A double-z type heterojunction composite catalyst and a preparation method and application thereof

Abstract

The application discloses a double-Z type heterojunction composite catalyst and a preparation method and application thereof, and belongs to the technical field of nanocomposites and photocatalysis. In the application, TiO2 nanorods and Bi2WO6 nanoparticles are deposited on the surface of Bi2O2CO3 nanosheets, forming a catalyst with Bi2WO6 / Bi2O2CO3 Z-type heterojunction and TiO2 / Bi2O2CO3 Z-type heterojunction, wherein the (110) crystal surface of Bi2O2CO3, the (101) crystal surface of TiO2 and the (131) crystal surface of Bi2WO6 are in close contact with each other in pairs. The catalyst of the application shows excellent catalytic performance in the photocatalytic degradation of tetracycline. The application constructs a Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double-Z type heterojunction composite catalyst system, utilizes the mutual cooperation of the heterojunction interface, promotes the separation and transmission of photo-generated electrons and holes, and realizes the efficient photocatalytic degradation of tetracycline.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials and photocatalysis technology, specifically relating to a double Z-type heterojunction composite catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, various antibiotics have been frequently detected in rivers and lakes across the country. Therefore, there is an urgent need to develop new technologies for treating polluted water bodies in order to control pollution sources and reduce the concentration of antibiotic pollution in water bodies.

[0003] Photocatalysts can absorb light to be excited and participate in various reactions, and their physicochemical properties remain unchanged after the reaction. Since these reactions only require light energy as an energy source and do not require other types of energy input, if stable sunlight-driven photocatalytic reactions can be achieved, this technology is expected to become a key technology for low-cost and green sustainable development.

[0004] Bi₂O₂CO₃, as a typical layered Bi-based semiconductor material, is considered an excellent semiconductor photocatalyst due to its chemical stability and unique chemical properties. However, the low separation efficiency of photogenerated electrons and holes in traditional Bi₂O₂CO₃ photocatalysts limits the practical application of photocatalysis. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a double Z-type heterojunction composite catalyst, its preparation method and application, which improves the separation efficiency of photogenerated electrons and holes.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst, wherein TiO2 nanorods and Bi2WO6 nanoparticles are deposited on Bi2O2CO3 nanosheets to form a catalyst having a Bi2WO6 / Bi2O2CO3 Z-type heterojunction and a TiO2 / Bi2O2CO3 Z-type heterojunction, wherein the (110) crystal plane of Bi2O2CO3, the (101) crystal plane of TiO2 and the (131) crystal plane of Bi2WO6 are in close contact with each other.

[0008] Furthermore, in the above technical solution, the size of the TiO2 nanorods is 70.9-102.5 nm, the size of the Bi2O2CO3 nanosheets is 184.1-545.7 nm, and the size of the Bi2WO6 nanoparticles is 6.7-12.6 nm.

[0009] Furthermore, in the above technical solution, the molar ratio of Bi2O2CO3, TiO2 and Bi2WO6 is 1-2:2-4:1-2.

[0010] Secondly, the present invention provides a Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst and its preparation method, comprising the following steps:

[0011] Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts were synthesized by a one-step hydrothermal method using potassium titanate nanowires as precursors in urea solution, specifically urea aqueous solution, with the addition of bismuth nitrate and copper nitrate.

[0012] In this process, bismuth nitrate nucleates and grows in the urea solution to form Bi2O2CO3 nanosheets, potassium titanate nanowires grow in situ to form TiO2 nanorods and are deposited on the Bi2O2CO3 nanosheets, while sodium tungstate and bismuth nitrate generate Bi2WO6 nanoparticles in an alkaline environment and are deposited on the Bi2O2CO3 nanosheets, forming a double Z-type heterojunction composite catalyst.

[0013] Furthermore, the above technical solution specifically includes the following steps:

[0014] (1) The precursor is mixed with the urea solution and then ultrasonicated to obtain the precursor solution;

[0015] (2) Add Bi(NO3)3·5H2O and Na2WO4·2H2O to the precursor solution, stir evenly, and react at 180-220℃ for 14-18h. After washing with water, centrifuging and drying, the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts are obtained.

[0016] Furthermore, in the above technical solution, the preparation method of the potassium titanate nanowire precursor includes the following steps:

[0017] At room temperature, P25 (abbreviation for titanium dioxide P25) is mixed evenly with potassium hydroxide aqueous solution and reacted at 190-210℃ for 22-26 hours. The solid in the product is separated, washed with water until neutral, and dried to obtain the final product.

