Full-spectrum response type photo-thermal-pyroelectric heterojunction composite photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a full-spectrum response type photo-thermal-pyroelectric heterojunction composite photocatalyst as well as a preparation method and application thereof. The chemical formula of the heterojunction composite photocatalyst is BiOBr / (Bi (Bi2S3) 9I3) 0.667. The heterojunction composite photocatalyst BiOBr / (Bi (Bi2S3) 9I3) 0.667 provided by the invention has full-spectrum responsiveness, namely wide-spectrum responsiveness, has photo-thermal catalysis and pyroelectric catalysis properties at the same time, and can effectively utilize sunlight. The heterojunction composite photocatalyst material is simple in preparation method, mild in reaction condition, low in cost and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field, and particularly to a full-spectrum response type photothermal-pyroelectric heterojunction composite photocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the aggravation of the global energy crisis and environmental pollution problems, the development of efficient and sustainable solar energy-driven technologies has become a research hotspot. Photocatalytic materials can utilize solar energy to achieve applications such as pollutant degradation, water splitting for hydrogen production, carbon dioxide reduction, and radioactive nuclide extraction, showing great potential in the fields of environmental remediation and clean energy. However, traditional photocatalysts generally have problems such as a narrow spectral response range (mainly relying on ultraviolet light), a high recombination rate of photo-generated carriers, and a low quantum efficiency, which seriously restrict their practical applications. Therefore, designing a new type of composite photocatalytic material with full-spectrum response, efficient carrier separation ability, and multi-functional synergistic effect has become a key direction to break through the existing technical bottlenecks.

[0003] Bismuth oxybromide (BiOBr), as a typical layered semiconductor material, exhibits excellent visible light responsiveness, high chemical stability, and adjustable band structure due to its unique alternating structure of [Bi2O2] layers and double halogen layers. Research shows that the degradation efficiency of BiOBr for organic pollutants (such as rhodamine B) under visible light can reach 93%, and its light absorption ability and specific surface area can be significantly improved through morphology regulation (such as porous nanosheets) or composite modification (such as combination with carbon nanotubes and metallic Bi). However, BiOBr still has the following defects: (1) It has a relatively wide bandgap (about 2.69 eV) and no response to infrared light, resulting in insufficient utilization of solar energy; (2) The recombination rate of photo-generated carriers is fast, and it is necessary to rely on sacrificial agents or heterojunction design to improve the charge separation efficiency; (3) A single photocatalytic mechanism is difficult to meet the requirements of multi-functional synergistic effects in complex environmental applications, such as the coupling of photothermal conversion and pyroelectric effect. Summary of the Invention

[0004] The present invention aims to solve at least one of the above technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a full-spectrum response type photothermal-pyroelectric heterojunction composite photocatalyst, a preparation method thereof, and an application thereof.

[0005] In order to achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] In the first aspect of the present invention, a heterojunction composite photocatalyst is provided, and its chemical formula is BiOBr / (Bi(Bi2S3)9I3) 0.667 .

[0007] In the present invention, (Bi(Bi2S3)9I3) 0.667As a narrow-bandgap pyroelectric semiconductor, the material has the ability to respond to light in the entire visible light region, which can complement the visible light response of BiOBr to achieve the full-range utilization of the solar spectrum. In addition, (Bi(Bi2S3)9I3) 0.667 The high photothermal conversion ability of the material can convert the absorbed light energy into heat energy, increase the local temperature, and then trigger the pyroelectric effect, generating a spontaneous polarization electric field at the heterojunction interface, driving the directional migration of carriers and suppressing recombination, so that the heterojunction composite photocatalyst BiOBr / (Bi(Bi2S3)9I3) 0.667 exhibits the synergistic effect of the photothermal-pyroelectric effect and the heterojunction interface engineering.

[0008] In some embodiments of the present invention, the molar ratio of S element to Bi element in the BiOBr / (Bi(Bi2S3)9I3) 0.667 is (0.1 - 3):1.

[0009] The second aspect of the present invention provides a method for preparing the heterojunction composite photocatalyst as described above, comprising the following steps:

[0010] Dissolve BiOBr, iodine source, and sulfur source in water according to a ratio, and carry out a hydrothermal reaction to obtain the heterojunction composite photocatalyst.

[0011] In some embodiments of the present invention, the molar ratio of sulfur element in the sulfur source to Bi element in BiOBr is (0.1 - 3):1.

[0012] In some embodiments of the present invention, the molar ratio of sulfur element in the sulfur source to iodine element in the iodine source is 1:(3 - 5), such as 1:4.

[0013] In some embodiments of the present invention, the iodine source includes at least one of sodium iodide and potassium iodide; the concentration of the iodine source is 0.5 - 1M.

