Preparation method and application of porous BiOCl1-xBrx / BiOBr1-xClx nanosheet

Abstract

The invention provides porous BiOCl < 1-x > Br < x > / BiOBr < 1-x > Cl < x > composite nanosheet powder as well as a preparation method and photoelectric property application thereof.The method comprises the following steps: preparing BiOCl nanosheet powder by adopting a hydrothermal method, adding a H2O2 solution with the mass fraction of 30% into deionized water to form a solution A, adding an HBr solution with the mass fraction of 40% into deionized water to obtain a solution B, and performing hydrothermal reaction on the solution A and the solution B to obtain the porous BiOCl < 1-x > Br < x > / BiOBr < 1-x > Cl < x > composite nanosheet powder; and pouring the BiOCl nanosheet powder into a solution C obtained by fully mixing the solution A and the solution B, stirring, centrifuging, washing and drying to obtain the porous BiOCl < 1-x > Brx / BiOBr < 1-x > Clx composite nanosheet powder. According to the method, the porous BiOCl < 1-x > Br < x > / BiOBr < 1-x > Cl < x > composite nanosheet powder can be obtained, the interior of the porous structure contains more Cl elements, and the exterior of the porous structure contains more Br elements; the prepared composite nanosheet powder has good photon-generated carrier separation and light absorption capabilities, and can generate stronger photoelectric response performance. And meanwhile, the preparation method is simple in process, low in raw material cost, non-toxic to the environment and easy for batch and large-scale production.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials and specifically relates to a porous BiOCl 1-x Br x / BiOBr 1-x Cl x Nanosheets, preparation methods and applications thereof. Background Art

[0002] BiOBr is a common, non-toxic, environmentally friendly semiconductor material with a unique layered crystal structure. It has significant absorption of visible light and exhibits unique physical and chemical properties. It has good and broad application prospects in the fields of catalysis, antibacterial, and photoelectric detection.

[0003] Currently, the BiOBr that people have studied more often exists in the form of single-crystal nanosheets, but the recombination rate of photogenerated carriers in BiOBr nanosheets is still relatively high, and the photoelectrodes made from them have weak light absorption intensity. People have tried to solve this problem with different strategies. One aspect is that researchers have used different methods to prepare BiOCl / BiOBr composites to improve the photogenerated charge separation ability of BiOBr, such as hydrothermal method (Appl. Surf. Sci., 2019, 467-468: 505), solvothermal method (Applied Chemical Industry, 2021, 50(03): 675), liquid phase co-precipitation method (J. Nanopart. Res., 2023, 25:96), microwave-assisted reaction method (Ind. Eng. Chem. Res., 2015, 54: 9913), ultrasound-assisted reaction method (J.Cleaner Prod., 2020, 259: 120679.) and electrospinning method (Appl. Surf. Sci., 2016, 384: 192-199.). However, the BiOCl / BiOBr composite materials prepared by these methods mostly present a 3D structure in the form of nanoparticles, nanosheets, or a combination of the two. Although the heterojunction formed by the material composite improves the separation efficiency of photogenerated carriers, the light absorption capacity of the composite material still needs to be further improved. Therefore, exploring a preparation method for BiOCl / BiOBr composite materials with simple process, low cost, environmental friendliness and stronger light absorption capacity is of great significance for obtaining high photoelectric response performance. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a porous BiOCl 1-x Br x / BiOBr 1-x Cl xComposite nanosheet powder, preparation method thereof and application thereof, the method can obtain BiOCl composed of porous nanosheets 1-x Br x / BiOBr 1-x Cl x The composite material contains more Cl elements inside the porous structure and more Br elements outside the porous structure. The size of the pores on the nanosheets is 1~3um. The composite nanosheet powder contains both tightly contacted BiOCl 1-x Br x / BiOBr 1-x Cl x The heterojunction structure also includes a hole structure that can utilize the incident light to reflect multiple times inside the sample to improve the light energy utilization rate. These two characteristics make the BiOCl prepared by this invention 1-x Br x / BiOBr 1-x Cl x It has a significant photoelectric response enhancement effect.

