A ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials, their preparation methods and applications

Abstract

The application discloses a kind of ZnIn2S4 / H + Ti2NbO7 ‑ Photocatalytic composite material and its preparation method and application.Cs2CO3, Nb2O5 and TiO2 are weighed, and CsTi2NbO7 powder is prepared by calcination, the powder is washed by acid and H + After stacking, H + Ti2NbO7 ‑ Nanosheet, finally with ZnCl2, InCl3.4H2O and TAA by hydrothermal method to prepare photocatalytic composite material.The preparation method of the application has low cost, high efficiency and environmental friendliness, and the obtained H + Ti2NbO7 ‑ The composite ZnIn2S4 material has a composite heterojunction structure and a unique 3D-2D core-shell structure.The unique 3D-2D structure gives the heterojunction a large interface area, increases the specific surface area, and the ultrathin nanosheet structure can effectively increase the reactive sites, thereby improving the hydrogen production rate.

Description

Technical Field

[0001] This invention belongs to the field of material preparation and renewable clean energy utilization technology, specifically relating to a ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials, their preparation methods, and applications. Background Technology

[0002] The ever-increasing energy demand and the environmental hazards of fossil fuel combustion have made the search for renewable energy sources urgent. Hydrogen, with its zero emissions and high energy content, is considered a major alternative to fossil fuels. Among the various methods for H2 conversion, using sunlight to drive photocatalytic water splitting to produce H2 has attracted considerable interest as a strategy that can solve both environmental and energy problems.

[0003] In theory, all photocatalytic reactions are driven by charge carriers, whose behavior can be categorized into charge generation, separation, migration, and surface reactions. The efficiency of charge utilization in each step determines the overall performance of the photocatalysis. The heterojunction structure of composite photocatalysts with tight interfaces and sufficient contact area is key to achieving excellent photogenerated carrier migration efficiency. However, most composite materials lack sufficient contact area due to their morphology, resulting in low photogenerated carrier migration efficiency.

[0004] Indium zinc sulfide (ZnIn2S4) has become a hot topic among photocatalytic material researchers due to its suitable band gap, safety and non-toxicity, physicochemical stability, and good durability. The ternary sulfide ZnIn2S4 belongs to the n-type layered semiconductor structure with a band gap between 2.06 and 2.85 eV, exhibiting a suitable semiconductor band gap structure and demonstrating good photocatalytic activity in the visible light region. However, sulfides face some typical challenges, such as low separation and migration efficiency of photogenerated carriers (electron-hole pairs) and their easy recombination, which hinder the improvement of their photocatalytic performance. Furthermore, single sulfide catalysts prepared by conventional methods have a low specific surface area, resulting in fewer active sites for photocatalytic reactions and lower visible light utilization, ultimately leading to low visible light utilization. To obtain better photocatalytic performance, it is necessary to increase the number of effective active sites, broaden the spectral response range, and improve the separation and migration efficiency of photogenerated carriers. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials, their preparation methods and applications, including ZnIn2S4 / H + Ti2NbO7 -Photocatalytic composite materials have a unique 3D-2D core-shell structure, and their preparation methods are simple, low-cost, efficient, environmentally friendly, safe and convenient, showing good application prospects.

[0006] To address the problems in the existing technology, the present invention adopts the following technical solution:

[0007] A ZnIn2S4 / H + Ti2NbO7 - The preparation method of photocatalytic composite material includes the following steps:

[0008] Step 1: Mix Cs2CO3, Nb2O5 and TiO2 in a certain proportion, grind them carefully in a dry environment, heat to 750℃, 950℃ and 1050℃ and keep for 12 hours each to obtain CsTi2NbO7 powder;

[0009] Step 2: CsTi₂NbO₇ was added to an aqueous nitric acid solution and stirred at 60 °C for 72 hours, with the acid solution replaced every 24 hours. 1.0 g of HTi₂NbO₇ was then distributed into distilled water, followed by the addition of tetrabutylammonium hydroxide (TBAOH) solution until the pH reached 9.5-10. After continuous stirring for 7 days, the supernatant was collected by high-speed centrifugation to obtain HTi₂NbO₇ nanosheets. Then, an aqueous HNO₃ solution was added to the HTi₂NbO₇ nanosheets, causing HNO₃ to... + Re-stacking H + Ti2NbO7 - The nanosheets were immediately aggregated (denoted as HTN), and the precipitate HTN was dried in a petri dish and collected.

