Preparation method of alpha-Fe2O3-coated Bi2O3 core-shell ellipsoid

Abstract

The invention provides a preparation method of an alpha-Fe2O3 (at) Bi2O3 core-shell ellipsoid, and relates to a preparation method of a core-shell ellipsoid material, according to the method, fusiform alpha-Fe2O3 is taken as a core, Bi (NO3) 3.5 H2O is taken as a bismuth source, and polyvinylpyrrolidone (PVP) is utilized to assist a solvothermal method to successfully synthesize the alpha-Fe2O3 (at) Bi2O3 core-shell ellipsoid. By adjusting the addition amount of PVP, alpha-Fe2O3 and Bi2O3 core-shell ellipsoids with different shell thicknesses can be synthesized. The method is simple to operate and low in cost, and the prepared alpha-Fe2O3-Bi2O3 core-shell ellipsoid is stable in structure, good in dispersion, uniform in particle size and adjustable in morphology and size, and has important application prospects in the fields of photocatalysis, sensors, electrochemistry and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing a core-shell ellipsoid material, in particular to a method for preparing an alpha-Fe2O3@Bi2O3 core-shell ellipsoid. Background Art

[0002] α-Fe2O3 has good chemical stability, non-toxicity and wide distribution, and has important applications in photocatalysis, gas sensors and lithium-ion batteries. Bi2O3 is a semiconductor material with excellent light absorption properties, especially in the visible light region. It has significant light response ability. Combining it with α-Fe2O3 can not only enhance its photoelectric properties, but also improve its catalytic activity. Using Bi2O3 to coat the surface of α-Fe2O3 to form a core-shell structure is one of the effective strategies. The heterogeneous structure can significantly improve the comprehensive performance of the two and expand their application potential.

[0003] Common synthesis methods for core-shell structures include coprecipitation, chemical vapor deposition, hydrothermal and microemulsion. The coprecipitation method is simple and low-cost, but the morphology controllability is poor; the chemical vapor deposition method has precise surface coverage, but the operation is complicated and the cost is high; the microemulsion method can be synthesized at low temperatures, but the process is complicated. The hydrothermal method is simple to operate and low-cost. The synthesized product has high dispersibility, purity and crystallinity, and its morphology is controlled. It is the first choice for the preparation of α-Fe2O3 and Bi2O3 composite structures.

[0004] Sun et al. prepared α-Fe2O3 / Bi2O3 core-shell structure by hydrothermal method, but bismuth oxide was not evenly coated on the surface of α-Fe2O3, but attached to the surface of α-Fe2O3 in a scattered state of flakes, which made it not have good dispersibility and stability. In the α-Fe2O3 / Bi2O3 composite structure synthesized by Lei et al. by hydrothermal method, Bi2O3 nanosheets were deposited on the surface of α-Fe2O3 nanotube array. Li et al. synthesized Fe2O3 / Bi2O3 composite particles by hydrothermal method and ultrasound assistance, but the composite particles formed by this method had poor stability, and the α-Fe2O3 and Bi2O3 particles were easily separated due to external interference. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids, which adopts a solvothermal method similar to a hydrothermal method, uses ethanol as the main solvent for the reaction, uses α-Fe2O3 particles as the core, and uses Bi(NO3)3·5H2O as a bismuth source. With the assistance of PVP, Bi2O3 is successfully and evenly coated on the surface of α-Fe2O3 particles to prepare α-Fe2O3@Bi2O3 core-shell ellipsoids. The prepared α-Fe2O3@Bi2O3 core-shell ellipsoids have good dispersibility, uniform particle size distribution, and stable structure. The shell thickness of the core-shell ellipsoids can be regulated by changing the amount of PVP used.

