Preparation method and application of CuS / BiOBr heterojunction photocatalyst

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of a CuS / BiOBr heterojunction photocatalyst. The CuS prepared through a solvothermal reaction is placed in a precursor solution of BiOBr to be subjected to the solvothermal reaction to synthesize the CuS / BiOBr heterojunction photocatalyst, and the CuS / BiOBr heterojunction photocatalyst can be applied to the field of photocatalytic reduction of CO2. Compared with an existing photocatalyst, the CuS / BiOBr heterojunction has good yield and stability, and a strong built-in electric field at the heterojunction interface can accelerate separation and transfer of carriers and enhance adsorption and activation of CO2, so that the activity of photocatalytic reduction of CO2 is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a preparation method and application of a CuS / BiOBr heterojunction photocatalyst. Background Art

[0002] With the substantial increase in greenhouse gas emissions, finding an environmentally friendly solution to the problem of excess carbon dioxide gas has become a global hot topic. Among them, solar-driven photocatalysis has become the most ideal approach due to its convenience and effectiveness. Generally speaking, an excellent photocatalytic CO2 reduction system requires high charge separation efficiency, good visible light utilization, and strong carbon dioxide adsorption capacity. However, CO2 is particularly stable as a non-polar molecule with high dissociation energy, and is therefore extremely difficult to activate during the photocatalytic process.

[0003] CuS is widely used in the field of photocatalytic reduction of CO2 due to its excellent electrical conductivity and strong visible light absorption capacity. However, some disadvantages greatly inhibit its photocatalytic reduction of CO2 activity: high recombination efficiency of photogenerated carriers; low carbon dioxide adsorption; facing the problems of low solar energy utilization and high carrier recombination rate. Therefore, synthetic heterojunction is an effective method to improve the solar energy utilization of CuS and reduce the recombination of electron-hole pairs. The present invention introduces CuS / BiOBr to form a heterojunction, which can improve the separation efficiency of photogenerated electrons and holes, thereby improving the photocatalytic activity; and there is no related report on the use of CuS / BiOBr heterojunction as a photocatalyst for reducing CO2. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a preparation method and application of a CuS / BiOBr heterojunction photocatalyst.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing a CuS / BiOBr heterojunction photocatalyst comprises the following steps:

[0007] 1) copper acetate dihydrate and thiourea are placed in a beaker filled with deionized water, stirred thoroughly until they are evenly dispersed, and then placed in an autoclave for hydrothermal reaction. After the reaction is completed, a black precipitate is obtained. The sample is washed and dried to obtain CuS;

[0008] 2) CuS is placed in a beaker filled with ethylene glycol and stirred to be fully dispersed to obtain a solution A; bismuth nitrate pentahydrate is placed in a beaker filled with ethylene glycol and ultrasonically dispersed, and then stirred, and PVP is slowly added during the stirring process, and after the mixture is fully mixed, hexadecyl ammonium bromide is slowly added and stirred to obtain a solution B; after fully stirring, the solution A is slowly poured into the stirring solution B and continued to be stirred, and after fully mixing, the solution is placed in an autoclave for hydrothermal reaction, and after cooling, it is centrifugally washed three times with deionized water and ethanol respectively, and dried to obtain CuS / BiOBr.

[0009] Furthermore, in the above preparation method, in step 1), the amount of cupric acetate dihydrate used is 0.363 g, the amount of thiourea used is 0.153 g, and the amount of deionized water used is 40 mL.

[0010] Furthermore, in the above preparation method, in step 1), the temperature of the water reaction is 180° C. and the reaction time is 24 h.

[0011] Furthermore, in the above preparation method, in step 2), in solution A, the amount of CuS is 0.096 g, and the amount of ethylene glycol is 24 mL; in solution B, the amount of bismuth nitrate pentahydrate is 0.485 g, the amount of ethylene glycol is 24 mL, the amount of PVP is 0.05 g, and the amount of hexadecyl ammonium bromide is 0.365 g.

[0012] Furthermore, in the above preparation method, in step 2), the temperature of the hydrothermal reaction is 160° C. and the reaction time is 10 h.

[0013] Furthermore, in the above-mentioned preparation method, in steps 1) and 2), the stirring method is to use a magnetic stirrer for stirring.

[0014] Furthermore, in the above preparation method, in steps 1) and 2), the drying temperature is 60° C. and the drying time is 6 hours.