[0010] Step 3: Weigh out HTN and place it in deionized water. Stir vigorously until homogeneous. Then, add ZnCl2, InCl3·4H2O, and TAA one by one to the above stirred liquid phase. Continue stirring for 30 minutes. Then, place it in a 100 ml reactor and hydrothermally react in an oven at 160 °C for 16 hours. After naturally cooling to room temperature, collect the product, wash it with deionized water, dry it, and collect it to obtain ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials.

[0011] Preferably, the molar ratio of Cs2CO3, Nb2O5 and TiO2 in step 1 is 1.12:1:4.

[0012] Preferably, the heating rate in step 1 is 5-10 ℃ / min.

[0013] Preferably, the centrifugation speed in step 2 is 4000 r / min.

[0014] Preferably, the drying temperature in step 2 is 70 °C.

[0015] Preferably, the hydrothermal reaction in step 3 is carried out at a temperature of 160 °C for 16 h.

[0016] Preferably, the drying temperature in step 3 is 60 ℃ and the drying time is 12 h.

[0017] The above ZnIn2S4 / H + Ti2NbO7 - A method for preparing photocatalytic composite materials, characterized in that the ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials have a 3D / 2D core-shell structure.

[0018] ZnIn2S4 / H prepared by the above method + Ti2NbO7 - Application of photocatalytic composite materials in photocatalytic water splitting for hydrogen production.

[0019] HTN and ZIS nanosheets form a 2D / 3D heterojunction. HTN cannot be excited by visible light irradiation, while ZIS generates photogenerated electrons and holes. Based on a type II migration mechanism, the close chemical contact between HTN and ZIS provides an efficient channel for promoting photogenerated charge migration. Due to the inward electric field created by the potential difference, photogenerated electrons in the CB (-0.8 V) of ZIS migrate to the CB (-0.64 V) of HTN, and then react with H₂O / H₂O. + The reaction produces H2. Simultaneously, the holes generated by ZIS photoexcitation remain in their original valence band. The heterojunction effect effectively suppresses electron-hole recombination in ZnIn2S4. Furthermore, the larger interaction surface area between the nanoflower-shaped ZnIn2S4 and the reactants facilitates proton generation and promotes the rapid formation of reaction intermediates. The formation of the type II heterostructure not only increases the number of high-energy electrons participating in the reduction reaction but also creates spatial isolation between electrons and holes, effectively suppressing recombination and thus improving photocatalytic activity. In conclusion, the results indicate that the type II heterostructure between HTN and ZIS can be used as an effective photocatalyst for hydrogen production under visible light irradiation. Beneficial effects

[0020] Compared with existing inventions, the present invention provides a ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials, their preparation methods, and applications have the following advantages:

[0021] (1) The preparation process of this invention is simple, low-cost, efficient, environmentally friendly, safe and convenient;

[0022] (2) The ZnIn2S4 / H obtained in this invention + Ti2NbO7 - The unique 3D-2D core-shell structure of the photocatalytic composite material increases the specific surface area of ​​the constructed photocatalyst, exposes more active reaction sites, and improves the mobility of the photogenerated support.

[0023] (3) ZnIn2S4 / H + Ti2NbO7 - The hydrogen production performance of the photocatalytic composite material was improved by 1.7 times compared with the pure ZnIn2S4 sample. Attached Figure Description

[0024] Figure 1 XRD patterns of composite materials prepared in different embodiments and comparative examples of the present invention;

[0025] Figure 2 The images shown are SEM images of Embodiment 3 of the present invention: (a) ZIS, (b) HTN, (c) TZ-3, and (d) TEM image.

[0026] Figure 3 The following are comparison graphs of hydrogen production in various embodiments, where (a) is a hydrogen production graph over 5 hours and (b) is a graph of average hourly hydrogen production.

