Synthetic method of SWCNT-coated ZnIn2S4 nano composite material and photocatalyst

Abstract

The invention discloses a synthetic method and a photocatalyst of an SWCNT-coated ZnIn2S4 nano composite material, and the synthetic method comprises the following steps: (1) putting SWCNT powder into a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1: (2.8-3.2), carrying out ultrasonic treatment for 8-10 hours, taking a solid, washing, and freeze-drying to obtain carboxylated SWCNT powder; (2) dispersing the carboxylated SWCNT powder in a glycerol aqueous solution, continuously adding a zinc salt, an indium salt and a sulfur source, dissolving, heating to 75-85 DEG C, keeping for 1.5-2.5 hours, taking a precipitate, washing, and freeze-drying to obtain an SWCNT coated ZnIn2S4 nano composite material; the molar ratio of the zinc salt to the indium salt to the sulfur source is 1: 2: (4-6); the addition proportion of the carboxylated SWCNT powder is 0.01 to 0.6 percent according to the theoretical mass of the final product ZnIn2S4. According to the invention, the SWCNT of 1D and the ZnIn2S4 nanostructure of 3D are combined to form an efficient heterojunction, so that the photocatalytic hydrogen production performance is remarkably improved, and meanwhile, the carbon consumption is reduced.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing a SWCNT@ZnIn2S4 nanocomposite material, and also relates to a photocatalyst. Background Art

[0002] The development of clean and renewable energy is a current research hotspot. As a highly efficient and clean energy carrier, hydrogen has the characteristics of high calorific value and zero pollution emissions, and is considered an important part of the future energy system. The photocatalytic water splitting technology for hydrogen production uses solar energy to decompose water into hydrogen and oxygen, and is a very promising green energy preparation method.

[0003] As a typical layered sulfide semiconductor material, ZnIn2S4 has received extensive attention in the field of photocatalysis due to its suitable band gap structure (about 2.0 - 2.4 eV), excellent light absorption performance, and good chemical stability. However, pure ZnIn2S4 materials have problems such as a fast recombination rate of photo-generated electron-hole pairs and low carrier migration efficiency, which limit the further improvement of their photocatalytic performance. Carbon materials have excellent electrical conductivity, high specific surface area, and good chemical stability, and are ideal modifiers for photocatalytic materials. Combining carbon materials with ZnIn2S4 can construct an efficient heterojunction structure to promote the separation and transport of photo-generated carriers, thereby significantly improving the photocatalytic performance.

[0004] The invention patent application with the publication number CN 117399032 A discloses a C@ZnIn2S4 / noble metal photo-driven micro-motor catalyst and its preparation method and application. This method uses an oil bath method to in-situ grow ZnIn2S4 on the inner and outer surfaces of carboxylated hollow carbon microtubes to obtain a C@ZnIn2S4 photocatalyst or a C@ZnIn2S4 / Au catalyst. In this method, the used carbon tubes are micron-sized, the addition amount of carbon tubes is large, and a noble metal is required as a co-catalyst. For the prepared catalyst, the hydrogen production amount does not increase linearly over time, and the hydrogen production amount after 2 hours is basically the same as that after 1 hour, and as the number of cycles increases, the stability gradually decreases. The invention patent application with the publication number CN 116851007 A uses carbon nanotubes to prepare a carbon nanotube-zinc indium sulfide nanosheet composite material, and the carbon nanotubes uniformly form a network structure inside the semiconductor photocatalytic material. This method must reduce the carbon tube usage, but a hydrothermal method is required, with high temperature and high pressure, harsh conditions, the required amount of carbon nanotubes is still large, and an external magnetic field is required to further increase the catalytic hydrogen production rate, increasing the preparation cost and technical difficulty. Summary of the Invention

[0005] Objective of the Invention: The objective of the present invention is to provide a method for synthesizing SWCNT@ZnIn2S4 nanocomposites, so as to reduce the dosage of carbon nanotubes and simultaneously improve the photocatalytic hydrogen production performance of the SWCNT@ZnIn2S4 nanocomposites.

