Preparation method of S mechanism BiOBr / BiSBr heterojunction with interface shared Bi atomic layer

Abstract

This invention discloses a method for preparing an S-mechanism BiOBr / BiSBr heterojunction with a shared Bi atomic layer at the interface. Using choline bromide and polyethylene glycol as raw materials, a transparent, low-melting-point eutectic is obtained by heating. Bismuth chloride pentahydrate is then added, resulting in a light yellow BiOBr precipitate. The obtained BiOBr is transferred to a ceramic boat and placed in a tube furnace purged with nitrogen. Another ceramic boat is filled with sublimed sulfur and placed upstream of the nitrogen flow. The sample is heated and sulfided at a specific heating rate. Through an in-situ anion exchange-induced strategy, an S-mechanism oxygen-vacancy BiOBr / BiSBr heterojunction nanosheet photocatalyst with a shared Bi atomic layer at the interface is obtained. This photocatalyst exhibits excellent photocatalytic activity and stability in visible light-driven photocatalytic N2 fixation, photocatalytic degradation of organic pollutants in water, and selective photocatalytic reduction of organic matter.

Description

Technical Field

[0001] This invention belongs to the field of cutting-edge new materials and relates to a method for preparing an S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface. Specifically, it relates to a method for preparing an S-mechanism BiOBr / BiSBr heterojunction nanosheet photocatalytic material rich in oxygen vacancies by constructing S-Bi-O interface chemical bonds through an anion exchange-induced strategy. Background Technology

[0002] Nitrogen fixation, the conversion of atmospheric nitrogen into a bioavailable form, is crucial for the natural nitrogen cycle, industrial production, and human survival. While green technologies based on photocatalysis have successfully converted N2 to NH3 or NO3⁻, current research largely focuses on the half-reaction processes of N2 reduction (NRR) or N2 oxidation (NOR), often requiring sacrificial agents and auxiliary gases. This not only increases costs but also reduces energy conversion efficiency. Therefore, achieving "total nitrogen fixation" through photocatalysis—that is, a one-step reaction simultaneously converting N2 molecules into NH3 and NO3⁻ products—has proven to be an ideal strategy. However, single photocatalysts inevitably suffer from drawbacks such as high recombination rates of photogenerated carriers and insufficient redox potentials, resulting in low carrier utilization and unsatisfactory nitrogen fixation activity. Therefore, designing suitable composite photocatalysts to achieve highly efficient photocatalytic "total nitrogen fixation" performance is of great significance.

[0003] In recent years, heterojunction photocatalysts have shown significant application potential in the field of photocatalysis. Among them, the S-mechanism heterojunction, as a novel heterostructure, has attracted much attention due to its unique carrier separation mechanism and high redox potential. The S-mechanism heterojunction is formed by the close contact between a reduced semiconductor (RS) and an oxidized semiconductor (OS) to create a heterojunction interface. Under photoexcitation, photogenerated electrons and holes accumulate in the conduction band (CB) and valence band (VB) of the two semiconductor materials, respectively. Driven by the Fermi level difference, electrons transfer from the CB of OS to the VB of RS and recombine with holes, thus effectively retaining strongly reducing photogenerated electrons and strongly oxidizing holes. Therefore, the S-mechanism heterojunction is expected to become a key material system for photocatalytically driven nitrogen fixation. However, most existing S-mechanism heterojunction materials are obtained through conventional chemical synthesis or physical mixing, still facing challenges such as weak interfacial interactions and limited contact area. This leads to hindered interfacial charge transport, thus affecting photocatalytic efficiency. Therefore, designing and optimizing the interfacial structure to achieve rapid interfacial electron transport is an important goal in the development of S-mechanism heterojunctions.

[0004] To control the interface structure of S-mechanism heterojunctions, various strategies and design schemes have been proposed, including surface / interface functionalization and the introduction of electrostatic or van der Waals interactions. In particular, establishing chemical bonds at the interface can enhance the stability of the heterojunction structure and provide a fast channel for electron diffusion. However, the actual formation of chemical bonds is limited by the inherent constraints of the coordination saturation of interface atoms and the orbital mixing energy barrier, making it difficult to achieve uniform coverage of the entire interface.