[0027] Figure 4 The present invention is ZnIn2S4 / H + Ti2NbO7 - Photocatalytic mechanism of photocatalytic composite materials;

[0028] Figure 5 The figures shown are for testing the stability of the samples of this invention. (a) is the XRD pattern before and after the reaction in Example 3, and (b) is the hydrogen production data after 16 hours of continuous reaction in Example 3. Detailed Implementation

[0029] The following embodiments are provided to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Example 1

[0030] A ZnIn2S4 / H + Ti2NbO7 - The preparation method of photocatalytic composite material includes the following steps:

[0031] Step 1: Mix Cs2CO3, Nb2O5 and TiO2 in a certain proportion, grind them carefully in a dry environment, and keep them at 750 ℃, 950 ℃ and 1050 ℃ for 12 hours each to obtain CsTi2NbO7 powder.

[0032] Step 2: To obtain HTi₂NbO₇, 5.0 g of the prepared CsTi₂NbO₇ was added to 500 ml of nitric acid aqueous solution (1 mol) and stirred at 60 °C for 72 hours, with the acid being replaced every 24 hours. 1.0 g of HTi₂NbO₇ was then distributed to 100 ml of distilled water. A certain amount of tetrabutylammonium hydroxide (TBAOH) solution was added to the suspension until the pH reached 9.5-10. After continuous stirring for 7 days, the supernatant was collected by high-speed centrifugation to obtain HTi₂NbO₇ nanosheets. Then, 0.1 mM HNO₃ aqueous solution was added to the HTi₂NbO₇ nanosheets, causing HNO₃ to... + Re-stacking H + Ti2NbO7 - The nanosheets were immediately aggregated (denoted as HTN), and the precipitate HTN was dried in a petri dish and collected.

[0033] Step 3: Weigh 0.0150 g of HTN and place it in 60 ml of deionized water. Stir vigorously until homogeneous. Then, add 0.1610 g of ZnCl2, 0.6928 g of InCl3·4H2O, and 0.7100 g of TAA to the stirred liquid phase one by one. Continue stirring for 30 minutes. Then, place the mixture in a 100 ml reactor and incubate at 160 ℃ in an oven for 16 hours. After naturally cooling to room temperature, collect the product, wash it with deionized water, and finally dry it for 12 hours. The final sample is designated as TZ-1. Example 2

[0034] The mass of HTN in step 3 was changed to 0.0250 g, and the rest was the same as in Example 1. The final sample was denoted as TZ-2. Example 3

[0035] The mass of HTN in step 3 was changed to 0.0350 g, and the rest was the same as in Example 1. The final sample was denoted as TZ-3. Example 4

[0036] The mass of HTN in step 3 was changed to 0.0450 g, and the rest was the same as in Example 1. The final sample was denoted as TZ-4.

[0037] 0.1610 g ZnCl2, 0.6928 g InCl3·4H2O, and 0.7100 g TAA were added sequentially to 60 ml of deionized water. The mixture was stirred for 30 minutes, then placed in a 100 ml reactor and incubated in a 160 °C oven for 16 hours. After natural cooling to room temperature, the product was collected, washed with deionized water, and finally dried for 12 hours. The final sample, ZnIn2S4, was denoted as ZIS.

[0038] The mass of HTN in step 3 was changed to 0.0350 g, and the rest was the same as in Example 1. The final sample was denoted as TZ-3.

[0039] The ZnIn2S4 / H prepared in Examples 1-4 of this invention + Ti2NbO7 - Photocatalytic composite materials, single ZnIn2S4 and H + Ti2NbO7 - The performance test was conducted using the following methods:

[0040] Characterization of catalysts:

[0041] XRD analysis of the samples was performed using a Shimadzu XRD-6000 X-ray diffractometer (Japan), with a Cu target (λ = 0.1541 nm) and a graphite monochromator. The tube voltage was 40 kV, the tube current was 30 mA, the scanning speed was 5 ° / min, and the scanning angle range was 10–80 °. The ZnIn2S4 / H samples prepared in Examples 1–4 of this invention were analyzed. + Ti2NbO7 - Photocatalytic composite materials, single ZnIn2S4 and H + Ti2NbO7 - X-ray powder diffraction analysis was performed, and the results are as follows: Figure 1 The image shows ZnIn2S4, H + Ti2NbO7 - and ZnIn2S4 / H + Ti2NbO7 - The XRD pattern of the prepared ZnIn2S4 catalyst showed no diffraction related to pure CsTi2NbO7, indicating that the reaction between the precursors was very complete, consistent with the literature. The XRD pattern of the prepared ZnIn2S4 catalyst showed diffraction peaks at 21.6, 27.7, 30.4, 47.2, 52.4, and 56.3°, which are attributed to the (006), (102), (104), (110), (116), and (203) crystal planes of the hexagonal phase, respectively.

