Metal Mg-mediated BiOCl photocatalyst, preparation method thereof and application of metal Mg-mediated BiOCl photocatalyst in photocatalytic carbon dioxide reduction

Abstract

The invention discloses a metal Mg-mediated BiOCl photocatalyst as well as a preparation method and application thereof in photocatalytic carbon dioxide reduction, and belongs to the technical field of photocatalytic materials. The Mg-mediated BiOCl photocatalyst is synthesized through a hydrothermal method, and the photocatalytic performance is optimized by regulating and controlling the Mg / Bi molar ratio. The preparation method comprises the following steps: dissolving bismuth nitrate pentahydrate and mannitol in deionized water to prepare a precursor solution A; adding a certain amount of magnesium chloride hexahydrate into a sodium chloride solution to prepare a precursor solution B; and uniformly mixing the prepared precursor B and the prepared precursor A, and obtaining the Mg-mediated BiOCl photocatalyst by using a hydrothermal method. Mg mediation can greatly improve the activity of photocatalytic reduction of carbon dioxide by BiOCl.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a metal Mg-mediated BiOCl photocatalyst, its preparation method, and its application in photocatalytic carbon dioxide reduction. Background Technology

[0002] The rapid development of human society has led to a continuous increase in the demand for fossil fuels, and the problems of environmental pollutant emissions and energy shortages have become increasingly prominent. Photocatalysis technology, with its green, efficient, and sustainable characteristics, has attracted widespread attention in fields such as pollutant degradation, carbon dioxide reduction, and water splitting for hydrogen production. Bismuth oxychloride, as a typical layered perovskite semiconductor photocatalytic material, has a unique electronic structure, good chemical stability, and visible light response, and is considered one of the most promising photocatalytic materials.

[0003] Pure-phase BiOCl exhibits limited adsorption capacity for carbon dioxide and poor activation effect, resulting in low photocatalytic activity and conversion efficiency. To improve the photocatalytic performance of BiOCl, researchers have employed various modification strategies, including mediation, recombination, and morphology regulation. Metal ion mediation is an effective method that introduces heteroions to regulate the electronic structure of BiOCl, reducing the probability of electron-hole recombination and enhancing its light absorption capacity and photocatalytic activity.

[0004] Magnesium is an abundant, non-toxic, and inexpensive metallic element. Currently, the preparation of Mg-mediated BiOCl photocatalysts faces challenges such as complex processes, demanding reaction conditions, and poor mediating uniformity, limiting their large-scale production and application. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a metal Mg-mediated BiOCl photocatalyst, its preparation method, and its application in the photocatalytic reduction of carbon dioxide.

[0006] The technical solution adopted in this invention is: a metal Mg-mediated BiOCl photocatalyst, wherein the molar ratio of Mg to Bi in the photocatalyst is 1%-10%.

[0007] The above-mentioned method for preparing a metal Mg-mediated BiOCl photocatalyst includes the following steps:

[0008] 1) Bismuth nitrate pentahydrate and mannitol were dissolved in deionized water to prepare precursor solution A;

[0009] 2) A certain amount of magnesium chloride hexahydrate was added to a sodium chloride solution to prepare precursor solution B;

[0010] 3) Mix precursor solution B and precursor solution A evenly, and react them using a hydrothermal method. After the reaction system cools naturally to room temperature, collect the precipitate, wash and dry it to obtain the Mg-mediated BiOCl photocatalyst.

[0011] In the above preparation method, in step 1), the ratio of bismuth nitrate pentahydrate: mannitol: deionized water is 0.5-1g: 0.5-1g: 20-50ml.

[0012] In the above preparation method, step 2), the ratio of magnesium chloride hexahydrate to sodium chloride to water is 4 - 41 mg: 11 g: 30 ml.

[0013] In the above preparation method, step 3), the hydrothermal method has a reaction temperature of 120-180℃ and a reaction time of 3-16 hours.

[0014] In the preparation method described above, step 3) involves washing with deionized water and ethanol alternately, 3-5 times each, using centrifugal washing at a speed of 5000-8000 r / min for 5-10 minutes.

[0015] In the preparation method described above, step 3) involves drying at a temperature of 60-80°C under vacuum for 10-15 hours.

[0016] The above describes the application of a Mg-mediated BiOCl photocatalyst in the photocatalytic reduction of carbon dioxide.

[0017] The above application is carried out in the following way: Under visible light irradiation, the above Mg-mediated BiOCl photocatalyst is placed in a closed space filled with carbon dioxide gas, and the carbon dioxide gas is reduced to carbon monoxide gas.

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

[0019] 1. This invention uses a hydrothermal method to synthesize a metal Mg-mediated BiOCl photocatalyst. The process is simple, the reaction conditions are mild, and it improves the carrier separation efficiency and enhances the photocatalytic activity.

