Preparation method and application of polyion liquid modified bismuth oxygen bromide photocatalyst

Abstract

The invention provides a preparation method of a polyion liquid modified bismuth oxygen bromide photocatalyst, which comprises the following steps: dissolving 1-vinyl-3-butylimidazolium bromide in acetone, and adding Bi (NO3) 3.5 H2O to obtain a precursor solution; and dropwise adding a cross-linking agent, adding an initiator azodiisobutyronitrile, reacting, washing, and drying to obtain the product. The invention further provides application, and the photocatalyst is used for photocatalytic CO2 reduction reaction and used for degrading tetracycline in a water body. The light absorption capacity of the material is enhanced through an in-situ cross-linking polymerization strategy, the charge separation efficiency and stability are improved, and the catalyst can be applied to photocatalytic CO2 reduction and organic pollutant degradation.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and particularly relates to a preparation method and application of a polyionic liquid-modified bismuth oxybromide photocatalyst. Background Art

[0002] As a special type of SBB material, bismuth halide (BiOX) plays a crucial role in visible light-driven photocatalytic applications, such as antibiotic degradation, overall water splitting, carbon dioxide reduction, N2 fixation, hydrogen peroxide production, selective organic synthesis, and photoelectrochemical reactions. However, pure-phase BiOX is physically restricted by the strong Coulomb force interaction between electron-hole pairs on its [Bi2O2] 2+ layer, resulting in an exciton effect. The recombination of electron-hole pairs will compete with the generation of free carriers, which greatly affects the photocatalytic efficiency. To reduce the recombination of electron-hole pairs, preparing ultrathin two-dimensional nanosheets is a relatively good method. In thinner nanosheets, the electrons and holes generated by light require a shorter migration distance to diffuse from the interior or bulk to the surface, which is more conducive to the reaction. However, the BiOBr material in the prior art has the following defects: (1) a high recombination rate of photo-generated electron-hole pairs, resulting in low photocatalytic efficiency; (2) poor affinity with catalytic substrates; (3) easy aggregation of nanosheets and insufficient stability. Currently, most improvement methods are to prepare ultrathin nanosheets or doping modification, but it is difficult to simultaneously improve the photocatalytic activity and material stability.

[0003] As a green solvent, ionic liquid (IL) can self-assemble into micelles, increasing the porosity in materials. Due to its unique properties such as extremely low volatility, high ionic conductivity, good solubility, designable structure, and wide electrochemical window, it has been widely used as a novel reaction medium in organic reactions and electrochemical devices. They have been used as solvents, templates, or reactants for synthesizing inorganic nanomaterials with new morphologies and improved properties. Polyionic liquid (PIL) has designability, high ionic conductivity, and hydrophilicity, and can be used as a functional modifier. Although existing studies have attempted to use ionic liquids in material synthesis, there is no technology involving constructing an internal electric field through a cross-linking polymerization strategy to enhance the charge separation efficiency. Therefore, developing an efficient and stable BiOBr-based composite material modified with polyionic liquid has important value in the field of photocatalysis. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method and application of a polyionic liquid-modified bismuth oxybromide photocatalyst in view of the above deficiencies of the prior art. This method enhances the light absorption ability, charge separation efficiency, and stability of the material through an in-situ cross-linking polymerization strategy, and expands its application in photocatalytic CO2 reduction and organic pollutant degradation.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst, and the method is as follows: S1. Dissolve 1-vinyl-3-butylimidazolium bromide in acetone, and then add Bi(NO3)3·5H2O. After stirring, a precursor solution is obtained; S2. Under the condition of a temperature of 50 °C, add a crosslinking agent dropwise to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 75 °C - 80 °C, add an initiator azobisisobutyronitrile, and react at a constant temperature for 2.5 h to obtain a reaction product; S3. Wash and dry the reaction product obtained in S2 to obtain a polyionic liquid-modified bismuth oxybromide photocatalyst, named BiOBr-PIL composite material.

[0006] Preferably, the molar ratio of Bi(NO3)3·5H2O to 1-vinyl-3-butylimidazolium bromide in S1 is 1:(1 - 4).

