quartz glass lid; evacuate the glass reaction vessel, then fill it with CO2, and repeat the cycle four times; photocatalytically reduce CO2 under visible light irradiation.

[0023] Furthermore, in the above application, in step 1), the amount of ZnSe / MnWO4 heterojunction photocatalyst used is 10 mg, and the area of ​​the culture dish is 2 cm². 2 .

[0024] Furthermore, in the above application, step 2), the amount of deionized water used is 500 μL.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. The ZnSe / MnWO4 heterojunction photocatalyst prepared by the solvothermal method in this invention has a two-dimensional structure, which can increase the specific surface area, improve the carrier separation efficiency, and enhance the photocatalytic activity.

[0027] 2. The ZnSe / MnWO4 heterojunction photocatalyst prepared by this invention has a stronger ability to absorb visible light, which is an effective way to improve visible light photocatalytic activity.

[0028] 3. The ZnSe / MnWO4 heterojunction photocatalyst prepared by this invention has good photocatalytic reduction performance of CO2, and the method is simple to prepare, environmentally friendly and non-toxic, low cost, and conducive to large-scale production. Attached Figure Description

[0029] Figure 1 X-ray diffraction patterns of ZnSe, MnWO4, and ZnSe / MnWO4 heterojunction photocatalysts.

[0030] Figure 2 Time curves for the reduction of CO2 to CO by ZnSe, MnWO4, and ZnSe / MnWO4 heterojunction photocatalysts. Detailed Implementation

[0031] Example 1

[0032] The preparation method of ZnSe / MnWO4 heterojunction photocatalyst is as follows:

[0033] 1) Selenium powder (0.158g), zinc chloride (0.271g), and sodium hydroxide (0.64g) were placed in beakers containing equal volumes (20mL) of deionized water. The mixture was magnetically stirred until evenly dispersed. Then, the zinc chloride solution was slowly poured into the beaker containing the selenium powder, and the mixture was magnetically stirred until fully stirred. Next, the sodium hydroxide solution was slowly poured into the mixture of selenium powder and zinc chloride. After thorough magnetic stirring, the mixture was placed in an autoclave for a hydrothermal reaction (180℃, 24h). After the reaction was complete, a yellow precipitate was obtained. The sample was washed and dried at 60℃ for 6h to obtain ZnSe.

[0034] 2) Dissolve manganese acetate (0.491 g) and sodium tungstate (0.6597 g) separately in 30 mL of deionized water and stir magnetically until completely dissolved. Then, while continuously stirring magnetically, add the sodium tungstate solution to the manganese acetate solution. Place the mixed solution in an autoclave for hydrothermal reaction (150 °C, 6 h) to obtain a brown precipitate. Wash the sample and dry it at 60 °C for 6 h to obtain MnWO4.

[0035] 3) Disperse ZnSe (0.145g) in 60mL of deionized water and stir magnetically until light yellow. Then add 0.303g of MnWO4 and stir magnetically until uniform. Put the mixture into an autoclave for hydrothermal reaction (180℃, 12h). After the reaction is complete, wash the sample and dry it at 60℃ for 6h to obtain the ZnSe / MnWO4 heterojunction photocatalyst.

[0036] Figure 1 The X-ray diffraction pattern of the ZnSe / MnWO4 heterojunction photocatalyst prepared in Example 1 is shown. Characteristic diffraction peaks appear at 2θ = 27.224°, 45.195°, 53.568° and 65.858° and 72.632°, corresponding to the (111), (220), (331), (400) and (331) crystal planes, which is consistent with the ZnSe PDF standard card (PDF#37-1643). Characteristic diffraction peaks appear in the figure at 2θ = 18.315°, 23.516°, 24.032°, 29.786°, 30.209°, and 35.965°, corresponding to the (100), (001), (110), (-111), (111), and (021) crystal planes, which is consistent with the MnWO4 PDF standard card (PDF#10-0477). When the two are combined... Figure 1 As can be seen, the peaks of both substances appear in the composite sample ZnSe / MnWO4, indicating that the two substances were successfully composited.