[0015] Application of the CuS / BiOBr heterojunction photocatalyst prepared by any of the preparation methods described above in photocatalytic reduction of CO2.

[0016] Furthermore, the above-mentioned application method is as follows: take the CuS / BiOBr heterojunction photocatalyst and spread it evenly on the culture dish, then add deionized water and then dry it to make the catalyst evenly spread on the culture dish; inject deionized water into the bottom of a transparent glass reaction container, then transfer the dry culture dish into the glass reaction container, and seal the glass reaction container with a quartz glass cover; evacuate the glass reaction container, and then fill it with CO2, and repeat the operation four times; photocatalytically reduce CO2 under visible light irradiation conditions.

[0017] Furthermore, for the above application, the amount of CuS / BiOBr heterojunction photocatalyst used is 20 mg, 500 μL of deionized water is injected into the bottom of the glass reaction container, and the culture dish area is 2 cm 2 .

[0018] The beneficial effects of the present invention are:

[0019] 1. The CuS / BiOBr heterojunction photocatalyst prepared by the solvothermal method of the present invention has a spherical structure, which can increase the specific surface area, improve the separation efficiency of carriers, and enhance the photocatalytic activity.

[0020] 2. The CuS / BiOBr heterojunction photocatalyst prepared by the present invention has a stronger ability to absorb visible light, and is an effective way to improve the catalytic activity under visible light.

[0021] 3. The CuS / BiOBr heterojunction photocatalyst prepared by the present invention has good photocatalytic reduction of CO2 performance, and the method is simple to prepare, environmentally friendly, non-toxic, low-cost, and conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 X-ray diffraction patterns of CuS, BiOBr, and CuS / BiOBr heterojunction photocatalysts.

[0023] Figure 2 This is the time curve of CuS, BiOBr, and CuS / BiOBr heterojunction photocatalysts reducing CO2 to CO. DETAILED DESCRIPTION

[0024] Example 1

[0025] The preparation method of CuS / BiOBr heterojunction photocatalyst is as follows:

[0026] 1) Weigh 0.363 g of copper acetate dihydrate and 0.153 g of thiourea into a beaker containing 40 mL of deionized water, stir them magnetically until they are evenly dispersed, and then place them in an autoclave for heating at 180° C. for 24 h. After the reaction is completed, a black precipitate is obtained. The sample is washed and dried at 60° C. for 6 h to obtain CuS.

[0027] 2) Weigh 0.096g of CuS and put it into a beaker containing 24mL of ethylene glycol and stir it magnetically for 1h to fully disperse it to obtain solution A. Put 0.485g of bismuth nitrate pentahydrate into a beaker containing 24mL of ethylene glycol and disperse it by ultrasonic for 30min, stir it magnetically for 1h, slowly add 0.05g of PVP during stirring, and then slowly add 0.365g of hexadecyl ammonium bromide and stir it magnetically after it is fully mixed to obtain solution B. After fully stirring, slowly pour solution A into the stirring solution B and continue to stir it magnetically for 30min. After fully mixing, put it into a 100mL reactor and heat it at 160℃ for 10h. After cooling, centrifuge it three times with deionized water and ethanol respectively, and dry it at 60℃ for 6h to collect CuS / BiOBr.

[0028] The preparation method of BiOBr is as follows:

[0029] Weigh 0.485 g of bismuth nitrate pentahydrate and put it into a beaker containing 24 mL of ethylene glycol, ultrasonically disperse it for 30 minutes, and magnetically stir it for 1 hour. During the stirring process, slowly add 0.05 g of PVP. After it is fully mixed, slowly add 0.365 g of hexadecyl ammonium bromide and fully magnetically stir it. After fully mixing, put it into a 100 mL reactor and heat it at 160°C for 10 hours. After the reaction is completed, wash the sample and dry it at 60°C for 6 hours to obtain BiOBr.

[0030] Figure 1 This is the X-ray diffraction pattern of the CuS / BiOBr heterojunction photocatalyst prepared in Example 1. In the figure, characteristic diffraction peaks appear at 2θ=10.946°, 25.260°, 31.810°, 47.769° and 58.226°, corresponding to (001), (011), (012), (201) and (023) crystal planes, which is consistent with the BiOBr PDF standard card (PDF#73-2061). Characteristic diffraction peaks appear at 2θ=27.925°, 29.542°, 32.071°, 33.152°, 49.747° and 59.902°, corresponding to (101), (102), (103), (006), (112) and (116) crystal planes, which is consistent with the CuS PDF standard card (PDF#75-2234). Figure 1 It can be seen that the peaks of both substances appear in the composite sample CuS / BiOBr, indicating that the two substances are successfully composited.