[0006] Technical Solution: A method for synthesizing SWCNT@ZnIn2S4 nanocomposites according to the present invention includes the following steps:

[0007] (1) Put SWCNT powder into a mixed solution with a volume ratio of nitric acid to sulfuric acid of 1:2.8 - 3.2, perform ultrasonic treatment for 8 - 10 hours, take the solid, wash it, and freeze-dry it to obtain carboxylated SWCNT powder;

[0008] (2) Disperse the carboxylated SWCNT powder in an aqueous glycerol solution, then continue to add zinc salt, indium salt, and sulfur source, dissolve them, heat to 75 - 85 °C and maintain for 1.5 - 2.5 hours, take the precipitate, wash it, and freeze-dry it to obtain SWCNT@ZnIn2S4 nanocomposites; the molar ratio of the zinc salt, indium salt, and sulfur source is 1:2:4 - 6; based on the theoretical mass of the final product ZnIn2S4, the addition ratio of the carboxylated SWCNT powder is 0.01 - 0.6%.

[0009] Preferably, in step (2), in the aqueous glycerol solution, the volume fraction of glycerol is 15 - 25%.

[0010] Preferably, in step (1), SWCNT powder pre-purification is also included, and the purification method is: take SWCNT powder, put it into a nitric acid solution with a mass fraction of 18 - 22%, stir at room temperature for 11 - 13 hours, take the solid, wash it, and freeze-dry it to obtain pre-purified SWCNT powder. Preferably, in steps (1) and (2), deionized water and ethanol are used for washing.

[0011] Preferably, in step (2), take the carboxylated SWCNT powder, perform ultrasonic treatment for 4 - 6 hours to disperse it in the aqueous glycerol solution.

[0012] Preferably, in step (1), the zinc salt is ZnCl2, the indium salt is InCl3·4H2O, and the sulfur source is thioacetamide.

[0013] Preferably, in step (1), based on the theoretical mass of the final product ZnIn2S4, the addition ratio of the carboxylated SWCNT powder is 0.05 - 0.3%.

[0014] Preferably, in step (1), the mass fraction of nitric acid is 65 - 68%, and the mass fraction of sulfuric acid is 95 - 98%.

[0015] Preferably, in steps (1) and (2), the power used during ultrasonic treatment is 500 kW to 1000 kW.

[0016] A photocatalyst, comprising the SWCNT@ZnIn2S4 nanocomposite synthesized by the aforementioned synthesis method.

[0017] Preferably, in the SWCNT@ZnIn2S4 nanocomposite, the ZnIn2S4 nanostructure grows in-situ along the tube wall of the SWCNT.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: 1. Reducing the dosage of carbon nanotubes while improving the photocatalytic hydrogen production performance of the SWCNT@ZnIn2S4 nanocomposite: By using carboxylated SWCNT as a substrate and growing ZnIn2S4 nanostructures in-situ on its surface using an oil bath method to form a 1D / 3D nanocomposite, this composite material has excellent dispersibility, a high specific surface area, and a tight heterojunction interface, significantly improving the separation efficiency of photo-generated carriers and the photocatalytic hydrogen production performance. The hydrogen production rate of the obtained material is increased to 2122 μmol·h -1 ·g -1 , without auxiliary conditions. Calculated based on the theoretical mass of the final product ZnIn2S4, the addition ratio of carbon nanotubes is not higher than 0.5%, and can be further reduced to 0.3% and below, reducing the synthesis cost; 2. Mild reaction conditions and simple process: It can be obtained under normal pressure oil bath without high temperature and high pressure, reducing the synthesis difficulty; 3. The obtained material has excellent cycle stability and can be reused: The in-situ construction makes the heterojunction interface tighter. From the results of the stable cycle test, the photocorrosion of ZnIn2S4 is inhibited; 4. It provides a new idea for the development of high-efficiency photocatalytic materials. Description of the Drawings

[0019] Figure 1 It is a TEM morphology diagram of the carboxylated SWCNT prepared in the first embodiment of the present invention;

[0020] Figure 2 It is a TEM morphology diagram of pure ZnIn2S4 prepared in the first comparative example of the present invention;

