Preparation method of BiOCl / BiOI composite catalyst for visible light degradation of rhodamine B

Abstract

The invention belongs to the technical field of photocatalytic materials, and discloses a preparation method of a BiOCl / BiOI composite photocatalyst for visible light degradation of rhodamine B. The energy band structure of BiOCl is regulated and controlled in cooperation with BiOI, and efficient photocatalytic decoloration of rhodamine B with wide spectral response is achieved through S-type interface charge transfer. A petal-shaped BiOCl / BiOI heterojunction with R = 8: 1, a BiOCl0. 88I0. 12 solid solution and a BiOCl0. 8I0. 2 solid solution show excellent visible light catalytic activity, and about 92.52% of rhodamine B molecules, 99.7% of rhodamine B molecules and 99.7% of rhodamine B molecules are respectively degraded by the BiOCl / BiOI heterojunction and the BiOCl0. 88I0. 12 solid solution after being irradiated by visible light for 10 minutes. The catalytic reaction accords with the two-stage one-stage kinetic law, and high photocatalytic efficiency can still be maintained after five times of circulation. The single BiOCl and BiOI respectively degrade about 64.3% and 10.02% of rhodamine B molecules under the same light reaction condition, and the catalytic reaction follows a first-level kinetic model. The preparation method has the advantages of being low in preparation temperature, simple in technological process, stable in chemical property and the like, the large-scale two-dimensional micron / nanosheet and the three-dimensional self-assembly structure of the large-scale two-dimensional micron / nanosheet can be obtained only through a hydrothermal and water bath synthesis technology, and the preparation method has great application value in the field of visible light degradation of organic pollutants.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials and relates to a method for preparing a BiOCl / BiOI composite catalyst for degrading rhodamine B under visible light. Background Art

[0002] Semiconductor photocatalytic technology can directly absorb solar energy and convert it into high value-added chemical energy, which can be used in environmental remediation, water splitting, CO 2 In recent years, bismuth oxyhalides (BiOX, X = F, Cl, Br and I) have become TiO due to their stable physical and chemical properties and unique electronic structure. 2 (P25) is one of the most promising semiconductor photocatalysts. Its highly anisotropic layered structure is composed of a double halogen ion layer and [Bi 2 O 2 ] 2+ The layers are staggered and provide 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 photoreaction activity. Compared with other layered catalysts, BiOX has better photocatalytic stability due to the covalent bonds within the layers and the van der Waals forces between the layers. However, problems such as low photon absorption efficiency, easy recombination of photogenerated carriers, and relatively positive conduction band edge potential still become bottleneck problems restricting the practical application of single BiOX photocatalytic technology. Reasonable band structure regulation and surface interface microstructure design are the key to improving the precious metal enrichment performance of BiOX-based semiconductor photocatalysis. Band structure tailoring can accurately adjust the quasi-Fermi level and redox potential of the catalyst, thereby broadening the light response range and enhancing the driving force of the catalytic reaction; at the same time, it prolongs the lifetime of photogenerated carriers and realizes efficient visible light catalysis. Although BiOI has a strong visible light absorption ability, the rapid recombination of photogenerated electrons and holes seriously weakens its photoreaction activity. Changing the halogen atomic composition can achieve continuous adjustment 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, stable chemical properties, etc. The obtained large-scale two-dimensional micro / nano sheets 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] The present invention provides a preparation method of a BiOCl / BiOI composite catalyst for visible light degradation of rhodamine B in response to the demand for mineralization of organic pollutants. The composite of BiOI and BiOCl promotes phase separation of photogenerated carriers and realizes efficient visible light degradation of rhodamine B with a wide spectrum response. The petal-shaped self-assembly structure of BiOCl / BiOI and BiO(Cl,I) is obtained by morphology control, and can show excellent visible light catalytic activity and cycle stability after only 10 minutes of visible light irradiation, which is a powerful tool for environmental purification and energy conversion.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a BiOCl / BiOI composite catalyst for visible light degradation of rhodamine B. 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) adding bismuth nitrate solution and potassium chloride solution to deionized water solution in a molar ratio of 1:1 and stirring continuously for 30 minutes; the volume ratio of bismuth nitrate, potassium chloride and deionized water is 2:1:30;

