Bi-guided controllable flower-like hetero-photocatalyst and preparation method thereof

Abstract

The application discloses a Bi-guided controllable flower-shaped heterojunction photocatalyst and a preparation method thereof. By using a double bismuth source and a reducing agent, Bi element is introduced to control Bi2O2CO3 powder, and residual -OH on the surface of the Bi2O2CO3 powder is introduced, then a halogenating agent is added to guide the growth and construction of a composite ternary heterojunction structure. The introduction of Bi can maintain the stable flower-shaped structure of the powder, promote the crystal growth of BiOCl, regulate the proportion of each crystal phase in the heterojunction catalyst to obtain a more effective heterojunction structure, and regulate the morphology to expose the gap of the lamella of the composite powder, effectively improve the active sites and defects, and improve the photocatalytic activity. The method is simple in preparation process, the prepared powder is stable in structure, and the photocatalytic activity of the powder is improved by introducing a heterojunction and a metal element.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalyst materials, and particularly relates to a Bi-guided controllable flower-shaped heterojunction photocatalyst and a preparation method thereof. BACKGROUND

[0002] Bismuth semiconductor photocatalysts have excellent performance in degrading organic dyes due to their structural and crystalline characteristics, and have attracted widespread attention. BiOCl and Bi2O2CO3 are both bismuth photocatalysts, and both have a large band gap, which makes their photocatalytic performance not ideal. Common modification methods for the above materials include constructing heterojunctions, surface modification, metal deposition, etc. However, the introduction of metals in the current photocatalyst mainly plays a general role of electron traps and carrier channels, and cannot affect the morphology and heterostructure of the photocatalyst, limiting the improvement of its catalytic performance. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a Bi-guided controllable flower-shaped heterojunction photocatalyst and a preparation method thereof. The method is simple, the prepared powder has good dispersibility, stable structure, and the prepared powder contains heterojunctions, metal elements and surface defects to improve the photocatalytic performance of the powder. The existence of double bismuth sources in the powder preparation process can maintain the three-dimensional flower-like microstructure without being destroyed, so that the spatial structure is stable. Bi element is generated in the reduction reaction, and -OH is left on the surface of Bi2O2CO3, which promotes the growth of BiOCl and the proportion of catalyst components, exposes more gaps between the layers, introduces defects, and increases the active sites.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0005] A preparation method of a Bi-guided controllable flower-shaped heterojunction photocatalyst, comprising the following steps:

[0006] Step 1: preparing pure-phase Bi2O2CO3 powder by a solvothermal method;

[0007] Step 2: preparing Bi / Bi2O2CO3 powder by using Bi(NO3)3·5H2O, a reducing agent and pure-phase Bi2O2CO3 powder;

[0008] Step 3: preparing a composite heterojunction BiOCl / Bi / Bi2O2CO3 ternary photocatalyst by ion exchange of Bi / Bi2O2CO3 powder in a halide salt solution.

[0009] In one embodiment, the precursor solution used to prepare Bi2O2CO3 in step 1 is placed in a stainless steel sealed autoclave lined with polytetrafluoroethylene, and is incubated at 170-190°C for 10-12 hours, and then cooled to room temperature; the product is collected by centrifugation, and is washed several times with deionized water and anhydrous ethanol alternately, and then dried in an oven at 60-80°C for 10-14 hours, and ground to obtain pure-phase Bi2O2CO3 powder.

[0010] In one embodiment, the precursor solution is obtained by the following method:

[0011] 0.4-0.5 g Bi(NO3)3·5H2O is dissolved in 30-40 mL deionized water, and then 0.8-0.9 g sodium citrate, 0.2-0.3 g urea and 0.4-0.5 g polyvinylpyrrolidone are added in sequence, and stirred for 40-50 min to obtain.

[0012] In one embodiment, the filling ratio in the sealed autoclave is 40-50%.

