Method for improving oxygen production performance of bismuth oxyhalide photocatalyst

Abstract

The application belongs to the field of semiconductor photocatalytic materials, and relates to a cerium oxide / bismuth oxyhalide composite material synthesized by loading cerium oxide on bismuth oxyhalide through in-situ photodeposition. The photocatalytic oxygen production performance of bismuth oxyhalide is effectively improved by loading a cocatalyst on bismuth oxyhalide, shortening the migration distance of photo-generated carriers, promoting the separation of electron-hole pairs of bismuth oxyhalide, improving the photocurrent performance, reducing the impedance, greatly reducing the occurrence of photodecomposition of bismuth oxyhalide, and improving the light corrosion resistance of bismuth oxyhalide.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials, and more specifically to a method for improving the photocatalytic oxygen production performance of bismuth oxyhalide. Background Technology

[0002] Photocatalysis, as a novel and effective green technology, can effectively remove toxic and harmful organic pollutants from the environment using sunlight (Colloids Surf., A, 2019, 573, 137-45). Furthermore, photocatalysis is also frequently used for hydrogen production and the reduction of carbon dioxide into fuels (J. Photochem. Photobiol., C, 2019, 38, 1-26). Therefore, semiconductor photocatalysis technology is considered an effective way to solve energy and environmental problems.

[0003] Bismuth oxide (BiOX) is an indirect bandgap semiconductor with a moderate bandgap and good visible light absorption (Water Resour. Ind., 2023, 29, 100211). BiOX's open layered structure, high oxidation capacity, and high visible light response have also attracted widespread attention from researchers (Appl. Surf. Sci., 2019, 487, 743-54).

[0004] However, the low visible light utilization rate and high photogenerated carrier recombination rate of bismuth oxyhalide (BiOX), coupled with its susceptibility to decomposition under light irradiation, result in poor photocatalytic performance, limiting its further applications. Improving the photocatalytic performance and photocorrosion resistance of bismuth oxyhalide through ion doping, metal loading, and heterojunction construction (Korean J. Chem. Eng., 2018, 35, 1955-68) is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the photocatalytic oxygen production performance of bismuth halides.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for improving the photocatalytic oxygen production performance of bismuth oxyhalide involves loading a co-catalyst, cerium oxide (CeO2), onto the surface of bismuth oxyhalide (BiOX) to enhance its photocatalytic oxygen production performance; wherein the bismuth oxyhalide is bismuth oxychloride (BiOCl), bismuth oxybromine (BiOBr), or bismuth oxyiodide (BiOI).

[0008] Specifically, bismuth halide is dispersed in an aqueous solution of cerium nitrate hexahydrate, and cerium oxide (CeO2) is loaded onto the surface of bismuth halide by in-situ photodeposition.

[0009] Furthermore, the light source for the in-situ photodeposition method is a 300 W xenon lamp, and the illumination time is 5~10 min.

[0010] Furthermore, the loading of cerium oxide (CeO2) is 1~5 wt%.

[0011] A cerium oxide (CeO2) / bismuth halide (BiOX) composite material, wherein the CeO2 is loaded onto the BiOX surface by in-situ photodeposition.

[0012] Furthermore, the bismuth halide described herein has a nanosheet structure.

[0013] Furthermore, the bismuth halide is prepared by dissolving bismuth nitrate pentahydrate in ethylene glycol and transferring it to a syringe, then slowly injecting sodium halide dispersed in an aqueous solution. The resulting product is then washed with water by centrifugation and transferred to a deionized aqueous solution with a pH of 1 for hydrothermal synthesis. The hydrothermal synthesis takes 12 to 24 hours and is carried out at a temperature of 120 to 140 °C.

