CN110102322B - Preparation method of flower-like Ag@AgBr/ZnO photocatalytic materials - Google Patents

Abstract

The invention discloses a preparation method of a flower-shaped Ag@AgBr/ZnO photocatalytic material, and belongs to the field of nanometer material preparation. The method adopts the following steps: 1) configuring a certain concentration of surfactant and a Zn source as a Zn source solution; configuring a certain concentration of hexamethylenetetramine and an Ag source as an Ag source solution; 2) adding a solution to the Ag source solution Add oxidizing agent, and add it dropwise to the Zn source solution at a certain rate; 3) transfer the mixed solution to an autoclave, and carry out a hydrothermal reaction at a certain temperature for a certain period of time; 4) Wash the product with water and alcohol and dry it After calcination in air, the flower-like Ag@AgBr/ZnO photocatalytic material was obtained after cooling to room temperature. The synthetic method adopted in the present invention has the advantages of simple process flow, simple and convenient operation, and no secondary pollution. The synthesized photocatalytic materials have the characteristics of uniform morphology and excellent performance. The work of the present invention belongs to the field of photocatalytic materials.

Description

Preparation method of flower-like Ag@AgBr/ZnO photocatalytic materials

technical field

The invention relates to a preparation method of flower-shaped Ag@AgBr/ZnO photocatalytic materials.

Background technique

ZnO is a semiconductor catalyst widely used in photocatalytic oxidation technology. It has excellent photocatalytic activity, stable chemical properties and high quantum yield. Therefore, ZnO has high application value in sewage treatment and other directions. However, ZnO is a wide bandgap semiconductor material, which can only stimulate photocatalytic oxidation reaction by ultraviolet light, and the utilization rate of sunlight is only 4%, and as a photocatalytic material, ZnO also has an electron-hole pair recombination rate. quick question. These defects limit its practical application. In order to solve these defects of ZnO, a series of attempts have been made. The study found that the Ag@AgBr plasmonic catalyst, due to the plasmon resonance effect of Ag nanoparticles generated by the decomposition of AgBr in the system, can respond to visible light for the photocatalytic oxidation process of Ag@AgBr, but due to its small inherent band gap, it can be directly used For photocatalytic oxidation, the effect is not ideal. In view of the advantages and disadvantages of a single catalyst, we composite Ag@AgBr and ZnO to form a composite catalyst Ag@AgBr/ZnO, which greatly improves the utilization rate of light by the photocatalyst and can generate light between the components. Electron transfer, delaying the recombination of electron-hole pairs, and improving the speed and efficiency of photocatalytic degradation of organic matter. In today's severe environmental situation, the development of efficient composite photocatalysts is imminent, which has both theoretical and practical value.

In 2013, Lei Shi et al. in the article "Highly efficient visible light-drivenAg/AgBr/ZnO composite photocatalyst for degrading Rhodamine B" used a two-step deposition-precipitation method to obtain AgBr/ZnO photocatalytic materials, and then prepared rod-shaped materials by photoreduction method. Ag/AgBr/ZnO nanocomposites. Under the condition of simulated sunlight irradiation for 1h, the degradation rate of 0.05g of this sample to 10mg/L Rhodamine B was 94.7%. The preparation method of the deposition-precipitation two-step method combined with the photoreduction method has problems such as complicated operation, cumbersome process and long preparation period.

In 2014, Qi Zhang et al. in the article "In situ oxidation of Ag/ZnO by bromine water to prepare ternary Ag-AgBr/ZnO sunlight-derived photocatalyst" used bromine water in situ oxidation of Ag/ZnO microspheres prepared by one-pot method to obtain spherical Ag-AgBr/ZnO composite photocatalytic material. Under the condition of 300W iodine-tungsten lamp irradiation for 3h, the degradation rate of 0.1g of this sample to 5mg/L Rhodamine B is close to 100%. In addition to the complicated preparation process and long preparation period, this preparation method also has the problem of low degradation efficiency of spherical Ag-AgBr/ZnO.

