Composite material based on cesium-lead-bromine perovskite / tin disulfide Z-type heterojunction and preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic materials and new energy, and discloses a composite material based on a cesium-lead-bromine perovskite / tin disulfide Z-type heterojunction and a preparation method and application thereof, perovskite quantum dots are fully and stably loaded on the surface of a tin disulfide nanosheet through interface interaction, a Z-type heterojunction structure is formed, and the composite material is prepared. And centrifugally collecting a solid product, and drying to obtain the final cesium-lead-bromine perovskite / tin disulfide Z-type heterojunction composite catalyst. The preparation method can overcome the defects in the prior art, can obtain a novel photocatalytic material which efficiently utilizes visible light, realizes efficient charge separation and retains strong oxidation-reduction capacity, and can be used in the fields of photocatalytic carbon dioxide reduction, new energy and the like.

Description

Technical Field

[0001] This invention belongs to the fields of photocatalytic materials technology and new energy technology, and relates to a composite material for photocatalytic reduction of carbon dioxide (CO2) to prepare carbon-based fuels (such as carbon monoxide, methane, methanol, etc.), its preparation method and application. Specifically, it is a composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction, its preparation method and application. Background Technology

[0002] Photocatalytic carbon dioxide reduction technology is of great strategic significance for solving the energy crisis and the greenhouse effect. Utilizing solar energy to directly convert the greenhouse gas carbon dioxide into renewable fuels such as methane and carbon monoxide not only achieves the recycling of carbon resources and turns waste into treasure, but also constructs a zero-carbon or carbon-negative energy conversion pathway. Traditional semiconductors (such as TiO2) have wide band gaps and can only utilize ultraviolet light, resulting in low solar energy utilization. Single catalysts exhibit easy recombination of photogenerated electron-hole pairs, leading to low quantum efficiency. While common type II heterojunctions can separate charges, they sacrifice the redox ability of photogenerated carriers, thus limiting catalytic activity.

[0003] While perovskite CsPbBr3 exhibits excellent photoelectric properties, it suffers from poor stability and easy charge recombination. Therefore, it is crucial to develop a novel photocatalytic material that can efficiently utilize visible light, achieve efficient charge separation, and retain strong redox capabilities. Summary of the Invention

[0004] To address the problems existing in the prior art, the main objective of this invention is to propose a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction, its preparation method, and its application. This invention aims to overcome the bottlenecks of low photogenerated charge separation efficiency and weak redox capability in traditional technologies by designing a highly efficient Z-type heterojunction photocatalyst, thus providing a key material basis for achieving solar-driven artificial photosynthesis and carbon neutrality.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction includes the following steps: Preparation of lead-containing precursor solution: Hydrobromic acid, reducing agent and lead source compound are mixed and heated and stirred at 145-155℃ until the lead source compound is completely dissolved to obtain lead-containing precursor solution; Synthesis of cesium lead bromide perovskite: A cesium source compound is added to the lead-containing precursor solution, and the reaction is continuously stirred at 145-155℃ to generate cesium lead bromide perovskite crystals. In-situ composite: Tin disulfide nanomaterials were added to the reaction system for synthesizing cesium lead bromide perovskite, and the composite reaction was carried out by continuous stirring at 145-155℃. Product post-processing: The in-situ composite mixture was quenched and cooled, the solid products were separated and washed, and then vacuum dried to obtain the composite material based on the Z-type heterojunction of cesium lead bromide perovskite / tin disulfide.

[0006] Preferably, the reducing agent is at least one of hypophosphorous acid and phosphorous acid; the lead source compound is at least one of lead oxide and lead bromide.

[0007] Preferably, when preparing the lead-containing precursor solution, the concentration of hydrobromic acid is 45wt%-60wt%, the amount of the reducing agent is 10%-13% of the volume of hydrobromic acid, and the amount of the lead source compound is 1%-5% of the molar amount of hydrobromic acid.

[0008] Preferably, cesium bromide is used as the cesium source compound. When synthesizing cesium lead bromide perovskite, the molar ratio of cesium bromide to the lead source compound used in preparing the lead-containing precursor solution is (0.5~2.5):(0.5~1.5); the stirring reaction rate is 645-655 rpm and the time is 10~60 minutes.

