Composite nanomaterial, preparation method and application thereof
By using composite nanomaterials with a stacked structure of BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets, the problems of insufficient photocatalytic performance and stability of metal halide perovskite materials were solved, and the effect of efficient catalytic reduction of carbon dioxide to carbon monoxide was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2024-03-15
- Publication Date
- 2026-06-09
Smart Images
Figure CN118304904B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic materials technology, and specifically relates to a composite nanomaterial, its preparation method, and its application. Background Technology
[0002] CO2 is a safe, inexpensive, readily available, and abundant renewable resource with high carbon content. Therefore, the efficient conversion of CO2 into high-value-added fine chemicals is of great significance. The key to achieving this goal is the development of advanced, high-performance photocatalysts.
[0003] Currently, numerous photocatalytic materials have been used to perform photocatalytic chemical reactions of CO2 in reaction systems under visible or ultraviolet light, such as metal-free compounds (e.g., C3N4), metal oxides (e.g., TiO2, ZnO), metal sulfides (e.g., CdS, ZnS), and metal-organic frameworks (MOFs). Furthermore, metal halide perovskites (MHPs), as highly efficient photocatalysts with excellent photoelectric properties, have become candidate materials for photocatalysis due to their superior light absorption, good carrier transport capacity, low binding energy, and tunable band gap. More importantly, MHPs are easily synthesized into nanocrystal or quantum dot structures, are low in cost, and possess tunable chemical composition and structure. However, metal halide perovskite materials suffer from low photocatalytic performance due to severe recombination of photogenerated carriers. Additionally, they are highly unstable in aqueous systems and prone to decomposition, resulting in poor long-term catalytic performance.
[0004] Therefore, there is an urgent need to provide a composite nanomaterial with good catalytic performance and stability. Summary of the Invention
[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial alternative or create conditions. Specifically, the present invention provides a composite nanomaterial with good catalytic performance and stability.
[0006] The inventive concept of this invention: The composite nanomaterial of this invention comprises BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets stacked from bottom to top. The internal structure of this composite nanomaterial allows for the formation of a double heterojunction, promoting the separation of photogenerated electrons and holes. Furthermore, since the BiOBr, CsPbBr3, and CdS nanosheets are all 2D materials, they possess the advantages of a large specific surface area and the ability to expose more reactive sites, resulting in excellent photocatalytic activity. In addition, the stacked layered structure of the composite nanomaterial effectively protects CsPbBr3, improving the stability of the composite nanomaterial.
[0007] Therefore, a first aspect of the present invention provides a composite nanomaterial.
[0008] Specifically, a composite nanomaterial includes BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets stacked from bottom to top.
[0009] Preferably, the lateral dimension of the BiOBr nanosheet is 50-110 nm; more preferably, the lateral dimension of the BiOBr nanosheet is 55-100 nm.
[0010] Preferably, the thickness of the BiOBr nanosheet is 7-11 nm; more preferably, the thickness of the BiOBr nanosheet is 8-10 nm.
[0011] Preferably, the CsPbBr3 nanosheets are square.
[0012] Preferably, the size of the CsPbBr3 nanosheets is 9-45 nm; more preferably, the size of the CsPbBr3 nanosheets is 10-40 nm.
[0013] Specifically, the size of CsPbBr3 nanosheets refers to their lateral dimensions.
[0014] Preferably, the thickness of the CsPbBr3 nanosheets is 3.5-5.5 nm; more preferably, the thickness of the CsPbBr3 nanosheets is 4-5.2 nm.
[0015] Preferably, the CdS nanosheets have an irregular nanosheet structure.
[0016] A second aspect of the present invention provides a method for preparing the composite nanomaterial described in the first aspect of the present invention.
[0017] Specifically, the preparation method of the composite nanomaterial includes the following steps:
[0018] BiOBr nanosheets and CsPbBr3 nanosheets were mixed in a solvent, and then CdS nanosheets were added to prepare the composite nanomaterial.
