Three-dimensional peony flower-shaped composite photocatalyst and preparation method thereof

Abstract

The application discloses a three-dimensional peony flower-shaped composite photocatalyst and a preparation method thereof. On the basis of Bi2O2CO3, a surfactant and a halogenating agent are introduced to generate a synergistic reaction, the solubilization of the surfactant to the halogen salt is utilized, the selective diffusion of ions in the reaction is realized, the generation of BiOCl is promoted, the preferred orientation and the micro morphology of the crystal growth are intervened, oxygen vacancies are generated, active sites are increased, and thus the three-dimensional peony flower-shaped composite photocatalyst containing a BiOCl / Bi2O2CO3 heterostructure is constructed. Meanwhile, a trace amount of surfactant residue is left on the surface of the powder, the phase solubility of the material and pollutants is increased, and thus the catalytic performance is effectively improved. The method has simple and convenient preparation process, and the prepared powder has good dispersity, a stable three-dimensional flower-shaped structure and surface defects, and is beneficial to improving the photocatalytic performance of the powder.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalyst materials, and particularly relates to a three-dimensional peony flower-shaped composite photocatalyst and a preparation method thereof. BACKGROUND

[0002] The photocatalyst can effectively solve the development and utilization of solar energy and the sewage treatment problem in environmental pollution, and people pay attention to the expansion of the application of photocatalytic materials in most visible light in sunlight. As one of bismuth-based photocatalysts, bismuth carbonite (Bi2O2CO3) has strong photocatalytic properties in the visible light region, but its wide band gap limits the generation of photo-generated electrons and holes, and its stacked morphology inhibits the adsorption of pollutants and subsequent catalytic reactions. Bismuth carbonite is often combined with other materials to form a heterostructure to improve its photocatalytic performance, but the microstructure of the powder stack limits the catalytic reaction during the modification process, and the introduction of a surfactant can not only regulate the microstructure of the photocatalyst, but also produce defects on the surface of the catalyst to improve the photocatalytic performance. SUMMARY

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a three-dimensional peony flower-shaped composite photocatalyst and a preparation method thereof, which has a simple and convenient preparation process and a stable microstructure of the prepared powder. During the preparation process, BiOCl / Bi2O2CO3 is generated through the combined action of a surfactant and a halogenating agent, and a three-dimensional peony flower-shaped microstructure is constructed, which is easy to catalyze the reaction. The growth of the crystal and the number of micro-morphology and surface oxygen defects are regulated during the reaction process, and the photocatalytic performance of the pure-phase Bi2O2CO3 powder is improved.

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

[0005] A preparation method of a three-dimensional peony flower-shaped composite photocatalyst, comprising the following steps:

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

[0007] Step 2: mixing the pure-phase Bi2O2CO3 powder with a surfactant and a halide salt solution in a water bath, collecting the product and washing, centrifuging, drying and grinding, and the surfactant and the halogenating agent synergistically act during the process to synthesize a BiOCl / Bi2O2CO3 heterostructure photocatalyst, i.e. the three-dimensional peony flower-shaped composite photocatalyst.

[0008] In one embodiment, the step 1, the bismuth nitrate pentahydrate is mixed with deionized water, and then the sodium citrate, urea and polyvinylpyrrolidone are added in sequence, and the mixture is stirred to obtain a white precursor solution; the white precursor solution is kept at 170-190 DEG C in a sealed autoclave for 10-12 hours, and then cooled to room temperature; the product is collected and centrifuged, and then washed with deionized water and anhydrous ethanol alternately, and dried and ground to obtain pure-phase flower-like Bi2O2CO3 powder.

[0009] In one embodiment, the amount of the bismuth nitrate pentahydrate is 0.4-0.5 g, and the amount of the sodium citrate, urea and polyvinylpyrrolidone is 0.8-0.9 g, 0.2-0.3 g and 0.4-0.5 g, respectively.

[0010] In one embodiment, the step 1, the drying condition is 60-80 DEG C for 10-14 hours, and the step 2, the drying condition is 60-80 DEG C for 10-14 hours.

