Preparation method of biocl / bioi composite catalyst for visible light degradation of rhodamine b

Abstract

This invention belongs to the field of photocatalytic materials technology and discloses a method for preparing a BiOCl / BiOI composite photocatalyst for the visible light degradation of Rhodamine B. By synergistically regulating the band structure of BiOCl with BiOI, a highly efficient photocatalytic decolorization of Rhodamine B with a broad-spectrum response is achieved through S-type interfacial charge transfer. The method involves a petal-shaped R=8:1 BiOCl / BiOI heterojunction and BiOCl... 0.88 I 0.12 and BiOCl 0.8 I 0.2 The solid solution exhibits excellent visible light photocatalytic activity, degrading approximately 92.52%, 99.7%, and 99.7% of Rhodamine B molecules after 10 minutes of visible light irradiation, respectively. The catalytic reaction follows a two-stage first-order kinetic model, and high photocatalytic efficiency is maintained even after 5 cycles. The degradation of approximately 64.3% and 10.02% of Rhodamine B molecules by BiOCl and BiOI alone under the same photoreaction conditions follows a first-order kinetic model. This invention has advantages such as low preparation temperature, simple process, and stable chemical properties. Large-scale two-dimensional micro / nanosheets and their three-dimensional self-assembled structures can be obtained through hydrothermal and water bath synthesis processes, making it highly valuable for the visible light degradation of organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, and relates to a method for preparing a BiOCl / BiOI composite catalyst for visible light degradation of Rhodamine B. Background Technology

[0002] Semiconductor photocatalysis technology can directly absorb solar energy and convert it into high-value-added chemical energy, showing significant advantages in environmental remediation, water splitting, and CO2 reduction. In recent years, bismuth oxyhalides (BiOX, X = F, Cl, Br, and I) have become one of the most promising semiconductor photocatalysts after TiO2 (P25) due to their stable physicochemical properties and unique electronic structure. Its highly anisotropic layered structure consists of a double halide ion layer and [Bi2O2]. 2+ The layers are arranged in an alternating pattern, providing sufficient space for the polarization of atoms and orbitals. The built-in electric field formed along the

[001] direction promotes the separation of photogenerated electrons and holes, thereby improving the photocatalytic activity. Compared with other layered catalysts, BiOX has better photocatalytic stability due to the intralayer covalent bonds and interlayer van der Waals forces. However, problems such as low photon absorption efficiency, easy recombination of photogenerated carriers, and relatively positive conduction band edge potential still become bottlenecks restricting the practical application of single BiOX photocatalysis technology. Reasonable band structure regulation and surface and interface microstructure design are the key to improving the photocatalytic noble metal enrichment performance of BiOX-based semiconductors. Band structure trimming can precisely adjust the quasi-Fermi level and redox potential of the catalyst, thereby broadening the photoresponse range and enhancing the driving force of the catalytic reaction; at the same time, it can extend the lifetime of photogenerated carriers and achieve efficient visible light photocatalysis. Although BiOI has a strong visible light absorption capacity, the rapid recombination of photogenerated electrons and holes seriously weakens its photocatalytic activity. Changing the halogen atom composition can achieve continuous tunability of the BiOX band gap energy.

[0003] The BiOCl / BiOI composite photocatalyst of the present invention has the advantages of low preparation temperature, simple process and stable chemical properties. The resulting large-scale two-dimensional micro / nanosheets and their three-dimensional self-assembled structures are more conducive to chemical modification and photogenerated carrier migration, and have great application value in the field of visible light degradation of organic pollutants. Summary of the Invention

[0004] This invention provides a method for preparing a BiOCl / BiOI composite catalyst for the visible light degradation of Rhodamine B, addressing the need for mineralization of organic pollutants. The method combines BiOI and BiOCl to promote phase separation of photogenerated charge carriers, achieving highly efficient visible light degradation of Rhodamine B with a broad spectral response. Morphology control is utilized to obtain a petal-like self-assembled structure of BiOCl / BiOI and BiO(Cl,I), which exhibits excellent visible light catalytic activity and cycling stability after only 10 minutes of visible light irradiation, making it a powerful tool for environmental purification and energy conversion.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a BiOCl / BiOI composite catalyst for visible light degradation of Rhodamine B, wherein the BiOCl / BiOI composite catalyst comprises a BiOCl / BiOI heterojunction and a BiO(Cl,I) solid solution.

