Preparation method of Ag2S / Ag composite nanosheet photocatalyst
The Ag2S/Ag composite nanosheet photocatalyst was prepared by a two-step solvothermal method, which solved the problems of wide band gap and complex synthesis of existing photocatalysts and achieved the effect of efficient photocatalytic degradation of organic dyes and easy recycling.
Patent Information
- Application Number
- CN202411516951.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2025-01-07
AI Technical Summary
Existing photocatalysts such as TiO2 and ZnO have wide band gaps, which cannot fully utilize visible light. They also have low quantum efficiency and low photocatalytic performance when used alone. Furthermore, they require the addition of surfactants during synthesis and have problems such as small contact area or difficulty in recycling during use.
A two-step solvothermal method was used to prepare Ag2S/Ag composite nanosheet photocatalysts. Inexpensive chemical reagents zinc nitrate, thiourea and silver nitrate were used to synthesize Ag2S/Ag composite nanosheets under mild conditions through solvothermal reaction, avoiding the use of surfactants and forming an irregular sheet-like structure.
The preparation process is simple, low-cost, produces high-purity products with high photocatalytic activity, and can effectively degrade organic dyes with a degradation rate of up to 99.2%. It is also easy to recycle and reuse.
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Figure CN119259080A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a method for preparing a Ag2S / Ag composite nanosheet photocatalyst. Background Art
[0002] In recent years, environmental problems caused by toxic organic pollutants have become the focus of global attention. Countries around the world are seeking effective ways to solve water pollution. Over the years, humans have developed a variety of physical, chemical and biochemical methods to treat sewage, and have achieved certain results. However, the biological-physical treatment method used can only meet basic emission requirements. Although there is a slight decrease in chromaticity, organic matter is only decomposed into smaller substances. The properties of these decomposition products are difficult to control and master, and it is impossible to guarantee that there will be no harm to the environment. In recent years, the emerging semiconductor photocatalytic technology has attracted widespread attention due to its low production cost, simple equipment, mild reaction conditions, easy operation and control, and low secondary pollution. Semiconductor photocatalytic technology is believed to be able to effectively solve energy and environmental problems, and countries around the world have conducted extensive research on semiconductor photocatalysis.
[0003] Common semiconductor catalysts include TiO2, ZnO, ZnS, etc. These catalysts are widely used because of their advantages such as low price, non-toxicity and good stability. However, due to their wide band gap, they cannot fully utilize the visible part and have low quantum efficiency, which limits their practical application. Therefore, people now focus on the research of new visible light catalysts. In recent years, transition metal sulfur compounds have attracted widespread interest from researchers because of their special photoelectric properties and chemical properties. Among the many transition metal sulfur compounds, Ag2S has always been one of the substances that has received widespread attention. Ag2S is a typical narrow band gap semiconductor with a band gap of about 1.0 eV at room temperature. It is an n-type semiconductor photocatalyst with a large light absorption coefficient and good photoelectric properties. It is widely used in optoelectronic devices and electronic devices. However, a single photocatalyst itself cannot have a narrower gap width, a more negative conduction band and a more positive valence band at the same time. At the same time, due to the recombination of photogenerated electron-hole pairs, the photocatalytic performance of a single photocatalyst is relatively low. Therefore, the formation of a heterojunction at the photocatalyst interface is an effective way to improve the photocatalytic activity. As a precious metal nanomaterial, Ag plays an important role in catalysis, optics, biological diagnosis and treatment. Therefore, a new type of composite material can be obtained by combining Ag2S and Ag. This composite structure not only has the properties of these two nanomaterials, but also has better performance under synergistic effect.
[0004] At present, most photocatalysts are in the form of thin films or nanoparticles. Thin film catalysts have relatively small contact areas with organic pollutants during use, and the catalyst is easily deactivated. Nanoparticle catalysts have problems such as small particles and difficult to recover during use. Two-dimensional nanosheet catalysts can effectively solve these problems. In addition, there are few reports on Ag2S / Ag composite nanosheets, and very few of them have been used in photocatalytic treatment of organic pollutants. And in the process of synthesizing silver-containing composite materials, it is often necessary to add some surfactants. Therefore, a synthesis method that uses less chemical reagents, has a simple preparation process, a low reaction temperature, does not add any surfactants, does not require complex and expensive equipment, and has mild synthesis conditions is a technical problem that needs to be solved at present. Summary of the invention
[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for preparing Ag2S / Ag composite nanosheet photocatalyst. The method uses less chemical reagents, has a simple preparation process, a low reaction temperature, does not add any surfactant, does not require complex and expensive equipment, and has mild synthesis conditions; the synthesis of Ag2S / Ag composite nanosheets does not introduce impurities, has high purity, and has high photocatalytic activity.