[0009] Preferably, the tin disulfide nanomaterial adopts a two-dimensional nanosheet structure of tin disulfide; when performing in-situ composite, the amount of tin disulfide added is (0.2-5):1 based on its mass ratio with the theoretically generated cesium lead bromide perovskite; the stirring reaction rate is 645-655 rpm, and the time is 0.5-2 hours.

[0010] Preferably, during the post-processing of the product, quenching and cooling are performed by an ice-water bath or a 0°C ethanol bath, so that the mixed system obtained by in-situ composite is cooled to below room temperature within 5 minutes.

[0011] The present invention also provides a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction, which is prepared by the preparation method described above.

[0012] Preferably, in this composite material, cesium lead bromide perovskite nanocrystals are attached to the surface of tin disulfide nanosheets, forming a heterojunction interface between the cesium lead bromide perovskite nanocrystals and the tin disulfide nanosheets.

[0013] The present invention also provides the application of the composite material based on the cesium lead bromide perovskite / tin disulfide Z-type heterojunction as described above, which is used for photocatalytic reduction of carbon dioxide.

[0014] Preferably, the products of photocatalytic reduction of carbon dioxide include at least one of carbon monoxide and methane.

[0015] The beneficial effects of this invention are as follows: This invention relates to a method for preparing a Z-shaped heterojunction based on cesium lead bromide perovskite / tin disulfide. The method involves sequentially preparing a lead-containing precursor, synthesizing cesium lead bromide perovskite, and in-situ composite with tin disulfide nanomaterials in a unified reaction system at 145-155℃. This allows tin disulfide and nascent cesium lead bromide perovskite crystals to self-assemble into a tightly bonded Z-shaped heterojunction. Furthermore, this invention leverages the band structure characteristics of both materials (SnS2 has a more negative valence and conduction band than CsPbBr3) to achieve directional recombination of CsPbBr3 conduction band electrons and SnS2 valence band holes after illumination. This efficiently retains the strong reducing electrons in the SnS2 conduction band and the strong oxidizing holes in the CsPbBr3 valence band, significantly suppressing electron-hole pair recombination and improving quantum efficiency. Simultaneously, this invention fully utilizes the light absorption advantages of the cesium lead bromide perovskite crystal and tin disulfide nanomaterials, taking advantage of the excellent visible light absorption of cesium lead bromide perovskite and the extension of tin disulfide to approximately [missing information - likely related to light absorption]. The 600nm absorption edge allows the composite material to cover a wider visible light region, breaking through the limitation of traditional TiO2 semiconductors that can only utilize ultraviolet light. This significantly expands the light absorption range to improve the utilization rate of sunlight and provides an energy basis for improving the photocatalytic CO2 reduction efficiency. Moreover, the preparation process adopts a one-step aqueous phase synthesis approach, and the post-processing only requires quenching cooling, separation washing, and vacuum drying. The process is simple and the conditions are mild, reducing the difficulty and cost of production, making it easy to scale up production and showing significant prospects for industrial application. Based on the above advantages, when the composite material is used to catalyze CO2 reduction under simulated sunlight, the yield of target products (such as CO and CH4) is significantly higher than that of single cesium lead bromide perovskite, tin disulfide, and physical mixtures of the two. In addition, the target product selectivity is good, effectively solving the core performance bottleneck of existing photocatalytic materials and providing key material and technical support for carbon resource recycling and carbon neutrality. Attached Figure Description

[0016] Figure 1 This is a graph showing the production yield of the composite material obtained in Example 1 of the present invention; Figure 2 This is a graph showing the production yield of the composite material obtained in Example 2 of the present invention; Figure 3 This is a graph showing the yield of the composite material obtained in Example 3 of the present invention; Figure 4 This is a graph showing the yield of the composite material obtained in Example 4 of the present invention; Figure 5 This is a graph showing the yield of the composite material obtained in Example 5 of the present invention; Figure 6 This is a microscopic morphology diagram of the composite material obtained in Example 1 of the present invention; Figure 7 The image shows the XRD pattern of the composite material obtained in Example 1 of this invention. Figure 8 This is a graph showing the production yield of the composite material obtained in Comparative Example 1 of the present invention; Figure 9 This is a graph showing the production yield of the composite material obtained in Comparative Example 2 of the present invention; Figure 10 This is a microscopic morphology diagram of the composite material obtained in Comparative Example 2 of the present invention. Detailed Implementation

