A Cs3Bi2Br9 / BiOCl composite material, its preparation method and application

Abstract

This invention provides a Cs3Bi2Br9 / BiOCl composite material, its preparation method, and its applications, relating to the field of photocatalytic materials technology. First, BiOCl is prepared via a solvothermal method. Then, BiOCl is added to a CsBr-BiBr3 dimethyl sulfoxide solution and stirred to disperse it, followed by drying in a drying oven. Isopropanol (IPA) is added dropwise to the resulting solid. After the reaction is complete, the sample is collected by centrifugation, washed with ethanol, centrifuged again, and dried in a drying oven to obtain the Cs3Bi2Br9 / BiOCl composite material. The preparation method of the Cs3Bi2Br9 / BiOCl composite material of this application is simple, yields high-quality materials, and is low-cost. The prepared Cs3Bi2Br9 / BiOCl composite material exhibits full-spectrum photocatalytic activity and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, and in particular to a Cs3Bi2Br9 / BiOCl composite material, its preparation method, and its application. Background Technology

[0002] Against the backdrop of increasingly severe global environmental problems, the emission of the greenhouse gas carbon dioxide has become one of the most pressing issues to address. Photocatalytic materials refer to a class of semiconductor catalyst materials that undergo photochemical reactions under the influence of light. Under sunlight, photocatalytic materials can convert carbon dioxide into renewable energy for subsequent use, and have become a promising green technology for solving environmental problems in recent years.

[0003] Bismuth oxychloride (BiOCl) is a non-toxic and corrosion-resistant photocatalytic material. Its unique layered sandwich structure, consisting of a double chloride ion layer and [Bi₂O₂], is highly effective. 2+ The alternating layers, with an electrostatic field in between, facilitate the migration and separation of electrons and holes (eh), thus attracting widespread attention in the field of photocatalytic carbon dioxide reduction.

[0004] However, the applicant has discovered that the prior art has at least the following technical problems:

[0005] Bismuth oxychloride photocatalysts have a relatively wide band gap of approximately 3.6 eV, resulting in poor performance in photocatalytic carbon dioxide reduction across the entire spectrum. Therefore, developing a bismuth oxychloride-based heterojunction photocatalyst that exhibits excellent carbon dioxide reduction performance across the entire spectrum is currently a challenging and valuable endeavor for those skilled in the art. Summary of the Invention

[0006] The purpose of this application is to provide a Cs3Bi2Br9 / BiOCl composite material, its preparation method and application, aiming to solve the technical problems of poor full-spectrum response of bismuth oxychloride photocatalyst and low photocatalytic carbon dioxide reduction efficiency in the prior art.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, this application provides a method for preparing a Cs3Bi2Br9 / BiOCl composite material, comprising the following steps:

[0009] Step S1: Preparation of BiOCl: Bismuth nitrate pentahydrate and acetic acid are mixed in a certain proportion and stirred until they are evenly mixed and dissolved. Then methanol and D(+)-glucosamine hydrochloride are added. The mixed solution is transferred to an autoclave for reaction. After cooling to room temperature, the sample is collected by centrifugation, washed with water and ethanol in turn, and then dried in a drying oven to obtain BiOCl.

[0010] Step S2: Preparation of CsBr-BiBr3 solution: Cesium bromide and bismuth bromide are added to dimethyl sulfoxide and stirred to dissolve them, thus obtaining CsBr-BiBr3 solution;

[0011] Step S3: Add the BiOCl obtained in step S1 to the CsBr-BiBr3 solution obtained in step S2 in a certain proportion, stir to mix evenly, and then put the mixed solution into a drying oven to dry.

[0012] Step S4: Take the powder obtained in step S3, add isopropanol solution dropwise to the powder under stirring conditions, react for 0.5 to 2 hours after the addition is complete, centrifuge the obtained solution to collect the sample, wash the sample with ethanol, centrifuge the washed sample to collect it, and dry it in a drying oven to obtain Cs3Bi2Br9 / BiOCl composite material.

[0013] In one or more embodiments of this application, in the step S1 of preparing BiOCl, the mass ratio of bismuth nitrate pentahydrate to D(+)-glucosamine hydrochloride is 5.0:1.5, the amount of acetic acid is 10-50 ml, the amount of methanol is 100-140 ml, and the temperature of the thermal reaction in the autoclave is 160-180°C.