[0019] Specifically, since BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets have different electronegativity, and the lateral dimension (length dimension) of BiOBr nanosheets is significantly larger than that of CsPbBr3 nanosheets, this invention uses BiOBr nanosheets as the bottom layer. After mixing, due to the different electronegativity, a composite nanomaterial is obtained by layer-by-layer attraction, in which BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets are stacked sequentially from bottom to top.
[0020] Preferably, the process of adding CdS nanosheets also includes centrifugation and drying.
[0021] Preferably, the solvent includes isopropanol.
[0022] Preferably, the mass ratio of the BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets is (1.8-4.5):(0.9-3.3):1; more preferably, the mass ratio of the BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets is (2-4):(1-3):1.
[0023] Preferably, the preparation method of the BiOBr nanosheets is as follows:
[0024] BiOBr nanosheets were prepared by mixing bismuth salt, bromide salt, and surfactant and then reacting them hydrothermally.
[0025] More preferably, the preparation method of the BiOBr nanosheets is as follows:
[0026] Bismuth salt and mannitol were mixed in a solvent, and then a surfactant and a bromide salt were added and mixed to obtain a mixture. The mixture was subjected to a hydrothermal reaction to obtain BiOBr nanosheets.
[0027] Preferably, the hydrothermal reaction further includes centrifugation and drying processes.
[0028] Preferably, the bismuth salt comprises Bi(NO3)3; more preferably, the bismuth salt comprises Bi(NO3)3·5H2O.
[0029] Preferably, the solvent is water; more preferably, the solvent is deionized water.
[0030] Preferably, the surfactant includes polyvinylpyrrolidone (PVP).
[0031] Preferably, the bromine salt comprises KBr.
[0032] Preferably, the hydrothermal reaction temperature is 140-180℃ and the hydrothermal reaction time is 2-4h; more preferably, the hydrothermal reaction temperature is 150-170℃ and the hydrothermal reaction time is 2.5-3.5h; even more preferably, the hydrothermal reaction temperature is 160℃ and the hydrothermal reaction time is 3h.
[0033] Preferably, the method for preparing the CsPbBr3 nanosheets is as follows:
[0034] (1) Mix cesium salt, oleic acid and octadecene, and heat to prepare a cesium oleate precursor solution;
[0035] (2) The CsPbBr3 nanosheets were prepared by mixing lead bromide and the cesium oleate precursor solution obtained in step (1).
[0036] Preferably, in step (1), the cesium salt includes cesium carbonate.
[0037] Preferably, in step (1), the heating process is to first heat to 160-200℃ and hold for 20-40 minutes, and then cool down to 110-150℃ and hold for 20-40 minutes.
[0038] More preferably, in step (1), the heating process is to first heat to 170-190℃ and hold for 25-35 minutes, and then cool down to 120-140℃ and hold for 25-35 minutes.
[0039] More preferably, in step (1), the heating process is to first heat to 180°C and hold for 30 minutes, and then cool down to 130°C and hold for 30 minutes.
[0040] Preferably, in step (1), the temperature after heating is 110-150℃; more preferably, the temperature after heating is 120-140℃; and even more preferably, the temperature after heating is 130℃.
[0041] Preferably, step (2) is: mixing lead bromide and ligand, heating, and then adding the cesium oleate precursor solution obtained in step (1) to prepare the CsPbBr3 nanosheets.
[0042] Preferably, the ligand comprises octadecene, oleic acid, oleylamine, octanoic acid, and octylamine.
[0043] Specifically, the octadecene, oleic acid, oleylamine, octanoic acid, and octylamine, as ligands, can passivate surface defects, stabilize CsPbBr3 nanosheets, and prevent the agglomeration of synthesized nanosheets.
[0044] Preferably, in step (2), after adding the cesium oleate precursor solution, a cooling process is also included.
[0045] Preferably, in step (2), the cesium oleate precursor solution is added and then cooled after 4-6 seconds; more preferably, in step (2), the cesium oleate precursor solution is added and then cooled after 4.5-5.5 seconds; even more preferably, in step (2), the cesium oleate precursor solution is added and then cooled after 5 seconds.