[0021] Figure 3 It is a TEM morphology diagram of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the second embodiment of the present invention;

[0022] Figure 4 It is a TEM morphology diagram of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the first embodiment of the present invention;

[0023] Figure 5TEM morphology of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the third embodiment of the present invention;

[0024] Figure 6 EDS mapping morphology of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the first embodiment of the present invention;

[0025] Figure 7 Raman spectra of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the first embodiment of the present invention and pure ZnIn2S4 prepared in the first comparative example;

[0026] Figure 8 Transient photocurrent response curves of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the first embodiment of the present invention and pure ZnIn2S4 prepared in the first comparative example;

[0027] Figure 9 Performance test chart of photocatalytic hydrogen production of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in different embodiments of the present invention;

[0028] Figure 10 Stability cycle test chart of photocatalytic hydrogen production of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in the first embodiment of the present invention. Detailed implementation manners

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0030] Example 1: Preparation of 0.3% SWCNT@ZnIn2S4 nanocomposite

[0031] (1) Purification of single-walled carbon nanotubes (SWCNT): Take 100 mg of SWCNT and place it in 100 ml of a nitric acid solution with a mass fraction of 20%, stir magnetically for 12 hours. After stirring, filter to obtain the solid, and successively filter and wash the solid with deionized water and ethanol 2 - 3 times until the washing liquid is neutral. Then place the solid in a freeze dryer for drying to obtain purified SWCNT powder.

[0032] (2) Carboxylation of SWCNT: Take 50 mg of purified SWCNT powder and place it in a mixed solution of 50 ml of concentrated nitric acid (mass fraction about 65 - 68%) and concentrated sulfuric acid (mass fraction about 95 - 98%) with a volume ratio of 1:3. Ultrasonic it with a 500w ultrasonic cleaner for 10 hours. After ultrasonic treatment, filter to obtain the solid, and wash the solid with deionized water and ethanol 2 - 3 times until the washing liquid is neutral. Then place it in a freeze dryer for drying to obtain carboxylated SWCNT powder.

[0033] (3) Growth of in-situ ZnIn2S4 nanostructures: Weigh 3 mg of carboxylated SWCNT powder and put it into 80 mL of deionized water. Then add 20 mL of glycerol solution and ultrasonically treat it at 500 w for 4 hours (power) to obtain a uniformly dispersed mixture. Subsequently, add 1.8 mmol of ZnCl2, 3.6 mmol of InCl3·4H2O, and 9.6 mmol of thioacetamide to the mixture and stir until all the solid drugs are dissolved. Place the mixture in an oil bath, stir, and control the temperature of the oil bath to rise to 80 °C and maintain it for 2 hours. After the oil bath ends, perform suction filtration to obtain a precipitate. Wash the precipitate with deionized water and ethanol repeatedly 2 - 3 times and then put it into a freeze dryer for drying to obtain the SWCNT@ZnIn2S4 nanocomposite. Calculated based on the theoretical mass of the final product ZnIn2S4 (the relative molecular mass of ZnIn2S4 is about 537.8, and the theoretical yield is about 968.04 mg), in the SWCNT@ZnIn2S4 nanocomposite obtained in this example, the mass fraction of SWCNT is about 0.3%, denoted as 0.3% SWCNT@ZnIn2S4.

[0034] Example 2: Preparation of 0.1% SWCNT@ZnIn2S4 nanocomposite. The preparation method of the materials in this example is the same as that in Example 1, except that in step (3), the addition amount of carboxylated SWCNT powder is 1 mg.

[0035] Example 3: Preparation of 0.5% SWCNT@ZnIn2S4 nanocomposite. The preparation method of the materials in this example is the same as that in Example 1, except that in step (3), the addition amount of carboxylated SWCNT powder is 5 mg.

[0036] Comparative Example 1: According to step (3) of Example 1, omit the carboxylated SWCNT powder to prepare pure ZnIn2S4.