[0011] In one embodiment, the step 2, the amount of the Bi2O2CO3 powder is 0.2-0.3 g, the amount of the surfactant is 15-75 mg, the concentration of the halide salt solution is 1-1.5 mol / L, and the amount of the halide salt solution is 3-5 mL.

[0012] Different types of surfactants have different effects on the promotion of the dissolution of the chloride salt in the solution. Among them, CTAC has a promoting effect on the dissolution of the chloride salt, and further affects the ion exchange reaction in the solution, so that the proportion of the BiOCl crystal phase in the composite photocatalyst is increased. At the same time, a suitable amount of CTAC can maintain the three-dimensional peony flower-like morphology, affect the self-assembly of the lamella, and avoid the stacking of the lamella due to excessive conversion of BiOCl, so as to affect the photocatalytic performance of the powder. In addition, there will be a small amount of surfactant residues on the surface of the three-dimensional peony flower-like composite photocatalyst, and these surfactants can act as shallow electron traps on the surface of the powder, increase the number of oxygen defects, enhance the role of the trapping center, reduce the recombination of the photo-generated carriers, and improve the photocatalytic performance.

[0013] In one embodiment, the halide salt solution is a LiCl solution.

[0014] In one embodiment, the surfactant is DA hydrochloride (dopamine hydrochloride), SDBS (sodium dodecyl benzene sulfonate) or CTAC (dodecyl trimethyl ammonium chloride).

[0015] In one embodiment, the step 2, first mix the pure phase Bi2O2CO3 powder with deionized water, then stir in a water bath pot at 25-35 DEG C for 1-2 hours; then add the surfactant and stir for 20-40 minutes; then add the halide salt solution dropwise, continue to stir for 20-40 minutes.

[0016] The application also claims the three-dimensional peony flower-shaped composite photocatalyst prepared by the above preparation method.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] 1. The microstructure of the powder is a three-dimensional flower shape of "double peony flower", which is due to the joint effect of the surfactant and the halogenating agent. In the mutual transformation process of Bi2O2CO3 and BiOCl, the addition of the surfactant makes the stacking of the lamellas preferentially develop into a plane, exposing the center of the flower structure. Compared with the Bi2O2CO3 powder, the transformed lamellas are larger and thinner, have a larger surface area, are beneficial to electron transmission, expose more active sites, promote the separation of photo-generated carriers, and improve the photocatalytic efficiency.

[0019] 2. In the wet reaction, the surfactant and the halogenating agent jointly act on the formation of BiOCl / Bi2O2CO3. The surfactant has a solubilizing effect on the chloride salt, realizes the selective diffusion of ions in the solution, controls the combination rate of groups, and at the same time, a trace amount of surfactant residue is left on the surface of the catalytic powder, as a shallower electron trap center, increases the oxygen vacancies on the surface of the powder, enhances the effect of the trapping center, enhances the adsorption of the photocatalyst to pollutants, and improves the photocatalytic degradation efficiency.

[0020] 3. A trace amount of surfactant promotes the exchange reaction of CO3 2 in Bi2O2CO3 with Cl - in the halogenating agent, in-situ grows BiOCl on Bi2O2CO3, so that the two have a good heterojunction, lattice distortion occurs at the interface, the band gap of the photocatalyst is adjusted, a heterostructure is formed, which is beneficial to the transmission of photo-generated carriers, thereby improving the performance of the photocatalyst.

[0021] 4. The preparation period of the application is short, the preparation process is simple, the reaction process is carried out under neutral conditions, the equipment is not damaged, the prepared powder has good dispersibility, stable structure, and has the catalytic ability of degrading organic dyes and antibiotics such as norfloxacin. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a SEM diagram of a three-dimensional peony flower-shaped composite photocatalyst.

[0023] Figure 2 are photocatalytic degradation diagrams of pure-phase Bi2O2CO3 powder and three-dimensional peony flower-like composite photocatalyst containing BiOCl / Bi2O2CO3 heterostructure in degrading rhodamine B. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and examples. The technical solutions of the present application are not limited to the specific embodiments listed below, but also include any combination of the specific embodiments.