[0046] Preferably, liquid nitrogen is used for cooling.
[0047] Preferably, the method for preparing the CdS nanosheets is as follows:
[0048] The CdS nanosheets were prepared by mixing cadmium salt, thiourea, and solvent and then reacting them hydrothermally.
[0049] Preferably, the hydrothermal reaction further includes centrifugation and drying processes.
[0050] Preferably, the cadmium salt comprises Cd(OAc)2; more preferably, the cadmium salt comprises Cd(OAc)2·2H2O.
[0051] Preferably, the solvent includes ethylenediamine.
[0052] Preferably, the hydrothermal reaction temperature is 80-120℃ and the hydrothermal reaction time is 7-9h; more preferably, the hydrothermal reaction temperature is 90-110℃ and the hydrothermal reaction time is 7.5-8.5h; even more preferably, the hydrothermal reaction temperature is 100℃ and the hydrothermal reaction time is 8h.
[0053] A third aspect of the present invention provides the application of the composite nanomaterial described in the first aspect of the present invention in the catalytic reduction of carbon dioxide to prepare carbon monoxide.
[0054] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:
[0055] (1) The composite nanomaterial of the present invention can form a double heterojunction to promote the separation of photogenerated electrons and holes. At the same time, since BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets are all 2D materials, they have the advantages of large specific surface area and the ability to expose more reactive sites, which makes the composite nanomaterial have good photocatalytic activity. In addition, the stacked layered structure of the composite nanomaterial can fully protect the CsPbBr3 nanosheets and improve the stability of the composite nanomaterial.
[0056] (2) The preparation method of the present invention is simple, the reaction conditions are mild and the cost is low. Attached Figure Description
[0057] Figure 1 The images show the XRD patterns of BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials of Example 1 of this invention.
[0058] Figure 2 The ultraviolet spectra of BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets and BiOBr-CsPbBr3-CdS composite nanomaterials in Example 1 of this invention are shown below.
[0059] Figure 3 This is a transmission electron microscope (TEM) image of the BiOBr nanosheets from Example 1 of the present invention.
[0060] Figure 4 This is a transmission electron microscope (TEM) image of the CsPbBr3 nanosheets from Example 1 of the present invention.
[0061] Figure 5 This is a transmission electron microscope (TEM) image of the CdS nanosheets from Example 1 of the present invention.
[0062] Figure 6 This is a high-resolution transmission electron microscope image of the BiOBr-CsPbBr3-CdS composite nanomaterial of Example 1 of the present invention.
[0063] Figure 7 The diagram shows the catalytic performance of BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials in Example 1 of this invention.
[0064] Figure 8 The stability performance diagrams of BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials in Example 1 of this invention are shown.
[0065] Figure 9 The catalytic performance diagrams of the composite nanomaterials in Example 1 and Comparative Examples 1-3 of this invention are shown.
[0066] Figure 10 The stability performance diagrams of the composite nanomaterials in Embodiment 1 and Comparative Examples 1-3 of the present invention are shown. Detailed Implementation
[0067] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.
[0068] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.
[0069] Example 1
[0070] A BiOBr-CsPbBr3-CdS composite nanomaterial includes BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets; the composite nanomaterial has a stacked structure, with CsPbBr3 nanosheets and CdS nanosheets stacked sequentially on the BiOBr nanosheets.
[0071] A method for preparing BiOBr-CsPbBr3-CdS composite nanomaterials includes the following steps:
[0072] (1) 486 mg Bi(NO3)3·5H2O and 600 mg mannitol were dispersed in 30 mL of deionized water to form solution A; 100 mg PVP and 178.5 mg KBr were added to solution A and stirred for 1 h to form solution B; solution B was added to a 50 mL hydrothermal reactor and reacted at 160 °C for 3 h. After centrifugation, the solid was dried at 60 °C for 10 h to obtain BiOBr nanosheets.
