A 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, its preparation method and application

Abstract

This invention discloses an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, its preparation method, and its application, belonging to the field of photocatalysis technology. The method involves adding Bi3TiNbO9 powder to deionized water and stirring to form a suspension, then adding AgNO3 powder and stirring until homogeneous. Finally, Na2HPO4·12H2O solution is added. By introducing silver phosphate onto the surface of bismuth titanate and constructing an 0D / 2D heterojunction, the built-in electric field of the heterojunction promotes the separation of photogenerated carriers. Simultaneously, the narrow bandgap silver phosphate's good response to visible light expands the spectral absorption range of the photocatalyst and inhibits photocorrosion of silver phosphate. The resulting 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst has multiple active sites, high photogenerated carrier separation efficiency, and excellent photocatalytic degradation performance of dyes. Furthermore, the preparation process of this invention is simple, with low reaction temperature, short reaction time, and low material cost, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] The rise of semiconductor photocatalysis technology has spanned several decades, beginning with the discovery of the "Honda-Fujishima Effect." Honda, under the guidance of his student Fujishima, discovered that ultraviolet light irradiation on a TiO2 electrode decomposes water into hydrogen and oxygen, a phenomenon known as the Honda-Fujishima Effect. In July 1972, they published this phenomenon in Nature, thus ushering in a new era of photocatalysis. In 1976, Garey et al. discovered the effective decomposition of polychlorinated biphenyls (PCBs) under ultraviolet light irradiation on TiO2, demonstrating that photocatalysis could be applied to the elimination of water and environmental pollution, further fueling the surge in semiconductor photocatalysis research. In recent years, people have gained a new understanding of the role of photocatalysis in environmental protection. Photocatalysis is an emerging high-tech field combining environmental science and environmental engineering. However, the large-scale industrial application of photocatalysis technology still faces significant challenges. For example, the low solar energy conversion efficiency restricts the practical application of photocatalysis technology.

[0003] The spontaneous polarization field within ferroelectric materials has been shown to effectively drive the separation of photogenerated charges, suppress recombination between photogenerated charges, and improve photocatalytic efficiency, attracting increasing attention from researchers. In recent years, ferroelectric Bi3TiNbO9 crystals, due to their typical ferroelectric properties, have been successfully used as photocatalysts for pollutant reduction, photocatalytic water splitting, and photocatalytic carbon dioxide reduction. Jiang et al. significantly reduced the band gap of Bi3TiNbO9 to nearly 1 eV using a Cr / Nb co-doping strategy. With only 10% Cr / Nb co-doping, hydrogen production increased more than twofold (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.). Cui et al., through Fe... 3+Doping strategies, which simultaneously induce oxygen vacancies and enhance ferroelectric polarization in Bi3TiNbO9 nanosheets, significantly improve photodegradation efficiency (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.). However, the catalytic performance of Bi3TiNbO9 reported in the literature is still limited, and the separation efficiency of its internal photogenerated carriers needs to be further improved; at the same time, the modification methods of Bi3TiNbO9 are also relatively simple, mainly focusing on doping strategies.

[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 an OD / 2DAg3PO4 / 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, and having a low separation efficiency of photogenerated carriers.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing an OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, comprising: adding Bi3TiNbO9 powder to deionized water and stirring to form a suspension, then adding AgNO3 powder, stirring evenly, adding Na2HPO4·12H2O solution, stirring evenly under light, washing, and drying to obtain the OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0008] Preferably, the mass ratio of Ag3PO4 powder to Bi3TiNbO9 powder is 20:(1-4); and the molar ratio of AgNO3 powder to Na2HPO4·12H2O is (2.95-3.05):(1.95-2.05).

[0009] Preferably, the stirring temperature is 20–30°C and the stirring time is 0.4–0.6 h.

[0010] Preferably, the stirring temperature in the dark is 20-30°C and the time is 1.5-2.5 hours.

[0011] Preferably, the drying temperature is 45–55°C and the drying time is 11–13 hours.

[0012] Preferably, the Bi3TiNbO9 powder is prepared by the molten salt method. The specific preparation method is as follows: NaCl, KCl, and the Bi3TiNbO9 precursor are mixed, ball-milled in anhydrous ethanol, then dried, calcined, and washed until no Cl is detected in the supernatant. - After final drying, Bi3TiNbO9 powder can be obtained.

