2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst and preparation method and application thereof

Abstract

The application discloses a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst and a preparation method and application thereof, and belongs to the technical field of photocatalysis. First, Bi3TiNbO9 powder is prepared; then, Bi(NO3)3.5H2O is dissolved in deionized water containing glacial acetic acid, the Bi3TiNbO9 powder is added, KBr solution is added after uniform stirring, hydrothermal reaction is carried out again after uniform stirring, and the reaction product is washed and dried after cooling to obtain the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst. The face-to-face contact formed by 2D / 2D can provide more carrier transfer channels, has more reactive sites, has high photo-generated carrier separation efficiency, and has excellent photocatalytic degradation performance on antibiotics. The application has the advantages of simple preparation process, low reaction temperature, short reaction time, low material cost, and suitability for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photocatalysis, and particularly relates to a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst as well as a preparation method and application thereof. BACKGROUND

[0002] In 1972, Honda and Fujishima found that a photoelectrochemical system composed of TiO2 and Pt electrodes can decompose water into hydrogen and oxygen under sunlight irradiation. Since then, Frank and Kenji et al. found that semiconductor photocatalytic materials can degrade cyanide and organic pollutants under light irradiation. Since then, photocatalytic technology has attracted more and more scholars to use environmentally friendly and easily collected solar energy to solve environmental pollution problems because it can efficiently degrade pollutants in water without consuming a large amount of energy. Therefore, photocatalytic technology is considered as a promising green technology for successful utilization of solar energy. Despite its wide application prospects, the large-scale industrial application of photocatalytic technology still faces great challenges, and the low solar energy conversion efficiency is a key factor restricting the practical application of photocatalytic technology.

[0003] In recent years, ferroelectric materials have attracted more and more attention of researchers because the internal spontaneous polarization field of the ferroelectric materials can effectively drive the separation of photo-generated charges, inhibit the recombination of photo-generated charges, and improve the photocatalytic efficiency (Li Y, Li J, Yang W, et al. Implementation of ferroelectric materials in photocatalytic and photoelectrochemical water splitting [J]. Nanoscale Horizons, 2020, 5(8): 1174-1187.). Among them, the ferroelectric Bi3TiNbO9 crystal is successfully used as a photocatalyst to degrade pollutants, split water and reduce carbon dioxide because of its typical ferroelectric properties. However, its band gap is relatively large, and it can only absorb ultraviolet light, which cannot fully utilize the visible light in the solar spectrum, and the internal separation efficiency of photo-generated carriers needs to be further improved. At present, Cui et al. adjusted the crystal face exposure rate in the ferroelectric Bi3Ti x Nb 2-x O9 single crystal nanosheet through self-doping strategy, thereby optimizing the {001} and {110} face junction effect, and effectively promoting the separation of carriers (Cui Y, Guo P, Wang F, et al. Self-Doping Based Facet Junctions and Oxygen Vacancies in Ferroelectric Bi3Ti x Nb 2–xO9 Nanosheets for Boosting Photocatalytic Degradation and Antibacterial Activity[J].ACS Applied Materials & Interfaces, 2022, 14(46): 51819–51834.). Literature reports on Bi3TiNbO9 focus on its doping modification (Jiang L, Ni S, Liu G, et al. Photocatalytic hydrogen production over Aurivillius compound Bi3TiNbO9 and its modifications by Cr / Nb co-doping[J]. Applied Catalysis B: Environmental, 2017, 217: 342–352. and Cui Y, Guo P, Dang P, et al. Improved photodegradation efficiency in Fe 3+ -Doped Bi3TiNbO9 nanosheets through oxygen vacancies introduction and ferroelectric polarization enhancement simultaneously[J].Applied Surface Science,2022,575:151749.), can effectively improve photocatalytic performance, but its catalytic performance still needs further exploration.

[0004] Given the existing problems of Bi3TiNbO9, such as its large band gap, which allows it to absorb only ultraviolet light and cannot fully utilize visible light in the solar energy spectrum, as well as its low separation efficiency of photogenerated carriers, there is an urgent need to conduct modification research to improve its photocatalytic performance. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a 2D / 2DBiOBr / Bi3TiNbO9 heterojunction photocatalyst, its preparation method and application, so as to solve the technical problems of the existing Bi3TiNbO9 having a large band gap, only absorbing ultraviolet light and unable to fully utilize the visible light in the solar energy spectrum, as well as the low separation efficiency of its internal photogenerated carriers and the limited catalytic performance of BiOBr.

