A method for preparing bismuth cuprate nano-powder by molten salt

Abstract

This invention provides a method for preparing bismuth cuprate nanopowder with molten salt assistance. Sodium bismuthate dihydrate, sodium sulfite, copper sulfate, and sodium nitrate are mixed and ground uniformly to obtain a solid mixture. The solid mixture is heated to melt the sodium nitrate, forming an ion-molten liquid environment, and the reaction takes place in this environment. During the reaction, sodium bismuthate dihydrate and sodium sulfite undergo a redox reaction to generate the transition product bismuth oxysulfate, producing hydroxide ions and forming a self-generated alkaline environment. Simultaneously, in this self-generated alkaline environment, bismuth oxysulfate and copper sulfate react to generate bismuth cuprate. The reaction product is then post-treated to obtain Bi₂CuO₄ nanopowder. The advantages of this invention are: based on the synthesis strategy of using an ion-molten liquid environment, accelerating reactant diffusion, and improving redox reaction efficiency, it can efficiently prepare bismuth cuprate nanopowder, and the preparation steps are simple, convenient, and low-cost.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and photocatalysis, and in particular to a method for preparing bismuth cuprate (Bi2CuO4) nanopowder with molten salt assistance. Background Technology

[0002] Bismuth cuprate (Bi2CuO4) is a low bandgap semiconductor material with advantages such as visible light response, photoelectrochemical stability, high charge separation efficiency, and environmental friendliness. It has broad application prospects in the fields of photocatalysis and photoelectrochemistry and can be used in scenarios such as pollutant degradation, water splitting for hydrogen production, and photocathodes.

[0003] Currently, common methods for preparing Bi2CuO4 include hydrothermal method, solution precipitation-calcination method, and high-temperature solid-state reaction method. Among them, hydrothermal method requires pressure-resistant equipment; solution precipitation-calcination method has many steps and requires high-temperature calcination; although high-temperature solid-state reaction method has simple process and low cost, the high reaction temperature can easily cause grain coarsening, making it difficult to obtain nanoscale powder.

[0004] Therefore, it is of great significance to develop a new method for preparing nano-sized Bi2CuO4 powder that is simple in process, low in cost, and efficient. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing Bi2CuO4 nanopowder with molten salt assistance. This method is based on a synthesis strategy that uses an ion-molten liquid environment to accelerate the diffusion of reactants and improve the efficiency of redox reactions. It can efficiently prepare bismuth cuprate nanopowder, and the preparation steps are simple, easy to operate, and low in cost.

[0006] The present invention solves the above-mentioned technical problems by adopting the following technical solutions: A method for preparing Bi₂CuO₄ nanoparticles with molten salt assistance involves mixing sodium bismuthate dihydrate, sodium sulfite, copper sulfate, and sodium nitrate solids, grinding them uniformly to obtain a solid mixture; heating the solid mixture to melt the sodium nitrate and form an ion-molten liquid environment, where a reaction takes place; during the reaction, sodium bismuthate dihydrate and sodium sulfite undergo a redox reaction to generate the transition product bismuth oxysulfate, producing hydroxide ions and forming an autogenous alkaline environment; simultaneously, in this autogenous alkaline environment, bismuth oxysulfate and copper sulfate react to generate bismuth cuprate; the reaction products are then post-treated to obtain Bi₂CuO₄ nanoparticles; the overall reaction process is as follows: .

[0007] As one of the preferred embodiments of the present invention, the molar ratio of sodium bismuthate dihydrate, sodium sulfite, copper sulfate and sodium nitrate is 2:2:1:30.

[0008] As one of the preferred embodiments of the present invention, the heating temperature of the solid mixture is 350°C and the reaction time is 5-10 h.

[0009] As one of the preferred embodiments of the present invention, the reaction process in the ion-molten liquid environment specifically includes: (1) Redox reaction: ; (2) The reaction that produces bismuth cuprate: .

[0010] As one of the preferred embodiments of the present invention, the post-processing step includes: washing the reaction product with deionized water and then drying it to obtain Bi2CuO4 nanoparticles.

[0011] As one of the preferred methods of the present invention, the drying is performed at 120°C for 2 hours.

[0012] As one of the preferred embodiments of the present invention, the average grain size of Bi2CuO4 in the obtained Bi2CuO4 nanopowder is 67.3~87.9nm.

[0013] Reaction principle: In this invention, solid sodium bismuthate dihydrate (pentavalent bismuth salt) is in situ reduced by sodium sulfite in molten sodium nitrate to the transition product bismuth oxysulfate (trivalent bismuth salt) and sodium hydroxide is produced. Simultaneously, under self-generated alkaline conditions, the transition product bismuth oxysulfate and copper sulfate further react to form bismuth cuprate. Within this reaction system, the ionic liquid properties of molten sodium nitrate dissolve both sodium sulfite and copper sulfate. Its low viscosity and high ion mobility establish an ultrafast mass transfer channel, improving reaction efficiency and enabling uniform nucleation and growth, ultimately yielding nanoscale bismuth cuprate.