[0025] A preparation method of a three-dimensional peony flower-like composite photocatalyst, pure-phase Bi2O2CO3 powder prepared by a hydrothermal method is mixed with a surfactant and a halide salt solution added subsequently in a water bath, and the surfactant and the halide agent synergize during the process to synthesize a three-dimensional peony flower-like composite photocatalyst containing BiOCl / Bi2O2CO3 heterostructure.

[0026] It can specifically include the following steps:

[0027] Step 1), 0.4g-0.5g bismuth nitrate pentahydrate is uniformly mixed with 25mL-35mL deionized water, 0.8g-0.9g sodium citrate, 0.2g-0.3g urea and 0.4g-0.5g polyvinylpyrrolidone (K30) are sequentially added, and stirring is performed for 30min-50min to obtain a white precursor solution; the white precursor solution is placed in a stainless steel airtight autoclave with a polytetrafluoroethylene liner, and is kept at 170℃-190℃ for 10-12 hours, and then naturally cooled to room temperature; the product is collected and centrifuged, and is washed with deionized water and anhydrous ethanol alternately for several times, and then dried in an oven at 60℃-80℃ for 10-14 hours, and after grinding, pure-phase flower-like Bi2O2CO3 powder is obtained.

[0028] Step 2), 0.2g-0.3g Bi2O2CO3 powder is mixed with 20mL-30mL deionized water, and stirred in a water bath at 25-35℃ for 1-2 hours; then 15mg-75mg of surfactant is added, and stirred for 20min-40min; finally, 3mL-5mL of 1.3mol / L LiCl solution is added dropwise, and continues to stir for 20min-40min; the product is collected and washed several times with deionized water and anhydrous ethanol alternately, and then dried in an oven at 60-80℃ for 10-14 hours, and after grinding, the three-dimensional flower-like BiOCl / Bi2O2CO3 composite powder is obtained. In this step, the surfactant and halogenating agent are introduced on the basis of Bi2O2CO3 to occur a synergistic reaction, the solubilization of the surfactant to the halide salt is utilized, the selective diffusion of ions in the reaction is realized, the generation of BiOCl is promoted, the preferred orientation and micro-morphology of crystal growth are intervened, the oxygen vacancies are produced, the active sites are increased, and thus the three-dimensional peony flower-like composite photocatalyst containing BiOCl / Bi2O2CO3 heterostructure is constructed. At the same time, the trace amount of surfactant is left on the surface of the powder, the solubility of the material and the pollutants is increased, and thus the catalytic performance is effectively improved. Specifically, CO3 2- in the pure phase Bi2O2CO3 powder is exchanged with Cl - in the added LiCl solution to occur an ion exchange reaction, and a heterostructure is produced. Moreover, the previously added surfactant will affect the crystal phase composition of the photocatalytic powder, form a three-dimensional flower-like micro-morphology, and increase the number of surface oxygen defects. The method has simple and convenient preparation process, and the prepared powder has good dispersity, and has a three-dimensional flower-like stable structure and surface defects, which is beneficial to improve the photocatalytic performance of the powder.

[0029] In the present application, the surfactant used can be hydrochloric acid DA (hydrochloric acid dopamine), SDBS (sodium dodecyl benzene sulfonate) or CTAC (dodecyl trimethyl ammonium chloride).

[0030] The following are several embodiments of the present application.

[0031] Example 1

[0032] Step 1), 0.485g bismuth nitrate pentahydrate is mixed with 30mL deionized water, and 0.88g sodium citrate, 0.24g urea and 0.5g polyvinylpyrrolidone (K30) are sequentially added, and stirred for 45min to obtain a white precursor solution; the precursor solution is placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and is kept at 180℃ for 12 hours, and then naturally cooled to room temperature; the sample is collected and centrifuged, and washed with water and alcohol alternately for 6 times, and then dried in an oven at 60℃ for 12 hours, and after grinding, the pure phase Bi2O2CO3 powder is obtained.