[0017] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The present invention relates to a method for preparing a cesium lead bromide perovskite / tin disulfide Z-type heterostructure composite material. In an acidic hydrothermal environment, CsPbBr3 is first synthesized. Then, utilizing the high temperature and chemical environment of the reaction system, subsequently added SnS2 nanosheets undergo in-situ self-assembly with the nascent CsPbBr3 crystals, forming a tightly bonded heterostructure. Specifically, the CsPbBr3 quantum dots and SnS2 nanosheets form a direct Z-type heterostructure structure through interfacial interactions.

[0019] The preparation method of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction of the present invention specifically includes the following steps: Step (1) Preparation of lead-containing precursor solution: Hydrobromic acid, reducing agent, and lead source compound are mixed and heated and stirred at 150±5℃ until the lead source is completely dissolved to obtain a lead-containing precursor solution; wherein, the reducing agent is at least one of hypophosphorous acid and phosphorous acid; the lead source compound is at least one of lead oxide (PbO) and lead bromide (PbBr2). The concentration of hydrobromic acid is 45wt%-60wt%, the amount of reducing agent is 10%-13% of the volume of hydrobromic acid, and the amount of lead source compound is 1%-5% of the molar amount of hydrobromic acid.

[0020] Step (2) Synthesis of cesium lead bromide perovskite: A cesium source compound is added to the lead-containing precursor solution obtained in step (1), and the reaction is continuously stirred at 150±℃ to generate cesium lead bromide perovskite crystals; wherein, the cesium source compound is cesium bromide (CsBr), and the molar ratio of cesium bromide to the lead source compound used in preparing the lead-containing precursor solution is (0.5~2.5):(0.5~1.5); the stirring rate is 650±5 rpm, and the time is 10~60 minutes.

[0021] Step (3) In-situ composite: Add tin disulfide nanomaterials to the reaction system obtained in step (2) and carry out the composite reaction by continuous stirring at 150±5℃; wherein, the tin disulfide nanomaterials adopt a two-dimensional nanosheet structure of tin disulfide; the amount of tin disulfide added is (0.2-5):1 according to its mass ratio with the theoretically generated cesium lead bromide perovskite (CsPbBr3); the stirring rate is 650±5 rpm and the time is 0.5~2 hours.

[0022] Step (4) Product post-processing: The mixture obtained in step (3) is quenched and cooled, centrifuged and washed, and then vacuum dried to obtain the cesium lead bromide perovskite / tin disulfide Z-type heterojunction composite material. Quenching and cooling can be performed using an ice-water bath or a 0°C ethanol bath to cool the in-situ composite mixture to below room temperature within 5 minutes. The collected solid product is washed 2-3 times alternately with deionized water and anhydrous ethanol. The vacuum drying temperature is 60±5°C, and the drying time is 18-30 hours.

[0023] In the above-described scheme of this invention, the valence band of SnS2 (-6.5 eV) is more negative than that of CsPbBr3 (-5.6 eV), and its conduction band (-4.2 eV) is more negative than that of CsPbBr3 (-3.4 eV). This band arrangement satisfies the thermodynamic conditions for constructing a direct Z-type heterojunction. After illumination, electrons in the conduction band of CsPbBr3 recombine with holes in the valence band of SnS2 under the influence of the built-in electric field. This retains strongly reducing electrons in the conduction band of SnS2 and strongly oxidizing holes in the valence band of CsPbBr3, achieving both charge separation and maximizing the preservation of the high redox capability of the charge carriers. The Z-type heterojunction mechanism and the tight interfacial contact between the two-dimensional nanosheets and zero-dimensional quantum dots provide an efficient channel for the migration of photogenerated charge carriers, significantly suppressing electron-hole recombination and improving quantum efficiency. CsPbBr3 absorbs visible light, while the absorption edge of SnS2 extends to approximately 600 nm. The combination of these two materials achieves broad-spectrum absorption in the visible light region, significantly improving solar energy conversion efficiency. The preparation method is simple, operates under mild conditions, requires no expensive equipment, and is easily scalable, showing broad prospects for industrial application. Experiments show that this composite material, under simulated sunlight, catalyzes CO2 reduction with significantly higher yields (e.g., CO, CH4) than individual CsPbBr3, SnS2, or their physical mixtures, and exhibits good selectivity for the target products.