[0006] In order to achieve the above object, the present application adopts the following technical solutions to achieve the above object:

[0007] The application discloses a preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0008] Preferably, the molar ratio of Bi(NO3)3.5H2O to Bi3TiNbO9 powder is (2-8):1.

[0009] Preferably, the KBr solution is prepared by dissolving KBr in deionized water, and the concentration is 16.7-66.7 mmol / L. -1 The molar ratio of Bi(NO3)3.5H2O to KBr is (0.98-1.02):(0.98-1.02).

[0010] Preferably, the concentration of the glacial acetic acid solution is 3.48-3.52 mol / L.

[0011] Preferably, the temperature of the hydrothermal reaction is 115-125 DEG C.

[0012] Preferably, the time of the hydrothermal reaction is 5.5-6.5 h.

[0013] Preferably, the Bi3TiNbO9 powder is prepared by a molten salt method, and the preparation method comprises the following steps: mixing NaCl, KCl and Bi3TiNbO9 precursor according to a molar ratio of (49.8-50.2):(49.8-50.2):(0.98-1.02), ball milling for 3.5-4.5 h, drying for 11.5-12.5 h, calcining at 798-802 DEG C for 1.98-2.02 h, washing until no Cl - is detected in the supernatant, and drying to obtain the Bi3TiNbO9 powder.

[0014] Preferably, the Bi3TiNbO9 precursor is prepared by mixing Bi2O3, TiO2 and Nb2O5 according to a mass ratio of (1.397-1.399):(0.159-0.161):(0.265-0.267).

[0015] The application further discloses the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst prepared by the preparation method.

[0016] The application further discloses application of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst in degrading antibiotics.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The application discloses a preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0019] The application further discloses the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst prepared by the preparation method, wherein the unique 2D / 2D heterojunction structure can bring more effective physical contact and enhanced charge transfer rate, and thus the photocatalyst has significantly enhanced photocatalytic performance.

[0020] The application further discloses application of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst in degrading antibiotics, wherein the TC degradation percentage of Bi3TiNbO9 / 3BiOBr is close to 63% under 60 min light irradiation, the degradation rate is 5.6 times that of Bi3TiNbO9 and 1.4 times that of pure BiOBr, and the heterojunction photocatalytic performance is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1XRD patterns of the heterojunction photocatalysts prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr;

[0022] Figure 2 UV-diffuse reflectance absorption spectra of the heterojunction photocatalysts prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr;

[0023] Figure 3 SEM images of the heterojunction photocatalysts prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr;

[0024] Figure 4 Tetracycline hydrochloride degradation curves of the heterojunction photocatalysts prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr;

[0025] Figure 5 is the linear fitting of the photodegradation rate of the heterojunction photocatalyst prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in embodiments 1-4 and comparative examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr;

[0026] Figure 6 is a schematic diagram of the photocatalytic mechanism of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst disclosed in the present application. DETAILED DESCRIPTION

[0027] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] The present application will be described in further detail below in conjunction with the drawings:

[0030] A preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, comprising the following steps:

[0031] 1) Bi3TiNbO9 is prepared by a molten salt method: 1.397-1.399 g of Bi2O3, 0.159-0.161 g of TiO2 and 0.265-0.267 g of Nb2O5 are mixed in proper stoichiometric ratios according to the composition of Bi3TiNbO9 to obtain a Bi3TiNbO9 precursor; then NaCl and KCl as a eutectic agent are mixed with the Bi3TiNbO9 precursor in a molar ratio of (49.8-50.2):(49.8-50.2):(0.98-1.02); the mixture is ball-milled in anhydrous ethanol for 3.5-4.5 h, dried in a drying oven at 45-55 °C for 11.5-12.5 h, and calcined at 798-802 °C for 1.98-2.02 h, and then the powder is washed with hot deionized water until no Cl is detected in the supernatant - ; finally, the sample is dried at 45-55 °C for 11.5-12.5 h to obtain Bi3TiNbO9 powder;

