阅读说明：本技术 一种无铅铋基混合卤化钙钛矿纳米片及其制备方法和应用 (Lead-free bismuth-based mixed halogenated perovskite nanosheet and preparation method and application thereof ) 是由 尹双凤 白张君 陈浪 申升 郭君康 于 2021-01-11 设计创作，主要内容包括：本发明公开了一种无铅铋基混合卤化钙钛矿纳米片及其制备方法和应用,本发明以简单的反溶剂再结晶法制备了Cs-3Bi-(2-x)Sb-xBr-9纳米片,其分子式为Cs-3Bi-(2-x)Sb-xBr-9,式中0﹤x≤0.4。Sb的引入增加了Cs-3Bi-2Br-9的可见光吸收能力和光生载流子的分离效率。Sb良好的尺寸匹配提高了Cs-3Bi-2Br-9钙钛矿材料的稳定性。少量的Sb掺杂促进了C(sp～3)-H键活化关键活性物种空穴的产生。(The invention discloses a lead-free bismuth-based mixed halogenated perovskite nanosheet and a preparation method and application thereof 3 Bi 2‑x Sb x Br 9 Nanosheets having a molecular formula of Cs 3 Bi 2‑x Sb x Br 9 And x is less than or equal to 0.4 in the formula < 0 >. Introduction of Sb increased Cs 3 Bi 2 Br 9 Visible light absorption capability and photogenerated carrier separation efficiency. Good size matching of Sb improves Cs 3 Bi 2 Br 9 Stability of the perovskite material. The small amount of Sb doping promotes C (sp) 3 ) The H bond activates the generation of a hole of a key active species.)

1. A lead-free bismuth-based mixed halogenated perovskite nanosheet is characterized in that: its molecular formula is Cs₃Bi_2-xSb_xBr₉And x is less than or equal to 0.4 in the formula < 0 >.

2. The lead-free bismuth-based mixed halogenated perovskite nanoplate as claimed in claim 1, characterized in that: x in the molecular formula is more than or equal to 0.1 and less than or equal to 0.3.

3. The lead-free bismuth-based mixed halogenated perovskite nanoplate as claimed in claim 2, characterized in that: in the formula, x is 0.2.

4. A method of producing lead-free bismuth-based mixed halogenated perovskite nanoplate as claimed in any one of claims 1 to 3, characterized by comprising the steps of:

(1) according to a set molar ratio, CsBr and BiBr are added₃And SbBr₃Dissolving in DMSO to obtain precursor solution;

(2) adding the precursor liquid obtained in the step (1) into isopropanol, crystallizing for 0.5-5 min by an anti-solvent method, washing and drying to obtain the productCs₃Bi_2-xSb_xBr₉Nanosheets.

5. The method of claim 4, wherein: the BiBr in the step (1)₃And SbBr₃The molar ratio of (1.7: 0.3) - (1.9: 0.1), and the concentration of CsBr in DMSO is 10-20 mM.

6. The method of claim 5, wherein: the BiBr₃And SbBr₃Is 1.8: 0.2.

7. The method of claim 4, wherein: the volume ratio of the precursor liquid to the isopropanol in the step (2) is 1: 20-1: 30.

8. The method of claim 4, wherein: in the step (2), washing with chloroform, and then drying in a vacuum oven at 60 ℃ for 10 hours to obtain Cs₃Bi_2-xSb_xBr₉Nanosheets.

9. Use of the lead-free bismuth-based mixed halogenated perovskite nanoplate as defined in any one of claims 1 to 3 or the lead-free bismuth-based mixed halogenated perovskite nanoplate produced by the production method as defined in any one of claims 4 to 8, characterized in that: it is used for photocatalysis of C (sp)³) -H bond activation reaction.

Technical Field

The invention relates to the technical field of nano material preparation and photocatalysis, in particular to a lead-free bismuth-based mixed halogenated perovskite nanosheet, a preparation method thereof and application thereof in photocatalysis C (sp)³) -H bond activation.