[0014] The above-mentioned cerium oxide (CeO2) / bismuth halide (BiOX) composite material is used in photocatalytic oxygen production systems.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) BiOX semiconductor materials have the advantages of being inexpensive and readily available as photocatalysts. The metal co-catalyst CeO2 is loaded onto the BiOX photocatalyst using an in-situ photodeposition method. By loading CeO2, the migration distance of photogenerated carriers is shortened, the carrier separation efficiency is improved, and the photocatalytic oxygen production performance is improved.

[0017] (2) By loading CeO2, the purpose of improving the effective separation of electron-hole pairs in BiOX material is achieved. By improving photocurrent performance, reducing impedance, and enhancing the transport and migration ability of photogenerated electron-hole pairs, the resistance to photocorrosion and the photocatalytic oxygen production performance can be improved. Attached Figure Description

[0018] Figure 1 The images show the X-ray powder diffraction patterns of (a) bismuth oxybromine and cerium oxide / bismuth oxybromine composite materials obtained in Example 2, (b) scanning electron microscope (SEM) image of bismuth oxybromine, (c) SEM image of bismuth oxybromine after 1 h of irradiation with a 300 W xenon lamp, (d) transmission electron microscope (TEM) image of the cerium oxide / bismuth oxybromine composite material, and (e) and (f) energy dispersive spectroscopy (EDS) images of the cerium oxide / bismuth oxybromine composite material.

[0019] Figure 2 The images show (a) photocurrent response diagram and (b) impedance diagram of the bismuth oxybromine and cerium oxide / bismuth oxybromine composite materials obtained in Example 2.

[0020] Figure 3 (a) Photocatalytic oxygen production performance of cerium oxide / bismuth oxybromine composites with different cerium oxide loadings, and (b) Long-term photocatalytic oxygen production performance of bismuth oxybromine and cerium oxide / bismuth oxybromine composites obtained in Example 2. Detailed Implementation

[0021] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0022] Example 1

[0023] (1) Preparation of bismuth oxybromine nanosheets: Weigh 0.001 mol of bismuth nitrate pentahydrate and add it to 30 mL of ethylene glycol solvent. Stir until completely dissolved (referred to as solution A). Dissolve 0.003 mol of sodium bromide (NaBr) in 30 mL of deionized water using ultrasonication (referred to as solution B). Transfer solution A to a 50 mL syringe and inject it into solution B at a rate of 2 mL / min under magnetic stirring at 300 rpm to form a white suspension. Centrifuge the suspension and wash it three times with deionized water. Filter the solution and redisperse the precipitate in 30 mL of deionized water with a pH of 1 (approximately 1 mL of 65% dilute nitric acid was added to 149 mL of deionized water). Transfer the precipitate to a PTFE autoclave (50 mL). Set the hydrothermal temperature to 140 °C and react for 12 hours. After the autoclave cools naturally to room temperature, centrifuge to collect the precipitate and wash it three times each with deionized water and ethanol. Finally, dry the precipitate in a 60 °C oven overnight to obtain bismuth oxybromine (BiOBr) nanosheets.

[0024] (2) Preparation of cerium nitrate hexahydrate aqueous solution: Dissolve 1 g of cerium nitrate hexahydrate solid in 1 mL of deionized water to obtain cerium nitrate hexahydrate Ce(NO3)3·6H2O aqueous solution.

[0025] (3) Preparation of cerium oxide / bismuth oxybromide composite material: 0.05 g of the above BiOBr nanosheets were weighed and dispersed in 100 mL of deionized water. 2.52 mL of Ce(NO3)3·6H2O solution (1 wt%) with a density of 1 g / mL was added dropwise and dispersed evenly to obtain a suspension. The suspension was then irradiated with a 300 W xenon lamp for 5 min. After the reaction was completed, the reaction solution was centrifuged and washed three times with deionized water and ethanol, respectively. Then, it was placed in an oven and dried at 60 °C overnight.