[0032] 2) Bi(NO3)3·5H2O is dissolved in 30 mL of deionized water containing 6 mL of glacial acetic acid, 0.2269-0.2289 g of Bi3TiNbO9 powder obtained in step 1) is added, and 29-31 mL of KBr solution is added at a constant speed after stirring, so that the molar ratio of Bi(NO3)3·5H2O and KBr is (0.98-1.02):(0.98-1.02), and the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9 is (2-8):1, to obtain a series of heterojunction photocatalysts with different BiOBr mass fractions; after stirring again, hydrothermal reaction is carried out, the mixture is transferred to a 100 mL polytetrafluoroethylene-lined reaction kettle, and hydrothermal reaction is carried out at 115-125 °C for 5.5-6.5 h. The obtained powder is washed with deionized water by centrifugation for 3-5 times until the supernatant is neutral, and then dried in an oven at 45-55 °C to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0033] In step 1), the Bi3TiNbO9 precursor is mixed by Bi2O3:TiO2:Nb2O5 in a mass ratio of (1.397-1.399):(0.159-0.161):(0.265-0.267); preferably, the mass of Bi2O3, TiO2 and Nb2O5 is 1.398:0.160:0.266.

[0034] The ball-milling time is 3.5-4.5 h; preferably, the ball-milling time is 4 h.

[0035] The drying temperature is 45-55 °C, and preferably the drying temperature is 50 °C.

[0036] The drying time is 11.5-12.5h; preferably, the drying time is 12h.

[0037] The calcination temperature is 798-802℃, preferably, the calcination temperature is 800℃.

[0038] The calcination time is 1.98-2.02h, preferably, the calcination time is 2h.

[0039] In step 2), the KBr solution is prepared by dissolving KBr in deionized water, and the concentration of the KBr solution is 16.7-66.7mmol·L -1 ; the molar ratio of Bi(NO3)3·5H2O:KBr is (0.98-1.02):(0.98-1.02); preferably, the molar ratio of Bi(NO3)3·5H2O and KBr is 1:1.

[0040] The molar ratio of Bi(NO3)3·5H2O:Bi3TiNbO9 powder is (2-8):1.

[0041] The concentration of the added glacial acetic acid is 3.48-3.52mol / L; preferably, the concentration is 3.5mol / L.

[0042] The hydrothermal reaction temperature is 115-125℃; preferably, the hydrothermal reaction temperature is 120℃.

[0043] The hydrothermal reaction time is 5.5-6.5h; preferably, the hydrothermal reaction time is 6h.

[0044] The application will be further described in detail below in combination with examples:

[0045] Comparative Example 1

[0046] Bi3TiNbO9 is prepared by a molten salt method, and the specific steps are as follows:

[0047] 1) 1.398g Bi2O3, 0.160g TiO2 and 0.266g Nb2O5 are weighed, and 5.844g of a flux of NaCl and 7.455g of KCl are weighed in a ball mill jar;

[0048] 2) 90g of ball stones are added to the above powder, and 25mL of anhydrous ethanol (the mass ratio of the powder:anhydrous ethanol:ball stones is 1:1:6);

[0049] 3) After ball milling for 4h, drying is performed in an oven at 50℃ for 12h;

[0050] 4) The obtained powder is placed in a crucible and calcined at 800℃ for 2h;

[0051] 5) The calcined product was dissolved in deionized water and heated on a magnetic stirrer at 60°C, and washed 3 times until no Cl was detected in the supernatant - ;

[0052] 6) After the end of the salt washing, the powder was collected and dried at 50°C for 12h to obtain Bi3TiNbO9 powder.

[0053] Comparative Example 2

[0054] BiOBr was prepared by a hydrothermal method, and the specific steps were as follows:

[0055] 1) 1.944g of Bi(NO3)3·5H2O was dissolved in 30mL of deionized water containing 6mL of glacial acetic acid;

[0056] 2) 0.480g of KBr dissolved in 30mL of deionized water was added to the above solution at a uniform speed to make the molar ratio of Bi(NO3)3·5H2O to KBr 1:1, and stirred on a magnetic stirrer for 30min;

[0057] 3) The obtained solution was transferred to a 100mL polytetrafluoroethylene lined reaction kettle, and hydrothermal reaction was carried out at 120°C for 6h.

[0058] 4) After the reaction was completed and cooled, the obtained product was washed with deionized water until the pH was neutral, and finally dried at 50°C for 12h to obtain BiOBr.

[0059] Example 1

[0060] Bi3TiNbO9 / xBiOBr was prepared by a molten salt method and a one-step hydrothermal method, where x = 2, and x is the molar ratio of Bi(NO3)3·5H2O to Bi3TiNbO9.

