One-pot hydrothermal synthesis of bismuth oxide chloride-tin dioxide nanocomposites

Abstract

The application provides a one-pot hydrothermal preparation method of a bismuth oxychloride-tin dioxide nanocomposite, which comprises the following steps: dispersing sodium bismuthate and stannous chloride in deionized water to obtain a solid-liquid mixture; and placing the solid-liquid mixture in a hydrothermal condition to perform a hydrothermal reaction; in the same hydrothermal system, the sodium bismuthate and the stannous chloride perform a redox reaction to generate BiOCl, and at the same time, generate Sn4+ and OH-; the Sn4+ and the OH- perform in-situ precipitation and are loaded on the surface of the BiOCl, are converted into SnO2 crystals through hydrothermal crystallization, and finally, the BiOCl-SnO2 nanocomposite is obtained in one step. Based on the synergistic effect of the redox reaction, the precipitation reaction and the hydrothermal crystallization reaction, the BiOCl-SnO2 nanocomposite is synthesized in one step in a single reaction system, and no alkali agent and template agent need to be added, so that the process is simple, the conditions are compatible, the product has high purity, is green and environment-friendly, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the fields of nanocomposite material preparation and photocatalysis technology, and particularly to a one-pot hydrothermal preparation method for bismuth oxychloride-tin dioxide (BiOCl-SnO2) nanocomposite materials. Background Technology

[0002] Bismuth oxychloride (BiOCl) is a semiconductor material with a stable layered structure and a strong built-in electric field, and it has important applications in many fields such as photocatalysis. However, BiOCl alone suffers from the problem of easy recombination of photogenerated carriers during photocatalysis, resulting in low catalytic efficiency.

[0003] In the field of semiconductor photocatalysis, heterostructure construction strategies are often used to enhance the catalytic performance of materials, combining two semiconductor materials. Tin dioxide (SnO2) is a high-performance semiconductor photocatalytic material, and theoretically, it can be combined with BiOCl to form a heterojunction, thereby improving carrier separation efficiency and surface reactivity, and ultimately enhancing the photocatalytic effect of BiOCl-based materials.

[0004] However, conventional methods for constructing heterojunctions between different semiconductors often employ a stepwise approach. This involves first preparing two individual materials separately, then achieving composite synthesis via impregnation-calcination or hydrothermal methods, or synthesizing individual products separately in different precursor systems before composite synthesis. These methods have significant drawbacks: the reaction conditions (such as pH, temperature, and precursor type) for different semiconductors are typically incompatible, making simultaneous synthesis and composite synthesis in the same system difficult. Specifically, for the composite of BiOCl and SnO2, the preparation of BiOCl requires a weakly acidic to neutral environment to inhibit BiO2 synthesis. 3+ Excessive hydrolysis and the preparation of SnO2 require a strong alkaline environment; the reaction conditions for the two are significantly different, making it impossible to complete the composite process in the same system.

[0005] Therefore, there are currently no publicly reported methods for the direct one-pot synthesis of BiOCl-SnO2 nanocomposites in a single reaction system. Developing a simple, condition-compatible, green, and efficient one-pot preparation technology is of great practical significance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a one-pot hydrothermal preparation method for BiOCl-SnO2 nanocomposites. Based on the synergistic effect of redox reaction, precipitation reaction and hydrothermal crystallization reaction, BiOCl-SnO2 nanocomposites are synthesized in a single reaction system in one step without the need to add alkali and template agent. The process is simple, the conditions are compatible, the product has high purity, and it is green and environmentally friendly, making it suitable for industrial production.

[0007] The present invention solves the above-mentioned technical problems by adopting the following technical solutions: A one-pot hydrothermal preparation method for BiOCl-SnO2 nanocomposites involves dispersing sodium bismuthate and stannous chloride in deionized water to obtain a solid-liquid mixture. The solid-liquid mixture is then subjected to a hydrothermal reaction. In the same hydrothermal system, sodium bismuthate and stannous chloride undergo a redox reaction to generate BiOCl, simultaneously producing tetravalent tin ions and hydroxide ions. The tetravalent tin ions and hydroxide ions precipitate in situ and are loaded onto the BiOCl surface, which is then converted to SnO2 crystals via hydrothermal crystallization. Finally, the BiOCl-SnO2 nanocomposites are obtained in one step. The overall reaction process is as follows: .

[0008] As one of the preferred embodiments of the present invention, the molar ratio of sodium bismuthate to stannous chloride is 1:1.

[0009] As one of the preferred embodiments of the present invention, the solid-liquid mixture is reacted under hydrothermal conditions at 180~200℃ for 5~10 hours.

[0010] As one of the preferred embodiments of the present invention, the reaction process under hydrothermal conditions specifically includes: (1) Redox reaction: ; (2) Precipitation reaction: ; (3) Hydrothermal crystallization reaction: .

[0011] As one of the preferred embodiments of the present invention, after the hydrothermal reaction, the steps of centrifugation of the reaction product, washing with deionized water, and drying are further included to finally obtain the target BiOCl-SnO2 nanocomposite.