[0014] In some embodiments of the present invention, the sulfur source includes at least one of sodium sulfide, sodium thiosulfate, and thiourea; the concentration of the sulfur source is 0.5 - 1M.

[0015] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 120°C - 180°C; the time of the hydrothermal reaction is 12 - 36h.

[0016] In some embodiments of the present invention, the BiOBr can be a commercially available product or prepared according to the disclosed related technologies; it can also be prepared according to the following method of the present invention:

[0017] The preparation method of the BiOBr comprises the following steps: dissolving a bismuth source in a mannitol solvent, adding an aqueous solution containing a bromine source, and performing a hydrothermal reaction to obtain BiOBr; preferably, the temperature of the hydrothermal reaction is 120°C to 180°C; the time of the hydrothermal reaction is 12 to 36 h.

[0018] In some embodiments of the present invention, the ratio of the mass of the bismuth source to the volume of the mannitol solvent is 1 to 3:20 to 40 g / mL.

[0019] In some embodiments of the present invention, the concentration of the bromine source in the aqueous solution containing the bromine source is 0.5 to 1 M.

[0020] In some embodiments of the present invention, the bismuth source includes at least one of bismuth nitrate pentahydrate, bismuth carbonate, bismuth phosphate, bismuth sulfate, and bismuth trioxide.

[0021] In some embodiments of the present invention, the bromine source includes at least one of sodium bromide, potassium bromide, calcium bromide, and cetyltrimethylammonium bromide.

[0022] In a third aspect of the present invention, there is provided an application of the heterojunction composite photocatalyst as described above in degrading at least one of organic dyes, antibiotics, and heavy metal pollutants.

[0023] The heterojunction composite photocatalyst BiOBr / (Bi(Bi2S3)9I3) in the present invention 0.667 has a high-efficiency catalytic reduction effect on pollutants such as Cr(VI), and has a high separation efficiency of photogenerated carriers, can effectively utilize near-infrared light, and has a high catalytic efficiency.

[0024] The beneficial effects of the present invention are:

[0025] The heterojunction composite photocatalyst BiOBr / (Bi(Bi2S3)9I3) of the present invention 0.667 has full-spectrum responsiveness, that is, a wide-spectrum response ability, and at the same time has photothermal catalytic and pyroelectric catalytic properties, and can effectively utilize sunlight.

[0026] The heterojunction composite photocatalyst BiOBr / (Bi(Bi2S3)9I3) in the present invention 0.667 has a high-efficiency catalytic reduction effect on pollutants such as Cr(VI), and has a high separation efficiency of photogenerated carriers, can effectively utilize near-infrared light, and has a high catalytic efficiency.

[0027] The preparation method of the heterojunction composite photocatalyst material of the present invention is simple, the reaction conditions are mild, the cost is low, and it is suitable for large-scale production. Description of the Drawings

[0028] Figure 1The X-ray diffraction patterns of the photocatalytic materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 are shown.

[0029] Figure 2 The performance curve of the full-spectrum photocatalytic degradation of Cr(VI) by the photocatalytic materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 is shown.

[0030] Figure 3 The UV-Vis-Infrared absorption spectra of the photocatalytic materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 are shown.

[0031] Figure 4 The performance curve of the temperature-variable pyroelectric catalytic degradation of Cr(VI) by the photocatalytic materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2 is shown. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0033] Example 1

[0034] This example prepares a full-spectrum responsive photothermal-pyroelectric heterojunction composite photocatalyst, and the specific process is as follows:

[0035] (1) 1-5 mmol of bismuth nitrate pentahydrate is added to 30 mL of an aqueous solution (0.1 M) of mannitol, and after stirring until the solution is transparent, 0.4-2 mL of a 2.5 M potassium bromide solution is added, and after sufficient stirring, a mixed solution is obtained. The mixed solution is transferred to a polytetrafluoroethylene reactor, and a hydrothermal reaction is carried out at 160° C. for 12 hours. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain a precipitate.

[0036] (2) The precipitate obtained in step (1) is washed by centrifugation with deionized water and ethanol respectively, and then dried at 70° C. to obtain a BiOBr precursor.

[0037] (3) 2 mmol BiOBr was added to 30 mL deionized water and dispersed evenly. Then, NaI, Na2S2O3 and BiOBr were added to the BiOBr dispersion at a mass ratio of 1:4:2. After sufficient stirring, the mixture was transferred to a polytetrafluoroethylene reactor and subjected to a hydrothermal reaction at 140° C. for 24 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a precipitate.