[0007] Preferably, the molar ratio of Bi(NO3)3·5H2O to 1-vinyl-3-butylimidazolium bromide is 1:3.

[0008] Preferably, the temperature during stirring in S1 is 50 °C and the stirring time is 1.5 h; the washing method in S3 is: alternately wash with ultrapure water and absolute ethanol for a total of 3 times; the drying temperature in S3 is 70 °C and the drying time is 12 h.

[0009] Preferably, the crosslinking agent in S2 is divinylbenzene.

[0010] Preferably, the average specific surface area of the polyionic liquid-modified bismuth oxybromide photocatalyst in S3 is 10.9 m 2 / g - 28 m 2 / g, and the average pore diameter is 17 nm - 25 nm.

[0011] The present invention also provides an application of the polyionic liquid-modified bismuth oxybromide photocatalyst prepared by the above preparation method. The polyionic liquid-modified bismuth oxybromide photocatalyst is used for photocatalytic CO2 reduction reaction to generate CO and methane.

[0012] Preferably, when the polyionic liquid-modified bismuth oxybromide photocatalyst is used for the CO2 reduction reaction, the generation rate of CO is 4.33 μmol / g / h - 41.66 μmol / g / h.

[0013] The present invention also provides the application of the poly(ionic liquid)-modified bismuth oxybromide photocatalyst prepared by the above preparation method, characterized in that the poly(ionic liquid)-modified bismuth oxybromide photocatalyst is used for photocatalytic degradation of tetracycline in water bodies.

[0014] Preferably, the degradation rate of the tetracycline is 38.32294% - 86.73469%.

[0015] The present invention has the following advantages compared with the prior art: 1. The poly(ionic liquid)-modified BiOBr photocatalyst (BOB-PIL) prepared by the present invention enhances the light absorption ability, charge separation efficiency and stability of the material through an in-situ cross-linking polymerization strategy. The present invention also expands its applications in photocatalytic CO2 reduction and degradation of organic pollutants.

[0016] 2. The light absorption range of the poly(ionic liquid)-modified bismuth oxybromide photocatalyst prepared by the present invention is extended to 480 nm, and the band gap is reduced to 2.78 eV; the lifetime of photo-generated carriers is extended to 0.0285 s, and the electron-hole recombination rate is significantly reduced; the CO2 reduction efficiency is as high as 41.66 μmol / g / h, and the degradation rate of tetracycline is as high as 86.73469% within 90 min; the performance retention rate is ≥75% after 4 cycles of use, and the stability is significantly improved.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the preparation process of BiOBr-PIL in Example 1 of the present invention.

[0019] Figure 2 It is a comparison diagram of TEM and element distribution of BiOBr prepared in Comparative Example 1 and BiOBr-PIL prepared in Example 1 of the present invention ((a) HRTEM image of BiOBr (the upper right corner is the TEM image); (b) TEM image of BiOBr-PIL and (c) and (d) HRTEM images; (e) dark field image of BiOBr-PIL; (f-k) EDS element mappings of C and Br (f), Bi (g), Br (h), O (i), C (j) and N (k)).

[0020] Figure 3 It is the XRD (a) and FT-IR spectra (b) of BiOBr-PIL prepared in Example 1 of the present invention, BiOBr in Comparative Example 1 and PIL in Comparative Example 2.

[0021] Figure 4N2 adsorption - desorption isotherms (a) and pore size distribution diagrams (b) of BiOBr - PIL prepared in Example 1 of the present invention, BiOBr of Comparative Example 1, and PIL of Comparative Example 2; N2 adsorption - desorption isotherms (c) and pore size distribution diagrams (d) of BiOBr - PIL, BiOBr - PIL - 1:1, BiOBr - PIL - 1:2, and BiOBr - PIL - 1:4 prepared in Examples 1 - 4.

[0022] Figure 5 XPS O 1s spectra (a) and EPR spectra (b) of BiOBr - PIL prepared in Example 1 of the present invention and BiOBr of Comparative Example 1.

