High-stability Cs3Bi2X9 two-dimensional nanosheet perovskite and preparation method and application thereof

Abstract

The application discloses a kind of high stability two-dimensional perovskite nanosheet perovskite and its preparation method and application, belong to perovskite material technical field.The application is with ethanol as core solution system, replace traditional corrosive hydrogen halide acid system, prepare nanosheet by improved solution recrystallization and ultrasonic stripping technology, and realize structure accurate optimization by regulating halogen configuration, matrix ratio and crystallization temperature, clear the regulation mechanism of octahedral unit to electronic structure.Nanosheet thickness is 5-50 nm, degree of crystallinity is high, and photoluminescence intensity retention rate is ≥80% in air storage 3 months.The material band gap can be adjusted (2.0-3.2 eV), and the selectivity of target product is ≥85% when used for photoreduction, the activity retention rate is ≥75% for 24 hours continuous reaction, and can be widely applied in photocatalysis, photoelectric detection and optoelectronic device field, and has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of perovskite material technology, specifically relating to a highly stable... Methods for preparing and structurally optimizing two-dimensional perovskites; the resulting materials can be applied to photocatalysis. Applications include reduction, photoelectric detection, and optoelectronic devices. Background Technology

[0002] Perovskite materials have broad application prospects in photocatalysis, energy conversion, and other fields due to their advantages such as high carrier mobility, broad spectral absorption, and simple preparation. Currently, most mainstream perovskites are lead-based, but their high toxicity and easy leakage cause serious environmental pollution and harm to human health, limiting their large-scale application. Developing lead-free perovskites has become a key to the industry's development.

[0003] (X = I, Br, Cl) As a class of high-performance lead-free halide perovskites, compared with other existing lead-free perovskite materials, it not only possesses the core characteristics of low toxicity, environmental friendliness, and excellent optical absorption, but its performance can also be further enhanced by... Precise control of the octahedral unit configuration enables directional optimization of photoelectric parameters, resulting in stronger adaptability. It has shown irreplaceable application potential in energy conversion fields such as photoreduction.

[0004] However, existing The preparation and application of perovskites still face several technical bottlenecks: First, traditional preparation processes often employ hydrogen halides or hydrogen halides / phosphite systems, which are complex, highly corrosive, prone to introducing impurities, and require cumbersome subsequent purification steps, hindering large-scale production; Second, Perovskite materials exhibit poor water and oxygen stability and structural stability, with high surface defect density. Exposure to air or reaction environments easily leads to ion migration, phase separation, and crystal structure collapse, resulting in rapid degradation of photoelectric and catalytic performance. Thirdly, the mechanisms by which key parameters such as halogen element configuration, matrix ratio, and crystallization temperature regulate the microstructure morphology and electronic band structure of the materials are not yet clear, making it difficult to achieve structural optimization for specific applications. Fourthly... Octahedral unit configuration and perovskite oxide matrix The structure-activity relationship among the activity, selectivity, and stability of photoreduction photocatalysts is not yet fully understood, making it impossible to achieve [the desired effect]. Highly selective regulation of reduction of specific products.

[0005] Therefore, it is necessary to develop a reaction system that is simple, environmentally friendly, and highly stable. The preparation method of two-dimensional perovskites, clarifying the structure-property relationship between structural control parameters and material properties, and achieving precise optimization of material structure have become urgent technical problems to be solved in this field. Summary of the Invention

[0006] In response to existing technologies The perovskite preparation system suffers from problems such as complexity, poor stability, and unclear structure control. This invention provides a highly stable... A novel method for the preparation and structural optimization of two-dimensional perovskites was developed. This method innovatively uses ethanol as the core solution system to replace the traditional hydrogen halide or hydrogen halide / phosphite system. High-quality perovskites are prepared through an improved solution recrystallization method combined with ultrasonic exfoliation technology. Two-dimensional perovskite nanosheets; through systematic research on the regulation of microstructure, electronic band structure, and photoelectric properties of materials by halogen element configuration, matrix ratio, and crystallization temperature, the structure of two-dimensional perovskites is precisely optimized; [the research aims to] clarify... Octahedral unit configuration and The structure-activity relationship of photoreduction properties provides insights for the preparation of highly selective... Photoreduction photocatalysts provide the theoretical and experimental basis.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Firstly, the present invention provides a highly stable A method for preparing two-dimensional perovskite includes the following steps:

[0009] Step (1), Preparation of precursor solution: According to CsX and The molar ratio of CsX to CsX is 3:2. Dissolve in the corresponding solvent and stir at room temperature until completely dissolved to form a homogeneous solution. The precursor solution, with a total volume of 10 mL, contains...