[0013] In one embodiment, in step 2, Bi(NO3)3·5H2O and pure-phase Bi2O2CO3 powder are added to a reducing agent at a molar ratio of 1:1-3:2, and the mixture is stirred for 1-2 hours, and the uniformly mixed solution is transferred to a hydrothermal kettle lined with polytetrafluoroethylene, and the hydrothermal temperature is 150-170°C, and the hydrothermal time is 8-12 hours; the obtained sample is collected, washed with water and alcohol alternately, dried in an oven at 50-80°C, and ground to obtain Bi / Bi2O2CO3 powder.

[0014] In one embodiment, the reducing agent is methanol, ethylene glycol or glycerol; in step 2, Bi(NO3)3·5H2O and Bi2O2CO3 as a double-bismuth source react with the reducing agent to generate elemental bismuth, avoiding excessive reaction of the reducing agent with Bi2O2CO3 to destroy the original flower-like morphology of the powder.

[0015] In one embodiment, in step 3, 0.2-0.3 g Bi / Bi2O2CO3 powder is mixed with 20-30 mL deionized water, and stirred in a water bath at 25-35°C for 1-2 hours; then 20-30 mg CTAC is added; then 3-5 mL of a 1.3 mol / L halide salt solution is added dropwise, and stirring is continued for 20-40 min; the product is collected, washed with deionized water and anhydrous ethanol alternately and centrifuged, and then dried in an oven at 60-80°C for 10-14 hours, and ground to obtain three-dimensional flower-like composite hetero BiOCl / Bi / Bi2O2CO3 powder.

[0016] In one embodiment, the halide salt solution is a lithium chloride solution, and in the step 3, the halide salt solution and Bi2O2CO3 undergo an ion exchange reaction, so that part of Bi2O2CO3 is converted into BiOCl, thereby generating the ternary hetero-composite photocatalyst.

[0017] The application also claims the Bi-guided controllable flower-shaped hetero-photocatalyst prepared by the above preparation method.

[0018] The Bi-guided controllable flower-shaped hetero-photocatalyst can be used as a catalyst for purifying water bodies, and degrading pollutants such as rhodamine B and tetracycline hydrochloride in polluted water bodies. Experiments show that the degradation rate of the Bi-guided controllable flower-shaped hetero-photocatalyst to organic dyes such as rhodamine B reaches 95%, and the degradation rate to antibiotics such as tetracycline hydrochloride reaches 75%.

[0019] Compared with the prior art, the Bi-guided controllable flower-shaped hetero-photocatalyst has the following beneficial effects:

[0020] 1. In the process of forming elemental Bi on the basis of Bi2O2CO3, the added Bi(NO3)3·5H2O and the Bi2O2CO3 base powder can be used as a double-bismuth source to participate in the reduction reaction. The reducing agent tends to reduce Bi(NO3)3·5H2O first, and then reduce a small part of Bi2O2CO3, so that the structure after reduction maintains a stable three-dimensional flower-shaped structure, avoiding the destruction of the structure after excessive reduction. On this basis, a halogenating agent is added to synthesize a BiOCl / Bi / Bi2O2CO3 hetero-photocatalyst. The final photocatalyst morphology is mostly a sheet layer stacking flower-shaped structure. The small Bi elemental particles in the structure and the multi-sheet layer stacking structure are conducive to the penetration of pollutants into the interior of the catalyst, promoting the adsorption of pollutants. When reducing Bi, the residual -OH on the surface of Bi2O2CO3 and Bi jointly affect the growth of BiOCl and the proportion of the crystal phase. More oxygen vacancies and active sites are formed on the multi-sheet layer stacking flower-shaped structure with a larger area, which is helpful for the adsorption and degradation of the photocatalytic reaction.

[0021] 2. When Bi2O2CO3 in the ternary hetero-system is converted into BiOCl, it will be affected by the residual -OH on the surface of Bi2O2CO3 and Bi, which will regulate the proportion between the two phases and form a BiOCl / Bi / Bi2O2CO3 heterostructure. The [Bi2O2] 2+ unit layer is generated before the crystal phase conversion, which can increase the contact between Bi and the hetero-interface, and make Bi exist in the sheet layer. It can be regarded as a convenient "channel" for photo-generated carriers, which is more conducive to the separation and transmission of photo-generated carriers, and improves the photocatalytic performance.

