A ZnIn2S4-based Z-type crystalline heterojunction photocatalyst, its preparation method and application

Abstract

The application discloses a ZnIn2S4-based Z-type crystal heterojunction photocatalyst and a preparation method and application thereof. The Z-type crystal heterojunction photocatalyst with ZnIn2S4 loaded and embedded in NaTi3O6(OH) 2H2O is constructed by using a step-by-step solvothermal method. The application does not need to use a template agent, a surfactant and a complicated heterojunction step-by-step construction. The obtained photocatalyst not only improves the separation efficiency of carriers, but also significantly inhibits the agglomeration of a single photocatalyst, and exhibits excellent photocatalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, and particularly relates to a ZnIn2S4-based Z-type crystal heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] Currently, the rapid development of human society relies excessively on non-renewable traditional energy sources (coal, oil, and natural gas, etc.). The massive consumption of traditional energy sources has led to serious environmental and energy problems, and photocatalysis technology can fundamentally alleviate these issues.

[0003] In 1972, Fujishima and Honda discovered that TiO2 could split water into hydrogen under photoexcitation. Therefore, photocatalytic water splitting for hydrogen production has attracted widespread attention from researchers. In recent years, different types of semiconductor photocatalysts (metal oxides, metal sulfides, etc.) have been widely used in photocatalytic water splitting for hydrogen production and pollutant degradation research. For metal oxides, most only respond in the ultraviolet range, resulting in low utilization of sunlight, and are rarely used directly as photocatalytic semiconductor materials. Compared to metal oxides, metal sulfides (ZnIn2S4) have strong photogenerated electrons with high reduction ability and visible light response, making them candidate materials for photocatalytic hydrogen production. However, severe recombination of photogenerated carriers directly limits the application of this catalyst. Therefore, most researchers focus on constructing heterojunctions to improve the separation efficiency of photogenerated carriers, but bulk photogenerated carriers cannot be fully separated. This patent is the first to propose the concept of crystalline heterojunction photocatalysts. Guided by theory, it rationally designs the optimal ZnIn2S4-based Z-type crystalline heterojunction photocatalyst to achieve efficient bulk phase separation of photogenerated carriers for photocatalytic hydrogen evolution and pollutant degradation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a ZnIn2S4-based Z-type crystal heterojunction photocatalyst.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a ZnIn2S4-based Z-type crystalline heterojunction photocatalyst includes the following steps: S1. Add 0.1-4.0 g of anatase TiO2 to 75 mL of 10M NaOH solution, stir for 1-12 h, then transfer to a 100 mL polytetrafluoroethylene reactor and keep warm at 160-200℃ for 48 h. Filter with water until the pH is neutral, and dry under vacuum at 60℃ to obtain NaTi3O6(OH)·2H2O, denoted as: HNTO; S2. Different percentages of NaTi3O6(OH)·2H2O (10%, 20%, 40%, and 60%) were added to ethylene glycol solvent and ultrasonically stirred for 20 min. Then, ZnCl2, InCl3·4H2O, and thioacetamide were added sequentially, stirred for 30 min, and transferred to a polytetrafluoroethylene reactor. The mixture was kept at 60-200℃ for 1-12 h, washed 3-5 times with anhydrous ethanol, and vacuum dried at 60℃ to obtain the X HNTO / ZnIn2S4 (ZIS) crystalline heterojunction photocatalyst, where X represents the theoretical molar mass percentage of HNTO in ZIS.

[0006] Furthermore, in step S2, the volume of ethylene glycol is 10-60 mL, the molar ratio of ZnCl2, InCl3·4H2O and thioacetamide is 1:2:4, and the molar ratio of NaTi3O6(OH)·2H2O to ZnCl2 is 42.3~253.8:1.

[0007] Another object of the present invention is to provide an XHNTO / ZIS crystalline heterojunction photocatalyst prepared by the above preparation method.

[0008] Another object of the present invention is to provide an application of an XHNTO / ZIS crystalline heterojunction photocatalyst in photocatalytic water splitting for hydrogen production and pollutant degradation.