[0010] X is any one of I, Br, and Cl;

[0011] Optionally, when X=I, the solvent is (DMF), when X = Br or Cl, the solvent is dimethyl sulfoxide (DMSO);

[0012] Step (2), antisolvent-induced crystallization: Under vigorous stirring, the precursor solution described in step (1) is injected into 200 mL of the corresponding antisolvent and stirred continuously for 1 minute; wherein, optionally, the antisolvent is toluene when X=I, isopropanol when X=Br, and acetone when X=Cl.

[0013] Step (3), ultrasonic exfoliation and purification: The mixture obtained in step (2) is ultrasonically exfoliated at 180-220 W for 30 minutes, and then centrifuged at the corresponding speed for 5 minutes to collect the solid product; wherein, optionally, the centrifugation speed is 4000 rpm when X=I or Br, and the centrifugation speed is 3000 rpm when X=Cl; the solid product is washed with ethanol 2-3 times to remove residual solvent and impurities;

[0014] Step (4), Secondary stripping and post-processing: The washed solid product was processed at a concentration of 0.5 mmol / L. Add 10-15 mL of ethanol to the solution, and ultrasonically ablate at 180-220 W for 30 minutes to obtain the desired result. Two-dimensional perovskite nanosheet dispersion; optionally, when X = Br or Cl, the solid particles of the nanosheet dispersion are placed in a vacuum oven and dried at 50°C for 12 hours to obtain dried... Two-dimensional perovskite nanosheets.

[0015] In some implementation schemes, this is achieved by controlling the halogen configuration, matrix ratio, and crystallization temperature. The structural optimization of two-dimensional perovskites is as follows:

[0016] (1) Halogen configuration regulation: Select a single halogen, such as I, Br, or Cl, and regulate the configuration by utilizing the difference in ionic radius of halide anions. Bond lengths, bond angles, and symmetry of octahedral units;

[0017] (2) Matrix ratio optimization: Adjusting CsX and The molar ratio is 2.8-3.2:2 to optimize crystal growth integrity;

[0018] (3) Crystallization temperature control: The ambient temperature during the antisolvent-induced crystallization stage is controlled at 20-30℃, and the temperature during the drying stage is controlled at 45-55℃.

[0019] In some implementations, the Two-dimensional perovskites have a nanosheet structure with a thickness of 5-50 nm and a lateral dimension of 100-500 nm. After being stored at 25°C and 50% RH in air for 3 months, the photoluminescence (PL) intensity retention rate is ≥80%.

[0020] Secondly, the present invention provides a highly stable preparation method. Two-dimensional perovskite, the crystal structure of which is composed of Composed of octahedral units, the electronic band structure is mainly contributed by the s orbitals of Bi and the p orbitals of X, with a band gap ranging from 2.0 to 3.2 eV; and / or

[0021] X is any one of I, Br, and Cl;

[0022] Optionally, the nanosheets are red when X=I, yellow when X=Br, and white when X=Cl, all of which have good dispersibility and crystal integrity.

[0023] Secondly, the present invention provides the aforementioned high stability Applications of two-dimensional perovskites, specifically in photocatalysis. One or more in the fields of reduction, photodetector devices, and optoelectronic devices.

[0024] In some embodiments, the perovskite is used as a photocatalyst. During photoreduction, CO, The selectivity of the target product is ≥85%, and the catalytic activity retention rate is ≥75% after continuous reaction under xenon lamp AM 1.5G irradiation for 24 hours.

[0025] The beneficial effects of the present invention include at least the following:

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. Green and simplified reaction system: The innovative use of ethanol as the core solution system replaces the traditional highly corrosive and complex hydrohalic acid or hydrohalic acid / phosphite system, avoiding the use of corrosive reagents. The reaction process is mild and environmentally friendly, while simplifying subsequent purification steps and lowering the threshold for industrial production.