[0073] (2) 200 mg Cs2CO3, 3 mL oleic acid and 5.1 mL octadecene were put into a 10 mL single-necked flask and heated to 180 °C under N2 atmosphere to completely dissolve Cs2CO3. Then the temperature was lowered to 130 °C and held for 30 min to finally obtain the cesium oleate precursor solution C.
[0074] (3) Add 10 mL of octadecene, 145 mg of PbBr2, 1 mL of oleic acid, 1 mL of oleylamine, 0.21 mL of octanoic acid and 0.21 mL of octylamine to a 25 mL three-necked flask, heat to 120 °C under N2 atmosphere and keep for 1 h until PbBr2 is completely dissolved, then heat to 130 °C and quickly inject 0.9 mL of the precursor solution C obtained in step (2), and cool rapidly with liquid nitrogen after 5 s; then centrifuge, take the precipitate and dry it at 60 °C for 5 h to obtain CsPbBr3 nanosheets;
[0075] (4) 533.06 mg Cd(OAc)2·2H2O and 456.72 mg SC(NH2)2 were dispersed in 60 mL of ethylenediamine and stirred for 1 h to obtain solution D; then solution D was transferred to 80 mL of hydrothermal reactor and reacted at 100 °C for 8 h to obtain suspension. After centrifugation, the precipitate was taken and washed several times with deionized water and ethanol. Then the precipitate was dried at 60 °C for 12 h to obtain yellow CdS nanosheets.
[0076] (5) 3 mg BiOBr nanosheets and 2 mg CsPbBr3 nanosheets were dispersed in 1 mL of isopropanol, ultrasonically dispersed for 5 min and stirred for 1 h. Then 1 mg CdS nanosheets were added, ultrasonically dispersed for 5 min and stirred for 1 h. The resulting solution was centrifuged, the supernatant was discarded, the precipitate was taken and dried at 50 °C for 6 h to obtain BiOBr-CsPbBr3-CdS composite nanomaterial.
[0077] Example 2
[0078] The only difference between Example 2 and Example 1 is that in step (1), the amount of PVP added is 200mg, and the rest is the same as in Example 1.
[0079] Example 3
[0080] The only difference between Example 3 and Example 1 is that in step (1), the amount of PVP added is 300mg, and the rest is the same as in Example 1.
[0081] Example 4
[0082] The only difference between Example 4 and Example 1 is that in step (1), the amount of PVP added is 400mg, and the rest is the same as in Example 1.
[0083] Example 5
[0084] The only difference between Example 5 and Example 1 is that in step (5), the amount of isopropanol added is 2 mL, and the rest is the same as in Example 1.
[0085] Example 6
[0086] The only difference between Example 6 and Example 1 is that in step (5), the amount of isopropanol added is 3 mL, and the rest is the same as in Example 1.
[0087] Comparative Example 1
[0088] A BiOBr-CsPbBr3 composite material includes BiOBr nanosheets and CsPbBr3 nanosheets; the CsPbBr3 nanosheets are located on the BiOBr nanosheets.
[0089] The preparation method of BiOBr-CsPbBr3 composite material is the same as that in Example 1, except that step (4) is not performed.
[0090] Comparative Example 2
[0091] A CsPbBr3-CdS composite material includes CsPbBr3 nanosheets and CdS nanosheets; the CdS nanosheets are located on the CsPbBr3 nanosheets.
[0092] The preparation method of CsPbBr3-CdS composite material is the same as that in Example 1, except that step (1) is not performed.
[0093] Comparative Example 3
[0094] A BiOBr-CdS composite material includes BiOBr nanosheets and CdS nanosheets; the CdS nanosheets are located on the BiOBr nanosheets.
[0095] The preparation method of BiOBr-CdS composite material is different from that of Example 1 only in that steps (2) and (3) are not performed, and the rest is the same as that of Example 1.
[0096] Performance testing
[0097] 1. XRD Testing
[0098] XRD tests were performed on the BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials prepared in steps (1), (3), (4), and (5) of Example 1. The test results are as follows: Figure 1 As shown.