[0042] The morphology of the samples in Example 3 was characterized using a QUANTA 200 scanning electron microscope (SEM) (FEI Corporation, USA) and a JEM-2100 transmission electron microscope (TEM) (JEOL Corporation, Japan). To further verify the above-mentioned speculations regarding substance identification and to further analyze ZnIn2S4 and H... + Ti2NbO7 - and ZnIn2S4 / H+ Ti2NbO7 - The microstructure characteristics of photocatalytic materials, such as Figure 2 (a) shows ZnIn2S4. As can be seen from the figure, ZnIn2S4 exhibits microspheres with a diameter of approximately 4 μm. Figure 2 (b) H can be observed + Ti2NbO7 - It exhibits a distinct layered structure with a large amount of H + Ti2NbO7 - Nanosheets overlapped together. ZnIn2S4 / H + Ti2NbO7 - The morphology of the composite material is as follows Figure 2 As shown in (c), H + Ti2NbO7 - Nanosheets were uniformly loaded onto ZnIn2S4, increasing the specific surface area. Furthermore, the ultrathin nanosheet structure effectively increased the number of reactive sites, thereby improving the hydrogen production rate. The interface of the heterojunction composite material was studied using transmission electron microscopy. Figure 2 (d) The morphology of ZnIn2S4 is clearly visible, in which ZnIn2S4 and H are present. + Ti2NbO7 - Closely integrated, in Figure 3 (f) shows the lattice fringes of ZnIn2S4 and H + Ti2NbO7 - The lattice fringes are visible, and ZnIn2S4 and H can be observed. + Ti2NbO7 - The close contact interface between them.

[0043] Photocatalytic performance testing: Photocatalytic performance was tested by simulating hydrogen production rates under visible light conditions.

[0044] Weigh 45 ml of deionized water and 40 mg of sample. Mix the materials thoroughly, then add 0.4 ml of chloroplatinic acid solution to the reaction solution. Use a 300 W xenon lamp (PLS-SXE300C, Beijing Perfectlight Co., Ltd.) as the light source and irradiate for 30 min in a full-spectrum environment to load Pt. Finally, add 5 ml of triethanolamine as a sacrificial agent. Use a 300 W xenon lamp (PLS-SXE300C, Beijing Perfectlight Co., Ltd.) as the light source (k>420 nm). Detect H2 using an online gas chromatograph (Umeda, TCD, Ar support). Hydrogen production procedure: First, evacuate the instrument to a vacuum, wait for a period of time to ensure the instrument is leak-free, then adjust the chromatography, measure for 5 hours, take samples every hour, set the bridge current to 60 mA, and then start the experiment.

[0045] Furthermore, in order to verify ZnIn2S4, H + Ti2NbO7 - and ZnIn2S4 / H + Ti2NbO7 - The hydrogen production rate of the visible light photocatalyst. This experiment conducted a comprehensive visible light photocatalytic hydrogen production experiment on the prepared samples.

[0046] from Figure 3 As can be seen, the hydrogen production of the materials gradually increases with the extension of illumination time, showing a linear growth trend. Among them, TZ-3 has the best hydrogen production performance. Figure 3 The results show that the H2 generation rates of TZ-1, TZ-2, TZ-3, TZ-4, and ZS are 0.95, 1.13, 2.21, 1.34, and 1.26 mmol g, respectively. -1 h -1 This reveals that as the proportion of HTN increases, the hydrogen production rate first rises and then falls, reaching its highest level among different heterojunctions when the proportion reaches 7%. Furthermore, when H... + Ti2NbO7 - When the loading exceeds 7%, the activity growth slows significantly, which should be due to H + Ti2NbO7 - This is due to the reduced utilization rate.