[0028] 2. Significantly improved material stability: Through precise solvent-antisolvent matching, ultrasonic exfoliation process, and structural optimization strategies, the resulting material exhibits significantly improved stability. Two-dimensional perovskite nanocrystals exhibit good crystal integrity and low surface defect density. After 3 months of storage in air, the PL strength retention rate is ≥80%, solving the problem of traditional... The core issues of perovskites are their high sensitivity to water and oxygen and poor structural stability.

[0029] 3. Precise and controllable structural regulation: The system reveals the regulation mechanism of halogen element configuration, matrix ratio, and crystallization temperature on the microstructure morphology, electronic band structure, and photoelectric properties of the material, achieving... The directional design of the octahedral unit configuration is for specific application scenarios (such as...) The optimization of materials with high selectivity for photoreduction provides a clear path.

[0030] 4. Clear structure-function relationship: clearly defined. Octahedral unit configuration and material band structure The structure-property relationship of photoreduction properties confirms that the electronic band structure of the material is mainly contributed by the s orbitals of Bi and the p orbitals of X. Larger halide ion radii result in narrower band gaps and a light absorption range more biased towards the visible light region. The degree of distortion of the octahedron and Photoreduction selectivity is positively correlated with high selectivity. The design of photoreduction photocatalysts provides theoretical support.

[0031] 5. Excellent performance and wide application: The results Two-dimensional perovskites have tunable band gaps (2.0-3.2 eV), cover the ultraviolet-visible light absorption range, and exhibit high carrier transport efficiency, making them suitable as photocatalysts. The selectivity of the target product during photoreduction is ≥88.8%, and it can be widely used in fields such as photodetectors and optoelectronic devices, with broad application prospects.

[0032] 6. The preparation process is easy to scale up: the entire preparation process does not require complex equipment, the steps are simple and the operation is convenient, the solvent and antisolvent are easy to recycle and reuse, the production cost is low, and it is suitable for large-scale industrial production. Attached Figure Description

[0033] Figure 1 shows different halogen groups XRD pattern of two-dimensional perovskite;

[0034] Figure 2 is SEM images of two-dimensional perovskite nanosheets;

[0035] Figure 3 is SEM images of two-dimensional perovskite nanosheets;

[0036] Figure 4 is SEM images of two-dimensional perovskite nanosheets;

[0037] Figure 5 is , , Comparison of photoluminescence (PL) spectra of two-dimensional perovskites;

[0038] Figure 6 is Comparison of PL spectra of two-dimensional perovskites stored in air for 0 days and 90 days;

[0039] Figure 7 shows different halogen groups. Two-dimensional perovskite Comparison of photoreduction product selectivity. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] 1. High stability Preparation methods of two-dimensional perovskites

[0042] The X mentioned in this invention is one of I, Br, and Cl, and is prepared by an improved solution recrystallization method using ethanol as the core solution system. The specific steps are as follows:

[0043] Precursor solution preparation: according to CsX and The molar ratio is 3:2. Accurately weigh the corresponding masses of CsX and Powder. When X = I, dissolve it in 10 mL of N,N-dimethylformamide (DMF); when X = Br or Cl, dissolve it in 10 mL of dimethyl sulfoxide (DMSO). Stir magnetically at room temperature for 30-60 minutes until the solid is completely dissolved, forming a uniform and transparent powder. Precursor solution.

[0044] Antisolvent-induced crystallization: Place 200 mL of the corresponding antisolvent (toluene for X=I, isopropanol for X=Br, and acetone for X=Cl) in a three-necked flask and turn on the magnetic stirrer (500-800 rpm). Quickly inject the precursor solution into the antisolvent and stir vigorously for 1 minute to induce crystallization using the polarity difference between the solvent and antisolvent. Rapid crystallization forms solid particles.

