S-bi double-defect bi 2s 3 / zns composite material and preparation method therefor

Abstract

Disclosed in the present application are an S-Bi double-defect Bi2S3 / ZnS composite material and a preparation method therefor. The method comprises: dissolving bismuth nitrate pentahydrate in a mannitol solution, so as to obtain a solution A; dissolving zinc chloride in water, so as to obtain a solution B; and mixing the solution A with the solution B, adding L-cysteine thereto, and then conducting a hydrothermal reaction, so as to obtain a composite material. By means of the method of the present application, the Bi2S3 / ZnS composite material containing both cationic Bi defects and anionic S defects can be obtained. The composite material can inhibit the recombination of photogenerated electron-hole pairs and achieve an effective improvement in the photocatalytic reduction ability regarding carbon dioxide while improving the transfer rate of photogenerated charges.

Description

A S-Bi double-defect Bi2S3 / ZnS composite material and its preparation method

[0001] Cross-references

[0002] This application claims priority to Chinese patent application No. 202311232657.6, filed on September 22, 2023, entitled “A S-Bi double-defect Bi2S3 / ZnS composite photocatalyst and its preparation method”, all disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present application belongs to the technical field of composite materials, and in particular relates to an S-Bi double-defect Bi2S3 / ZnS composite material and a preparation method thereof. Background Art

[0004] The massive consumption of fossil fuels has led to a dramatic increase in atmospheric carbon dioxide emissions, triggering global warming and an energy crisis, which has seriously impacted human sustainable development. Addressing the energy crisis and global warming is a critical issue that cannot be ignored. Solar energy is a renewable energy source with abundant energy reserves. Using solar energy as a power source, semiconductors as a medium, and carbon dioxide as a feedstock to convert this greenhouse gas into high-value-added hydrocarbon fuels not only addresses global warming at its source but also provides a new approach for developing alternative energy sources. Among semiconductor photocatalysts, metal sulfides ZnS and Bi2S3 are widely used for the photocatalytic reduction of carbon dioxide due to their suitable reduction potentials, broad visible light absorption range, and rapid electron transfer rates. However, factors such as the efficiency of photogenerated charge transfer and the recombination of photogenerated electron-hole pairs have long constrained the performance of photocatalysts. Therefore, it is particularly important to utilize methods such as defect engineering to improve the optoelectronic properties of materials and enhance their photocatalytic activity.

[0005] Current research indicates that defect engineering can effectively manipulate the internal electronic and geometric structures of photocatalysts, thereby improving their catalytic activity. Defects can be categorized into anionic and cationic defects based on the atomic charge within the compound. Anionic and cationic defects play different roles in photocatalytic materials: Cation defects tend to promote the transfer rate of photogenerated charges, while anionic defects are more conducive to inhibiting the recombination of photogenerated electron-hole pairs. By manipulating these defects, the photocatalytic performance of the material can be effectively enhanced.

[0006] However, there are currently no reports on the effective combination of cation defects and anion defects to achieve photocatalytic reduction of carbon dioxide to produce carbon monoxide and methane.

[0007] Application Contents

[0008] Based on the above technical problems, the present application provides a method for preparing a photocatalyst, which can obtain a Bi2S3 / ZnS composite material containing both cationic Bi defects and anionic S defects. It can promote the photogenerated charge transfer rate while inhibiting the recombination of photogenerated electron-hole pairs, thereby effectively improving the ability of photocatalytic reduction of carbon dioxide.

[0009] The specific application plan is as follows:

[0010] The present application provides a method for preparing an S-Bi double-defect Bi2S3 / ZnS composite material, comprising: dissolving bismuth nitrate pentahydrate in a mannitol solution to obtain solution A; dissolving zinc chloride in water to obtain solution B; mixing solution A and solution B, adding L-cysteine, and then subjecting the mixture to a hydrothermal reaction to obtain the composite material.

[0011] The method described in this application uses L-cysteine ​​as a sulfur source to form anionic S defects on ZnS, which can effectively promote the separation of photogenerated electron-hole pairs and improve the material's utilization rate of photogenerated charges; and mannitol is added as a solvent during the synthesis process to achieve effective regulation of metal cation Bi defects, forming cationic Bi defects on Bi2S3 without affecting S defects, thereby improving the transfer rate of photogenerated electrons.