Background

The selective oxidation of saturated hydrocarbons to produce high value added products (e.g., aldehydes, ketones, and epoxides) is one of the most challenging and interesting disciplines in catalytic chemistry today. Due to C (sp)³) -H bond (70-130 kcalmol)^-1) High bond dissociation energy and unfavorable adsorption, often requiring harsh conditions (high temperature and/or pressure). In addition, the conversion rate must be suppressed to less than<15% to avoid over oxidation of the product under such harsh conditions resulting in poor selectivity. To solve this problem, replacing traditional thermal catalysis with mild photocatalysis is a promising solution. Heterogeneous photocatalytic systems of metal oxides and metal sulfides have now led to an extensive search by researchers due to their high stability and ease of separationAttention is paid. However, the performance of these photocatalysts is still not ideal due to narrow light absorption, low charge separation efficiency and conversion efficiency. All-metal halide perovskite A^IPb^IIX₃(A ═ Rb, Cs; B ═ Ge, Pb, Sn; and X ═ Cl, Br, I), in particular CsPbBr₃And CsPbI₃It has proven to be a promising photocatalytic material due to its appropriate bandgap, excellent light absorption and efficient carrier mobility. However, the use of lead in the field of photocatalysis is limited due to its toxicity, low oxidation capacity (valence band top is typically less than 1.4eV) and chemical stability.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a lead-free bismuth-based mixed halogenated perovskite nanosheet and a preparation method and application thereof. The Sb doping improves the separation efficiency of the catalyst on the photo-generated carriers absorbed by visible light on one hand, and promotes the generation of holes on the other hand. At the same time, good size matching of Sb improves Cs₃Bi₂Br₉Stability of the perovskite material.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

lead-free bismuth-based mixed halogenated perovskite nanosheet with molecular formula of Cs₃Bi_2-xSb_xBr₉And x is less than or equal to 0.4 in the formula < 0 >.

Preferably, x is more than or equal to 0.1 and less than or equal to 0.3 in the molecular formula; further preferably, x is 0.2.

The invention also provides a preparation method of the lead-free bismuth-based mixed halogenated perovskite nanosheet, which comprises the following steps:

(1) according to a set molar ratio, CsBr and BiBr are added₃And SbBr₃Dissolving in DMSO to obtain precursor solution;

(2) adding the precursor liquid obtained in the step (1) into isopropanol, crystallizing for 0.5-5 min by an anti-solvent method, and washing and drying to obtain Cs₃Bi_2-xSb_xBr₉Nanosheets.

Preferably, the BiBr in step (1)₃And SbBr₃The molar ratio of (1.7: 0.3) - (1.9: 0.1), and the concentration of CsBr in DMSO is 10-20 mM.

Further preferably, the BiBr is₃And SbBr₃The molar ratio of (A) to (B) is 1.8: 0.2.

Preferably, the volume ratio of the precursor liquid to the isopropanol in the step (2) is 1: 20-1: 30.

Preferably, in the step (2), the Cs is obtained by washing with chloroform and then drying in a vacuum oven at 60 ℃ for 10 hours₃Bi_2-xSb_xBr₉Nanosheets.

The invention also provides application of the lead-free bismuth-based mixed halogenated perovskite nanosheet in photocatalysis of C (sp)³) -H bond activation reaction.

The invention adopts Bi and Sb as B-site cations in halide perovskite, wherein Bi is used as a main element, Sb is used as an auxiliary element, and the mixed halide perovskite nanosheet is synthesized by an anti-solvent recrystallization method. The inventors have found that during the anti-solvent process, the crystallization time needs to be strictly controlled so as not to form large crystal particles and not to obtain the nanoplatelets of the present invention. The invention is realized by adding Cs₃Bi₂Br₉A small amount of Sb is introduced to replace part of Bi, and the doping of Sb improves the separation efficiency of the catalyst on the photo-generated carriers absorbed by visible light on one hand and promotes the generation of holes on the other hand. At the same time, good size matching of Sb improves Cs₃Bi₂Br₉Stability of the perovskite material.

Compared with the prior art, the invention has the advantages that:

the invention prepares Cs by a simple anti-solvent recrystallization method₃Bi_2-xSb_xBr₉Nanosheet, introduction of Sb increases Cs₃Bi₂Br₉Visible light absorption capability and photogenerated carrier separation efficiency. Good size matching of Sb improves Cs₃Bi₂Br₉Stability of the perovskite material. A small amount of Sb doping promotesC(sp³) The H bond activates the generation of a hole of a key active species.

Drawings

FIG. 1 shows Cs samples obtained in comparative example 1, example 1 and comparative examples 2 to 4₃Bi₂Br₉(a)、Cs₃Bi_1.8Sb_0.2Br₉(b)、Cs₃Bi_1.5Sb_0.5Br₉(c)、Cs₃Bi_0.7Sb_1.3Br₉(d)、Cs₃Sb₂Br₉(e) SEM image of (d).

FIG. 2 is an SEM photograph of samples prepared in example 1(a), comparative example 5(b), and comparative example 6 (c).

FIG. 3 is an SEM photograph of samples prepared in example 1(a), comparative example 7(b), and comparative example 8 (c).