[0007] The preparation method of the BiOCl / BiOI heterojunction comprises the following steps:

[0008] (1) Add bismuth nitrate solution and potassium chloride solution to deionized water in a molar ratio of 1:1 and stir continuously for 30 minutes. The volume ratio of bismuth nitrate, potassium chloride and deionized water is 2:1:30.

[0009] The bismuth nitrate (Bi(NO3)3·5H2O) solution contains Bi 3+ The concentration is 0.5 mol / L;

[0010] The potassium chloride (KCl) solution contains Cl - The concentration is 1 mol / L;

[0011] The potassium iodide (KI) solution contains I - The concentration is 1 mol / L;

[0012] (2) Add sodium hydroxide or nitric acid dropwise to the solution in step (1) to adjust the pH value to 10, stir thoroughly to obtain a uniform suspension; then transfer it to a hydrothermal reactor and react in an oven preheated to 180°C for 24 hours.

[0013] (3) The hydrothermal products were separated by centrifugation and dried to obtain the BiOCl precursor;

[0014] (4) The BiOCl precursor powder obtained in step (3) is ultrasonically dispersed in an aqueous solution containing ethylene glycol. The volume ratio of ethylene glycol to deionized water is 1:2, and the solution volume is the same as in step (1).

[0015] (5) Add bismuth nitrate solution and potassium iodide solution to step (4) and prepare the solution according to the molar ratio of BiOCl:BiOI R = 8:1;

[0016] (6) The mixed solution obtained in step (5) is reacted in a water bath at 60°C for 30 min;

[0017] (7) The water bath product was centrifuged and dried to obtain BiOCl / BiOI heterojunction;

[0018] The preparation method of the BiO(Cl,I) solid solution comprises the following steps:

[0019] A. Add potassium chloride and potassium iodide solutions to the deionized water solution and stir continuously for 30 minutes, using a molar ratio of Cl... - :I - The solutions were prepared in ratios of 8:1 and 4:1, and the total volume of potassium chloride and potassium iodide solutions was mixed with the volume of deionized water at a ratio of 1:30.

[0020] The potassium chloride (KCl) solution contains Cl - The concentration is 1 mol / L;

[0021] The potassium iodide (KI) solution contains I - The concentration is 1 mol / L;

[0022] B. Add bismuth nitrate solution to step (A), according to Bi 3+ :(Cl - +I - Prepare the mixture with a molar ratio of 1:1;

[0023] The bismuth nitrate (Bi(NO3)3·5H2O) solution contains Bi 3+ The concentration is 0.5 mol / L;

[0024] C. The mixed solution obtained in step (B) is reacted in a water bath at 60°C for 30 minutes;

[0025] D. The product obtained by water bath was centrifuged and dried to obtain BiO(Cl,I) solid solution.

[0026] A further feature is that in steps (3), (7) and (D), the centrifugal separation process is as follows: washing with deionized water three times and rinsing with alcohol once;

[0027] A further feature is that in steps (3), (7) and (D), the drying temperature is 70°C and the drying time is 24 hours.

[0028] This invention relates to a BiOCl / BiOI composite photocatalyst for the visible light degradation of Rhodamine B. By synergistically modulating the band structure of BiOCl with BiOI, it achieves highly efficient photocatalytic decolorization of Rhodamine B with a broad-spectrum response through S-type interfacial charge transfer. The catalyst comprises a petal-shaped R=8:1 BiOCl / BiOI heterojunction and a BiOCl... 0.88 I 0.12 and BiOCl 0.8 I 0.2The solid solution exhibits excellent visible light photocatalytic activity, degrading approximately 92.52%, 99.7%, and 99.7% of Rhodamine B molecules after 10 minutes of visible light irradiation, respectively. The catalytic reaction follows a two-stage first-order kinetic model, and high photocatalytic efficiency is maintained even after 5 cycles. Under the same photoreaction conditions, BiOCl and BiOI alone degrade approximately 64.3% and 10.02% of Rhodamine B molecules, respectively, and the catalytic reactions follow a first-order kinetic model.

[0029] The preparation method of this invention is characterized by low temperature, simple process, and stable chemical properties. Large-scale two-dimensional micro / nanosheets and their three-dimensional self-assembled structures can be obtained through hydrothermal and water bath synthesis processes, which has great application value in the field of visible light degradation of organic pollutants. Attached Figure Description

[0030] Figure 1 The XRD patterns of the BiOCl / BiOI composite photocatalysts prepared in Examples 1-5 are shown.

