Preparation method and application of Bi-BiO / BiOCl ternary Z-type heterojunction

Abstract

The application belongs to the field of photocatalytic environmental remediation, and particularly relates to a preparation method and application of a Bi-BiO / BiOCl ternary Z-type heterojunction. The preparation method comprises the following steps: S1, adding Bi(NO3)3.5H2O and PVP into a mannitol solution, then adding a sodium chloride solution dropwise, and then performing a hydrothermal reaction, and obtaining BiOCl nanosheets after cooling, centrifuging and washing the product; S2, mixing HNO3 solution, ethylene glycol and water to form a mixed solution, adding Bi(NO3)3.5H2O into the mixed solution and stirring until a transparent solution is formed, then adding the BiOCl nanosheets into the transparent solution to form a suspension; S3, performing a hydrothermal reaction on the suspension obtained in step S2, and obtaining the Bi-BiO / BiOCl ternary Z-type heterojunction after cooling, centrifuging, washing and drying the product. The Bi-BiO is loaded on the surface of the BiOCl through a two-step hydrothermal method to construct a Z-type heterojunction photocatalyst, which improves the photoelectron-hole separation capacity and light absorption range of the material, and further increases the oxygen vacancy concentration of the material, so that the Z-type heterojunction photocatalyst has excellent photocatalytic activity.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic environmental remediation, specifically relating to a method for preparing and applying a Bi-BiO / BiOCl ternary Z-type heterojunction. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Since the beginning of the 21st century, with the advancement of modern industrial large-scale production and the continuous growth of the global population, the demand for chemical products has been increasing daily, resulting in a large amount of organic pollutants that are difficult to degrade naturally. This trend has now impacted the natural environment and the human living environment. To address these problems, researchers have proposed numerous solutions, among which semiconductor photocatalysis technology is an effective strategy for utilizing solar energy to catalytically degrade organic pollutants. Its advantages, such as the use of non-toxic photocatalysts, low energy consumption in the photocatalytic degradation process, and high degradation efficiency, have made it stand out among many pollutant treatment technologies. The photocatalytic phenomenon was first discovered by Fujishima and Honda of the University of Tokyo. The TiO2 material used could decompose water into hydrogen and oxygen under ultraviolet light irradiation. Since then, TiO2 and related derivative catalysts have attracted a large number of scholars to study. However, with in-depth research, numerous studies have shown that TiO2 semiconductor materials have weak response to the visible light component of sunlight, and the high recombination rate of photogenerated electrons and holes leads to a low quantum yield, making it currently unsuitable for practical production. Therefore, researchers have begun to focus their photocatalysis research on the development of novel, highly efficient photocatalysts.

[0004] Bismuth oxychloride (BiOCl), as a novel bismuth-based photocatalyst, stands out among numerous semiconductor catalysts due to its high stability, suitable band structure, and typical layered structure, which give it highly efficient photocatalytic performance. Furthermore, BiOCl photocatalysts possess specific exposed crystal faces and surface oxygen vacancies, making them ideal model materials with significant research value. Although many researchers have made considerable efforts in studying BiOCl, its light absorption range and the recombination rate of photogenerated electrons and holes have not yet reached ideal levels. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a Bi-BiO / BiOCl ternary Z-shaped heterojunction. This invention utilizes a two-step hydrothermal method to load Bi-BiO onto the surface of BiOCl, constructing a Z-shaped heterojunction photocatalyst. This improves the photogenerated electron-hole separation capability and light absorption range of the material, and further increases the oxygen vacancy concentration, resulting in excellent photocatalytic activity for the Z-shaped heterojunction photocatalyst.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a Bi-BiO / BiOCl ternary Z-type heterojunction, comprising the following steps:

[0008] S1. Bi(NO3)3·5H2O and KCl were added to an appropriate amount of water and stirred evenly. Then, a hydrothermal reaction was carried out. After the hydrothermal reaction, the product was cooled, centrifuged, and washed to obtain BiOCl nanosheets.