[0009] Mechanism: This invention prepares NaTi3O6(OH)·2H2O (HNTO) photocatalyst via a one-step hydrothermal method. Guided by ion exchange theory, ZnIn2S4 (ZIS) is further supported and embedded in the interlayer of HNTO using a solvothermal method to obtain a Z-shaped crystalline heterojunction of HNTO / ZIS. Secondly, studies show that the work functions of HNTO and ZIS are not significantly different, and the charge transport mechanism of the Z-shaped heterojunction is achieved through the close contact between their crystalline heterojunction interfaces. Finally, the construction of the Z-shaped crystalline heterojunction achieves phase separation of photogenerated carriers while retaining strong reducing and oxidizing capabilities. Simultaneously, the introduction of HNTO into the heterojunction and the aggregation of ZIS expose more active sites, enhancing photocatalytic activity. This invention provides a simple method for preparing the Z-shaped crystalline heterojunction photocatalyst of HNTO / ZIS, with abundant raw material sources and excellent photocatalytic performance, demonstrating significant economic and social benefits.

[0010] The advantages of this invention are: 1. This invention enables the preparation of a ZIS-supported crystalline heterojunction photocatalyst embedded in the interlayer of HNTO without the use of template agents or surfactants. This catalyst exhibits a photocatalytic hydrogen evolution rate of up to 15.0 mmol / h / g under photoexcitation, which is 33.3 times that of HNTO and 1.6 times that of ZIS. This is mainly attributed to the efficient transfer and separation of charges within the crystal (bulk phase) of the composite material, while the close contact further promotes the separation of surface charges, effectively enhancing the photocatalytic hydrogen production activity. Experiments using sodium lignosulfonate (SLS) as a pollutant (100 ppm) under a 10 W LED lamp showed a degradation efficiency of 73.3% within 120 min, with the COD value decreasing from an initial 109.5 mg / mL to 33.3 mg / mL. Compared to the degradation capacity of ZIS, the composite material shows a significantly increased degradation rate, which can be attributed to the close contact between the crystalline heterojunctions, altering the charge transport pathway and separation. The Z-type heterojunction charge transport mechanism retains both strong reducing and oxidizing capabilities. 2. This invention is the first to prepare a ZIS-supported and HNTO-embedded interlayer crystalline heterojunction photocatalyst. The preparation conditions of this catalyst are mild, the equipment requirements are low, no surfactants or templates are required, no precious metals are used, the atom utilization rate is high and the raw material cost is low, which is conducive to the realization of industrial production. 3. The catalyst prepared by this invention is a composite of one-dimensional and two-dimensional materials, which is more conducive to the directional transport and migration of photogenerated carriers, increases the specific surface area of ​​the catalyst, and exposes more active sites. 4. This invention, through component regulation, ZIS loading and embedding in the HNTO interlayer, results in close interfacial contact, promotes the separation of bulk photogenerated carriers and retains strong reducing and oxidizing capabilities, thereby increasing the photocatalytic activity of the catalyst; 5. The introduction of HNTO in this invention can effectively inhibit the aggregation of ZIS itself and provide more active sites; 6. Through reasonable theoretical design, the resulting ZIS-supported crystalline heterojunction photocatalyst embedded in HNTO layers exhibits excellent photocatalytic hydrogen evolution performance and activity in degrading sodium lignosulfonate. Attached Figure Description

[0011] Figure 1 Figure 1 shows the mechanism relationship of the composite material prepared by the method of the present invention; Figure 2a is a schematic diagram of the composite material preparation; Figure 3b is the XRD pattern of different comparative samples; Figure 4cf is the high-resolution XPS pattern of the corresponding elements of the comparative samples; and Figure 5g1 is the SEM image of different catalysts.

[0012] Figure 2Figure 1 shows the crystal structure and specific surface area characterization of different photocatalysts in this invention; Figure 2a is the XRD pattern, Figure 3b is the FTIR pattern, Figure 4c is the BET pattern, and Figure 5d is the pore size distribution.

[0013] Figure 3 These are microstructure characterization diagrams of the photocatalyst in this invention; wherein Figure a is a TEM image of HNTO, Figure b is a TEM image of ZIS, Figure cd are SEM images of the photocatalyst at different magnifications, Figure e is a TEM image of 20HNTO / ZIS, Figure fg is a HRTEM image of 20HNTO / ZIS, Figure h is a dark-field TEM image, and Figures h1-h5 are the corresponding elemental mapping diagrams.

