Preparation method of sandwich type two-dimensional flaky heterojunction

Abstract

The invention relates to the technical field of heterojunction preparation, in particular to a preparation method of a sandwich type two-dimensional flaky heterojunction. The preparation method comprises the following steps: dissolving CsBr in a precursor solvent to obtain a precursor solution A; biBr3 and AgBr are dissolved in HBr, and a precursor solution B is obtained; the ratio of the mole of the BiBr3 to the volume of the HBr is (0.29 mmol): (0.09 to 0.18 mmol): 2.3 mL; mixing the precursor solution A, the precursor solution B and isopropanol to obtain a precursor solution C; and heating the precursor solution C to 90-95 DEG C, and naturally cooling to obtain the sandwich type two-dimensional sheet heterojunction. By changing the molar ratio of Ag / Bi and adding isopropanol, the speed of synthesizing the heterojunction by a traditional two-step method is increased, the morphology of the heterojunction is accurately regulated and controlled, and the sandwich type heterojunction with a large specific surface area is formed.

Description

Technical Field

[0001] The invention relates to the technical field of heterojunction preparation, and in particular to a method for preparing a sandwich-type two-dimensional sheet heterojunction. Background Art

[0002] Perovskites play a vital role in the degradation of organic pollutants. They can be used as effective photocatalysts to degrade refractory antibiotic residues in ethanol. It has been proven that photosensitive materials with large specific surface areas (such as two-dimensional morphologies such as thin sheets) are expected to achieve better catalytic performance. However, most of them currently use quantum dots or other ligands to control the morphology. It is still a challenge to obtain large-volume, high-yield, and controllable synthesis of two-dimensional morphologies of perovskites. The separation efficiency of photogenerated carriers is another important factor affecting photocatalytic performance. In order to increase the heterojunction area and carrier separation efficiency, people have tried to prepare two-dimensional sheet-like halide perovskite heterojunctions.

[0003] In order to ensure the purity of each substance during the heterojunction growth process, a two-step synthesis of the heterojunction is usually required (Nature 2020, 580, 614–620). Traditional perovskite heterostructures are prepared by epitaxial growth, ion exchange, and phase separation. However, due to the stimulation of self-luminescence or external light, electric field, or thermal field, ion diffusion structures are often prone to phase mixing (Nano Letters, 2020, 20, 8151-8156).

[0004] Therefore, using a rapid synthesis method to achieve large-area, high-efficiency, and controllable two-dimensional sheet-like sandwich-type halide perovskite heterojunction preparation is crucial for its further practical application and even industrialization. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a sandwich-type two-dimensional sheet heterojunction, which solves the problems that the synthesis of sandwich-type two-dimensional sheet CABB / CBB / CABB heterojunction is slow, requires high temperature and high pressure, has a small area and cannot be adjusted.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a sandwich-type two-dimensional sheet heterojunction, comprising the following steps:

[0008] 1) dissolving CsBr in a precursor solvent to obtain a precursor solution A;

[0009] 2) Dissolve BiBr3 and AgBr in HBr to obtain precursor solution B;

[0010] The volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.09-0.18mmol:2.3mL;

[0011] 3) mixing the precursor solution A obtained in step 1) with the precursor solution B obtained in step 2) and isopropanol to obtain a precursor solution C;

[0012] 4) heating the precursor solution C obtained in step 3) to 90-95° C. and cooling naturally to obtain a sandwich-type two-dimensional sheet heterojunction;

[0013] There is no time sequence limitation for step 1) and step 2).

[0014] Preferably, in step 1), the volume ratio of the mole of CsBr to the precursor solvent is 4.5 mmol:52.5 mL.

[0015] Preferably, the precursor solvent includes HBr and water.

[0016] Preferably, the volume ratio of HBr to water is 34.5 mL:18 mL.

[0017] Preferably, in step 2), the volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.12-0.15mmol:2.3mL.

[0018] Preferably, in step 3), the volume ratio of the precursor solutions A and B to isopropanol is 5.25 mL:2.3 mL:11.3 mL.