FIG. 4 shows Cs samples obtained in comparative example 1, example 1 and comparative examples 2 to 4₃Bi₂Br₉、Cs₃Bi_1.8Sb_0.2Br₉、Cs₃Bi_1.5Sb_0.5Br₉、Cs₃Bi_0.7Sb_1.3Br₉、Cs₃Sb₂Br₉XRD pattern of (a).

FIG. 5 shows Cs samples obtained in comparative example 1, example 1 and comparative examples 2 to 4₃Bi₂Br₉、Cs₃Bi_1.8Sb_0.2Br₉、Cs₃Bi_1.5Sb_0.5Br₉、Cs₃Bi_0.7Sb_1.3Br₉、Cs₃Sb₂Br₉Performance testing of photocatalytic toluene oxidation.

FIG. 6 shows Cs obtained in comparative example 1 and example 1₃Bi₂Br₉、Cs₃Bi_1.8Sb_0.2Br₉Stability of the samples is compared.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.

The invention is based on the photocatalysis of C (sp)³) Evaluation of-H bond activationCs₃Bi_2-xSb_xBr₉Activity of the nanoplatelets. Firstly, dispersing 10mg of catalyst into 5mL of reaction substrate; the mixture was magnetically stirred in the dark for 30min and oxygen (2mL min)^-1) The bottom of the reaction mixture was introduced and the adsorption-desorption equilibrium was established. A300W xenon lamp is adopted as a light source and is provided with a lambda filter with the wavelength being more than or equal to 400 nm. Quantitative analysis was carried out by gas chromatography using an internal standard method.

Example 1

Cs₃Bi_1.8Sb_0.2Br₉Preparing a nano sheet:

0.45mmol CsBr and 0.075mmol SbBr₃And 0.225mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_1.8Sb_0.2Br₉Nanosheets.

Comparative example 1

Cs₃Bi₂Br₉Preparing a nano sheet:

adding 0.45mmol CsBr and 0.30mmol BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi₂Br₉Nanosheets.

Comparative example 2

Cs₃Bi_1.5Sb_0.5Br₉Preparing a nano sheet:

0.45mmol CsBr and 0.150mmol SbBr₃And 0.150mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_1.5Sb_0.5Br₉Nanosheets.

Comparative example 3

Cs₃Bi_0.7Sb_1.3Br₉Preparing nano particles:

0.45mmol CsBr and 0.225mmol SbBr₃And 0.075mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_0.7Sb_1.3Br₉And (3) nanoparticles.

Comparative example 4

Cs₃Sb₂Br₉Preparing nano particles:

0.45mmol CsBr and 0.30mmol SbBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi₂Br₉And (3) nanoparticles.

Comparative example 5

Cs₃Bi_1.8Sb_0.2Br₉Preparing nano particles:

0.45mmol CsBr and 0.075mmol SbBr₃And 0.225mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 180 min. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_1.8Sb_0.2Br₉And (3) nanoparticles.

Comparative example 6

Cs₃Bi_1.8Sb_0.2Br₉Preparing nano particles:

0.45mmol CsBr and 0.075mmol SbBr₃And 0.225mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 720 min. Washing with chloroform for three times, and drying in a vacuum oven at 60 deg.C for 10 hr to obtain yellowColor Cs₃Bi_1.8Sb_0.2Br₉And (3) nanoparticles.

Comparative example 7

Cs₃Bi_1.8Sb_0.2Br₉Preparing nano particles:

2.25mmol CsBr, 0.375mmol SbBr₃And 1.125mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_1.8Sb_0.2Br₉And (3) nanoparticles.

Comparative example 8

Cs₃Bi_1.8Sb_0.2Br₉Preparing nano particles:

4.5mmol CsBr, 0.75mmol SbBr₃And 2.25mmol of BiBr₃Dissolved in 30mL of DMSO to obtain a precursor liquid. Then, 2mL of precursor was added to 50mL of isopropanol with vigorous stirring, and stirred rapidly for 1 minute. Washed three times with chloroform and dried in a vacuum oven at 60 ℃ for 10 hours to obtain yellow Cs₃Bi_1.8Sb_0.2Br₉And (3) nanoparticles.

Performance evaluation:

by photocatalysis of C (sp)³) H bond activation the catalytic activity of the prepared samples was investigated for model reactions:

10mg of the sample was dispersed in 5mL of toluene. The mixture was magnetically stirred in the dark for 30min and oxygen (2mL min)^-1) The bottom of the reaction mixture was introduced and the adsorption-desorption equilibrium was established. A300W xenon lamp is adopted as a light source and is provided with a lambda filter with the wavelength being more than or equal to 400 nm. The amounts of reactants and products were determined by internal standard method with n-decane as internal standard. Quantitation was performed on a Shimadzu GC2010Plus chromatograph equipped with a FID detector and a WAX capillary column (30 m. times.0.25 mm. times.0.25 μm).