[0023] Figure 6 UV - Vis diffuse reflectance absorption spectra of BiOBr - PIL prepared in Example 1 of the present invention, BiOBr of Comparative Example 1, and PIL of Comparative Example 2.

[0024] Figure 7 Photocurrent response (a), impedance (b), Bode plot (c), and PL spectrogram (d) of BiOBr - PIL prepared in Example 1 of the present invention, BiOBr of Comparative Example 1, and PIL of Comparative Example 2.

[0025] Figure 8 CO2 reduction efficiency diagrams (a) of BiOBr - PIL prepared in Example 1, BiOBr of Comparative Example 1, and PIL of Comparative Example 2 in Example 5 of the present invention; 20 h CO2 reduction efficiency diagram (b) of BiOBr - PIL of Example 1; CO2 reduction efficiency diagrams (c) of BiOBr - PIL - 1:1, BiOBr - PIL - 1:2, BiOBr - PIL, BiOBr - PIL - 1:4 of Examples 1 - 4.

[0026] Figure 9 Tetracycline degradation curve diagrams (a) and degradation efficiency diagrams (b) of BiOBr - PIL prepared in Example 1, BiOBr of Comparative Example 1, and PIL of Comparative Example 2 in Example 6 of the present invention; tetracycline degradation curve diagrams (c) and degradation efficiency diagrams (d) of BiOBr - PIL - 1:1, BiOBr - PIL - 1:2, BiOBr - PIL, BiOBr - PIL - 1:4 of Examples 1 - 4.

[0027] Figure 10 4 - cycle degradation experiment (a) of BiOBr - PIL prepared in Example 1 of the present invention; XRD patterns (b) before and after degradation. Detailed implementation manners

[0028] Example 1 Preparation method of polyionic liquid-modified bismuth oxybromide photocatalyst in this embodiment: Crosslinking agent S1: Dissolve 6 mmol of ionic liquid monomer 1-vinyl-3-butylimidazolium bromide (VBImBr) in 8 mL of acetone, then add 2 mmol of Bi(NO3)3·5H2O, and stir at 50 °C for 1.5 h to obtain a precursor solution; S2: At 50 °C, add 0.5 g of crosslinking agent divinylbenzene (C 10 H 10 ) dropwise to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 80 °C, add 0.5 g of initiator azobisisobutyronitrile (AIBN, chemical formula C8H 12 N4), and react at a constant temperature for 2.5 h. While forming BiOBr nanosheets, the ionic liquid and the crosslinking agent crosslink and polymerize under the initiation of the initiator to form polyionic liquid and wrap it on the surface of the BiOBr nanosheets to obtain a reaction product; Figure 1 This is the preparation process of the BOB-PIL composite material prepared in Example 1 of the present invention. First, Bi(NO3)3·5H2O and VBImBr (C9H 15 BrN2) react with Br - ions to generate BiOBr nanosheets. Then, under the action of the AIBN radical initiator, the vinyl double bonds in VBImBr and DVB (divinylbenzene) are opened, and chain growth is initiated to crosslink into a PIL (polyionic liquid) network structure and coat it on the surface of BiOBr. The crosslinked polyionic liquid network restricts the further stacking of BiOBr, obtains ultrathin nanosheets, increases the oxygen vacancies on the surface of BiOBr, broadens the light absorption range of BiOBr, and further improves the photocatalytic performance.

[0029] S3: Wash the reaction product obtained in S2, wash it alternately with ultrapure water and absolute ethanol for a total of 3 times, and then dry it at 70 °C for 12 h to obtain a polyionic liquid-modified bismuth oxybromide photocatalyst with an average specific surface area of 26.9 m 2 / g and an average pore diameter of 25 nm, which is the BiOBr-PIL composite material, named BiOBr-PIL composite material (also denoted as BiOBr-PI-1:3).

[0030] The BiOBr-PIL composite material prepared in Example 1 of this invention is composed of BiOBr nanosheets and crosslinked polyionic liquid, and is rich in bromine on the surface and has oxygen vacancy defects.

