An S8 polymer composite photocatalyst and its preparation method and application

Abstract

The present invention provides an S8 polymer photocatalyst, a preparation method and an application thereof, and belongs to the technical field of material synthesis and catalysts. The present invention utilizes a low-temperature polymerization method and a self-assembly method to synthesize an S8 polymer composite photocatalyst. The S8 polymer composite photocatalyst is assembled from three-dimensional spherical S8 and two-dimensional GCN nanosheets, and is a special mesoporous material. The S8 polymer composite photocatalyst has the advantages of a large secondary structure specific surface area, multiple active sites, and a strong separation and transmission capability of photogenerated charges and carriers, and exhibits excellent photocatalytic hydrogen production activity under visible light irradiation. In addition, the preparation process of the S8 polymer composite photocatalyst is simple, the operation is convenient, and the reaction time is short, which can effectively reduce energy consumption and production costs, and is convenient for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of material synthesis and catalysts, and specifically relates to an S8 polymer composite photocatalyst and a preparation method and application thereof. Background Art

[0002] Energy shortages and environmental pollution are major global challenges, making the development of reusable, clean, and renewable energy crucial. Solar energy is an inexhaustible, green energy source with promising applications. Semiconductor-based photocatalytic hydrogen production is considered one of the most promising technologies for photochemical conversion, harnessing solar energy to generate high-calorific-value, zero-pollution, and sustainable clean energy.

[0003] Currently, the large-scale application of photocatalytic hydrogen production still faces key scientific challenges. Existing photocatalysts present several challenges, such as low light absorption, carrier recombination losses, and insufficient catalytic active sites. Therefore, it is necessary to develop new high-performance, highly stable, and low-cost photocatalysts to improve the efficiency and affordability of photocatalytic hydrogen production. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides an S8 polymer composite photocatalyst, a preparation method thereof, and an application thereof. The present invention utilizes a low-temperature polymerization method and a self-assembly method to synthesize the S8 polymer composite photocatalyst. The S8 polymer composite photocatalyst is assembled from a three-dimensional spherical S8 polymer and a two-dimensional GCN nanosheet, and is a special mesoporous material. The S8 polymer composite photocatalyst has the advantages of a large secondary structure specific surface area, multiple active sites, and a strong separation and transmission capability of photogenerated charges and carriers, and exhibits excellent photocatalytic hydrogen production activity under visible light irradiation. In addition, the preparation process of the S8 polymer composite photocatalyst is simple, the operation is convenient, and the reaction time is short, which can effectively reduce energy consumption and production costs, and is convenient for large-scale production.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical means.

[0006] The present invention first provides an S8 polymer composite photocatalyst, in which three-dimensional spherical S8 polymers are uniformly embedded in two-dimensional GCN nanosheets; the three-dimensional spherical S8 polymers are formed by disordered stacking of S8 nanosheets, and the average diameter of the three-dimensional spherical S8 polymers is about 70-160nm.

[0007] The present invention also provides a method for preparing the above-mentioned S8 polymer composite photocatalyst, which specifically comprises the following steps:

[0008] (1) dissolving thiocyanate in sodium hydroxide solution to obtain solution A after reaction;

[0009] (2) Saturated potassium iodide solution was slowly added dropwise to solution A to obtain turbid liquid B; liquid B was then placed in an ice-water bath for reaction, and after the reaction was completed, the solution was naturally cooled to room temperature, and then centrifuged, washed, and vacuum-dried to obtain S8 polymer;

[0010] (3) The S8 polymer and the catalyst graphite phase carbon nitride are uniformly ground and then calcined, and the S8 polymer composite photocatalyst is obtained after the calcination is completed.

[0011] Preferably, in step (1), the volume ratio of thiocyanate to sodium hydroxide solution is 1:3; the concentration of sodium hydroxide solution is 0.5 to 0.7 mol L -1 .

[0012] Preferably, in step (1), the reaction conditions of the solution A are to react at room temperature for 10 to 15 minutes.

[0013] Preferably, in step (2), the volume ratio of solution A to saturated potassium iodide solution is 10:1.

[0014] Preferably, in step (2), the reaction is carried out at 0-5°C for 8-48 hours.

[0015] Preferably, in step (3), in the S8 polymer composite photocatalyst, the mass percentage of the S8 polymer and the two-dimensional GCN nanosheets is 1 to 7%.