[0022] 3. The preparation method of the application is simple, the reaction process is carried out under neutral conditions, the prepared powder has good dispersibility, and has good ability to degrade organic dyes and part of antibiotics. Attached Figure Description

[0023] Figure 1 This is a SEM image of a Bi-guided controllable flower-like heterogeneous photocatalyst.

[0024] Figure 2 This is a photocatalytic degradation curve of Rhodamine B by a Bi-guided controllable flower-like heterogeneous photocatalyst. Detailed Implementation

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0026] A method for preparing a Bi-guided controllable flower-like heterogeneous photocatalyst involves preparing pure-phase Bi2O2CO3 powder by a solvothermal method, then adding bismuth nitrate pentahydrate and a reducing agent to prepare Bi / Bi2O2CO3 powder, and finally preparing a composite heterogeneous BiOCl / Bi / Bi2O2CO3 ternary photocatalyst through ion exchange in a halide solution.

[0027] Specifically, it may include the following steps:

[0028] Step 1): The precursor solution used to prepare Bi2O2CO3 is placed in a stainless steel sealed autoclave lined with polytetrafluoroethylene and kept at 170℃~190℃ for 10~12 hours, then cooled to room temperature; the filling ratio in the sealed autoclave is between 40% and 70%. The product is collected and centrifuged, and washed several times alternately with deionized water and anhydrous ethanol, then dried in an oven at 60℃~80℃ for 10~14 hours, and ground to obtain pure phase Bi2O2CO3 powder. The precursor solution of this invention is prepared by dissolving 0.4~0.5g Bi(NO3)3·5H2O in 30mL~40mL of deionized water. Subsequently, 0.8g~0.9g sodium citrate, 0.2g~0.3g urea, and 0.4g~0.5g polyvinylpyrrolidone are added sequentially, and the mixture is stirred for 40~50min.

[0029] This step yielded pure-phase Bi2O2CO3 powder, which exhibits a flower-like structure with a size of approximately 1 μm, composed of fine 2D nanosheets assembled together. Its size and morphology are relatively stable.

[0030] Step 2), Bi(NO3)3.5H2O and Bi2O2CO3 are added to the reducing agent in a molar ratio of 1:1 to 3:2, stirred for 1 to 2 hours, and the uniformly mixed solution is transferred to a hydrothermal kettle lined with polytetrafluoroethylene, the hydrothermal temperature is 150 to 170 DEG C, and the hydrothermal time is 8 to 12 hours. The obtained sample is collected, washed several times with water-alcohol alternately, dried in an oven at 50 to 80 DEG C, and ground to obtain Bi / Bi2O2CO3 powder. The reducing agent can be methanol, ethylene glycol or glycerol, etc. Taking the material amount of the precursor solution in step 1 as an example, the amount of the reducing agent in this step is generally about 25 mL.

[0031] In the process of this step, by using Bi(NO3)3.5H2O and Bi2O2CO3 as double bismuth sources, the reducing agent is reacted to generate elemental bismuth, which can control the Bi2O2CO3 powder and the residual -OH on the surface of the Bi2O2CO3 powder, avoiding excessive reaction of the reducing agent with the Bi2O2CO3 to destroy the original flower-like morphology of the powder.

[0032] Step 3), 0.2 to 0.3 g of Bi / Bi2O2CO3 powder is mixed with 20 to 30 mL of deionized water, stirred in a water bath at 25 to 35 DEG C for 1 to 2 hours, then 20 to 30 mg of CTAC is added, stirred for 20 to 40 min, then 3 to 5 mL of 1.3 mol / L lithium chloride solution is added dropwise, and stirring is continued for 20 to 40 min. The product is collected, washed several times with deionized water and anhydrous ethanol alternately and centrifuged, then dried in an oven at 60 to 80 DEG C for 10 to 14 hours, and ground to obtain a three-dimensional flower-like composite heterostructure BiOCl / Bi / Bi2O2CO3 powder.

[0033] In the process of this step, the halogenating agent can guide the growth and construction of the composite ternary heterostructure. Specifically, the lithium chloride solution reacts with Bi2O2CO3 to exchange ions, so that part of Bi2O2CO3 is converted to BiOCl, thereby generating a ternary heterostructure photocatalyst.