[0005] To address the above problems, this invention proposes an in-situ anion exchange-induced strategy, namely, using anion S... 2 ⁻ Replacement of O in the [Bi₂O₂]²⁺ layer 2 ⁻, Constructing BiOBr / BiSBr heterojunctions rich in S-Bi-O interfacial chemical bonds. This in-situ transformation not only forms more uniform interfacial chemical bonds but also promotes electron cloud redistribution and enhances interfacial interactions, overcoming the limitations of traditional interfacial bonding in terms of bonding range and bonding strength, and preparing highly efficient photocatalysts. Summary of the Invention

[0006] This invention addresses the shortcomings of existing BiOBr / BiSBr heterojunctions, which involve complex and cumbersome processes, difficulty in achieving interfacial bonding at the BiOBr / BiSBr heterojunction interface, low carrier mobility, and poor long-term stability. It proposes a method for preparing an S-mechanism BiOBr / BiSBr heterojunction with a shared Bi atomic layer at the interface. The method is characterized by a BiOBr / BiSBr heterojunction rich in oxygen vacancies, possessing an S-mechanism carrier transfer pathway. This S-mechanism BiOBr / BiSBr heterojunction is formed through tight coupling via a shared Bi atomic layer at the interface, with the interfacial S-Bi-O bond serving as a rapid carrier transfer pathway. The preparation is achieved through an in-situ anion exchange-induced method, and the specific steps include the following: (1) Mix 0.01-1 mol choline bromide with 0.1-10 mol polyethylene glycol-200 uniformly and stir in an oil bath at 40-80 ℃ for 10-60 min to form a transparent low-melting-point eutectic. Then add 0.001-0.2 mol bismuth chloride pentahydrate to the low-melting-point eutectic system and stir to form a light yellow BiOBr precipitate. After stirring for 0.5-1 h, wash the precipitate three times with deionized water and ethanol, and then dry it in a vacuum oven at 40-60 ℃ to obtain BiOBr. (2) Transfer 0.05-1.0 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.005-0.3 g of sublimed sulfur at a distance of 3-6 cm upstream of the sample in the nitrogen flow. Heat to 250-400 ℃ at a heating rate of 2-10 ℃ / min and then hold for 15-120 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0007] The advantages of this invention are as follows: Based on the preparation of BiOBr nanosheets, this method uses an in-situ anion exchange-induced method to obtain S-mechanism oxygen-vacancy BiOBr / BiSBr heterojunction nanosheets. Through tight coupling via a shared interface Bi atom layer, BiOBr / BiSBr heterojunction nanosheets with a shared interface Bi atom layer are obtained. Highly symmetrical Bi-6p... z Orbit and O-2p z and S-2p z Effective orbital overlap forms continuous S-Bi-O interfacial chemical bonds through σ-bond interactions, exhibiting strong orbital coupling and a low-barrier charge transport pathway, thereby promoting interfacial charge transfer. Atomic-level S-Bi-O channels, in conjunction with a built-in electric field, establish an S-mechanism redox pathway, thus maintaining the heterojunction's high redox potential. The synergistic effect of oxygen vacancies and the shared interfacial covalent layer significantly lowers the barrier to the rate-determining steps of the photochemical reaction, significantly enhancing the visible-light-driven photocatalytic nitrogen fixation performance of the BiOBr / BiSBr heterojunction, its photocatalytic degradation performance of organic pollutants in water, and its photocatalytic selective reduction performance of organic matter. Attached Figure Description

[0008] Figure 1 XRD patterns and two standard diffraction PDFs of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared by the method described in Example 1 of this invention, and three comparative samples.

[0009] Figure 2 SEM image of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface, prepared using the method described in Example 1 of this invention.

[0010] Figure 3 This is a TEM image of a BiOBr / BiSBr heterojunction with an interface-shared Bi atom layer prepared using the method described in Example 1 of this invention.

[0011] Figure 4 HRTEM image of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface, prepared using the method described in Example 1 of this invention.

[0012] Figure 5 STEM image (a) and elemental distribution map (be) of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface prepared by the method described in Example 1 of this invention.

[0013] Figure 6 XPS spectra of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention, and a comparative sample.

[0014] Figure 7 The image shows the ESR spectrum of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention.

[0015] Figure 8 To illustrate the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention, and the NH4+ of the comparative sample in a photocatalytic all-nitrogen fixation system. + Generation rate and NO3⁻ generation rate.

