Method for preparing bismuth trioxide-bismuth subcarbonate-cerium dioxide ternary nanocomposite by one-step molten salt method

Abstract

This invention relates to the field of nanophotocatalytic materials technology, and provides a one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites. The method involves mixing sodium bismuthate dihydrate, cerium acetate, and sodium nitrate as solid raw materials, grinding them uniformly to obtain a solid mixture, and then heating the solid mixture in a sodium nitrate molten salt medium to simultaneously generate bismuth trioxide, bismuth oxycarbonate, and cerium dioxide through a one-step in-situ reaction, which then composites to form a Bi₂O₃-3Bi₂O₂CO₃-4CeO₂ ternary nanocomposite. The advantages of this invention are: by using a one-pot molten salt in-situ reaction to simultaneously generate and in-situ composite bismuth trioxide, bismuth oxycarbonate, and cerium dioxide, it avoids the problems of cumbersome step-by-step synthesis, difficulty in component control, and poor bonding effects in existing methods.

Description

Technical Field

[0001] This invention relates to the field of nanophotocatalytic materials technology, and in particular to a method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites by a one-step molten salt method. Background Technology

[0002] In recent years, bismuth-based photocatalysts have become a research hotspot due to their unique electronic structure, strong visible light absorption, and high degradation activity. Among them, bismuth trioxide (Bi₂O₃) and bismuth oxycarbonate (Bi₂O₂CO₃) have unique crystal structures, good photocatalytic activity, are recyclable, and non-toxic, showing broad application prospects in environmental remediation and photodegradation of organic matter. In addition, cerium dioxide (CeO₂) possesses excellent optical, electrical, magnetic, and chemical properties, exhibiting outstanding catalytic performance and enzyme-mimicking activity, while also being chemically stable, biocompatible, and non-toxic.

[0003] The aforementioned single semiconductor catalysts generally suffer from drawbacks in photocatalytic applications, such as high recombination rates of photogenerated electron-hole pairs and narrow photoresponse ranges, which limit their application efficiency. Constructing heterojunctions by combining these catalysts can effectively promote photogenerated carrier separation, broaden the photoresponse range, and improve photocatalytic efficiency and performance, representing the current mainstream improvement approach.

[0004] However, existing ternary and multi-component composite materials mostly employ stepwise synthesis, which suffers from cumbersome preparation steps, complex processes, difficulty in quantitative control of components, and ineffective combination of components. Therefore, there is an urgent need to provide a method for preparing ternary nanocomposites that is simple to process, synthesizes in one step, allows for controllable composition, enables in-situ composite formation, and is suitable for industrial production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites. This method generates bismuth trioxide, bismuth oxycarbonate and cerium dioxide simultaneously and in situ through a one-pot molten salt in-situ reaction, thus avoiding the problems of cumbersome step-by-step synthesis, difficulty in controlling components and poor bonding effect of existing methods.

[0006] The present invention solves the above-mentioned technical problems by adopting the following technical solutions: A one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites involves mixing and grinding sodium bismuthate dihydrate (NaBiO3·2H2O), cerium acetate (Ce(CH3COO)3), and sodium nitrate (NaNO3) into a homogeneous solid mixture. The solid mixture is then heated in a sodium nitrate molten salt medium to simultaneously generate bismuth trioxide (Bi2O3), bismuth oxycarbonate (Bi2O2CO3), and cerium dioxide (CeO2) through a one-step in-situ reaction, forming a Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite. The reaction process is as follows: .

[0007] As one of the preferred embodiments of the present invention, the molar ratio of sodium bismuthate dihydrate, cerium acetate and sodium nitrate is 2:1:40.

[0008] As one of the preferred embodiments of the present invention, the heating reaction temperature of the solid mixture is 350°C and the reaction time is 2-6 hours.

[0009] As one of the preferred embodiments of the present invention, the heating reaction is carried out in a covered crucible, and the reaction atmosphere is air.

[0010] As one of the preferred embodiments of the present invention, after the heating reaction, the reaction product is washed with deionized water and then dried to obtain the Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

[0011] As one of the preferred embodiments of the present invention, the specific drying conditions are: drying at 120°C for 2 hours.

[0012] As one of the preferred embodiments of the present invention, in the final obtained Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite, the average grain size of Bi2O2CO3 is 51.5~62.7nm.

[0013] Reaction principle: In the sodium nitrate molten salt medium of ionic solution, NaBiO3·2H2O, as a bismuth source, undergoes a redox reaction with Ce(CH3COO)3, being converted into Bi2O3 and Bi2O2CO3; among which Ce(CH3COO)3 acts as both a reducing agent and a cerium and carbon source. Simultaneously, Ce... 3+ Oxidized to Ce 4+ CeO2 is formed, and some acetate ions are oxidized to carbonate ions. This redox reaction proceeds synergistically in the molten salt system, simultaneously generating three products: Bi2O3, Bi2O2CO3, and CeO2, which then combine in situ to form a Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

[0014] In the above reaction system, sodium nitrate molten salt has ionic liquid properties and can fully dissolve Ce(CH3COO)3. Its low viscosity and high ion mobility can establish an ultrafast mass transfer channel, improve reaction efficiency, and achieve effective composite of Bi2O3, Bi2O2CO3 and CeO2.