[0019] The present invention improves the speed of the traditional two-step heterojunction synthesis, precisely controls the heterojunction morphology, and forms a sandwich heterojunction with a large specific surface area by changing the molar ratio of Ag / Bi and adding an anti-solvent (isopropanol). Examples 1-4 are CABB / CBB / CABB (0.3, 0.4, 0.5 and 0.6) heterojunction single crystals obtained by this scheme. The present invention uses isopropanol as an anti-solvent, and injects a mixed solution of BiBr and HBr (AgBr is dissolved therein) into a mixed solution of CsBr, HBr and water (the solution is heated to 95°C). After a few seconds, two-dimensional thin sheets of perovskite sandwich heterojunction single crystals begin to suspend in the solution. The resulting samples have regular shapes, controllable crystal morphology, and high crystallinity (such as Figure 2-5 shown).

[0020] Comparative Example 1 is a CABB / CBB / CABB (0.6) crystal synthesized by a traditional two-step method. The specific experimental scheme is to dissolve the precursor into HBr, heat the solution to 95°C, cool it naturally to room temperature, and wait for crystal precipitation after a few hours. After heating the HBr solution mixed with AgBr to 95°C, drip it on the crystal, cool it naturally to room temperature, and no heterojunction structure is generated.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention only requires one step of operation, and the entire growth process only takes a few seconds, which saves time, is easy to operate, and does not require high temperature and high pressure. It can be synthesized in large quantities without the participation of ligands, has good stability, and high reproducibility, which provides favorable conditions for its application in the fields of photocatalysis and photovoltaics.

[0023] (2) The present invention breaks away from the traditional synthesis method of forming a heterojunction structure on a substrate and forms an independent two-dimensional single crystal without the need for a substrate, thus breaking the technical barriers and expanding the scope of application.

[0024] (3) The present invention overcomes the single-sided heterojunction structure formed on the substrate by the traditional two-step synthesis method and forms a sandwich structure, which has a larger specific surface area, higher photon utilization, more efficient carrier separation and transmission, and achieves performance improvement.

[0025] (4) The present invention can precisely control the heterojunction morphology through a stoichiometric control method, and can realize the preparation of heterojunctions of different areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0027] Figure 1 Schematic diagram of the experimental process of preparing CABB / CBB / CABB heterojunction by antisolvent-mediated one-step rapid growth method;

[0028] Figure 2 This is an optical microscope photo of a CABB / CBB / CABB (0.6) heterojunction single crystal thin film prepared by an anti-solvent-mediated one-step rapid growth method in the examples;

[0029] Figure 3 This is an optical microscope photo of a CABB / CBB / CABB (0.5) heterojunction single crystal thin film prepared by an anti-solvent-mediated one-step rapid growth method in the example;

[0030] Figure 4 This is an optical microscope photo of a CABB / CBB / CABB (0.4) heterojunction single crystal thin film prepared by an anti-solvent-mediated one-step rapid growth method in the example;

[0031] Figure 5 This is an optical microscope photo of a CABB / CBB / CABB (0.3) heterojunction single crystal thin film prepared by an anti-solvent-mediated one-step rapid growth method in the example;

[0032] Figure 6 An optical microscope photograph of a CABB / CBB / CABB (0.6) heterojunction single crystal thin film synthesized using a conventional two-step method in a comparative example;

[0033] Figure 7 XRD patterns of CABB / CBB / CABB (0.3, 0.4, 0.5 and 0.6) prepared by the one-step rapid growth method proposed in the present invention and photos of large-scale synthesized samples. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a sandwich-type two-dimensional sheet heterojunction, comprising the following steps:

[0035] 1) dissolving CsBr in a precursor solvent to obtain a precursor solution A;

[0036] 2) Dissolve BiBr3 and AgBr in HBr to obtain precursor solution B;

[0037] The volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.09-0.18mmol:2.3mL;

[0038] 3) mixing the precursor solution A obtained in step 1) with the precursor solution B obtained in step 2) and isopropanol to obtain a precursor solution C;

[0039] 4) heating the precursor solution C obtained in step 3) to 90-95° C. and cooling naturally to obtain a sandwich-type two-dimensional sheet heterojunction;

[0040] There is no time sequence limitation for step 1) and step 2).