[0006] The objective of the present invention is achieved through the following technical solutions: A method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids, the method is completed according to the following steps: 1. Stir and dissolve PVP in an ethanol solution, and then ultrasonically disperse α-Fe2O3 particles in the ethanol solution in which PVP is dissolved, and the resulting mixed solution is marked as solution A; in the above step 1, the concentration of α-Fe2O3 in solution A is 1.0-10 mg / mL, the amount of ethanol solution used is 20-400 mL, and the mass ratio of PVP to α-Fe2O3 particles is 0.4:1-3:1; 2. Stir and dissolve Bi(NO3)3·5H2O in diethylene glycol, and the resulting solution is marked as solution B; the molar ratio of Bi to Fe in the solution B in step 2 and the α-Fe2O3 particles in the solution A in step 1 is 0.3:1 to 3:1, and the amount of diethylene glycol used is 10 to 200 mL; 3. Slowly add solution A to solution B, and stir the resulting mixed solution magnetically at 20-40°C for 20-60 min, then transfer the mixed solution to a reactor and place it in a heating device for reaction; in the above step 3, the volume of the reactor is 50-1000 mL, the reaction temperature is 110-150°C, and the reaction time is 8-24 h; 4. The product after the reaction in step 3 is collected by centrifugation, and ultrasonically cleaned several times with ethanol and distilled water respectively. Finally, the product is dried at 40-80°C for 8-20h to obtain α-Fe2O3@Bi2O3 core-shell ellipsoid powder.

[0007] The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids comprises the following steps: in the above step 1, PVP is stirred and dissolved in an ethanol solution, and then α-Fe2O3 particles are ultrasonically dispersed in the ethanol solution in which PVP is dissolved, and the resulting mixed solution is marked as solution A; in the step 1, the concentration of α-Fe2O3 in solution A is 1.1-9.9 mg / mL, the amount of ethanol solution used is 25-395 mL, and the mass ratio of PVP to α-Fe2O3 particles is 0.5:1-2.9:1.

[0008] The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids is as follows: in the above step 2, Bi(NO3)3·5H2O is stirred and dissolved in diethylene glycol, and the resulting solution is marked as solution B; the molar ratio of Bi to Fe of Bi(NO3)3·5H2O in solution B in step 2 and α-Fe2O3 particles in solution A in step 1 is 0.4:1~2.9:1, and the amount of diethylene glycol used is 15~195mL.

[0009] The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids is as follows: in the above step 3, solution A is slowly added to solution B, the resulting mixed solution is magnetically stirred at 21-39°C for 21-59 minutes, and then the mixed solution is transferred to a reactor and placed in a heating device for reaction; in step 3, the volume of the reactor is 100-950 mL, the reaction temperature is 115-145°C, and the reaction time is 8.5-23.5 hours.

[0010] The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids is as follows: in the above step 4, the product after the reaction in step 3 is collected by centrifugation, and ultrasonically cleaned several times with ethanol and distilled water respectively, and finally the product is dried at 41~79°C for 8.5~19.5h to obtain α-Fe2O3@Bi2O3 core-shell ellipsoid powder.

[0011] Advantages of the invention 1. The present invention adopts PVP-assisted solvothermal method to prepare α-Fe2O3@Bi2O3 core-shell ellipsoids, and the core-shell ellipsoids have stable structure, good dispersibility and uniform particle size distribution. The synthesis method is highly operable, simple in process and low in cost.

[0012] 2. In the preparation method of the present invention, the introduction of PVP realizes the uniform coating of Bi2O3 on the surface of α-Fe2O3 particles, forming a complete shell structure, and by changing the amount of PVP, the shell thickness of the core-shell ellipsoid can be regulated to about 5~25nm, thereby improving the excellent performance of the structure and expanding its application potential in the fields of photocatalysis, sensors and electrochemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1Scanning electron microscope image of α-Fe2O3 particles in Example 1 of the present invention; Figure 2 Scanning electron microscope image of the α-Fe2O3@Bi2O3 core-shell ellipsoid prepared in Example 1 of the present invention. DETAILED DESCRIPTION Example 1

[0014] A method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids can be specifically completed according to the following steps: 1. Dissolve 0.1 g PVP in 80 mL ethanol by stirring, then disperse 0.1 g α-Fe2O3 particles in the ethanol solution containing PVP by ultrasonic. The resulting mixed solution is marked as solution A. 2. Dissolve 0.606 g Bi(NO3)3·5H2O in 40 mL diethylene glycol with stirring. The resulting solution is labeled as solution B. 3. Slowly add solution A to solution B, and stir the resulting mixed solution magnetically at 25°C for 25 min. Then transfer the mixed solution to a 200 mL reactor and place it in a heating device at 130°C for 10 h. 4. The product after the reaction in step 3 is collected by centrifugation, and ultrasonically cleaned several times with ethanol and distilled water respectively. Finally, the product is dried at 55°C for 12h to obtain α-Fe2O3@Bi2O3 core-shell ellipsoid powder.