[0005] The present invention provides a porous BiOCl 1-x Br x / BiOBr 1-x Cl x The preparation method of composite nanosheet powder comprises the following steps: BiOCl nanosheet powder was prepared by hydrothermal method; A 30% H2O2 solution was added to deionized water to obtain solution A; A 40% HBr solution was added to deionized water to obtain solution B; Solution A and solution B were mixed to obtain solution C. BiOCl powder prepared by hydrothermal method was added to solution C and stirred for a certain period of time to obtain a suspension. The suspension was washed by centrifugation with anhydrous ethanol and dried to obtain porous BiOCl. 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

[0006] Preferably, the mass fraction of the BiOCl nanosheet powder in solution C is 0.4% to 0.7%.

[0007] Preferably, the mass fraction of H2O2 in solution C is 3% to 4%.

[0008] Preferably, the mass fraction of HBr in solution C is 0.8% to 1.5%.

[0009] Preferably, the stirring time after the BiOCl nanosheet powder is added to solution C is 20-40 minutes.

[0010] Preferably, the drying temperature of the wet powder after centrifugal washing is 60-80 o C, drying time is 2~4h.

[0011] The present invention provides a porous BiOCl prepared by the preparation method described in the above technical solution 1-x Br x / BiOBr 1- x Cl x Composite nanosheet powder, the porous BiOCl 1-x Br x / BiOBr 1-x Cl x The inside of the porous structure of the composite nanosheet powder contains more Cl elements, and the outside of the porous structure contains more Br elements. The size of the pores is 1~3um.

[0012] The present invention provides a photoelectric response material, including the porous BiOCl prepared by the preparation method described in the above technical solution or the porous BiOCl described in the above technical solution. 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

[0013] The present invention provides a porous BiOCl 1-x Br x / BiOBr 1-x Cl x The preparation method of composite nanosheet powder uses BiOCl nanosheet powder obtained by common hydrothermal method as raw material, H2O2 as bismuth ion chelating agent to control the reaction speed of BiOCl nanosheet raw material, HBr as corrosive agent and bromine source, and the formula ratio of reactants is regulated. The porous BiOCl is obtained by reaction under liquid phase stirring at room temperature. 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

[0014] Compared with the prior art, the preparation method and the prepared porous BiOCl 1-x Br x / BiOBr 1- x Cl x Composite nanosheet powder has the following beneficial effects: First, the hydrothermal method used in the preparation method of the present invention utilizes BiOCl as the synthetic raw material, which exhibits good crystallinity, few defects, and slow corrosion rate, thus facilitating pore formation. However, BiOCl raw materials prepared at room temperature contain many defects. Due to the high activity of the defects, they corrode too quickly and fail to form a porous structure, thereby affecting the photoelectric response performance of the composite material.

[0015] Second, in the preparation method of the present invention, 30% by mass of H2O2 is used as Bi 3+ The mass fraction of H2O2 in the reaction solution is 3% to 4%. H2O2 is a green and cheap chelating agent and will not introduce other metal ions or non-metallic ion impurities other than Bi, Cl, Br, and O into the product. In the present invention, the mass fraction of H2O2 chelating agent in the reaction solution plays a key role. Not adding or too little H2O2 will cause the BiOCl raw material to corrode too quickly and fail to obtain a large number of porous structures. Adding too much will cause Bi 3+ It is tightly coordinated and cannot be released, and the yield of powder in the solution is low.

[0016] Third, in the preparation method described in the present invention, HBr, which accounts for 0.8% to 1%, plays the role of corroding BiOCl nanosheets and serving as a Br source. HBr corrodes holes in the center of the BiOCl nanosheets, and the corroded BiOCl decomposes and provides Bi 3+ OH - The synthesis of BiOBr with Br ions in HBr deposits on BiOCl and forms a heterojunction with BiOCl. The control of HBr concentration in the reaction is also very critical. Too little HBr will make the BiOBr nanosheets unable to be fully corroded, unable to generate a significant porous structure and more BiOBr phases that can absorb visible light, while too much HBr will make Bi 3+ In solution, [BiBr] 3- The porous BiOCl described in this patent application exists in a stable form and cannot undergo the formation reaction of the BiOBr phase. 1-x Br x / BiOBr 1-x Cl x The porous structure inside the composite nanosheet powder directly synergizes with the heterojunction formed on the nanosheet and the BiOBr distributed outside the pores, jointly affecting the light energy utilization rate of the composite nanosheet, significantly enhancing its photoelectric response performance compared to existing composite materials.