[0015] The advantages of this invention compared to the prior art are: (1) The present invention adopts a one-step molten salt synthesis process, abandons the stepwise preparation mode of traditional multi-component composite materials, and provides a method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposite; the reaction system of the present invention constructs an ionic environment with molten salt medium, which can effectively dissolve reactants, accelerate the diffusion of substances, and enable the redox reaction to be completed simultaneously and synergistically, so as to promote the in-situ composite formation of heterojunction structure of each component and improve the composite effect and structural stability of the product; (2) The sodium nitrate molten salt used in the method of the present invention is a cheap and readily available conventional raw material, and cerium acetate can be used as a reducing agent, cerium source and carbon source at the same time; the reaction process does not require high temperature calcination, and can be completed under low temperature and normal pressure conditions, without the need for sealed pressure-resistant equipment, the preparation conditions are mild and economical. (3) The method of the present invention is simple in process, easy to operate, and the reaction conditions and raw material ratios are controllable. The preparation process is stable and can efficiently obtain composite photocatalytic materials with uniform structure. It is suitable for large-scale industrial production and provides a feasible solution for the development and application of environmental purification photocatalytic materials. Attached Figure Description

[0016] Figure 1 The image shows a transmission electron microscope (TEM) image of the product prepared in Example 3 of the present invention (the scale bar is 100 nm). Figure 2 The XRD patterns of the products prepared in Examples 1, 2, and 3 of this invention are shown (with reference to the XRD standard cards of Bi2O3, Bi2O2CO3, and CeO2). Figure 3 The XRD patterns of the products prepared in Example 3 and the comparative example of the present invention are shown (with reference to the XRD standard cards of Bi2O3, Bi2O2CO3 and CeO2). Detailed Implementation

[0017] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Furthermore, unless otherwise specified, the reagents and experimental methods used in the following embodiments, comparative examples, and experimental examples are all conventional reagents or methods in the art and will not be described again.

[0018] Example 1 This embodiment describes a one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites, comprising the following steps: (1) Mix 0.02 mol NaBiO3·2H2O, 0.01 mol Ce(CH3COO)3 and 0.4 mol NaNO3 solid raw materials and grind them evenly to obtain a solid mixture.

[0019] (2) The solid mixture obtained in step (1) is added to a 50ml alumina crucible with a lid and placed in a high-temperature furnace and heated for 2 hours in an air atmosphere at 350℃. During the heating process, NaNO3 melts to form an ion-melting medium. In this medium environment, NaBiO3·2H2O undergoes a redox reaction with Ce(CH3COO)3 and is converted into Bi2O3 and Bi2O2CO3. At the same time, Ce(CH3COO)3 is oxidized to CeO2. The reaction simultaneously generates three products: Bi2O3, Bi2O2CO3 and CeO2. The components recombine in situ to form a ternary complex of Bi2O3-3Bi2O2CO3-4CeO2. The overall reaction process is as follows: .

[0020] (3) The product obtained in step (2) was washed with deionized water and then dried at 120°C for 2 hours to obtain the target product Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

[0021] Example 2 This embodiment describes a one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites, comprising the following steps: (1) Mix 0.02 mol NaBiO3·2H2O, 0.01 mol Ce(CH3COO)3 and 0.4 mol NaNO3 solid raw materials and grind them evenly to obtain a solid mixture.

[0022] (2) The solid mixture obtained in step (1) is added to a 50ml alumina crucible with a lid and placed in a high-temperature furnace and heated at 350℃ in air atmosphere for 4 hours. During the heating process, NaNO3 melts to form an ion-melting medium. In this medium environment, NaBiO3·2H2O undergoes a redox reaction with Ce(CH3COO)3 and is converted into Bi2O3 and Bi2O2CO3. At the same time, Ce(CH3COO)3 is oxidized to CeO2. The reaction simultaneously generates three products: Bi2O3, Bi2O2CO3 and CeO2. The components recombine in situ to form a ternary complex of Bi2O3-3Bi2O2CO3-4CeO2. The overall reaction process is as follows: .

[0023] (3) The product obtained in step (2) was washed with deionized water and then dried at 120°C for 2 hours to obtain the target product Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

[0024] Example 3 This embodiment describes a one-step molten salt method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposites, comprising the following steps: (1) Mix 0.02 mol NaBiO3·2H2O, 0.01 mol Ce(CH3COO)3 and 0.4 mol NaNO3 solid raw materials and grind them evenly to obtain a solid mixture.

[0025] (2) The solid mixture obtained in step (1) is added to a 50ml alumina crucible with a lid and placed in a high-temperature furnace and heated for 6 hours in an air atmosphere at 350℃. During the heating process, NaNO3 melts to form an ion-melting medium. In this medium environment, NaBiO3·2H2O undergoes a redox reaction with Ce(CH3COO)3 and is converted into Bi2O3 and Bi2O2CO3. At the same time, Ce(CH3COO)3 is oxidized to CeO2. The reaction simultaneously generates three products: Bi2O3, Bi2O2CO3 and CeO2. The components recombine in situ to form a ternary complex of Bi2O3-3Bi2O2CO3-4CeO2. The overall reaction process is as follows: .