[0009] S2. Mix HNO3 solution, ethylene glycol and water to form a mixture. Add Bi(NO3)3·5H2O to the mixture and stir until a transparent solution is formed. Then add BiOCl nanosheets to the transparent solution to form a suspension.

[0010] S3. The suspension obtained in step S2 is subjected to a hydrothermal reaction. After the hydrothermal reaction, the product is cooled, centrifuged, washed, and dried to obtain a Bi-BiO / BiOCl ternary Z-type heterojunction.

[0011] Preferably, in step S1, the ratio of Bi(NO3)3·5H2O, KCl and water is 1 mmol: 224-1491 mg: 10-40 mL.

[0012] Preferably, in step S1, the temperature of the hydrothermal reaction is 150-170℃ and the time is 1-24h.

[0013] Preferably, in step S2, the concentration of the HNO3 solution is 9.9-10.1 mol / L, and the volume ratio of HNO3 solution, ethylene glycol and water is 1:45-55:8-10.

[0014] Preferably, in step S2, the proportion of Bi(NO3)3·5H2O added to the mixture is 1-20 mg / mL.

[0015] Preferably, in step S2, the ratio of BiOCl nanosheets added to the transparent solution is 54-55 mg / mL.

[0016] Preferably, in step S3, the hydrothermal reaction temperature is 150-170℃ and the time is 10min-24h.

[0017] Preferably, in step S3, the centrifugation speed is 12500-13500 rpm; the washing method is to wash with deionized water 2-3 times first, and then wash with ethanol 2-3 times; the drying is vacuum drying at a temperature of 55-65℃ for 10-12 hours.

[0018] In a second aspect, the present invention provides a Bi-BiO / BiOCl ternary Z-type heterojunction, which is obtained by the preparation method described in the first aspect.

[0019] Thirdly, the present invention provides the application of the Bi-BiO / BiOCl ternary Z-type heterojunction as described in the first aspect in the photocatalytic degradation of organic pollutants, including methyl orange.

[0020] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0021] This invention employs a two-step hydrothermal method to load Bi-BiO onto the surface of BiOCl. The first step involves hydrothermal preparation of BiOCl nanosheets, while the second step involves hydrothermal loading of amorphous BiO onto the BiOCl surface, converting BiO into Bi-BiO during the hydrothermal reaction. The proportion of Bi-BiO introduced onto the BiOCl nanosheets is controlled by adjusting the amount of Bi(NO3)3·5H2O added during the second hydrothermal reaction. The ratio of Bi to BiO is adjusted by controlling the duration of the second hydrothermal reaction. The Z-shaped heterostructure formed by Bi-BiO / BiOCl enhances the photogenerated electron-hole separation capability and light absorption range. The in-situ formed Bi-BiO structure increases the oxygen vacancy concentration of the heterojunction, thereby giving the heterojunction excellent photocatalytic efficiency.

[0022] The experimental conditions of this invention are controllable and reproducible. The prepared Bi-BiO / BiOCl composite nanosheets, as catalysts, exhibit high catalytic activity, good stability, and ease of separation and recovery, and are expected to be applied in fields such as the degradation of organic pollutants, water decomposition, and wastewater treatment. The preparation method of this invention is easy to implement and universal, and is expected to achieve industrial application. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 These are scanning electron microscope images of BiOCl(a) and Bi-BiO / BiOCl(b) obtained in Example 1;

[0025] Figure 2 The XRD patterns of the Bi-BiO / BiOCl ternary Z-type heterojunctions obtained in Examples 1 and 5-7 and the BiOCl in Comparative Example 1 are shown.

[0026] Figure 3 The graphs show the photocatalytic degradation performance of methyl orange by the Bi-BiO / BiOCl ternary Z-type heterojunctions obtained in Examples 1-7 and BiOCl in Comparative Example 1.

[0027] Figure 4 The graphs show the photocatalytic degradation performance of methyl orange by the Bi-BiO / BiOCl ternary Z-type heterojunctions obtained in Examples 1 and 8-11, BiOCl in Comparative Example 1, and 0% Bi-BiO / BiOCl in Comparative Example 2.