[0031] Comparative Example 1 Preparation method of the catalyst in this comparative example: S1. Dissolve 6 mmol of KBr in 8 mL of acetone, then add 2 mmol of Bi(NO3)3·5H2O, and stir for 1.5 h at a temperature of 50 °C to obtain a precursor solution; S2. Dropwise add 0.5 g of crosslinking agent divinylbenzene to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 80 °C, add 0.5 g of initiator azobisisobutyronitrile (AIBN), and react at a constant temperature for 2.5 h to obtain a reaction product; S3. Wash the reaction product obtained in S2, wash it alternately with ultrapure water and absolute ethanol for a total of 3 times, and then dry it at a temperature of 70 °C for 12 h to obtain a bismuth oxybromide material without polyionic liquid modification with an average specific surface area of 10.6 m 2 / g, named BiOBr, and this BiOBr has no polyionic liquid coating.

[0032] Comparative Example 2 The preparation method of the catalyst in this comparative example is as follows: S1. Dissolve 6 mmol of 1-vinyl-3-butylimidazolium bromide (VBImBr) in 8 mL of acetone, and stir for 1.5 h at a temperature of 50 °C to obtain a precursor solution; S3. Dropwise add 0.5 g of crosslinking agent divinylbenzene to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 80 °C, add 0.5 g of initiator azobisisobutyronitrile (AIBN), and react at a constant temperature for 2.5 h to obtain a reaction product; S4. Wash the reaction product obtained in S3, wash it alternately with ultrapure water and absolute ethanol for a total of 3 times, and then dry it at a temperature of 70 °C for 12 h to obtain polyionic liquid PIL, named PIL. Figure 2 It is a TEM and elemental distribution comparison chart of BiOBr prepared in Comparative Example 1 of the present invention and BiOBr-PIL prepared in Example 1, Figure 2 (a) The TEM image in the upper right corner shows that BiOBr obtained from inorganic salts tends to stick together to form an aggregated BiOBr, and the HRTEM image clearly shows that there is no cladding on the surface of BiOBr. Figure 2 (b) In the figure, due to the adsorption of VBIm+ chains on the surface of BiOBr, the aggregation of flaky BiOBr is hindered, so the formed BiOBr-PIL is highly dispersed nanosheets, and it can be seen that BiOBr wrapped with PIL is thinner nanosheets. Figure 2 (c) The HRTEM of BiOBr-PIL shows that BiOBr is wrapped in an imidazolium-based crosslinked polymer of about 3.5 nm (separated by the yellow line). Figure 2(d) shows a large number of defect points marked with green circles in BOB-PIL. Figure 2 (e-f) are the EDS-mapping element mapping group diagrams of BOB-PIL, showing that the C element is wrapped on the surface of BiOBr, indicating the successful preparation of BiOBr-PIL.

[0033] Figure 3 The XRD and FT-IR diagrams of BiOBr and PIL prepared in Comparative Examples 1-2 of the present invention and BiOBr-PIL prepared in Example 1. From Figure 3 (a), it can be seen that the prepared composite catalyst BiOBr-PIL has exactly the same crystal phase as BiOBr, and this material is free of impurities and relatively pure. Figure 3 In (b), the peak at 523 cm -1 of BiOBr and PIL-BiOBr can be attributed to the valence symmetric A 2u -type vibration of the Bi-O bond, the peak at 3129 cm -1 can be attributed to the C-C bond at the 4th and 5th positions of the imidazole ring, the peak at 2959 cm -1 can be attributed to the stretching vibration of the H-C-H bond in -CH3 and the -CH2- bond in butyl, the peak at 1561 cm -1 can be attributed to the stretching vibration of the carbon-nitrogen heterocycle, and the peak at 1158 cm-1 can be attributed to the bending vibration of the imidazole ring. The above four positions have obvious peaks in both the BiOBr-PIL and PIL samples, while there is no such vibration peak in the BiOBr sample, indicating that BiOBr-PIL has been successfully coated with polyionic liquid.