[0034] In the present application, the introduction of Bi can maintain the flower-like stable structure of the powder, promote the crystal growth of BiOCl, regulate the proportion of each crystal phase in the heterostructure catalyst to obtain a more effective heterostructure, and control the morphology to expose the gap between the layers of the composite powder, effectively improve the active sites and defects, and improve the photocatalytic activity. The preparation process is simple, the prepared powder has stable structure, and the introduction of heterojunction and metal elements improves the photocatalytic activity of the powder.

[0035] The following are several embodiments of the present application.

[0036] Example 1

[0037] Step 1), the white precursor solution used to prepare Bi2O2CO3 was placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and incubated at 180°C for 12 hours, and then naturally cooled to room temperature; the product was collected by centrifugation, and washed with deionized water and anhydrous ethanol alternately for 6 times, and then dried in an oven at 70°C for 10 hours, and ground to obtain pure phase Bi2O2CO3 powder. The precursor solution was prepared by dissolving 0.485g Bi(NO3)3·5H2O in 30mL deionized water. Then 0.88g sodium citrate, 0.24g urea, and 0.5g polyvinylpyrrolidone were added in sequence, and stirred for 45min.

[0038] Step 2), Bi(NO3)3·5H2O and Bi2O2CO3 were added to 25mL of ethylene glycol in a molar ratio of 3:2, and stirred for 1 hour, wherein the amount of Bi2O2CO3 was 0.51g, and the uniform solution was transferred to a hydrothermal kettle lined with polytetrafluoroethylene, and the hydrothermal temperature was 160°C, and the hydrothermal time was 10 hours. The obtained product was collected, washed with deionized water and anhydrous ethanol alternately for 6 times, dried in an oven at 70°C for 10 hours, and ground to obtain Bi / Bi2O2CO3 powder. In this process, Bi(NO3)3·5H2O and Bi2O2CO3 as double bismuth sources reacted with ethylene glycol to generate elemental bismuth, avoiding excessive reaction of ethylene glycol with Bi2O2CO3 to destroy the original flower-like morphology of the powder.

[0039] Step 3), 0.25g Bi / Bi2O2CO3 powder was mixed with 30mL deionized water in a 30°C water bath, and stirred for 1 hour; then 25mg CTAC was added, and stirred for 20min; then 4mL of 1.3mol / L lithium chloride solution was added dropwise, and stirred for 30min; the product was collected, washed with water and alcohol alternately, and centrifuged for 6 times, and then dried in an oven at 70°C for 12 hours, and ground to obtain three-dimensional flower-like composite heterostructure BiOCl / Bi / Bi2O2CO3 powder. In this process, the lithium chloride solution reacted with Bi2O2CO3 by ion exchange, so that part of Bi2O2CO3 was converted to BiOCl, thereby generating a Bi-guided controllable flower-like heterostructure photocatalyst.

[0040] Reference Figure 1 The composite heterostructure BiOCl / Bi / Bi2O2CO3 powder prepared according to the example step 1) has a three-dimensional flower-like morphology, and the morphology is not destroyed, maintaining the spatial stability. The heterostructure and metal elements in the powder can improve the photocatalytic performance.

[0041] Reference Figure 2photocatalytic degradation experiment. The concentration of Rhodamine B in the experiment was 10 mg / L. The photocatalytic test process was that 30 mL of Rhodamine B solution was stirred with 30 mg of the photocatalyst in the dark for 30 min, and 3 mL of the suspension was taken every 15 min for centrifugation. Then a 500W xenon lamp was used as a light source to irradiate the target pollutants, and the suspension was taken every 20 min for centrifugation, and the light reaction was carried out in an environment at 25°C. During the process, a centrifuge at 11000 r / min was used for centrifugation for 3 min, and the supernatant was moved to a cuvette, and the concentration of the pollutants was quantitatively measured by using a UV-visible spectrophotometer. The target pollutant Rhodamine B can be degraded by 99% within 60 min, and has a good photocatalytic degradation effect.

