A method for preparing and applying a CuS / BiOBr heterojunction photocatalyst

Abstract

This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing and applying a CuS / BiOBr heterojunction photocatalyst. The CuS / BiOBr heterojunction photocatalyst, synthesized by solvothermal reaction of CuS prepared via CuS in a BiOBr precursor solution, can be applied to the photocatalytic reduction of CO2. Compared to existing photocatalysts, the CuS / BiOBr heterojunction of this invention exhibits good yield and stability. The strong built-in electric field at the heterojunction interface not only accelerates carrier separation and transfer but also enhances CO2 adsorption and activation, thereby enhancing 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 CuS / BiOBr heterojunction photocatalyst. Background Technology

[0002] With the dramatic increase in greenhouse gas emissions, finding an environmentally friendly solution to address excess carbon dioxide has become a global priority. Among these options, solar-driven photocatalysis stands out as the most ideal approach due to its convenience and effectiveness. Generally, a good photocatalytic CO2 reduction system requires high charge separation efficiency, good visible light utilization, and strong carbon dioxide adsorption capacity. However, CO2, as a nonpolar molecule with high dissociation energy, is exceptionally stable and therefore extremely difficult to activate during photocatalysis.

[0003] CuS, due to its excellent electrical conductivity and strong visible light absorption, is widely used in the field of photocatalytic CO2 reduction. However, several drawbacks significantly inhibit its photocatalytic CO2 reduction activity: high recombination efficiency of photogenerated carriers; low carbon dioxide adsorption; and problems of low solar energy utilization and high carrier recombination rate. Therefore, synthesizing heterojunctions is an effective method to improve the solar energy utilization of CuS and reduce electron-hole recombination. This invention introduces CuS / BiOBr to form a heterojunction, which can improve the separation efficiency of photogenerated electrons and holes, thereby improving photocatalytic activity; furthermore, there are no previous reports on CuS / BiOBr 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 CuS / BiOBr heterojunction photocatalyst.

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

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

[0007] 1) Copper acetate dihydrate and thiourea were placed in a beaker containing deionized water and stirred thoroughly until they were evenly dispersed. Then, they were placed in an autoclave for hydrothermal reaction. After the reaction was completed, a black precipitate was obtained. The sample was washed and dried to obtain CuS.

[0008] 2) Place CuS in a beaker containing ethylene glycol and stir to disperse it fully, obtaining solution A; place bismuth nitrate pentahydrate in a beaker containing ethylene glycol and sonicate to disperse it fully, then stir. During stirring, slowly add PVP, and after it is fully mixed, slowly add hexadecylammonium bromide and stir to obtain solution B; after stirring, slowly pour solution A into solution B while it is being stirred and continue stirring. After it is fully mixed, place it in an autoclave for hydrothermal reaction. After cooling, wash it three times with deionized water and ethanol respectively, and dry it to obtain CuS / BiOBr.

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

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

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

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

[0013] Furthermore, in the above preparation method, steps 1) and 2), the stirring is performed using a magnetic stirrer.

[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 CuS / BiOBr heterojunction photocatalysts prepared by any of the above methods in photocatalytic reduction of CO2.

[0016] Further, the above application is carried out as follows: The CuS / BiOBr heterojunction photocatalyst is evenly spread on a petri dish, then deionized water is added and the dish is dried to ensure the catalyst is evenly spread on the petri dish; deionized water is injected into the bottom of a transparent glass reaction vessel, and then the dried petri dish is transferred to the glass reaction vessel, which is then sealed with a quartz glass lid; the glass reaction vessel is evacuated, then filled with CO2, and this process is repeated four times; CO2 is then photocatalytically reduced under visible light irradiation.

[0017] Furthermore, in the above application, the amount of CuS / BiOBr heterojunction photocatalyst used is 20 mg, and 500 μL of deionized water is injected into the bottom of the glass reaction vessel, with a culture dish area of ​​2 cm². 2 .

[0018] The beneficial effects of this invention are as follows:

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

[0020] 2. The CuS / BiOBr 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.

[0021] 3. The CuS / BiOBr 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

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

[0023] Figure 2 Time curves for the reduction of CO2 to CO by CuS, BiOBr, and CuS / BiOBr heterojunction photocatalysts. Detailed Implementation

[0024] Example 1

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

[0026] 1) Weigh 0.363g of copper acetate dihydrate and 0.153g of thiourea into a beaker containing 40mL of deionized water. Stir the mixture magnetically until it is evenly dispersed. Then, place the mixture into an autoclave and heat it at 180℃ for 24h. After the reaction is complete, a black precipitate is obtained. Wash the sample and dry it at 60℃ for 6h to obtain CuS.

