CN105772018A - A kind of Bi2WO6-BiFeO3 composite photocatalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a Bi2WO6-BiFeO3 compound photocatalyst and a preparing method thereof, and belongs to the technical field of inorganic environment-friendly photocatalytic materials.According to the technical scheme, the preparing method is characterized by comprising the steps that firstly, a bismuth nitrate pentahydrate aqueous solution is prepared, and ferric nitrate and sodium tungstate are added into the bismuth nitrate pentahydrate aqueous solution to form a mixed solution; secondly, the mixed solution obtained in the first step is stirred for 30 min, then an alkaline solution is used for regulating the pH value of the mixed solution to be 9-11, and then the mixed solution continues to be stirred for 1 h at the room temperature; thirdly, the mixed solution obtained in the second step is transferred into a hydrothermal reaction kettle, then the hydrothermal reaction kettle is put into a microwave digestion instrument for a microwave reaction at 180 DEG C for 10-30 min, cooling, centrifuging, washing and drying are carried out after the reaction is finished, and the magnetic Bi2WO6-BiFeO3 compound photocatalyst can be obtained.The prepared compound photocatalyst has a high visible light utilization rate and photocatalytic activity, has magnetism and is convenient to regenerate and recycle.

Description

A kind of Bi2WO6-BiFeO3 composite photocatalyst and preparation method thereof

technical field

The invention belongs to the technical field of inorganic environment-friendly photocatalytic materials, and in particular relates to a Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst and a preparation method thereof.

Background technique

With the rapid development of industry and technology, while enjoying the convenience brought by development, people are also tasting the consequences of environmental pollution. How to deal with the balance between environmental protection and development is an important issue at present. Semiconductor photocatalytic technology, as a new means of environmental governance, has a series of advantages such as non-toxic, harmless and low energy consumption, and has attracted widespread attention. In addition, it can also decompose toxic and harmful organic macromolecules into non-toxic and harmless inorganic small molecules such as water and carbon dioxide, without secondary pollution, so it has broad development space and application prospects.

Among many semiconductor photocatalytic materials, Bi ₂ WO ₆ is considered to be the most promising visible photocatalyst because of its narrow bandgap structure, which has a strong ability to degrade organic matter under visible light. However, the fast electron-hole recombination of pure Bi ₂ WO ₆ hinders its photocatalytic activity and also affects its practical application. In order to overcome this shortcoming of Bi ₂ WO ₆ , people try to combine Bi ₂ WO ₆ with other types of semiconductor materials to promote the separation of electrons and holes and improve its photocatalytic activity. Among many photocatalysts, BiFeO ₃ has narrow band gap, large specific surface area, and strong visible light catalytic activity. However, there is no relevant literature report on Bi ₂ WO ₆ -BiFeO ₃ composite photocatalysts.

Contents of the invention

The technical problem solved by the invention is to provide a magnetic Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst with high solar energy utilization rate, high photon quantum efficiency, easy recovery and good photocatalytic activity.

Another technical problem solved by the present invention is to provide a simple and easy-to-operate preparation method of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst.

In order to solve the above technical problems, the present invention adopts the following technical scheme, a preparation method of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst, which is characterized in that it includes the following steps: (1) Prepare bismuth nitrate pentahydrate and deionized water as raw materials An aqueous solution of bismuth nitrate pentahydrate, adding iron nitrate and sodium tungstate to the aqueous solution of bismuth nitrate pentahydrate under stirring conditions to form a mixed solution, wherein the molar ratio of added ferric nitrate to bismuth nitrate pentahydrate is 0.1-0.3:1; ( 2) Stir the mixed solution obtained in step (1) for 30 minutes, then adjust the pH value of the mixed solution to 9-11 with alkaline solution, and then continue to stir the mixed solution at room temperature for 1 hour; (3) Mix the mixed solution obtained in step (2) Transfer the mixed solution to a hydrothermal reaction kettle, then put the hydrothermal reaction kettle into a microwave digestion apparatus and react with microwave at 180°C for 10-30min. After the reaction is completed, it is cooled, centrifuged, washed and dried to obtain magnetic Bi ₂ WO _{6 -BiFeO3} composite photocatalyst.

Further preferably, the molar concentration of the bismuth nitrate pentahydrate aqueous solution in step (1) is 0.5-1 mol/L.

Further preferably, the alkali solution in step (2) is sodium hydroxide solution.

The Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst of the present invention is prepared according to the above method.

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

1. BiFeO ₃ has a narrow band gap, a large specific surface area, and strong visible light catalytic activity. It has a suitable band gap structure and can form a heterogeneous photocatalyst with Bi ₂ WO _6. Studies have shown that Bi ₂ WO ₆ The conduction band potential E _CB =0.25eV of the photocatalyst, the valence band potential E _VB =3.16eV, and the conduction band potential E _CB =0.1eV of the BiFeO ₃ photocatalyst, the valence band potential E _VB =2.3eV, in Bi ₂ WO ₆ -In the BiFeO ₃ compound semiconductor, the conduction band potential of BiFeO ₃ is more negative, and the photogenerated electrons can easily migrate from the conduction band of BiFeO ₃ with low energy level to the conduction band of Bi ₂ WO ₆ with high energy level, while the valence band of Bi ₂ WO ₆ The potential is corrected, and the photogenerated holes can easily migrate from the high-energy Bi ₂ WO ₆ valence band to the low-energy BiFeO ₃ valence band, thereby improving the separation efficiency of the photo-generated electron holes, thereby improving its photocatalytic activity;

2. BiFeO ₃ has a narrow band gap, which can effectively expand the utilization rate of visible light of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst, thereby effectively improving the light utilization rate and photocatalytic activity;

3. BiFeO ₃ itself is magnetic, and the combination of BiFeO ₃ and Bi ₂ WO ₆ makes the Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst also magnetic. It can be quickly separated from the wastewater treatment system by using magnetic separation technology, solving the problem of Photocatalysts are difficult to recycle after use, and have good application prospects.