[0031] Figure 2 The R=8:1 BiOCl / BiOI heterojunction and BiOCl prepared in Examples 3 and 4 0.88 I 0.12 TEM morphology of solid solutions;

[0032] Figure 3 The absorption spectra of the BiOCl / BiOI composite photocatalysts prepared in Examples 1-5 under visible light irradiation to degrade Rhodamine B;

[0033] Figure 4 The BiOCl / BiOI composite photocatalysts prepared in Examples 1-5 demonstrate the photodegradation performance of Rhodamine B under visible light irradiation.

[0034] Figure 5 It is the BiOCl prepared in Example 4 0.88 I 0.12 Results of cyclic degradation of Rhodamine B by solid solution;

[0035] Figure 6 The images show the photocurrent response curves and electrochemical impedance spectra of the BiOCl / BiOI composite photocatalysts prepared in Examples 1-4. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments. All chemical formulas used in the examples are of analytical grade.

[0037] In this embodiment of the invention, a Rigaku D / max-2500PC X-ray diffractometer was used to analyze the phase composition; a JEOL JEM-2100F transmission electron microscope was used to analyze the morphology and microstructure of the product; a Shimadzu UV-3600Plus UV-Vis spectrophotometer was used to analyze the absorbance changes of Rhodamine B molecules in the spectral range of 400–700 nm at different photoreaction times; and an electrochemical workstation was used to test the photocurrent response curve and electrochemical impedance spectroscopy.

[0038] Example 1

[0039] (1) Preparation of solution

[0040] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in deionized water and mixed thoroughly to prepare a Bi 3+ A 0.5 mol / L bismuth nitrate (Bi(NO3)3·5H2O) solution;

[0041] Dissolve potassium chloride (KCl) in deionized water and mix thoroughly to prepare Cl... - A 1 mol / L potassium chloride (KCl) solution;

[0042] (2) Add the 2 mmol bismuth nitrate and 2 mmol potassium chloride solution prepared in step (1) to 60 mL of deionized water and stir continuously for 30 min.

[0043] (3) Add sodium hydroxide or nitric acid to the solution in step (2) to adjust the pH value to 10 and stir thoroughly for 30 min to obtain a uniform suspension; then transfer it to a 100 mL hydrothermal reactor and react in an oven preheated to 180 °C for 24 h.

[0044] (4) The hydrothermal products were centrifuged and dried to obtain BiOCl powder.

[0045] Example 2

[0046] (1) Preparation of solution

[0047] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in deionized water and mixed thoroughly to prepare a Bi 3+ A 0.5 mol / L bismuth nitrate (Bi(NO3)3·5H2O) solution;

[0048] Dissolve potassium iodide (KI) in deionized water and mix thoroughly to prepare I - A 1 mol / L potassium iodide (KI) solution;

[0049] (2) Add the 2 mmol bismuth nitrate and 2 mmol potassium iodide solution prepared in step (1) to a 60 mL aqueous solution containing 20 mL ethylene glycol;

[0050] (3) The mixed solution obtained in step (2) is reacted in a water bath at 60°C for 30 min;

[0051] (4) The hydrothermal products were centrifuged and dried to obtain BiOI powder.

[0052] Example 3

[0053] (1) Preparation of solution

[0054] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in deionized water and mixed thoroughly to prepare a Bi 3+ A 0.5 mol / L bismuth nitrate (Bi(NO3)3·5H2O) solution;

[0055] Dissolve potassium chloride (KCl) in deionized water and mix thoroughly to prepare Cl... - A 1 mol / L potassium chloride (KCl) solution;

[0056] Dissolve potassium iodide (KI) in deionized water and mix thoroughly to prepare I - A 1 mol / L potassium iodide (KI) solution;

[0057] (2) Add the 2 mmol bismuth nitrate and 2 mmol potassium iodide solution prepared in step (1) to 60 mL of deionized water and stir continuously for 30 min.

[0058] (3) Add sodium hydroxide or nitric acid to the solution in step (2) to adjust the pH value to 10 and stir thoroughly for 30 min to obtain a uniform suspension; then transfer it to a 100 mL hydrothermal reactor and react in an oven preheated to 180 °C for 24 h.

[0059] (4) The hydrothermal products were separated by centrifugation and dried to obtain the BiOCl precursor.

[0060] (5) The 2 mmol BiOCl precursor powder obtained in step (4) was ultrasonically dispersed in 60 mL of aqueous solution containing 20 mL of ethylene glycol.