[0099] Depend on Figure 1 It can be seen that the positions of the diffraction peaks of BiOBr nanosheets correspond one-to-one with the standard cards of BiOBr, CsPbBr3 nanosheets correspond one-to-one with the standard cards of CsPbBr3, and CdS nanosheets correspond one-to-one with the standard cards of CdS. This indicates the successful preparation of BiOBr, CsPbBr3, and CdS nanosheets. Furthermore, the BiOBr-CsPbBr3-CdS composite nanomaterial exhibits diffraction peaks for BiOBr, CsPbBr3, and CdS, respectively, further confirming the successful preparation of the BiOBr-CsPbBr3-CdS composite nanomaterial.
[0100] 2. Ultraviolet spectrum
[0101] The BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials prepared in steps (1), (3), (4), and (5) of Example 1 were subjected to ultraviolet spectroscopy tests. The test results are as follows: Figure 2 As shown.
[0102] Depend on Figure 2 It can be seen that the absorption edge of BiOBr nanosheets is around 430 nm, that of CsPbBr3 nanosheets is around 550 nm, and that of CdS nanosheets is around 540 nm; while in the absorption spectrum of BiOBr-CsPbBr3-CdS composite nanomaterials, the characteristic absorptions of BiOBr, CsPbBr3 and CdS appear.
[0103] 3. Transmission electron microscopy analysis
[0104] Transmission electron microscopy (TEM) analysis was performed on the BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets prepared in steps (1), (3), and (4) of Example 1. The test results are as follows: Figure 3 , 4 As shown in Figure 5.
[0105] Depend on Figure 3-5It can be seen that the BiOBr prepared in Example 1 is in the form of regular nanosheets with a lateral dimension of 55-100 nm and a thickness of 8-10 nm; CsPbBr3 is in the form of regular square nanosheets with a lateral dimension of 10-40 nm and a thickness of 4-5.2 nm; CdS is in the form of irregular nanosheets with wrinkles.
[0106] The BiOBr-CsPbBr3-CdS composite nanomaterials prepared in step (5) of Example 1 were analyzed by high-resolution transmission electron microscopy (HRTEM), and the test results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the composite nanomaterials exhibit a stacked structure.
[0107] 4. Catalytic performance test
[0108] 3 mg of the BiOBr nanosheets, CsPbBr3 nanosheets, CdS nanosheets, and BiOBr-CsPbBr3-CdS composite nanomaterials prepared in steps (1), (3), (4), and (5) of Example 1 were coated onto quartz cloth and placed at the bottom of a 100 mL single-necked flask. High-purity carbon dioxide and water vapor were then simultaneously introduced into the photocatalytic system to ensure sufficient CO2. A 600 W Xe light source was used for 6 hours of irradiation. After irradiation, the products were detected using a GC-2014 gas chromatograph. The catalytic performance of the composite nanomaterials of this invention in photocatalytic reduction of CO2 to CO is as follows: Figure 7 As shown.
[0109] Depend on Figure 7 It can be seen that the photocatalytic reduction of CO2 to CO yields of BiOBr-CsPbBr3-CdS composite nanomaterials, BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets are 316.1 μmol g, respectively. -1 h -1 17.2 μmol g -1 h -1 29.0 μmolg -1 h -1 and 8.2 μmol g -1 h -1 This indicates that the photocatalytic reduction of CO2 to CO by BiOBr-CsPbBr3-CdS composite nanomaterials exhibits significantly better catalytic activity than BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets.
[0110] Following the above testing method, the products were detected using GC-2014 gas chromatography after irradiation for 0h, 16h, 32h, 48h, 64h, and 80h respectively. The stability of the BiOBr-CsPbBr3-CdS composite nanomaterial for photocatalytic reduction of CO2 to CO in this invention is as follows: Figure 8 As shown. By Figure 8 It can be seen that the catalytic stability of BiOBr-CsPbBr3-CdS composite nanomaterials is significantly better than that of BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets.