[0028] Figure 5 XPS spectra of O1s for BiOCl and Bi-BiO / BiOCl obtained in Example 9. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0030] Example 1

[0031] 1.455 g Bi(NO3)3·5H2O was dissolved in 30 mL of water and stirred for 20 min. Then, 0.2235 g KCl was added, and the mixture was stirred for another 20 min. The solution was then transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and reacted at 160 °C for 12 h to obtain BiOCl. At room temperature, 0.25 mL of 10 M HNO3 solution, 2.25 mL of distilled water, and 12.5 mL of ethylene glycol were mixed thoroughly with a magnetic stirrer. Next, while stirring, 0.150 g Bi(NO3)3·5H2O and 0.8215 g BiOCl were added to the above solution, and the mixture was stirred for 30 min. The mixture was transferred to a 50 mL stainless steel autoclave lined with PTFE and heated at 160 °C for 1 h. After natural cooling, the precipitate was collected by centrifugation and washed several times with deionized water and ethanol. The precipitate was then vacuum dried at 60 °C to obtain a Bi-BiO / BiOCl ternary Z-type heterojunction.

[0032] like Figure 1 As shown, the Bi-BiO / BiOCl obtained by the hydrothermal method exhibits thin and uniform nanosheets, indicating that the introduction of Bi-BiO onto the BiOCl nanosheets did not alter the morphological structure, and the nanosheet structure exists in both the pre- and post-composite samples. In the loaded sample, spherical particles were observed uniformly loaded onto the nanosheet surface.

[0033] Example 2

[0034] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 10 min.

[0035] Example 3

[0036] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 30 min.

[0037] Example 4

[0038] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 3 h.

[0039] Example 5

[0040] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 6 h.

[0041] Example 6

[0042] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 12 h.

[0043] Example 7

[0044] Unlike Example 1, the mixture was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 160 °C for 24 h.

[0045] Comparative Example 1

[0046] Dissolve 1.455g Bi(NO3)3·5H2O in 30mL of water and stir for 20min. Then add 0.2235g KCl and stir for 20min. Transfer the mixture to a 50mL stainless steel autoclave lined with polytetrafluoroethylene and react at 160℃ for 12h to obtain BiOCl.

[0047] like Figure 2As shown, most diffraction peaks can be indexed as characteristic diffraction peaks of BiOCl (JCPDS No. 06-0249), and the diffraction peak at 27.2° can be indexed as a characteristic diffraction peak of Bi (JCPDS No. 51-1161). Furthermore, the intensity of this diffraction peak increases with increasing reaction time, indicating that the Bi content increases with reaction time. No BiO diffraction peaks were observed in Bi-BiO / BiOCl, indicating its amorphous structure. Amorphous BiO provides a higher specific surface area, a wider light absorption range, and higher conductivity, and has more defect states and oxygen vacancies, which are beneficial for photocatalytic reactions.

[0048] The photocatalytic degradation performance of methyl orange by the Bi-BiO / BiOCl ternary Z-type heterojunctions obtained in Examples 1-7 and BiOCl in Comparative Example 1 was tested. Specifically, 20 mg of Bi-BiO / BiOCl composite material and 100 mL of 10% BiOCl were added to a 100 mL reactor. -5 mol·L -1 The methyl orange dye was tested using a 300W xenon lamp to simulate sunlight. Figure 3 As shown, the Bi-BiO / BiOCl composite materials exhibit higher photocatalytic activity than BiOCl. The degradation efficiency of methyl orange gradually increases when the reaction time is shortened from 24 h to 1 h, but decreases sharply when the reaction time is shortened from 1 h to 10 min. In the second hydrothermal step, amorphous BiO is first loaded onto the surface of the BiOCl nanosheets. The metastability of BiO causes it to decompose and generate crystalline Bi during the hydrothermal process, thus creating oxygen vacancies. The presence of Bi also facilitates electron transport and inhibits charge recombination. However, with further extension of the hydrothermal time, BiO is excessively reduced to Bi, and the low BiO ratio leads to a significant decrease in oxygen vacancy concentration, resulting in a decline in photocatalytic performance.