[0016] Preferably, in step (3), the calcination conditions are: heating to 500° C. and calcining for 4 to 6 hours in a nitrogen atmosphere.

[0017] Preferably, the heating rate of calcination is 2.5-5°C min -1 .

[0018] The present invention also provides the use of the above-mentioned S8 polymer composite photocatalyst in catalytic hydrogen production under visible light.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Compared with the photocatalysts in the prior art, the S8 polymer composite photocatalyst prepared by the present invention has the following advantages:

[0021] (1) The S8 polymer composite photocatalyst of the present invention has good water dispersibility. Due to the inherently poor water dispersibility of sulfur, sulfur nanomaterials such as sulfur nanoparticles, sulfur nanorods, and sulfur nanowires have not received much attention until the synthesis of sulfur quantum dots with good water dispersibility. The present invention uses low-temperature polymerization and self-assembly methods to control the nanostructure and morphology of the S8 polymer composite photocatalyst, achieving the stable existence of sulfur in the form of a well-dispersible S8 layered structure, thereby meeting the requirements of different reactions.

[0022] (2) The S8 polymer composite photocatalyst of the present invention has excellent light absorption capacity. Due to the problems of low specific surface area and limited visible light absorption capacity of GCN. The S8 polymer obtained by the present invention using a unique preparation process is a three-dimensional spherical structure formed by disordered stacking of two-dimensional nanosheets. It has the advantages of large specific surface area of ​​secondary structure, many active sites, and strong separation and transmission capacity of photogenerated charges and carriers. At the same time, the three-dimensional structure can also serve as a support, avoiding the agglomeration problem caused by van der Waals force and providing a path for electron transfer. In addition, the multiple reflection effect of incident photons in the interconnected open framework structure of the three-dimensional structure S8 can effectively improve the light absorption capacity and improve the utilization rate of light energy. Therefore, the S8 polymer is embedded in the GCN structure, and the obtained S8 polymer composite photocatalyst has a photocatalytic hydrogen production rate increased by 9.52 times compared with the GCN photocatalyst.

[0023] (3) The S8 polymer composite photocatalyst of the present invention has environmentally friendly properties. Sulfur is widely present in the earth's crust and the earth's environment and is an abundant natural resource. The use of sulfur to prepare catalysts can reduce dependence on scarce and limited resources, thereby promoting sustainable development and environmental protection. In addition, sulfur itself has low toxicity and environmental impact. Compared with other common metal catalysts such as platinum and rhodium, the use of sulfur as a catalyst can reduce potential harm to human health and the environment. This provides a new approach for the development of sustainable energy and clean fuels, and helps promote the development and application of green energy technologies.

[0024] (4) The S8 polymer composite photocatalyst prepared by the present invention is convenient for large-scale production. The S8 polymer composite photocatalyst prepared by the present invention has the advantages of simple process, convenient operation, and short reaction time, thereby reducing energy consumption and production costs, and facilitating large-scale production. Furthermore, the S8 polymer composite photocatalyst is non-toxic and harmless, meeting environmental requirements, further highlighting its benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD spectrum of S8 polymer.

[0026] Figure 2SEM photos of S8 polymer (a) and SEM photos of S8 polymer composite photocatalyst (b).

[0027] Figure 3 TEM photo of S8 polymer (a) and characterization diagrams of S8 polymer composite photocatalyst (b~h); among them, b is the TEM photo of S8 polymer composite photocatalyst, c is the HRTEM photo, d is the HRTEM photo, and e~h are STEM-EDX element surface scanning photos.

[0028] Figure 4 The photocatalytic hydrogen production kinetic curve of S8 polymer composite photocatalyst under visible light (a) and the kinetic curve after five cycles (b).

[0029] Figure 5 UV-vis DRS curve of S8 polymer composite photocatalyst (a) and light absorption quantum efficiency of S8 polymer composite photocatalyst (b).

[0030] Figure 6 PL spectrum (a) and TS-PL decay curve (b) of S8 polymer composite photocatalyst.

[0031] Figure 7 The photocatalytic hydrogen production kinetic curve of S8 polymer composite photocatalyst under visible light (a) and the kinetic curve after five cycles (b).

[0032] Figure 8 This is the photocurrent response curve of the S8 polymer composite photocatalyst.