[0037] Comparative Example 2: Preparation of SWCNT@ZnIn2S4 nanocomposite with 0.3% SWCNT. The preparation method of the materials in this comparative example is the same as that in Example 1. The difference is that in step (3), the washed solid is dried in an oven, and the drying conditions are: 80 °C, 24 hours. The SWCNT@ZnIn2S4 nanostructures in the obtained materials are damaged and severely agglomerated, and the catalytic performance drops significantly. The reason may be that as the water content is lost, the nanoflower or nanowire structures adhere to each other, resulting in agglomeration of nanoparticles or destruction of the structure, affecting their performance. During freeze drying, the solution-like nanocomposite is first frozen to maintain the microscopic morphology, and then vacuumed to slowly remove the water molecules between the nanomaterials. The ice directly sublimes into gas and is removed, which can better maintain the original structure and dispersion of the nanomaterials and reduce agglomeration.

[0038] The SWCNT@ZnIn2S4 nanocomposites prepared in Examples 1 to 3 and the pure ZnIn2S4 prepared in Comparative Example 1 were characterized and subjected to performance tests. The results of the characterization and performance tests are as Figures 1 to 10 shown.

[0039] Figure 1 It can be seen that the diameter of the carboxylated single-walled carbon nanotubes is about 5 nm and can reach dozens of micrometers in length. The breakage of the tube wall indicates that the single-walled carbon nanotubes are well carboxylated.

[0040] Figure 2 Figure 11 shows the TEM morphology of the pure ZnIn2S4 obtained in Comparative Example 1. The left figure is at low magnification and the right one is at high magnification. It can be seen from the figure that the pure ZnIn2S4 is prone to aggregation, has very poor dispersibility and a small specific surface area; Figures 3 to 5 Figures 13(a), 13(b), and 13(c) are the TEM morphology diagrams of the SWCNT@ZnIn2S4 nanocomposites prepared in Example 2, Example 1, and Example 3, respectively. The left figure is at low magnification and the right one is at high magnification. It can be seen that in the SWCNT@ZnIn2S4 nanocomposites with different SWCN addition amounts, the 3D ZnIn2S4 nanostructures grow in-situ along the tube walls of the 1D SWCNTs, forming 1D / 3D nanocomposites. The ZnIn2S4 nanocomposite structures are uniformly dispersed and have a large specific surface area, which is conducive to fully reacting with the solution, can increase the active sites of photocatalysis. There is an obvious interface between the SWCNT and ZnIn2S4 materials, and the composite interface forms an efficient heterojunction structure, which is beneficial to improving the separation of photo-generated carriers.

[0041] Figure 6 Figure 17 shows the EDS mapping diagrams of the overall SWCNT@ZnIn2S4 nanocomposite prepared in Example 1, and the carbon, zinc, indium, and sulfur elements in the SWCNT@ZnIn2S4 nanocomposite from left to right. It can be clearly seen that the 3D ZnIn2S4 nanostructures grow in-situ along the surface of the 1D SWCNTs.

[0042] Figure 7 It can be seen from the Raman spectrum of that the Raman vibration mode of the carboxyl group in SWCNT@ZnIn2S4 has disappeared, and we believe that the carboxyl group has fallen off during the formation of the heterojunction.

[0043] Take the SWCNT@ZnIn2S4 nanocomposite prepared in Example 1 and the pure ZnIn2S4 prepared in Comparative Example 1, and test their optoelectronic response performance. The test conditions are as follows: a three-electrode electrochemical test system, with Pt as the counter electrode and Ag / AgCl as the reference electrode. After ultrasonically mixing 5 mg of the SWCNT@ZnIn2S4 nanocomposite, 1.6 mL of deionized water, 0.8 mL of ethanol, and 25 μL of Nafion, it is coated on ITO glass as the working electrode. The light source is a xenon lamp source. The test results are as Figure 8 shown. Figure 8 As can be seen from Figure 8 Figure 8 , the photocurrent response of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite is higher than that of the pure ZnIn2S4 nanomaterial, up to 43 times, which means that the SWCNT@ZnIn2S4 nanocomposite obtained in the present invention effectively improves the separation of photo-generated carriers.