[0031] Example 2

[0032] At room temperature and pressure, 20 mg of CuS / BiOBr heterojunction photocatalyst was evenly spread on a culture dish (2 cm 2), then add deionized water and then dry it to make the catalyst evenly spread on the culture dish. Inject 500μL of deionized water into the bottom of the transparent glass reaction container, then transfer the dry culture dish into the glass reaction container, and seal the glass reaction container with a quartz glass cover. Evacuate the glass reaction container and then fill it with CO2, and repeat the operation four times. Use a 300W xenon lamp as a light source to illuminate the photocatalyst. After every 1h of illumination reaction, use a syringe to extract the upper gas from the glass reaction container, and use a gas chromatograph to test the carbon monoxide concentration in the upper gas, and continue to detect for 4h (one cycle).

[0033] Figure 2 This is a time curve of the sample's photocatalytic reduction of CO2 to CO. It can be seen that after 4 hours of light reaction, the CO production of CuS / BiOBr is 76.44 μmol / g / h, which is 32.52 times that of pure CuS and 3.27 times that of pure BiOBr.

Claims

1. A method for preparing a CuS / BiOBr heterojunction photocatalyst, characterized in that: The steps include: 1) copper acetate dihydrate and thiourea are placed in a beaker filled with deionized water, stirred thoroughly until they are evenly dispersed, and then placed in an autoclave for hydrothermal reaction. After the reaction is completed, a black precipitate is obtained. The sample is washed and dried to obtain CuS; 2) CuS is placed in a beaker filled with ethylene glycol and stirred to be fully dispersed to obtain a solution A; bismuth nitrate pentahydrate is placed in a beaker filled with ethylene glycol and ultrasonically dispersed, and then stirred, and PVP is slowly added during the stirring process, and after the mixture is fully mixed, hexadecyl ammonium bromide is slowly added and stirred to obtain a solution B; after fully stirring, the solution A is slowly poured into the stirring solution B and continued to be stirred, and after fully mixing, the solution is placed in an autoclave for hydrothermal reaction, and after cooling, it is centrifugally washed three times with deionized water and ethanol respectively, and dried to obtain CuS / BiOBr.

2. The preparation method according to claim 1, characterized in that: In step 1), the amount of cupric acetate dihydrate used is 0.363 g, the amount of thiourea used is 0.153 g, and the amount of deionized water used is 40 mL.

3. The preparation method according to claim 1, characterized in that: In step 1), the water reaction temperature is 180° C. and the reaction time is 24 h.

4. The preparation method according to claim 1, characterized in that: In step 2), in solution A, the amount of CuS is 0.096 g, and the amount of ethylene glycol is 24 mL; in solution B, the amount of bismuth nitrate pentahydrate is 0.485 g, the amount of ethylene glycol is 24 mL, the amount of PVP is 0.05 g, and the amount of hexadecyl ammonium bromide is 0.365 g.

5. The preparation method according to claim 1, characterized in that: In step 2), the temperature of the hydrothermal reaction is 160° C. and the reaction time is 10 h.

6. The preparation method according to claim 1, characterized in that: In steps 1) and 2), the stirring method is to use a magnetic stirrer for stirring.

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

8. Use of the CuS / BiOBr heterojunction photocatalyst prepared by the preparation method according to any one of claims 1 to 7 in photocatalytic reduction of CO2.

9. The use according to claim 8, characterized in that: The method is as follows: take a CuS / BiOBr heterojunction photocatalyst and spread it evenly on a culture dish, then add deionized water and then dry it to make the catalyst evenly spread on the culture dish; inject deionized water into the bottom of a transparent glass reaction container, then transfer the dry culture dish into the glass reaction container, and seal the glass reaction container with a quartz glass cover; evacuate the glass reaction container, then fill it with CO2, and repeat the operation four times; photocatalytically reduce CO2 under visible light irradiation conditions.

10. The use according to claim 9, characterized in that: The amount of CuS / BiOBr heterojunction photocatalyst used was 20 mg, and 500 μL of deionized water was injected into the bottom of the glass reaction container. The area of ​​the culture dish was 2 cm 2 .

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