Preparation method and application of MoS2 / Bi2O2CO3 heterojunction photocatalyst

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of a MoS2 / Bi2O2CO3 heterojunction photocatalyst. The MoS2 / Bi2O2CO3 heterojunction is prepared through a simple thermal solvent method. The formation of a heterojunction interface is beneficial to the proceeding of CO2 reduction reaction, and the gas-solid heterogeneous photocatalytic CO2 reduction result shows that the CO yield of the MoS2 / Bi2O2CO3 heterojunction photocatalyst is 8.6 times and 3.0 times higher than that of the original MoS2 and Bi2O2CO3 respectively. Research finds that the enhanced photocatalytic activity can be attributed to the formed heterojunction, and the formation of the heterojunction inhibits recombination of electrons and holes, so that more electrons can be used for CO2 reduction reaction, and the reaction process is accelerated. The method provides a potential value for the gas-solid heterogeneous photocatalytic CO2 reduction reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and specifically relates to a preparation method and application of a MoS2 / Bi2O2CO3 heterojunction photocatalyst. Background Art

[0002] After a long period of development, humans have continuously developed and utilized various types of energy. However, due to the limitations of scientific and technological levels, humans are still lacking in the recycling of energy, resulting in a large amount of energy being turned into waste gas, wastewater, etc. without being fully utilized. Among them, CO2 is the largest in volume. How to solve the recycling problem of CO2 will bring a milestone leap in solving the energy problem.

[0003] In recent years, researchers have focused their attention on the study of various types of photocatalysts, using high-yield, simple-to-prepare photocatalysts, and then providing the energy required for electron-hole separation for the photocatalytic CO2 reduction reaction under the irradiation of light simulating sunlight. The photocatalytic CO2 reduction reaction converts CO2 into CO, which has a wider range of uses, as well as other carbon and hydrogen compounds. The newly generated CO can be used as a raw material or fuel for the production of other alkanes, aldehydes, and formaldehyde, and can also be used to make liquid fuels such as synthetic petroleum through the water gas shift reaction and the Fischer-Tropsch process. Traditional CO is basically obtained by burning fossil fuels, which not only wastes energy but is also non-renewable. Therefore, CO2 photoreduction to CO is considered a potential way to reduce excessive fossil consumption, obtain environmentally sustainable products, and mitigate climate change.

[0004] Among bismuth-based semiconductors, Bi2O2CO3 has attracted extensive attention from researchers due to its low production cost, safety and environmental protection, high stability, and strong internal electric field. MoS2 has stable chemical properties, adjustable band gap width, and large specific surface area. It is a new type of graphene-like layered compound. Molybdenum disulfide has a large number of unsaturated active sites at the edge of the sheet, so it has strong adsorption capacity and photocatalytic activity. Based on the above characteristics of Bi2O2CO3 and MoS2, this paper uses a simple solvothermal method to prepare a new MoS2 / Bi2O2CO3 heterojunction, and successfully grows MoS2 on Bi2O2CO3. In the gas-solid heterogeneous photocatalytic activity test, the new heterojunction material has higher photocatalytic activity, which is 8.6 times and 3.0 times higher than the original material performance, respectively. This study provides potential value for gas-solid heterogeneous photocatalytic CO2 reduction. Summary of the invention

[0005] The present invention discloses a preparation method and application of a MoS2 / Bi2O2CO3 heterojunction photocatalyst.

[0006] The technical solution adopted by the present invention is: a MoS2 / Bi2O2CO3 heterojunction photocatalyst, and the preparation method comprises the following steps:

[0007] 1) dissolving bismuth nitrate pentahydrate in HNO3 solution, and after it is completely dissolved, adding citric acid to the mixed solution, adding NaOH solution to adjust the pH under stirring, and then putting it into an autoclave for hydrothermal reaction, and finally collecting the white precipitate by centrifugation, and drying to obtain Bi2O2CO3;

[0008] 2) Bi2O2CO3 is dispersed in a beaker filled with deionized water. After the dispersion is uniform, the heat-treated MoS2 is placed in a beaker filled with Bi2O2CO3 solution and stirred evenly, and then placed in an autoclave for hydrothermal reaction. After the reaction is completed, the sample is collected by centrifugation and dried to obtain a MoS2 / Bi2O2CO3 heterojunction photocatalyst.