[0009] The bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) Bi in solution 3+ The concentration is 0.5 mol / L;

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

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

[0012] (2) adding sodium hydroxide or nitric acid dropwise to the solution in step (1) to adjust the pH value of the solution to 10, stirring thoroughly to obtain a uniform suspension; then transferring the suspension to a hydrothermal reactor and reacting the mixture in an oven preheated to 180° C. for 24 h;

[0013] (3) The hydrothermal product is centrifuged and dried to obtain a BiOCl precursor;

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

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

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

[0017] (7) The water bath product is centrifuged and dried to obtain a 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 solution to deionized water solution and continue stirring for 30 minutes. - :I - =8:1 and 4:1, the total volume of potassium chloride and potassium iodide solution and the volume ratio of deionized water are 1:30;

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

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

[0022] B. Add bismuth nitrate solution to step (A) and 3+ :(Cl - +I - ) was prepared at a molar ratio of 1:1;

[0023] The bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) Bi in solution 3+ The concentration is 0.5 mol / L;

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

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

[0026] Further characterized, in steps (3), (7) and (D), the centrifugal separation process is: washing three times with deionized water and rinsing once with alcohol;

[0027] Further features, in steps (3), (7) and (D), the drying temperature is 70°C and the drying time is 24 hours.

[0028] The BiOCl / BiOI composite photocatalyst for visible light degradation of rhodamine B of the present invention cooperates with BiOI to regulate the energy band structure of BiOCl, and utilizes S-type interface charge transfer to achieve efficient photocatalytic decolorization of rhodamine B with a wide spectrum response. Petal-shaped R=8:1BiOCl / BiOI heterojunction, BiOCl 0.88 I 0.12 and BiOCl 0.8 I 0.2 The solid solution exhibited excellent visible light photocatalytic activity, and after 10 minutes of visible light irradiation, it degraded about 92.52%, 99.7%, and 99.7% of the rhodamine B molecules, respectively. The catalytic reaction conformed to the two-stage first-order kinetic law, and the high photocatalytic efficiency could be maintained after 5 cycles. Single BiOCl and BiOI degraded about 64.3% and 10.02% of the rhodamine B molecules, respectively, under the same photoreaction conditions, and the catalytic reaction followed the first-order kinetic model.

[0029] The preparation method of the present invention has low temperature, simple process and stable chemical properties. Large-scale two-dimensional micro / nano sheets and their three-dimensional self-assembled structures can be obtained only through hydrothermal and water bath synthesis processes, which has great application value in the field of visible light degradation of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the XRD spectrum of the BiOCl / BiOI composite photocatalyst prepared in Examples 1 to 5;

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

[0032] Figure 3 is the absorption spectrum of the BiOCl / BiOI composite photocatalyst prepared in Examples 1 to 5 for degradation of Rhodamine B under visible light irradiation;

[0033] Figure 4 The photodegradation performance of the BiOCl / BiOI composite photocatalyst prepared in Examples 1 to 5 for Rhodamine B under visible light irradiation;

[0034] Figure 5 The BiOCl prepared in Example 4 0.88 I 0.12 The results of cyclic degradation of Rhodamine B by solid solution;

[0035] Figure 6 The photocurrent response curves and electrochemical impedance spectra of the BiOCl / BiOI composite photocatalysts prepared in Examples 1 to 4 are shown. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the examples, and the chemical formulas used in the examples are all of analytically pure grade.