[0020] 2. By modifying with Mg ions, the electronic structure of BiOCl can be effectively regulated, the recombination rate of photogenerated electron-hole pairs can be reduced, and its absorption capacity for visible light can be improved, thus significantly enhancing the photocatalytic activity of BiOCl.

[0021] 3. The metal Mg-mediated BiOCl photocatalyst prepared in this invention has good chemical stability, stronger photocatalytic reduction ability, participates in catalytic reactions, and has good photocatalytic reduction performance of carbon dioxide. Attached Figure Description

[0022] Figure 1 X-ray diffraction patterns of BOC, 1-MBOC, 5-MBOC, and 10-MBOC photocatalysts.

[0023] Figure 2 Scanning electron microscope images of BOC (a) and 5-MBOC (b).

[0024] Figure 3 Photoluminescence spectra of BOC, 1-MBOC, 5-MBOC, and 10-MBOC photocatalysts.

[0025] Figure 4 A comparison diagram of the photocatalytic reduction of carbon dioxide using BOC, 1-MBOC, 5-MBOC, and 10-MBOC photocatalysts.

[0026] Figure 5 A comparison chart showing the performance of BOC, 1-MBOC, 5-MBOC, and 10-MBOC photocatalysts in reducing CO2 to CO. Detailed Implementation

[0027] Example 1: A metal Mg-mediated BiOCl photocatalyst (magnesium to bismuth molar ratio of 1%)

[0028] 1) Dissolve 1g of bismuth nitrate pentahydrate and 0.55g of mannitol in 40ml of deionized water. Stir the resulting solution at room temperature for 30 minutes to obtain precursor solution A.

[0029] 2) Dissolve 11g of sodium chloride in 30ml of deionized water, and slowly add 4.1mg of magnesium chloride hexahydrate under stirring. Stir for 30 minutes to obtain precursor solution B.

[0030] 3) Disperse precursor solution A in precursor solution B while stirring for 2 hours. Place the solution in a 100 mL stainless steel high-temperature reactor and heat at 160 °C for 3 hours. Finally, allow the solution to cool naturally to room temperature. Collect the precipitate by centrifugation and wash it three times with deionized water and anhydrous ethanol alternately by centrifugation at 5000-8000 r / min for 5-10 minutes. Dry the precipitate overnight in a vacuum oven at 60 °C to obtain the metal Mg-mediated BiOCl photocatalyst, labeled as 1-MBOC.

[0031] Comparative Example

[0032] The original BOC was prepared using the same process as in Example 1 without the addition of magnesium chloride hexahydrate.

[0033] Example 2: A metal Mg-mediated BiOCl photocatalyst (magnesium to bismuth molar ratio of 5%)

[0034] 1) Preparation of precursor solution A: Same as in Example 1.

[0035] 2) Dissolve 11g of sodium chloride in 30ml of deionized water, and slowly add 20.3mg of magnesium chloride hexahydrate under stirring. Stir for 30 minutes to obtain precursor solution B.

[0036] 3) Disperse precursor solution A in precursor solution B while stirring for 2 hours. Place the solution in a 100 mL stainless steel high-temperature reactor and heat at 160 °C for 3 hours. Finally, allow the solution to cool naturally to room temperature. Collect the precipitate by centrifugation and wash it three times alternately with deionized water and anhydrous ethanol at a speed of 5000-8000 r / min for 5-10 minutes. Dry the precipitate overnight in a vacuum oven at 60 °C to obtain a Mg-mediated BiOCl photocatalyst with a magnesium to bismuth molar ratio of 5%, labeled as 5-MBOC.

[0037] Figure 2 In the image, a and b are scanning electron microscope images of BOC and 5-MBOC, respectively. From... Figure 2 As can be seen from a, BiOCl forms a nanosheet structure. Figure 2 As can be seen from b, the introduction of Mg slightly alters the nanosheet structure of BiOCl, indicating that the Mg-mediated BiOCl photocatalyst was successfully prepared.

[0038] Figure 3 The image shows the photoluminescence spectrum of the Mg-mediated BiOCl photocatalyst. Figure 3 As can be seen, the 5-MBOC composite sample has the lowest PL emission peak, which proves that the composite sample has the advantage of high separation efficiency for photogenerated electron and hole pairs when the molar ratio of magnesium to bismuth is 5%.

[0039] Example 3: A metal Mg-mediated BiOCl photocatalyst (magnesium to bismuth molar ratio of 10%)

[0040] 1) Preparation of precursor solution A: Same as in Example 1.

[0041] 2) Dissolve 11g of sodium chloride in 30ml of deionized water, and slowly add 40.6mg of magnesium chloride hexahydrate under stirring. Stir for 30 minutes to obtain precursor solution B.