[0006] The present invention provides a method for preparing a Ag2S / Ag composite nanosheet photocatalyst, and the specific steps are as follows: 1) Dissolve zinc nitrate and thiourea in a molar ratio of (1-3):(3-1) in 60 ml of ethylenediamine, and transfer the solution into a 100 ml reactor; 2) Keep the reactor at 140-220°C for 8-24 hours, and after cooling, wash the precipitate with deionized water and anhydrous ethanol respectively; 3) dissolving the precipitate obtained in step 2) in 60 ml of a 0.1-1 mol / L silver nitrate solution, and transferring the solution into a 100 ml reaction kettle; 4) The reactor was kept at 100-180° C. for 8-24 h. After cooling, the precipitate was washed with deionized water and anhydrous ethanol respectively to obtain Ag2S / Ag composite nanosheet photocatalyst.
[0007] Among them, Ag2S / Ag is a flake structure with an irregular shape, a length and width of 0.3~10μm, and an average thickness of 250nm; the flake structure is composed of particles, and the average diameter of these particles is 250nm and the average length is 0.5μm.
[0008] The preferred conditions of the method of the present invention are as follows: The molar ratio of zinc nitrate to thiourea in step 1) is (1:3) to (2:1); Step 2) The reaction kettle is reacted at 160-200°C for 10-18h; The concentration of silver nitrate in step 3) is 0.3-0.8 mol / L; In step 4), the reactor is reacted at 120-160° C. for 10-20 hours.
[0009] Beneficial effects of the present invention: 1. The present invention adopts a two-step solvothermal method to prepare Ag2S / Ag composite nanosheet photocatalyst using zinc nitrate, thiourea and ethylenediamine. The preparation process of the present invention is simple, easy to operate, has low production cost, and the raw materials are cheap and easy to obtain, and is easy to industrialize.
[0010] 2. The present invention uses less raw materials and has a simple process, which reduces adverse factors in the reaction process, so the product will not introduce impurities and has high purity.
[0011] 3. The Ag2S / Ag composite nanosheet photocatalyst obtained by the present invention has high activity under sunlight irradiation, and has the advantages of being easy to use, easy to recycle, and reusable when photocatalytically degrading organic dyes. The degradation rate of Rhodamine-B can reach more than 99.2% in 40 minutes. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 The X-ray diffraction (XRD) spectrum of the product obtained in Example 1 of the present invention is shown in FIG.
[0013] Figure 2 This is a scanning electron microscope (SEM) image of the product obtained in Example 1 of the present invention.
[0014] Figure 3 This is a scanning electron microscope (SEM) image of the product obtained in Example 1 of the present invention.
[0015] Figure 4 This is a scanning electron microscope (SEM) image of the product obtained in Example 1 of the present invention.
[0016] Figure 5 This is the full X-ray photoelectron spectroscopy (XPS) spectrum of the product obtained in Example 1 of the present invention.
[0017] Figure 6 This is the S 2p XPS fine XPS graph of the product obtained in Example 1 of the present invention.
[0018] Figure 7 The Ag 3d XPS fine XPS image of the product obtained in Example 1 of the present invention is Figure 8 The degradation rate curves of the products obtained in Examples 1 to 3 of the present invention vary with reaction time. DETAILED DESCRIPTION
[0019] The technical solution of the present invention is further explained and illustrated in the form of specific embodiments below.
[0020] Example 1 In the first step of solvothermal reaction, 2 mmol of zinc nitrate and 2 mmol of thiourea were first dissolved in 60 ml of ethylenediamine, and the solution was transferred to a 100 ml reactor; the reactor was then kept at 180° C. for 16 h, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol respectively.
[0021] In the second step, the precipitate obtained from the first step was dissolved in 60 ml of 1.0 mol / L silver nitrate solution, and the solution was transferred to a 100 ml reactor; the reactor was kept warm at 140° C. for 16 h, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol, respectively, to obtain an Ag2S / Ag composite nanosheet photocatalyst.
[0022] Figure 1 is the X-ray diffraction pattern of the product obtained in Example 1, Figure 1 As shown, the diffraction peaks of the obtained product are consistent with the diffraction peaks on the standard cards of monoclinic Ag2S (JCPDS No. 14-0072) and face-centered cubic Ag (JCPDS No. 04-0783), and no impurity phase peaks appear, indicating that the product contains Ag2S and Ag. Figure 2~Figure 4 : is the SEM picture of the product obtained in this embodiment. Figure 2 As shown, the product obtained in this embodiment is a sheet structure with a width of about 5 μm and a length of about 7 μm. Figure 3 and Figure 4 As shown, the average thickness of the product obtained in this example is about 250 nm. In addition, the plate-like structure is composed of particles, and the average diameter of these particles is about 250 nm and the average length is about 0.5 μm. Figure 5 This is the XPS full spectrum of the product obtained in this example. Figure 5 As shown, the product obtained in this embodiment contains four elements: S, Ag, C and O. Among them, the C element comes from the instrument itself, and O comes from H2O or CO2 adsorbed by the sample. Figure 6 and Figure 7 The S 2p XPS fine XPS pattern and the Ag 3d XPS fine XPS pattern of the obtained product are respectively.