[0018] Furthermore, in the above technical solution, the molar ratio of the precursor, Bi(NO3)3·5H2O and Na2WO4·2H2O is 2-4:0.5-1.5:3-5.

[0019] Thirdly, the present invention provides an application of the above-described composite catalyst or the composite catalyst prepared by the described preparation method in the photocatalytic degradation of tetracycline.

[0020] Beneficial effects:

[0021] This invention uses potassium titanate nanowires as a precursor and employs a one-step hydrothermal method to rationally construct Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-shaped heterojunction composite catalysts. Bi2WO6 nanoparticles are grown on Bi2O2CO3, while TiO2 titanium nanorods are grown on Bi2O2CO3. The Bi2O2CO3 (110) crystal plane, TiO2 (101) and Bi2WO6 (131) crystal planes are in close contact, forming a double Z-shaped heterojunction interface.

[0022] The Bi₂WO₆ / Bi₂O₂CO₃ and TiO₂ / Bi₂O₂CO₃ dual Z-junction composite catalysts exhibited enhanced photocatalytic activity in the photocatalytic degradation of tetracycline, achieving 75% degradation of tetracycline after 1.5 h of illumination. This result indicates that the coupling between Bi₂WO₆ and Bi₂O₂CO₃, and between TiO₂ and Bi₂O₂CO₃, can induce the transfer of photogenerated electrons and holes among the three semiconductors, thereby improving the separation efficiency of photogenerated electrons and holes, achieving highly efficient photocatalytic degradation of tetracycline, and enhancing the catalytic reaction performance. Attached Figure Description

[0023] Figure 1 XRD characterization diagrams of Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts.

[0024] Figure 2 The images show electron microscopy (TEM) characterizations of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts. In the figures, a is a TEM image of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts, and b is a lattice spacing diagram of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts.

[0025] Figure 3 The figures show the photocatalytic degradation performance of tetracycline by Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts; figure a is the photocatalytic activity of Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts, figure b is the reaction constant K value of Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts, and figure c is the cycle stability. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: Preparation of Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts

[0028] At room temperature, 1 g of P25 was added to a 10 M potassium hydroxide solution and mixed thoroughly. The mixture was kept at 200 °C for 24 h and then allowed to cool naturally to room temperature. The resulting product was centrifuged and filtered, and the precipitate was washed with water until the pH was approximately 7. The product was then centrifuged and dried to obtain the potassium titanate nanowire precursor.

[0029] 30 mL of deionized water was added to a 50 mL polytetrafluoroethylene reactor, along with 0.05 g of potassium titanate nanowire precursor. After stirring for 10 min, 2.4 g of urea was added, and the mixture was sonicated for 30 min. Subsequently, 0.337 g of Bi(NO3)3·5H2O and 0.057 g of Na2WO4·2H2O were added under stirring. After stirring for 10 min, the reactor was sealed and kept at 200 °C for 16 h. After cooling to room temperature, the reactor was washed with water, centrifuged, and dried at 80 °C for 12 h to obtain Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts.

[0030] The potassium hydroxide used in this invention is analytical grade with a purity ≥96.0%, the urea is analytical grade with a purity ≥99%, the copper nitrate trihydrate is analytical grade with a purity ≥99.0%, and the bismuth nitrate pentahydrate is analytical grade with a purity ≥99%.

[0031] The XRD patterns of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts prepared in this invention are shown in the figure. Figure 1 As shown, the synthesized double Z-type heterojunction composite catalyst exhibits diffraction peaks corresponding to those of single-phase bismuth tungstate and bismuth oxycarbonate samples, but no diffraction peaks of titanium dioxide rods are observed in the TEM. However, the presence of titanium dioxide rods can be observed.

[0032] Figure 2 Morphological characterization of Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts is presented, from... Figure 2In diagram a, we can clearly see many Bi2WO6 and TiO2 nanorods growing on the Bi2O2CO3 nanosheets. Figure 2 b indicates that the crystal planes of Bi2O2CO3(110), TiO2(101) and Bi2WO6(131) are in close contact, effectively forming a double Z-type heterostructure interface.