[0033] Step 2), 0.25 g of Bi2O2CO3 powder was mixed with 30 mL of deionized water and stirred in a water bath at 30°C for 2 hours; then 15 mg of CTAC was added and stirred for 30 min, 4 mL of 1.3 mol / L LiCl solution was added dropwise, and stirring was continued for 30 min; finally, the product was collected by centrifugation, washed with water and alcohol alternately for 2 times, and then dried in an oven at 60°C for 12 hours. After grinding, the three-dimensional flower-shaped composite heterostructure BiOCl / Bi2O2CO3 powder was obtained.

[0034] Reference Figure 1 The three-dimensional peony flower-shaped BiOCl / Bi2O2CO3 composite photocatalyst prepared according to Example 1 benefits from the ion exchange reaction caused by the addition of CTAC and LiCl solution. The prepared heterostructure BiOCl / Bi2O2CO3 powder has a small structure size, an average particle size of about 1 μm, a moderate stacking of the sheet layers in the flower-shaped morphology, an un-filled stacking center, large and thin sheet layers, an increased specific surface area of the powder, more active sites, greater adsorption capacity, and better catalytic activity. The addition of CTAC also generates more oxygen defects on the surface of the photocatalyst, further improving the photocatalytic performance of the powder.

[0035] The three-dimensional peony flower-shaped composite photocatalyst of the present application can provide a solution for sewage treatment in environmental problems, degrades pollutants such as organic dyes and antibiotics contained in sewage, and produces non-toxic products. In one application of the catalyst obtained in the present example, rhodamine B was used as the target pollutant, 30 mL of 10 mg / L rhodamine B was mixed with 30 mg of photocatalyst, and stirring was carried out in the dark for 30 min to reach adsorption equilibrium. A 500 W xenon lamp was used to simulate natural light, and the photocatalytic reaction was carried out at a temperature below 25°C. Every 20 min, 3 mL of the suspension was taken to analyze the degradation rate of the photocatalyst. In this process, the removed suspension was centrifuged using a high-speed centrifuge at 11000 r / min, and then the supernatant was poured into a cuvette. The degradation rate of the pollutant was quantitatively tested using a UV-Vis spectrophotometer.

[0036] The experimental results show that the degradation rate of pure-phase Bi2O2CO3 powder under light irradiation for 120 min is 97%, while the three-dimensional peony flower-shaped composite photocatalyst containing BiOCl / Bi2O2CO3 heterostructure achieves the same degradation effect under light irradiation for 80 min.

[0037] In another application, similar means were used, and rhodamine B was replaced by 10 mg / L norfloxacin. The degradation rate of the present example reached 85% in 80 min, showing good photocatalytic performance.

[0038] Example 2

[0039] Step 1), 0.485 g of bismuth nitrate pentahydrate was mixed with 30 mL of deionized water, and 0.88 g of sodium citrate, 0.24 g of urea and 0.5 g of polyvinylpyrrolidone (K30) were sequentially added, stirred for 45 min to obtain a white precursor solution; the precursor solution was placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner and incubated at 180℃ for 12 hours, and then naturally cooled to room temperature; the product was collected and centrifuged, and washed with deionized water and anhydrous ethanol alternately for several times, and then dried in an oven at 70℃ for 14 hours, and ground to obtain pure phase Bi2O2CO3 powder.

[0040] Step 2), 0.25 g of Bi2O2CO3 powder was mixed with 30 mL of deionized water, and stirred in a water bath at 30℃ for 2 hours; then 50 mg of SDBS was added, stirred for 30 min, and 4 mL of 1.3 mol / L LiCl solution was added dropwise, and stirred for another 30 min; finally, the product was collected and centrifuged, and washed with water and ethanol alternately for 6 times, and then dried in an oven at 70℃ for 14 hours, and ground to obtain three-dimensional flower-like composite heterostructure BiOCl / Bi2O2CO3 powder. In this process, part of the groups in the pure phase Bi2O2CO3 powder are replaced by Cl - The ion exchange reaction is carried out, and SDBS affects the ion exchange process and intervenes in the preferred growth orientation of the crystal. The heterostructure is generated at the same time, and the flower-like morphology is formed which is beneficial to the photocatalytic reaction.

