A tubular ZnIn2S4 photocatalyst and its preparation method

Abstract

The application belongs to the technical field of nanometer material preparation, and discloses a tubular ZnIn2S4 photocatalyst and a preparation method thereof. Zinc chloride, indium chloride and a hydrazine hydrate solution are mixed, and then thiourea is added to obtain a reaction precursor solution, and a hydrothermal reaction is performed to obtain the tubular ZnIn2S4 photocatalyst. The preparation method has a simple process flow, is convenient to operate, and has relatively mild reaction conditions. The method does not need complex and expensive instrument equipment, and does not need to introduce an additional template agent or a surfactant, reduces the difficulty of subsequent impurity removal, and is beneficial to maintaining the purity and structural stability of the product composition.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a tubular ZnIn2S4 photocatalyst and its preparation method. Background Technology

[0002] ZnIn2S4 is a ternary chalcogenide compound with a layered structure. Due to its suitable band gap (approximately 2.4–2.8 eV), good visible light response characteristics, and excellent photocatalytic performance, it shows broad application prospects in photocatalytic water splitting for hydrogen production, photocatalytic degradation of organic pollutants, and photoelectrochemical cells. ZnIn2S4 has a typical layered spinel structure with weak interlayer interactions. By controlling the synthesis conditions, various morphologies such as nanosheets, nanoflowers, and nanospheres can be obtained.

[0003] Among various morphologies, tubular structures, due to their unique hollow shape, possess advantages such as large specific surface area, numerous active sites, and short photogenerated carrier transport paths, and are considered one of the most promising photocatalytic material morphologies. However, current methods for preparing tubular ZnIn2S4 mainly suffer from the following problems: (1) Template method: Traditional tubular structure preparation often relies on hard templates (such as anodic alumina templates AAO, mesoporous silica, etc.) or soft templates (such as surfactants CTAB, P123, etc.). The hard template method requires the template to be removed by etching with strong acid or strong base after synthesis, which is a complex process and introduces secondary pollution; the soft template method has problems such as incomplete template removal and residual organic matter affecting material properties. In addition, the use of template agents significantly increases production costs and is not conducive to industrial application.

[0004] (2) Solvent problem: In existing hydrothermal / solventothermal synthesis methods of ZnIn2S4, commonly used organic solvents (such as ethylene glycol, N,N-dimethylformamide, ethanolamine, etc.) are not only expensive, but also difficult to recycle after the reaction, resulting in resource waste and environmental pollution. Some methods use water as a solvent, which is environmentally friendly, but it is difficult to effectively control the morphology of the product.

[0005] (3) Difficulty in morphology control: Obtaining tubular morphology directly through a simple hydrothermal method without using a template is still quite challenging. Most template-free methods yield morphologies such as nanosheets, nanoflowers, or nanospheres, making it difficult to achieve precise control of the tubular structure.

[0006] Therefore, developing a template-free, solvent-recyclable, simple, and efficient method for synthesizing tubular ZnIn2S4 is of great significance for promoting the practical application of ZnIn2S4 photocatalytic materials. Summary of the Invention

[0007] The purpose of this invention is to provide a tubular ZnIn2S4 photocatalyst and its preparation method, thereby solving the aforementioned problems existing in the prior art.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a tubular ZnIn2S4 photocatalyst, comprising the following steps: A solution of zinc chloride, indium chloride, and hydrazine hydrate was mixed, and then thiourea was added to obtain a reaction precursor solution. The precursor solution was placed in a polytetrafluoroethylene-lined reactor for hydrothermal reaction. The reaction product was washed and freeze-dried to obtain a tubular ZnIn2S4 photocatalyst.

[0009] Preferably, the hydrazine hydrate solution has a mass fraction of 80%.

[0010] Preferably, the ratio of zinc chloride, indium chloride, thiourea, and hydrazine hydrate solution is 1~1.5 mmol:2~3 mmol:7~9 mmol:40~50 mL.

[0011] Preferably, the mixing time of the zinc chloride, indium chloride, and hydrazine hydrate solution is 20-50 min.

[0012] Preferably, the addition of thiourea is followed by stirring; the stirring time is 2-3 hours.

[0013] Preferably, the temperature of the hydrothermal reaction is 170~190 ℃; and the time of the hydrothermal reaction is 36~48 h.

[0014] Preferably, the freeze-drying time is 12-24 h.

[0015] The present invention also provides a tubular ZnIn2S4 photocatalyst prepared by the above preparation method.