[0014] The advantages of this invention compared to the prior art are: (1) The present invention adopts a molten salt-assisted synthesis strategy to construct an ion-molten liquid environment as a reaction system to achieve effective dissolution and rapid diffusion of reactants. During the reaction, hydroxide ions are generated in situ through redox reaction to form a self-generated alkaline environment. No additional alkaline reagents are required, so that redox reaction and combination reaction are completed in the same system, realizing "one-pot reaction" and significantly improving reaction efficiency. (2) The molten salt NaNO3 used in this invention is a cheap and readily available chemical raw material, and the overall raw material cost is low. At the same time, the reaction is carried out at a relatively low temperature, which does not require high-temperature calcination or closed pressure-resistant equipment, thus greatly improving the economic efficiency of the process. (3) The reaction temperature of this invention is controlled at 350℃, which is much lower than the temperature of the traditional high temperature solid-state reaction method. This can effectively suppress grain coarsening and ensure that the final average grain size of the nanoscale Bi2CuO4 powder is 67.3~87.9nm, thus solving the technical problem that it is difficult to prepare nanoscale powder by high temperature solid-state method. (4) The process of this invention is simple and safe to operate. It does not require complex equipment and complicated steps. The post-treatment only requires simple deionized water washing and drying. The process is simple. Moreover, no harmful gases are generated during the reaction process. It is environmentally friendly and easy to industrialize and promote on a large scale. Attached Figure Description

[0015] Figure 1 The image shows a 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 the various embodiments and comparative examples of the present invention are shown (with reference to the XRD standard cards of Bi2CuO4 and Bi2O3). Detailed Implementation

[0016] 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.

[0017] Example 1 This embodiment describes a method for preparing Bi2CuO4 nanopowder using molten salt assistance: (1) Mix 0.01 mol sodium bismuthate dihydrate, 0.01 mol sodium sulfite, 0.005 mol copper sulfate and 0.15 mol sodium nitrate solid raw materials and grind them evenly to obtain a solid mixture.

[0018] (2) Add the solid mixture obtained in step (1) into a 50ml alumina crucible with a lid, and heat it in a high-temperature furnace at 350°C for 5 hours. During the heating process, sodium nitrate melts and forms an ion-molten liquid environment. Under this environment, sodium bismuthate dihydrate and sodium sulfite undergo a redox reaction to generate the transition product bismuth oxysulfate and generate hydroxide ions, forming an autogenous alkaline environment. At the same time, under the autogenous alkaline environment, the transition product bismuth oxysulfate and copper sulfate further react to generate bismuth copperate.

[0019] Specifically, the above reaction includes the following two simultaneous processes: Redox reaction: ; The reaction that produces bismuth cuprate: .

[0020] The entire reaction process is as follows: .

[0021] (3) Wash the reaction product of step (2) with deionized water, and then dry it at 120°C for 2 hours to obtain the target product Bi2CuO4 nanopowder.

[0022] Example 2 This embodiment describes a method for preparing Bi2CuO4 nanopowder using molten salt assistance: (1) Mix 0.01 mol sodium bismuthate dihydrate, 0.01 mol sodium sulfite, 0.005 mol copper sulfate and 0.15 mol sodium nitrate solid raw materials and grind them evenly to obtain a solid mixture.

[0023] (2) Add the solid mixture obtained in step (1) into a 50ml alumina crucible with a lid, and heat it in a high-temperature furnace at 350℃ for 8 hours. During the heating process, sodium nitrate melts and forms an ion-molten liquid environment. Under this environment, sodium bismuthate dihydrate and sodium sulfite undergo a redox reaction to generate the transition product bismuth oxysulfate and generate hydroxide ions, forming an autogenous alkaline environment. At the same time, under the autogenous alkaline environment, the transition product bismuth oxysulfate and copper sulfate further react to generate bismuth copperate.

[0024] Specifically, the above reaction includes the following two simultaneous processes: Redox reaction: ; The reaction that produces bismuth cuprate: .

[0025] The entire reaction process is as follows: .

[0026] (3) Wash the reaction product of step (2) with deionized water, and then dry it at 120°C for 2 hours to obtain the target product Bi2CuO4 nanopowder.

[0027] Example 3 This embodiment describes a method for preparing Bi2CuO4 nanopowder using molten salt assistance: (1) Mix 0.01 mol sodium bismuthate dihydrate, 0.01 mol sodium sulfite, 0.005 mol copper sulfate and 0.15 mol sodium nitrate solid raw materials and grind them evenly to obtain a solid mixture.

[0028] (2) Add the solid mixture obtained in step (1) into a 50ml alumina crucible with a lid, and heat it in a high-temperature furnace at 350℃ for 10h. During the heating process, sodium nitrate melts and forms an ion-molten liquid environment. Under this environment, sodium bismuthate dihydrate and sodium sulfite undergo a redox reaction to generate the transition product bismuth oxysulfate and generate hydroxide ions, forming an autogenous alkaline environment. At the same time, under the autogenous alkaline environment, the transition product bismuth oxysulfate and copper sulfate further react to generate bismuth copperate.

[0029] Specifically, the above reaction includes the following two simultaneous processes: Redox reaction: ; The reaction that produces bismuth cuprate: .