[0061] A preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, and the specific steps were as follows:

[0062] 1) Bi3TiNbO9 powder was prepared: Bi2O3, TiO2 and Nb2O5 were mixed in a mass ratio of 1.397:0.159:0.265 to obtain Bi3TiNbO9 precursor, then NaCl and KCl as flux were mixed with Bi3TiNbO9 precursor in a molar ratio of NaCl:KCl:Bi3TiNbO9 precursor = 49.8:49.8:0.98; ball milling in anhydrous ethanol for 3.5h, drying in a drying oven at 45°C for 11.5h, and calcining at 798°C for 1.98h, then washing the powder with deionized water until no Cl was detected in the supernatant - ; finally, the sample was dried at 45°C for 11.5h to obtain Bi3TiNbO9 powder;

[0063] 2) Dissolve Bi(NO3)3·5H2O in 30 mL of deionized water containing 6 mL of glacial acetic acid, add 0.2269 g of Bi3TiNbO9 powder obtained in step 1), stir well, and then add 30 mL of 16.7 mmol·L⁻¹ solution dropwise at a uniform rate. -1 A KBr solution was prepared, maintaining a molar ratio of Bi(NO3)3·5H2O to KBr of 0.98:0.99. Simultaneously, the molar ratio of Bi(NO3)3·5H2O to Bi3TiNbO9 powder was adjusted to 2:1. After stirring thoroughly again, a hydrothermal reaction was carried out. The mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor and subjected to a hydrothermal reaction at 115 °C for 5.5 h. The resulting powder was washed three times with deionized water by centrifugation until the supernatant was neutral, and then dried in an oven at 45 °C for 11.5 h to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0064] Example 2

[0065] Bi3TiNbO9 / xBiOBr was prepared by a molten salt method and a one-step hydrothermal method, where x = 3 and x is the molar ratio of Bi(NO3)3·5H2O to Bi3TiNbO9.

[0066] A method for preparing a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, the specific steps of which are as follows:

[0067] 1) Preparation of Bi3TiNbO9 powder: Bi2O3, TiO2, and Nb2O5 were mixed in a mass ratio of 1.398:0.16:0.266 to obtain the Bi3TiNbO9 precursor. Then, NaCl and KCl, as eutectic agents, were mixed with the Bi3TiNbO9 precursor in a molar ratio of NaCl:KCl:Bi3TiNbO9 precursor = 49.8:49.9:1. The mixture was ball-milled in anhydrous ethanol for 4 h, dried in a drying oven at 50 °C for 12 h, and calcined at 799 °C for 2 h. The powder was then washed with deionized water until no Cl was detected in the supernatant. - Finally, the sample is dried at 50℃ for 12 hours to obtain Bi3TiNbO9 powder.

[0068] 2) Dissolve Bi(NO3)3·5H2O in 30 mL of deionized water containing 6 mL of glacial acetic acid, add 0.2275 g of Bi3TiNbO9 powder obtained in step 1), stir well, and then add 30 mL of 25 mmol·L⁻¹ solution dropwise at a uniform rate. -1KBr solution, keeping the molar ratio of Bi(NO3)3·5H2O and KBr at 1:1.01, while adjusting the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9 powder to 3:1, stirring uniformly again, then carrying out hydrothermal reaction, transferring the mixture to a 100 mL polytetrafluoroethylene-lined reaction kettle, and carrying out hydrothermal reaction at 120°C for 6h; centrifugally washing the obtained powder with deionized water for 4 times until the supernatant is neutral, and drying in an oven at 50°C for 12h, to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0069] Example 3

[0070] Bi3TiNbO9 / xBiOBr is prepared by a molten salt method and a one-step hydrothermal method, where x = 5, and x is the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9.

[0071] A preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, and the specific steps are as follows:

[0072] 1) Bi3TiNbO9 powder is prepared: Bi2O3, TiO2 and Nb2O5 are mixed in a mass ratio of 1.399:0.161:0.267 to obtain Bi3TiNbO9 precursor, then NaCl and KCl as fluxes are mixed with the Bi3TiNbO9 precursor in a molar ratio of NaCl:KCl:Bi3TiNbO9 precursor = 50.1:50.2:1.01; ball milling in anhydrous ethanol for 4.5h, drying in a drying oven at 55°C for 12.5h, and calcining at 800°C for 2h, then washing the powder with deionized water until no Cl is detected in the supernatant - ; finally, the sample is dried at 55°C for 12.5h to obtain Bi3TiNbO9 powder;