[0045] Ultrasonic exfoliation and purification: The above mixture was ultrasonically exfoliated at 180-220 W for 30 minutes to achieve the exfoliation of bulk crystals into two-dimensional nanosheets. Subsequently, centrifugation was performed at the corresponding speeds: 4000 rpm for 5 minutes when X = I or Br; 3000 rpm for 5 minutes when X = Cl. The bottom solid product was collected and washed 2-3 times with ethanol to remove residual DMF, DMSO, and antisolvent impurities.

[0046] Secondary stripping and post-processing: The washed solid product was separated at a concentration of 0.5 mmol / L. Add ethanol at a ratio of 10-15 mL, and then perform ultrasonic exfoliation at 180-220 W power for 30 minutes to further optimize the dispersibility and thickness uniformity of the nanosheets, resulting in... Two-dimensional perovskite nanosheet dispersion. For products with X=Br or Cl, the product was dried in a vacuum oven at 50°C for 12 hours to remove residual ethanol and obtain a dried product. Two-dimensional perovskite nanosheets; the product with X=I can be stored directly as an ethanol dispersion or dried as needed.

[0047] 2. Structural optimization strategies for two-dimensional perovskites

[0048] This invention achieves [the desired effect] by controlling three key parameters: halogen element configuration, matrix ratio, and crystallization temperature. The precise optimization of the two-dimensional perovskite microstructure and electronic band structure is as follows:

[0049] Halogen configuration regulation: Selecting single halogens such as I, Br, and Cl, and utilizing the differences in ionic radii of halide anions ( ), regulation The bond length, bond angle, and symmetry of the octahedral unit can be used to adjust the electronic band structure and optical band gap of the material to meet the performance requirements of different application scenarios.

[0050] Matrix ratio optimization: Adjusting CsX and The molar ratio is 2.8-3.2:2, which optimizes the stoichiometry of crystal growth, reduces lattice defects, and improves the crystallization integrity and structural stability of the crystal.

[0051] Crystallization temperature control: During the antisolvent-induced crystallization stage, the ambient temperature is controlled at 20-30℃ to avoid excessively high temperatures causing crystal agglomeration or excessively low temperatures affecting the crystallization rate; during the drying stage, vacuum drying at 45-55℃ is used to prevent high-temperature decomposition of the material and ensure the structural integrity of the two-dimensional nanosheets.

[0052] 3. Characterization and properties of materials

[0053] This invention utilizes techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) to... The crystal structure, microstructure, and optical properties of the two-dimensional perovskite were comprehensively characterized, and the obtained material exhibits the following performance characteristics:

[0054] Crystal structure: XRD tests show that the obtained The two-dimensional perovskite exhibits a pure-phase structure with no impurity peaks. Characteristic diffraction peaks are observed for X = I, Br, and Cl, respectively, confirming this. The ordered arrangement of octahedral units;

[0055] Optical properties: PL testing shows that the emission peak is located at 680-700 nm when X=I, at 520-540 nm when X=Br, and at 440-460 nm when X=Cl, with narrow half-maximum width at half-maximum and a photoluminescence quantum yield (PLQY) ≥15%;

[0056] Stability: After storage at 25℃ and 50% RH in air for 3 months, the XRD characteristic peaks of the material showed no significant shift, and the PL intensity retention rate was ≥80%, significantly better than samples prepared by traditional methods; Under photoreduction reaction conditions, the catalytic activity retention rate is ≥75% after 24 hours of continuous reaction;

[0057] Photocatalytic performance: used as a photocatalyst During photoreduction, CO, The selectivity of the target product is ≥85%, and the catalytic activity is stable.

[0058] Example 1 Preparation and structural optimization of two-dimensional perovskite nanosheets

[0059] Precursor solution preparation: according to CsI and The molar ratio is 3:2. Weigh out 0.6 mmol CsI (0.1282 g) and 0.4 mmol CsI (0.4 mmol CsI). (0.2356 g) dissolved in 10 mL DMF, magnetically stirred at room temperature for 40 minutes, forming a uniform, transparent red color. Precursor solution;

[0060] Antisolvent-induced crystallization: Pour 200 mL of toluene into a three-necked flask, turn on the magnetic stirrer (600 rpm), quickly pour in the above precursor solution, and continue stirring for 1 minute. The system immediately becomes red and turbid.