[0013] Preferably, the NaCl:KCl:Bi3TiNbO9 precursor is mixed in a molar ratio of (49.8~50.2):(49.8~50.2):(0.98~1.02); the Bi3TiNbO9 precursor is formed by mixing Bi2O3:TiO2:Nb2O5 in a mass ratio of (1.397~1.399):(0.159~0.161):(0.265~0.267).

[0014] Preferably, the ball milling time is 3.5 to 4.5 hours; the drying temperature is 45 to 55°C and the time is 11 to 13 hours; the calcination temperature is 798 to 802°C and the time is 1.98 to 2.02 hours.

[0015] The present invention also discloses the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst prepared by the above preparation method.

[0016] The present invention also discloses the application of the above-mentioned 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst in the degradation of organic dyes.

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

[0018] This invention discloses a method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst. The sample is prepared using a combination of molten salt method and room temperature co-precipitation method. The reaction temperature is low and the time is short, making it suitable for industrial production. Bi3TiNbO9 powder is added to deionized water and stirred to form a suspension. Then, AgNO3 powder is added and stirred until homogeneous. Next, Na2HPO4·12H2O solution is added. The AgNO3 powder reacts with the Na2HPO4·12H2O solution to generate Ag3PO4. After stirring evenly under light, the mixture is washed and dried to obtain the 0D / 2D... The Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, by introducing Ag3PO4 onto the surface of ferroelectric Bi3TiNbO9 and constructing an OD / 2DAg3PO4 / Bi3TiNbO9 heterojunction, achieves two advantages: firstly, the built-in electric field of the heterojunction promotes the separation of photogenerated carriers and suppresses electron-hole recombination; secondly, the narrow bandgap Ag3PO4's good response to visible light expands the spectral absorption range of the photocatalyst and inhibits the photocorrosion of Ag3PO4. The resulting OD / 2DAg3PO4 / Bi3TiNbO9 heterojunction photocatalyst exhibits highly efficient photodegradation of Rhodamine B, with the Ag3PO4 / Bi3TiNbO9-15% achieving a photodegradation efficiency of 97%, representing degradation rates 10 times and 1.5 times higher than those of pure Ag3PO4 and Bi3TiNbO9, respectively. This heterojunction photocatalyst holds promise for applications in wastewater treatment and other fields.

[0019] Furthermore, current methods for preparing Bi3TiNbO9 powder include solid-state methods and sol-gel methods. Solid-state methods are difficult to control uniformity because the solid medium used is not homogeneous enough, which may lead to product inhomogeneity. They also require high temperatures and pressures, resulting in higher costs. Sol-gel methods use expensive raw materials, have poor interparticle sintering properties, and exhibit significant shrinkage during drying, making them prone to agglomeration. This invention, however, uses a molten salt method to prepare Bi3TiNbO9 powder, which can lower the synthesis temperature, shorten the reaction time, and save costs. The synthesized two-dimensional sheet-like Bi3TiNbO9 powder has more active sites and a shorter charge transfer distance, giving it an advantage in the field of photocatalysis.

[0020] The present invention also discloses the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst prepared by the above preparation method. The morphological characteristics of 0D / 2D give it an increased specific surface area and more reactive sites.

[0021] This invention also discloses the application of the above-mentioned 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst in the degradation of organic dyes. The Ag3PO4 / Bi3TiNbO9-15% composite photocatalyst achieved a degradation rate of 97% for Rhodamine B under visible light irradiation within 6 minutes, which is 10 times and 1.5 times that of pure phase Ag3PO4 and Bi3TiNbO9, respectively, demonstrating highly efficient photocatalytic performance. Attached Figure Description

[0022] Figure 1 These are XRD patterns of OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 to Ag3PO4 as disclosed in Examples 1-4 of this invention; wherein, (a) Bi3TiNbO9; (b) Ag3PO4; (c) OD / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) OD / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) OD / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) OD / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst;

[0023] Figure 2 These are scanning electron microscope (SEM) images of 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 of this invention; wherein, (a) Ag3PO4; (b) Bi3TiNbO9; (c) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst under low magnification; and (d) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst under high magnification.