[0026] Example 2

[0027] (1) Preparation of bismuth oxybromide nanosheets: Weigh 0.001 mol of bismuth nitrate pentahydrate and add it to 30 mL of ethylene glycol solvent. Stir until completely dissolved (referred to as solution A). Dissolve 0.003 mol of sodium bromide (NaBr) in 30 mL of deionized water using ultrasonication (referred to as solution B). Transfer solution A to a 50 mL syringe and inject solution B at a rate of 2 mL / min under magnetic stirring at 300 rpm to form a white suspension. Centrifuge the suspension and wash it three times with deionized water. Filter the solution and redisperse the precipitate in 30 mL of deionized water with a pH of 1 (approximately 1 mL of 65% dilute nitric acid was added to 149 mL of deionized water). Transfer the precipitate to a 50 mL high-pressure autoclave and set the hydrothermal temperature to 140 °C. React for 12 hours. After the autoclave cools naturally to room temperature, centrifuge to collect the precipitate and wash it three times each with deionized water and ethanol. Finally, dry the precipitate in an oven at 60 °C overnight to obtain bismuth oxybromide nanosheets.

[0028] (2) Preparation of cerium nitrate hexahydrate aqueous solution: Dissolve 1 g of cerium nitrate hexahydrate solid in 1 mL of deionized water to obtain cerium nitrate hexahydrate aqueous solution.

[0029] (3) Preparation of cerium oxide / bismuth oxybromide composite material: 0.05 g of the above BiOBr nanosheets were weighed and dispersed in 100 mL of deionized water. 7.57 mL of 1 g / mL Ce(NO3)3·6H2O solution (3 wt.%) was added dropwise and dispersed evenly to obtain a suspension. The suspension was then irradiated with a 300 W xenon lamp for 5 min. After the reaction was completed, the reaction solution was centrifuged and washed three times with deionized water and ethanol, respectively. Then, it was placed in an oven and dried at 60 °C overnight.

[0030] Example 3

[0031] (1) Preparation of bismuth oxybromide nanosheets: Weigh 0.001 mol of bismuth nitrate pentahydrate and add it to 30 mL of ethylene glycol solvent, stirring until completely dissolved (denoted as solution A). Dissolve 0.003 mol of sodium bromide (NaBr) in 30 mL of deionized water using ultrasonication (denoted as solution B). Transfer solution A to a 50 mL syringe and inject it into solution B at a rate of 2 mL / min under magnetic stirring at 300 rpm to form a white suspension. Centrifuge the suspension and wash it three times with deionized water. Filter the solution and redisperse the precipitate in 30 mL of deionized water with a pH of 1 (approximately 1 mL of 65% dilute nitric acid was added to 149 mL of deionized water). Transfer the precipitate to a 50 mL high-pressure autoclave and set the hydrothermal temperature to 140 °C. React for 12 hours. After the autoclave cools naturally to room temperature, centrifuge to collect the precipitate. Wash it three times each with deionized water and ethanol, and finally dry it overnight in an oven at 60 °C to obtain bismuth oxybromide nanosheets.

[0032] (2) Preparation of cerium nitrate hexahydrate aqueous solution: Dissolve 1 g of cerium nitrate hexahydrate solid in 1 mL of deionized water to obtain cerium nitrate hexahydrate aqueous solution.

[0033] (3) Preparation of cerium oxide / bismuth oxybromide composite material: 0.05 g of the above BiOBr nanosheets were weighed and dispersed in 100 mL of deionized water. 12.61 mL of 1 g / mL Ce(NO3)3·6H2O solution (5 wt.%) was added dropwise, and the mixture was stirred and dispersed evenly to obtain a suspension. The suspension was then irradiated with a 300 W xenon lamp for 5 min. After the reaction was completed, the reaction solution was centrifuged and washed three times with deionized water and ethanol, respectively. Then, it was placed in an oven and dried overnight at 60 °C.