[0023] Figure 8 Curve 1 in FIG. 1 is a curve of the degradation rate of rhodamine-B catalyzed by sunlight of the product obtained in this example. Figure 8 As shown in the middle curve 1, when the concentration of rhodamine-B solution is 8 mg / L, the power of the xenon lamp is 250 W, and the reaction time is 40 minutes, the degradation rate reaches 99.2%. Figure 8Curve 4 is the photocatalytic degradation curve of P25 under the same conditions. Under the same conditions, the degradation rate of P25 is 86.1%, which further illustrates that the product obtained in this experimental example has a better photocatalytic effect than P25.
[0024] Example 2 In the first step of solvothermal reaction, 1 mmol of zinc nitrate and 3 mmol of thiourea were first dissolved in 60 ml of ethylenediamine, and the solution was transferred to a 100 ml reactor; the reactor was then kept at 140° C. for 24 hours, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol respectively.
[0025] In the second step, the precipitate obtained from the first step was dissolved in 60 ml of 0.1 mol / L silver nitrate solution, and the solution was transferred to a 100 ml reactor; the reactor was kept warm at 180° C. for 8 h, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol, respectively, to obtain an Ag2S / Ag composite nanosheet photocatalyst.
[0026] like Figure 8 As shown in curve 2, when the concentration of rhodamine-B solution is 8 mg / L, the power of the xenon lamp is 250 W, and the reaction time is 40 minutes, the degradation rate reaches 95.2%. Figure 8 Curve 4 is the photocatalytic degradation curve of P25 under the same conditions. Under the same conditions, the degradation rate of P25 is 86.1%, which further illustrates that the product obtained in this experimental example has a better photocatalytic effect than P25.
[0027] Example 3 In the first step of solvothermal reaction, 3 mmol of zinc nitrate and 1 mmol of thiourea were first dissolved in 60 ml of ethylenediamine, and the solution was transferred to a 100 ml reactor; the reactor was then kept at 220° C. for 8 h, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol respectively.
[0028] In the second step, the precipitate obtained from the first step was dissolved in 60 ml of 0.5 mol / L silver nitrate solution, and the solution was transferred to a 100 ml reactor; the reactor was kept warm at 120° C. for 24 h, and after cooling, the precipitate was washed with deionized water and anhydrous ethanol, respectively, to obtain an Ag2S / Ag composite nanosheet photocatalyst.
[0029] like Figure 8 As shown in curve 3, when the concentration of rhodamine-B solution is 8 mg / L, the power of the xenon lamp is 250 W, and the reaction time is 45 minutes, the degradation rate reaches 89.2%. Figure 8Curve 4 is the photocatalytic degradation curve of P25 under the same conditions. Under the same conditions, the degradation rate of P25 is 86.1%, which further illustrates that the product obtained in this experimental example has a better photocatalytic effect than P25.
[0030] In the present invention, a two-step solvothermal reaction is used, wherein the first step generates ZnS(en) 0.5 Nanosheet template, second step reaction ZnS(en) 0.5 In the reactor, 0.5 ethylenediamine is removed to generate ZnS. At the same time, due to the presence of Ag in the solution, + , and the solubility product of Ag2S is much smaller than that of ZnS, so all ZnS is converted into Ag2S, and the product retains the morphology and size of the template. + During the high-pressure process in the reactor, it is reduced to metallic Ag and distributed in the Ag2S nanosheets, eventually forming an Ag2S / Ag composite nanosheet structure.
Claims
1. A method for preparing a Ag2S / Ag composite nanosheet photocatalyst, characterized in that: The specific steps are as follows: 1) Dissolve zinc nitrate and thiourea in a molar ratio of (1-3):(3-1) in 60 ml of ethylenediamine, and transfer the solution into a 100 ml reactor; 2) Keep the reactor at 140-220°C for 8-24 hours, and after cooling, wash the precipitate with deionized water and anhydrous ethanol respectively; 3) dissolving the precipitate obtained in step 2) in 60 ml of a 0.1-1 mol / L silver nitrate solution, and transferring the solution into a 100 ml reaction kettle; 4) The reactor was kept at 100-180° C. for 8-24 h. After cooling, the precipitate was washed with deionized water and anhydrous ethanol respectively to obtain Ag2S / Ag composite nanosheet photocatalyst.
2. The method for preparing the Ag2S / Ag composite nanosheet photocatalyst according to claim 1, characterized in that: The molar ratio of zinc nitrate to thiourea in step 1) is (1:3) to (2:1).
3. The method for preparing the Ag2S / Ag composite nanosheet photocatalyst according to claim 1, characterized in that: In step 2), the reactor is reacted at 160-200° C. for 10-18 hours.
4. The method for preparing the Ag2S / Ag composite nanosheet photocatalyst according to claim 1, characterized in that: The concentration of silver nitrate in step 3) is 0.3-0.8 mol / L.
5. The method for preparing the Ag2S / Ag composite nanosheet photocatalyst according to claim 1, characterized in that: In step 4), the reactor is reacted at 120-160° C. for 10-20 hours.
6. An Ag2S / Ag composite nanosheet photocatalyst prepared by the method according to any one of claims 1 to 5, characterized in that: Ag2S / Ag is a flake structure with an irregular shape, a length and a width of 0.3-10 μm, and an average thickness of 250 nm; the flake structure is composed of particles, and the average diameter of the particles is 250 nm and the average length is 0.5 μm.