[0024] Figure 3 Rhodamine B degradation curves of OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 of this invention; (a) Bi3TiNbO9; (b) Ag3PO4; (c) OD / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) OD / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) OD / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) OD / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst;

[0025] Figure 4The linear fits of the photodegradation of Rhodamine B by 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 of this invention are as follows: (a) Bi3TiNbO9; (b) Ag3PO4; (c) 0D / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) 0D / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) 0D / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst.

[0026] Figure 5 This is a diagram illustrating the photocatalytic mechanism of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst disclosed in this invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of 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 skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] This invention constructs an Ag3PO4 / Bi3TiNbO9 heterojunction, which promotes the separation of photogenerated carriers and expands the spectral absorption range of the photocatalyst by utilizing the good visible light response of Ag3PO4, while also inhibiting the photocorrosion of Ag3PO4. The preparation process is simple, and the prepared Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst has a high efficiency in photodegrading organic dyes, and its photocatalytic effect is far superior to that of pure phase Ag3PO4 and Bi3TiNbO9.

[0031] A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst includes the following steps:

[0032] 1) Preparation of Bi3TiNbO9 powder: Mix 1.397–1.399 g Bi2O3, 0.159–0.161 g TiO2, and 0.265–0.267 g Bi3TiNbO9 according to the stoichiometric ratio of Bi3TiNbO9. Bi3TiNbO9 precursor was prepared by reacting Nb2O5 with NaCl and KCl as eutectic fluxes. The mixture was then mixed with the Bi3TiNbO9 precursor at a molar ratio of NaCl:KCl:Bi3TiNbO9 precursor of (49.8–50.2):(49.8–50.2):(0.98–1.02). The mixture was 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. The powder was then washed with hot deionized water until no Cl was detected in the supernatant. - Finally, the sample is dried at 45–55℃ for 11.5–12.5 h to obtain Bi3TiNbO9 powder;

[0033] 2) The Bi3TiNbO9 powder obtained in step 1) was uniformly dispersed in 14–16 mL of deionized water. The mass of Ag3PO4 was fixed at 0.2 g. 0.2425–0.2445 g of AgNO3 was added. After stirring at 20–30 °C for 0.4–0.6 h, 14–16 mL of Na2HPO4·12H2O solution was added dropwise at a uniform rate, maintaining the molar ratio of AgNO3 to Na2HPO4·12H2O at (2.95–3.05):(1.95–2.05). Simultaneously, the mass ratio of Ag3PO4 to Bi3TiNbO9 was adjusted to 20:(1–4). After stirring in the dark at 20–30 °C for 1.5–2.5 h, the reaction product was washed 3–5 times and dried at 45–55 °C for 11.5–12.5 h to obtain a series of 0D / 2D fractions of Bi3TiNbO9 with different mass fractions. Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0034] The present invention will be further described in detail below with reference to embodiments:

[0035] Comparative Example 1

[0036] The specific steps for preparing Bi3TiNbO9 using the molten salt method are as follows:

[0037] 1) Weigh 1.398g Bi2O3, 0.160g TiO2 and 0.266g Nb2O5, 5.844g NaCl and 7.455g KCl into a ball mill jar;

[0038] 2) Add 90g of pebbles and 25mL of anhydrous ethanol to the above powder (powder: anhydrous ethanol: pebbles mass ratio = 1:1:6);

[0039] 3) After ball milling for 4 hours, dry in an oven at 50°C for 12 hours;

[0040] 4) Place the powder obtained above in a crucible and calcine it at 800℃ for 2 hours;

[0041] 5) Dissolve the calcined product in deionized water, heat at 60°C on a magnetic stirrer, and wash three times until no Cl is detected in the supernatant. - ;

[0042] 6) After the salt washing is completed, the powder is collected and dried at 50℃ for 12 hours to obtain Bi3TiNbO9 powder.

[0043] Comparative Example 2

[0044] The specific steps for preparing pure Ag3PO4 using a room temperature coprecipitation method are as follows:

[0045] 1) Weigh 0.2435g of AgNO3 and dissolve it in 15ml of deionized water;

[0046] 2) Add 0.3423g of Na2HPO4·12H2O solution dissolved in 15mL of deionized water dropwise to the above solution at a uniform rate, so that the molar ratio of AgNO3 to Na2HPO4·12H2O is 3:2. Shield the solution from light and stir thoroughly on a magnetic stirrer.