[0037] In the embodiment of the present invention, a D / max-2500PC X-ray diffractometer produced by Rigaku of Japan is used to analyze the physical phase; a JEM-2100F transmission electron microscope produced by JEOL of Japan is used to analyze the morphology and microstructure of the product; a UV-3600Plus ultraviolet-visible spectrophotometer produced by Shimadzu of Japan is used to analyze the absorbance change of the Rhodamine B molecule in the spectral range of 400 to 700 nm under different photoreaction times of the catalyst; and an electrochemical workstation is used to test the photocurrent response curve and the electrochemical impedance spectrum.

[0038] Example 1

[0039] (1) Preparation of solution

[0040] Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in deionized water and mixed evenly to prepare Bi 3+ Bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) solution;

[0041] Dissolve potassium chloride (KCl) in deionized water and mix well to prepare Cl - Potassium chloride (KCl) solution with a concentration of 1 mol / L;

[0042] (2) adding 2 mmol of bismuth nitrate and 2 mmol of potassium chloride solution prepared in step (1) to 60 mL of deionized water and stirring continuously for 30 min;

[0043] (3) adding sodium hydroxide or nitric acid dropwise to the solution in step (2) to adjust the pH value of the solution to 10 and stirring for 30 min to obtain a uniform suspension; then transferring the mixture to a 100 mL hydrothermal kettle and reacting it in an oven preheated to 180° C. for 24 h;

[0044] (4) The hydrothermal product is separated by centrifugation and dried to obtain BiOCl powder.

[0045] Example 2

[0046] (1) Preparation of solution

[0047] Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in deionized water and mixed evenly to prepare Bi3+ Bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) solution;

[0048] Dissolve potassium iodide (KI) in deionized water and mix well to prepare I - Potassium iodide (KI) solution with a concentration of 1 mol / L;

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

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

[0051] (4) The hydrothermal product is separated by centrifugation and dried to obtain BiOI powder.

[0052] Example 3

[0053] (1) Preparation of solution

[0054] Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in deionized water and mixed evenly to prepare Bi 3+ Bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) solution;

[0055] Dissolve potassium chloride (KCl) in deionized water and mix well to prepare Cl - Potassium chloride (KCl) solution with a concentration of 1 mol / L;

[0056] Dissolve potassium iodide (KI) in deionized water and mix well to prepare I - Potassium iodide (KI) solution with a concentration of 1 mol / L;

[0057] (2) adding 2 mmol of bismuth nitrate and 2 mmol of potassium iodide solution prepared in step (1) to 60 mL of deionized water and stirring continuously for 30 min;

[0058] (3) adding sodium hydroxide or nitric acid dropwise to the solution in step (2) to adjust the pH value of the solution to 10 and stirring for 30 min to obtain a uniform suspension; then transferring the mixture to a 100 mL hydrothermal kettle and reacting it in an oven preheated to 180° C. for 24 h;

[0059] (4) The hydrothermal product is separated by centrifugation and dried to obtain BiOCl precursor.

[0060] (5) ultrasonically dispersing the 2 mmol BiOCl precursor powder obtained in step (4) in 60 mL of an aqueous solution containing 20 mL of ethylene glycol;

[0061] (6) Add 2 mmol of bismuth nitrate and potassium iodide solution to step (5) and add 2 mmol of bismuth nitrate and potassium iodide solution according to Cl - :I - The molar ratio R=8:1 was prepared;

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

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

[0064] Example 4

[0065] (1) Preparation of solution

[0066] Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in deionized water and mixed evenly to prepare Bi 3+ Bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) solution;

[0067] Dissolve potassium chloride (KCl) in deionized water and mix well to prepare Cl - Potassium chloride (KCl) solution with a concentration of 1 mol / L;

[0068] Dissolve potassium iodide (KI) in deionized water and mix well to prepare I - Potassium iodide (KI) solution with a concentration of 1 mol / L;