[0044] Take the SWCNT@ZnIn2S4 nanocomposites prepared in Examples 1 to 3 and the pure ZnIn2S4 prepared in Comparative Example 1, and test their catalytic performance. The test conditions are as follows: Put 30 mg of the photocatalyst into 100 mL of deionized water, add 10 mL of triethanolamine as the sacrificial agent, and then ultrasonically disperse for 30 minutes and place it on the photocatalytic hydrogen production device for testing. The incident light λ>420 nm. The test results are as Figure 9 shown. It can be seen that the photocatalytic hydrogen production rate of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite is increased to 2122 μmol·h -1 ·g -1 , and its catalytic performance is 3.5 times that of the pure ZnIn2S4 nanomaterial. When the SWCNT@ZnIn2S4 nanocomposite catalyzes, the hydrogen production performance and time are in a linear relationship, and as time increases, the amount of hydrogen produced increases linearly.

[0045] Figure 10 In Figure 8 Figure 8 is the stability cycle test chart of the 1D / 3D SWCNT@ZnIn2S4 nanocomposite prepared in Example 1. The data shows that the 1D / 3D nanocomposite has excellent cycle stability and can be reused.

[0046] The 1D / 3D SWCNT@ZnIn2S4 nanocomposite obtained in the present invention is in-situ grown on the surface of 1D SWCNT by the 3D ZnIn2S4 nanostructure, and there is coupling at the interface between the two materials. The addition of SWCNT also effectively inhibits the aggregation of the ZnIn2S4 nanostructure, improves the dispersibility and specific surface area, effectively increases the active sites of the composite material, and thus improves the photocatalytic hydrogen production performance.

Claims

1. A method for synthesizing a SWCNT@ZnIn2S4 nanocomposite material, characterized in that: The following steps are involved: (1) placing the SWCNT powder in a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1:2.8 to 3.2, ultrasonically treating for 8 to 10 hours, taking out the solid, washing it, and freeze-drying it to obtain a carboxylated SWCNT powder; (2) Dispersing the carboxylated SWCNT powder in a glycerol aqueous solution, adding zinc salt, indium salt and sulfur source, dissolving, heating to 75-85°C and maintaining for 1.5-2.5 hours, taking the precipitate, washing, and freeze-drying to obtain a SWCNT@ZnIn2S4 nanocomposite material; the molar ratio of the zinc salt, indium salt and sulfur source is 1:2:4-6; based on the theoretical mass of the final product ZnIn2S4, the addition ratio of the carboxylated SWCNT powder is 0.01-0.6%.

2. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 1, characterized in that: In step (2), the volume fraction of glycerol in the glycerol aqueous solution is 15 to 25%.

3. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 1, characterized in that: In step (1), the SWCNT powder is also pre-purified. The purification method is as follows: taking the SWCNT powder, putting it into a nitric acid solution with a mass fraction of 18-22%, stirring it at room temperature for 11-13 hours, taking the solid, washing it, and freeze-drying it to obtain the pre-purified SWCNT powder.

4. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 3, characterized in that: In step (1) and step (2), washing is performed with deionized water and ethanol.

5. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 1, characterized in that: In step (2), the carboxylated SWCNT powder is treated with ultrasound for 4 to 6 hours to disperse it in a glycerol aqueous solution.

6. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 1, characterized in that: In step (1), the zinc salt is ZnCl2, the indium salt is InCl3·4H2O, and the sulfur source is thioacetamide.

7. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 1, characterized in that: In step (1), the carboxylated SWCNT powder is added in an amount of 0.05 to 0.3% based on the theoretical mass of the final product ZnIn2S4.

8. The method for synthesizing the SWCNT@ZnIn2S4 nanocomposite material according to claim 4, characterized in that: In step (1) and step (2), the power used in ultrasonic treatment is 500 kW to 1000 kW.

9. A photocatalyst, characterized in that Including SWCNT@ZnIn2S4 nanocomposite material synthesized by the aforementioned synthesis method.

10. The photocatalyst according to claim 9, characterized in that In the SWCNT@ZnIn2S4 nanocomposite, ZnIn2S4 nanostructures grow in situ along the tube wall of SWCNT.

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