[0061] (6) Add 2 mmol of bismuth nitrate and potassium iodide solution to step (5), and then add it according to Cl. - :I - Prepare the mixture with a molar ratio of R = 8:1;

[0062] (7) The mixed solution obtained in step (6) is reacted in a water bath at 60°C for 30 min;

[0063] (8) The water bath product was centrifuged and dried to obtain BiOCl / BiOI heterojunction.

[0064] Example 4

[0065] (1) Preparation of solution

[0066] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in deionized water and mixed thoroughly to prepare a Bi 3+ A 0.5 mol / L bismuth nitrate (Bi(NO3)3·5H2O) solution;

[0067] Dissolve potassium chloride (KCl) in deionized water and mix thoroughly to prepare Cl... - A 1 mol / L potassium chloride (KCl) solution;

[0068] Dissolve potassium iodide (KI) in deionized water and mix thoroughly to prepare I - A 1 mol / L potassium iodide (KI) solution;

[0069] (2) Add the 2 mmol potassium chloride and potassium iodide solution prepared in step (1) to 60 mL of deionized water and stir continuously for 30 min. Add the solution at a molar ratio of Cl... - :I - The ratio is 8:1.

[0070] (3) Add 2 mmol of bismuth nitrate to step (2);

[0071] (4) The mixed solution obtained in step (3) is reacted in a water bath at 60°C for 30 min;

[0072] (5) The water bath product was centrifuged and dried to obtain BiO(Cl,I) solid solution.

[0073] Example 5

[0074] (1) Preparation of solution

[0075] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in deionized water and mixed thoroughly to prepare a Bi 3+ A 0.5 mol / L bismuth nitrate (Bi(NO3)3·5H2O) solution;

[0076] Dissolve potassium chloride (KCl) in deionized water and mix thoroughly to prepare Cl... - A 1 mol / L potassium chloride (KCl) solution;

[0077] Dissolve potassium iodide (KI) in deionized water and mix thoroughly to prepare I - A 1 mol / L potassium iodide (KI) solution;

[0078] (2) Add the 2 mmol potassium chloride and potassium iodide solution prepared in step (1) to 60 mL of deionized water and stir continuously for 30 min. Add the solution at a molar ratio of Cl... - :I - The ratio is 4:1.

[0079] (3) Add 2 mmol of bismuth nitrate to step (2);

[0080] (4) The mixed solution obtained in step (3) is reacted in a water bath at 60°C for 30 min;

[0081] (5) The water bath product was centrifuged and dried to obtain BiO(Cl,I) solid solution.

Claims

1. A method for preparing a BiOCl / BiOI heterojunction for visible light degradation of Rhodamine B, characterized in that, The steps are as follows: (1) Add bismuth nitrate solution and potassium chloride solution to deionized water in a molar ratio of 1:1 and stir continuously for 30 min. The volume ratio of bismuth nitrate, potassium chloride and deionized water is 2:1:

30. The bismuth nitrate (Bi(NO3)3·5H2O) solution contains Bi 3+ The concentration is 0.5 mol / L; The potassium chloride (KCl) solution contains Cl - The concentration is 1 mol / L; Potassium iodide (KI) solution I - The concentration is 1 mol / L; (2) Add sodium hydroxide or nitric acid to the solution in step (1) to adjust the pH value to 10, stir thoroughly to obtain a uniform suspension; then transfer it to a hydrothermal reactor and react in an oven preheated to 180 °C for 24 h. (3) The hydrothermal products were centrifuged and dried to obtain the BiOCl precursor; (4) The BiOCl precursor powder obtained in step (3) is ultrasonically dispersed in an aqueous solution containing ethylene glycol. The volume ratio of ethylene glycol to deionized water is 1:2, and the solution volume is the same as in step (1). (5) Add bismuth nitrate solution and potassium iodide solution to step (4) and prepare the solution according to the molar ratio of BiOCl:BiOI R=8:1; (6) The mixed solution obtained in step (5) is reacted in a water bath at 60 °C for 30 min; (7) The water bath product was centrifuged and dried to obtain BiOCl / BiOI heterojunction.

2. The preparation method according to claim 1, characterized in that: In steps (3) and (7), the centrifugal separation process is as follows: three washes with deionized water and one rinse with alcohol.

3. The preparation method according to claim 1, characterized in that, In steps (3) and (7), the drying temperature is 70°C and the drying time is 24 h.

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