[0014] In one or more embodiments of this application, in step S2, the mass ratio of cesium bromide to bismuth bromide is 0.096:0.1345, and the amount of dimethyl sulfoxide is 5-15 ml.

[0015] In one or more embodiments of this application, in step S3, the mass amount of BiOCl is 0.15 to 0.35 g, the amount of CsBr-BiBr3 solution is 1 ml to 4 ml, the stirring time is 30 to 90 minutes, and the drying temperature in the drying oven is 50 to 90°C.

[0016] In one or more embodiments of this application, in step S4, the amount of isopropanol solution used is 3 ml to 7 ml, the stirring time is 30 to 90 minutes, and the drying temperature in the drying oven is 50 to 90°C.

[0017] Secondly, this application provides a Cs3Bi2Br9 / BiOCl composite material, which is prepared by the preparation method described in the first aspect.

[0018] Thirdly, this application also provides the application of the Cs3Bi2Br9 / BiOCl composite material described in the second aspect in the photocatalytic reduction of carbon dioxide.

[0019] Based on the above technical solutions, the Cs3Bi2Br9 / BiOCl composite material of the present invention, its preparation method, and its application have at least the following technical effects:

[0020] This application first prepares BiOCl via a solvothermal method, then adds BiOCl to a CsBr-BiBr3 dimethyl sulfoxide solution and stirs to disperse it, drying it in a drying oven. Isopropanol (IPA) is added dropwise to the resulting solid, and after the reaction is complete, the sample is collected by centrifugation. The sample is washed with ethanol, centrifuged again, and dried in a drying oven to obtain the Cs3Bi2Br9 / BiOCl composite material. The preparation method of the Cs3Bi2Br9 / BiOCl composite material of this application is simple, and the prepared material has high yield and low cost. The Cs3Bi2Br9 / BiOCl composite material prepared by the method of this application is a photocatalytic material with an S-shaped heterostructure and a uniform distribution of cesium, bismuth, bromine, oxygen, and chlorine elements. Cs3Bi2Br9 and BiOCl possess suitable band structures. After forming a heterojunction, the difference in Fermi levels spontaneously creates an internal electric field between the materials, which is beneficial for carrier migration. Moreover, the inactive carriers in the S-type heterojunction tend to recombine at the heterojunction interface, preserving the high redox capability of the composite material. Compared to single Cs3Bi2Br9 or BiOCl, the photocatalytic ability of the Cs3Bi2Br9 composite material is greatly improved. The prepared Cs3Bi2Br9 composite material can successfully reduce carbon dioxide to carbon monoxide and methane gas under broad-spectrum light, exhibiting full-spectrum photocatalytic capability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is the XRD pattern of the Cs3Bi2Br9 / BiOCl composite material prepared in Example 5.

[0023] Figure 2 The images include scanning electron microscope (SEM) images of the BiOCl material prepared in Example 1, the Cs3Bi2Br9 material prepared in Example 2, and the Cs3Bi2Br9 / BiOCl materials with different ratios prepared in Examples 3-5, as well as transmission electron microscope (TEM) images and elemental distribution maps of the Cs3Bi2Br9 / BiOCl material prepared in Example 4. Figure 2 (a) is a scanning electron microscope image of the BiOCl material in Example 1; Figure 2 (b) is a scanning electron microscope image of the Cs3Bi2Br9 material obtained in Example 2; Figure 2 (c) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl material obtained in Example 3; Figure 2 (d) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4;

[0024] Figure 2 (e) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 5. Figure 2 (f) is a low-magnification transmission electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4; Figure 2 (g) to Figure 2 (k) is the elemental distribution diagram of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4. Figure 2 (l) is a high-resolution transmission electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4.

[0025] Figure 3 Photocatalytic carbon dioxide reduction performance of the BiOCl material prepared in Example 1, the Cs3Bi2Br9 material prepared in Example 2, and the Cs3Bi2Br9 / BiOCl materials with different ratios prepared in Examples 3-5.

[0026] Figure 4 In-situ X-ray photoelectron spectroscopy and electron spin resonance spectroscopy of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0030] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0032] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0033] Raw materials and their sources

[0034] Bismuth nitrate pentahydrate: Bi(NO3)3·5H2O, analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0035] Acetic acid: CH3COOH, analytical grade, Chengdu Kelong Chemical Co., Ltd.

[0036] Methanol: CH3OH, analytical grade, Chengdu Kelong Chemical Co., Ltd.