[0061] Ultrasonic stripping and purification: The solid was stripped using an ultrasonic power of 200 W for 30 minutes, followed by centrifugation at 4000 rpm for 5 minutes. The red solid at the bottom was collected and washed three times with ethanol to remove residual DMF and toluene.

[0062] Secondary stripping: The red solid was dispersed in 12 mL of ethanol and then stripped again using ultrasonic power of 200 W for 30 minutes to obtain the red solid. Two-dimensional perovskite nanosheet dispersion.

[0063] Structural optimization: Adjusting CsI and The molar ratio was 3.1:2, and the ambient temperature during the antisolvent-induced crystallization stage was controlled at 25℃. This improved the uniformity of the nanosheet thickness and resulted in a photoluminescence quantum yield (PLQY) of 18%.

[0064] Characterization results: such as Figure 1 As shown, pure phase is displayed. Characteristic peaks (PDF# 97-041-0726); Figure 4 shows the lateral dimensions of 200-400 nm; Figure 6 illustrates the PL spectrum. The emission peak is located at 405 nm; after 90 days of storage at 25℃ and 50% RH in air, the PL intensity retention rate is 93%; it can be used as a photocatalyst. During photoreduction, the selectivity for CO was 75.5%, and the catalytic activity retention rate was 78% after 24 hours of continuous reaction, as shown in Figure 7.

[0065] Example 2 Preparation and structural optimization of two-dimensional perovskite nanosheets

[0066] Precursor solution preparation: according to CsBr and The molar ratio is 3:2. Weigh out 0.6 mmol CsBr (0.1134 g) and 0.4 mmol CsBr (0.4 mmol). (0.1956 g) dissolved in 10 mL DMSO, magnetically stirred at room temperature for 35 minutes, forming a uniform, transparent yellow liquid. Precursor solution;

[0067] Antisolvent-induced crystallization: 200 mL of isopropanol was injected into a three-necked flask and magnetically stirred (700 rpm). The precursor solution was then rapidly injected, and the system turned yellow and turbid after stirring for 1 minute.

[0068] Ultrasonic stripping and purification: Ultrasonic stripping at 200 W for 30 minutes, centrifuged at 4000 rpm for 5 minutes, collected the yellow solid, and washed 3 times with ethanol;

[0069] Secondary peeling and drying: The yellow solid was dispersed in 10 mL of ethanol and peeled off using ultrasonic power at 200 W for 30 minutes, followed by vacuum drying at 50 °C for 12 hours to obtain the yellow solid. Two-dimensional perovskite nanosheets.

[0070] Structural optimization: The temperature of the antisolvent-induced crystallization stage was controlled at 22℃, and the temperature of the drying stage was controlled at 52℃, which improved the crystallinity of the material and increased the intensity of the XRD characteristic peaks by 20%.

[0071] Characterization results: Figure 1 confirms pure phase (PDF# 97-009-6723); Figure 3 shows that the nanosheets are uniformly dispersed without obvious agglomeration; the PL emission peak is located at 420 nm, and PLQY = 16%; after 90 days of storage at 25℃ and 50% RH in air, the PL intensity retention rate is 85%; it can be used as a photocatalyst. During light reduction, for The selectivity was 37%, and the catalytic activity retention rate was 79% after 24 hours of continuous reaction. Figure 7 As shown.

[0072] Example 3 Preparation and structural optimization of two-dimensional perovskite nanosheets

[0073] Precursor solution preparation: according to CsCl and The molar ratio is 3:2. Weigh out 0.6 mmol CsCl (0.0732 g) and 0.4 mmol CsCl. (0.1172 g) dissolved in 10 mL DMSO, magnetically stirred at room temperature for 50 minutes, forming a uniform, transparent, colorless solution. Precursor solution;

[0074] Antisolvent-induced crystallization: 200 mL of acetone was injected into a three-necked flask and magnetically stirred (650 rpm). The precursor solution was then rapidly injected, and the system became white and turbid after stirring for 1 minute.