[0047] 3) After the reaction is complete, the product is thoroughly washed with deionized water and then dried at 50°C for 12 hours to obtain Ag3PO4.

[0048] Example 1

[0049] Ag3PO4 / Bi3TiNbO9-x% was prepared by molten salt method and room temperature coprecipitation method, where x = 5 and x% is the mass ratio of Bi3TiNbO9 to Ag3PO4.

[0050] A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, the specific steps of which are as follows:

[0051] 1) Preparation of Bi3TiNbO9 powder: Bi2O3, TiO2, and Nb2O5 were mixed in a mass ratio of 1.398:0.160:0.266 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 = 50:50:1. 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 800 °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.

[0052] 2) With the mass of Ag3PO4 fixed at 0.2g, 0.01g of Bi3TiNbO9 powder obtained in step 1) was uniformly dispersed in 15mL of deionized water. 0.2435g of AgNO3 was added and stirred evenly. Then, 15mL of Na2HPO4·12H2O solution was added dropwise at a uniform rate, maintaining the molar ratio of AgNO3 to Na2HPO4·12H2O at 3:2. At the same time, the mass ratio of Ag3PO4 to Bi3TiNbO9 was adjusted to 20:1. The mixture was stirred at 25℃ in the dark for 2h. The resulting powder was washed four times by centrifugation with deionized water and dried in an oven at 50℃ for 12h to obtain an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0053] Example 2

[0054] Ag3PO4 / Bi3TiNbO9-x% was prepared by molten salt method and room temperature co-precipitation method, where x = 10 and x% is the mass ratio of Bi3TiNbO9 to Ag3PO4.

[0055] A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, the specific steps of which are as follows:

[0056] 1) Preparation of Bi3TiNbO9 powder: Bi2O3, TiO2, and Nb2O5 were mixed in a mass ratio of 1.397:0.159:0.265 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 = 49.8:49.9:0.99. The mixture was ball-milled in anhydrous ethanol for 3.5 h, dried in a drying oven at 45 °C for 11.5 h, and calcined at 798 °C for 1.98 h. The powder was then washed with deionized water until no Cl was detected in the supernatant. - Finally, the sample was dried at 45℃ for 11.5h to obtain Bi3TiNbO9 powder.

[0057] 2) With a fixed mass of 0.2 g of Ag3PO4, 0.02 g of Bi3TiNbO9 powder obtained in step 1) was uniformly dispersed in 14 mL of deionized water. 0.2425 g of AgNO3 was added and stirred evenly. Then, 14 mL of Na2HPO4·12H2O solution was added dropwise at a uniform rate, maintaining the molar ratio of AgNO3 to Na2HPO4·12H2O at 2.95:1.95. At the same time, the mass ratio of Ag3PO4 to Bi3TiNbO9 was adjusted to 20:2. The mixture was stirred at 20 °C in the dark for 1.5 h. The resulting powder was washed four times by centrifugation with deionized water and dried in an oven at 45 °C for 11.5 h to obtain an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0058] Example 3

[0059] Ag3PO4 / Bi3TiNbO9-x% was prepared by molten salt method and room temperature coprecipitation method, where x = 15 and x% is the mass ratio of Bi3TiNbO9 to Ag3PO4.

[0060] A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, the specific steps of which are as follows:

[0061] 1) Preparation of Bi3TiNbO9 powder: Bi2O3, TiO2, and Nb2O5 were mixed in a mass ratio of 1.399:0.161:0.267 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 = 50.2:50.1:1.02. The mixture was ball-milled in anhydrous ethanol for 4.5 h, dried in a drying oven at 55 °C for 12.5 h, and calcined at 802 °C for 2.02 h. The powder was then washed with deionized water until no Cl was detected in the supernatant. -Finally, the sample was dried at 55℃ for 12.5h to obtain Bi3TiNbO9 powder.