[0024] As a preferred embodiment of the above-described scheme of the present invention, hypophosphite is used as the reducing agent, lead oxide (PbO) is used as the lead source compound, and cesium bromide is used as the cesium source compound.

[0025] In the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction prepared by the present invention, cesium lead bromide perovskite nanocrystals are uniformly attached to the surface of tin disulfide nanosheets, and the two form a tight heterojunction interface.

[0026] The composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction prepared by this invention can be used in photocatalytic reduction of carbon dioxide. The products of photocatalytic reduction of carbon dioxide include at least one of carbon monoxide and methane.

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0028] Example 1 This embodiment describes a method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction, including the following steps: Step (1) Preparation of lead-containing precursor solution: In a reaction vessel, add 4 mL of 47 wt% hydrobromic acid, 0.5 mL of hypophosphoric acid, and 0.5 mmol of lead oxide (PbO) in sequence. Stir the mixture magnetically at 150±5℃ until the lead oxide powder is completely dissolved to obtain a clear lead-containing precursor solution.

[0029] Step (2) Synthesis of cesium lead bromide perovskite: 0.6 mmol of cesium bromide was added to the lead-containing precursor solution obtained in step (1), and the mixture was stirred continuously at 650±5 rpm for 30 minutes at 150±5℃ to generate cesium lead bromide perovskite nuclei in the reaction system.

[0030] Step (3) In-situ composite: Add 10 mg of two-dimensional tin disulfide nanosheets to the reaction solution obtained in step (2), and maintain the temperature at 150±5℃ and the stirring state (i.e., stirring at a stirring rate of 650±5 rpm) for 1 hour.

[0031] Step (4) Product post-processing: The reaction system obtained in step (3) is quickly transferred to an ice-water bath for quenching and cooling, and then the solid product is collected by centrifugation. The solid product is washed twice with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60±5℃ for 24 hours to obtain the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction.

[0032] The morphology of the composite material based on the cesium lead bromide perovskite / tin disulfide Z-type heterostructure obtained in this embodiment is as follows: Figure 6 As shown, cesium lead bromide is uniformly grown on the surface of tin disulfide. XRD analysis was performed on the composite material obtained in this embodiment based on the cesium lead bromide perovskite / tin disulfide Z-type heterostructure, and the results are as follows. Figure 7 As shown, the recombination process did not damage the crystal structure.

[0033] The photocatalytic CO2 reduction performance of the obtained composite material was tested. After irradiation under simulated sunlight for 4 hours, the product yield was as follows: Figure 1 As shown, Figure 1 The analysis results are shown in Table 1: Table 1

[0034] As shown in Table 1, the CO yield reached 82.73 μmol g. -1 h -1 The CH4 yield reached 126.82 μmol g. -1 h -1 .

[0035] Example 2 The preparation method of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction in this embodiment is the same as that in Example 1, wherein: in step (1), the amount of hydrobromic acid used is 6 mL, the concentration of hydrobromic acid is 60 wt%, and the amount of lead oxide used is 1 mmol. In step (2), the amount of cesium bromide added is 1.5 mmol, and the reaction time is 45 minutes. In step (3), the amount of tin disulfide nanosheets added is 80 mg, and the composite reaction time is 1.5 hours. The remaining processes and conditions are the same as in Example 1 unless otherwise specified.

[0036] The composite material based on the cesium lead bromide perovskite / tin disulfide Z-type heterojunction obtained in this embodiment was tested, and the product yield was as follows: Figure 2 As shown, Figure 2 The analysis results are shown in Table 2: Table 2

[0037] As shown in Table 2, the CO yield from photocatalytic CO2 reduction reached 63.24 μmol g. -1 h -1 The CH4 yield reached 107.89 μmol g. -1 h -1 .

[0038] Example 3 The preparation method of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction in this embodiment is the same as that in Example 1, wherein: in step (3), the amount of tin disulfide added is 50 mg, which is 1:1 according to its mass ratio with the theoretically generated cesium lead bromide perovskite. The remaining processes and conditions are the same as in Example 1 unless otherwise specified.