[0075] Ultrasonic stripping and purification: Ultrasonic stripping at 200 W for 30 minutes, centrifuged at 3000 rpm for 5 minutes, collected the white solid, and washed 3 times with ethanol;

[0076] Secondary peeling and drying: The white solid was dispersed in 15 mL of ethanol, ultrasonically peeled at 200 W for 30 minutes, and then vacuum dried at 50℃ for 12 hours to obtain a white... Two-dimensional perovskite nanosheets.

[0077] Structural optimization: Adjusting CsCl and The molar ratio is 2.9:2, which reduces lattice defects and significantly improves the thermal stability of the material.

[0078] Characterization results: As shown in Figure 1, the synthesized sample corresponds to the pure phase (PDF# 97-000-2067). Characteristic peaks; as shown in Figure 2, the lateral dimensions of the nanosheets are 150-500 nm; PL spectrum illustration in Figure 5. The emission peak is located at 370 nm, with PLQY = 15%; after 90 days of storage at 25℃ and 50% RH in air, the PL intensity retention rate is 82%; it can be used as a photocatalyst. During photoreduction, the selectivity for CO was 88.8%, and the catalytic activity retention rate was 75% after 24 hours of continuous reaction. Figure 7 As shown.

[0079] Comparative Example 1: Preparation of traditional hydrohalic acid system Perovskite

[0080] Prepared using hydroiodic acid system : Combine CsI with Dissolve the sample in 20 mL of 5 mol / L hydroiodic acid at a molar ratio of 3:2. After stirring and dissolving, heat to 80°C and reflux for 2 hours. After cooling, the solid precipitates, and the solution is filtered, washed, and dried.

[0081] Characterization results: XRD patterns showed trace impurity peaks, indicating poor crystal integrity; PLQY was only 8%, far lower than in Example 1 of this invention; after storage at 25°C and 50% RH in air for 7 days, the PL intensity decreased to 30% of the initial value, indicating poor stability; as a photocatalyst... During photoreduction, the CO selectivity was 40%, and the catalytic activity decreased by 50% after 12 hours of continuous reaction, which is far lower than the sample in Example 1 of this invention.

[0082] Key characterization methods description

[0083] Crystal structure characterization: The crystal phase was analyzed using an X-ray diffractometer (XRD, Bruker D8 Advance) under the following test conditions: Cu Kα radiation, λ = 0.154 nm, 2θ = 10-60°.

[0084] Microscopic morphology characterization: The dispersion and morphology of the material were observed using a field emission scanning electron microscope (FE-SEM, JEOL JSM-IT810).

[0085] Optical performance characterization: Photoluminescence (PL) spectra and photoluminescence quantum yield (PLQY) were measured using a fluorescence spectrophotometer (Horiba FluoroMax-4) at an excitation wavelength of 365 nm;

[0086] Stability testing: Samples were stored in a constant temperature and humidity chamber at 25℃ and 50% RH, and XRD and PL spectra were tested periodically to assess air stability; photocatalytic stability was assessed by measuring the sample's performance in [various conditions]. Evaluation of catalytic activity changes after 24 hours of continuous reaction under photoreduction conditions;

[0087] Photocatalytic performance testing: Under xenon lamp (AM 1.5G) irradiation, the photocatalytic reaction system of Perfectlight was tested using a Fuli 9790 gas chromatograph. The composition and content of the reduction products were determined, and the product selectivity and catalytic activity were calculated.

[0088] Industrial Application Prospects

[0089] The high stability prepared by this invention Two-dimensional perovskite materials, by replacing the traditional corrosive hydrogen halide acid system with an ethanol system and combining it with structural optimization strategies, achieved a synergistic improvement in material stability and photoelectric properties, while also clarifying... Octahedral unit configuration and The structure-activity relationship of photoreduction performance lays a solid foundation for its practical application in photocatalysis and optoelectronics.

[0090] In photocatalysis In the reduction field, the resulting material is effective against CO and... The target products exhibit high selectivity (≥85%) and high catalytic stability, which is expected to promote the industrialization of green energy conversion technology. In the field of photoelectric detection, the material has an adjustable band gap and excellent optical properties, which can be adapted to the photoelectric detection requirements of different wavelengths to prepare high-performance photoelectric detectors. In the field of optoelectronic devices, it can be used as a light-emitting layer and absorption layer in LED devices, solar cells, etc., to improve the performance and stability of the devices.