In 2011, Xu Yuanguo et al. used the hydrothermal method to prepare Ag/AgBr@ZnO photocatalyst in the conference "Preparation of Ag/AgBr@ZnO Photocatalyst and Research on Degradation of Methyl Orange". The degradation rate of methyl orange was about 95% under illumination for 3h. It is not difficult to see that the degradation time as long as 3h cannot reflect the high efficiency and rapidity of the photocatalytic oxidation method.

In 2018, Cheng Zhipeng et al. used the hydrothermal method to prepare porous Ag/AgBr materials in the patent "Preparation Method of Porous Ag/AgBr Nanomaterials" (CN108975383A). In the method, the Ag/AgCl/AgBr precursor is first prepared, and Ag/AgBr is obtained after the AgCl is removed by washing with ammonia solution. The preparation process is not directly directed to the final prepared nanomaterials, and there is a certain waste of raw materials.

In 2016, Chen Shenyun et al. used imidazolium-based ionic liquid 1-butyl-3-methylimidazolium bromide ([BMIM]Br) in the patent "Preparation and Application of Photocatalyst Ag/AgBr" (CN106111166A). The Ag/AgBr photocatalyst was prepared hydrothermally from bromine source and precursor. It is worth pointing out that ionic liquids will strongly absorb moisture in the air (even hydrophobic ionic liquids), greatly reducing its performance; and in practical experiments, ionic liquids are expensive and low in purity (limited by the preparation process), once mixed with Impurities will also affect its performance, limiting its practical application ability.

In 2015, Wang Yongqiang et al. used CuBr microspheres as templates in the patent "Preparation Method of Visible Light Catalyst AgBr/Ag Porous Composite Microspheres" (CN104815679A), and prepared AgBr/Ag porous composite microspheres visible light catalyst by ion exchange method. Under the irradiation of 400nm filter xenon lamp (500W), the degradation rate of 30mL of 10mg/mL methyl orange reached more than 90%.

In 2018, Song Caixia et al. used the spray drying method to prepare the Ag/ZnO nanorod self-assembly precursor in the patent "A preparation method of Ag/ZnO nanorod self-assembly" (CN108745354A), and then calcined to obtain Ag/ZnO Nanorod Hierarchical Self-Assembly. The prepared Ag/ZnO nanorod assembly photocatalytic material can be used for photocatalytic water splitting to produce hydrogen, and the yield can be as high as 1.07mmol/g ^-1 h ^-1 .

In 2018, in the patent "A Method for Preparing Ag-loaded ZnO Nanorod Arrays" (CN108970612A), Zhao Jingzhong et al. first prepared the ZnO seed layer substrate, secondly prepared the ZnO nanorod array film, and finally prepared the ZnO nanorod array film. Ag-supported to obtain an Ag-supported ZnO material.

In 2017, Cai Fanpeng et al. used the spray thermal decomposition method in the gas phase method to prepare the ZnO photocatalytic material in the patent "A Preparation Method of Hollow ZnO" (CN108002425A). It is worth mentioning that the hollow ZnO material prepared by this method has serious fragmentation, non-uniform particle size and non-uniform morphology. This result will directly lead to the uncontrollable photocatalytic activity of the material.

In 2018, Xing Yanjun et al. prepared micro-nano ZnO with various morphologies under normal pressure and low temperature conditions in the patent "A method for preparing micro-nano ZnO with controllable morphology under normal pressure and low temperature conditions" (CN108275713A). It is worth pointing out that this preparation method uses the solvent oleylamine, which is known to have a pungent odor and can burn and corrode the skin. The safety and productivity of this preparation method needs to be investigated.

Although the above methods have made outstanding contributions to the preparation of photocatalytic materials, these preparation methods have many common problems, such as cumbersome preparation process, harsh raw material requirements, and poor catalytic performance of the obtained catalysts with special morphology. Comparatively speaking, the one-step hydrothermal method used in the present invention has simple process, convenient operation, easy control of various parameters, cheap and easy-to-obtain raw materials, and the special morphology of the catalyst is beneficial to the improvement of catalytic activity. In addition to controlling the morphology as a surfactant, CTAB also acts as a bromine source, controlling the morphology and saving raw materials, killing two birds with one stone.