[0017] Fourth, the preparation method of the present invention can obtain BiOCl with a porous structure. 1-x Br x / BiOBr 1- x Clx The composite nanosheet powder has a pore size of 1 to 3 μm. The porous structure increases the contact area between the composite nanomaterial and visible light. At the same time, the porous structure is conducive to capturing visible light and causing the visible light to be reflected multiple times inside the pores, thereby improving the utilization rate of light energy. The porous BiOCl prepared by the preparation method of the present invention 1-x Br x / BiOBr 1-x Cl x The composite nanosheet powder has a stronger photoelectric response effect than the existing BiOCl / BiOBr composite material. At the same time, the preparation method of the present invention uses simple raw materials, is low in cost, is non-toxic to the environment, and is easy to mass-produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The porous BiOCl in this patent application 1-x Br x / BiOBr 1-x Cl x XRD analysis diagram of composite nanosheet powder; Figure 2 The porous BiOCl in this patent application 1-x Br x / BiOBr 1-x Cl x FESEM images of composite nanosheet powders; Figure 3 The porous BiOCl in this patent application 1-x Br x / BiOBr 1-x Cl x EDS line scan spectrum of composite nanosheet powder; Figure 4 The porous BiOCl in this patent application 1-x Br x / BiOBr 1-x Cl x Photoelectric response diagram of composite nanosheet powder; DETAILED DESCRIPTION

[0019] To further illustrate the present invention, the bismuth nanosheets, preparation methods and applications thereof provided by the present invention are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention. Example

[0020] 0.5 g of BiOCl nanosheet powder was prepared by hydrothermal method. 10 ml of 30% H2O2 solution was added to 40 ml of deionized water to form solution A. 1.7 ml of 40% HBr solution was added to 40 ml of deionized water to obtain solution B. Solution A and solution B were fully mixed to obtain solution C. The BiOCl nanosheet powder obtained by hydrothermal method was poured into solution C and stirred for 30 min to obtain a suspension. The suspension was centrifuged, the supernatant was discarded, and the wet precipitate was washed twice with an appropriate amount of anhydrous ethanol. The washed product was placed in 70 o C was dried in a forced air drying oven for 2 h to obtain porous BiOCl 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

[0021] By using the preparation method described in this patent application, a porous BiOCl with a strong photoelectric response effect can be obtained. 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder, the formation mechanism of the pore structure in the composite nanosheet powder is as follows: First, HBr corrodes the hydrothermal BiOCl nanosheets. + Attacking O in the surface lattice of BiOCl nanosheets 2- Lead to Bi 3+ and OH - Released from the surface of BiOCl nanosheets, if Bi 3+ Too much corrosion will cause Bi 3+ 、Cl - Br - OH - In the solution, it spontaneously nucleates and grows into nanosheets, which is not conducive to the formation of a large number of porous structures. If the free Bi in the solution is chelated by H2O2, 3+ The quantity is limited, then Bi 3+ A new phase will be formed around the unetched BiOCl with holes, thus forming a heterojunction with a porous structure.

[0022] FESEM scanning of the composite nanosheet powder prepared in this embodiment shows that the composite nanosheet has a porous nanosheet shape; EDS energy spectrum analysis of the inner and outer sides of the structure shows that the side close to the hole contains more Cl elements, while the side away from the hole contains more Br elements. Therefore, the chemical formula of the product obtained in the present invention is written as BiOCl 1-x Br x / BiOBr 1-x Clx , which means that the inner side of the pore structure is replaced by a small amount of Br atoms instead of Cl atoms in BiOCl 1-x Br x BiOBr is composed of a small amount of Cl atoms replacing Br atoms on the outside. 1-x Cl x Phase composition. Example