[0009] In the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, in step 1), the molar ratio of bismuth nitrate pentahydrate to citric acid is 2:1.

[0010] In the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, in step 1), the hydrothermal reaction is at 180°C and the reaction time is 24h.

[0011] In the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, in step 2), the mass ratio of MoS2 to Bi2O2CO3 is 9%, 12% or 15%.

[0012] In the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, in step 2), the temperature of the hydrothermal reaction is 130°C and the reaction time is 2h.

[0013] In the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, in step 2), the preparation method of heat-treated MoS2 comprises the following steps: dispersing MoS2 into a beaker filled with deionized water, vigorously stirring it evenly, placing it into an autoclave for hydrothermal reaction, then centrifuging and collecting the black product, and finally drying it to obtain the heat-treated MoS2. 。

[0014] For the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, the hydrothermal reaction temperature is 130°C and the reaction time is 2h.

[0015] Application of the above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst in photocatalytic reduction of CO2.

[0016] The above application method is as follows: place the above MoS2 / Bi2O2CO3 heterojunction photocatalyst in a crucible, place it at the bottom of the reactor, add deionized water into the reaction vessel, and then vacuum the glass reactor. After repeated evacuation and ventilation for several times, fill it with high-purity CO2, and photocatalytically reduce CO2 under a 300W xenon lamp.

[0017] The beneficial effects of the present invention are:

[0018] 1. The MoS2 / Bi2O2CO3 heterojunction photocatalyst prepared by the present invention has a larger specific surface area, better photoelectric activity and stronger ability to absorb visible light, and is an effective way to improve visible light catalytic activity.

[0019] 2. The MoS2 / Bi2O2CO3 heterojunction photocatalyst prepared by the present invention has good photocatalytic and 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

[0020] Figure 1 These are the X-ray diffraction patterns of MoS2, Bi2O2CO3, and MoS2 / Bi2O2CO3 heterojunction photocatalysts.

[0021] Figure 2 This is the product yield (CO)-time curve of the photocatalytic reduction of CO2 by MoS2, Bi2O2CO3, and MoS2 / Bi2O2CO3 heterojunction photocatalysts. DETAILED DESCRIPTION

[0022] Example 1 MoS2 / Bi2O2CO3 Heterojunction Photocatalyst

[0023] 1. Preparation of Bi2O2CO3:

[0024] First, 1.5mmol (0.728g) Bi(NO)3·5H2O was dissolved in 30ml of 1.2mol / L HNO3 solution prepared in advance. After the solution was stirred from white turbidity to colorless and transparent, 0.144g of citric acid was added. Then, 8mol / L NaOH solution was slowly added to the solution. The pH value of the solution was measured at the same time. After the pH value of the solution was adjusted to 6, the addition of NaOH solution was stopped. After the above solution was stirred at room temperature for 30min, it was transferred to an 80ml hot reaction container and kept at 180° for 24h. After natural cooling, the precipitate was washed by centrifugation, dried at 60°, and reserved for use.

[0025] 2. Preparation of MoS2:

[0026] The purchased MoS2 was heat treated by dispersing 0.5g MoS2 into 150ml deionized water, stirring the mixed solution vigorously to disperse it, and after the MoS2 was evenly dispersed, it was transferred to the reactor and kept at 130° for 2h. After natural cooling, it was dried to obtain a black product.

[0027] 3. Preparation of MoS2 / Bi2O2CO3 photocatalyst:

[0028] Disperse 2mmol (0.102g) of prepared Bi2O2CO3 in 30ml of deionized water, stir for 20min, add the above heat-treated MoS2, and then stir vigorously until the solution is uniform. At the same time, prepare three Bi2O2CO3 precursor solutions, add 0.009g, 0.012g, and 0.015g MoS2 respectively. Keep the mixed solution at 130℃ for two hours. According to the different masses of MoS2 added, the products are recorded as 9% MB (0.009g), 12% MB (0.012g), and 15% MB (0.015g).