[0033] Figure 9 The hydrogen production rate of different samples is shown in Figure 2. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0035] Example 1: Preparation of S8 polymer composite photocatalyst

[0036] (1) Dissolve 2.4 g of sodium hydroxide in 100 mL of deionized water to obtain a sodium hydroxide solution; dissolve 3.54 g of trithiocyanate in the sodium hydroxide solution and react for 24 hours to obtain solution A.

[0037] (2) Accurately weigh 10 g of potassium iodide and dissolve it in 10 mL of deionized water to obtain a saturated potassium iodide solution. Slowly add 10 mL of the saturated potassium iodide solution dropwise to solution A to obtain a turbid liquid B. Liquid B is then placed in an ice-water bath and reacted at 0°C for 8 h. After cooling naturally to room temperature, the solution is centrifuged and washed alternately with anhydrous ethanol and distilled water, dried, and then dried in a vacuum drying oven at 80°C for 12 h.

[0038] (3) 0.0042 g of S8 polymer and 1 g of graphite carbon nitride (GCN) catalyst were uniformly ground and then heated at 5 °C min in a nitrogen atmosphere. -1 The temperature was raised to 500° C. and calcined at a rate of 1000° C. and maintained for 4 hours. After the calcination, the S8 polymer composite photocatalyst was obtained, which was named 1%-S8 polymer composite photocatalyst.

[0039] In this example, the S8 polymer composite photocatalyst was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental surface scanning (EDS), and the like.

[0040] Figure 1 The XRD spectrum of the S8 polymer is shown in Figure 2. As can be seen, the diffraction peaks of the S8 polymer are consistent with the standard spectrum of PDF#8507991. This indicates that the crystal structure and phase composition of the S8 polymer analyzed by XRD are completely consistent with the standard comparison card, indicating that the S8 polymer was successfully prepared.

[0041] Figure 2 The SEM images of S8 polymer (a) and S8 polymer composite photocatalyst (b) are shown. Figure 2 In a, we can see that S8 has a 3D spherical structure. Figure 2 In b, 3D spherical S8 polymers are distributed on 2D GCN nanosheets. This indicates that S8 has a 3D microstructure and the S8 polymer composite photocatalyst is a microstructure composed of 2D nanosheets and 3D spherical structures.

[0042] Figure 3 The TEM image of S8 polymer (a) and the characterization images of S8 polymer composite photocatalyst (b~h); among them, b is the TEM image of S8 polymer composite photocatalyst, c is the HRTEM image, d is the HRTEM image, and e~h are STEM-EDX element surface scanning images. Figure 3 In a, the S8 polymer is an irregular 3D spherical structure formed by the accumulation of S8 nanosheets. This structure shortens the electron transmission path, allowing electrons to be freely transmitted between nanosheets, reducing the obstacles to electron transmission, improving the electron transmission efficiency, and facilitating the separation and utilization of photogenerated electron-hole pairs. Figure 3In Figure b, the irregular three-dimensional spherical structure formed by the accumulation of S8 nanosheets in the S8 polymer is fully preserved and embedded within the 2D GCN structure. In addition, in the STEM-EDX elemental map of the S8 polymer composite photocatalyst (Figure ch), C, N, O, and S elements are all detected and exhibit a uniform characteristic distribution, further confirming the successful preparation of the S8 polymer composite photocatalyst.

[0043] Example 2: Preparation of S8 polymer composite photocatalyst

[0044] (1) Dissolve 2.4 g of sodium hydroxide in 100 mL of deionized water to obtain a sodium hydroxide solution; dissolve 3.54 g of trithiocyanate in the sodium hydroxide solution and react for 24 hours to obtain solution A.

[0045] (2) Accurately weigh 10 g of potassium iodide and dissolve it in 10 mL of deionized water to obtain a saturated potassium iodide solution. Slowly add 10 mL of the saturated potassium iodide solution dropwise to solution A to obtain a turbid liquid B. Liquid B is then placed in an ice-water bath and reacted at 0°C for 8 h. After cooling naturally to room temperature, the solution is centrifuged and washed alternately with anhydrous ethanol and distilled water, dried, and dried in a vacuum drying oven at 60°C for 12 h.