[0041] The present invention dissolves CsBr in a precursor solvent to obtain a precursor solution A. In the present invention, the volume ratio of the mole of CsBr to the precursor solvent is preferably 4.5mmol:52.5mL. In the present invention, the precursor solvent preferably includes HBr and water. In the present invention, the volume ratio of the HBr to water is 34.5mL:18mL. In the present invention, the water is preferably deionized water.

[0042] In the present invention, BiBr3 and AgBr are dissolved in HBr to obtain a precursor solution B; the volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.09-0.18mmol:2.3mL. In the present invention, the volume ratio of the moles of BiBr3 and AgBr to HBr is preferably 0.29mmol:0.12-0.15mmol:2.3mL.

[0043] The present invention heats the obtained precursor solution C to 90-95° C. and cools it naturally to obtain a sandwich-type two-dimensional sheet heterojunction.

[0044] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] The synthesis of sandwich-type two-dimensional sheet heterojunction CABB / CBB / CABB (0.6) was carried out using Figure 1 The experimental flow chart shown:

[0047] CsBr (0.45 mmol) was dissolved in 5.25 mL of HBr and deionized water (the volume ratio of deionized water to HBr was 34.5:18) as precursor solution A.

[0048] BiBr3 (0.29 mmol) and AgBr (0.18 mmol) were dissolved in 2.3 mL HBr to obtain precursor solution B.

[0049] Precursor solution A and B were mixed with 11.3 ml of isopropanol (the volume ratio of precursor solution A and B to anti-solvent was 5.25 ml:2.3 ml:11.3 ml) to obtain precursor solution C.

[0050] The precursor solution C is heated to 95°C and then cooled naturally to room temperature. After a few seconds, heterojunction flakes begin to form on the upper layer of the solution. A large number of sandwich-type two-dimensional heterojunction CABB / CBB / CABB (0.6) flakes can be obtained in about 2 minutes. Figure 2 As shown, the obtained flakes are regular hexagons with a lateral size of about 70 μm.

[0051] Example 2

[0052] The synthesis of sandwich-type two-dimensional sheet heterojunction CABB / CBB / CABB (0.5) was carried out using Figure 1 The experimental flow chart shown:

[0053] CsBr (0.45 mmol) was dissolved in 5.25 mL of HBr and deionized water (the volume ratio of deionized water to HBr was 34.5:18) as precursor solution A.

[0054] BiBr3 (0.29 mmol) and AgBr (0.15 mmol) were dissolved in 2.3 mL HBr to obtain precursor solution B.

[0055] Precursor solution A and B were mixed with 11.3 ml of isopropanol (the volume ratio of precursor solution A and B to anti-solvent was 5.25 ml:2.3 ml:11.3 ml) to obtain precursor solution C.

[0056] The precursor solution C is heated to 95°C and then cooled naturally to room temperature. After a few seconds, heterojunction flakes begin to form on the upper layer of the solution. A large number of sandwich-type two-dimensional heterojunction CABB / CBB / CABB (0.5) flakes can be obtained in about 2 minutes. Figure 3 As shown, the obtained flakes are regular hexagons with a lateral size of about 70 μm.

[0057] Example 3

[0058] The synthesis of sandwich-type two-dimensional sheet heterojunction CABB / CBB / CABB (0.4) was carried out using Figure 1 The experimental flow chart shown:

[0059] CsBr (0.45 mmol) was dissolved in 5.25 mL of HBr and deionized water (the volume ratio of deionized water to HBr was 34.5:18) as precursor solution A.

[0060] BiBr3 (0.29 mmol) and AgBr (0.12 mmol) were dissolved in 2.3 mL HBr to obtain precursor solution B.

[0061] Precursor solution A and B were mixed with 11.3 ml of isopropanol (the volume ratio of precursor solution A and B to anti-solvent was 5.25 ml:2.3 ml:11.3 ml) to obtain precursor solution C.

