CN107983336A - A kind of praseodymium doped bismuth tungstate light urges agent and preparation method thereof - Google Patents

Abstract

The invention discloses a praseodymium-doped bismuth tungstate photocatalyst and a preparation method thereof. It is a three-dimensional flower-like structure formed by lamellar accumulation. The thickness of the lamellar layer is 50-80nm. The diameter of the flower-like particles is 2-4um. Its crystal structure is an orthorhombic phase. Its preparation method is to dissolve bismuth nitrate in nitric acid solution In the process, seal and stir to obtain bismuth nitrate acidic solution; add sodium tungstate solution dropwise into bismuth nitrate acidic solution, seal and stir to obtain a mixed solution, then dissolve praseodymium nitrate in the mixed solution, seal and stir; Transfer to a high-pressure reactor, keep warm at 120-200°C, cool naturally to room temperature, then filter and centrifuge, wash with absolute ethanol, and dry at 60-80°C. The invention has low cost, good consistency of the obtained product, no need to add additional surfactant, and the obtained praseodymium-doped bismuth tungstate product has a three-dimensional flower-like structure formed by lamellar stacking, has good dispersibility and has visible light catalytic effect.

Description

A kind of praseodymium-doped bismuth tungstate photocatalyst and preparation method thereof

technical field

The invention relates to a praseodymium-doped bismuth tungstate photocatalyst and a preparation method thereof, belonging to the technical field of photocatalysis.

Background technique

Bi ₂ WO ₆ bismuth tungstate is an Aurivillius-type oxide with a layered structure, and its atomic layers are compact and easy to form a regular sheet structure. Its forbidden band is narrow, about 2.7eV, and it can be excited by absorbing part of visible light. It has high application value in the fields of pollutant degradation and new energy development. Moreover, the bismuth tungstate photocatalytic material has good stability and no toxic side effects. It is an environmentally friendly material and has received extensive attention in the field of photocatalytic materials in recent years. However, Bi ₂ WO ₆ has a narrow visible light response range, easy recombination of photogenerated electrons and holes, and short lifetime of photogenerated carriers. Therefore, the photocatalytic efficiency still has a certain gap compared with the developed TiO ₂ and other systems. The catalytic ability of the Bi ₂ WO ₆ photocatalytic system has been improved to a certain extent by changing its morphology and particle size by using catalyst compounding and adding surfactants. However, the composite method increases the production cost of the catalyst, and the method of adding a surfactant is not easy to control the final shape of the product. Therefore, a bismuth tungstate nanopowder with a simple preparation process, uniform microstructure and good dispersion is developed to improve its optical properties. Catalytic efficiency plays a positive role in promoting the long-term development of bismuth tungstate in the field of photocatalysis.

Contents of the invention

In view of this, the object of the present invention is to provide a kind of raw material that utilizes bismuth nitrate, sodium tungstate and praseodymium nitrate, the preparation process is simple, the preparation process does not need to add surfactant, does not need to compound other types of catalysts, and obtains uniform structure and good dispersion. Rare earth doped Bi ₂ WO ₆ photocatalyst, the obtained product has good crystallinity and visible light catalytic activity.

In order to realize the above-mentioned invention object, a kind of praseodymium-doped bismuth tungstate photocatalyst of the present invention, it is the three-dimensional flower-like structure that lamellar accumulation forms, and the thickness of sheet is 50-80nm, and the diameter of flower-like particle is 2 -4um, its crystal structure is an orthorhombic phase, and the doping concentration of praseodymium is 0.5-10%.

A kind of preparation method of praseodymium doped bismuth tungstate photocatalyst, it is the following steps:

(1) Dissolve 200-500 μL of nitric acid in 20-60 mL of deionized water, seal and stir for 10-30 minutes to obtain a nitric acid solution, dissolve 0.5-2.0 g of Bi(NO ₃ ) ₃ ·5H ₂ O in the nitric acid solution, seal and Stir for 10 to 30 minutes to obtain an acidic solution of bismuth nitrate;

(2) Dissolve 0.5 to 2.0 grams of Na ₂ WO ₄ ·2H ₂ O in 20 to 60 mL of deionized water, stir for 10 to 30 minutes to obtain a sodium tungstate solution, and add the sodium tungstate solution dropwise to the bismuth nitrate acidic solution, Seal and stir for 10-30 minutes to obtain a mixed solution, then dissolve 0.01-0.03 g of Pr(NO ₃ ) ₃ ·6H ₂ O in the mixed solution, seal and stir for 10-30 minutes;

(3) Transfer the solution obtained in step (2) to a high-pressure reactor, keep it warm at 120-200°C for 12-24 hours, cool down to room temperature naturally, then filter and centrifuge, and then wash with absolute ethanol for 3-5 times. Dry at 60-80°C for 6-12 hours.