[0016] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: The preparation method of this invention has a simple process flow, is easy to operate, has relatively mild reaction conditions, does not require complex and expensive instruments and equipment, and does not require the introduction of additional template agents or surfactants. This is because hydrazine hydrate (N2H4·H2O) plays multiple key roles in the hydrothermal / solventothermal reaction system: as a strongly polar solvent, it can effectively dissolve and complex the metal precursor (Zn). 2+ In 3+Furthermore, its strongly alkaline environment promotes the slow hydrolysis of the sulfur source (thiourea), achieving a continuous and controllable release of sulfur ions and preferentially generating a layered ZnIn2S4 precursor with N2H4 intercalation. Subsequently, this layered precursor spontaneously folds and curls due to surface energy anisotropy, forming a hollow tubular prototype. As the reaction progresses, the intercalated hydrazine hydrate is gradually removed at high temperature, and the precursor obtains a crystalline tube wall through a solid-solid phase transition. Simultaneously, the high concentration of hydrazine hydrate dissolves the tiny crystals and deposits them on the surface of the tubular structure, ultimately yielding ZnIn2S4 nanotubes with uniform wall thickness. This invention utilizes hydrazine hydrate to simultaneously act as a solvent, complexing agent, and in-situ intercalation soft template, leaving no residue after intercalation and deintercalation. Therefore, precise control of the tubular morphology can be achieved without the need for additional hard template agents, reducing the difficulty of subsequent impurity removal and helping to maintain the purity and structural stability of the product composition. The raw materials used, such as zinc chloride, indium chloride, and thiourea, are widely available and relatively inexpensive. The experimental process is highly controllable and reproducible, making it suitable for laboratory preparation and further scale-up research. Compared with traditional irregular granular or sheet-like ZnIn2S4 materials, the tubular ZnIn2S4 obtained in this invention has a unique spatial structure and a larger exposed surface area, which increases the contact area between the material and the external reaction system and facilitates light absorption, interfacial mass transfer, and the migration and separation of photogenerated charges, thereby improving the overall photocatalytic performance of the material. This tubular structure can also, to some extent, improve the problems of easy aggregation and insufficient utilization of effective active sites in ZnIn2S4 materials, providing a simple, economical, and green preparation approach for morphology control and performance optimization of ZnIn2S4-based photocatalytic materials. The method of this invention has the advantages of readily available raw materials, low cost, simple steps, controllable morphology, and good application prospects. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a flowchart illustrating the preparation process of the tubular ZnIn2S4 photocatalyst of the present invention. Figure 2 SEM image of the tubular ZnIn2S4 photocatalyst of Example 1; Figure 3 This is a TEM image of the tubular ZnIn2S4 photocatalyst from Example 1. Figure 4 The diagram shows the dechlorination performance of Application Example 1. Detailed Implementation

[0019] This invention provides a method for preparing tubular ZnIn2S4 photocatalysts, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps: A solution of zinc chloride, indium chloride, and hydrazine hydrate was mixed, and then thiourea was added to obtain a reaction precursor solution. The precursor solution was placed in a polytetrafluoroethylene-lined reactor for hydrothermal reaction. The reaction product was washed and freeze-dried to obtain a tubular ZnIn2S4 photocatalyst.

[0020] In this invention, the mass fraction of the hydrazine hydrate solution is preferably 80%.

[0021] In this invention, the preferred ratio of the zinc chloride, indium chloride, thiourea, and hydrazine hydrate solution is 1~1.5 mmol:2~3 mmol:7~9 mmol:40~50 mL, and more preferably 1~1.2 mmol:2~2.4 mmol:7.5~8.5 mmol:40~45 mL.

[0022] In this invention, the mixing time of the zinc chloride, indium chloride, and hydrazine hydrate solution is preferably 20-50 min, and more preferably 30-40 min.

[0023] In this invention, the addition of thiourea is followed by stirring; the stirring time is preferably 2-3 h, more preferably 2-2.5 h.

[0024] In this invention, the temperature of the hydrothermal reaction is preferably 170~190 ℃, more preferably 175~185 ℃; the time of the hydrothermal reaction is preferably 36~48 h, more preferably 40~44 h.

[0025] In this invention, the washing is preferably performed by sequentially washing with anhydrous ethanol and water; the number of times the anhydrous ethanol is washed is preferably 2 to 3 times, more preferably 3 times; the number of times the water is washed is preferably 2 to 3 times, more preferably 3 times.

[0026] In this invention, the freeze-drying time is preferably 12-24 h, and more preferably 16-24 h.

[0027] The present invention also provides a tubular ZnIn2S4 photocatalyst prepared by the above preparation method.