[0042] 3) Disperse precursor solution A in precursor solution B while stirring for 2 hours. Place the solution in a 100 mL stainless steel high-temperature reactor and heat at 160 °C for 3 hours. Finally, allow the solution to cool naturally to room temperature. Collect the precipitate by centrifugation and wash it three times alternately with deionized water and anhydrous ethanol at a speed of 5000-8000 r / min for 5-10 minutes. Dry the precipitate overnight in a vacuum oven at 60 °C to obtain a Mg-mediated BiOCl photocatalyst with a magnesium to bismuth molar ratio of 10%, labeled as 10-MBOC.

[0043] X-ray diffraction analysis was performed on the BOC, 1-MBOC, 5-MBOC, and 10-MBOC prepared by the above method. The test results are as follows: Figure 1 As shown in the figure, the typical characteristic peak of BOC has shifted slightly, indicating the successful preparation of 1-MBOC, 5-MBOC, and 10-MBOC.

[0044] Example 4: Application of a metal Mg-mediated BiOCl photocatalyst in the photocatalytic reduction of carbon dioxide

[0045] The Mg-mediated BiOCl photocatalysts prepared in Examples 1, 2, and 3, and the BOC prepared in the comparative example, were used to conduct photocatalytic reduction experiments on carbon dioxide. The test procedure was as follows: Using a 300 W xenon lamp as the light source, 10 mg of each of the prepared BOC, 1-MBOC, 5-MBOC, and 10-MBOC samples were mixed thoroughly with 1 mL of ethanol, dropped onto a petri dish, and dried. The samples were then evenly spread and placed in reaction containers, with 1 mL of deionized water added. A vacuum pump was used to evacuate the sealed container, and carbon dioxide gas was passed through, repeated three times. Then, illumination was applied. After each 30-minute illumination, the gas in the sealed container was extracted, and the carbon monoxide concentration was measured using a gas chromatograph. This was repeated four times. The test results are as follows: Figure 4 and Figure 5 .

[0046] Carbon dioxide is reduced under visible light irradiation. For example... Figure 4 As shown, the Mg-mediated BiOCl photocatalyst prepared in Example 2 exhibits excellent photocatalytic activity and stability. The Mg-mediated BiOCl photocatalyst is an effective way to promote photocatalytic reactions. Figure 5 As shown, the carbon monoxide formation rate of 1-MBOC reaches 9.175 μmol·h⁻¹. -1 ·g -1 The carbon monoxide formation rate of 5-MBOC reached 13.45 μmol·h⁻¹. -1 ·g -1The carbon monoxide formation rate of 10-MBOC reached 11.4 μmol·h⁻¹. -1 ·g -1 The carbon monoxide formation rate of pure BiOCl was only 4.895 μmol·h⁻¹. -1 ·g -1 .

Claims

1. A metal Mg-mediated BiOCl photocatalyst, characterized in that, The molar ratio of Mg to Bi in the photocatalyst is 1%-10%.

2. A method for preparing a metal Mg-mediated BiOCl photocatalyst, characterized in that, Includes the following steps: 1) Bismuth nitrate pentahydrate and mannitol were dissolved in deionized water to prepare precursor solution A; 2) A certain amount of magnesium chloride hexahydrate was added to a sodium chloride solution to prepare precursor solution B; 3) Mix precursor solution B and precursor solution A evenly, and react them using a hydrothermal method. After the reaction system cools naturally to room temperature, collect the precipitate, wash and dry it to obtain the Mg-mediated BiOCl photocatalyst.

3. The preparation method according to claim 2, characterized in that, In step 1), the ratio of bismuth nitrate pentahydrate: mannitol: deionized water is 0.5-1g: 0.5-1g: 20-50ml.

4. The preparation method according to claim 2, characterized in that, In step 2), the ratio of magnesium chloride hexahydrate to sodium chloride to water is 4-41 mg: 11 g: 30 ml.

5. The preparation method according to claim 2, characterized in that, In step 3), the hydrothermal method has a reaction temperature of 120-180℃ and a reaction time of 3-16 hours.

6. The preparation method according to claim 2, characterized in that, In step 3), the washing is performed by alternating between deionized water and ethanol, 3-5 times each, using centrifugal washing at a speed of 5000-8000 r / min for 5-10 minutes.

7. The preparation method according to claim 2, characterized in that, In step 3), the drying temperature is 60-80℃, vacuum drying is performed, and the drying time is 10-15 hours.

8. The application of the metal Mg-mediated BiOCl photocatalyst according to claim 1 in the photocatalytic reduction of carbon dioxide.

9. The application according to claim 8, characterized in that, The method is as follows: Under visible light irradiation, the metal Mg-mediated BiOCl photocatalyst is placed in a sealed space filled with carbon dioxide gas, and the carbon dioxide gas is reduced to carbon monoxide gas.

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