[0046] (3) 0.0126 g of S8 polymer and 1 g of catalyst graphite carbon nitride (GCN) were uniformly ground and then heated in a nitrogen atmosphere at 5 °C min -1 The temperature was raised to 500° C. and calcined at a rate of 1000° C. and maintained for 4 hours. After the calcination, the S8 polymer composite photocatalyst was obtained, which was named 3%-S8 polymer composite photocatalyst.

[0047] Example 3: Preparation of S8 polymer composite photocatalyst

[0048] (1) Dissolve 2.4 g of sodium hydroxide in 100 mL of deionized water to obtain a sodium hydroxide solution; dissolve 3.54 g of trithiocyanate in the sodium hydroxide solution and react for 24 hours to obtain solution A.

[0049] (2) Accurately weigh 10 g of potassium iodide and dissolve it in 10 mL of deionized water to obtain a saturated potassium iodide solution. Slowly add 10 mL of the saturated potassium iodide solution dropwise to solution A to obtain a turbid liquid B. Liquid B is then placed in an ice-water bath and reacted at 0°C for 8 h. After cooling naturally to room temperature, the solution is centrifuged and washed alternately with anhydrous ethanol and distilled water, dried, and dried in a vacuum drying oven at 70°C for 12 h.

[0050] (3) 0.021 g of S8 polymer and 1 g of catalyst graphite carbon nitride (GCN) were uniformly ground and then heated in a nitrogen atmosphere at 5 °C min-1 The temperature was raised to 500° C. and calcined at a rate of 1000° C. and maintained for 4 hours. After the calcination, the S8 polymer composite photocatalyst was obtained, which was named 5%-S8 polymer composite photocatalyst.

[0051] Example 4: Preparation of S8 polymer composite photocatalyst

[0052] (1) Dissolve 2.4 g of sodium hydroxide in 100 mL of deionized water to obtain a sodium hydroxide solution; dissolve 3.54 g of trithiocyanate in the sodium hydroxide solution and react for 24 hours to obtain solution A.

[0053] (2) Accurately weigh 10 g of potassium iodide and dissolve it in 10 mL of deionized water to obtain a saturated potassium iodide solution. Slowly add 10 mL of the saturated potassium iodide solution dropwise to solution A to obtain a turbid liquid B. Liquid B is then placed in an ice-water bath and reacted at 0°C for 8 h. After cooling naturally to room temperature, the solution is centrifuged and washed alternately with anhydrous ethanol and distilled water, dried, and dried in a vacuum drying oven at 70°C for 12 h.

[0054] (3) 0.0294 g of S8 polymer and 1 g of catalyst graphite carbon nitride (GCN) were uniformly ground and then heated in a nitrogen atmosphere at 5 °C min -1 The temperature was raised to 500° C. and calcined at a rate of 1000° C. and maintained for 4 hours. After the calcination, the S8 polymer composite photocatalyst was obtained, which was named 7%-S8 polymer composite photocatalyst.

[0055] In this example, the ability and stability of the S8 polymer composite photocatalyst prepared in Examples 1 to 4 to produce hydrogen under visible light were also investigated.

[0056] Figure 4 The following are the kinetic curves of photocatalytic hydrogen production under visible light by the S8 polymer composite photocatalyst (a) and the kinetic curve after five cycles (b). As can be seen from the figure, the photocatalytic hydrogen production rate of the S8 polymer composite photocatalyst is 9.52 times that of the GCN photocatalytic hydrogen production rate. Moreover, the activity of the S8 polymer composite photocatalyst remains basically unchanged after 20 hours of five cycles of reaction. This shows that the S8 polymer composite photocatalyst is significantly superior to the GCN photocatalyst in terms of hydrogen production activity, that is, it can produce more hydrogen under the same conditions. In addition, the S8 polymer composite photocatalyst can work continuously for 20 hours and still has high activity, which is very friendly to industrial applications or long-term experiments because it reduces the frequency of catalyst replacement and maintenance.

[0057] Figure 5 UV-vis DRS curve of S8 polymer composite photocatalyst (a) and light absorption quantum efficiency of S8 polymer composite photocatalyst (b). Figure 5In a, the light absorption characteristics of S8 and S8 polymer composite photocatalysts were analyzed by UV-vis DRS. It can be seen that S8 polymer and S8 polymer composite photocatalysts have obvious visible light absorption ability, and their absorption edges are 420nm and 425nm respectively. Figure 5 Figure b shows the quantum efficiency of the S8 polymer composite photocatalyst under different fixed wavelengths of monochromatic light, with the optimal quantum efficiency reaching 30.1% at 400 nm. This indicates that the S8 polymer composite photocatalyst has a high quantum efficiency at 400 nm. However, high quantum efficiency means that more incident photons are effectively converted into the desired catalytic reactants. Therefore, the S8 polymer composite photocatalyst can more effectively utilize light energy.

