Preparation method of bismuth trisulfide carbon nanotube heterojunction photocatalytic material as well as product and application of bismuth trisulfide carbon nanotube heterojunction photocatalytic material

Abstract

The invention provides a preparation method of a Bi2S3 / carbon nanotube heterojunction photocatalytic material. Bi2S3 enhances the absorption of visible light by the material and widens the absorption band of sunlight by the material; the heterostructure improves the distribution of photon-generated carriers, improves the separation efficiency of electron-hole pairs, and plays an important role in improving the photocatalytic performance of the material. The preparation process is relatively simple and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing a heterojunction photocatalytic material, which is particularly suitable for the degradation of organic pollutants under solar photocatalysis. Background Technology

[0002] Semiconductor photocatalysis technology can directly convert solar energy into chemical and electrical energy, and has broad application prospects in energy development and environmental governance. This field has been focusing on the development of high-efficiency visible light-responsive photocatalytic materials.

[0003] Catalyst activity is one of the main factors affecting photocatalytic efficiency. According to the reaction principle, catalyst activity is influenced by factors such as band structure, crystal form, morphology, size, and specific surface area. The redox capability of photogenerated carriers is closely related to the band position of the catalyst. An increase in conduction band potential weakens the reduction capability of photogenerated electrons; an increase in valence band potential enhances the oxidation capability of photogenerated holes. Simultaneously, a wider band gap results in a smaller response range to sunlight, reducing the utilization rate of visible light.

[0004] Carbon nanotubes, as a typical polymer semiconductor material, possess excellent thermal and chemical stability, making them promising photocatalysts. The C atoms in the carbon nanotube molecule form a highly delocalized π-conjugated system with sp2 hybridization. To further improve the photocatalytic performance of carbon nanotubes, methods such as noble metal deposition, metal ion doping, and semiconductor composites are commonly used to modify them. Bismuth sulfide (Bi₂S₃) is a narrow bandgap (1.3–1.7 eV) semiconductor material with advantages such as low cost, non-toxicity, and high photosensitivity, making it of significant research value. However, Bi₂S₃ suffers from photocorrosion and high electron-hole recombination rates, resulting in poor photocatalytic performance.

[0005] Considering the complementary nature of carbon nanotubes and Bi2S3 in absorbing sunlight, combining the two to prepare Bi2S3 / carbon nanotube composite materials is expected to significantly improve photocatalytic activity. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a heterojunction photocatalytic material with a wide absorption band of sunlight.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a Bi2S3 / carbon nanotube heterojunction photocatalytic material includes the following steps: 1) Preparation of carbon nanotube dispersion Weigh out multi-walled carbon nanotubes and dispersant, add them to deionized water, and homogenize under high pressure at 1500 bar for 3 min to obtain carbon nanotube dispersion. 2) Preparation of Bi2S3 / carbon nanotube heterojunction photocatalytic materials Thiourea was dissolved in deionized water and stirred until the solution was clear; this solution was denoted as solution A. A soluble bismuth salt was dissolved in urea solution and stirred vigorously; this solution was denoted as solution B. Solution A was added dropwise to solution B while stirring vigorously, and stirring was continued for 30–60 min after the addition was complete. Add the carbon nanotube dispersion prepared in step 1), stir evenly, and transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. After sealing, place it in an oven at 120–150 °C and heat for 12–15 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the mixture in the reactor, collect the precipitate, and wash the precipitate with deionized water. Repeat the centrifugation and washing at least three times. Place the precipitate in an oven and dry it at 80–95 °C for 18–24 h to obtain the Bi2S3 / carbon nanotube heterojunction photocatalytic material.

[0008] According to one embodiment of the present invention, the dispersant in step 1) is a cationic dispersant or a nonionic dispersant.

[0009] This invention involves the reaction of thiourea with soluble bismuth salts in a carbon nanotube dispersion under hydrothermal conditions to generate bismuth sulfide crystals. These bismuth sulfide crystals then deposit on the surface of the carbon nanotubes, forming a heterojunction structure. The reaction product, ammonium nitrate, is a weakly acidic substance, and the hydrothermal system gradually generates positively charged hydrogen ions. Using cationic or nonionic dispersants, the carbon nanotubes are unaffected by these positively charged hydrogen ions and can maintain stable dispersion in the hydrothermal system. However, if anionic dispersants are used, they easily bind with hydrogen ions, weakening the dispersing ability and causing flocculation of the carbon nanotubes, thus preventing the formation of the Bi₂S₃ / carbon nanotube heterojunction structure.