[0039] The composite material based on the cesium lead bromide perovskite / tin disulfide Z-type heterojunction obtained in this embodiment was tested, and the product yield was as follows: Figure 3 As shown, Figure 3 The analysis results are shown in Table 3: Table 3

[0040] Table 3 shows that the CO yield from photocatalytic CO2 reduction reached 75.59 μmol g. -1 h -1 The CH4 yield reached 63.08 μmol g. -1 h -1 .

[0041] Example 4 The preparation method of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction in this embodiment is the same as that in Example 1, wherein: in step (1), the amount of lead oxide, the lead source compound, is 1.5 mmol, the amount of hydrobromic acid (concentration 47wt%) is 8 mL, and the amount of hypophosphoric acid is 0.8 mL. In step (2), the amount of cesium bromide, the cesium source compound, is 2.4 mmol (molar ratio with lead source is 1.6:1), and the reaction time is 50 minutes. In step (3), the amount of tin disulfide nanosheets is 150 mg (based on its mass ratio with the theoretically generated cesium lead bromide perovskite is 0.8:1), and the composite reaction time is 1.2 hours. In step (4), the vacuum drying time is 20 hours. The remaining processes and conditions, unless otherwise specified, are the same as in Example 1.

[0042] The photocatalytic CO2 reduction performance of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction obtained in this embodiment was tested. After irradiation under simulated sunlight for 4 hours, the product yield was as follows: Figure 4 As shown, Figure 4 The analysis results are shown in Table 4: Table 4

[0043] As shown in Table 4, the CO yield reached 38.70 μmol g. -1 h -1 The CH4 yield reached 14.09 μmol g. -1 h -1 Compared with Comparative Examples 1 and 2, the composite material obtained in this embodiment exhibits significantly improved photocatalytic activity.

[0044] Example 5 The preparation method of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterostructure in this embodiment is the same as that in Example 1, wherein: in step (1), the amount of lead oxide, the lead source compound, is 0.8 mmol, the amount of hydrobromic acid (concentration 60wt%) is 5 mL, and the amount of hypophosphoric acid is 0.6 mL. In step (2), the amount of cesium bromide, the cesium source compound, is 1.0 mmol (molar ratio with lead source is 1.25:1), and the reaction time is 15 minutes. In step (3), the amount of tin disulfide nanosheets is 20 mg (approximately 0.25:1 based on its mass ratio with the theoretically generated cesium lead bromide perovskite), and the composite reaction time is 0.5 hours. In step (4), quenching and cooling are performed using a 0℃ ethanol bath, and the vacuum drying time is 30 hours. The remaining processes and conditions, unless otherwise specified, are the same as in Example 1.

[0045] The photocatalytic CO2 reduction performance of the composite material based on cesium lead bromide perovskite / tin disulfide Z-type heterojunction obtained in this embodiment was tested. After irradiation under simulated sunlight for 4 hours, the product yield was as follows: Figure 5 As shown, Figure 5 The analysis results are shown in Table 5: Table 5

[0046] As shown in Table 5, the CO yield reached 38.80 μmol g. -1 h -1 The CH4 yield reached 33.68 μmol g. -1 h -1 Compared with Comparative Examples 1 and 2, the composite material obtained in this embodiment exhibits significantly improved photocatalytic activity.

[0047] Comparative Example 1 A method for preparing pure-phase cesium lead bromide perovskite includes only steps (1), (2) and (4) of Example 1, without performing the composite process in step (3).

[0048] The photocatalytic CO2 reduction performance of the pure phase CsPbBr3 obtained in this comparative example was tested, and the product yield was as follows: Figure 8 As shown, Figure 8 The analysis results are shown in Table 6: Table 6

[0049] Table 3 shows that, under the same conditions, the CO yield is 11.5 μmol g. -1 h -1 The yield of CH4 was 0.7 μmol g. -1 h -1Although pure-phase CsPbBr3 has high carrier mobility, its photogenerated electrons and holes easily recombine before reaching the surface to participate in the reaction, resulting in low photocatalytic CO2 reduction efficiency.

[0050] Comparative Example 2 A method for preparing a physical mixture of cesium lead bromide perovskite and tin disulfide involves physically grinding and mixing pure phase CsPbBr3 prepared according to Comparative Example 1 and pure phase SnS2 at the same mass ratio as in Example 1.