[0016] Figure 9 To assess the stability of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention during five full nitrogen fixation reaction cycles. Detailed Implementation

[0017] The present invention will be further described in detail below through specific embodiments: Example 1 (1) 0.1 mol choline bromide and 0.8 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 60 ℃ for 30 min to form a transparent low-melting-point eutectic. Then, 0.01 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 40 ℃ to obtain BiOBr. (2) Transfer 0.1 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.03 g of sublimed sulfur 5 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 30 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0018] Example 2 (1) 0.1 mol choline bromide and 0.8 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 60 ℃ for 30 min to form a transparent low-melting-point eutectic. Then, 0.01 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 40 ℃ to obtain BiOBr. (2) Transfer 0.1 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.01 g of sublimed sulfur 5 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 30 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0019] Example 3 (1) 0.1 mol choline bromide and 0.8 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 60 ℃ for 30 min to form a transparent low-melting-point eutectic. Then, 0.01 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 40 ℃ to obtain BiOBr. (2) Transfer 0.1 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.05 g of sublimed sulfur 5 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 30 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0020] Example 4 (1) 0.01 mol choline bromide and 0.1 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 40 ℃ for 10 min to form a transparent low-melting-point eutectic. Then, 0.001 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 0.5 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 50 ℃ to obtain BiOBr. (2) Transfer 0.05 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.005 g of sublimed sulfur 3 cm upstream of the sample in the nitrogen flow. Heat to 250 °C at a heating rate of 2 °C / min and hold for 60 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0021] Example 5 (1) 1 mol of choline bromide and 10 mol of polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 80 ℃ for 60 min to form a transparent low-melting-point eutectic. Then, 0.2 mol of bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 60 ℃ to obtain BiOBr. (2) Transfer 1.0 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.3 g of sublimed sulfur 6 cm upstream of the sample in the nitrogen flow. Heat to 400 °C at a heating rate of 10 °C / min and hold for 15 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0022] Example 6 (1) 0.5 mol choline bromide and 6 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 70 ℃ for 30 min to form a transparent low-melting-point eutectic. Then, 0.1 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 0.5 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 50 ℃ to obtain BiOBr. (2) Transfer 0.4 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.03 g of sublimed sulfur 4 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 120 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0023] Example 7 (1) 0.2 mol choline bromide and 1.2 mol polyethylene glycol-200 were mixed evenly and stirred in an oil bath at 60 ℃ for 45 min to form a transparent low-melting-point eutectic. Then, 0.03 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system. After stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 50 ℃ to obtain BiOBr. (2) Transfer 0.2 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.08 g of sublimed sulfur 5 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 60 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

[0024] 0.1 mol choline bromide and 0.8 mol polyethylene glycol-200 were uniformly mixed and stirred in an oil bath at 60 °C for 30 min to form a transparent low-melting-point eutectic. Then, 0.01 mol bismuth chloride pentahydrate was added to the low-melting-point eutectic system, and after stirring, a light yellow BiOBr precipitate was formed. After stirring for 1 h, the precipitate was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 40 °C to obtain BiOBr.

[0025] 0.1 g of BiOBr prepared in step (1) of Example 1 was transferred into a ceramic boat and spread evenly on the bottom of the boat. The ceramic boat was placed in the center of a tube furnace with nitrogen flow. Under the nitrogen atmosphere, the temperature was increased to 300 °C at a heating rate of 5 °C / min and then held for 30 min to obtain a BiOBr sample rich in oxygen vacancies.

[0026] Transfer 0.1 g of BiOBr prepared in step (1) of Example 1 to a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.2 g of sublimed sulfur 5 cm upstream of the sample in the nitrogen flow. Heat to 300 °C at a heating rate of 5 °C / min and hold for 30 min to obtain the BiSBr sample.

[0027] Figure 1XRD patterns and two standard diffraction PDFs of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention and three comparative samples were obtained. Comparison with standard diffraction cards revealed that the diffraction peaks of Comparative Example 1 and Comparative Example 2 matched those of tetragonal BiOBr (JCPDS: 09-0393), while the diffraction peaks of Comparative Example 3 matched those of orthorhombic BiSBr (JCPDS: 97-003-1389). The sample in Example 1 simultaneously exhibited characteristic peaks of both tetragonal BiOBr and orthorhombic BiSBr, confirming the formation of the BiOBr / BiSBr heterojunction in Example 1.