[0012] Wherein, in solution A, the molar concentration of bismuth nitrate pentahydrate is 1-5mmol:30ml.

[0013] Wherein, the concentration of mannitol solution is 0.1-0.5M.

[0014] Wherein, in solution B, the molar concentration of zinc chloride is 0.3-6mmol:20ml.

[0015] The molar ratio of bismuth nitrate pentahydrate to zinc chloride is 2:0.3-6; the molar ratio of bismuth nitrate pentahydrate to L-cysteine ​​is 2:20-30.

[0016] The molar ratio of bismuth nitrate pentahydrate to zinc chloride is 2:3; the molar ratio of bismuth nitrate pentahydrate to L-cysteine ​​is 2:25.

[0017] The hydrothermal reaction temperature is 160-200° C., and the hydrothermal reaction time is 18-26 hours.

[0018] The method further includes washing and drying the hydrothermal product; the drying temperature is 50-80° C., and the drying time is 10-20 hours.

[0019] Wherein, zinc chloride is dissolved in water, ultrasonicated for 10-40 minutes, and stirred for 10-40 minutes to obtain solution B.

[0020] The present application also provides an S-Bi double-defect Bi2S3 / ZnS composite material, which is prepared by any of the above methods.

[0021] The beneficial effects of this application are:

[0022] The present application provides a preparation method for a Bi2S3 / ZnS composite material capable of simultaneously obtaining an S-Bi double defect. The method can form anionic Bi defects without affecting S defects.

[0023] The S-Bi double-defect Bi2S3 / ZnS composite material is used for the photocatalytic reduction of carbon dioxide. The regulation based on the two defects can promote the transfer rate of photogenerated charges while suppressing the recombination of photogenerated electron-hole pairs. At the same time, the presence of multiple site defects effectively increases the specific surface area of ​​the composite material, providing more reaction sites for the photocatalytic reduction of carbon dioxide reaction. In addition, the defects will also participate in the carbon dioxide reduction reaction as electron-rich centers, converting it into high-value-added hydrocarbons such as carbon monoxide and methane. Compared with the Bi2S3 / ZnS composite material with a single defect, its photocatalytic performance is significantly improved, providing a green and environmentally friendly, efficient treatment method and material basis for effectively solving the problem of carbon dioxide emission pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a SEM image of different samples, wherein (a) is the Bi2S3 obtained in Comparative Example 5, (b) is the ZnS obtained in Comparative Example 4, and (c) is the Bi2S3 / ZnS composite material obtained in Example 1;

[0025] Figure 2 shows the TEM, electron diffraction and HRTEM spectra of the Bi2S3 / ZnS composite material obtained in Example 1, wherein (d) is a TEM image, (e) is an electron diffraction image, and (f) is a HRTEM image;

[0026] FIG3 is an XRD spectrum of different samples, which correspond to the Bi2S3 obtained in Comparative Example 5, the ZnS obtained in Comparative Example 4, and the Bi2S3 / ZnS composite material obtained in Example 1;

[0027] Figure 4 shows the ESR spectra of different samples, where (a) is the ESR spectra of Bi2S3 in different solvents of Comparative Examples 5 and 6; (b) is the ESR spectra of ZnS obtained in Comparative Example 4, D-Bi2S3 obtained in Comparative Example 5, and Bi2S3 / ZnS obtained in Example 1;

[0028] FIG5 is a graph showing ultraviolet-visible diffuse reflectance spectra of different samples, namely, Bi2S3 obtained in Comparative Example 5, ZnS obtained in Comparative Example 4, and the Bi2S3 / ZnS composite material obtained in Example 1;

[0029] Figure 6 (a) shows the cycle characteristics of the Bi2S3 / ZnS composite material obtained in Example 1 for CO2 reduction, and (b) shows the XRD patterns before and after the reaction. DETAILED DESCRIPTION

[0030] Below, the present application describes the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration and are not to be construed as limiting the scope of the present application.