The invention utilizes a hydrothermal method to synthesize a flower-like praseodymium-doped bismuth tungstate preparation method formed by lamellar stacking. The preparation process does not require surfactants, and the prepared bismuth tungstate has good crystallinity and visible light catalysis active. By doping with rare earth element Pr, without affecting the morphology of bismuth tungstate catalyst, bismuth tungstate with uniform structure, good dispersion and visible light catalytic effect can be obtained without adding additional surfactant. The method also has the advantages of low cost and good repeatability.

Compared with the prior art, the present invention has the following beneficial effects: the present invention has low cost, good product consistency, no additional surfactant is needed in the preparation process, and the finally obtained praseodymium-doped bismuth tungstate photocatalyst is lamellar stacked The resulting flower-like structure has good dispersion and photocatalytic effect.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) figure of the praseodymium-doped bismuth tungstate catalyst prepared in embodiment 1, 2, wherein a is the X-ray diffraction (XRD) figure of the praseodymium-doped bismuth tungstate prepared in embodiment 1 , b is the X-ray diffraction (XRD) pattern of the praseodymium-doped bismuth tungstate prepared in Example 2.

Fig. 2 is a scanning electron micrograph of praseodymium-doped bismuth tungstate prepared in Example 1 of the present invention, wherein a is a scanning electron micrograph enlarged 5000 times, and b is a scanning electron micrograph enlarged 20000 times.

3 is an energy spectrum diagram of the praseodymium-doped bismuth tungstate prepared in Example 1.

Fig. 4 is a scanning electron microscope photo of praseodymium-doped bismuth tungstate prepared in Example 2, wherein a is a scanning electron microscope photo magnified 5000 times, and b is a scanning electron micrograph photo magnified 20000 times.

Fig. 5 is the graph that praseodymium-doped bismuth tungstate prepared in the present invention embodiment 1, 2 catalytic methyl orange degradation under visible light condition, wherein a is the degradation graph of embodiment 1, b is the degradation curve of embodiment 2 picture.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

A kind of praseodymium-doped bismuth tungstate photocatalyst of the present invention, it is the three-dimensional flower-like structure that lamellar accumulation forms, and the thickness of sheet is 50-80nm, and the diameter of flower-like particle is 2-4um, and its crystal structure is In the orthorhombic phase, the doping concentration of praseodymium is 0.5-10%.

A kind of preparation method of praseodymium doped bismuth tungstate photocatalyst, it is the following steps:

(1) Dissolve 200-500 μL of nitric acid in 20-60 mL of deionized water, seal and stir for 10-30 minutes to obtain a nitric acid solution, dissolve 0.5-2.0 g of Bi(NO ₃ ) ₃ ·5H ₂ O in the nitric acid solution, seal and Stir for 10 to 30 minutes to obtain an acidic solution of bismuth nitrate;

(2) Dissolve 0.5 to 2.0 grams of Na ₂ WO ₄ ·2H ₂ O in 20 to 60 mL of deionized water, stir for 10 to 30 minutes to obtain a sodium tungstate solution, and add the sodium tungstate solution dropwise to the bismuth nitrate acidic solution, Seal and stir for 10-30 minutes to obtain a mixed solution, then dissolve 0.01-0.03 g of Pr(NO ₃ ) ₃ ·6H ₂ O in the mixed solution, seal and stir for 10-30 minutes;

(3) Transfer the solution obtained in step (2) to a high-pressure reactor, keep it warm at 120-200°C for 12-24 hours, cool down to room temperature naturally, then filter and centrifuge, and then wash with absolute ethanol for 3-5 times. Dry at 60-80°C for 6-12 hours.

Example 1

(1) Dissolve 200 μL of nitric acid in 30 ml of deionized water, seal and stir for 30 minutes;

(2) 1.0 g of Bi(NO ₃ ) ₃ ·5H ₂ O was dissolved in the solution obtained in step (1), sealed and stirred for 30 minutes;

(3) Dissolve 0.6 g of Na ₂ WO ₄ ·2H ₂ O in 30 ml of deionized water, and stir for 20 minutes;

(4) Add the solution obtained in step (3) dropwise to the solution obtained in step (2), seal and stir for 15 minutes;

(5) 0.01 g of Pr(NO ₃ ) ₃ 6H ₂ O was dissolved in the solution obtained in step (4), sealed and stirred for 30 minutes;

(6) The solution obtained in step (5) was transferred to an autoclave, kept at 180° C. for 12 hours, and cooled naturally to room temperature.