[0014] Figure 4 Figure 1 shows the relationship between photocatalytic hydrogen evolution performance evaluation; Figure 2a is the change of photocatalytic hydrogen evolution amount over time, Figure 3b is the hydrogen evolution rate corresponding to different catalysts, Figure 4c is the hydrogen evolution rate of different comparison samples, and Figure 5d is the quantum efficiency of 20HNTO / ZIS.

[0015] Figure 5 Figure 1 shows the relationship between photocatalytic degradation performance evaluation. Figure 2a is the photocatalytic degradation activity diagram, Figure 3b is the degradation rate constant diagram corresponding to pseudo-first-order kinetics, Figure 4c is the free radical capture experiment diagram, and Figure 5d is the relationship between COD and TOC values ​​of LS degradation by 20HNTO / ZIS. Detailed Implementation

[0016] Example 1 A method for preparing a ZnIn2S4-based Z-type crystalline heterojunction photocatalyst includes the following steps: (1) Add 0.1-4.0 g of anatase TiO2 to 75 mL of 10 M NaOH solution, stir for 1-12 h, transfer to 100 mL of polytetrafluoroethylene reactor, keep warm at 160-200℃ for 48 h, filter with water until pH is neutral, and vacuum dry at 60℃ to obtain NaTi3O6(OH)·2H2O(HNTO).

[0017] (2) 42.3 mg of HNTO was added to 20 mL of EG solvent and sonicated for 10 min. Then, 1 mmol ZnCl2, 2 mmol InCl3·4H2O and 4 mmol TAA were added in sequence, stirred for 30 min and transferred to a 50 mL polytetrafluoroethylene reactor and kept at 120 °C for 2 h. The mixture was washed three times with anhydrous ethanol and dried under vacuum at 60 °C to obtain ZIS loaded with HNTO, named 10HNTO / ZIS.

[0018] Another object of the present invention is to provide an HNTO / ZIS crystalline heterojunction photocatalyst prepared by the above preparation method.

[0019] Another object of the present invention is to provide an application of an HNTO / ZIS crystalline heterojunction photocatalyst in photocatalytic water splitting for hydrogen production and pollutant degradation.

[0020] Example 2 The difference between Example 2 and Example 1 is as follows: 84.6 mg of HNTO was added to 20 mL of EG solvent and sonicated for 10 min. Then, 1 mmol of ZnCl2, 2 mmol of InCl3·4H2O and 4 mmol of TAA were added sequentially, stirred for 30 min and transferred to a 50 mL polytetrafluoroethylene reactor. The mixture was kept at 120 °C for 2 h, washed three times with anhydrous ethanol, and vacuum dried at 60 °C to obtain ZIS loaded with HNTO, named 20HNTO / ZIS.

[0021] Example 3 The difference between Example 3 and Example 1 is as follows: 169.2 mg of HNTO was added to 20 mL of EG solvent and sonicated for 10 min. Then, 1 mmol ZnCl2, 2 mmol InCl3·4H2O and 4 mmol TAA were added sequentially, stirred for 30 min and transferred to a 50 mL polytetrafluoroethylene reactor. The mixture was kept at 120 °C for 2 h, washed three times with anhydrous ethanol, and vacuum dried at 60 °C to obtain ZIS loaded with HNTO, named 40HNTO / ZIS.

[0022] Example 4 The difference between Example 4 and Example 1 is as follows: 253.8 mg of HNTO was added to 20 mL of EG solvent and sonicated for 10 min. Then, 1 mmol ZnCl2, 2 mmol InCl3·4H2O and 4 mmol TAA were added sequentially, stirred for 30 min and transferred to a 50 mL polytetrafluoroethylene reactor. The mixture was kept at 120 °C for 2 h, washed three times with anhydrous ethanol, and vacuum dried at 60 °C to obtain ZIS loaded with HNTO, named 60HNTO / ZIS.

[0023] Performance testing Test conditions: Photocatalytic hydrogen production test: using triethanolamine as a sacrificial agent: 10 mg of catalyst + 100 mL of triethanolamine aqueous solution (10 ml triethanolamine + 90 ml water), excited under a 300 W xenon lamp.

[0024] Pollutant degradation test: Sodium lignosulfonate as pollutant: 30 mg catalyst + 30 mL of 100 ppm sodium lignosulfonate aqueous solution, under a 10 W LED lamp.