[0028] Figure 2 This is a SEM image of a BiOBr / BiSBr heterojunction with an interface-shared Bi atom layer prepared using the method described in Example 1 of this invention. Figure 2 As can be seen, the BiOBr / BiSBr heterojunction sample exhibits a regular nanosheet structure with a width ranging from 100 to 300 nm. This unique nanosheet structure not only shortens the carrier diffusion distance but also provides a large number of alternative sites for anion substitution reactions.

[0029] Figure 3 This is a TEM image of a BiOBr / BiSBr heterojunction with an interface-shared Bi atom layer prepared using the method described in Example 1 of this invention. Figure 3 Further confirmation revealed that the BiOBr / BiSBr heterojunction sample exhibits an ultrathin nanosheet structure with a thickness of approximately 6-8 nm.

[0030] Figure 4 HRTEM image of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface, prepared using the method described in Example 1 of this invention. Figure 4 The image shows two sets of lattice fringes at 0.28 nm and 0.34 nm, corresponding to the interplanar spacing of the (102) and (111) crystal planes of BiOBr, respectively. The interlacing of the two sets of lattice fringes confirms the formation of a tightly coupled BiOBr / BiSBr heterointerface. Furthermore, the discontinuous lattice fringes indicate the generation of oxygen vacancies in BiOBr. Since no additional Bi³⁺ ions are introduced during the sulfidation reaction, this provides the possibility for the formation of S-Bi-O interfacial chemical bonds and the sharing of Bi atomic layers at the interface.

[0031] Figure 5STEM images (a) and corresponding elemental distribution maps (be) of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface prepared by the method described in Example 1 of this invention are shown. The images show that bismuth, oxygen, bromine, and sulfur are uniformly distributed, confirming the generation of BiSBr on the surface of the BiOBr nanosheets via anion exchange.

[0032] Figure 6 XPS spectra of the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention, and a comparative sample. Figure 6 Figures a and 6b show a comparison of the fine spectra of Br 3d and Bi 4f for Comparative Example 2 BiOBr, Example 1 BiOBr / BiSBr, and Comparative Example 3 BiSBr. The binding energies at the fitted peaks of 67.9 eV and 68.8 eV were determined to be Br 3d5 / 2 and Br 3d3 / 2, respectively. In the fine spectrum of Bi 4f, the peaks at 159.1 eV and 164.3 eV were attributed to Bi 3+ The Bi 4f7 / 2 and Bi 4f5 / 2 energy levels ( Figure 6 b) Low-valence Bi appearing in the low binding energy region of Bi 4f (3-β)+ This is related to oxygen vacancies. Compared to Comparative Example 2 BiOBr, the Br 3d and Bi 4f peaks in Example 1 BiOBr / BiSBr and Comparative Example 3 BiSBr are shifted to lower binding energies. This phenomenon can be attributed to the electron aggregation effect around Br and Bi atoms after the oxygen atom is replaced by the less electronegative sulfur atom. Since the binding energy position of the S 2p peak is very close to that of the Bi 4f peak, a high-resolution S 2s spectrum at 225.7 eV is provided for accurate analysis. Figure 6 c). In addition, such as Figure 6 As shown in Figure d, the O 1s spectrum exhibits peaks at 529.7 eV, 531.2 eV, and 532.7 eV, attributed to lattice oxygen (Bi-O), oxygen vacancies (Ov), and adsorbed oxygen, respectively. XPS spectroscopy further confirms that the introduction of sublimated sulfur triggers anion exchange reactions, leading to a transformation of the bismuth coordination environment from O to O vacancies and then to S. Furthermore, the S 2s spectrum of Example 1 shows a significant positive shift in binding energy, while the O 1s binding energy shows a corresponding negative shift. This change in binding energy indicates a strong electronic interaction at the heterostructure interface of Example 1, which forms an internal electric field in the BiSBr to BiOBr direction, conforming to the band matching rules of the S-mechanism heterostructure.