[0062] 2) With a fixed mass of 0.2 g of Ag3PO4, 0.03 g of Bi3TiNbO9 powder obtained in step 1) was uniformly dispersed in 16 mL of deionized water. 0.2445 g of AgNO3 was added, and after stirring evenly, 16 mL of Na2HPO4·12H2O solution was added dropwise at a uniform rate, maintaining the molar ratio of AgNO3 to Na2HPO4·12H2O at 3.05:2.05. At the same time, the mass ratio of Ag3PO4 to Bi3TiNbO9 was adjusted to 20:3. The mixture was stirred at 30 °C in the dark for 2.5 h. The resulting powder was washed 5 times by centrifugation with deionized water and dried in an oven at 55 °C for 12.5 h to obtain an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0063] Example 4

[0064] Ag3PO4 / Bi3TiNbO9-x% was prepared by molten salt method and room temperature co-precipitation method, where x = 20 and x% is the mass ratio of Bi3TiNbO9 to Ag3PO4.

[0065] A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, the specific steps of which are as follows:

[0066] 1) Preparation of Bi3TiNbO9 powder: Bi2O3, TiO2, and Nb2O5 were mixed in a mass ratio of 1.398:0.160:0.266 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 = 50:50:1. 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 800 °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.

[0067] 2) With the mass of Ag3PO4 fixed at 0.2g, 0.04g of Bi3TiNbO9 powder obtained in step 1) was uniformly dispersed in 15mL of deionized water. 0.2435g of AgNO3 was added and stirred evenly. Then, 15mL of Na2HPO4·12H2O solution was added dropwise at a uniform rate, maintaining the molar ratio of AgNO3 to Na2HPO4·12H2O at 3:2. At the same time, the mass ratio of Ag3PO4 to Bi3TiNbO9 was adjusted to 20:4. The mixture was stirred at 25℃ in the dark for 2h. The resulting powder was washed four times by centrifugation with deionized water and dried in an oven at 50℃ for 12h to obtain an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst.

[0068] See Figure 1 The XRD patterns of 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 to Ag3PO4 as disclosed in Examples 1-4 of this invention are shown below; wherein, (a) Bi3TiNbO9; (b) Ag3PO4; (c) 0D / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) 0D / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) 0D / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst; from Figure 1 It can be seen that as the mass ratio of Bi3TiNbO9 to Ag3PO4 gradually increases during the preparation process, the mass fraction of Bi3TiNbO9 in the Ag3PO4 / Bi3TiNbO9 heterojunction increases accordingly. Diffraction peaks belonging to Ag3PO4 and Bi3TiNbO9 can be observed simultaneously in Ag3PO4 / Bi3TiNbO9-15%.

[0069] See Figure 2 The images show scanning electron microscope (SEM) images of 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 of this invention; where (a) Ag3PO4; (b) Bi3TiNbO9; (c) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst under low magnification; and (d) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst under high magnification. As can be seen from the images, the second phase of Ag3PO4 grows on the surface of the Bi3TiNbO9 nanoplate and forms a heterostructure, and the heterostructure interface increases with the increase of Bi3TiNbO9 composite content.

[0070] See Figure 3 Rhodamine B degradation curves of 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 of this invention; (a) Bi3TiNbO9; (b) Ag3PO4; (c) 0D / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) 0D / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst; as shown in the figure, tests on the visible light degradation dye Rhodamine B revealed that the 0D / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst, 0D / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst, 0D / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst, and 0D / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst all exhibited superior photodegradation efficiency compared to pure Bi3TiNbO9 and Ag3PO4, with Ag3PO4 / Bi3TiNbO9-15% showing the best photodegradation performance. The photodegradation rate was calculated through kinetic simulation.

[0071] Table 1. Photodegradation rate of photocatalysts

[0072]

[0073] See Figure 4 Linear fitting of the photodegradation rate of heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 and Comparative Examples 1 and 2 of this invention; (a) Bi3TiNbO9; (b) Ag3PO4; (c) OD / 2D Ag3PO4 / Bi3TiNbO9-5% heterojunction photocatalyst; (d) OD / 2D Ag3PO4 / Bi3TiNbO9-10% heterojunction photocatalyst; (e) OD / 2D Ag3PO4 / Bi3TiNbO9-15% heterojunction photocatalyst; (f) OD / 2D Ag3PO4 / Bi3TiNbO9-20% heterojunction photocatalyst; See Table 1 for the photodegradation rate table of heterojunction photocatalysts prepared with different mass ratios of Bi3TiNbO9 and Ag3PO4 as disclosed in Examples 1-4 and Comparative Examples 1 and 2 of this invention; Figure 4As shown in Table 1, the photodegradation efficiency of Ag3PO4 / Bi3TiNbO9-15% reached 97%, which was 10 times and 1.5 times that of pure Ag3PO4 and Bi3TiNbO9, respectively. This fully demonstrates that loading Ag3PO4 onto the surface of Bi3TiNbO9 to form a heterojunction structure is an effective strategy for developing highly efficient photocatalysts.