[0012] As one of the preferred embodiments of the present invention, the specific drying conditions are: drying at 120°C for 2 hours.

[0013] As one of the preferred embodiments of the present invention, in the final BiOCl-SnO2 nanocomposite product, the average grain size of BiOCl is 83.1~101.5nm and the average grain size of SnO2 is 6.2~13.9nm.

[0014] Reaction principle: Solid sodium bismuthate is in situ reduced to BiOCl by stannous chloride in aqueous solution. Stannous chloride acts as both a reducing agent and a chlorine source. Simultaneously, tetravalent tin ions and hydroxide ions are generated. The precipitation reaction between the tetravalent tin ions and hydroxide ions produces amorphous SnO2, which is deposited in situ on the BiOCl surface. Under hydrothermal conditions, it further crystallizes into crystalline SnO2, thus forming a BiOCl-SnO2 nanocomposite. In the above reaction system, the redox reaction of sodium bismuthate and stannous chloride generates nano-BiOCl while simultaneously producing tetravalent tin ions and hydroxide ions. This ensures that the precipitation reaction of tetravalent tin ions and hydroxide ions produces SnO2 and deposits it on the BiOCl surface. The redox reaction and precipitation reaction work synergistically, promoting the complete completion of both reactions. Finally, the BiOCl-SnO2 nanocomposite is obtained by a one-pot hydrothermal method.

[0015] The advantages of this invention compared to the prior art are: (1) This invention achieves the synthesis of BiOCl-SnO2 nanocomposite in a single hydrothermal system in one step through the synergistic effect of the redox reaction, precipitation reaction and hydrothermal crystallization reaction of sodium bismuthate and stannous chloride. It solves the problems of complex step-by-step preparation process and cumbersome process in the prior art, significantly shortens the preparation cycle, reduces production cost, is easy to operate and is easy to promote on a large scale. (2) This invention cleverly utilizes the hydroxide ions generated in situ by the redox reaction to provide the alkaline environment required for the precipitation of SnO2, avoiding the pH conflict between BiOCl synthesis (weak acid / neutral) and SnO2 synthesis (strong base) in the traditional process. Moreover, no template agent or alkaline substance needs to be added to the reaction system, which simplifies the control of process parameters, and the product has high purity and good economic efficiency. (3) In this invention, SnO2 is deposited and crystallized in situ at the same time as BiOCl is generated. The interface between the two is in close contact and the heterojunction structure is stable, which is conducive to the efficient separation and migration of photogenerated carriers and ensures the excellent photocatalytic performance of the material from the structure. (4) The raw materials used in this invention, sodium bismuthate and stannous chloride, are conventional chemical raw materials with low cost. The entire reaction process is carried out in aqueous solution without high-temperature calcination, resulting in low energy consumption. There are no side reactions during the reaction process, which has atom economy characteristics. No toxic or harmful byproducts are produced, making it environmentally friendly and meeting the requirements for green synthesis of materials. Attached Figure Description

[0016] Figure 1 This is a TEM image of the product prepared in Example 2 of the present invention (the scale bar in the image is 50 nm). Figure 2 The XRD patterns of the products prepared in Examples 1, 2, and 3 of this invention are compared (using the XRD standard cards of BiOCl and SnO2 as references). Figure 3The XRD patterns of the products prepared in Examples 3, 4, and 5 of this invention are compared (with the XRD standard cards of BiOCl and SnO2 as references). 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 and experimental examples are all conventional reagents or methods in the art and will not be described again.

[0018] Example 1 This embodiment of a one-pot hydrothermal preparation method for BiOCl-SnO2 nanocomposites includes the following steps: (1) Add 0.01 mol sodium bismuthate and 0.01 mol stannous chloride to a 50 ml hydrothermal reactor containing 40 ml deionized water and mix well to obtain a solid-liquid mixture.

[0019] (2) The solid-liquid mixture obtained in step (1) was reacted at 180°C for 10 h under hydrothermal conditions. In the same hydrothermal system, BiOCl-SnO2 nanocomposite was finally prepared in one step through the redox reaction of sodium bismuthate and stannous chloride, the in-situ deposition reaction of tetravalent tin ions and hydroxide ions, and the synergistic effect of hydrothermal crystallization.

[0020] The coordinated reaction specifically includes the following steps that occur simultaneously: a. Redox reaction: Sodium bismuthate reacts with stannous chloride in a redox reaction to produce BiOCl, while tetravalent tin ions and hydroxide ions are generated. The reaction formula is as follows: ; b. Precipitation reaction: Tetravalent tin ions react with hydroxide ions in situ to form amorphous SnO2, which is then deposited in situ on the BiOCl surface. The reaction formula is as follows: ; c. Hydrothermal crystallization reaction: Amorphous SnO2 is further crystallized into crystalline SnO2 under hydrothermal conditions, as shown in the following reaction formula: .

[0021] The entire reaction process is as follows: .

[0022] (3) The product obtained in step (2) is centrifuged, washed with deionized water, and dried at 120°C for 2 hours to obtain the target product BiOCl-SnO2 nanocomposite.

