Preparation method and application of layered double-perovskite micron crystal material

Abstract

The invention relates to a preparation method and application of a layered double-perovskite micro-crystal material, and belongs to the field of perovskite micro-crystal materials. Aiming at the defects of poor stability, high photogenerated charge recombination rate, low product selectivity and the like of a traditional perovskite photocatalyst, a Cs4Cd0. 8Cu0. 2Bi2Cl12 layered double-perovskite system is constructed through a Cu doping strategy. The preparation method comprises the following steps: dissolving cadmium chloride, copper chloride and bismuth chloride in hydrochloric acid, then adding cesium chloride, carrying out a low-temperature (60 DEG C) heating reaction, and then carrying out centrifugal cleaning and drying to obtain the micro-crystal material. According to the invention, the yield of CH4 is successfully increased to 7.2 [mu] mol / (g.h) (about 260% higher than that of an undoped system). The material keeps a stable structure after a photocatalytic reaction, has a visible light response characteristic, and breaks through the dependence of a traditional catalyst on ultraviolet light. The preparation process adopts a low-temperature solution method, the reaction time is less than 10 minutes, the energy consumption is reduced by about 60%, and low-cost large-scale production is realized.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite microcrystalline materials, and relates to a preparation method and application of layered double perovskite microcrystalline materials. Background Art

[0002] In order to reduce the level of carbon dioxide (CO2) in the atmosphere and address urgent environmental challenges, the development of efficient and sustainable CO2 capture and conversion technologies has become an urgent task. Photocatalytic CO2 reduction, which converts CO2 into high-value chemical fuels such as carbon monoxide, methanol, and methane, is a promising strategy for achieving carbon neutrality by producing chemical energy using renewable energy. Halide perovskites are considered a promising photocatalyst for CO2 reduction due to their excellent optoelectronic properties. However, their practical applications are limited by insufficient long-term stability under reaction conditions and unsatisfactory photocatalytic efficiency due to the rapid recombination of photo-generated charge carriers.

[0003] Traditional three-dimensional halide perovskite photocatalysts are prone to decomposition in humid environments, and ion migration occurs in the crystal structure under long-term light illumination, resulting in a rapid decay of catalytic activity. In addition, the efficient recombination problem of photo-generated electron-hole pairs significantly reduces the quantum efficiency, and there is a lack of effective charge transport channels inside the material, and only less than 30% of the photo-generated carriers can participate in the surface catalytic reaction.

[0004] Different from traditional three-dimensional (3D) double perovskites, two-dimensional (2D) perovskites, and perovskite quantum dots, layered double perovskites (LDPs) have a direct bandgap, fast and stable photoelectrochemical responses, and stability under humid and light conditions, making them strong candidates for CO2 reduction. Currently, there is relatively little research on layered double perovskites in the field of photocatalysis, and the structure of layered double perovskites allows for the optimization of their photocatalytic performance by adjusting the types of metal ions and anions. This flexibility enables the design of materials according to specific application requirements. In the field of photocatalysis, the efficient utilization of visible light, which accounts for approximately 50% of solar energy, has always been a research hotspot and difficulty. Most existing photocatalytic systems rely on ultraviolet light excitation, but ultraviolet light has a low proportion in solar energy and the equipment is complex and expensive.

[0005] Based on the above technical bottlenecks, there is an urgent need to develop a new type of layered double perovskite photocatalytic material with high stability, wide spectral response characteristics, and precise product selectivity, and to achieve its functional regulation through a simple and scalable preparation process. This has become the core breakthrough for promoting the transformation of photocatalytic CO2 reduction technology from the laboratory to practical applications. Summary of the Invention

[0006] In view of this, one of the objectives of the present invention is to provide a preparation method of a layered double perovskite microcrystalline material, and the second objective is to provide an application of the layered double perovskite microcrystalline material in photocatalytic CO2 reduction.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a layered double perovskite microcrystalline material, and the preparation method includes the following steps:

[0009] (1) Add cadmium chloride, copper chloride, and bismuth chloride to hydrochloric acid, stir to dissolve until it becomes clear, and prepare a precursor solution;

[0010] (2) Add cesium chloride to the precursor solution prepared in step (1), heat and stir, and fully react to obtain a reaction mixture;

[0011] (3) Centrifuge the reaction mixture obtained in step (2) to remove the supernatant, and repeatedly centrifuge and wash with absolute ethanol to obtain a sample precipitate. After vacuum drying, the layered double perovskite microcrystalline material can be obtained;

[0012] Preferably, in step (1), the molar volume ratio of cadmium chloride, copper chloride, bismuth chloride, and hydrochloric acid solution is 0.8:0.2:2:10; mmol:mmol:mmol:ml, and the stirring time is 8-10 min;

[0013] Preferably, in step (2), the molar volume ratio of cesium chloride to the mixed solution prepared in step (1) is 4:10; mmol:ml;