[0074] See Figure 5 This is a photocatalytic mechanism diagram of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst disclosed in this invention. As can be seen from the diagram, on the one hand, the strong absorption of visible light by Ag3PO4 broadens the spectral absorption range of the photocatalyst; on the other hand, the built-in electric field of the heterostructure promotes the migration of photogenerated carriers. Electrons transfer from the conduction band of Bi3TiNbO9 to the conduction band of Ag3PO4, and holes transfer from the valence band of Ag3PO4 to the valence band of Bi3TiNbO9, thereby achieving effective separation of electrons and holes, inhibiting electron-hole recombination, and improving photocatalytic efficiency.

[0075] The 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst prepared by this invention has a simple preparation process, low reaction temperature, and short reaction time, making it suitable for industrial production. The prepared 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst has multiple active sites, high photogenerated carrier separation efficiency, and high performance in photodegrading dyes, and is expected to be applied in wastewater treatment and other fields.

[0076] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing an 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst, characterized in that, include: Bi3TiNbO9 powder was added to deionized water and stirred to form a suspension. Then, AgNO3 powder was added and stirred evenly. Na2HPO4•12H2O solution was added, and the reaction was stirred evenly under light. After washing and drying, an OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst was obtained. By introducing Ag3PO4 onto the surface of ferroelectric Bi3TiNbO9 and constructing an OD / 2D Ag3PO4 / Bi3TiNbO9 heterojunction, on the one hand, the built-in electric field of the heterojunction promotes the separation of photogenerated carriers and suppresses electron-hole recombination; on the other hand, the good response of the narrow bandgap Ag3PO4 to visible light is utilized to expand the spectral absorption range of the photocatalyst and suppress the photocorrosion of Ag3PO4. The mass ratio of Ag3PO4 powder to Bi3TiNbO9 powder is 20:(1~4); the molar ratio of AgNO3 powder to Na2HPO4•12H2O is (2.95~3.05):(1.95~2.05). The stirring reaction is carried out at a temperature of 20-30 °C for 0.4-0.6 h; the stirring in the dark is carried out at a temperature of 20-30 °C for 1.5-2.5 h.

2. The preparation method of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst according to claim 1, characterized in that, The drying temperature is 45~55 ℃, and the time is 11~13 h.

3. The preparation method of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst according to claim 1, characterized in that, The Bi3TiNbO9 powder was prepared by the molten salt method. Specifically, NaCl, KCl, and the Bi3TiNbO9 precursor were mixed, ball-milled in anhydrous ethanol, then dried, calcined, and washed until no Cl was detected in the supernatant. - After final drying, Bi3TiNbO9 powder can be obtained.

4. The preparation method of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst according to claim 3, characterized in that, The NaCl:KCl:Bi3TiNbO9 precursor is mixed in a molar ratio of (49.8~50.2):(49.8~50.2):(0.98~1.02); the Bi3TiNbO9 precursor is formed by mixing Bi2O3:TiO2:Nb2O5 in a mass ratio of (1.397~1.399):(0.159~0.161):(0.265~0.267).

5. The preparation method of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst according to claim 3, characterized in that, In the process of preparing Bi3TiNbO9 powder by molten salt method, the ball milling time is 3.5~4.5 h; the drying temperature is 45~55 ℃ and the time is 11~13 h; the calcination temperature is 798~802 ℃ and the time is 1.98~2.02 h.

6. The 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst prepared by any one of claims 1 to 5.

7. The application of the 0D / 2D Ag3PO4 / Bi3TiNbO9 heterojunction photocatalyst according to claim 6 in the degradation of organic dyes.

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