[0015] Figure 1 This is a scanning electron microscope image of the α-Fe2O3 particles used in Example 1 of the present invention, which are spindle-shaped with sharp ends. Figure 2 This is a scanning electron microscope image of the α-Fe2O3@Bi2O3 core-shell ellipsoid prepared in Example 1 of the present invention, and Figure 1 In contrast, both ends of the product particles are passivated, and the surface of the α-Fe2O3 particles is coated with bismuth oxide to form α-Fe2O3@Bi2O3 core-shell ellipsoids.

Claims

1. A method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoids, characterized in that: The method is accomplished by following the steps below:

1. Stir and dissolve PVP in an ethanol solution, and then ultrasonically disperse α-Fe2O3 particles in the ethanol solution in which PVP is dissolved, and the resulting mixed solution is marked as solution A; in the above step 1, the concentration of α-Fe2O3 in solution A is 1.0-10 mg / mL, the amount of ethanol solution used is 20-400 mL, and the mass ratio of PVP to α-Fe2O3 particles is 0.4:1-3:1; 2. Stir and dissolve Bi(NO3)3·5H2O in diethylene glycol, and the resulting solution is marked as solution B; the molar ratio of Bi to Fe in the solution B in step 2 and the α-Fe2O3 particles in the solution A in step 1 is 0.3:1 to 3:1, and the amount of diethylene glycol used is 10 to 200 mL; 3. Slowly add solution A to solution B, and stir the resulting mixed solution magnetically at 20-40°C for 20-60 min, then transfer the mixed solution to a reactor and place it in a heating device for reaction; in the above step 3, the volume of the reactor is 50-1000 mL, the reaction temperature is 110-150°C, and the reaction time is 8-24 h; 4. The product after the reaction in step 3 is collected by centrifugation, and ultrasonically cleaned several times with ethanol and distilled water respectively. Finally, the product is dried at 40-80°C for 8-20h to obtain α-Fe2O3@Bi2O3 core-shell ellipsoid powder.

2. The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoid according to claim 1, characterized in that: In the above step 1, PVP is stirred and dissolved in an ethanol solution, and then α-Fe2O3 particles are ultrasonically dispersed in the ethanol solution in which PVP is dissolved, and the resulting mixed solution is marked as solution A; in step 1, the concentration of α-Fe2O3 in solution A is 1.1~9.9 mg / mL, the amount of ethanol solution used is 25~395mL, and the mass ratio of PVP to α-Fe2O3 particles is 0.5:1~2.9:

1.

3. The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoid according to claim 2, characterized in that: In the above step 2, Bi(NO3)3·5H2O is stirred and dissolved in diethylene glycol, and the resulting solution is marked as solution B; the molar ratio of Bi to Fe of Bi(NO3)3·5H2O in solution B in step 2 and α-Fe2O3 particles in solution A in step 1 is 0.4:1~2.9:1, and the amount of diethylene glycol used is 15~195mL.

4. The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoid according to claim 3, characterized in that: In the above step 3, solution A is slowly added to solution B, and the resulting mixed solution is magnetically stirred at 21-39° C. for 21-59 min. The mixed solution is then transferred to a reactor and placed in a heating device for reaction; in step 3, the volume of the reactor is 100-950 mL, the reaction temperature is 115-145° C., and the reaction time is 8.5-23.5 h.

5. The method for preparing α-Fe2O3@Bi2O3 core-shell ellipsoid according to claim 4, characterized in that: In the above step 4, the product after the reaction in step 3 is collected by centrifugation, and ultrasonically cleaned several times with ethanol and distilled water respectively. Finally, the product is dried at 41-79° C. for 8.5-19.5 h to obtain α-Fe2O3@Bi2O3 core-shell ellipsoid powder.

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