A method for preparing and applying a MoS2 / Bi2O2CO3 heterojunction photocatalyst

Abstract

The application belongs to the technical field of photocatalytic materials, and particularly relates to a preparation method and application of a MoS2 / Bi2O2CO3 heterojunction photocatalyst. A MoS2 / Bi2O2CO3 heterojunction is prepared by a simple hot solvent method. The formation of the heterojunction interface is conducive to the CO2 reduction reaction, and the results of the gas-solid heterogeneous photocatalytic CO2 reduction show 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. It is found through research that the enhanced photocatalytic activity can be attributed to the formed heterojunction, and the formation of the heterojunction inhibits the recombination of electrons and holes, so that more electrons can be used for the CO2 reduction reaction, and the reaction process is accelerated. The present application provides potential value for the gas-solid heterogeneous photocatalytic CO2 reduction reaction.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing and applying a MoS2 / Bi2O2CO3 heterojunction photocatalyst. Background Technology

[0002] Over a long period of development, humankind has continuously explored and utilized various energy sources. However, due to limitations in technology, there are still shortcomings in the recycling of energy, resulting in a large amount of energy being unused and turned into waste gas and wastewater. Among these, CO2 is the most abundant, and solving the problem of CO2 recycling will bring a milestone leap in solving the energy problem.

[0003] In recent years, researchers have focused on various photocatalysts, utilizing high-yield, simple-to-prepare photocatalysts. These catalysts, then illuminated under simulated sunlight, provide the energy needed for electron-hole separation in the photocatalytic CO2 reduction reaction. This process converts CO2 into CO, a more widely used form of carbon and hydrogen compounds. The newly generated CO can be used as a feedstock or fuel for the production of other alkanes, aldehydes, and formaldehyde. It can also be used to manufacture liquid fuels such as synthetic petroleum through water-gas shift reactions and the Fischer-Tropsch process. Traditional CO production primarily relies on burning fossil fuels, which is not only energy-intensive but also non-renewable. Therefore, the photocatalytic reduction of CO2 to CO is considered a potential pathway to reduce excessive fossil fuel consumption, obtain environmentally sustainable products, and mitigate climate change.

[0004] In bismuth-based semiconductors, Bi₂O₂CO₃ has attracted widespread attention from researchers due to its low production cost, safety, environmental friendliness, high stability, and strong internal electric field. MoS₂, with its stable chemical properties, tunable band gap, and large specific surface area, is a novel graphene-like layered compound. Molybdenum disulfide possesses numerous unsaturated active sites at the edges of its sheets, thus exhibiting strong adsorption capacity and photocatalytic activity. Based on the aforementioned characteristics of Bi₂O₂CO₃ and MoS₂, this paper presents a novel MoS₂ / Bi₂O₂CO₃ heterojunction prepared using a simple solvothermal method, successfully growing MoS₂ onto Bi₂O₂CO₃. In gas-solid heterogeneous photocatalytic activity tests, the new heterojunction material exhibits significantly higher photocatalytic activity, exceeding that of the original material by 8.6 times and 3.0 times, respectively. This research provides potential value for gas-solid heterogeneous photocatalytic CO₂ reduction. Summary of the Invention

[0005] This invention relates to a method for preparing a MoS2 / Bi2O2CO3 heterojunction photocatalyst and its application.

[0006] The technical solution adopted in this invention is: a MoS2 / Bi2O2CO3 heterojunction photocatalyst, the preparation method of which includes the following steps:

[0007] 1) Dissolve bismuth nitrate pentahydrate in HNO3 solution. After complete dissolution, add citric acid to the above mixed solution. While stirring, add NaOH solution to adjust the pH. Then, put it into an autoclave for hydrothermal reaction. Finally, centrifuge to collect the white precipitate and dry it to obtain Bi2O2CO3.

[0008] 2) Disperse Bi2O2CO3 into a beaker containing deionized water. After the dispersion is uniform, place the heat-treated MoS2 into a beaker containing Bi2O2CO3 solution and stir until uniform. Then, place it into an autoclave for hydrothermal reaction. After the reaction is completed, centrifuge to collect the sample and dry it to obtain the 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, the hydrothermal reaction in step 1) is carried out at 180°C for 24 hours.

[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 hydrothermal reaction temperature is 130℃ and the reaction time is 2h.

[0013] In the aforementioned MoS2 / Bi2O2CO3 heterojunction photocatalyst, step 2) involves the following steps to prepare the heat-treated MoS2: MoS2 is dispersed in a beaker containing deionized water, stirred vigorously until homogeneous, then placed in an autoclave for hydrothermal reaction. The black product is then collected by centrifugation and finally dried to obtain the heat-treated MoS2. 。

[0014] The above-mentioned MoS2 / Bi2O2CO3 heterojunction photocatalyst has a hydrothermal reaction temperature of 130℃ and a reaction time of 2h.

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

[0016] The above application is carried out as follows: The above MoS2 / Bi2O2CO3 heterojunction photocatalyst is placed in a crucible at the bottom of the reactor. Deionized water is added dropwise to the reaction vessel. Then, the glass reactor is vacuum-treated. After repeated evacuation and aeration several times, high-purity CO2 is introduced and CO2 is photocatalytically reduced under a 300W xenon lamp.