[0034] Example 4

[0035] (1) Preparation of bismuth oxybromide nanosheets: 0.003 mol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was weighed and added to 30 mL of ethylene glycol solvent and stirred until completely dissolved (denoted as solution A). 0.001 mol of sodium bromide (NaBr) was ultrasonically dissolved in 30 mL of deionized water (denoted as solution B). Solution A was transferred to a 50 mL syringe and injected into solution B at a rate of 2 mL / min under magnetic stirring at 300 rpm to form a white suspension. The suspension was centrifuged and washed three times with deionized water, filtered, and the resulting precipitate was redispersed in 30 mL of deionized water with a pH of 1 (approximately 1 mL of 65% dilute nitric acid was added to 149 mL of deionized water). The precipitate was transferred to a polytetrafluoroethylene autoclave (50 mL), and the hydrothermal temperature was set to 140℃ for 12 hours. After the autoclave has cooled to room temperature, the precipitate is collected by centrifugation, washed three times each with deionized water and ethanol, and finally dried overnight in an oven at 60°C to obtain bismuth oxybromide nanosheets.

[0036] (2) Preparation of cerium nitrate hexahydrate aqueous solution: Dissolve 1 g of cerium nitrate hexahydrate solid in 1 mL of deionized water to obtain cerium nitrate hexahydrate aqueous solution.

[0037] (3) Preparation of cerium oxide / bismuth oxybromide composite material: Weigh 0.05 g of the synthesized BiOBr nanosheets and disperse them in 100 mL of deionized water. Add 2.52 mL of 1 g / mL Ce(NO3)3·6H2O solution (1 wt.%) and stir to disperse evenly to obtain a suspension. Then irradiate the suspension with a 300 W xenon lamp for 10 min. After the reaction is complete, centrifuge the reaction solution, wash it three times with deionized water and ethanol respectively, and then dry it overnight in an oven at 60 °C.

[0038] Example 5

[0039] (1) Preparation of bismuth oxybromide nanosheets: Weigh 0.001 mol of bismuth nitrate pentahydrate and add it to 30 mL of ethylene glycol solvent. Stir until completely dissolved (referred to as solution A). Dissolve 0.001 mol of sodium bromide (NaBr) in 30 mL of deionized water using ultrasonication (referred to as solution B). Transfer solution A to a 50 mL syringe and inject it into solution B at a rate of 2 mL / min under magnetic stirring at 300 rpm to form a white suspension. Centrifuge the suspension and wash it three times with deionized water. Filter the solution and redisperse the precipitate in 30 mL of deionized water with a pH of 1 (approximately 1 mL of 65% dilute nitric acid was added to 149 mL of deionized water). Transfer the precipitate to a 50 mL high-pressure autoclave and set the hydrothermal temperature to 120 °C. React for 24 hours. After the autoclave cools naturally to room temperature, centrifuge to collect the precipitate. Wash it three times each with deionized water and ethanol. Finally, dry it overnight in an oven at 60 °C to obtain bismuth oxybromide nanosheets.

[0040] (2) Preparation of cerium nitrate hexahydrate aqueous solution: Dissolve 1 g of cerium nitrate hexahydrate solid in 1 mL of deionized water to obtain cerium nitrate hexahydrate aqueous solution.

[0041] (3) Preparation of cerium oxide / bismuth oxybromide composite material: 0.05 g of the above BiOBr nanosheets were weighed and dispersed in 100 mL of deionized water. 12.61 mL of 1 g / mL Ce(NO3)3·6H2O solution (5 wt.%) was added dropwise, and the mixture was stirred and dispersed evenly to obtain a suspension. The suspension was then irradiated with a 300 W xenon lamp for 5 min. After the reaction was completed, the reaction solution was centrifuged, washed three times with deionized water and ethanol, and then dried overnight in an oven at 60 °C.