[0010] According to one embodiment of the present invention, the molar concentration of thiourea in solution A is 0.2 to 0.3 mol / L.

[0011] According to one embodiment of the present invention, the molar concentration of the urea solution is 1 to 1.5 mol / L.

[0012] According to one embodiment of the present invention, the soluble bismuth salt is bismuth nitrate pentahydrate.

[0013] According to one embodiment of the present invention, the molar concentration of bismuth nitrate pentahydrate in solution B is 0.1 to 0.15 mol / L.

[0014] According to one embodiment of the present invention, the mass ratio of the carbon nanotubes added in step 2) to the bismuth nitrate pentahydrate in solution B is 0.35 to 2.65:1.

[0015] The present invention relates to a heterojunction photocatalytic material for the photocatalytic degradation of organic pollutants by sunlight, which has a wide absorption band and high degradation efficiency.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing a Bi₂S₃ / carbon nanotube heterojunction photocatalytic material. Bi₂S₃ enhances the material's absorption of visible light, broadening its absorption band for sunlight; the heterostructure improves the distribution of photogenerated carriers and increases the electron-hole pair separation efficiency, playing a crucial role in enhancing the material's photocatalytic performance. This preparation process is relatively simple and easy to operate. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments; these examples are provided for illustrative purposes only and do not limit the present invention in any way.

[0018] Example 1 The preparation of the heterojunction photocatalytic material in this embodiment includes the following steps: 1) Preparation of carbon nanotube dispersion Weigh 3.0 g of carbon nanotubes and 1.0 g of cationic dispersant Hypermer KD2 (purchased from Croda Chemicals (Shanghai) Co., Ltd.), add 6 g of deionized water, and homogenize under high pressure at 1500 bar for 3 min to obtain a carbon nanotube dispersion with a mass concentration of 30%.

[0019] 2) Preparation of Bi2S3 / carbon nanotube heterojunction photocatalytic materials Weigh 0.30 g of thiourea and dissolve it in deionized water. Stir for 10 min until the solution is clear, then bring the volume to 20 mL. This solution is labeled as solution A. Dissolve 1.94 g of bismuth nitrate pentahydrate in 1 mol / L urea solution and stir vigorously. Bring the volume to 40 mL. This solution is labeled as solution B. Under vigorous stirring, add solution A dropwise to solution B. After the addition is complete, continue stirring for 30 min. Add 2.29 g of the carbon nanotube dispersion prepared in step 1), stir until homogeneous, and then transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. Seal the reactor and place it in a 120 ℃ oven, heating at 120 ℃ for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the mixture in the reactor, collect the precipitate, and wash the precipitate with deionized water. Repeat centrifugation and washing at least three times. Place the precipitate in an oven and dry at 80 ℃ for 24 h to obtain the Bi2S3 / carbon nanotube composite material.

[0020] In this embodiment, the molar concentration of thiourea in solution A is 0.2 mol / L, and the molar concentration of bismuth nitrate pentahydrate in solution B is 0.1 mol / L. The mass ratio of the carbon nanotubes added in step 2) to the bismuth nitrate pentahydrate in solution B is 0.35:1.

[0021] Example 2 The preparation of the heterojunction photocatalytic material in this embodiment includes the following steps: 1) Preparation of carbon nanotube dispersion Weigh 3.0 g of carbon nanotubes and 1.0 g of cationic dispersant Hypermer KD2 (purchased from Croda Chemicals (Shanghai) Co., Ltd.), add 6 g of deionized water, and homogenize under high pressure at 1500 bar for 3 min to obtain a carbon nanotube dispersion with a mass concentration of 30%.

[0022] 2) Preparation of Bi2S3 / carbon nanotube heterojunction photocatalytic materials Weigh 0.46 g of thiourea and dissolve it in deionized water. Stir for 10 min until the solution is clear, then bring the volume to 30 mL. This solution is labeled as solution A. Dissolve 2.91 g of bismuth nitrate pentahydrate in 1 mol / L urea solution and stir vigorously. Bring the volume to 40 mL. This solution is labeled as solution B. Under vigorous stirring, add solution A dropwise to solution B. After the addition is complete, continue stirring for 30 min. Add 5.14 g of the carbon nanotubes prepared in step 1), stir well, and transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. Seal the reactor and place it in a 120 ℃ oven. Heat at 120 ℃ for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the mixture in the reactor, collect the precipitate, and wash the precipitate with deionized water. Repeat centrifugation and washing at least three times. Place the precipitate in an oven and dry at 80 ℃ for 24 h to obtain the Bi2S3 / carbon nanotube composite material.