[0037] D(+)-Glucosamine hydrochloride: C6H 13 NO5·HCl, analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0038] Cesium bromide: CsBr, analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0039] Bismuth bromide: BiBr3, analytical grade, Shanghai Mairui Biochemical Technology Co., Ltd.

[0040] Dimethyl sulfoxide (C2H6OS), analytical grade, Chengdu Kelong Chemical Co., Ltd.

[0041] Isopropanol: C3H8O, analytical grade, Chengdu Kelong Chemical Co., Ltd.

[0042] This application provides a method for preparing Cs3Bi2Br9 / BiOCl composite material, the specific steps of which are as follows:

[0043] Step S1: Preparation of BiOCl: Mix 4.852g of bismuth nitrate pentahydrate and 10-50ml of acetic acid in a certain proportion and stir until they are evenly mixed and dissolved. Then add 100-140ml of methanol and 1.510g of D(+)-glucosamine hydrochloride. Transfer the mixed solution to an autoclave for reaction. The temperature of the thermal reaction is 160-180℃. After cooling to room temperature, centrifuge to collect the sample, wash with water and ethanol in sequence, and then dry in a drying oven to obtain BiOCl.

[0044] Step S2: Prepare CsBr-BiBr3 solution by adding 0.096g of cesium bromide and 0.1345g of bismuth bromide to 5-15ml of dimethyl sulfoxide and stirring to dissolve them, thus obtaining CsBr-BiBr3 solution.

[0045] Step S3: Add the BiOCl obtained in step S1 to the CsBr-BiBr3 solution obtained in step S2 in a certain proportion, stir to mix evenly, and then put the mixed solution into a drying oven to dry; the mass of BiOCl is 0.15~0.35g, the volume of CsBr-BiBr3 solution is 1ml~4ml, the stirring time is 30-90 minutes, and the drying temperature in the drying oven is 50-90℃.

[0046] Step S4: Add 3-7 ml of isopropanol dropwise to the powder obtained in step S3 while stirring. After the addition is complete, react for 0.5-2 hours. Centrifuge the resulting solution to collect the sample. Wash the sample with ethanol, centrifuge the washed sample again, and dry it in a drying oven to obtain the Cs3Bi2Br9 / BiOCl composite material. Preferably, the centrifuge speed used for centrifuging is 13000 rpm, the stirring time is 30-90 minutes, and the drying temperature in the drying oven is 50-90℃.

[0047] The technical solution of this application will be described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] This embodiment 1 provides a method for preparing BiOCl material, including the following steps:

[0050] S1: Add 4.852 g of bismuth nitrate pentahydrate to 30 mL of acetic acid and stir until completely dissolved. Then add 120 mL of methanol and 1.510 g of D(+)-glucosamine hydrochloride to the mixed solution and continue magnetic stirring for 1 hour.

[0051] S2: Transfer the solution obtained in step S1 to a Teflon-lined stainless steel autoclave; react solvothermically at 180°C for 5 hours;

[0052] S3: After the solution cools to room temperature, centrifuge to collect the sample, and wash the sample with deionized water at least three times. Centrifuge the washed sample again and dry it overnight at 70°C in a drying oven to obtain the prepared BiOCl material. The centrifuge used for centrifuging the sample was 13000 rpm.

[0053] Example 2

[0054] This embodiment 2 provides a method for preparing Cs3Bi2Br9 photocatalytic material, including the following steps:

[0055] S1: Add 0.384 g of CsBr and 0.538 g of BiBr3 to 10 mL of dimethyl sulfoxide and stir until homogeneous. Then slowly add the solution to 50 mL of isopropanol and react for 1 hour with magnetic stirring.

[0056] S2: The solution obtained in step S1 was centrifuged to collect the sample, washed with ethanol, and dried overnight at 70°C in a drying oven. The material prepared was Cs3Bi2Br9. The centrifuge used for centrifuging to collect the sample was 13,000 rpm.

[0057] Example 3

[0058] This embodiment 3 provides a method for preparing Cs3Bi2Br9 / BiOCl photocatalytic material, including the following steps:

[0059] S1: Add 0.25g of BiOCl to 2mL of CsBr-BiBr3 solution, stir for 1 hour at room temperature, and then dry the above system in a drying oven at 70℃.