[0023] This example serves as a comparative experiment for Example 1. Compared with Example 1, H2O2 was not involved in the reaction during the preparation process. Specifically, 0.5 g of BiOCl nanosheet powder prepared by a hydrothermal method was taken, 1.7 ml of a 40% HBr solution was added to 90 ml of deionized water to obtain a reaction solution, the BiOCl nanosheet powder obtained by the hydrothermal method was poured into the solution, and the suspension was obtained after continuous stirring for 30 minutes. The suspension was centrifuged, the supernatant was discarded, and the wet precipitate was washed twice with an appropriate amount of anhydrous ethanol. The washed product was placed at 70 o The sample was dried in a forced-air drying oven at 400 °C for 2 h to obtain a control sample in which no H₂O₂ was added during the reaction. XRD analysis revealed that the composite nanosheet powder synthesized in this example was composed of BiOCl and BiOBr phases, but the diffraction peak corresponding to BiOCl was weak, indicating a low content of BiOCl in this sample. FESEM images also revealed that the composite nanosheet powder synthesized in this example had a less porous structure than the composite nanosheet powder in Example 1.

[0024] Figure 1 The porous BiOCl prepared in this example 1-x Br x / BiOBr 1-x Cl x XRD analysis of composite nanosheet powder. The BiOCl and BiOBr spectra at the bottom of the figure are two single-phase nanosheet powders obtained by the common hydrothermal method. The spectrum marked without H2O2 corresponds to the spectrum obtained by preparing only porous BiOCl 1-x Br x / BiOBr 1-x Cl x The sample data obtained by removing H2O2 during the composite nanosheet powder process (i.e., the composite nanosheet powder prepared in Example 2) can be seen that the porous BiOCl prepared in Example 1 1-x Br x / BiOBr 1-x Cl x The composite nanosheet powder is composed of BiOBr-based main phase and BiOCl-based secondary phase. Compared with the composite nanosheet powder prepared in Example 2, the porous BiOCl 1-x Brx / BiOBr 1-x Cl x There are more BiOCl subphases in the composite nanosheet powder, which is related to the effect of H2O2 on the Bi 3+ is related to the chelation effect.

[0025] Figure 2 It is porous BiOCl 1-x Br x / BiOBr 1-x Cl x FESEM image of composite nanosheet powder. Figure 2 (a) It can be seen that the BiOBr prepared in this example 1-x Cl x The material is in the shape of porous nanosheets with a pore size of 1~3um. Figure 2 (b) It can be seen that the sample without adding H2O2 during the preparation process contains fewer pores.

[0026] Figure 3 The EDS line scan energy spectrum of the inner and outer sides of the porous composite nanosheet shows that the Cl element is more on the side close to the hole and the Br element is more on the side away from the hole. Therefore, the chemical formula of the product obtained by the present invention is written as BiOCl 1-x Br x / BiOBr 1- x Cl x , which means that the inner side of the pore structure is replaced by a small amount of Br atoms instead of Cl atoms in BiOCl 1-x Br x BiOBr is composed of a small amount of Cl atoms replacing Br atoms on the outside. 1-x Cl x Phase composition.

[0027] Figure 4 The porous BiOCl prepared in Example 1 of the present invention 1-x Br x / BiOBr 1-x Cl x Photoelectric response effect of composite nanosheet powder. Different powder samples were made into photoelectrodes by drop coating, and their photoelectric response performance was tested using an electrochemical workstation under irradiation with simulated sunlight. As can be seen from the figure, since BiOCl prepared by the hydrothermal method is a semiconductor material that only absorbs ultraviolet light, its photoelectric response is weak, while BiOBr prepared by the hydrothermal method can absorb visible light and has a stronger photoelectric response. The photoelectric response of the sample without adding H2O2 during the preparation process is not much different from that of the single BiOBr, while the porous BiOCl prepared by the present invention 1-x Br x / BiOBr1-x Cl x The composite nanosheet powder has the strongest photoelectric response, which is mainly attributed to its unique heterojunction and porous structure. Example