[0034] Figure 4 The N2 adsorption-desorption isotherms of BiOBr and PIL prepared in Comparative Examples 1-2 of the present invention and BiOBr-PIL prepared in Examples 1-4. It can be seen from the figure that the porosity and specific surface area of the polyionic liquid-modified BiOBr-PIL composite photocatalyst have both increased, thereby increasing the active sites of the reaction and contributing to the improvement of the photocatalytic performance.

[0035] Figure 5 The XPS O1s spectra and EPR spectra of BiOBr and PIL prepared in Comparative Examples 1-2 of the present invention and BiOBr-PIL prepared in Example 1. From Figure 5 (a), it can be seen that the area of oxygen vacancies has increased, indicating that the introduction of PIL can increase the number of oxygen vacancies. At the same time Figure 5 (b) shows that the signal peak intensity of oxygen vacancies in the BiOBr-PIL sample has increased. It shows that the introduction of PIL helps to increase the oxygen vacancy concentration.

[0036] Figure 6UV-visible diffuse reflectance absorption spectra of BiOBr and PIL prepared in Comparative Examples 1-2 of the present invention and BiOBr-PIL prepared in Example 1. It shows that BiOBr-PIL effectively expands the light absorption range of the catalyst, and the light absorption intensity of BiOBr-PIL is significantly enhanced in the region of 300-500 nm, which is mainly attributed to the fact that the imidazolium cross-linked polymer can improve the light absorption performance. Figure 7 Photocurrent response (a), impedance (b), Bode plot (c) and PL spectrogram (d) of BiOBr and PIL prepared in Comparative Examples 1-2 of the present invention and BiOBr-PIL prepared in Example 1. From Figure 7 It can be seen from (a) that the photocurrent response of BiOBr-PIL is better than that of BiOBr and PIL. This improvement in photocurrent is mainly due to the fact that the imidazolium cross-linked polymer wrapped on the surface of BiOBr ultimately improves the separation efficiency of electron-hole pairs. Figure 7 In (b), the radius of the arc of BiOBr-PIL is the smallest, which also indicates that the formation of BiOBr-PIL can accelerate the interfacial charge transfer. Figure 7 Compared with BiOBr, the carrier lifetime of BiOBr-PIL is extended from 0.0277 s to 0.0285 s, indicating that the polyionic liquid wrapped on BiOBr can effectively inhibit the recombination of electrons and holes. Figure 7 In (d), the photoluminescence spectrum intensity of BiOBr-PIL is slightly lower than that of BiOBr, indicating that the recombination rate of photo-generated electron-hole pairs under illumination is lower. The results show that BiOBr-PIL has higher photocurrent, smaller interfacial transfer resistance, longer electron lifetime and higher photo-generated electron-hole separation ability.

[0037] Example 2 Preparation method of the polyionic liquid modified bismuth oxybromide photocatalyst in this example. The method is as follows: Cross-linking agent S1: Dissolve 2 mmol of 1-vinyl-3-butylimidazolium bromide (VBImBr) in 8 mL of acetone, then add 2 mmol of Bi(NO3)3·5H2O, and stir at a temperature of 50 °C for 1.5 h to obtain a precursor solution; S2: At a temperature of 50 °C, add 0.5 g of the cross-linking agent obtained in S1 dropwise to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 75 °C, add 0.5 g of initiator azobisisobutyronitrile (AIBN), and react at a constant temperature for 2.5 h, so that the polyionic liquid VBImBr cross-links and polymerizes to wrap on the surface of BiOBr while forming BiOBr, to obtain a reaction product; S3: Wash the reaction product obtained in S2. Wash alternately with ultrapure water and absolute ethanol for a total of 3 times, and then dry at 70 °C for 12 h to obtain a poly(ionic liquid)-modified bismuth oxybromide photocatalyst with an average specific surface area of 28 m 2 / g and an average pore diameter of 25 nm, which is the BiOBr-PIL composite material, named BiOBr-PIL-1:1 composite material.