[0060] The preparation method of BiOCl includes: adding 4.852 g of bismuth nitrate pentahydrate to 30 mL of acetic acid and stirring until completely dissolved. Then, adding 120 mL of methanol and 1.510 g of D(+)-glucosamine hydrochloride to the mixed solution, and then transferring the mixed solution to an autoclave for reaction. The reaction is carried out at 180 °C for 5 hours using a solvothermal method. After cooling to room temperature, the sample is collected by centrifugation, washed with water and ethanol, and then dried in a drying oven at 70 °C to obtain BiOCl. The preparation method of CsBr-BiBr3 solution includes: adding 0.096 g of cesium bromide and 0.1345 g of bismuth bromide to 10 mL of dimethyl sulfoxide and stirring until dissolved to obtain CsBr-BiBr3 solution.

[0061] S2: Transfer the powder obtained in step S1 to a beaker, and add 5 mL of isopropanol dropwise to the powder while stirring. After the addition is complete, react for 1 hour. Collect the resulting solution by centrifugation, wash the sample with ethanol, collect the washed sample by centrifugation, and dry it in a drying oven at 70℃ to obtain the Cs3Bi2Br9 / BiOCl composite material. The centrifuge used for centrifugation was 13000 rpm.

[0062] Example 4

[0063] This embodiment 4 provides a method for preparing Cs3Bi2Br9 / BiOCl photocatalytic material, including the following steps:

[0064] S1: Add 0.25g of BiOCl to 3mL of CsBr-BiBr3 solution, stir for 1 hour at room temperature, and then dry the above system in a drying oven at 70℃.

[0065] The preparation method of BiOCl includes: adding 4.852 g of bismuth nitrate pentahydrate to 30 mL of acetic acid and stirring until completely dissolved. Then, adding 120 mL of methanol and 1.510 g of D(+)-glucosamine hydrochloride to the mixed solution, and then transferring the mixed solution to an autoclave for reaction. The reaction is carried out at 180 °C for 5 hours using a solvothermal method. After cooling to room temperature, the sample is collected by centrifugation, washed with water and ethanol, and then dried in a drying oven at 70 °C to obtain BiOCl. The preparation method of CsBr-BiBr3 solution includes: adding 0.096 g of cesium bromide and 0.1345 g of bismuth bromide to 10 mL of dimethyl sulfoxide and stirring until dissolved to obtain CsBr-BiBr3 solution.

[0066] S2: Transfer the powder obtained in step S1 to a beaker, and add 5 mL of isopropanol dropwise to the powder while stirring. After the addition is complete, react for 1 hour. Collect the resulting solution by centrifugation, wash the sample with ethanol, collect the washed sample by centrifugation, and dry it in a drying oven at 70℃ to obtain the Cs3Bi2Br9 / BiOCl composite material. The centrifuge used for centrifugation was 13000 rpm.

[0067] Example 5

[0068] Example 5 provides a method for preparing Cs3Bi2Br9 / BiOCl photocatalytic material, including the following steps:

[0069] S1: Add 0.25g of BiOCl to 4mL of a mixed solution of CsBr-BiBr3, stir for 1 hour at room temperature, and then dry the above system in a drying oven at 70℃.

[0070] The preparation method of BiOCl includes: adding 4.852 g of bismuth nitrate pentahydrate to 30 mL of acetic acid and stirring until completely dissolved. Then, adding 120 mL of methanol and 1.510 g of D(+)-glucosamine hydrochloride to the mixed solution, and then transferring the mixed solution to an autoclave for reaction. The reaction is carried out at 180 °C for 5 hours using a solvothermal method. After cooling to room temperature, the sample is collected by centrifugation, washed with water and ethanol, and then dried in a drying oven at 70 °C to obtain BiOCl. The preparation method of CsBr-BiBr3 solution includes: adding 0.096 g of cesium bromide and 0.1345 g of bismuth bromide to 10 mL of dimethyl sulfoxide and stirring until dissolved to obtain CsBr-BiBr3 solution.

[0071] S2: Transfer the powder obtained in step S1 to a beaker, and add 5 mL of isopropanol dropwise to the powder while stirring. After the addition is complete, react for 1 hour. Collect the resulting solution by centrifugation, wash the sample with ethanol, collect the washed sample by centrifugation, and dry it in a drying oven at 70℃ to obtain the Cs3Bi2Br9 / BiOCl composite material. The centrifuge used for centrifugation was 13000 rpm.

[0072] Example 6

[0073] Example 6 provides an experiment on the photocatalytic reduction of carbon dioxide using the products prepared in Examples 1 to 5.