[0029] Figure 1 This is the X-ray diffraction pattern of the MoS2 / Bi2O2CO3 heterojunction photocatalyst prepared in Example 1. In the figure, a characteristic diffraction peak appears at 2θ=14.4°, corresponding to the (002) and crystal planes, which is consistent with the MoS2 PDF standard card (PDF#77-1716). In the figure, characteristic diffraction peaks appear at 2θ=12.9°, 23.9°, 30.2° and 32.7°, corresponding to the (002), (011), (013) and (110) and (622) crystal planes, which is consistent with the Bi2O2CO3 PDF standard card (PDF#41-1488). When the two are combined, Figure 1 It can be seen that the peaks of both substances appear in the composite sample MoS2 / Bi2O2CO3, indicating that the two substances are successfully composited.

[0030] Example 2

[0031] At room temperature and pressure, take 40 mg of the prepared photocatalytic sample, place it in a round crucible with a diameter of 20 mm, add a small amount of deionized water and ultrasonically treat it for 5 minutes, then dry the sample, put the dried sample at the bottom of the glass reaction container, and add 0.5 ml of deionized water to the reaction container. Then vacuum the glass reactor, repeatedly evacuate and ventilate it 5 times, and then fill the glass reactor with high-purity CO2. The photocatalytic reduction reaction is carried out under a 300w xenon lamp. The reactor is placed 3 cm away from the xenon lamp light source. Finally, 1 ml of the generated gas is extracted using a micro-syringe and quantitatively analyzed by gas chromatograph (GC-1690).

[0032] Figure 2This is the product of the photocatalytic reduction of CO2 of the sample: CO production-time curve. It can be seen that after 4 hours of light reaction, the CO production of MoS2 / Bi2O2CO3 is 36.8μmol / g, which is 8.6 times that of pure MoS2 and 3.0 times that of pure Bi2O2CO3.

Claims

1. A MoS2 / Bi2O2CO3 heterojunction photocatalyst, characterized in that: The preparation method comprises the following steps: 1) dissolving bismuth nitrate pentahydrate in HNO3 solution, and after it is completely dissolved, adding citric acid to the mixed solution, adding NaOH solution to adjust the pH under stirring, and then putting it into an autoclave for hydrothermal reaction, and finally collecting the white precipitate by centrifugation, and drying to obtain Bi2O2CO3; 2) Bi2O2CO3 is dispersed in a beaker filled with deionized water. After the dispersion is uniform, the heat-treated MoS2 is placed in a beaker filled with Bi2O2CO3 solution and stirred evenly, and then placed in an autoclave for hydrothermal reaction. After the reaction is completed, the sample is collected by centrifugation and dried to obtain a MoS2 / Bi2O2CO3 heterojunction photocatalyst.

2. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 1, characterized in that: In step 1), the molar ratio of bismuth nitrate pentahydrate to citric acid is 2:

1.

3. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 1, characterized in that: In step 1), the hydrothermal reaction is at 180° C. and the reaction time is 24 h.

4. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 1, characterized in that: In step 2), the mass ratio of MoS2 to Bi2O2CO3 is 9%, 12% or 15%.

5. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 1, characterized in that: In step 2), the temperature of the hydrothermal reaction is 130° C. and the reaction time is 2 h.

6. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 1, characterized in that: In step 2), the preparation method of heat-treated MoS2 includes the following steps: dispersing MoS2 into a beaker filled with deionized water, vigorously stirring it evenly, placing it into an autoclave for hydrothermal reaction, then centrifuging and collecting the black product, and finally drying it to obtain heat-treated MoS2. 。 7. The MoS2 / Bi2O2CO3 heterojunction photocatalyst according to claim 6, characterized in that: The temperature of the hydrothermal reaction was 130°C and the reaction time was 2 h.

8. Use of the MoS2 / Bi2O2CO3 heterojunction photocatalyst 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: the MoS2 / Bi2O2CO3 heterojunction photocatalyst described in any one of claims 1 to 7 is placed in a crucible, placed at the bottom of a reactor, deionized water is dripped into the reaction container, and then the glass reactor is vacuum-treated, and after repeated evacuation and ventilation for several times, high-purity CO2 is filled in, and CO2 is photocatalytically reduced under a 300W xenon lamp.

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