[0023] Example 2 The one-pot hydrothermal preparation method of BiOCl-SnO2 nanocomposite in this embodiment is basically the same as that in Example 1, except that in step (2), the obtained solid-liquid mixture is reacted under hydrothermal conditions at 190°C for 10 hours.

[0024] Example 3 The one-pot hydrothermal preparation method of BiOCl-SnO2 nanocomposite in this embodiment is basically the same as that in Example 1, except that in step (2), the obtained solid-liquid mixture is reacted under hydrothermal conditions at 200°C for 10 hours.

[0025] Example 4 The one-pot hydrothermal preparation method of BiOCl-SnO2 nanocomposite in this embodiment is basically the same as that in Example 1, except that in step (2), the obtained solid-liquid mixture is reacted under hydrothermal conditions at 200°C for 8 hours.

[0026] Example 5 The one-pot hydrothermal preparation method of BiOCl-SnO2 nanocomposite in this embodiment is basically the same as that in Example 1, except that in step (2), the obtained solid-liquid mixture is reacted under hydrothermal conditions at 200°C for 5 hours.

[0027] Experimental Example 1 The product obtained in the above embodiments (taking Example 2 as an example) was observed under a transmission electron microscope (TEM), and the results are as follows. Figure 1 As shown.

[0028] from Figure 1 As can be seen, the BiOCl-SnO2 nanocomposite prepared by this invention has a rod-like morphology. BiOCl is the main rod structure, and SnO2 nanoparticles are uniformly and densely deposited and crystallized in situ on the surface and inside of BiOCl. The interface between the two phases is tightly bonded without obvious gaps or shedding, forming a structurally stable BiOCl-SnO2 heterojunction composite. This in situ synchronous growth structure can effectively promote the efficient separation and migration of photogenerated carriers, providing a structural basis for the excellent photocatalytic performance of the material.

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

[0030] Figure 2 The above are comparison results of the XRD patterns of the products prepared in Examples 1, 2, and 3 of this invention. Figure 3The XRD patterns of the products prepared in Examples 3, 4, and 5 of this invention are compared using the X-ray diffraction standard cards for BiOCl (PDF#73-2060) and SnO2 (PDF#75-9496) as references. Figure 2 , Figure 3 It can be seen that the XRD patterns of the products in each embodiment show obvious characteristic diffraction peaks of BiOCl and SnO2, and no diffraction peaks of other substances, indicating that the products in each embodiment are composed only of BiOCl and SnO2 crystals and are pure BiOCl-SnO2 composites.

[0031] Furthermore, based on the XRD patterns of the products from Examples 1, 2, 3, 4, and 5, calculations were performed using the Scherrer formula. The average grain sizes of BiOCl in the products from Examples 1, 2, 3, 4, and 5 were 83.1 nm, 90.9 nm, 101.5 nm, 100.6 nm, and 99.3 nm, respectively, while the average grain sizes of SnO2 were 6.2 nm, 8.8 nm, 13.9 nm, 13.3 nm, and 12.2 nm, respectively. This indicates that with increasing reaction temperature, the average grain sizes of both BiOCl and SnO2 in the products increased significantly, with SnO2 showing a more pronounced increase. Additionally, with prolonged reaction time, the average grain size of BiOCl increased slowly, while the average grain size of SnO2, although smaller, increased more rapidly. Therefore, compared to reaction time, the crystal growth of BiOCl and SnO2 in the products is more sensitive to reaction temperature.

[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 one-pot hydrothermal preparation method for bismuth oxychloride-tin dioxide nanocomposite, characterized in that, Sodium bismuthate and stannous chloride were dispersed in deionized water to obtain a solid-liquid mixture. The solid-liquid mixture was placed under hydrothermal conditions for hydrothermal reaction. In the same hydrothermal system, sodium bismuthate and stannous chloride underwent a redox reaction to generate BiOCl, while tetravalent tin ions and hydroxide ions were generated. The tetravalent tin ions and hydroxide ions precipitated in situ and were loaded on the surface of BiOCl. After hydrothermal crystallization, they were transformed into SnO2 crystals, and finally, BiOCl-SnO2 nanocomposite was obtained in one step. The reaction process under hydrothermal conditions specifically includes: (1) Redox reaction: ； (2) Precipitation reaction: ； (3) Hydrothermal crystallization reaction: ； The overall reaction process is as follows: 。 2. The preparation method according to claim 1, characterized in that, The molar ratio of sodium bismuthate to stannous chloride is 1:

1.

3. The preparation method according to claim 1, characterized in that, The solid-liquid mixture is reacted under hydrothermal conditions at 180~200℃ for 5~10 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that, Following the hydrothermal reaction, the process further includes centrifugation of the reaction product, washing with deionized water, and drying, ultimately obtaining the target BiOCl-SnO2 nanocomposite.

5. The preparation method according to claim 4, characterized in that, The specific drying conditions are: drying at 120℃ for 2 hours.

6. The preparation method according to claim 4, characterized in that, In the final BiOCl-SnO2 nanocomposite product, the average grain size of BiOCl was 83.1~101.5 nm, and the average grain size of SnO2 was 6.2~13.9 nm.

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