[0074] Specifically:

[0075] 10 mg of each product prepared in Examples 1, 2, 3, 4, and 5 were uniformly dispersed in a 25 mL beaker. The beaker was placed in the center of a 200 mL quartz reactor, and 50 μL of water was added dropwise to the edge of the reactor. The reactor was sealed, and high-purity CO2 was bubbled through it for 20 min to fill the reactor with CO2 gas. A photocatalytic CO2 reduction reaction was carried out under the conditions of a 300 W xenon lamp as the light source and an AM 1.5 G filter. The products were analyzed using gas chromatography.

[0076] See results Figures 1 to 3 As shown, Figures 1-3 Images are obtained for characterizing the BiOCl material prepared in Example 1, the Cs3Bi2Br9 material prepared in Example 2, and the Cs3Bi2Br9 / BiOCl materials prepared in Examples 3 to 5.

[0077] in:

[0078] Figure 1 This is the XRD pattern of the Cs3Bi2Br9 / BiOCl material prepared in Example 5. Figure 1 The XRD analysis results of the sample are shown. The XRD pattern reveals the crystal structure of the prepared material, indicating that the material contains BiOCl and Cs3Bi2Br9 substances and has good crystallinity.

[0079] Figure 2 These are scanning electron microscope (SEM) images of the BiOCl material prepared in Example 1, the Cs3Bi2Br9 material prepared in Example 2, the Cs3Bi2Br9 / BiOCl materials prepared in Examples 3 to 5, and the transmission electron microscopy (TEM) and surface distribution images of the Cs3Bi2Br9 / BiOCl material prepared in Example 4. Figure 2 (a) is a scanning electron microscope image of the BiOCl material in Example 1; Figure 2(b) is a scanning electron microscope image of the Cs3Bi2Br9 material obtained in Example 2; Figure 2 (c) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl material obtained in Example 3; Figure 2 (d) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4; Figure 2 (e) is a scanning electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 5. Figure 2 As shown in (a), BiOCl is spherical with a flower-like structure on its surface. Figure 2 As shown in (b), Cs3Bi2Br9 exhibits an irregular particle morphology, such as... Figure 2 (c) to Figure 2 As shown in (e), the Cs3Bi2Br9 / BiOCl composite material has a spherical morphology with fine particles growing on the surface, indicating that the flower-like structure of BiOCl restricts the growth of Cs3Bi2Br9 particles.

[0080] Figure 2 (f) is a low-magnification transmission electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4; Figure 2 (g) to Figure 2 (k) is the elemental distribution diagram of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4. It can be seen that the elements Bi, O, Cl, Cs, and Br are evenly distributed. Figure 2 (l) is a high-resolution transmission electron microscope image of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4. ， The presence of lattices representing Cs3Bi2Br9 and BiOCl in the composite material indicates the successful synthesis of the heterojunction.

[0081] Figure 3 The image shows the photocatalytic carbon dioxide reduction performance of BiOCl prepared in Example 1, Cs3Bi2Br9 prepared in Example 2, and Cs3Bi2Br9 / BiOCl materials prepared in Examples 3 to 5. Figure 3 It can be seen that the Cs3Bi2Br9 / BiOCl material prepared in Example 4 exhibits the best photocatalytic reduction performance for carbon dioxide, with a CO generation rate of 14.10 μmol·g. -1 ·h -1 It is higher than that of BiOCl and Cs3Bi2Br9 materials.

[0082] Figure 4 In-situ X-ray photoelectron spectroscopy and electron spin resonance spectroscopy of the Cs3Bi2Br9 / BiOCl composite material obtained in Example 4 are shown. Figure 4(a) is the fine Cs element spectrum of Example 4; Figure 4 (b) is the fine spectrum of Cl element from Example 4. Figure 4 (a) and Figure 4 (b) It can be seen that after BiOCl comes into contact with Cs3Bi2Br9, there is a built-in electric field in the heterojunction, which is conducive to internal charge migration. Under irradiation, electrons in Cs3Bi2Br9 / BiOCl are transferred from BiOCl to Cs3Bi2Br9. Figure 4 (c) is the DMPO-·OH spectrum of Example 4; Figure 4 (d) is DMPO-·O2 from Example 4 - Atlas. By Figure 4 (c) and Figure 4 (d) It can be seen that more photoexcited holes and electrons have accumulated in the valence band of BiOCl and the conduction band of Cs3Bi2Br9 in the Cs3Bi2Br9 composite material. Combined with the results of in-situ X-ray photoelectron spectroscopy analysis, it can be concluded that the carrier migration mechanism in the Cs3Bi2Br9 / BiOCl composite material is an S-type mechanism.

