Method for regulating photocatalytic performance of metal halide perovskite by alkali metal A-site doping

Abstract

The application discloses a method for regulating and controlling metal halide perovskite photocatalytic performance by alkali metal A site doping, and different proportions of alkali metal ions are doped into halide perovskite to improve the metal halide perovskite photocatalytic performance; the halide perovskite is CsPbCl3, CsPbBr3, CsPbI3, CsPbCl 3‑x Br x 3 or CsPbBr 3‑x I x 3; the alkali metal ion is Li + , Na + , K + or Rb + ; the application improves the photocatalytic hydrogen production performance by changing the doped metal and the doping proportion, and realizes the conversion from light energy to chemical energy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalysis, in particular to a method for regulating the photocatalytic performance of metal halide perovskite by alkali metal A-site doping. BACKGROUND

[0002] Hydrogen energy has the advantages of high energy density, cleanliness, renewability, system integration, energy storage, etc. These advantages make hydrogen energy an important choice for future energy system transformation, thereby promoting sustainable development and reducing dependence on limited fossil energy. However, one of the biggest challenges currently faced is the preparation of hydrogen energy from renewable energy. Photocatalytic hydrogen production technology effectively utilizes solar energy as the only input energy, and realizes hydrogen production under green and mild conditions, which has a wide application prospect.

[0003] Metal halide perovskite materials (ABX3) are considered to have great application potential in the field of photocatalytic hydrogen production due to their simple synthesis method and excellent photoelectric properties, such as long carrier diffusion length, adjustable band gap width, etc. However, instability and low photocatalytic efficiency hinder their further application in the field of photocatalysis, so many researchers have used various methods to improve their stability and photocatalytic efficiency, such as heterojunction engineering, doping engineering, surface modification engineering, etc. Among them, doping is one of the easiest and most convenient methods. For example, in 2020, researchers reported that lead-free perovskite crystals Cs3Bi 2x Sb 2-2x I9(x=0.1-0.9) in HI solution, compared with undoped Cs3Bi2I9, Cs3Sb2I9, Sb doping reduces the influence of Bi vacancies on the band structure, thereby increasing its light absorption, greatly improving the photocatalytic performance, and when x=0.03, it has the optimal photocatalytic performance. In 2021, a series of Pt 4+ doped, Cs2Pt x Sn 1-x Cl6 perovskite crystals (0≤x≤1), by changing the doping amount of Pt 4+ , the photocatalytic activity of the perovskite crystal can be regulated. When x=0.05, Cs2Pt x Sn 1-x Cl6 has the best photocatalytic hydrogen production performance and good stability.

[0004] In summary, by using metal doping technology to improve the photocatalytic performance of metal halide perovskite, research has focused on B-site doping, while A-site doping is a monovalent metal. There is no report on the application of alkali metal doping A-site to the field of photocatalysis. SUMMARY

[0005] In order to overcome the defects of the prior art, the present application aims to provide a method for regulating the photocatalytic performance of metal halide perovskite by alkali metal A-site doping, which has excellent photocatalytic hydrogen production capacity by optimizing the doping metal and the doping ratio.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A method for regulating the photocatalytic performance of metal halide perovskite by alkali metal A-site doping, different proportions of alkali metal ions are doped into halide perovskite to improve the photocatalytic performance of metal halide perovskite.

[0008] The halide perovskite is CsPbCl3, CsPbBr3, CsPbI3, CsPbCl 3-x Br x or CsPbBr 3-x I x .

[0009] The alkali metal ion is Li + , Na + , K + or Rb + .

[0010] The different proportions of doped alkali metal ions are obtained by anti-solvent precipitation.

[0011] The different proportions are 4.8-16.7% by mass.

[0012] The optimal doping mass ratio is 11.1%.

[0013] The present application has the following advantages:

[0014] (1) The present application dopes alkali metal ions into halide perovskite, which has some unique properties due to the active electrons in the outermost layer of alkali metals, such as strong metallic properties and strong reducing properties, so they become feasible and popular doping elements in the field of doping; alkali metals can induce photocatalyst charge redistribution, thereby promoting the separation of photo-generated carriers, the adsorption and activation of reactants, and the optimization of reaction pathways; alkali metal doping can be achieved by simple experimental techniques, which provides the possibility for further application.

[0015] (2) The halide perovskite doped in the present application is used for photocatalytic hydrogen production reaction, which can improve the hydrogen production efficiency by several times, and the system composition is simple, the operation is simple, the reaction conditions are mild, and the produced hydrogen can alleviate the environmental and energy problems. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 CsPbBr3 and Cs0.889 K 0.111 UV-Vis absorption spectrum of PbBr3.

[0017] Figure 2 CsPbBr3, Cs 0.889 K 0.111 Steady-state fluorescence spectrum of PbBr3, where the excitation wavelength λ = 400 nm.