[0023] In this embodiment, the molar concentration of thiourea in solution A is 0.2 mol / L, and the molar concentration of bismuth nitrate pentahydrate in solution B is 0.15 mol / L. The molar ratio of the carbon nanotubes added in step 2) to the bismuth nitrate pentahydrate in solution B is 1.77:1.

[0024] Example 3 The preparation of the heterojunction photocatalytic material in this embodiment includes the following steps: 1) Preparation of carbon nanotube dispersion Weigh 3.0 g of carbon nanotubes and 1.0 g of nonionic dispersant Dispers 755W (purchased from Evonik Specialty Chemicals (Shanghai) Co., Ltd.), add 6 g of deionized water, and homogenize under high pressure at 1500 bar for 3 min to obtain a carbon nanotube dispersion with a mass concentration of 30%.

[0025] 2) Preparation of Bi2S3 / carbon nanotube heterojunction photocatalytic materials Weigh 0.46 g of thiourea and dissolve it in deionized water. Stir for 10 min until the solution is clear, then bring the volume to 20 mL. This solution is labeled as solution A. Dissolve 2.91 g of bismuth nitrate pentahydrate in 1.5 mol / L urea solution and stir vigorously. Bring the volume to 40 mL. This solution is labeled as solution B. Under vigorous stirring, add solution A dropwise to solution B. After the addition is complete, continue stirring for 30 min. Add 7.71 g of the carbon nanotube dispersion prepared in step 1), stir until homogeneous, and then transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. Seal the reactor and place it in a 120 ℃ oven, heating at 120 ℃ for 12 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the mixture in the reactor, collect the precipitate, and wash the precipitate with deionized water. Repeat centrifugation and washing at least three times. Place the precipitate in an oven and dry at 80 ℃ for 24 h to obtain the Bi2S3 / carbon nanotube composite material.

[0026] In this embodiment, the molar concentration of thiourea in solution A is 0.3 mol / L, and the molar concentration of bismuth nitrate pentahydrate in solution B is 0.15 mol / L. The molar ratio of the carbon nanotubes added in step 2) to the bismuth nitrate pentahydrate in solution B is 2.65:1.

[0027] Those skilled in the art should note that the embodiments described in this invention are merely exemplary, and various other substitutions, changes, and improvements can be made within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is defined only by the claims.

Claims

1. A method for preparing a Bi₂S₃ / carbon nanotube heterojunction photocatalytic material, characterized in that, Includes the following steps: 1) Preparation of carbon nanotube dispersion Weigh out multi-walled carbon nanotubes and dispersant, add them to deionized water, and homogenize under high pressure at 1500 bar for 3 min to obtain carbon nanotube dispersion. 2) Preparation of Bi2S3 / carbon nanotube heterojunction photocatalytic materials Thiourea was dissolved in deionized water and stirred until the solution was clear; this solution was denoted as solution A. A soluble bismuth salt was dissolved in urea solution and stirred vigorously; this solution was denoted as solution B. Solution A was added dropwise to solution B while stirring vigorously, and stirring was continued for 30–60 minutes after the addition was complete. Add the carbon nanotube dispersion prepared in step 1), stir evenly, and transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene. After sealing, place it in an oven at 120–150 °C and heat for 12–15 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge the mixture in the reactor, collect the precipitate, and wash the precipitate with deionized water. Repeat the centrifugation and washing at least three times. Place the precipitate in an oven and dry it at 80–95 °C for 18–24 h to obtain the Bi2S3 / carbon nanotube heterojunction photocatalytic material.

2. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that, The dispersant is a cationic dispersant or a nonionic dispersant.

3. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that, The molar concentration of thiourea in solution A is 0.2–0.3 mol / L.

4. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that, The molar concentration of the urea solution is 1–1.5 mol / L.

5. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that... The soluble bismuth salt is bismuth nitrate pentahydrate.

6. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that, The molar concentration of bismuth nitrate pentahydrate in solution B is 0.1–0.15 mol / L.

7. The Bi₂S₃ / carbon nanotube heterojunction photocatalytic material according to claim 1, characterized in that, The mass ratio of the carbon nanotubes added in step 2) to the bismuth nitrate pentahydrate in solution B is 0.35 to 2.65:

1.

8. The Bi2S3 / carbon nanotube heterojunction photocatalytic material according to claims 1-6, used in the field of solar photocatalytic degradation of organic matter, has a wide absorption band and high degradation efficiency.