[0038] (4) The precipitate obtained in step (3) was washed by centrifugation with deionized water and ethanol respectively, and then dried at 70° C. to obtain BiOBr / (Bi(Bi2S3)9I3)0.667 Heterojunction photocatalyst, labeled B-1BSI.

[0039] Example 2

[0040] In this example, a full-spectrum responsive photothermal-pyroelectric heterojunction composite photocatalyst was prepared. The specific process is as follows:

[0041] (1) Add 1 - 5 mmol of bismuth nitrate pentahydrate to 30 mL of an aqueous solution of mannitol (0.1 M). After stirring until the solution becomes transparent, add 0.4 - 2 mL of a 2.5 M potassium bromide solution. After thorough stirring, a mixed solution is obtained. Transfer the mixed solution to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 160 °C for 12 hours. After the reaction is completed, naturally cool it to room temperature to obtain a precipitate.

[0042] (2) The precipitate obtained in step (1) is centrifugally washed with deionized water and ethanol respectively, and then dried at 70 °C to obtain the BiOBr precursor.

[0043] (3) Disperse 2 mmol of BiOBr evenly in 30 mL of deionized water. Then, add NaI and Na2S2O3 to the BiOBr dispersion in a molar ratio of 1:4:1 with BiOBr. After thorough stirring, transfer it to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 140 °C for 24 hours. After the reaction is completed, naturally cool it to room temperature to obtain a precipitate.

[0044] (4) The precipitate obtained in step (3) is centrifugally washed with deionized water and ethanol respectively, and then dried at 70 °C to obtain BiOBr / (Bi(Bi2S3)9I3) 0.667 Heterojunction photocatalyst, labeled B-2BSI.

[0045] Example 3

[0046] In this example, a full-spectrum responsive photothermal-pyroelectric heterojunction composite photocatalyst was prepared. The specific process is as follows:

[0047] (1) Add 1 - 5 mmol of bismuth nitrate pentahydrate to 30 mL of an aqueous solution of mannitol (0.1 M). After stirring until the solution becomes transparent, add 0.4 - 2 mL of a 2.5 M potassium bromide solution. After thorough stirring, a mixed solution is obtained. Transfer the mixed solution to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 160 °C for 12 hours. After the reaction is completed, naturally cool it to room temperature to obtain a precipitate.

[0048] (2) The precipitate obtained in step (1) is centrifugally washed with deionized water and ethanol respectively, and then dried at 70 °C to obtain the BiOBr precursor.

[0049] (3) Add 2 mmol of BiOBr to 30 mL of deionized water and disperse it evenly. Then, add NaI and Na2S2O3 to the BiOBr dispersion in a molar ratio of 3:12:2. After stirring well, transfer the mixture to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 140 °C for 24 hours. After the reaction is completed, cool it naturally to room temperature to obtain a precipitate.

[0050] (4) Centrifuge and wash the precipitate obtained in step (3) with deionized water and ethanol respectively, and then dry it at 70 °C to obtain the BiOBr / (Bi(Bi2S3)9I3) 0.667 heterojunction photocatalyst, labeled as B-3BSI.

[0051] Comparative Example 1

[0052] In this comparative example, a BiOBr photocatalyst was prepared. The specific process was as follows:

[0053] (1) Add 1 - 5 mmol of bismuth nitrate pentahydrate to 30 mL of an aqueous solution of mannitol (0.1 M). After stirring until the solution becomes transparent, add 0.4 - 2 mL of a 2.5 M sodium bromide solution. After stirring well, a mixed solution is obtained. Transfer the mixed solution to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 160 °C for 12 hours. After the reaction is completed, cool it naturally to room temperature to obtain a precipitate.

[0054] (2) Centrifuge and wash the precipitate obtained in step (1) with deionized water and ethanol respectively, and then dry it at 70 °C to obtain the BiOBr photocatalytic material.

[0055] Comparative Example 2

[0056] In this comparative example, a (Bi(Bi2S3)9I3) 0.667 photocatalyst was prepared. The specific process was as follows:

[0057] (1) Add 1 - 5 mmol of bismuth nitrate to 30 mL of ethylene glycol. After stirring evenly, add 1 - 5 mol of thiourea and stir for 15 min. Finally, add 4 - 20 mmol of potassium iodide to the solution and stir for 30 min. Transfer the mixed solution to a polytetrafluoroethylene reaction kettle and carry out a hydrothermal reaction at 160 °C for 24 hours. After the reaction is completed, cool it naturally to room temperature to obtain a precipitate.

[0058] (2) Centrifuge and wash the precipitate obtained in step (1) with deionized water and ethanol respectively, and then dry it at 70 °C to obtain the (Bi(Bi2S3)9I3) 0.667 photocatalytic material.