[0073] 2) Bi(NO3)3·5H2O is dissolved in 30mL deionized water containing 6mL glacial acetic acid, 0.2280g Bi3TiNbO9 powder obtained in step 1) is added, and 30mL of 41.7mmol·L -1KBr solution, keeping the molar ratio of Bi(NO3)3·5H2O and KBr at 1.01:1.02, while adjusting the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9 powder to 5:1, stirring uniformly again, then carrying out hydrothermal reaction, transferring the mixture to a 100 mL polytetrafluoroethylene-lined reaction kettle, and carrying out hydrothermal reaction at 125°C for 6.5 h; centrifugally washing the obtained powder with deionized water for 3 times until the supernatant is neutral, and drying in an oven at 55°C for 12.5 h, to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0074] Example 4

[0075] Bi3TiNbO9 / xBiOBr is prepared by a molten salt method and a one-step hydrothermal method, where x = 8, and x is the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9.

[0076] A preparation method of a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, and the specific steps are as follows:

[0077] 1) Bi3TiNbO9 powder is prepared: Bi2O3, TiO2 and Nb2O5 are mixed in a mass ratio of 1.397:0.161:0.266 to obtain Bi3TiNbO9 precursor, then NaCl and KCl as fluxes are mixed with the Bi3TiNbO9 precursor in a molar ratio of NaCl:KCl:Bi3TiNbO9 precursor = 49.8:50.2:1.01; ball milling in anhydrous ethanol for 4 h, drying in a drying oven at 55°C for 12 h, and calcining at 800°C for 2 h, then washing the powder with deionized water until no Cl is detected in the supernatant - ; finally, the sample is dried at 50°C for 12 h to obtain Bi3TiNbO9 powder;

[0078] 2) Bi(NO3)3·5H2O is dissolved in 30 mL deionized water containing 6 mL glacial acetic acid, 0.2289 g of Bi3TiNbO9 powder obtained in step 1) is added, and 30 mL of Bi(NO3)3·5H2O solution with a concentration of 66.7 mmol·L -1KBr solution, keeping the molar ratio of Bi(NO3)3·5H2O and KBr at 1:1, while adjusting the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9 at 8:1, stirring uniformly again, then carrying out the hydrothermal reaction, transferring the mixture into a 100 mL polytetrafluoroethylene-lined reaction kettle, carrying out the hydrothermal reaction at 125℃ for 5.5 h; centrifugally washing the obtained powder with deionized water for 5 times until the supernatant is neutral, and drying in an oven at 55℃ for 11.5 h, to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst.

[0079] Referring to Figure 1 XRD patterns of the heterojunction photocatalysts prepared according to different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr; Figure 1 It can be seen that as the molar ratio of Bi(NO3)3·5H2O and Bi3TiNbO9 gradually increases during the preparation process, the mass fraction of BiOBr in the BiOBr / Bi3TiNbO9 heterojunction increases accordingly, and the diffraction peaks belonging to BiOBr and Bi3TiNbO9 can be observed simultaneously in Bi3TiNbO9 / 3BiOBr.

[0080] Referring to Figure 2 UV-diffuse reflectance absorption spectra of the heterojunction photocatalysts prepared according to different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr; Figure 2 It is proved that as the mass fraction of BiOBr increases, the visible light absorption capacity of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst is obviously improved.

[0081] Referring to Figure 3Scanning electron microscope images of the heterojunction photocatalysts prepared with different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr; Figure 3 The scanning electron microscope images also prove that the second phase of BiOBr grows on the surface of the Bi3TiNbO9 nanosheet and forms a heterostructure, and with the increase of the BiOBr composite amount, more heterojunction interfaces are formed.

[0082] Referring to Figure 4 Tetracycline hydrochloride degradation curves of the heterojunction photocatalysts prepared with different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in Examples 1-4 and Comparative Examples 1 and 2 of the present application; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr; as shown in Figure 4 It can be found from the test of degrading antibiotic TC (tetracycline hydrochloride) under simulated visible light that the Bi3TiNbO9 / 2BiOBr, Bi3TiNbO9 / 3BiOBr, Bi3TiNbO9 / 5BiOBr, and Bi3TiNbO9 / 8BiOBr heterojunction photocatalysts exhibit better photocatalytic degradation efficiency than pure Bi3TiNbO9 and BiOBr, and the Bi3TiNbO9 / 3BiOBr has the best photocatalytic degradation performance. The photocatalytic degradation rate is calculated by kinetic simulation.