[0038] Example 3 The preparation method of the poly(ionic liquid)-modified bismuth oxybromide photocatalyst in this example is as follows: Crosslinking agent S1: Dissolve 4 mmol of 1-vinyl-3-butylimidazolium bromide (VBImBr) in 8 mL of acetone, then add 2 mmol of Bi(NO3)3·5H2O, and stir at 50 °C for 1.5 h to obtain a precursor solution; S2: At 50 °C, add 0.5 g of the crosslinking agent obtained in S1 dropwise to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 75 °C, add 0.5 g of initiator azobisisobutyronitrile (AIBN), and react at a constant temperature for 2.5 h, so that the poly(ionic liquid) VBImBr crosslinks and polymerizes to wrap on the surface of BiOBr while forming BiOBr, obtaining a reaction product; S3: Wash the reaction product obtained in S2, wash alternately with ultrapure water and absolute ethanol for a total of 3 times, and then dry at 70 °C for 12 h to obtain a poly(ionic liquid)-modified bismuth oxybromide photocatalyst with an average specific surface area of 25 m 2 / g and an average pore diameter of 20 nm, which is the BiOBr-PIL composite material, named BiOBr-PIL-1:2 composite material.

[0039] Example 4 The preparation method of the poly(ionic liquid)-modified bismuth oxybromide photocatalyst in this example is the same as that in Example 1, except that the amount of 1-vinyl-3-butylimidazolium bromide (VBImBr) in step S1 is 8 mmol, and the amount of Bi(NO3)3·5H2O is 2 mmol, obtaining a poly(ionic liquid)-modified bismuth oxybromide photocatalyst with an average specific surface area of 10.9 m 2 / g and an average pore diameter of 17 nm, named BiOBr-PIL-1:4 composite material.

[0040] Example 5 The poly(ionic liquid)-modified bismuth oxybromide photocatalysts prepared in Examples 1-4 can be used for photocatalytic CO2 reduction reaction to generate CO and methane. The photocatalytic CO2 reduction experiment is as follows: Disperse 50 mg of BiOBr-PIL (the catalysts BiOBr-PIL, BiOBr-PIL-1:1, BiOBr-PIL-1:2, BiOBr-PIL-1:4 prepared in Examples 1, 2, 3, and 4) and the catalysts (BiOBr, PIL) prepared in Comparative Examples 1 and 2 respectively in 50 mL of an aqueous solution containing triethanolamine (45 mL of water and 5 mL of triethanolamine), and ultrasonicate for 0.5 h to uniformly disperse the catalysts in the solution. First, evacuate the reaction system under dark conditions for about 0.5 h to remove the air in the system. Introduce CO2, circulate for 0.5 h, and then irradiate with a 300 W xenon lamp for 5 h. Detect the reduction product CO with an on-line gas chromatograph every 0.5 h. As Figure 8 shown, the CO production rate of BiOBr-PIL is finally calculated to be 41.66 μmol / g / h, and the production efficiency is 3 times higher than that of pure BiOBr.

[0041] Figure 8 This is the CO2 reduction efficiency diagram of BiOBr-PIL prepared in Examples 1-4 of the present invention, BiOBr of Comparative Examples 1-2, and PIL. From Figure 8 Figure (a), it can be obtained that after irradiating with a 300 W Xe lamp for 5 h, compared with the PIL and BiOBr samples, the CO production rates of the BiOBr-PIL samples are increased from 20.18 μmol / g / h and 14.27 μmol / g / h to 41.66 μmol / g / h respectively, indicating that the photocatalytic performance of the BiOBr-PIL composite material is superior to that of individual PIL and BiOBr. Figure 8 Figure (b) shows the long-term photocatalytic CO2 reduction performance of BiOBr-PIL, indicating that BiOBr-PIL has high stability. From Figure 8 Figure (c), the CO production rates of the BiOBr-PIL-1:1, BiOBr-PIL-1:2, BiOBr-PIL, and BiOBr-PIL-1:4 samples are 4.33, 29.25, 41.66, and 14.10 μmol / g / h respectively. This data shows that a BiOBr-PIL with oxygen vacancies and a bromine-rich state can be prepared with an appropriate stoichiometric ratio of Br / Bi, improving the photocatalytic CO2 reduction performance.