[0033] Example 2: Photocatalytic degradation of tetracycline

[0034] The photocatalytic degradation of tetracycline using the catalyst prepared in Example 1

[0035] Photocatalytic degradation of tetracycline was carried out in a specially designed quartz reactor. 20 mg·L⁻¹ -1 Tetracycline was used as a reactant, and the reaction was carried out under circulating water cooling. 20 mg of the catalyst prepared in Example 1 was added, and the mixture was stirred in the dark for 30 min. After that, the light source was turned on, and 3 mL of solution was taken out every 10 minutes and measured with a UV-Vis spectrophotometer. For the cycle stability experiment, the catalyst after the photocatalytic reaction was centrifuged, washed with ethanol, and dried at 60 °C before the next experiment.

[0036] from Figure 3 As can be seen, the photocatalytic degradation rate of the synthesized catalyst gradually increases with increasing reaction time. The composite catalyst exhibits enhanced reactivity; after 1.5 hours of reaction, the degradation rate of tetracycline can reach 75%. Figure 3 As can be seen from b, after 1.5 hours of reaction, the reaction K value of the composite catalyst can reach 0.02346. Figure 3 c indicates that the carbon composite catalyst has excellent reaction stability; after four reaction cycles, the activity did not decrease significantly.

[0037] By constructing heterojunctions between semiconductors, not only can the defects of individual semiconductors be compensated, which is beneficial for preparing advanced catalysts for target reactions, but also a deeper understanding of the structure-activity relationship between catalyst structure and reaction performance can be achieved. This invention prepares potassium titanate nanowires via a one-step hydrothermal method, and further synthesizes a ternary heterojunction composite catalyst of bismuth oxycarbonate, titanium dioxide, and bismuth tungstate via hydrothermal synthesis. The synergistic effect of the heterojunction interface achieves maximum separation of photogenerated electrons and holes, further enhancing the photocatalytic degradation activity of tetracycline under illumination.

[0038] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A Bi₂WO₆ / Bi₂O₂CO₃ and TiO₂ / Bi₂O₂CO₃ dual Z-type heterojunction composite catalyst, characterized in that, TiO2 nanorods and Bi2WO6 nanoparticles are deposited on the surface of Bi2O2CO3 nanosheets to form a catalyst with a Z-shaped heterojunction of Bi2WO6 / Bi2O2CO3 and a Z-shaped heterojunction of TiO2 / Bi2O2CO3. In the catalyst, the (110) crystal plane of Bi2O2CO3, the (101) crystal plane of TiO2 and the (131) crystal plane of Bi2WO6 are in close contact with each other. The TiO2 nanorods have a size of 70.9-102.5 nm, the Bi2O2CO3 nanosheets have a size of 184.1-545.7 nm, and the Bi2WO6 nanoparticles have a size of 6.7-12.6 nm. The molar ratio of Bi2O2CO3, TiO2, and Bi2WO6 is 1-2 : 2-4 : 1-2.

2. A method for preparing the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst according to claim 1, characterized in that, Includes the following steps: Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts were synthesized in a one-step hydrothermal method by adding bismuth nitrate and sodium tungstate to urea solution using potassium titanate nanowires as precursors. In this process, bismuth nitrate nucleates and grows in the urea solution to form Bi2O2CO3 nanosheets, potassium titanate nanowires grow in situ to form TiO2 nanorods and are deposited on the Bi2O2CO3 nanosheets, while sodium tungstate and bismuth nitrate generate Bi2WO6 nanoparticles in an alkaline environment and deposit them on the Bi2O2CO3 nanosheets, forming the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalysts.

3. The preparation method of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst according to claim 2, characterized in that, Specifically, the steps include the following: (1) The precursor is mixed with the urea solution and then sonicated to obtain a precursor solution; (2) Add Bi(NO3)3·5H2O and Na2WO4·2H2O to the precursor solution, stir evenly, react at 180-220 °C for 14-18 h, wash with water, centrifuge and dry to obtain the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst; The molar ratio of the precursor, Bi(NO3)3·5H2O and Na2WO4·2H2O is 2-4:0.5-1.5:3-5.

4. The preparation method of the Bi2WO6 / Bi2O2CO3 and TiO2 / Bi2O2CO3 double Z-type heterojunction composite catalyst according to claim 3, characterized in that, The method for preparing the precursor includes the following steps: At room temperature, P25 is mixed evenly with potassium hydroxide aqueous solution and reacted at 190-210 °C for 22-26 h. The solid in the product is separated, washed with water until neutral, and dried to obtain the final product.

5. The application of the composite catalyst according to claim 1 or the composite catalyst prepared by any one of claims 2-4 in the photocatalytic degradation of tetracycline.

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