[0027] 2) Weigh 0.096 g of CuS and place it in a beaker containing 24 mL of ethylene glycol. Stir magnetically for 1 h to ensure thorough dispersion, obtaining solution A. Place 0.485 g of bismuth nitrate pentahydrate in a beaker containing 24 mL of ethylene glycol and sonicate for 30 min to ensure thorough dispersion. Stir magnetically for 1 h. During stirring, slowly add 0.05 g of PVP. After thorough mixing, slowly add 0.365 g of hexadecylammonium bromide and stir magnetically continuously to obtain solution B. After thorough stirring, slowly pour solution A into the stirring solution B and continue stirring magnetically for 30 min. After thorough mixing, transfer the mixture to a 100 mL reactor and heat at 160 °C for 10 h. After cooling, centrifuge three times with deionized water and three times with ethanol, and dry at 60 °C for 6 h to collect the CuS / BiOBr.

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

[0029] Weigh 0.485 g of bismuth nitrate pentahydrate and place it in a beaker containing 24 mL of ethylene glycol. Sonicate for 30 min to disperse it thoroughly, and then magnetically stir for 1 h. During the stirring process, slowly add 0.05 g of PVP. After it is fully mixed, slowly add 0.365 g of hexadecylammonium bromide and magnetically stir thoroughly. After it is fully mixed, transfer it to a 100 mL reaction vessel and heat it at 160 °C for 10 h. After the reaction is completed, wash the sample and dry it at 60 °C for 6 h to obtain BiOBr.

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

[0031] Example 2

[0032] At room temperature and pressure, 20 mg of CuS / BiOBr heterojunction photocatalyst was evenly spread in a 2 cm culture dish. 2Add deionized water to the petri dish and then dry it to ensure the catalyst is evenly spread on the petri dish. 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 each 1-hour irradiation period, extract the upper gas layer from the glass reaction vessel using a syringe and test the carbon monoxide concentration in the upper gas layer using a gas chromatograph. Continue this monitoring for 4 hours (one cycle).

[0033] 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 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. The application of a CuS / BiOBr heterojunction photocatalyst in the photocatalytic reduction of CO2, characterized in that, The preparation method of the CuS / BiOBr heterojunction photocatalyst includes the following steps: 1) Copper acetate dihydrate and thiourea were placed in a beaker containing deionized water and stirred thoroughly until evenly dispersed. Then, the mixture was placed in an autoclave for hydrothermal reaction. After the reaction was completed, a black precipitate was obtained. The sample was washed and dried to obtain CuS. 2) Take CuS and put it into a beaker containing ethylene glycol and stir to disperse it fully to obtain solution A; put bismuth nitrate pentahydrate into a beaker containing ethylene glycol and sonicate to disperse it fully, then stir. During the stirring process, slowly add PVP. After it is fully mixed, slowly add hexadecylammonium bromide and stir to obtain solution B; after stirring, slowly pour solution A into solution B and continue stirring. After it is fully mixed, put it into an autoclave for hydrothermal reaction. After cooling, wash it three times with deionized water and ethanol respectively, and dry it to obtain CuS / BiOBr.

2. The application according to claim 1, characterized in that, In step 1), the amount of copper 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 application according to claim 1, characterized in that, In step 1), the temperature of the hydrothermal reaction is 180°C and the reaction time is 24 h.

4. The application 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 hexadecylammonium bromide is 0.365 g.

5. The application 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 application according to claim 1, characterized in that, In steps 1) and 2), the stirring method is to use a magnetic stirrer.

7. The application 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. The application according to claim 1, characterized in that, The method is as follows: Take CuS / BiOBr heterojunction photocatalyst and spread it evenly on a petri dish, then add deionized water and dry it to make the catalyst spread evenly on the petri dish; inject deionized water into the bottom of a transparent glass reaction vessel, then transfer the dried petri dish to 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 operation four times; under visible light irradiation, photocatalytically reduce CO2.

9. The application according to claim 8, characterized in that, The CuS / BiOBr heterojunction photocatalyst was 20 mg, and 500 μL of deionized water was injected into the bottom of a glass reaction vessel. The culture dish had a surface area of ​​2 cm². 2 .

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