[0062] The precursor solution C is heated to 95°C and then cooled naturally to room temperature. After a few seconds, heterojunction flakes begin to form on the upper layer of the solution. A large number of sandwich-type two-dimensional heterojunction CABB / CBB / CABB (0.4) flakes can be obtained in about 2 minutes. Figure 4 As shown, the obtained flakes are regular hexagons with a lateral size of about 70 μm.

[0063] Example 4

[0064] The synthesis of sandwich-type two-dimensional sheet heterojunction CABB / CBB / CABB (0.3) was carried out using Figure 1 The experimental flow chart shown:

[0065] CsBr (0.45 mmol) was dissolved in 5.25 mL of HBr and deionized water (the volume ratio of deionized water to HBr was 34.5:18) as precursor solution A.

[0066] BiBr3 (0.29 mmol) and AgBr (0.09 mmol) were dissolved in 2.3 mL HBr to obtain precursor solution B.

[0067] Precursor solution A and B were mixed with 11.3 ml of isopropanol (the volume ratio of precursor solution A and B to anti-solvent was 5.25 ml:2.3 ml:11.3 ml) to obtain precursor solution C.

[0068] The precursor solution C is heated to 95°C and then cooled naturally to room temperature. After a few seconds, heterojunction flakes begin to form on the upper layer of the solution. A large number of sandwich-type two-dimensional heterojunction CABB / CBB / CABB (0.3) flakes can be obtained in about 2 minutes. Figure 5 As shown, the obtained flakes are regular hexagons with a lateral size of about 70 μm.

[0069] Comparative Example 1

[0070] Two-dimensional sheet heterojunction CABB / CBB / CABB (0.6) synthesized using the traditional two-step method:

[0071] CsBr (0.45 mmol) was dissolved in 5.25 mL of HBr and deionized water (the volume ratio of deionized water to HBr was 34.5:18), and heated to 95° C. to form precursor solution A.

[0072] BiBr3 (0.29 mmol) was dissolved in 2.3 mL HBr and heated to 95°C to obtain precursor solution B.

[0073] Precursor solution B and 11.3 ml of isopropanol (the volume ratio of precursor solution A+B to isopropanol is 7.55:11.3) were mixed and heated to 95° C. to obtain precursor solution C.

[0074] The precursor solution C is quickly injected into the precursor solution A. After one second, floating flake single crystals appear in the solution. Then, the solution is naturally cooled to room temperature to obtain a large number of CBB single crystal thin sheets.

[0075] The single crystal slice was washed with ethanol and dried in an oven at about 40°C.

[0076] AgBr (0.18 mmol) was dissolved in 2.3 mL HBr as precursor solution D.

[0077] Immerse the CBB single crystal slice in the precursor solution D for 1 hour to obtain a CABB polyhedral crystal, such as Figure 6 As shown, the obtained crystals are irregular in shape and no heterojunction structure is found.

[0078] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a sandwich-type two-dimensional sheet heterojunction, characterized in that: The following steps are involved: 1) dissolving CsBr in a precursor solvent to obtain a precursor solution A; 2) Dissolve BiBr3 and AgBr in HBr to obtain precursor solution B; The volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.09-0.18mmol:2.3mL; 3) mixing the precursor solution A obtained in step 1) with the precursor solution B obtained in step 2) and isopropanol to obtain a precursor solution C; 4) heating the precursor solution C obtained in step 3) to 90-95° C. and cooling naturally to obtain a sandwich-type two-dimensional sheet heterojunction; There is no time sequence limitation for step 1) and step 2).

2. The preparation method according to claim 1, characterized in that: In the step 1), the volume ratio of the mole of CsBr to the precursor solvent is 4.5 mmol:52.5 mL.

3. The preparation method according to claim 1 or 2, characterized in that: The precursor solvent includes HBr and water.

4. The preparation method according to claim 3, characterized in that: The volume ratio of HBr to water is 34.5 mL:18 mL.

5. The preparation method according to claim 1, characterized in that: In the step 2), the volume ratio of the moles of BiBr3 and AgBr to HBr is 0.29mmol:0.12-0.15mmol:2.3mL.

6. The preparation method according to claim 1, characterized in that: In the step 3), the volume ratio of the precursor solutions A and B to isopropanol is 5.25 mL:2.3 mL:11.3 mL.

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