[0033] Figure 7 The image shows the ESR spectrum of the S-mechanism BiOBr / BiSBr heterojunction with a shared Bi atom layer at the interface, prepared using the method described in Example 1 of this invention. Figure 7It can be seen that there is a strong peak at g = 2.001, which is a characteristic peak of oxygen vacancies, indicating that BiOBr / BiSBr is rich in oxygen vacancies.

[0034] Figure 8 To illustrate the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers prepared using the method described in Example 1 of this invention, and the NH4+ of the comparative sample in a photocatalytic all-nitrogen fixation system. + The formation rates of nitrogen (NO3⁻) and nitrogen (NO3⁻) were evaluated. The photocatalytic performance of this catalyst under visible light irradiation was assessed. Figure 8 As shown, because oxygen vacancies broaden the visible light absorption range, the oxygen-vacancy-rich Comparative Example 2 sample exhibits higher NH4 content compared to the Comparative Example 1 sample. + and NO3 ‒ Yields. Furthermore, the BiOBr / BiSBr heterojunction photocatalyst of Example 1, formed through an interface-shared Bi atomic layer, further improved the yields of NH4⁺ and NO3⁻, reaching 116.3 µmol·g⁻¹·h⁻¹ and 71.9 µmol·g⁻¹·h⁻¹, respectively, which are 3.6 times and 5.4 times that of the Comparative Example 1 sample. This facilitates the rapid and simultaneous utilization of reducing electrons and oxidizing holes.

[0035] Figure 9 The stability of the S-mechanism BiOBr / BiSBr heterojunction prepared using the method described in Example 1 of this invention was tested during five full nitrogen fixation reaction cycles. As shown in the figure, after 30 hours of five full nitrogen fixation reaction cycles, the NH4⁺ production remained essentially unchanged, indicating that the S-mechanism BiOBr / BiSBr heterojunction nanosheets with shared Bi atomic layers at the interface are suitable for photocatalytic full nitrogen fixation to NH4⁺ production. + It has excellent stability.

[0036] The S-mechanism BiOBr / BiSBr heterojunction nanosheets with shared Bi atomic layers prepared by the method described in Example 1 of this invention were used for the photocatalytic degradation of organic dyes in aqueous solution. The results showed that they also had a good degradation and removal effect on organic dyes in water and could be used for the treatment of organic wastewater.

[0037] The S-mechanism BiOBr / BiSBr heterojunction nanosheets with shared Bi atomic layers prepared by the method described in Example 1 of this invention also exhibit excellent photocatalytic redox selectivity when used for selective photocatalytic redox of small molecule organic compounds.

[0038] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, substitutions, simplifications, etc. made without departing from the principle and process of the present invention are equivalent substitutions and should be included within the protection scope of the present invention.

Claims

1. A method for preparing a BiOBr / BiSBr heterojunction with a shared Bi atomic layer at the interface, characterized in that... The BiOBr / BiSBr heterojunction is rich in oxygen vacancies and possesses an S-mechanism carrier transfer pathway. This S-mechanism BiOBr / BiSBr heterojunction is formed through tight coupling via a shared Bi atom layer at the interface, with the interface S-Bi-O bond serving as a rapid carrier transfer pathway. It is prepared via an in-situ anion exchange-induced method, specifically including the following steps: (1) Mix 0.01-1 mol choline bromide with 0.1-10 mol polyethylene glycol-200 uniformly and stir in an oil bath at 40-80 ℃ for 10-60 min to form a transparent low-melting-point eutectic. Then add 0.001-0.2 mol bismuth chloride pentahydrate to the low-melting-point eutectic system and stir to form a light yellow BiOBr precipitate. After stirring for 0.5-1 h, wash the precipitate three times with deionized water and ethanol, and then dry it in a vacuum oven at 40-60 ℃ to obtain BiOBr. (2) Transfer 0.05-1.0 g of BiOBr prepared in step (1) into a ceramic boat and spread it evenly on the bottom of the boat. Place the ceramic boat in the center of a tube furnace with nitrogen flow. Place another ceramic boat containing 0.005-0.3 g of sublimed sulfur at a distance of 3-6 cm upstream of the sample in the nitrogen flow. Heat to 250-400 ℃ at a heating rate of 2-10 ℃ / min and then hold for 15-120 min to obtain the S-mechanism BiOBr / BiSBr heterojunction with shared Bi atomic layers at the interface.

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