[0083] Therefore, this application presents a novel S-type heterostructure Cs3Bi2Br9 / BiOCl prepared by impregnation. BiOCl is a flower-shaped arrangement of stacked nanosheets, while Cs3Bi2Br9 grows on the surface of BiOCl as irregular particles. Results show that the heterostructure formed by Cs3Bi2Br9 / BiOCl can generate an internal electric field at the interface, which is beneficial for carrier separation. Furthermore, due to the unique migration mechanism of S-type carriers, the unused electrons in the BiOCl conduction band and the holes in the Cs3Bi2Br9 valence band recombine at the interface. This recombination of unused carriers effectively preserves the redox capabilities of both the Cs3Bi2Br9 conduction band and the BiOCl valence band. The composite material exhibits excellent photocatalytic activity under simulated sunlight irradiation. The prepared Cs3Bi2Br9 / BiOCl material shows a CO generation rate of 14.10 μmol·g⁻¹ for the photocatalytic reduction of carbon dioxide. -1 ·h -1 The performance is significantly higher than that of BiOCl and Cs3Bi2Br9 materials. These findings provide a new platform for the design, fabrication, and application of high-performance S-type photocatalysts under broadband light, with potential applications in carbon dioxide reduction.

[0084] The Cs3Bi2Br9 / BiOCl composite material prepared in this application can be used in products from the photocatalytic reduction of carbon dioxide.

[0085] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a Cs3Bi2Br9 / BiOCl composite material, characterized in that, The method comprises the following steps: Step S1: preparing BiOCl: mixing bismuth nitrate pentahydrate and acetic acid in a certain proportion and stirring to mix them uniformly until dissolution, then adding methanol and D(+)-glucosamine hydrochloride, transferring the mixed solution into an autoclave for reaction, collecting the sample by centrifugation after cooling to room temperature, washing with water and ethanol in sequence, and then placing it into a drying box for drying to obtain BiOCl; Step S2: preparing CsBr-BiBr3 solution: adding cesium bromide and bismuth bromide into dimethyl sulfoxide, and stirring to dissolve them to obtain CsBr-BiBr3 solution; Step S3: adding BiOCl obtained in step S1 into CsBr-BiBr3 solution obtained in step S2 in a certain proportion, stirring to mix them uniformly, and then placing the mixed solution into a drying box for drying; Step S4: taking the powder obtained in step S3, adding isopropyl alcohol solution drop by drop into the powder under stirring, reacting for 0.5-2 hours after the addition is completed, collecting the sample by centrifugation, washing the sample with ethanol, collecting the washed sample by centrifugation, and drying it in a drying box to obtain Cs3Bi2Br9 / BiOCl composite material.

2. The production method according to claim 1, characterized by, In the step of preparing BiOCl in step S1, the mass ratio of the bismuth nitrate pentahydrate to the D(+)-glucosamine hydrochloride is 4.852:1.510, the amount of the acetic acid is 10-50 ml, the amount of the methanol is 100-140 ml, and the temperature for heat reaction in the autoclave is 160-180°C. In the step of preparing CsBr-BiBr3 solution in step S2, the mass ratio of the cesium bromide to the bismuth bromide is 0.096:0.1345, and the amount of the dimethyl sulfoxide is 5-15 ml.

3. The preparation method according to claim 1, characterized in that, In step S3, the amount of the BiOCl is 0.15-0.35 g, the amount of the CsBr-BiBr3 solution is 1 ml-4 ml, the stirring time is 30-90 minutes, and the drying temperature in the drying box is 50-90°C.

4. The method of claim 1, wherein, In step S4, the amount of the isopropyl alcohol solution is 3 ml-7 ml, the stirring time is 30-90 minutes, and the drying temperature in the drying box is 50-90°C.

5. The preparation method according to claim 1, characterized in that, The Cs3Bi2Br9 / BiOCl composite material is prepared by the preparation method of any one of the preceding claims 1-5.

6. A Cs3Bi2Br9 / BiOCl composite material, characterized in that, 7. Application of the Cs3Bi2Br9 / BiOCl composite material of claim 6 in photocatalytic reduction of carbon dioxide. ​

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