[0083] Table 1 Photocatalytic degradation rate of photocatalysts

[0084]

[0085] Referring to Figure 5Linear fitting of photodegradation rate of the heterojunction photocatalyst prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in the present application examples 1-4 and comparative examples 1 and 2; (a) Bi3TiNbO9; (b) 2D / 2D Bi3TiNbO9 / 2BiOBr; (c) 2D / 2D Bi3TiNbO9 / 3BiOBr heterojunction photocatalyst; (d) 2D / 2D Bi3TiNbO9 / 5BiOBr heterojunction photocatalyst; (e) 2D / 2D Bi3TiNbO9 / 8BiOBr heterojunction photocatalyst; (f) BiOBr; see Table 1 for the photodegradation rate table of the heterojunction photocatalyst prepared by different molar ratios of Bi3TiNbO9 and Bi(NO3)3·5H2O disclosed in the present application examples 1-4 and comparative examples 1 and 2; as Figure 5 As shown in Table 1 and Table 1, it can be found that the degradation rate of Bi3TiNbO9 / 3BiOBr is 5.6 times that of Bi3TiNbO9 and 1.4 times that of pure BiOBr, and the TC degradation percentage is close to 63% under 60 min light irradiation. This fully proves that loading BiOBr on the surface of Bi3TiNbO9 and forming a heterojunction structure is an effective strategy for developing high-efficiency photocatalysts. On the one hand, the strong absorption of BiOBr to visible light widens the spectral absorption range of the photocatalyst, and on the other hand, the built-in electric field of the heterostructure promotes the migration of photo-generated carriers.

[0086] Referring to Figure 6 The photocatalytic mechanism diagram of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst disclosed in the present application is shown in the figure. As can be seen from the figure, electrons are transferred from the conduction band of Bi3TiNbO9 to the conduction band of BiOBr, and holes are transferred from the valence band of BiOBr to the valence band of Bi3TiNbO9, thereby realizing effective separation of electrons and holes, inhibiting electron-hole recombination, and improving photocatalytic efficiency.

[0087] The 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst prepared by the present application has a simple preparation process, low hydrothermal reaction temperature and short time, and is suitable for industrial production. The prepared 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst has many active sites, high photo-generated carrier separation efficiency, and high-efficiency antibiotic photodegradation performance, and is expected to be applied in the field of sewage treatment and the like.

[0088] The above content only illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method for preparing a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst, characterized in that, include: Bi(NO3)3·5H2O was dissolved in glacial acetic acid solution, Bi3TiNbO9 powder was added, and the mixture was stirred evenly. KBr solution was added, and the mixture was stirred evenly again. A hydrothermal reaction was carried out. After cooling, the mixture was washed and dried to obtain a 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst. The molar ratio of Bi(NO3)3·5H2O:Bi3TiNbO9 powder is (2~8):1; The hydrothermal reaction temperature is 115~125 ℃; the hydrothermal reaction time is 5.5~6.5 h.

2. The preparation method of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst according to claim 1, characterized in that, The KBr solution was prepared by dissolving KBr in deionized water, with a concentration of 16.7–66.7 mmol·L⁻¹. -1 The molar ratio of Bi(NO3)3·5H2O:KBr is (0.98~1.02):(0.98~1.02).

3. The preparation method of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst according to claim 1, characterized in that, The concentration of the glacial acetic acid solution is 3.48~3.52 mol / L.

4. The preparation method of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst according to claim 1, characterized in that, The Bi3TiNbO9 powder was prepared by the molten salt method. The preparation method included: mixing NaCl:KCl:Bi3TiNbO9 precursor in a molar ratio of (49.8~50.2):(49.8~50.2):(0.98~1.02), ball milling for 3.5~4.5 h, drying for 11.5~12.5 h, calcining at 798~802 ℃ for 1.98~2.02 h, and washing until Cl was undetectable in the supernatant. - After drying, Bi3TiNbO9 powder was obtained.

5. The preparation method of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst according to claim 4, characterized in that, The Bi3TiNbO9 precursor is a mixture of Bi2O3:TiO2:Nb2O5 in a mass ratio of (1.397~1.399):(0.159~0.161):(0.265~0.267).

6. The 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the 2D / 2D BiOBr / Bi3TiNbO9 heterojunction photocatalyst according to claim 6 in the degradation of antibiotics.

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