[0037] Example 2

[0038] At room temperature and pressure, 10 mg of the ZnSe / MnWO4 heterojunction photocatalyst prepared in Example 1 was placed in a petri dish (2 cm²).2 Add deionized water droplets to the petri dish and spread it evenly. Then dry the petri dish in a 60°C oven until photocatalytic performance is tested. Pour 500 μL of deionized water into the bottom of a transparent glass reaction vessel, then transfer the dried petri dish to the glass reaction vessel and seal it with a quartz glass lid. Evacuate the glass reaction vessel, then fill it with CO2, repeating this process four times. Irradiate the photocatalyst using a 300W xenon lamp. After every 1 hour of irradiation, extract the upper gas layer from the vessel using a syringe and test the carbon monoxide concentration in the upper gas layer using a gas chromatograph. Continuously monitor for 4 hours (one cycle).

[0039] Figure 2 The time curve of photocatalytic reduction of CO2 to CO in the sample shows that after 4 hours of light irradiation, the CO production of ZnSe / MnWO4 is 8.897 μmol / g / h, which is 13.29 times that of pure ZnSe and 4.7 times that of pure MnWO4.

Claims

1. A method for preparing a ZnSe / MnWO4 heterojunction photocatalyst, characterized in that, Includes the following steps: 1) Selenium powder, zinc chloride, and sodium hydroxide were placed in beakers containing equal amounts of deionized water and stirred thoroughly until they were evenly dispersed. Then, the zinc chloride solution was slowly poured into the beaker containing selenium powder and stirred continuously until it was fully stirred. Then, the sodium hydroxide solution was slowly poured into the mixture of selenium powder and zinc chloride and stirred thoroughly. The mixture was then placed in an autoclave and subjected to a hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, a yellow precipitate was obtained. The sample was washed and dried to obtain ZnSe. 2) Dissolve manganese acetate and sodium tungstate in equal volumes of deionized water and stir until completely dissolved. Then stir continuously and add the sodium tungstate solution to the manganese acetate solution. Place the mixed solution in an autoclave and carry out a hydrothermal reaction at 150°C for 6 hours to obtain a brown precipitate. Wash the sample and dry it to obtain MnWO4. 3) Disperse the ZnSe obtained in step 1) in deionized water and stir until light yellow. Place the MnWO4 obtained in step 2) in a high-pressure reactor containing the ZnSe solution and carry out a hydrothermal reaction at 180℃ for 12 h. After the reaction is completed, wash the sample and dry it to obtain the ZnSe / MnWO4 heterojunction photocatalyst.

2. The preparation method according to claim 1, characterized in that, In step 1), the amount of selenium powder used is 0.158 g, the amount of zinc chloride used is 0.271 g, the amount of sodium hydroxide used is 0.64 g, and the total amount of deionized water used is 60 mL.

3. The preparation method according to claim 1, characterized in that, In step 2), the amount of manganese acetate used is 0.491 g, the amount of sodium tungstate used is 0.6597 g, and the total amount of deionized water used is 60 mL.

4. The preparation method according to claim 1, characterized in that, In step 3), the molar ratio of ZnSe to MnWO4 is 1:

2.

5. The preparation method according to claim 4, characterized in that, In step 3), the amount of ZnSe used is 0.145 g, the amount of MnWO4 used is 0.303 g, and the amount of deionized water used is 60 mL.

6. The preparation method according to claim 1, characterized in that, In steps 1), 2), and 3), the drying temperature is 60 °C and the drying time is 6 h.

7. The application of the ZnSe / MnWO4 heterojunction photocatalyst prepared by the preparation method according to any one of claims 1-6 in the photocatalytic reduction of CO2.

8. The application according to claim 7, characterized in that, The method is as follows: 1) Spread the ZnSe / MnWO4 heterojunction photocatalyst evenly on a petri dish, add deionized water, and then dry it to make the catalyst evenly spread on the petri dish; 2) Pour deionized water into the bottom of a transparent glass reaction vessel, then transfer the dried petri dish into the glass reaction vessel and seal the glass reaction vessel with a quartz glass lid; evacuate the glass reaction vessel, then fill it with CO2, and repeat the cycle four times; photocatalytically reduce CO2 under visible light irradiation.

9. The application according to claim 8, characterized in that, In step 1), the amount of ZnSe / MnWO4 heterojunction photocatalyst used was 10 mg, and the area of ​​the culture dish was 2 cm². 2 In step 2), the amount of deionized water used is 500 μL.

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