[0025] Test results: The catalyst can achieve a photocatalytic hydrogen evolution rate of up to 15.0 mmol / h / g under photoexcitation. Using sodium lignosulfonate (SLS) as the pollutant (100 ppm), under a 10 W LED lamp, its degradation efficiency reached 73.3% in 120 min, and the COD value decreased from the initial 109.5 mg / mL to 33.3 mg / mL.

[0026] Attached Figure Analysis: Figure 1 A detailed investigation was conducted into the mechanism of the composite material prepared in this invention. Using XPS, XRD, and SEM, it was concluded that the introduction of HNTO and Zn into the ZIS preparation system... 2+ and In 3+ First, replace Na. + Furthermore, ZIS is embedded into the HNTO lattice through sulfidation to form HNTO-Zn&In-TAA. In the final reaction process, excess ZIS is further loaded onto the HNTO-Zn&In-TAA structure to form an HNTO / ZIS heterojunction photocatalyst. In addition, Figure 2 The crystal structure and specific surface area of ​​the photocatalyst in this invention were characterized, confirming that the invention successfully prepared composite materials of ZIS, HNTO, and HNTO / ZIS, and the specific surface area of ​​the composite materials was significantly increased. Figure 3 The microstructure of the photocatalyst was further investigated using SEM and TEM. Figure 3 Figures a and b show that the ZIS and HNTO prepared in this invention exhibit micron-like flower structures and nanowire structures, respectively. Figure 3 As can be seen from the ch, the introduction of HNTO significantly inhibited the aggregation of ZIS, exhibiting a "bird's nest" structure; at the same time, the interface between the HNTO and ZIS heterojunction is not very obvious, indicating the concept of this heterojunction composite crystal heterojunction. Figure 4 This is a test graph showing the photocatalytic hydrogen evolution performance of the catalyst in this invention. The composite material exhibits excellent hydrogen evolution activity (15.0 mmol / h / g) and a maximum apparent quantum efficiency of 25.2%. Compared with other photocatalysts, the photocatalytic hydrogen evolution activity of the crystalline heterojunction photocatalyst formed by introducing ZIS into the HNTO interlayer is significantly improved. Figure 5 The photocatalytic activity of the photocatalyst for the degradation of sodium lignosulfonate was presented. Under a 10 W LED lamp, the degradation efficiency reached 73.3% in 120 min. Within 120 min, the COD and TOC values ​​of 20HNTO / ZIS for sodium lignosulfonate decreased from the initial 109.5 mg / L and 41.1 mg / L to 33.3 mg / L and 21.1 mg / L, respectively.

Claims

1. A method for preparing a ZnIn2S4-based Z-type crystalline heterojunction photocatalyst, characterized in that, Includes the following steps: S1. Add 0.1-4.0 g of anatase TiO2 to 75 mL of 10M NaOH solution, stir for 1-12 h, then transfer to 100 mL of polytetrafluoroethylene reactor and keep warm at 160-200℃ for 48 h. Filter with water until the pH is neutral, and dry under vacuum at 60℃ to obtain NaTi3O6(OH)·2H2O. S2. Add NaTi3O6(OH)·2H2O to ethylene glycol solvent, sonicate and stir for 20 min, then add ZnCl2, InCl3·4H2O and thioacetamide in sequence, stir for 30 min and transfer to polytetrafluoroethylene reactor and keep at 60-200℃ for 1-12 h, wash with anhydrous ethanol 3-5 times, and vacuum dry at 60℃ to obtain HNTO / ZIS crystalline heterojunction photocatalyst.

2. The preparation method of the ZnIn2S4-based Z-type crystal heterojunction photocatalyst as described in claim 1, characterized in that: In step S2, the volume of ethylene glycol is 10-60 mL, the molar ratio of ZnCl2, InCl3·4H2O and thioacetamide is 1:2:4, and the molar ratio of NaTi3O6(OH)·2H2O to ZnCl2 is 42.3~253.8:

1.

3. The HNTO / ZIS crystalline heterojunction photocatalyst prepared by the preparation method according to claim 1 or 2.

4. The application of the HNTO / ZIS crystalline heterojunction photocatalyst prepared according to claim 3 in photocatalytic water splitting for hydrogen production and pollutant degradation.

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