[0069] (2) Add 2 mmol of potassium chloride and potassium iodide solution prepared in step (1) to 60 mL of deionized water solution and continue stirring for 30 min. - :I - =8:1 for preparation;

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

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

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

[0073] Example 5

[0074] (1) Preparation of solution

[0075] Bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) was dissolved in deionized water and mixed evenly to prepare Bi 3+ Bismuth nitrate (Bi(NO 3 ) 3 ·5H 2 O) solution;

[0076] Dissolve potassium chloride (KCl) in deionized water and mix well to prepare Cl - Potassium chloride (KCl) solution with a concentration of 1 mol / L;

[0077] Dissolve potassium iodide (KI) in deionized water and mix well to prepare I - Potassium iodide (KI) solution with a concentration of 1 mol / L;

[0078] (2) Add 2 mmol of potassium chloride and potassium iodide solution prepared in step (1) to 60 mL of deionized water solution and continue stirring for 30 min. - :I - =4:1 for preparation;

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

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

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

Claims

1. A method for preparing a BiOCl / BiOI composite catalyst for visible light degradation of rhodamine B, characterized in that: The preparation method of BiOCl / BiOI heterojunction has the following steps: (1) adding bismuth nitrate solution and potassium chloride solution to deionized water solution in a molar ratio of 1:1 and stirring continuously for 30 minutes; the volume ratio of bismuth nitrate, potassium chloride and deionized water is 2:1:30; The Bi(NO3)3·5H2O solution contains 3+ The concentration is 0.5 mol / L; The Cl in the potassium chloride (KCl) solution - The concentration is 1 mol / L; The potassium iodide (KI) solution contains - The concentration is 1 mol / L; (2) adding sodium hydroxide or nitric acid dropwise to the solution in step (1) to adjust the pH value of the solution to 10, stirring thoroughly to obtain a uniform suspension; then transferring the suspension to a hydrothermal reactor and reacting the mixture in an oven preheated to 180° C. for 24 h; (3) The hydrothermal product is centrifuged and dried to obtain a BiOCl precursor; (4) ultrasonically dispersing the BiOCl precursor powder obtained in step (3) in an aqueous solution containing ethylene glycol, wherein the volume ratio of ethylene glycol to deionized water is 1:2, and the volume of the solution is the same as that in step (1); (5) adding bismuth nitrate solution and potassium iodide solution to step (4) to prepare a solution with a molar ratio of BiOCl:BiOI of R=8:1; (6) The mixed solution obtained in step (5) was reacted in a 60° C. water bath for 30 min; (7) The water bath product is centrifuged and dried to obtain a BiOCl / BiOI heterojunction.

2. A method for preparing a BiOCl / BiOI composite catalyst for degradation of rhodamine B under visible light, characterized in that: The preparation method of BiO(Cl,I) solid solution comprises the following steps: A. Add potassium chloride and potassium iodide solution to deionized water solution and continue stirring for 30 minutes. - :I - =8:1 and 4:1, the total volume of potassium chloride and potassium iodide solution and the volume ratio of deionized water are 1:30; The Cl in the potassium chloride (KCl) solution - The concentration is 1 mol / L; The potassium iodide (KI) solution contains - The concentration is 1 mol / L; B. Add bismuth nitrate solution to step (A) and 3+ :(Cl - +I - ) was prepared at a molar ratio of 1:1; The Bi(NO3)3·5H2O solution contains 3+ The concentration is 0.5 mol / L; C. The mixed solution obtained in step (B) was reacted in a 60° C. water bath for 30 min; D. The water bath product is centrifuged and dried to obtain BiO(Cl,I) solid solution.

3. The preparation method according to claim 1 or 2, characterized in that: In steps (3), (7) and (D), the centrifugal separation process is: washing three times with deionized water and rinsing once with alcohol.

4. The preparation method according to claim 1 or 2, characterized in that: In steps (3), (7) and (D), the drying temperature is 70° C. and the drying time is 24 h.

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