[0018] Figure 3 CsPbBr3, Cs 1-x K x X-ray crystal powder diffraction pattern (XRD) of PbBr3(x = 0, 0.167, 0.111, 0.083, 0.048).

[0019] Figure 4 CsPbBr3, Cs 0.889 K 0.111 High-resolution XPS spectrum of K 2p in PbBr3.

[0020] Figure 5 CsPbBr3, Cs + Comparison of photocatalytic hydrogen evolution performance of doped CsPbBr3.

[0021] Figure 6 CsPbBr3, Cs 0.889 K 0.111 Variation of H2 generated by long-time light irradiation of the optimally doped CsPbBr3 and undoped CsPbBr3 powders under the same conditions.

[0022] Figure 7 CsPbBr3, Cs 0.889 K 0.111 Variation of H2 generated by cyclic light irradiation of the optimally doped CsPbBr3 and undoped CsPbBr3 powders under the same conditions.

[0023] Figure 8 Li + , Na + , Rb + Comparison of photocatalytic hydrogen evolution performance of doped CsPbBr3. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred embodiments and the accompanying drawings. Those skilled in the art should understand that the specific descriptions below are illustrative rather than limiting, and should not limit the scope of protection of the present application.

[0025] In the present application, the preparation method is a conventional method unless otherwise specified, and the raw materials used are available from public commercial channels unless otherwise specified. The percentages are mass percentages unless otherwise specified.

[0026] In the present application, the crystal structure of the halide perovskite is characterized by X-ray crystal powder diffraction (XRD); the optical properties of the material are characterized by ultraviolet-visible diffuse reflectance absorption spectroscopy and steady-state fluorescence spectroscopy; and the H2 produced by the system is qualitatively and quantitatively detected by gas chromatography.

[0027] In the present application, the halide perovskite is synthesized according to the method in the reference [Efficient and Selective Photocatalytic Oxidation of Benzylic Alcohols with Hybrid Organic-Inorganic Perovskite Materials. ACS Energy Letters 2018, 3, 755.], and on this basis, a series of alkali ion-doped halide perovskites (mainly including Li + , Na + , K + , Rb + ) are synthesized based on the anti-solvent precipitation method.

[0028] Example 1

[0029] Hereinafter, the synthesis of K + -doped CsPbBr3, i.e., Cs 1-x K x PbBr3(x = 0, 0.167, 0.111, 0.083, 0.048), is specifically described as an example, and the specific experimental steps include:

[0030] (1) CsPbBr3(x = 0) powder is prepared according to the method in the reference: 0.6380 g (3.0 mmol) of cesium bromide, 10 mL of DMSO (dimethyl sulfoxide) are added into a 100 mL beaker, and stirred until the solid is completely dissolved; then 10 mL of lead bromide solution (1.101 g of lead bromide is dissolved in 10 mL of DMF (N,N-dimethylformamide)) is added, and stirring is continued until the precursor solution is uniformly mixed, and 40 mL of ethyl acetate is added under stirring, at which time yellow solids are rapidly precipitated, and stirring is continued until complete reaction; post-treatment: the solution after reaction is centrifuged at 6000 rpm for 6 min, the supernatant is discarded, and the solid is washed twice with ethyl acetate to obtain a yellow solid, which is dried in a vacuum drying box.

[0031] (2) Based on the anti-solvent precipitation method, alkali ion-doped halide perovskite Cs 1-x Kx PbBr3(x = 0.048, 0.083, 0.111, 0.167) powder: 3.0 x (1 - x) mmol of cesium bromide was added into a 100 mL beaker, 10 mL of DMSO was added and stirred until the solid was completely dissolved; then 60 μΐ of potassium bromide aqueous solution (3.0 x x mmol of potassium bromide was dissolved in deionized water) was added, followed by 10 mL of lead bromide DMF solution (1.101 g of lead bromide was dissolved in DMF), and the stirring was continued until the precursor solution was mixed uniformly, and 40 mL of ethyl acetate was added under stirring, at which time yellow solid was precipitated rapidly, and the stirring was continued until the reaction was completed; post-treatment: the reaction solution was centrifuged at 6000 rpm for 6 min, the supernatant was discarded, and the solid was washed twice with ethyl acetate to obtain a yellow solid, which was then dried in a vacuum drying box.

[0032] The prepared Cs 1- x K x PbBr3(x = 0, 0.167, 0.111, 0.083, 0.048) were characterized by UV-Vis diffuse reflectance absorption spectra, steady-state fluorescence spectra, X-ray crystal diffraction, as shown in Figures 1-3 The presence of K + in the doped perovskite was characterized by high-resolution X-ray photoelectron spectroscopy, as shown in Figure 4 .