[0031] Evaluation of photocatalytic activity: In a 100mL stainless steel reactor, a 300W xenon lamp was used as the light source and the operating current was adjusted to 6A to test the CO2 reduction activity of the Bi2S3 / ZnS composite material. The composite material (10mg) was evenly dispersed in quartz glass, 18mL deionized water was used as the solvent, and 2mL TEOA was used as the sacrificial agent. After five minutes of ultrasonic vibration, it was transferred to a stainless steel reactor. Before the photoreduction CO2 experiment, high-purity CO2 gas (99.995%) was used to ventilate for 15 minutes to exhaust the air in the reactor. Then, the valve at one end of the reactor was closed, and high-purity CO2 gas was introduced until the pressure reached 4 bar. The xenon lamp was turned on for illumination. Samples were taken every 1h during the illumination process, and the gas products CO and CH4 were detected by gas chromatography (GC-2030).

[0032] Example 1

[0033] An S-Bi double-defect Bi2S3 / ZnS composite material, the preparation method of which comprises:

[0034] Weigh 2 mmol of bismuth nitrate pentahydrate into beaker A, measure 30 mL of 0.1 M mannitol solution and pour it into beaker A, mark it as solution A, and then stir it at room temperature for 1 hour until solution A becomes clear.

[0035] Weigh 3 mmol of zinc chloride and put it into beaker B. Measure 20 mL of deionized water and pour it into the beaker, marked as solution B. Ultrasonicate the solution for 30 minutes, and then stir it at room temperature for 30 minutes.

[0036] Pour solution A into solution B and stir for 10 minutes. Weigh 25 mmol of L-cysteine ​​and put it into a beaker. Stir for 1 hour. Then transfer the stirred mixture into a hydrothermal autoclave, seal it, put it into an oven, and react at 180°C for 22 hours. After the reaction is cooled to room temperature, take out the precipitate from the reactor and wash it several times with deionized water and ethanol. The obtained product is dried in an oven at 60°C for 12 hours.

[0037] Example 2

[0038] A S-Bi double-defect Bi2S3 / ZnS composite material, the preparation method of which is different from that of Example 1 only in that the amount of zinc chloride added is adjusted from "3 mmol" to "0.3 mmol", and the other steps and parameters are the same as those of Example 1.

[0039] Example 3

[0040] A S-Bi double-defect Bi2S3 / ZnS composite material, the preparation method of which is different from that of Example 1 only in that the amount of zinc chloride added is adjusted from "3 mmol" to "6 mmol", and the other steps and parameters are the same as those of Example 1.

[0041] Example 4

[0042] A S-Bi double-defect Bi2S3 / ZnS composite material, the preparation method of which is different from that of Example 1 only in that the concentration of the mannitol solution is adjusted from "0.1M" to "0.5mmol", and the other steps and parameters are the same as those of Example 1.

[0043] Comparative Example 1

[0044] A Bi2S3 / ZnS composite material, the preparation method of which is different from that of Example 1 only in that the solvent is adjusted from "mannitol solution" to "ethylene glycol solution", and the other steps and parameters are the same as those of Example 1.

[0045] Comparative Example 2

[0046] A Bi2S3 / ZnS composite material, the preparation method of which is different from that of Example 1 only in that the solvent is adjusted from "mannitol solution" to "potassium hydroxide solution", and the other steps and parameters are the same as those of Example 1.

[0047] Comparative Example 3

[0048] A Bi2S3 / ZnS composite material, the preparation method of which differs from that of Example 1 only in that the solvent is adjusted from "mannitol solution" to "sodium hydroxide solution", and the other steps and parameters are the same as those of Example 1.

[0049] Comparative Example 4

[0050] Synthesis of photocatalyst ZnS:

[0051] Dissolve 3 mmol of zinc chloride in 20 mL of deionized water. Place the solution in an ultrasonic cleaner and sonicate for 30 minutes. Then stir at room temperature for 30 minutes until the solution turns milky white. Then, add 25 mmol of L-cysteine ​​and stir at room temperature for 1 hour until the solution becomes transparent. The mixed solution is transferred to a sealed, polytetrafluoroethylene-lined stainless steel autoclave and allowed to react in an oven at 180°C for 22 hours. After the reaction cools to room temperature, remove the precipitate from the autoclave and rinse several times with deionized water and ethanol. The resulting product is dried in an oven at 60°C for 10 hours to obtain a ZnS sample.