[0014] Preferably, in step (2), the heating temperature is 60 °C, and the reaction time is 5-8 min;

[0015] Preferably, in step (3), the rotation speed of the centrifugation is 4000-5000 rpm, and the centrifugation time is 5-8 min;

[0016] Preferably, in step (3), the temperature of the vacuum drying is 40-60 °C, and the time is 12-24 h;

[0017] Furthermore, for the layered double perovskite microcrystalline material prepared by the preparation method, the chemical formula of the layered double perovskite microcrystalline material is Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ;

[0018] Furthermore, the application of the layered double perovskite microcrystalline material in photocatalytic CO2 reduction.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention discloses a preparation method of a Cu-doped layered double perovskite microcrystalline material, mainly using CsCl, CdCl2, CuCl2, BiCl3, dissolving the raw materials by adding hydrochloric acid, and washing with absolute ethanol. The preparation method of the present invention is simple, easy to operate, has low requirements for equipment, and has the advantages of low cost and low energy consumption, and is suitable for large-scale production; in addition, the layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared by the present invention has the characteristics of stability and high selectivity of photocatalytic products, and has good application prospects in photocatalytic CO2 reduction.

[0021] Through the Cu-doped layered double perovskite structure (Cs4Cd0.8Cu0.2Bi2Cl12), compared with the undoped Cs4CdBi2Cl12 material: a CH4 production rate of 7.2 μmol / (g·h) is achieved (about 260% higher than the undoped system), the material remains structurally stable after the photocatalytic reaction, has visible light response characteristics, and breaks through the dependence of traditional catalysts on ultraviolet light. The preparation process adopts a low-temperature solution method, the reaction time is less than 10 minutes, and the energy consumption is reduced by about 60%, realizing low-cost large-scale production.

[0022] Synthesized by a low-temperature (60 °C) solution method, the equipment requirements are low, and it is more cost-effective compared with the traditional high-temperature solid-phase method; the dissolution of the precursor is regulated through a hydrochloric acid medium, simplifying the reaction process (only a reaction time of about 10 min is required).

[0023] Operating under visible light (non-ultraviolet light), the response wavelength range is broadened; the product selectivity is significantly improved: the total CH4 production is increased by about 260%, solving the problem of low selectivity of the catalyst.

[0024] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0026] Figure 1 For the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl12 ) and the X-ray powder diffraction pattern (XRD) of the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example;

[0027] Figure 2 For the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the scanning electron microscope image (SEM) of the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example;

[0028] Figure 3 For the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the bar chart of CH4 production (a) and the bar chart of CO production (b) of the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example;

[0029] Figure 4 After the photocatalytic test, for the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 )(a) and the scanning electron microscope image (SEM) of the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 )(b) prepared in the comparative example. Detailed implementation manners

[0030] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention schematically. Without conflict, the following examples and the features in the examples can be combined with each other.

[0031] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than actual physical diagrams, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0032] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] Example 1

[0034] A layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ), and the specific preparation method includes the following steps:

[0035] (1) Add 0.6307 g of bismuth chloride (BiCl3), 0.0268 g of copper chloride (CuCl2), and 0.1466 g of cadmium chloride (CdCl2) to 10 ml of hydrochloric acid, and stir to dissolve until it becomes clear;

[0036] (2) Add 0.6734 g of cesium chloride (CsCl) to the above solution, and stir to mix well to obtain a reaction mixture;

[0037] (3) Centrifuge the above reaction mixture at a speed of 5000 rpm for 5 min to remove the supernatant to obtain a precipitate, and add 10 ml of absolute ethanol for centrifugal washing (the centrifugal washing speed is 5000 rpm and the centrifugal time is 5 min), repeat three times to obtain a sample precipitate, and place the sample precipitate in a vacuum drying oven at 60 °C for drying for 12 h to obtain the layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ).

[0038] Comparative Example 1

[0039] A layered double perovskite microcrystalline material (Cs4CdBi2Cl 12), and the specific preparation method includes the following steps:

[0040] (1) Add 0.6307 g of bismuth chloride (BiCl3) and 0.1833 g of cadmium chloride (CdCl2) to 10 ml of hydrochloric acid, and stir to dissolve until it becomes clear;

[0041] (2) Add 0.6734 g of cesium chloride (CsCl) to the above solution, and stir to mix well to obtain a reaction mixture;

[0042] (3) Centrifuge the above reaction mixture at a speed of 5000 rpm for 5 min to remove the supernatant, and then add 10 ml of absolute ethanol for centrifugal washing (the centrifugal washing speed is 5000 rpm and the centrifugal time is 5 min). Repeat three times to obtain a sample precipitate. Place the sample precipitate in a vacuum drying oven at 60 °C and dry for 12 h to obtain a layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ).