[0033] The photocatalytic hydrogen production performance of CsPbBr3with different K + doping ratios was compared, and the specific implementation method was as follows: 800 mg of Cs 1-x K x PbBr3(x = 0, 0.048, 0.083, 0.111, 0.167) powder was added into 8.6 mL of hydrobromic acid (48 wt.% aqueous solution), and stirred until the Cs 1-x K x PbBr3was dissolved in the hydrobromic acid and reached equilibrium, and then 2.25 mL of hypophosphoric acid was added into the photoreactor; the system was pumped to vacuum by a vacuum pump, and was irradiated by a 300 W xenon lamp (with a filter, wavelength ≥ 400 nm), and every 2 h, the system was automatically sampled to a gas chromatograph by the photoreaction system for quantitative detection of H2generated in the system. The results are shown in Figure 5 The doping of K + significantly improved the hydrogen production efficiency of the perovskite, and under the optimal doping ratio, x = 0.111, i.e. Cs 0.889 K 0.111 PbBr3, the hydrogen production efficiency could be improved by about 11 times, indicating that the photocatalytic performance of the halide perovskite could be significantly improved by doping K + at the A site.

[0034] 800mg of Cs doped in the optimal ratio 0.889 K 0.111 PbBr3 and undoped CsPbBr3 powders were subjected to prolonged light irradiation under the same conditions. For example... Figure 6 As shown, with the extension of illumination time, Cs 0.889 K 0.111 The photocatalytic hydrogen production efficiency of PbBr3 increases with time, indicating that doping with K... + The CsPbBr3 exhibited good stability. Furthermore, compared to undoped CsPbBr3, after 10 hours of illumination, the CsPbBr3 showed better stability. 0.889 K 0.111 PbBr3 can still improve hydrogen production efficiency by several times, indicating that changing the doping ratio can significantly regulate the photocatalytic hydrogen production performance of CsPbBr3.

[0035] 1.6g of Cs doped in the optimal ratio 0.889 K 0.111 PbBr3 and undoped CsPbBr3 powders were subjected to cyclic light irradiation experiments under the same conditions. Samples were taken every 4 hours, and after each sampling, the system was re-vacuumed before the next cycle. Figure 7 As shown, Cs 0.889 K 0.111 The fact that PbBr3 retained its initial hydrogen production activity after 5 cycles indicates that the doped halo-based perovskite has good stability.

[0036] Example 2

[0037] Using the same antisolvent precipitation method, Li was doped into CsPbBr3. + Na + 、Rb + Cs were obtained respectively 0.889 Li 0.111 PbBr3, Cs 0.889 Na 0.111 PbBr3, Cs 0.889 Rb 0.111 PbBr3 was used, and its photocatalytic hydrogen production performance was tested accordingly, following the same steps as in Example 1. 800 mg of Cs was added... 0.889 Li 0.111 PbBr3, Cs 0.889 Na 0.111 PbBr3, Cs 0.889 Rb 0.111 PbBr3 was subjected to illumination under the same conditions, and the results were as follows: Figure 8 As shown, compared with undoped CsPbBr3, doped Li + Na + 、Rb +The photocatalytic hydrogen production performance can also be improved.

[0038] In the application, the hydrogen production efficiency can be improved several times by doping alkali metal ions into halogen-based perovskite, the system composition is simple, the operation is simple, the reaction condition is mild, and the generated hydrogen can alleviate the environmental and energy problems.

[0039] The above examples of the application are only examples for clearly illustrating the application, and are not intended to limit the embodiments of the application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and all the embodiments cannot be exhausted here. Any obvious changes or variations derived from the technical solutions of the application still fall within the protection scope of the application.

Claims

1. A method for regulating the performance of hydrogen evolution of metal halide perovskite photocatalyst by alkali metal A-site doping, characterized in that, The alkali metal ion is doped into the halogen-based perovskite based on an anti-solvent precipitation method, and the molar ratio of the doping substance is 11.1%; The anti-solvent based precipitation method is specifically as follows: synthesizing alkali metal ion doped halogen-based perovskite Cs 1-x K x PbBr3 powder, 3.0 × (1-x) mmol of cesium bromide, 10 mL of DMSO were added into a 100 mL beaker, and stirring was performed until the solid was completely dissolved, x = 0.111; then 60 μL of potassium bromide aqueous solution, 10 mL of lead bromide DMF solution were sequentially added, stirring was continued until the precursor solution was uniformly mixed, and 40 mL of ethyl acetate was added under stirring, at which time yellow solid was rapidly precipitated, and stirring was continued until complete reaction; the solution after reaction was centrifuged at 6000 rpm for 6 min, the supernatant was discarded, and the solid was washed twice with ethyl acetate to obtain a yellow solid, which was then dried in a vacuum drying box; The alkali metal ion is K + ; The potassium bromide aqueous solution is 3.0 × x mmol of potassium bromide dissolved in deionized water; The DMF solution of lead bromide is 1.101 g of lead bromide dissolved in DMF.

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