[0026] (3) The product obtained in step (2) was washed with deionized water and then dried at 120°C for 2 hours to obtain the target product Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

[0027] Comparative Example The method for preparing bismuth trioxide-bismuth oxycarbonate-cerium dioxide ternary nanocomposite in this comparative example is basically the same as that in Example 3, except that NaNO3 is not added, while the other raw material ratios, process conditions, and operating steps are completely consistent with those in Example 3.

[0028] Experimental Example 1 The product obtained in the above embodiments (taking Example 3 as an example) was observed under a transmission electron microscope (TEM), and the results are as follows. Figure 1 As shown. From Figure 1It can be seen that the prepared Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite exhibits a blocky morphology with a relatively uniform particle size distribution, ranging from approximately 40 to 90 nm. The components achieved in-situ composite formation during the molten salt reaction, without significant phase separation or loose mechanical mixing. This indicates that the one-step molten salt method of this invention can effectively prepare ternary nanocomposite photocatalytic materials with regular morphology and uniform structure.

[0029] Experimental Example 2 X-ray diffraction (XRD) analysis was performed on the products obtained in the above examples and comparative examples, and the results are as follows: Figure 2 , Figure 3 As shown.

[0030] Figure 2 The XRD patterns of the products prepared in Examples 1, 2, and 3 of this invention are shown below. Figure 3 The XRD patterns of the products prepared in Example 3 and the comparative example of this invention are shown below, with reference to the X-ray diffraction standard cards for Bi2O2CO3 (PDF#41-1488), Bi2O3 (PDF#74-1374), and CeO2 (PDF#34-0394). Figure 2 It can be seen that the XRD patterns of the products in each embodiment show obvious characteristic diffraction peaks of Bi2O2CO3, Bi2O3, and CeO2 (the characteristic diffraction peaks of Bi2O3 or CeO2 partially overlap with the characteristic diffraction peaks of other products), and there are no diffraction peaks of other substances. This indicates that the products in each embodiment are composed only of Bi2O2CO3, Bi2O3, and CeO2 crystals, and are pure Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposites; from Figure 3 It can be seen that, compared with Example 3, the XRD pattern of the product of the comparative example (without NaNO3 molten salt medium) only shows a weak characteristic diffraction peak of Bi2O2CO3, while the characteristic diffraction peaks of Bi2O3 and CeO2 are not obvious. At the same time, there are diffraction peaks of other substances. This indicates that under the condition of no molten salt medium, the redox reaction is not fully carried out, the crystallinity of Bi2O2CO3 is poor, and the target phases Bi2O3 and CeO2 are difficult to form a crystalline structure. The product composition is significantly different from that of the crystalline ternary complex, which proves that the molten salt medium plays a key role in promoting the full reaction and the formation of crystalline phases.

[0031] Furthermore, based on the XRD patterns of the products from Examples 1, 2, and 3, and using the Scherrer formula, the average grain sizes of Bi₂O₂CO₃ in the products of Examples 1, 2, and 3 were calculated to be 51.5 nm, 57.1 nm, and 62.7 nm, respectively (basically consistent with the TEM observation results of Experimental Example 1). This indicates that the average grain size of Bi₂O₂CO₃ in the products increases slowly with increasing reaction time. Since the characteristic diffraction peaks of Bi₂O₃ or CeO₂ overlap with the characteristic diffraction portions of other components, the average grain sizes of Bi₂O₃ and CeO₂ were not calculated. However, TEM images show that the average particle sizes of Bi₂O₃ and CeO₂ are both within the nanometer range.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing ternary nanocomposite of bismuth trioxide-bismuth oxy carbonate-cerium dioxide by one-step molten salt method, characterized in that, Sodium bismuthate dihydrate, cerium acetate, and sodium nitrate solid raw materials were mixed and ground evenly to obtain a solid mixture. The solid mixture was then heated in a sodium nitrate molten salt medium to simultaneously generate bismuth trioxide, bismuth oxycarbonate, and cerium dioxide through a one-step in-situ reaction, forming a Bi₂O₃-3Bi₂O₂CO₃-4CeO₂ ternary nanocomposite. The reaction process is as follows: 。 2. The method of claim 1, wherein, The molar ratio of sodium bismuthate dihydrate, cerium acetate, and sodium nitrate is 2:1:

40.

3. The method of claim 1, wherein, The solid mixture is heated to a temperature of 350°C for a reaction time of 2-6 hours.

4. The method of claim 1, wherein, The heating reaction is carried out in a covered crucible under an air atmosphere.

5. The method according to claim 1, characterized in that, After the heating reaction, the reaction product was washed with deionized water and then dried to obtain the Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite.

6. The method according to claim 5, characterized in that, The specific drying conditions are: drying at 120℃ for 2 hours.

7. The method according to any one of claims 1 to 6, characterized in that, In the final Bi2O3-3Bi2O2CO3-4CeO2 ternary nanocomposite, the average grain size of Bi2O2CO3 is 51.5~62.7 nm.

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