[0030] The entire reaction process is as follows: .

[0031] (3) Wash the reaction product of step (2) with deionized water, and then dry it at 120°C for 2 hours to obtain the target product Bi2CuO4 nanopowder.

[0032] Comparative Example 1 The method for preparing Bi2CuO4 nanopowder in this comparative example is basically the same as that in Example 3, except that sodium nitrate (NaNO3) is not added. The other raw material types, molar ratios, and process steps (grinding, heating temperature of 350℃, heating time of 10h, and post-treatment) are completely consistent with those in Example 3.

[0033] Comparative Example 2 The method for preparing Bi2CuO4 nanopowder in this comparative example is basically the same as that in Example 3, except that the raw materials are replaced with 0.005 mol bismuth oxysulfate (Bi2O2SO4) and 0.005 mol copper sulfate, and 0.02 mol sodium hydroxide is added (to provide an alkaline environment). Sodium bismuthate dihydrate and sodium sulfite are not added. The remaining process steps (adding sodium nitrate, grinding, heating temperature of 350℃, heating time of 10h, and post-treatment) are completely consistent with those in Example 3.

[0034] 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 1As can be seen, the Bi2CuO4 powder prepared by this invention exhibits a polygonal nanoparticle morphology with clear particle outlines and uniform size. Combined with a 100nm scale, its grain size can be estimated to be in the range of approximately 80~100nm, which is typical of nanoscale powder. The overall particle dispersion is good, with no obvious agglomeration, indicating that the molten salt-assisted synthesis process effectively suppressed grain coarsening and successfully prepared Bi2CuO4 nanoparticles with regular morphology and uniform particle size.

[0035] 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 As shown.

[0036] Figure 2 The XRD patterns of the products prepared in the various embodiments and comparative examples of this invention are shown below, with reference to the X-ray diffraction standard cards for Bi2CuO4 (PDF#79-1810) and Bi2O3 (PDF#74-1375). Figure 2 It can be seen that the XRD patterns of the products in each embodiment show obvious Bi2CuO4 characteristic diffraction peaks and no diffraction peaks of other substances, indicating that the products in each embodiment are composed only of Bi2CuO4 crystals and are pure Bi2CuO4. However, the XRD pattern of the product in Comparative Example 1 does not show obvious Bi2CuO4 characteristic diffraction peaks, but there are Bi2O3 characteristic diffraction peaks and many impurity peaks, indicating that the reaction cannot proceed completely under the condition of no sodium nitrate molten salt, and it is difficult to obtain the target product. Although the XRD pattern of the product in Comparative Example 2 shows Bi2CuO4 characteristic diffraction peaks, there are obvious impurity peaks, and the intensity of the Bi2CuO4 diffraction peaks is weaker than that in Example 3, indicating that its product has lower purity and poorer crystallinity.

[0037] Furthermore, based on the XRD patterns of the products from Examples 1, 2, and 3, and using the Scherrer formula for calculation, the average grain sizes of Bi2CuO4 in the products from Examples 1, 2, and 3 were 67.3 nm, 79.3 nm, and 87.9 nm, respectively (which are basically consistent with the TEM observation results of Experimental Example 1). This indicates that the average grain size of Bi2CuO4 in the product gradually increases with the extension of reaction time. This demonstrates that, under the conditions of the present invention, the grain size of Bi2CuO4 in the product can be controlled by controlling the reaction time.

[0038] The above description is merely 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 bismuth cuprate nanopowder with molten salt assistance, characterized in that, Sodium bismuthate dihydrate, sodium sulfite, copper sulfate, and sodium nitrate solids were mixed and ground uniformly to obtain a solid mixture. The solid mixture was heated to melt the sodium nitrate, creating an ion-molten liquid environment, where the reaction took place. During the reaction, sodium bismuthate dihydrate and sodium sulfite underwent a redox reaction to generate the transition product bismuth oxysulfate, producing hydroxide ions and forming an autogenous alkaline environment. Simultaneously, in this autogenous alkaline environment, bismuth oxysulfate and copper sulfate reacted to generate bismuth cuprate. The reaction products were post-treated to obtain Bi₂CuO₄ nanoparticles. The overall reaction process is as follows: 。 2. The method according to claim 1, characterized in that, The molar ratio of sodium bismuthate dihydrate, sodium sulfite, copper sulfate, and sodium nitrate is 2:2:1:

30.

3. The method according to claim 1, characterized in that, The solid mixture is heated to 350°C and the reaction time is 5-10 h.

4. The method according to claim 1, characterized in that, The reaction process in the ion-molten liquid environment specifically includes: (1) Redox reaction: ； (2) The reaction that produces bismuth cuprate: 。 5. The method according to claim 1, characterized in that, The post-processing steps include: washing the reaction product with deionized water and then drying it to obtain Bi2CuO4 nanoparticles.

6. The method according to claim 5, characterized in that, The drying process involves drying at 120°C for 2 hours.

7. The method according to claim 1, characterized in that, The average grain size of the obtained Bi2CuO4 nanopowder is 67.3~87.9 nm.

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