To sum up, in the present invention, a flower-like Ag@AgBr/ZnO material with excellent photocatalytic performance is synthesized by a simple one-step hydrothermal method, which meets the relevant requirements for materials in practical applications.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of expensive raw materials, complicated and tedious technological process, long preparation time, unsuitable production efficiency for mass production, and relatively high photocatalytic activity of the existing Ag@AgBr/ZnO photocatalytic material preparation methods. To solve the problem of poor quality, a preparation method of flower-like Ag@AgBr/ZnO photocatalytic material is provided.

The preparation method of flower-like Ag@AgBr/ZnO photocatalytic material is carried out according to the following steps:

1. According to the ratio of the amount of Zn element, Ag element, hexamethylenetetramine and surfactant to a certain value, configure a certain concentration of Zn source and surfactant in 30 mL of distilled water to obtain a Zn source solution; configure A certain concentration of Ag source and hexamethylenetetramine are dissolved in 20 mL of distilled water, and an oxidant is added to obtain an Ag source solution;

2. Add the Ag source solution dropwise to the Zn source solution at a certain drop rate, and transfer the mixed solution to the high-pressure reactor for hydrothermal reaction. The mixed solution accounts for about 50% of the volume of the reactor. The temperature is maintained for a certain hydrothermal time.

3. After washing with water, alcohol and drying, the product was transferred into a muffle furnace, calcined at a certain temperature for a certain period of time in an air atmosphere, and cooled to room temperature to obtain a flower-like Ag@AgBr/ZnO photocatalytic material .

The material ratio of Zn element, Ag element, hexamethylenetetramine and surfactant described in step 1 is 1:(0.01-0.4):1:(0.1-1).

The concentrations of the Zn source, surfactant, Ag source and hexamethylenetetramine described in step 1 are respectively 0.3333mol/L, (0.03333～0.3333)mol/L, (0.05～0.2)mol/L and 0.5 mol/L.

The Zn source described in step 1 is zinc sulfate (ZnSO ₄ ), zinc acetate dihydrate (C ₄ H ₆ O ₄ Zn·2H ₂ O), zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O) Or zinc sulfate heptahydrate (ZnSO ₄ ·7H ₂ O) compound.

The surfactant described in step 1 is cetyl trimethyl ammonium bromide (CTAB)

_The oxidant described in step one is H2O2 ₍ 30%).

The dropping acceleration rate described in step 2 is 1-3 seconds/drop; the set hydrothermal temperature is 100-180°C; and the hydrothermal time is 1-5 hours.

The calcination temperature in step 3 is 500-800°C; the calcination time is 1-3h.

The beneficial effects of the present invention are as follows:

The invention adopts zinc salt and silver nitrate as the silver source, so that the raw material components are mixed at the molecular level, and the synthesized flower-shaped Ag@AgBr/ZnO photocatalytic material composed of porous sheets has uniform chemical components; the invention adopts CTAB as the surface active material It can effectively control the morphology and particle size of the catalyst, so that the synthesized flower-like Ag@AgBr/ZnO photocatalytic material has a uniform morphology and uniform particle size; at the same time, CTAB also participates in the reaction as a Br source, without additional Selecting other Br sources saves costs and effectively reduces the difficulty of preparing Ag@AgBr/ZnO photocatalysts. The prepared flower-like Ag@AgBr/ZnO composed of porous sheets has extremely strong photocatalytic activity, which is in line with practical applications. material requirements.

Description of drawings

Fig. 1, the SEM photograph of the flower-shaped Ag@AgBr/ZnO material prepared by the method of the present invention

Fig. 2, the XRD spectrum of the flower-like Ag@AgBr/ZnO material prepared by the method of the present invention

Fig. 3. The relationship curve of the degradation efficiency of Rhodamine B and the photocatalytic time of the flower-shaped Ag@AgBr/ZnO material (specific embodiment 1) prepared by the method of the present invention, the catalyst amount is 1 g·L ^-1 , the Rhodamine B concentration 5mg·L ^-1 . In the figure (a) Ag@AgBr/ZnO material (specific embodiment 1) degradation efficiency of Rhodamine B when catalyzed under simulated sunlight; (b) Rhodamine B under simulated sunlight without Ag@AgBr/ZnO material catalysis The natural degradation efficiency of Ming B; (c) the degradation efficiency of rhodamine B when the Ag@AgBr/ZnO material (specific embodiment 1) is catalyzed under no-light conditions.