[0042] Figure 1(a) shows the X-ray powder diffraction (XRD) patterns of bismuth oxybromine (BiOBr) and cerium oxide / bismuth oxybromine (CeO2 / BiOBr) composite materials obtained in Example 2. The experimental results show that the diffraction peaks of the BiOBr crystal plane correspond to the standard diffraction peaks of the tetragonal crystal form PDF#09-0393, indicating the successful synthesis of BiOBr. For the CeO2 / BiOBr composite material, no characteristic peaks of CeO2 were detected in its XRD diffraction pattern, which may be due to the small size of the CeO2 particles it supports. Figure (b) is a scanning electron microscope image of BiOBr, which shows that BiOBr mainly consists of square nanosheets. Figure (c) is an electron microscope image of BiOBr after being irradiated with a 300W xenon lamp for 1 h. It can be seen that after irradiation, the originally smooth edges of the bismuth oxybromine are covered with a thick serrated oxide film, reducing its photocatalytic reaction sites. Figures (d) and (e) show that after photodeposition, the loaded CeO2 particles encapsulate the edges of bismuth oxybromide, protecting BiOBr and effectively inhibiting the growth of the Bi2O3 oxide film, thereby improving the photocorrosion resistance of bismuth oxybromide. Energy dispersive spectroscopy (EDS) spectrum (f) shows that Bi, O, and Br are uniformly distributed throughout the nanosheet, while Ce is distributed at the edges, further demonstrating the successful synthesis of the cerium oxide / bismuth oxybromide (CeO2 / BiOBr) composite material.

[0043] Figure 2 Figure (a) shows the photocurrent response and (b) impedance diagram of the bismuth oxybromine (BiOBr) and cerium oxide / bismuth oxybromine (CeO2 / BiOBr) composite materials obtained in Example 2. Figure (a) clearly shows that both the photocatalyst before and after loading exhibit photosensitivity. However, during the on / off cycle of the light source, the photocurrent density of the CeO2 / BiOBr composite material is consistently superior to that of the pure BiOBr sample. This indicates that the loading of CeO2 effectively promotes the separation and migration of photogenerated electron-hole pairs. Effective separation of photogenerated electron-hole pairs ensures that electrons or holes participate more effectively in photocatalytic reduction or oxidation reactions, thereby improving photocatalytic performance. Electrochemical impedance spectroscopy (EIS) was used to detect the interfacial migration dynamics of charge carriers. Figure (b) shows the impedance diagrams of the bismuth oxybromine (BiOBr) and cerium oxide / bismuth oxybromine (CeO2 / BiOBr) composite materials. Compared to bismuth oxybromine (BiOBr), the cerium oxide / bismuth oxybromine (CeO2 / BiOBr) composite material has a smaller (impedance) radius of curvature, revealing that the loading of CeO2 can promote charge transfer at the BiOBr interface. This indicates that the charge transfer capability and conductivity of the composite material are superior to those of the pure BiOBr sample, which is beneficial to improving the photocatalytic oxygen production performance of bismuth oxybromine (BiOBr).