[0111] The catalytic performance of the materials prepared in Example 1 and Comparative Examples 1-3 was tested using the same method described above. After 6 hours of illumination, the products were detected using GC-2014 gas chromatography. The catalytic performance of the materials prepared in Example 1 and Comparative Examples 1-3 for the photocatalytic reduction of CO2 to CO is as follows: Figure 9 As shown, by Figure 9 It can be seen that the photocatalytic reduction of CO2 to CO yields of the materials prepared in Example 1 and Comparative Examples 1-3 were 316.1 μmol g, respectively. -1 h -1 196.4 μmol g -1 h -1 107.8 μmol g -1 h -1 and 65.825 μmol g -1 h -1 This demonstrates that the BiOBr-CsPbBr3-CdS composite nanomaterials prepared in Example 1 of this invention exhibit excellent photocatalytic performance, significantly superior to comparative examples 1-3.
[0112] Following the same method described above, the materials prepared in Example 1 and Comparative Examples 1-3 were irradiated for 0 h, 16 h, 32 h, 48 h, 64 h, and 80 h, respectively, and the products were detected using GC-2014 gas chromatography. The stability of the photocatalytic reduction of CO2 to CO by the materials prepared in Example 1 and Comparative Examples 1-3 is as follows: Figure 10 As shown. By Figure 10 It can be seen that the catalytic stability of the BiOBr-CsPbBr3-CdS composite nanomaterial is significantly better than that of the BiOBr-CsPbBr3-CdS composite nanomaterials in comparative examples 1-3. 3、 CsPbBr3-CdS, BiOBr-CdS.
[0113] The test results above show that BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets are all indispensable in composite nanomaterials. The combined effect of the three makes the composite nanomaterials have good catalytic performance and stability.
[0114] Furthermore, the composite nanomaterials prepared in Examples 2-6 of this invention also exhibit good catalytic performance and stability.
[0115] In summary, the BiOBr-CsPbBr3-CdS composite nanomaterial prepared by this invention can form a double heterojunction to promote the separation of photogenerated electrons and holes. Furthermore, the BiOBr nanosheets, CsPbBr3 nanosheets, and CdS nanosheets are stacked sequentially and work together to give the composite nanomaterial good catalytic performance and stability.
[0116] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A composite nanomaterial, characterized in that, It includes BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets stacked from bottom to top.
2. The composite nanomaterial according to claim 1, characterized in that, The thickness of the BiOBr nanosheets is 7-11 nm.
3. The composite nanomaterial according to claim 1, characterized in that, The thickness of the CsPbBr3 nanosheets is 3.5-5.5 nm.
4. The composite nanomaterial according to claim 1, characterized in that, The CdS nanosheets have an irregular nanosheet structure.
5. The method for preparing the composite nanomaterial according to any one of claims 1-4, characterized in that, Includes the following steps: BiOBr nanosheets and CsPbBr3 nanosheets were mixed in a solvent, and then CdS nanosheets were added to prepare the composite nanomaterial.
6. The preparation method according to claim 5, characterized in that, The mass ratio of the BiOBr nanosheets, CsPbBr3 nanosheets and CdS nanosheets is (1.8-4.5):(0.9-3.3):
1.
7. The preparation method according to claim 5, characterized in that, The preparation method of the BiOBr nanosheets is as follows: BiOBr nanosheets were prepared by mixing bismuth salt, bromide salt, and surfactant and then reacting them hydrothermally.
8. The preparation method according to claim 5, characterized in that, The preparation method of the CsPbBr3 nanosheets is as follows: (1) Mix cesium salt, oleic acid and octadecene, and heat to prepare a cesium oleate precursor solution; (2) The CsPbBr3 nanosheets were prepared by mixing lead bromide and the cesium oleate precursor solution obtained in step (1).
9. The preparation method according to claim 5, characterized in that, The method for preparing the CdS nanosheets is as follows: The CdS nanosheets were prepared by mixing cadmium salt, thiourea, and solvent and then reacting them hydrothermally.
10. The application of the composite nanomaterial according to any one of claims 1-4 in the catalytic reduction of carbon dioxide to prepare carbon monoxide.