The results of the photocatalytic toluene oxidation reaction of the samples obtained in example 1 and comparative examples 1 to 4 are shown in table 1:

TABLE 1 results of photocatalytic toluene oxidation reaction of samples prepared in example 1 and comparative examples 1 to 4

As is clear from Table 1, different toluene conversion rates were obtained at different molar ratios of Bi and Sb, wherein the molar ratio of Bi to Sb was 1.8:0.2, and the formation rates of benzaldehyde and benzyl alcohol were 4.033mmol g^-1h^-1And 1.779mmol g^-1h^-1The best photocatalysis effect.

TABLE 2 results of photocatalytic toluene oxidation reaction of samples obtained in example 1 and comparative examples 5 to 6

As can be seen from Table 2, different toluene conversion rates were obtained at different crystallization times, wherein the benzaldehyde and benzyl alcohol formation rates at 1min were 4.033mmol g^-1h^-1And 1.779mmol g^-1h^-1The best photocatalysis effect.

TABLE 3 results of photocatalytic toluene oxidation reaction of samples obtained in example 1 and comparative examples 7 to 8

As can be seen from Table 3, CsBr concentration in DMSO gave different toluene conversion rates, wherein the benzaldehyde and benzyl alcohol formation rates were 4.033mmol g for 1min^-1h^-1And 1.779mmol g^-1h^-1The best photocatalysis effect.

Toluene derivatives having other substituents were tested on the samples prepared in example 1, and the results are shown in Table 4:

TABLE 4 results of photocatalytic oxidation of toluene derivatives for samples obtained in example 1

Note:^areaction conditions are as follows: 5mL substrate, 10mg Cs₃ Bi_1.8Sb_0.2Br₉As photocatalyst, lambda is more than or equal to 400nm, O₂(2mL·min^-1) And the reaction time is 3 hours.^bSolid p-nitrotoluene (3.225g, relative density 1.29g mL)^-1) Dissolved in 2.5mL acetonitrile for reaction.

As shown in FIG. 1a, Cs₃Bi₂Br₉In the form of nanoplates, having a thickness of about 20 nm. Substituted by small amounts of Sb (Cs)₃Bi_1.8Sb_0.2Br₉And Cs₃Bi_1.5Sb_0.5Br₉) The sheet structure can be maintained (fig. 1b and 1 c). However, the content of Sb, Cs, was further increased₃Bi_0.7Sb_1.3Br₉Shown as nanoparticles (FIG. 1d), this is in contrast to pure Cs₃Sb₂Br₉(FIG. 1e) are identical.

As shown in FIG. 2, Cs at different crystallization times₃Bi_1.8Sb_0.2Br₉The morphology of (A) is very different. Crystallization 1min for nanoplatelets (2a), crystallization 180min for nanoparticles (2b), and crystallization 700min for larger nanoparticles (2 c).

As shown in FIG. 3, the Cs obtained at different concentrations of CsBr in DMSO₃Bi_1.8Sb_0.2Br₉The morphology of (A) is very different. Nanosheets (3a) at a concentration of 15mM, nanoparticles (3b) at a concentration of 75mM and nanoparticles (3c) of larger size at a concentration of 150 mM.

As shown in FIG. 4a, with Cs₃Bi₂Br₉In contrast, Cs increased with Sb content₃Bi₂Br₉The diffraction peaks in (003), (300) and (220) gradually decrease in position and are in Cs₃Sb₂Br₉Middle disappearance (Miao Xiao)While the characteristic peaks of (022) and (204) are at a larger angle (fig. 4 b).

As shown in FIG. 5, the conversion of toluene was dependent on Sb³⁺The increase in (c) increases first and then decreases. In Cs₃Bi_1.8Sb_0.2Br₉The nano-sheet has the highest conversion rate which reaches 5813 mu mol h^-1g^-1The selectivity of benzaldehyde and benzyl alcohol was 69.4% and 30.6%, respectively, and Cs₃Bi_1.8Sb_0.2Br₉Respectively about pure Cs₃Sb₂Br₉And Cs₃Bi₂Br₉5.1 and 2.1 times.

As shown in FIG. 6, the cycling experiment showed that Cs₃Bi_1.8Sb_0.2Br₉The original activity retained after 4 cycles was over 77%, while Cs₃Bi₂Br₉Only 50% of its original activity was retained.