[0058] Figure 6 PL spectrum (a) and TS-PL decay curve (b) of S8 polymer composite photocatalyst. Figure 6 a It can be seen that the S8 polymer composite photocatalyst has a mesoporous structure, which is beneficial to the mass transfer of reactant and product molecules, thereby promoting the photocatalytic hydrogen production reaction. Figure 6 This is also confirmed by the pore size distribution centered at 39 nm in b.

[0059] This example also studies the dynamic behavior of photogenerated carriers in the S8 polymer composite photocatalyst through photochemistry and photoelectrochemistry.

[0060] Figure 7 The photocatalytic hydrogen production kinetic curve of S8 polymer composite photocatalyst under visible light (a) and the kinetic curve of five cycles (b). Figure 7 (a, b) PL and TS-PL curves show that the S8 polymer composite photocatalyst exhibits a strong PL emission peak near 440 nm. Fitting the TS-PL decay curve yields a fluorescence lifetime of 1.13 ns for the S8 polymer composite photocatalyst. This indicates that the S8 polymer composite photocatalyst has a short fluorescence lifetime, suggesting that the S8 polymer composite photocatalyst produces the desired reactants in a short time, thereby reducing unnecessary side reactions or competing reactions and improving catalytic selectivity.

[0061] Figure 8 This is the photocurrent response curve of the S8 polymer composite photocatalyst. As can be seen from Figure (a), the S8 polymer composite photocatalyst has light response ability.

[0062] Figure 9The graph below shows the hydrogen production rates for different samples. As can be seen from the figure, the S8 polymer composite photocatalytic activity is 1.50 times and 1.59 times that of the S-doped photocatalyst and SCN / PCN photocatalyst, respectively. Therefore, the S8 polymer composite photocatalyst exhibits superior photocatalytic hydrogen production activity compared to the S-doped photocatalyst and SCN / PCN photocatalyst.

[0063] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing an S8 polymer composite photocatalyst, characterized in that: include: (1) Dissolve thiocyanate in sodium hydroxide solution to obtain solution A after reaction; (2) Saturated potassium iodide solution was slowly added dropwise to solution A to obtain turbid liquid B; liquid B was then placed in an ice-water bath for reaction. After the reaction was completed, the solution was naturally cooled to room temperature, and then centrifuged, washed, and vacuum-dried to obtain S8 polymer; (3) The S8 polymer and graphite phase carbon nitride are uniformly ground and then calcined, and the S8 polymer composite photocatalyst is obtained after the calcination is completed.

2. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: In step (1), the concentration of the sodium hydroxide solution is 0.5~0.7mol·L -1 .

3. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: In step (2), the volume ratio of solution A to saturated potassium iodide solution is 10:

1.

4. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: In step (2), the reaction is carried out at 0°C for 8 to 48 hours.

5. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: In step (3), in the S8 polymer composite photocatalyst, the mass percentage of the S8 polymer and the two-dimensional GCN nanosheets is 1-7%.

6. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: In step (3), the calcination conditions are: heating to 500° C. in a nitrogen atmosphere and calcining for 4 to 6 hours.

7. The method for preparing the S8 polymer composite photocatalyst according to claim 1, characterized in that: The heating rate of calcination is 2.5~5℃·min -1 .

8. The S8 polymer composite photocatalyst prepared by the method according to any one of claims 1 to 7, characterized in that: In the S8 polymer composite photocatalyst, three-dimensional spherical S8 polymers are uniformly embedded in two-dimensional GCN nanosheets; the three-dimensional spherical S8 polymers are formed by disordered stacking of S8 nanosheets, and the average diameter of the three-dimensional spherical S8 polymers is 70-160 nm.

9. Use of the S8 polymer composite photocatalyst prepared by the method according to any one of claims 1 to 7 or the S8 polymer composite photocatalyst according to claim 8 in catalytic hydrogen production under visible light.

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