[0043] Example 2 Performance Test

[0044] Using the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 as a sample and the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example as a control, test the relevant performance, as follows:

[0045] Perform X-ray powder diffraction test (XRD) on the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example. The results are as Figure 1 shown. It can be seen from Figure 1 that the diffraction characteristic peaks of the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example are consistent with the simulated characteristic peaks. Cs4Cd 0.8 Cu 0.2 Bi2Cl 12The diffraction peak angle of the microcrystalline material shifts towards a higher diffraction peak angle due to ion substitution, and there are no other extra diffraction peaks, indicating the successful synthesis of Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 and Cs4CdBi2Cl 12 .

[0046] The Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example were analyzed by scanning electron microscopy (SEM). The results are shown in a and b of Figure 2 respectively, and both materials have a microcrystalline structure.

[0047] To better verify the properties of the Cu-doped layered double perovskite microcrystalline material Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 of the present invention, the photocatalytic performance of the Cu-doped layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 was tested. The test method is as follows: First, 3 mg of the layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 was added to a test tube containing 1 ml of absolute ethanol, and ultrasonicated for 30 min to uniformly disperse the layered double perovskite microcrystalline material Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 in the absolute ethanol solution to obtain a mixed solution; Secondly, the obtained mixed solution was dropped onto an electronic-grade glass slide dried on a 60°C drying table with a dropper to completely evaporate the absolute ethanol. The above operation was repeated until the mixed solution in the test tube was completely dropped, and Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 powder was uniformly distributed on the glass slide to obtain the prepared sample; Then, the prepared sample was placed in a gas chromatograph for 3 hours of photocatalytic performance testing (under visible light). At the same time, the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example was also subjected to the same above operations. The test results are shown in Figure 3 , where a is the bar chart of CH4 production and b is the bar chart of CO production. FromFigure 3 It can be clearly seen that Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 has significantly higher photocatalytic performance than Cs4CdBi2Cl 12 .

[0048] After the photocatalytic test, the layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared in Example 1 and the layered double perovskite microcrystalline material (Cs4CdBi2Cl 12 ) prepared in the comparative example were analyzed by scanning electron microscopy (SEM), and the results are shown in a and b of Figure 4 respectively. It can be seen from Figure 4 that the morphology of the microcrystals has not changed significantly, and the prepared layered double perovskite microcrystals have strong stability and are suitable for photocatalytic CO2 reduction.

[0049] In summary, the present invention discloses a preparation method of a layered double perovskite microcrystalline material, mainly using CsCl, CuCl2, CdCl2, BiCl3, by adding hydrochloric acid to dissolve the raw materials and adding absolute ethanol for cleaning. The preparation method of the present invention is simple, easy to operate, has low requirements for equipment, has the advantages of low cost and low energy consumption, and is suitable for large-scale production; in addition, the layered double perovskite microcrystalline material (Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 ) prepared by the present invention has the characteristics of stability and high selectivity of photocatalytic products under visible light, and has good application prospects in photocatalytic CO2 reduction.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. Preparation method of layered double perovskite microcrystalline material, characterized in that, The preparation method includes the following steps: (1) Add cadmium chloride, copper chloride, and bismuth chloride into hydrochloric acid, stir to dissolve them until the solution becomes clear, and prepare a precursor solution. (2) Add cesium chloride into the precursor solution prepared in step (1), heat and stir, and fully react to obtain a reaction mixture. (3) Centrifuge the reaction mixture obtained in step (2) to remove the supernatant, and repeatedly centrifuge and wash with absolute ethanol to obtain a sample precipitate. After vacuum drying, the layered double perovskite microcrystalline material can be obtained.

2. The preparation method according to claim 1, wherein In step (1), the molar volume ratio of cadmium chloride, copper chloride, bismuth chloride, and hydrochloric acid solution is 0.8:0.2:2:10; mmol:mmol:mmol:ml, and the stirring time is 8 - 10 min.

3. The preparation method according to claim 1, wherein In step (2), the molar volume ratio of cesium chloride to the mixed solution prepared in step (1) is 4:10; mmol:ml.

4. The preparation method according to claim 1, characterized in that, In step (2), the heating temperature is 60 °C, and the reaction time is 5 - 8 min.

5. The preparation method according to claim 1, wherein In step (3), the rotation speed of the centrifugation is 4000 - 5000 rpm, and the centrifugation time is 5 - 8 min.

6. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the vacuum drying is 40 - 60 °C, and the time is 12 - 24 h.

7. The layered double perovskite microcrystalline material prepared by the preparation method according to any one of claims 1 to 6, and the chemical formula of the layered double perovskite microcrystalline material is Cs4Cd 0.8 Cu 0.2 Bi2Cl 12 .

8. The application of the layered double perovskite microcrystalline material according to claim 7 in photocatalytic CO2 reduction.

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