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] The preparation method of tubular ZnIn2S4 photocatalyst includes the following steps: (1) Measure 40 mL of hydrazine hydrate solution (mass fraction 80%), place it in a beaker and stir thoroughly to form a homogeneous reaction medium; (2) Weigh 1 mmol zinc chloride (ZnCl2) and 2 mmol indium chloride (InCl3) and add them to the above hydrazine hydrate solution. Stir continuously for 30 min to fully dissolve and uniformly disperse the zinc and indium sources. (3) Weigh 8 mmol of thiourea (CH4N2S) and add it to the above mixed solution. Continue stirring for 2 h to fully mix the sulfur source and metal ions to obtain a homogeneous reaction precursor solution. (4) Transfer the reaction precursor liquid to a 100 mL polytetrafluoroethylene-lined reactor, seal it, and place it in an oven for hydrothermal reaction at 180 °C for 42 h. After the reaction is completed, allow it to cool naturally to room temperature. (5) The precipitate was collected by centrifugation and washed with anhydrous ethanol and deionized water in sequence, three times with anhydrous ethanol and three times with deionized water, to remove unreacted impurities and residual ions. (6) The washed precipitate was freeze-dried for 24 h. After drying, it was ground to obtain the tubular ZnIn2S4 photocatalyst.

[0031] SEM and TEM images of the tubular ZnIn2S4 photocatalyst are shown below. Figure 2 and Figure 3 As shown in the figure, this invention successfully synthesized tubular nanostructures with distinct hollow features. SEM images reveal that the sample consists of numerous interlaced nanoribbons forming a three-dimensional network structure; high-magnification observation shows that these ribbons have rough edges, exhibiting a hollow visual characteristic. TEM images further confirm its tubular configuration, clearly showing parallel-arranged nanotubes and their thin-walled structure, with a tube diameter of approximately 30–50 nm.

[0032] Application Example 1

[0033] To further investigate the actual efficiency of the tubular ZnIn2S4 photocatalyst in the degradation of organic pollutants in Example 1, chlorobenzene, a typical recalcitrant organochloride, was used as a model pollutant to evaluate the photocatalytic dechlorination activity of the prepared tubular ZnIn2S4. The test conditions were as follows: 100 mL of an initial 0.4 mM chlorobenzene aqueous solution and 20 mg of tubular ZnIn2S4 photocatalyst were added to a closed reactor, and the mixture was magnetically stirred in the dark for 30 min to achieve sufficient adsorption equilibrium of the pollutant on the photocatalyst surface. Subsequently, a 300 W Xe lamp (λ≥420 nm) was turned on for visible light irradiation. During the reaction, samples were taken periodically, and the concentration of chloride ions released in the solution was detected by ion chromatography to determine the degree of dechlorination. Its dechlorination performance is as follows: Figure 4 As shown. By Figure 4 As can be seen from the figure, the dechlorination rate gradually increases with time. The photocatalytic dechlorination reaction of the prepared tubular ZnIn2S4 to chlorobenzene exhibits typical "fast-slow" kinetic characteristics: the dechlorination rate rapidly climbs to about 0.30 (30%) within the first 2 hours of the reaction, indicating that there are sufficient active sites on the catalyst surface and the substrate concentration is high; thereafter the slope of the curve gradually slows down, and the dechlorination rate reaches about 0.43 (43%) after 8 hours.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a tubular ZnIn2S4 photocatalyst, characterized in that, Includes the following steps: A solution of zinc chloride, indium chloride, and hydrazine hydrate was mixed, and then thiourea was added to obtain a reaction precursor solution. The precursor solution was placed in a polytetrafluoroethylene-lined reactor for hydrothermal reaction. The reaction product was washed and freeze-dried to obtain a tubular ZnIn2S4 photocatalyst.

2. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The hydrazine hydrate solution has a mass fraction of 80%.

3. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The ratio of zinc chloride, indium chloride, thiourea, and hydrazine hydrate solution is 1~1.5 mmol: 2~3 mmol: 7~9 mmol: 40~50 mL.

4. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The mixing time for the zinc chloride, indium chloride, and hydrazine hydrate solutions is 20-50 min.

5. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The addition of thiourea is followed by stirring; the stirring time is 2-3 hours.

6. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The hydrothermal reaction temperature is 170~190 ℃; the hydrothermal reaction time is 36~48 h.

7. The method for preparing a tubular ZnIn2S4 photocatalyst according to claim 1, characterized in that, The freeze-drying time is 12-24 hours.

8. A tubular ZnIn2S4 photocatalyst prepared by the preparation method according to any one of claims 1 to 7.

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