[0052] Comparative Example 5

[0053] Synthesis of photocatalyst D-Bi2S3:

[0054] Dissolve 0.05 mol of mannitol in 500 mL of deionized water and sonicate for 30 minutes to prepare a 0.1 M mannitol solution. Weigh 2 mmol of bismuth nitrate pentahydrate and add 30 mL of the 0.1 M mannitol solution. Slowly pour the mannitol solution into a beaker and stir the solution at room temperature for 1 hour to clarify. Then, add 25 mmol of L-cysteine ​​to the mixed solution and stir at room temperature for 1 hour until the solution turns green and transparent. The mixed solution is then transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, sealed, and allowed to react in an oven at 180°C for 22 hours. After the reaction cools to room temperature, remove the precipitate from the autoclave and rinse several times with deionized water and ethanol. The resulting product is dried in an oven at 60°C for 12 hours to obtain the D-Bi2S3 sample.

[0055] Comparative Example 6

[0056] Synthesis of photocatalyst M-Bi2S3:

[0057] 2 mmol of Bi(NO₃)₃·5H₂O was dissolved in 30 mL of ethylene glycol and magnetically stirred at room temperature for 1 hour to form a transparent solution. 25 mmol of L-cysteine ​​was then added to the solution and stirred at room temperature for 1 hour until the solution became green and transparent. The mixed solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave, sealed, and reacted in an oven at 180°C for 22 hours. After the reaction cooled to room temperature, the precipitate was removed from the autoclave and rinsed several times with deionized water and ethanol. The resulting product was dried in an oven at 60°C for 12 hours to obtain the M-Bi₂S₃ sample.

[0058] The photocatalytic activities of the composite materials and photocatalysts obtained in the above examples and comparative examples were tested, and the yields of the reduction products CO and CH4 were measured after 5 hours of illumination, as shown in Table 1 below.

[0059] Table 1. Yields of reduction products CO and CH4

[0060] The data comparison above demonstrates that replacing the solvents described in the comparative examples of ethylene glycol (Comparative Example 1), potassium hydroxide (Comparative Example 2), and sodium hydroxide (Comparative Example 3) with the hydroxyl-containing mannitol described in the present invention significantly enhances the photocatalytic activity of the resulting Bi2S3 / ZnS composite. In particular, Example 1 achieved a 122% increase in CO yield compared to Comparative Example 1, far exceeding expectations. This demonstrates that the choice of solvent plays a significant role in the preparation of the S-Bi double-defect Bi2S3 / ZnS composite.

[0061] The above is only a preferred specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and application concept of the present application within the technical scope disclosed in the present application, and they should be covered by the scope of protection of the present application.

Claims

1. A method for preparing a S-Bi double-defect Bi2S3 / ZnS composite material, comprising: Dissolving bismuth nitrate pentahydrate in mannitol solution to obtain solution A; Dissolve zinc chloride in water to obtain solution B; The solution A is mixed with the solution B, L-cysteine ​​is added, and then the mixture is subjected to a hydrothermal reaction to obtain the product.

2. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: In solution A, the concentration of bismuth nitrate pentahydrate is 1-5mmol:30ml.

3. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: The concentration of mannitol solution is 0.1-0.5M.

4. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: In solution B, the molar concentration of zinc chloride is 0.3-6mmol:20ml.

5. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: The molar ratio of bismuth nitrate pentahydrate to zinc chloride is 2:0.3-6; the molar ratio of bismuth nitrate pentahydrate to L-cysteine ​​is 2:20-30.

6. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: The molar ratio of bismuth nitrate pentahydrate to zinc chloride is 2:3; the molar ratio of bismuth nitrate pentahydrate to L-cysteine ​​is 2:

25.

7. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: The hydrothermal reaction temperature is 160-200°C, and the hydrothermal reaction time is 18-26h.

8. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: The method also includes washing and drying the hydrothermal product; the drying temperature is 50-80° C. and the drying time is 10-20 hours.

9. The method for preparing the S-Bi double-defect Bi2S3 / ZnS composite material according to claim 1, wherein: Dissolve zinc chloride in water, sonicate for 10-40 minutes, and stir for 10-40 minutes to obtain solution B.

10. A S-Bi double-defect Bi2S3 / ZnS composite material, characterized in that: The method according to claim 1 is used to prepare the

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