[0059] Application Example

[0060] This application example conducts photocatalytic activity tests. The specific process is as follows:

[0061] The photocatalytic activity of the sample for the degradation of Cr(VI) was evaluated under a 300W xenon lamp (CEL-LAX500). The reactor used was a quartz reactor with a volume of 100 mL. 20 mg of the sample was added to a potassium dichromate solution (40 mL, 10 mg / L), and it was stirred in the dark for 2 hours to ensure absorption-desorption equilibrium. 4 mL of the reaction solution was taken out regularly. After the supernatant was subjected to a DCP color reaction, it was analyzed using a UV-1800 spectrophotometer. The variable-temperature pyroelectric catalysis was carried out under the temperature control of a circulating water constant temperature bath. 4 mL of the reaction solution was taken for detection every 6 cycles. The temperature was controlled to rise from the normal temperature of 20 °C to 55 °C and then held for 5 min, and then cold water was switched to lower the reaction environment temperature to 20 °C and held for 5 min as one cycle. The variable-temperature rate was controlled at 50 °C / min.

[0062] The results are as Figures 1 to 4 shown. It can be Figure 1 seen that the photocatalysts prepared in the examples and comparative examples both correspond to the characteristic peaks of standard BiOBr and (Bi(Bi2S3)9I3) 0.667 without impurity peaks, indicating high purity in sample preparation. It can be Figure 2 seen that the photocatalytic activities of Examples 1-3 are all higher than those of the comparative example, and the activity of Example 2 is the highest, with the removal rate of Cr(VI) reaching 100% within 30 min. It can be Figure 3 seen that the absorption spectra of Examples 1-3 are all broadened to the infrared region. Combining with Figure 4 the variable-temperature cycle catalysis results, it can be known that the prepared BiOBr / (Bi(Bi2S3)9I3) 0.667 heterojunction photocatalyst can achieve a degradation rate of 60% for Cr(VI) after 24 cycles under the condition of changing the environmental temperature (20-55 °C) without light irradiation, showing strong pyroelectric catalytic performance.

[0063] In summary, the full-spectrum response type BiOBr / (Bi(Bi2S3)9I3) 0.667 photo-thermal - pyroelectric heterojunction composite photocatalyst provided by the present invention can fully adapt to different catalytic conditions, and under the synergistic effect of the pyroelectric effect, it shows strong catalytic performance.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A heterojunction composite photocatalyst, characterized in that: Its chemical formula is BiOBr / (Bi(Bi2S3)9I3) 0.667 .

2. The heterojunction composite photocatalyst according to claim 1, characterized in that: The BiOBr / (Bi(Bi2S3)9I3) 0.667 The molar ratio of S element to Bi element is (0.1~3):

1.

3. A method for preparing the heterojunction composite photocatalyst according to claim 1 or 2, characterized in that: The following steps are involved: BiOBr, an iodine source and a sulfur source are dissolved in water in proportion, and a hydrothermal reaction is carried out to prepare the heterojunction composite photocatalyst.

4. The method for preparing a heterojunction composite photocatalyst according to claim 3, characterized in that: The molar ratio of sulfur element in the sulfur source to iodine element in the iodine source is 1:(3-5).

5. The method for preparing a heterojunction composite photocatalyst according to claim 3, characterized in that: The sulfur source includes at least one of sodium sulfide, sodium thiosulfate and thiourea; and / or the concentration of the sulfur source is 0.5-1M.

6. The method for preparing a heterojunction composite photocatalyst according to claim 3, characterized in that: The preparation method of BiOBr comprises the following steps: dissolving a bismuth source in a mannitol solvent, adding an aqueous solution containing a bromine source, and performing a hydrothermal reaction to obtain BiOBr.

7. The method for preparing a heterojunction composite photocatalyst according to claim 6, characterized in that: The ratio of the mass of the bismuth source to the volume of the mannitol solvent is 1-3:20-40 g / mL.

8. The method for preparing a heterojunction composite photocatalyst according to claim 6, characterized in that: The bismuth source includes at least one of bismuth nitrate pentahydrate, bismuth carbonate, bismuth phosphate, bismuth sulfate and bismuth trioxide; and / or, the bromine source includes at least one of sodium bromide, potassium bromide, calcium bromide and hexadecyltrimethylammonium bromide.

9. The method for preparing a heterojunction composite photocatalyst according to claim 3 or 6, characterized in that: The temperature of the hydrothermal reaction is 120° C. to 180° C.; and / or the time of the hydrothermal reaction is 12 to 36 hours.

10. Use of the heterojunction composite photocatalyst according to claim 1 or 2 in degrading at least one of organic dyes, antibiotics, and heavy metal pollutants.

Images