(7) The reaction product was filtered, centrifuged, washed 4 times with absolute ethanol, and dried at 60° C. for 8 hours.

As shown in Fig. 1(a), it is the XRD pattern of the dried praseodymium-doped bismuth tungstate sample in this embodiment. By comparing the PDF standard card, it is found that the bismuth tungstate prepared in this example matches the orthorhombic phase bismuth tungstate whose card number is No. 39-0256. And there is no diffraction peak of praseodymium element or praseodymium compound in the figure, indicating that Pr ions have entered the BiNa ₂ WO ₆ lattice.

Fig. 2 is an SEM image of the praseodymium-doped bismuth tungstate sample obtained in this embodiment. It can be seen from the figure that the samples are stacked by lamellar structures to form a three-dimensional flower-like structure. It can be seen from the enlarged view of Figure 2(b) that the thickness of the sheet is 50-80nm, and the diameter of the flower-like particles is 2-4um.

Fig. 3 is an energy spectrum analysis diagram of the praseodymium-doped bismuth tungstate sample obtained in this embodiment. There is an obvious peak of Pr element in the figure, indicating that the sample prepared in this embodiment contains Pr.

Example 2

(1) Dissolve 200 μL of nitric acid in 30 ml of deionized water, seal and stir for 30 minutes;

(2) 1.0 g of Bi(NO ₃ ) ₃ ·5H ₂ O was dissolved in the solution obtained in step (1), sealed and stirred for 30 minutes;

(3) Dissolve 0.6 g of Na ₂ WO ₄ ·2H ₂ O in 30 ml of deionized water, and stir for 20 minutes;

(4) Add the solution obtained in step (3) dropwise to the solution obtained in step (2), seal and stir for 15 minutes;

(5) 0.02 gram of Pr(NO3)3.6H2O was dissolved in the solution obtained in step (4), sealed and stirred for 30 minutes;

(6) The solution obtained in step (5) was transferred to an autoclave, kept at 200° C. for 12 hours, and cooled naturally to room temperature.

(7) The reaction product was filtered, centrifuged, washed 4 times with absolute ethanol, and dried at 60° C. for 8 hours.

(8) Add 30 mg of sample to a quartz tube with 250 ml of 10 mg/L methyl orange solution. Stir for 30 min in the dark to allow adsorption equilibrium. Turn on the 300W xenon lamp and keep stirring to carry out visible light catalytic degradation. Take the solution every 20 minutes, centrifuge, separate, and test the absorbance of the supernatant. The degradation rate of catalyst to methyl orange is calculated according to the following formula:

In the formula, C and C ₀ are the absorbance of methyl orange before and after degradation, respectively.

As shown in FIG. 1( b ), it is the XRD pattern of the dried praseodymium-doped bismuth tungstate sample in this embodiment. By comparing the PDF standard card, it is found that the bismuth tungstate prepared in this example matches No.39-0256. And there is no diffraction peak of praseodymium element or praseodymium compound in the figure, indicating that Pr ions enter the lattice of bismuth tungstate.

Fig. 4 is an SEM image of the praseodymium-doped bismuth tungstate sample obtained in this embodiment. It can be seen from the figure that the samples are stacked by lamellar structures to form a three-dimensional flower-like structure. It can be seen from the enlarged view of Figure 2(b) that the thickness of the sheet is 50-80nm, and the diameter of the flower-like particles is 2-4um.

Fig. 5 is the praseodymium doped bismuth tungstate obtained with embodiment 1, 2, under the condition of visible light to the degradation curve figure of methyl orange, under the photocatalysis of praseodymium doped bismuth tungstate, after 2 hours, the degradation curve of methyl orange The degradation efficiency reaches more than 90%, and the degradation efficiency of the praseodymium-doped bismuth tungstate obtained in Example 1 to methyl orange reaches 95% after 2 hours. It shows that the prepared praseodymium doped bismuth tungstate has good visible light catalytic activity.