[0042] Example 6 In this example, the poly(ionic liquid)-modified bismuth oxybromide photocatalyst prepared in Examples 1-4 can be used to degrade tetracycline in water. The tetracycline degradation experiment is as follows: Disperse 30 mg of BiOBr-PIL (the catalysts BiOBr-PIL-1:1, BiOBr-PIL-1:2, BiOBr-PIL, BiOBr-PIL-1:4 prepared in Examples 1 to 4) and the catalysts (BiOBr, PIL) prepared in Comparative Examples 1 to 2, and use the sample without adding a catalyst as the blank sample (blank), and disperse them separately in 50 mL of an aqueous solution containing 50 mg / L of tetracycline (TC). Ultrasonicate for 1 h under dark conditions to uniformly disperse the catalyst in the solution and complete adsorption. Under the irradiation of a 300 W xenon lamp, 0.25 mL of the liquid is taken every 15 min, and the photocatalyst particles are filtered off with a 0.45 μm filter. As Figure 6 shown, after a total of 90 min of illumination, the degradation rate reaches 86.7%, and the degradation efficiency is 2 times higher than that of pure BiOBr.

[0043] Figure 9 This is the degradation curve and degradation efficiency diagram of BiOBr-PIL prepared in Examples 1 to 4, BiOBr and PIL in Comparative Examples 1 to 2 in Application Example 2 of the present invention. Figure 9 The results of the blank experiment in (a) show that under the condition of not adding a catalyst, TC is hardly decomposed under visible light irradiation. Under the condition of 90 min of illumination, the degradation rate of TC by PIL and BiOBr reaches about 40%, and the degradation rate of BiOBr-PIL can reach 86.73469%. Figure 9 (b) The kinetic rate constant of BiOBr-PIL is 0.01946 min -1 . Figure 9 The degradation effect of BiOBr-PIL with different Br / Bi stoichiometric ratios on TC in (c-d) shows that the degradation efficiency is generally BiOBr-PIL > BiOBr-PIL-1:4 > BiOBr-PIL-1:2 > BiOBr-PIL-1:1. The degradation rates of tetracycline under the samples of BiOBr-PIL-1:1, BiOBr-PIL-1:2, BiOBr-PIL, BiOBr-PIL-1:4 are 49.26052%, 38.32294%, 86.73469%, 67.843327% respectively. It is confirmed that the catalysts prepared in Examples 1 to 4 have good degradation of tetracycline, and among them, BiOBr-PIL has a higher photocatalytic degradation efficiency of tetracycline.

[0044] Figure 10 This is the 4-cycle degradation experiment (a) of BiOBr-PIL prepared in Example 1 of the present invention; the XRD patterns before and after degradation (b). Figure 10 The cyclic photocatalytic degradation experiment in (a) shows that BiOBr-PIL has good cyclic performance. After 4 cycles, the degradation rate changes from 86.73469% to 68%. At the same timeFigure 10 As shown in (b), it can be seen from the comparison of XRD before and after the reaction that the crystal structure of BiOBr-PIL has not changed, indicating that the catalyst has good stability.

[0045] In the preparation methods of Examples 1 to 4 of the present invention, the ionic liquid (VBImBr) acts as a bromine source and a surfactant (containing N element), decomposes when heated, dopes heteroatoms into the catalyst lattice, narrows the band gap, and expands the light response range. Then, through an in-situ cross-linking polymerization strategy, during the polymerization reaction, DVB is introduced or the reactive groups of VBImBr itself are used to directly form a chemical cross-linking network between polymer chains, thereby constructing a polyionic liquid with a three-dimensional (3D) stable structure in one step, which not only enhances the structural stability, light corrosion resistance and durability of the BOB-PIL catalyst, but also enhances the light absorption ability, charge separation efficiency and stability of the material.