[0028] 0.3 g of BiOCl nanosheet powder was prepared by hydrothermal method. 8 ml of 30% H2O2 solution was added to 30 ml of deionized water to form solution A. 1.6 ml of 40% HBr solution was added to 30 ml of deionized water to obtain solution B. Solution A and solution B were fully mixed to obtain solution C. The BiOCl nanosheet powder obtained by hydrothermal method was poured into solution C and stirred for 20 min to obtain a suspension. The suspension was centrifuged, the supernatant was discarded, and the wet precipitate was washed twice with an appropriate amount of anhydrous ethanol. The washed product was placed at 70 o C was dried in a forced air drying oven for 4 h to obtain porous BiOCl 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder. Example

[0029] 0.8 g of BiOCl nanosheet powder was prepared by hydrothermal method. 12 ml of 30% H2O2 solution was added to 50 ml of deionized water to form solution A. 1.9 ml of 40% HBr solution was added to 50 ml of deionized water to obtain solution B. Solution A and solution B were fully mixed to obtain solution C. The BiOCl nanosheet powder obtained by hydrothermal method was poured into solution C and stirred for 40 min to obtain a suspension. The suspension was centrifuged, the supernatant was discarded, and the wet precipitate was washed twice with an appropriate amount of anhydrous ethanol. The washed product was placed in 80 o C was dried in a forced air drying oven for 2 h to obtain porous BiOCl 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

[0030] By the BiOCl prepared in Example 3 and Example 4 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder X X-ray diffraction, field emission scanning electron microscopy and photoelectric response test characterization, the obtained BiOCl 1-x Br x / BiOBr 1-x Cl xThe composite nanosheet powder also has a pore structure similar to that of Example 1, and its photoelectric response is similar to that of Example 1 and stronger than that of the composite nanosheet powder obtained in Example 2.

[0031] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A porous BiOCl 1-x Br x / BiOBr 1-x Cl x The preparation method of composite nanosheet powder comprises the following steps: BiOCl nanosheet powder was prepared by hydrothermal method; A 30% H2O2 solution was added to deionized water to obtain solution A; A 40% HBr solution was added to deionized water to obtain solution B; Solution A and solution B were mixed to obtain solution C. BiOCl powder prepared by hydrothermal method was added to solution C and stirred for a certain period of time to obtain a suspension. The suspension was washed by centrifugation with anhydrous ethanol and dried to obtain porous BiOCl. 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder.

2. The preparation method according to claim 1, characterized in that The BiOCl nanosheet powder raw material is prepared by a hydrothermal method, and the mass fraction of the BiOCl nanosheet powder in solution C is 0.2% to 0.5%.

3. The preparation method according to claim 2, characterized in that Solution C contains H2O2, and the mass fraction of H2O2 in solution C is 3%~4%.

4. The preparation method according to claim 3, characterized in that Solution C contains HBr, and the mass fraction of HBr in solution C is 0.8%~1%.

5. The preparation method according to claim 4, characterized in that Add BiOCl powder to solution C and stir for 20-40 min.

6. The preparation method according to claim 5, characterized in that After the reaction under stirring conditions, the obtained precipitate was washed by centrifugation with anhydrous ethanol.

7. The preparation method according to claim 6, characterized in that The wet powder after centrifugal washing is dried in a blast drying oven at a drying temperature of 60-80 o C, drying time is 2~4h.

8. A porous BiOCl prepared by the preparation method according to any one of claims 1 to 7 1-x Br x / BiOBr 1-x Cl x Composite nanosheet powder, characterized in that: BiOCl in the composite nanomaterial 1-x Br x Phase and BiOBr 1-x Cl x Phases are located on the same nanosheet, BiOCl 1-x Br x The phase is mainly distributed on the side close to the pore, BiOBr 1-x Cl x The phase is mainly distributed on the side away from the pores, and the pore size is 1~3um.

9. A photoelectric material, characterized in that: Including the porous BiOCl 1-x Br x / BiOBr 1-x Cl x Nanosheet composite powder materials.

10. A porous BiOCl as claimed in claim 8 1-x Br x / BiOBr 1-x Cl x Application of composite nanosheet powders in photoelectric response.

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