Example 3

A praseodymium-doped bismuth tungstate photocatalyst, which is composed of a three-dimensional flower-like structure formed by lamellar stacking, the thickness of the flakes is 55nm, the diameter of the flower-like particles is 2.5um, and its crystal structure is an orthorhombic phase, and the praseodymium The doping concentration is 1.5%.

A kind of preparation method of praseodymium doped bismuth tungstate photocatalyst, it is the following steps:

(1) Dissolve 400 μL of nitric acid in 40 mL of deionized water, seal and stir for 25 minutes to obtain a nitric acid solution, dissolve 1.5 grams of Bi(NO3)3·5H2O in the nitric acid solution, seal and stir for 25 minutes to obtain an acidic solution of bismuth nitrate;

(2) Dissolve 1.5 grams of Na ₂ WO ₄ 2H ₂ O in 30 mL of deionized water, stir for 20 minutes to obtain a sodium tungstate solution, add the sodium tungstate solution dropwise to the bismuth nitrate acidic solution, seal and stir for 20 minutes to obtain a mixed solution, and then 0.021 g of Pr(NO ₃ ) ₃ 6H ₂ O was dissolved in the mixed solution, sealed and stirred for 20 min;

(3) The solution obtained in step (2) was transferred to an autoclave, kept at 180°C for 20h, cooled to room temperature naturally, then filtered and centrifuged, washed 4 times with absolute ethanol, and dried at 70°C for 10h.

Example 4

A praseodymium-doped bismuth tungstate photocatalyst, which is composed of a three-dimensional flower-like structure formed by layer stacking, the thickness of the layer is 70nm, the diameter of the flower-like particles is 3.2um, and its crystal structure is an orthorhombic phase, praseodymium The doping concentration is 5%.

A kind of preparation method of praseodymium doped bismuth tungstate photocatalyst, it is the following steps:

(1) Dissolve 400 μL of nitric acid in 40 mL of deionized water, seal and stir for 20 min to obtain a nitric acid solution, dissolve 1.2 g of Bi(NO ₃ ) ₃ 5H ₂ O in the nitric acid solution, seal and stir for 20 min to obtain an acidic solution of bismuth nitrate ;

(2) Dissolve 1.3 grams of Na ₂ WO ₄ ·2H ₂ O in 40 mL of deionized water, stir for 20 minutes to obtain a sodium tungstate solution, add the sodium tungstate solution dropwise to the bismuth nitrate acidic solution, seal and stir for 20 minutes to obtain a mixed solution, and then 0.02 g of Pr(NO ₃ ) ₃ 6H ₂ O was dissolved in the mixed solution, sealed and stirred for 20 min;

(3) The solution obtained in step (2) was transferred to an autoclave, kept at 180°C for 21h, cooled to room temperature naturally, then filtered and centrifuged, washed 5 times with absolute ethanol, and dried at 72°C for 10h.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (2)

1. a kind of praseodymium-doped bismuth tungstate photocatalyst is characterized in that, it is the three-dimensional flower-like structure that lamellar accumulation forms, and the thickness of sheet is 50-80nm, and the diameter of flower-like particle is 2-4um, and its The crystal structure is an orthorhombic phase, and the doping concentration of praseodymium is 0.5-10%. 2. a preparation method of praseodymium-doped bismuth tungstate photocatalyst, is characterized in that, is the following steps: (1) Dissolve 200-500 μL of nitric acid in 20-60 mL of deionized water, seal and stir for 10-30 minutes to obtain a nitric acid solution, dissolve 0.5-2.0 g of Bi(NO ₃ ) ₃ ·5H ₂ O in the nitric acid solution, seal and Stir for 10 to 30 minutes to obtain an acidic solution of bismuth nitrate; (2) Dissolve 0.5 to 2.0 grams of Na ₂ WO ₄ ·2H ₂ O in 20 to 60 mL of deionized water, stir for 10 to 30 minutes to obtain a sodium tungstate solution, and add the sodium tungstate solution dropwise to the bismuth nitrate acidic solution, Seal and stir for 10-30 minutes to obtain a mixed solution, then dissolve 0.01-0.03 g of Pr(NO ₃ ) ₃ ·6H ₂ O in the mixed solution, seal and stir for 10-30 minutes; (3) Transfer the solution obtained in step (2) to a high-pressure reactor, keep it warm at 120-200°C for 12-24 hours, cool down to room temperature naturally, then filter and centrifuge, and then wash with absolute ethanol for 3-5 times. Dry at 60-80°C for 6-12 hours.