[0046] Combined with the cross-linking polymerization strategy, a polyionic liquid coating layer is constructed on the surface of BiOBr nanosheets to form a built-in electric field, significantly improving the photo-generated charge separation efficiency. The band gap of this material is as low as 2.78 eV, and the light absorption range is extended to 480 nm. It shows high activity and stability in CO2 reduction and tetracycline degradation, and is suitable for the fields of environmental governance and energy conversion. The present invention also expands its applications in photocatalytic CO2 reduction and organic pollutant degradation.

[0047] In summary, the polyionic liquid-modified bismuth oxybromide photocatalyst prepared by the present invention can be used for photocatalytic reduction of CO2 to produce CO and methane, and photocatalytic degradation of antibiotic pollutants (such as tetracycline) in water.

[0048] The light absorption range of the polyionic liquid-modified bismuth oxybromide photocatalyst prepared by the present invention is extended to 480 nm, and the band gap is reduced to 2.78 eV; the lifetime of photo-generated carriers is extended to 0.0285 s, and the electron-hole recombination rate is significantly reduced; the CO2 reduction efficiency reaches 4.33 μmol / g / h to 41.66 μmol / g / h, and the tetracycline degradation rate reaches 38.32294% to 86.73469% within 90 min; the performance retention rate is ≥75% after 4 cycles of use, and the stability is significantly improved.

[0049] The above are only the preferred embodiments of the present invention, and do not limit the present invention in any way. Any simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a polyionic liquid modified bismuth oxybromide photocatalyst, characterized in that, The method is as follows: S1. Dissolve 1-vinyl-3-butylimidazolium bromide in acetone, and then add Bi(NO3)3·5H2O. After stirring, a precursor solution is obtained; S2. Under the condition of a temperature of 50 °C, add a crosslinking agent dropwise to the precursor solution obtained in S1, react at a constant temperature for 2 h, then raise the temperature to 75 °C - 80 °C, add an initiator azobisisobutyronitrile, and react at a constant temperature for 2.5 h to obtain a reaction product; S3. Wash and dry the reaction product obtained in S2 to obtain a polyionic liquid-modified bismuth oxybromide photocatalyst, named BiOBr-PIL composite material.

2. The preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst according to claim 1, wherein The molar ratio of Bi(NO3)3·5H2O to 1-vinyl-3-butylimidazolium bromide described in S1 is 1:(1 - 4).

3. The preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst according to claim 2, characterized in that The molar ratio of Bi(NO3)3·5H2O to 1-vinyl-3-butylimidazolium bromide is 1:

3.

4. The preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst according to claim 1, characterized in that The temperature during stirring in S1 is 50 °C, and the stirring time is 1.5 h; the washing method in S3 is: wash alternately with ultrapure water and absolute ethanol for a total of 3 times; the drying temperature in S3 is 70 °C, and the drying time is 12 h.

5. The preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst according to claim 1, characterized in that, The crosslinking agent described in S2 is divinylbenzene.

6. The preparation method of a polyionic liquid-modified bismuth oxybromide photocatalyst according to claim 1, characterized in that, The average specific surface area of the poly(ionic liquid)-modified bismuth oxybromide photocatalyst described in S3 is 10.9 m 2 / g to 28 m 2 / g, and the average pore size is 17 nm to 25 nm.

7. Use of a polyionic liquid-modified bismuth oxybromide photocatalyst prepared by the preparation method according to any one of claims 1-6, characterized in that, The polyionic liquid-modified bismuth oxybromide photocatalyst is used for the photocatalytic CO2 reduction reaction to generate CO and methane.

8. The application according to claim 7, characterized in that, When the polyionic liquid-modified bismuth oxybromide photocatalyst is used for the CO2 reduction reaction, the generation rate of CO is 4.33 μmol / g / h - 41.66 μmol / g / h.

9. Use of a polyionic liquid-modified bismuth oxybromide photocatalyst prepared by the preparation method according to any one of claims 1-6, characterized in that, The polyionic liquid-modified bismuth oxybromide photocatalyst is used for photocatalytic degradation of tetracycline in water.

10. The application according to claim 9, wherein The degradation rate of the tetracycline is 38.32294% - 86.73469%.

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