[0042] The application uses a similar method, and the target pollutant Rhodamine B is replaced by 40 mg / L of tetracycline hydrochloride, and other experimental conditions remain unchanged. The results show that the degradation rate of tetracycline hydrochloride and other antibiotics reaches 80%.

[0043] Example 2

[0044] Step 1), the white precursor solution for preparing Bi2O2CO3 was placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and was incubated at 180°C for 12 hours, and then was naturally cooled to room temperature; the product was collected and centrifuged, and was washed with deionized water and anhydrous ethanol alternately for 6 times, and then was dried in an oven at 70°C for 10 hours, and was ground to obtain pure phase Bi2O2CO3 powder. The precursor solution was prepared by dissolving 0.485 g of Bi(NO3)3·5H2O in 30 mL of deionized water. Then 0.88 g of sodium citrate, 0.24 g of urea and 0.5 g of polyvinylpyrrolidone were sequentially added, and stirring was performed for 45 min.

[0045] Step 2), Bi(NO3)3·5H2O and Bi2O2CO3 were added to 25 mL of glycerol reducing agent in a molar ratio of 1:1 and stirred for 1 hour, wherein the amount of Bi2O2CO3 was 0.51 g, and the uniformly mixed solution was transferred to a hydrothermal kettle lined with polytetrafluoroethylene, the hydrothermal temperature was 160°C, and the hydrothermal time was 10 hours. The obtained product was collected, washed with deionized water and anhydrous ethanol alternately for 6 times, dried in an oven at 70°C for 10 hours, and ground to obtain Bi / Bi2O2CO3 powder. In this process, Bi(NO3)3·5H2O and Bi2O2CO3 as double bismuth sources react with glycerol to generate elemental bismuth, avoiding excessive reaction of glycerol with Bi2O2CO3 to destroy the original flower-like morphology of the powder.

[0046] Step 3), 0.25 g of Bi / Bi2O2CO3 powder was mixed with 30 mL of deionized water, and stirred in a water bath at 30℃ for 2 hours; then, 25 mg of CTAC was added, and stirred for 30 min; then, 4 mL of 1.3 mol / L lithium chloride solution was added dropwise, and continued to stir for 30 min; the product was collected by centrifugation, and washed with deionized water and anhydrous ethanol alternately for 6 times, and then dried in an oven at 70℃ for 12 hours, and after grinding, three-dimensional flower-shaped composite heterostructure BiOCl / Bi / Bi2O2CO3 powder was obtained. In this process, the lithium chloride solution and Bi2O2CO3 undergo ion exchange reaction, so that part of Bi2O2CO3 is converted to BiOCl, thereby generating a ternary heterostructure photocatalyst with a stacked morphology of sheet layers.

[0047] In more embodiments of the present application, the aforementioned parameters are combined in different types, for example, the holding temperature and time of the precursor solution in step 1) are respectively selected as the combination of 170℃ / 12 hours, the combination of 190℃ / 10 hours, the combination of 180℃ / 11 hours, etc., the drying temperature is selected as 60℃, 70℃, 80℃, and the time is selected as 10h, 12h, 14h for combination, and the results prove that pure phase Bi2O2CO3 powder can be prepared.

[0048] Similarly, in step 2), the molar ratio of Bi(NO3)3·5H2O to Bi2O2CO3 is also selected as 2:1, 3:2, the hydrothermal temperature is selected as 150℃, 160℃, 170℃, the time is selected as 8h, 10h, 12h, and the drying temperature is selected as 50℃, 60℃, 80℃, and the results prove that Bi / Bi2O2CO3 powder can be prepared.

[0049] Similarly, in step 3), the actual amount of Bi / Bi2O2CO3 powder is also selected as 0.2 g, 0.25 g, 0.3 g, the water bath temperature is selected as 25℃, 30℃, 35℃, the amount of CTAC is selected as 20 mg, 25 mg, 30 mg, the lithium chloride solution is selected as 3 mL, 4 mL, 5 mL, and the drying temperature is selected as 60℃, 70℃, 80℃, and the results prove that three-dimensional flower-shaped composite heterostructure BiOCl / Bi / Bi2O2CO3 powder can be prepared.