[0049] Example 8

[0050] Unlike Example 1, 0.045g Bi(NO3)3·5H2O and 0.8215g BiOCl were added.

[0051] Example 9

[0052] Unlike Example 1, 0.075g Bi(NO3)3·5H2O and 0.8215g BiOCl were added.

[0053] Example 10

[0054] Unlike Example 1, 0.105g Bi(NO3)3·5H2O and 0.8215g BiOCl were added.

[0055] Example 11

[0056] Unlike Example 1, 0.225g Bi(NO3)3·5H2O and 0.8215g BiOCl were added.

[0057] Comparative Example 2

[0058] Unlike Example 2, 0g Bi(NO3)3·5H2O and 0.8215g BiOCl were added to obtain 0% Bi-BiO / BiOCl.

[0059] The photocatalytic degradation performance of Bi-BiO / BiOCl ternary Z-type heterojunctions obtained in Examples 1 and 8-11 and BiOCl in Comparative Example 2 was tested, such as... Figure 4 As shown, in the absence of a catalyst, only a small amount of MO was degraded. Bi-BiO / BiOCl composites with different loadings all exhibited higher photocatalytic efficiency than BiOCl, with the composite material with a loading of 5% in Example 9 showing the highest degradation efficiency. Figure 5 As shown, in Example 9, the oxygen vacancy (OV) content in the 5% Bi-BiO / BiOCl composite material reached as high as 57.22%, providing it with excellent photocatalytic performance. If the Bi-BiO loading is further increased, the performance of the Bi-BiO / BiOCl composite material begins to decline, mainly because excessive loading affects the light absorption efficiency and photogenerated charge separation efficiency of the catalyst.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a Bi-BiO / BiOCl ternary Z-type heterojunction in the photocatalytic degradation of methyl orange, characterized in that, Its preparation method includes the following steps: S1. Bi(NO3)3·5H2O and KCl were added to an appropriate amount of water and stirred evenly. Then, a hydrothermal reaction was carried out. After the hydrothermal reaction, the product was cooled, centrifuged, and washed to obtain BiOCl nanosheets. S2. Mix HNO3 solution, ethylene glycol and water to form a mixture. Add Bi(NO3)3·5H2O to the mixture and stir until a transparent solution is formed. Then add BiOCl nanosheets to the transparent solution to form a suspension. S3. The suspension obtained in step S2 is subjected to a hydrothermal reaction. After the hydrothermal reaction, the product is cooled, centrifuged, washed, and dried to obtain a Bi-BiO / BiOCl ternary Z-type heterojunction. The BiO is in an amorphous state.

2. The application as described in claim 1, characterized in that, In step S1, the ratio of Bi(NO3)3·5H2O, KCl and water is 1 mmol: 224-1491 mg: 10-40 mL.

3. The application as described in claim 1, characterized in that, In step S1, the hydrothermal reaction is carried out at a temperature of 150-170°C for 1-24 hours.

4. The application as described in claim 1, characterized in that, In step S2, the concentration of the HNO3 solution is 9.9-10.1 mol / L, and the volume ratio of HNO3 solution, ethylene glycol and water is 1:45-55:8-10.

5. The application as described in claim 1, characterized in that, In step S2, the proportion of Bi(NO3)3·5H2O added to the mixture is 1-20 mg / mL.

6. The application as described in claim 1, characterized in that, In step S2, the proportion of BiOCl nanosheets added to the transparent solution is 54-55 mg / mL.

7. The application as described in claim 1, characterized in that, In step S3, the hydrothermal reaction temperature is 150-170 ℃ and the time is 10 min-24 h.

8. The application as described in claim 1, characterized in that, In step S3, the centrifugation speed is 12500-13500 rpm; the washing method is to wash with deionized water 2-3 times first, and then wash with ethanol 2-3 times; the drying is vacuum drying at a temperature of 55-65 ℃ for 10-12 h.

Images