Fig. 4. The relationship curve between the degradation efficiency of methylene blue and the photocatalytic time of the flower-shaped Ag@AgBr/ZnO material (specific embodiment 1) prepared by the method of the present invention, the catalyst amount is 1 g·L ^-1 , and the methylene blue concentration is 10 mg·L ^-1 .

Fig. 5, the relation curve of the degradation efficiency of cefuroxime sodium and the photocatalytic time of the flower-shaped Ag@AgBr/ZnO material prepared by the method of the present invention (specific embodiment 1), the catalyst amount is 1 g·L ^-1 , the cefuroxime sodium The concentration is 20mg·L ^-1 .

Detailed ways

The technical solutions of the present invention are not limited to the specific embodiments listed below, but also include any combination of specific embodiments.

Embodiment 1: The preparation method of the flower-shaped Ag@AgBr/ZnO material photocatalytic material in this embodiment is carried out according to the following steps:

1. Weigh zinc acetate dihydrate, silver nitrate, hexamethylenetetramine in the ratio of 1:0.2:1:0.55 according to the ratio of Zn element, Ag element, hexamethylenetetramine and surfactant. Amine and CTAB, configure 0.3333mol/L and 0.1833mol/L Zn source and surfactant in 30mL distilled water to obtain Zn source solution; configure 0.1mol/L and 0.5mol/L Ag source and hexamethylenetetramine Amine in 20mL of distilled water, and add oxidant, Ag source solution;

2. The Ag source solution is added dropwise to the Zn source solution at a drop rate of 1 second/drop, and the mixed solution is transferred to a high-pressure reactor for hydrothermal reaction. The mixed solution accounts for about 50% of the volume of the reactor. The hydrothermal temperature is 140°C, and the hydrothermal time is maintained at this temperature for 3 hours;

3. After washing with water, alcohol and drying, the resultant was transferred into a muffle furnace, calcined at 650 °C for 2 h in an air atmosphere, and cooled to room temperature to obtain a flower-shaped Ag@AgBr/ZnO photocatalytic material.

The beneficial effects of this embodiment are as follows: the flower-like Ag@AgBr/ZnO material synthesized in this embodiment has a flower-like structure composed of clusters of porous lamellae, and the use of CTAB can effectively control the growth direction and clustering mode of catalyst crystals, The morphology of the Ag@AgBr/ZnO material is about 4-6 μm in diameter, as shown in Figure 1. The larger size is beneficial to the free electron transfer in the photocatalytic process of the photocatalyst, and the XRD result (Fig. 2) shows the high crystalline nature of the composite material prepared by the present invention, which is also beneficial to the photocatalyst in the photocatalytic process. free electron transfer. The efficient transport of free electrons can reduce the recombination probability of electron holes to a certain extent, so that the Ag@AgBr/ZnO composite photocatalytic material exhibits extremely excellent photocatalytic activity.

A 5 mg·L ^-1 solution of Rhodamine B was degraded with 1 g·L ^-1 of the prepared flower-like Ag@AgBr/ZnO material, and stirred for 30 min under simulated sunlight, and the degradation rate reached 99.11%.

10 mg·L ^-1 of methylene blue solution was degraded with 1 g·L ^-1 of the prepared flower-like Ag@AgBr/ZnO material, and stirred for 30 min under simulated sunlight, and the degradation rate reached 99.99%.

1 g·L ^-1 of the prepared flower-like Ag@AgBr/ZnO material was used to degrade 20 mg·L ^-1 of cefuroxime sodium solution, and stirred for 30 min under simulated sunlight, and the degradation rate was 74.77%; after stirring for 150 min, the degradation rate reached 95.09% .