[0044] The photocatalytic oxygen production performance was tested using a CEL-HXE300 xenon lamp (300 W). 0.05 g of catalyst and 0.4 g of ferrous nitrate nonahydrate were added to 100 mL of deionized water and ultrasonically dispersed. The suspension was placed in a water splitting reactor and reacted for 1 hour in a closed-loop system with stirring at 600 rpm. The types and yields of produced gases were then analyzed using a gas chromatograph (GC-2014C, Shimadzu, Japan). Figure 3 The figures show the photocatalytic oxygen production performance of the BiOBr and CeO2 / BiOBr composite materials obtained in Examples 1-3. As shown in Figure (a), the photocatalytic performance is optimal at a cerium oxide loading content of 3 wt.%, approximately 86.1 μmol / h. When the cerium oxide loading content is 1 wt.%, the photocatalytic activity of the composite material is relatively low. This is because the amount of CeO2 in the CeO2 / BiOBr composite is small, resulting in a lower electron-hole pair separation efficiency. The photocatalytic oxygen production is relatively low when the cerium oxide loading content in the composite material is 5 wt.%, because the excessive CeO2 content causes the BiOBr edge to be over-coated by CeO2, covering the reactive sites on its surface and reducing the photocatalytic activity of CeO2 / BiOBr. Figure (b) shows the 10-hour photocatalytic oxygen production performance of CeO2, BiOBr obtained in Example 2, and the CeO2 / BiOBr composite material. The photocatalytic oxygen production amount and rate within 10 hours were used to evaluate the photocatalytic performance and photocorrosion resistance of BiOBr and the CeO2 / BiOBr composite material. As shown in the figure, the photocatalytic oxygen production of BiOBr after CeO2 loading increased to 2.8 times that of pure BiOBr. The photocatalytic oxygen production of pure CeO2 was much lower than that of BiOBr and the CeO2 / BiOBr composite material, and did not increase significantly after prolonged illumination. In the 10-hour continuous oxygen production test, it was found that the photocatalytic oxygen production rate of pure BiOBr gradually approached a plateau after 5 hours of photocatalysis, while the reaction rate of the CeO2 / BiOBr composite photocatalyst remained essentially unchanged after a long period of photocatalytic reaction. This long-term photocatalytic oxygen production performance test demonstrates that the photocatalytic oxygen production performance of BiOBr is enhanced after CeO2 loading.

[0045] In summary, this invention utilizes a supported CeO2 catalyst to form a BiOX-CeO2 heterojunction structure with halogen atoms. This structure facilitates electron-hole transport, thereby improving the catalytic performance of the composite. By redirecting holes that cause photocorrosion, it prevents their accumulation on the BiOX surface. This heterojunction structure enhances resistance to photocorrosion, thus promoting photocatalytic oxygen production.

[0046] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for improving the photocatalytic oxygen production performance of bismuth halide, characterized in that: The photocatalytic oxygen production performance of bismuth oxyhalide (BiOX) is improved by loading cerium oxide (CeO2) as a co-catalyst on the surface of bismuth oxyhalide (BiOX); wherein the bismuth oxyhalide is bismuth oxychloride (BiOCl), bismuth oxybromine (BiOBr), or bismuth oxyiodide (BiOI).

2. The method for improving the photocatalytic oxygen production performance of bismuth halide according to claim 1, characterized in that: Specifically, bismuth halide is dispersed in an aqueous solution of cerium nitrate hexahydrate, and cerium oxide (CeO2) is loaded onto the surface of bismuth halide by in-situ photodeposition.

3. The method for improving the photocatalytic oxygen production performance of bismuth halide according to claim 2, characterized in that: The in-situ photodeposition method uses a 300 W xenon lamp as the light source and the illumination time is 5-10 min.

4. The method for improving the photocatalytic oxygen production performance of bismuth halide according to claim 2, characterized in that: The CeO2 loading is 1~5 wt%.

5. A cerium oxide (CeO2) / bismuth halide (BiOX) composite material, characterized in that: The CeO2 was loaded onto the BiOX surface by in-situ photodeposition. Specifically, bismuth halide is dispersed in an aqueous solution of cerium nitrate hexahydrate, and cerium oxide (CeO2) is loaded onto the surface of bismuth halide by in-situ photodeposition. The light source for the in-situ photodeposition is a 300 W xenon lamp, and the illumination time is 5-10 min. The bismuth halide has a nanosheet structure; The bismuth halide is prepared by dissolving bismuth nitrate pentahydrate in ethylene glycol and transferring it to a syringe, then slowly injecting sodium halide dispersed in an aqueous solution. The resulting product is then washed with water by centrifugation and transferred to a deionized aqueous solution with a pH of 1 for hydrothermal synthesis. The hydrothermal synthesis takes 12 to 24 hours and is carried out at a temperature of 120 to 140 °C.

6. The application of the cerium oxide CeO2 / bismuth halide BiOX composite material as described in claim 5 in a photocatalytic oxygen production system.

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