[0047] Figure 5 (a) shows the XRD patterns of TZ-7 before and after irradiation. Clearly, the heterojunction retains its crystal structure, as there is no significant shift in the XRD peaks before and after irradiation. This finding confirms that the heterostructure is stable and does not undergo any structural changes due to illumination.

[0048] 40 mg of photocatalyst was mixed with 50 mL of 10% triethanolamine (TEOA) aqueous solution. To deposit the co-catalyst Pt, an appropriate amount of chloroplatinic acid was added to the reaction solution, resulting in a loading of 1 wt%. A 300 W xenon lamp (PLS-SXE300C, Beijing Perfectlight Co., Ltd.) with a wavelength greater than 420 nm was used as the light source. The H2 yield was measured using an online gas chromatograph (Umeda, TCD, Ar support). After 16 hours of continuous hydrogen production, the results are as follows: Figure 5 As shown in (b), the heterostructure exhibits good photochemical stability without a significant decrease in hydrogen production capacity. The synthesis method of this invention is a one-step hydrothermal process, requiring no secondary treatment, thus ensuring the stability of the heterostructure and preserving the ZnIn2S4 and H+ ions. + Ti2NbO7 - The contact between them effectively preserved the composite structure. In-situ growth during the hydrothermal process promoted the growth of ZnIn2S4 and H...+ Ti2NbO7 - The strong interactions between them lead to close contact and bonding, which further enhances the photostability of the TZ-7 heterostructure.

[0049] In summary, this invention prepares ZnIn2S4 / H via a one-step hydrothermal method. + Ti2NbO7 - The photocatalytic composite material of this invention has the advantages of low cost, environmental friendliness, safety and convenience, and simple process. The resulting ZnIn2S4 / H + Ti2NbO7 - The photocatalytic composite material has numerous surface active regions, exhibits visible light response, and demonstrates stable photocatalytic performance, further proving that ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials can be applied to the field of photocatalytic hydrogen production.

[0050] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A ZnIn2S4 / H + Ti2NbO7 - The application of photocatalytic composite materials in photocatalytic water splitting for hydrogen production is characterized by, The ZnIn2S4 / H + Ti2NbO7 - The preparation method of photocatalytic composite material includes the following steps: Step 1: Cs2CO3, Nb2O5 and TiO2 are mixed in a certain proportion and ground in a dry environment. The mixture is then kept at 750 ℃, 950 ℃ and 1050 ℃ for 12 hours each to obtain CsTi2NbO7 powder. The molar ratio of Cs2CO3, Nb2O5 and TiO2 is 1.12:1:

4. Step 2: CsTi₂NbO₇ was added to an aqueous nitric acid solution and stirred at 60 °C for 72 hours, with the acid solution replaced every 24 hours. 1.0 g of HTi₂NbO₇ was then distributed into distilled water, followed by the addition of tetrabutylammonium hydroxide solution until the pH reached 9.5-10. After continuous stirring for 7 days, the supernatant was collected by high-speed centrifugation to obtain HTi₂NbO₇ nanosheets. Then, an aqueous HNO₃ solution was added to the HTi₂NbO₇ nanosheets, causing HNO₃ to... + Re-stacking H + Ti2NbO7 - The immediate aggregation of nanosheets was observed. The precipitate HTN was dried in a petri dish at 70 °C and collected. Step 3: Weigh out HTN and place it in deionized water. Stir vigorously until homogeneous. Then, add ZnCl2, InCl3·4H2O, and TAA one by one to the above stirred liquid phase. Continue stirring for 30 minutes. Then, place it in a 100 ml reactor and hydrothermally react in an oven at 160 °C for 16 hours. After naturally cooling to room temperature, collect the product, wash it with deionized water, dry it, and collect it to obtain a 3D / 2D core-shell structured ZnIn2S4 / H + Ti2NbO7 - Photocatalytic composite materials.

2. The application according to claim 1, characterized in that, The heating rate in step 1 is 5-10 ℃ / min.

3. The application according to claim 1, characterized in that, In step 2, the centrifugation speed is 4000 r / min.

4. The application according to claim 1, characterized in that, In step 3, the drying temperature is 60 ℃ and the time is 12 hours.

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