Specific implementation two:

1. Weigh zinc acetate dihydrate, silver nitrate, hexamethylenetetramine in the ratio of 1:0.2:1:0.55 according to the ratio of Zn element, Ag element, hexamethylenetetramine and surfactant. Amine and CTAB, configure 0.3333mol/L and 0.1833mol/L Zn source and surfactant in 30mL distilled water to obtain Zn source solution; configure 0.1mol/L and 0.5mol/L Ag source and hexamethylenetetramine Amine in 20mL of distilled water, and add oxidant, Ag source solution;

2. The Ag source solution is added dropwise to the Zn source solution at a drop rate of 3 seconds/drop, and the mixed solution is transferred to a high-pressure reactor for hydrothermal reaction. The mixed solution accounts for about 50% of the volume of the reactor. The hydrothermal temperature is 160℃, and the hydrothermal time is maintained at this temperature for 2.5 hours;

3. After washing with water, alcohol and drying, the resultant was transferred into a muffle furnace, calcined at 500 °C for 2.5 h in an air atmosphere, and cooled to room temperature to obtain a flower-shaped Ag@AgBr/ZnO photocatalytic material.

Specific implementation three:

1. Weigh zinc acetate dihydrate, silver nitrate, hexamethylenetetramine in the ratio of 1:0.2:1:0.55 according to the ratio of Zn element, Ag element, hexamethylenetetramine and surfactant. Amine and CTAB, configure 0.3333mol/L and 0.1833mol/L Zn source and surfactant in 30mL distilled water to obtain Zn source solution; configure 0.1mol/L and 0.5mol/L Ag source and hexamethylenetetramine Amine in 20mL of distilled water, and add oxidant, Ag source solution;

2. The Ag source solution is added dropwise to the Zn source solution at a drop rate of 2 seconds/drop, and the mixed solution is transferred to a high-pressure reactor for hydrothermal reaction. The mixed solution accounts for about 50% of the volume of the reactor. The hydrothermal temperature is 130°C, and the hydrothermal time is maintained at this temperature for 4 hours;

3. After washing with water, alcohol and drying, the product was transferred into a muffle furnace, calcined at 700 °C for 3 h in an air atmosphere, and cooled to room temperature to obtain a flower-shaped Ag@AgBr/ZnO photocatalytic material.

The flower-shaped Ag@AgBr/ZnO powder shown in the invention can be used for photocatalytic decomposition of organic pollutants, and sunlight or ultraviolet light is used as a light source. During the photocatalytic reaction, it is carried out under stirring, adding a certain amount of catalyst (0.5-1g/L), and degrading a certain concentration (5-20mg/L) of Rhodamine B, methylene blue and rhodamine within a certain time (0.5-3h). Aqueous solutions of organic pollutants such as cefuroxime sodium. For example: to catalytically degrade 5mg/L Rhodamine B solution, take 100ml Rhodamine B solution, add catalyst (0.5～1g/L), carry out catalytic reaction under sunlight or ultraviolet light, at regular intervals (7.5～30min), Sampling 3-5ml of solution sample, after filtration, measure the absorbance of the solution with an ultraviolet-visible spectrophotometer to detect the change of solution concentration, thereby calculating the degradation rate of organic pollutants.

Claims (2)

1. The preparation method of the flower-shaped Ag @ AgBr/ZnO photocatalytic material is characterized by comprising the following steps of:

firstly, Zn element, Ag element, hexamethylenetetramine and hexadecyl trimethyl ammonium bromide according to the mass ratio of 1 (0.01-0.4): 1: (0.1-1), adding a Zn source and hexadecyl trimethyl ammonium bromide solution into 30mL of distilled water to obtain a Zn source solution; the Ag source and hexamethylenetetramine were added to 20mL of distilled water, and oxidant H was added₂O₂Obtaining Ag source solution;

dropwise adding the Ag source solution into the Zn source solution at the speed of 1-3 seconds per drop, transferring the mixed solution to a high-pressure reaction kettle for hydrothermal reaction, wherein the mixed solution accounts for 50% of the volume of the reaction kettle, and carrying out hydrothermal reaction for 1-5 hours at the temperature of 100-180 ℃;

and thirdly, washing with alcohol and drying the product, transferring the product into a muffle furnace, calcining for 1-3 h at 500-800 ℃ in the air atmosphere, and cooling to room temperature to obtain the flower-shaped Ag @ AgBr/ZnO photocatalytic material.

2. The preparation method of the flower-like Ag @ AgBr/ZnO photocatalytic material as claimed in claim 1, wherein the Zn source in the first step is zinc acetate dihydrate, zinc nitrate hexahydrate or zinc sulfate heptahydrate, and the Ag source is silver nitrate.

Images