[0051] The photocatalytic CO2 reduction performance of this physical mixture was tested, and the product yield was as follows: Figure 9 As shown, Figure 9 The analysis results are shown in Table 7: Table 7

[0052] Table 3 shows that, under the same conditions, no CO or CH4 was detected, and the photocatalytic CO2 reduction results are as follows: Figure 9 The SEM scan results are shown in Table 7. Figure 10 ,from Figure 10 As can be seen from the SEM scan, when cesium lead bromide perovskite is physically combined with tin disulfide, the composite material is bonded by physical action only. It has a small specific surface area and a slow charge transport rate. Therefore, CO and CH4 were not detected in this comparative example.

[0053] This invention utilizes a hydrohalic acid method to first synthesize CsPbBr3 in an acidic hydrothermal environment. Then, leveraging the high temperature and chemical environment of the reaction system, subsequently added SnS2 nanosheets undergo in-situ self-assembly with the nascent CsPbBr3 crystals, forming a tightly bonded Z-shaped heterojunction. This invention overcomes the shortcomings of existing technologies, yielding a novel photocatalytic material that efficiently utilizes visible light, achieves efficient charge separation, and retains strong redox capabilities. It can be used in photocatalytic carbon dioxide reduction, new energy fields, and other areas.

[0054] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0055] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction, characterized in that, The process includes the following: Preparation of lead-containing precursor solution: Hydrobromic acid, reducing agent and lead source compound are mixed and heated and stirred at 145-155℃ until the lead source compound is completely dissolved to obtain lead-containing precursor solution; Synthesis of cesium lead bromide perovskite: A cesium source compound is added to the lead-containing precursor solution, and the reaction is continuously stirred at 145-155℃ to generate cesium lead bromide perovskite crystals. In-situ composite: Tin disulfide nanomaterials were added to the reaction system for synthesizing cesium lead bromide perovskite, and the composite reaction was carried out by continuous stirring at 145-155℃. Product post-processing: The in-situ composite mixture was quenched and cooled, the solid products were separated and washed, and then vacuum dried to obtain the composite material based on the Z-type heterojunction of cesium lead bromide perovskite / tin disulfide.

2. The method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 1, characterized in that, The reducing agent is at least one of hypophosphorous acid and phosphorous acid; the lead source compound is at least one of lead oxide and lead bromide.

3. A method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 1 or 2, characterized in that, When preparing the lead-containing precursor solution, the concentration of hydrobromic acid is 45wt%-60wt%, the amount of reducing agent is 10%-13% of the volume of hydrobromic acid, and the amount of lead source compound is 1%-5% of the molar amount of hydrobromic acid.

4. The method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 1, characterized in that, Cesium bromide was used as the cesium source compound. When synthesizing cesium lead bromide perovskite, the molar ratio of cesium bromide to the lead source compound used in preparing the lead-containing precursor solution was (0.5~2.5):(0.5~1.5); the stirring rate was 645-655 rpm and the time was 10~60 minutes.

5. The method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 1, characterized in that, Tin disulfide nanomaterials employ a two-dimensional nanosheet structure. During in-situ composite formation, the amount of tin disulfide added is calculated as (0.2-5):1 based on its mass ratio with the theoretically generated cesium lead bromide perovskite. The stirring reaction rate is 645-655 rpm, and the reaction time is 0.5-2 hours.

6. The method for preparing a composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 1, characterized in that, During the post-processing of the product, quenching and cooling are performed using an ice-water bath or a 0°C ethanol bath to cool the in-situ composite mixture to below room temperature within 5 minutes.

7. A composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction, characterized in that, The composite material is prepared by any one of the preparation methods of claims 1-6.

8. A composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 7, characterized in that, In this composite material, cesium lead bromide perovskite nanocrystals are attached to the surface of tin disulfide nanosheets, forming a heterojunction interface between the cesium lead bromide perovskite nanocrystals and the tin disulfide nanosheets.

9. The application of the composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction as described in claim 7 or 8, characterized in that, This composite material is used for photocatalytic reduction of carbon dioxide.

10. The application of the composite material based on a cesium lead bromide perovskite / tin disulfide Z-type heterojunction according to claim 9, characterized in that, The products of photocatalytic reduction of carbon dioxide include at least one of carbon monoxide and methane.

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