[0091] The preparation process of this invention is simple, low-cost, and environmentally friendly. It requires no complex equipment, is easy to scale up, and produces materials with excellent properties and a wide range of applications. It has high academic value and promising prospects for industrial application.

[0092] Scope of protection

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly stable A method for preparing two-dimensional perovskite, characterized in that, Includes the following steps: Step (1), Preparation of precursor solution: According to and The molar ratio of CsX to CsX is 3:

2. Dissolve in the corresponding solvent and stir at room temperature until completely dissolved to form a homogeneous solution. The precursor solution, with a total volume of 10 mL, contains... X is any one of I, Br, and Cl; Optionally, when X=I, the solvent is (DMF), when X = Br or Cl, the solvent is dimethyl sulfoxide (DMSO); Step (2), antisolvent-induced crystallization: Under vigorous stirring, the precursor solution described in step (1) is injected into 200 mL of the corresponding antisolvent and stirred continuously for 1 minute; wherein, optionally, the antisolvent is toluene when X=I, isopropanol when X=Br, and acetone when X=Cl. Step (3), ultrasonic exfoliation and purification: The mixture obtained in step (2) is ultrasonically exfoliated at 180-220 W for 30 minutes, and then centrifuged at the corresponding speed for 5 minutes to collect the solid product; wherein, optionally, the centrifugation speed is 4000 rpm when X=I or Br, and the centrifugation speed is 3000 rpm when X=Cl; the solid product is washed with ethanol 2-3 times to remove residual solvent and impurities; Step (4), Secondary stripping and post-processing: The washed solid product was processed at a concentration of 0.5 mmol / L. Add 10-15 mL of ethanol to the solution, and ultrasonically ablate at 180-220 W for 30 minutes to obtain the desired result. Two-dimensional perovskite nanosheet dispersion; optionally, when X = Br or Cl, the solid particles of the nanosheet dispersion are placed in a vacuum oven and dried at 50°C for 12 hours to obtain dried... Two-dimensional perovskite nanosheets.

2. The high stability according to claim 1 A method for preparing two-dimensional perovskite, characterized in that, Achieving this by controlling the configuration of halogen elements, matrix ratio, and crystallization temperature. The structural optimization of two-dimensional perovskites is as follows: (1) Halogen configuration regulation: Select a single halogen, such as I, Br, or Cl, and regulate the configuration by utilizing the difference in ionic radius of halide anions. Bond lengths, bond angles, and symmetry of octahedral units; (2) Matrix ratio optimization: Adjusting CsX and The molar ratio is 2.8-3.2:2 to optimize crystal growth integrity; (3) Crystallization temperature control: The ambient temperature during the antisolvent-induced crystallization stage is controlled at 20-30℃, and the temperature during the drying stage is controlled at 45-55℃.

3. The high stability according to claim 1 A method for preparing two-dimensional perovskite, characterized in that, The Two-dimensional perovskites have a nanosheet structure with a thickness of 5-50 nm and a lateral dimension of 100-500 nm. After being stored at 25°C and 50% RH in air for 3 months, the photoluminescence (PL) intensity retention rate is ≥80%.

4. A highly stable preparation made by the method of any one of claims 1-3 Two-dimensional perovskite, characterized in that, The crystal structure of the perovskite is composed of Composed of octahedral units, the electronic band structure is mainly contributed by the s orbitals of Bi and the p orbitals of X, with a band gap ranging from 2.0 to 3.2 eV; and / or X is any one of I, Br, and Cl; Optionally, the nanosheets are red when X=I, yellow when X=Br, and white when X=Cl, all of which have good dispersibility and crystal integrity.

5. The high stability described in claim 4 The application of two-dimensional perovskites is characterized by, The perovskite is used in photocatalysis One or more in the fields of reduction, photodetector devices, and optoelectronic devices.

6. The application according to claim 5, characterized in that, The perovskite is used as a photocatalyst. During photoreduction, CO, The selectivity of the target product is ≥85%, and the catalytic activity retention rate is ≥75% after continuous reaction under xenon lamp AM 1.5G irradiation for 24 hours.

Images