[0017] The beneficial effects of this invention are as follows:

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

[0019] 2. The MoS2 / Bi2O2CO3 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

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

[0021] Figure 2 The product yield (CO)-time curves of photocatalytic reduction of CO2 by MoS2, Bi2O2CO3, and MoS2 / Bi2O2CO3 heterojunction photocatalysts are shown. Detailed Implementation

[0022] Example 1: MoS2 / Bi2O2CO3 heterojunction photocatalyst

[0023] 1. Preparation of Bi₂O₂CO₃:

[0024] First, 1.5 mmol (0.728 g) of Bi(NO)3·5H2O was dissolved in 30 ml of a pre-prepared 1.2 mol / L HNO3 solution. After the solution changed from a white, turbid state to a colorless and transparent state, 0.144 g of citric acid was added. Subsequently, an 8 mol / L NaOH solution was slowly added dropwise while simultaneously measuring the pH value. Once the pH reached 6, the addition of NaOH solution was stopped. The solution was stirred at room temperature for 30 min, then transferred to an 80 ml hot reaction vessel and maintained at 180 °C for 24 h. After natural cooling, the precipitate was washed by centrifugation, dried at 60 °C, and reserved for later use.

[0025] 2. Preparation of MoS2:

[0026] The purchased MoS2 was heat-treated by dispersing 0.5g of MoS2 in 150ml of deionized water and vigorously stirring the mixture until it was evenly dispersed. The solution was then transferred to a reactor and kept at 130℃ for 2 hours. After natural cooling, the product was dried to obtain a black product.

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

[0028] 2 mmol (0.102 g) of the prepared Bi₂O₂CO₃ was dispersed in 30 ml of deionized water and stirred for 20 min. Then, the heat-treated MoS₂ was added, and the mixture was stirred vigorously until homogeneous. Simultaneously, three aliquots of the Bi₂O₂CO₃ precursor solution were prepared, with 0.009 g, 0.012 g, and 0.015 g of MoS₂ added, respectively. The mixed solutions were kept at 130 °C for two hours. Based on the different masses of MoS₂ added, the products were designated as 9% MB (0.009 g), 12% MB (0.012 g), and 15% MB (0.015 g), respectively.

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

[0030] Example 2

[0031] At room temperature and pressure, 40 mg of the prepared photocatalytic sample was placed in a 20 mm diameter circular crucible. A small amount of deionized water was added, followed by ultrasonic treatment for 5 min. The sample was then dried and placed at the bottom of a glass reaction vessel. 0.5 ml of deionized water was added to the reaction vessel. The glass reactor was then subjected to vacuum treatment, and after repeated evacuation and purging five times, high-purity CO2 was introduced into the reactor. The photocatalytic reduction reaction was carried out under a 300 W xenon lamp. The reactor was placed 3 cm below the xenon lamp light source. Finally, 1 ml of the generated gas was extracted using a microsyringe and quantitatively analyzed using a gas chromatograph (GC-1690).

[0032] Figure 2The CO yield-time curve of the photocatalytic reduction of CO2 in the sample shows that after 4 hours of light irradiation, the CO yield of MoS2 / Bi2O2CO3 is 36.8 μmol / g, which is 8.6 times that of pure MoS2 and 3.0 times that of pure Bi2O2CO3.

Claims

1. The application of a MoS2 / Bi2O2CO3 heterojunction photocatalyst in the photocatalytic reduction of CO2, characterized in that, The method is as follows: The MoS2 / Bi2O2CO3 heterojunction photocatalyst is placed in a crucible at the bottom of a reactor. Deionized water is added dropwise to the reaction vessel. Then, the glass reactor is vacuum-treated, and after repeated evacuation and aeration several times, high-purity CO2 is introduced. CO2 is then photocatalytically reduced under a 300W xenon lamp. The preparation method of the MoS2 / Bi2O2CO3 heterojunction photocatalyst includes the following steps: 1) With a molar ratio of bismuth nitrate pentahydrate to citric acid = 2:1, bismuth nitrate pentahydrate was dissolved in HNO3 solution. After complete dissolution, citric acid was added to the above mixed solution. NaOH solution was added to adjust the pH while stirring. Then, the mixture was placed in an autoclave and subjected to hydrothermal reaction at 180°C for 24 hours. Finally, the white precipitate was collected by centrifugation and dried to obtain Bi2O2CO3. 2) Disperse Bi2O2CO3 into a beaker containing deionized water. After the dispersion is uniform, place the heat-treated MoS2 into a beaker containing Bi2O2CO3 solution and stir until uniform. The mass ratio of MoS2 to Bi2O2CO3 is 12% or 15%. Then, place the mixture in an autoclave and carry out a hydrothermal reaction at 130℃ for 2 hours. After the reaction is completed, centrifuge to collect the sample and dry it to obtain the MoS2 / Bi2O2CO3 heterojunction photocatalyst.

2. The application according to claim 1, characterized in that, In step 2), the preparation method of heat-treated MoS2 includes the following steps: MoS2 is dispersed in a beaker containing deionized water, stirred vigorously until homogeneous, and then placed in an autoclave for hydrothermal reaction. The black product is then collected by centrifugation and finally dried to obtain heat-treated MoS2.

3. The application according to claim 2, characterized in that, The hydrothermal reaction temperature is 130℃, and the reaction time is 2 hours.

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