[0041] In more embodiments of the present application, the aforementioned parameters are combined in different types, for example, in step 1), 0.4 g, 0.42 g and 0.5 g of bismuth nitrate pentahydrate are selected respectively, 25 mL, 30 mL and 35 mL of deionized water are selected respectively, 0.82 g, 0.86 g and 0.89 g of sodium citrate are selected respectively, 0.2 g, 0.22 g and 0.25 g of urea are selected respectively, and 0.45 g, 0.48 g and 0.49 g of polyvinylpyrrolidone are selected respectively, and the results prove that white precursor solutions can be prepared.

[0042] The hydrothermal temperature is selected as 170℃, 180℃ and 190℃ respectively, and the time is selected as 10 hours, 11 hours and 12 hours respectively, the drying temperature is selected as 60℃, 70℃ and 80℃ respectively, and the time is selected as 10 hours, 12 hours and 14 hours respectively, and the results prove that pure phase flower-like Bi2O2CO3 powder can be prepared.

[0043] Similarly, in step 2), 0.2 g, 0.25 g, 0.3 g of Bi2O2CO3 powder, 3 mL, 4 mL, 5 mL of LiCl solution, and 15 mg, 50 mg, 75 mg of surfactant are selected for combination; the results prove that three-dimensional flower-like BiOCl / Bi2O2CO3 composite powder can be prepared.

[0044] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any other 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 included in the protection scope of the present application.

Claims

1. A method for preparing a three-dimensional peony flower-shaped composite photocatalyst, characterized in that, It comprises the following steps: Step 1, pure phase Bi2O2CO3 powder is prepared by a hydrothermal method, and the method is as follows: Bi(NO3)3.5H2O is mixed with deionized water, and sodium citrate, urea and polyvinylpyrrolidone are sequentially added and stirred to obtain a white precursor solution; the white precursor solution is kept at 170-190 DEG C in a sealed autoclave for 10-12 hours, and then cooled to room temperature; the product is collected and centrifuged, and washed with deionized water and anhydrous ethanol alternately, dried and ground to obtain pure phase flower-like Bi2O2CO3 powder; Step 2, the pure phase Bi2O2CO3 powder is mixed with a surfactant and a halide salt solution in a water bath, and the product is collected, washed, centrifuged, dried and ground, and the surfactant and halide agent synergistically synthesize a BiOCl / Bi2O2CO3 heterostructure photocatalyst, i.e. the three-dimensional peony flower-like composite photocatalyst, wherein the halide salt solution is a LiCl solution, and the surfactant is CTAC.

2. The method for preparing the three-dimensional peony flower-shaped composite photocatalyst according to claim 1, characterized in that, The amount of Bi(NO3)3.5H2O is 0.4-0.5 g, and the amounts of sodium citrate, urea and polyvinylpyrrolidone are 0.8-0.9 g, 0.2-0.3 g and 0.4-0.5 g, respectively.

3. The method for preparing the three-dimensional peony flower-shaped composite photocatalyst according to claim 1, characterized in that, In step 1, the drying condition is 60-80 DEG C for 10-14 hours, and in step 2, the drying condition is 60-80 DEG C for 10-14 hours.

4. The preparation method of the three-dimensional peony flower-shaped composite photocatalyst according to claim 1, characterized in that, In step 2, the amount of Bi2O2CO3 powder is 0.2-0.3 g, the amount of surfactant is 15-75 mg, and the concentration of halide salt solution is 1-1.5 mol / L, and the amount is 3-5 mL.

5. The method for preparing the three-dimensional peony-shaped composite photocatalyst according to any one of claims 1 to 4, characterized in that, In step 2, the pure phase Bi2O2CO3 powder is first mixed with deionized water, and then stirred in a water bath at 25-35 DEG C for 1-2 hours; then the surfactant is added and stirred for 20-40 min; then the halide salt solution is added dropwise, and the stirring is continued for 20-40 min.

6. The three-dimensional peony flower-like composite photocatalyst prepared by the preparation method of any one of claims 1-5.

7. The use of the three-dimensional peony flower-like composite photocatalyst of claim 6 as a catalyst for degrading rhodamine B or norfloxacin in sewage treatment.

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