Description of drawings

Fig. ₁ is a comparison curve of the degradation of rhodamine B by the Bi2WO6 _- BiFeO3 composite photocatalyst prepared in Example _{1 of} the present invention and the pure _Bi2WO6 photocatalyst under the irradiation of a 300W mercury lamp (operating conditions: catalyst The amount: 0.1g; the mass concentration of Rhodamine B: 5mg/L).

detailed description

The above-mentioned contents of the present invention are described in further detail below through the embodiments, but this should not be interpreted as the scope of the above-mentioned themes of the present invention being limited to the following embodiments, and all technologies realized based on the above-mentioned contents of the present invention all belong to the scope of the present invention.

Example 1

(1) Use bismuth nitrate pentahydrate and deionized water as raw materials to prepare 200 mL of bismuth nitrate pentahydrate aqueous solution with a molar concentration of 0.5 mol/L, and add 0.01 mol of ferric nitrate and 0.045 mol of sodium tungstate to the pentahydrate under stirring conditions. A mixed solution is formed in the bismuth nitrate aqueous solution;

(2) Stir the mixed solution obtained in step (1) for 30 minutes, adjust the pH value of the mixed solution to 9 with sodium hydroxide solution, and then continue to stir the mixed solution at room temperature for 1 hour;

(3) Transfer the mixed solution obtained in step (2) to a hydrothermal reaction kettle, then put the hydrothermal reaction kettle into a microwave digestion apparatus and react with microwave at 180°C for 30 minutes, after the reaction is completed, cool, centrifuge, wash and dry Finally, a Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst with high catalytic activity was obtained.

Figure 1 is a comparison curve of the degradation of rhodamine B by the Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst prepared in this example and the pure Bi ₂ WO ₆ photocatalyst under the irradiation of a 300W mercury lamp. Under the irradiation of 80min, the degradation rate of Rhodamine B by pure Bi ₂ WO ₆ photocatalyst is about 56%, while that of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst can reach about 87%. , showing significantly enhanced photocatalytic activity.

Example 2

(1) Use bismuth nitrate pentahydrate and deionized water as raw materials to prepare 200 mL of bismuth nitrate pentahydrate aqueous solution with a molar concentration of 0.8 mol/L, and add 0.032 mol of ferric nitrate and 0.064 mol of sodium tungstate to the pentahydrate under stirring conditions. A mixed solution is formed in the bismuth nitrate aqueous solution;

(2) Stir the mixed solution obtained in step (1) for 30 minutes, adjust the pH value of the mixed solution to 10 with sodium hydroxide solution, and then continue to stir the mixed solution at room temperature for 1 hour;

(3) Transfer the mixed solution obtained in step (2) to a hydrothermal reaction kettle, then put the hydrothermal reaction kettle into a microwave digestion apparatus and react with microwave at 180°C for 20 minutes, after the reaction is completed, cool, centrifuge, wash and dry Finally, a Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst with high catalytic activity was prepared.

Example 3

(1) Use bismuth nitrate pentahydrate and deionized water as raw materials to prepare 200 mL of bismuth nitrate pentahydrate aqueous solution with a molar concentration of 1 mol/L, and add 0.06 mol of ferric nitrate and 0.07 mol of sodium tungstate to pentahydrate under stirring conditions A mixed solution is formed in the bismuth nitrate aqueous solution;

(2) Stir the mixed solution obtained in step (1) for 30 minutes, then adjust the pH value of the mixed solution to 11 with sodium hydroxide solution, and then continue to stir the mixed solution at room temperature for 1 hour;

(3) Transfer the mixed solution obtained in step (2) to a hydrothermal reaction kettle, then put the hydrothermal reaction kettle into a microwave digestion apparatus and react with microwave at 180°C for 10 minutes, after the reaction is completed, cool, centrifuge, wash, After drying, a Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst with high catalytic activity was obtained.

The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What are described in the above embodiments and description are only to illustrate the principles of the present invention. Without departing from the scope of the principle of the present invention, there will be various changes and improvements in the present invention, and these changes and improvements all fall within the protection scope of the present invention.

Claims (4)

1. A preparation method of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst, it is characterized in that comprising the following steps: (1) take bismuth nitrate pentahydrate and deionized water as raw material preparation bismuth nitrate aqueous solution, under stirring condition Add ferric nitrate and sodium tungstate to bismuth nitrate pentahydrate aqueous solution to form a mixed solution, wherein the molar ratio of ferric nitrate to bismuth nitrate pentahydrate is 0.1-0.3:1; (2) mix the obtained After stirring the solution for 30 minutes, adjust the pH value of the mixed solution to 9-11 with an alkali solution, and then continue to stir the mixed solution at room temperature for 1 hour; (3) transfer the mixed solution obtained in step (2) to a hydrothermal reaction kettle, and then Put the hydrothermal reaction kettle into a microwave digestion apparatus and react with microwave at 180°C for 10-30min. After the reaction is completed, the magnetic Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst is prepared by cooling, centrifuging, washing and drying. 2. The preparation method of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst according to claim 1, characterized in that the molar concentration of the bismuth nitrate pentahydrate aqueous solution in step (1) is 0.5-1 mol/L. 3. The preparation method of Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst according to claim 1, characterized in that: the alkali solution in step (2) is sodium hydroxide solution. 4. A Bi ₂ WO ₆ -BiFeO ₃ composite photocatalyst, characterized in that it is prepared according to the method described in any one of claims 1-3.