[0050] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, substitutions, combinations, simplifications, etc. made on the basis of the principles or spirit of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A method for preparing Bi-guided controllable flower-like hetero-photocatalyst, characterized in that, The method comprises the following steps: Step 1, a pure phase Bi2O2CO3 powder is prepared by a solvothermal method, and the method is as follows: The precursor solution for preparing Bi2O2CO3 is placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and is kept at 170-190 DEG C for 10-12 hours, and then is cooled to room temperature; the product is collected and centrifuged, and is cleaned several times alternately with deionized water and anhydrous ethanol, and then is dried in an oven at 60-80 DEG C for 10-14 hours, and is ground to obtain a pure phase Bi2O2CO3 powder; wherein the precursor solution is obtained by the following method: 0.4-0.5 g of Bi(NO3)3.5H2O is dissolved in 30-40 mL of deionized water, and then 0.8 g-0.9 g of sodium citrate, 0.2 g-0.3 g of urea and 0.4 g-0.5 g of polyvinylpyrrolidone are sequentially added, and stirring is carried out for 40-50 min to obtain; Step 2, Bi / Bi2O2CO3 powder is prepared by using Bi(NO3)3.5H2O, a reducing agent and a pure phase Bi2O2CO3 powder, in the process, Bi(NO3)3.5H2O and Bi2O2CO3 are used as double bismuth sources to react with the reducing agent to generate elemental bismuth, avoiding excessive reaction of the reducing agent with Bi2O2CO3 to destroy the original flower-like morphology of the powder; Step 3, a composite hetero BiOCl / Bi / Bi2O2CO3 ternary photocatalyst is prepared by ion exchange in a halide salt solution by using Bi / Bi2O2CO3 powder, wherein the halide salt solution is a lithium chloride solution, and in the process, the halide salt solution reacts with Bi2O2CO3 by ion exchange, so that part of Bi2O2CO3 is converted into BiOCl, thereby generating a ternary hetero composite photocatalyst.

2. The method for preparing Bi-guided controllable flower-like hetero-photocatalyst according to claim 1, characterized in that, The filling ratio in the sealed autoclave is 40%-50%.

3. The method for preparing the Bi-guided controllable flower-like heterogeneous photocatalyst according to claim 1, characterized in that, In step 2, Bi(NO3)3.5H2O and the pure phase Bi2O2CO3 powder are added to the reducing agent in a molar ratio of 1:1-3:2, and stirring is carried out for 1-2 hours, and the uniformly mixed solution is transferred into a hydrothermal kettle with a polytetrafluoroethylene liner, the hydrothermal temperature is 150-170 DEG C, and the hydrothermal time is 8-12 hours; the obtained sample is collected, cleaned alternately with water and alcohol, dried in an oven at 50-80 DEG C, and ground to obtain Bi / Bi2O2CO3 powder.

4. The preparation method of the Bi-guided controllable flower-like hetero-photocatalyst according to claim 1 or 3, characterized in that, The reducing agent is methanol, ethylene glycol or glycerol.

5. The method for preparing the Bi-guided controllable flower-like heterogeneous photocatalyst according to claim 1, characterized in that, The step 3, 0.2 g~0.3 g Bi / Bi2O2CO3 powder is mixed with 20 mL~30 mL deionized water, stirred in a water bath at 25 ℃~35 ℃ for 1~2 hours; then 20 mg~30 mg CTAC is added; then 3 mL ~ 5 mL 1.3 mol / L halogen salt solution is added dropwise, continue to stir for 20~40 min; the product is collected and washed with deionized water and anhydrous ethanol alternately and centrifuged, then dried in an oven at 60 ℃~80 ℃ for 10~14 hours, ground to obtain three-dimensional flower-like composite heterostructure BiOCl / Bi / Bi2O2CO3 powder.

6. The Bi-guided controllable flower-like heterostructure photocatalyst prepared by the preparation method of any one of claims 1 to 5.

7. The application of the Bi-guided controllable flower-like heterostructure photocatalyst of claim 6 as a catalyst for degrading rhodamine B or tetracycline hydrochloride in water purification.

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