Composite BiOCl / SiNWs material as well as preparation method and application thereof

Abstract

The invention discloses a composite BiOCl / SiNWs material and a preparation method and application thereof, and the preparation method comprises the following steps: synthesizing BiOCl nanoparticles by a steam thermal method, and loading the BiOCl nanoparticles on a silicon nanowire substrate by a deposition method to form the composite BiOCl / SiNWs material. Wherein the silicon nanowire array substrate is prepared by adopting a metal auxiliary chemical etching method, the scattering probability of incident light can be enhanced by the array structure, and the absorption efficiency of the silicon substrate to visible light can be improved. The BiOCl and the silicon nanowire array substrate can form a heterojunction structure, so that the separation and migration rate of photon-generated carriers is increased, and the recombination probability of the photon-generated carriers is reduced, thereby effectively improving the photoelectric property of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a composite BiOCl / SiNWs material and a preparation method and application thereof. Background Art

[0002] With the rapid rise of the antibiotic market, antibiotics have been abused and improperly handled, resulting in a wide distribution range, high concentration, and a variety of antibiotic pollution in water bodies. In addition, antibiotic wastewater also has the characteristics of high chroma and large pH fluctuations. Excessive concentration of antibiotics in water bodies will increase bacterial resistance and seriously threaten human health. Therefore, in response to the increasingly difficult problem of water pollution, it is necessary and urgent to find green, efficient and environmentally friendly antibiotic treatment technology. At present, photoelectrocatalytic degradation has attracted the attention of researchers due to its advantages such as simple degradation process, environmental friendliness, and good degradation performance.

[0003] Silicon (Si) has the advantages of abundant reserves, low price, stable physical and chemical properties and non-toxicity. In addition, the unique narrow band gap (1.12eV) of silicon can absorb sunlight from ultraviolet (UV) to near infrared (NIR), making it a potential photoanode. However, silicon has a high refractive index, few active sites, a high recombination rate of photogenerated carriers, and a valence band position far below the oxidation potential of hydroxyl radicals (~1.99eV); these shortcomings lead to low light utilization and weak valence band hole oxidation ability on the one hand; on the other hand, silicon is difficult to generate active free radicals with high oxidation ability, so it is difficult for silicon to directly oxidize and degrade pollutants, limiting its efficiency in photoelectrocatalytic degradation of pollutants and its application in this regard. How to apply silicon to photoelectrocatalytic degradation of pollutants has become a difficult problem that needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a composite BiOCl / SiNWs material and a preparation method and application thereof, which can accelerate the separation and migration rate of photogenerated carriers and reduce the recombination probability of photogenerated carriers, thereby effectively improving the photoelectric performance of the material.

[0005] In one aspect of the present invention, the present invention provides a composite BiOCl / SiNWs material. According to an embodiment of the present invention, BiOCl nanoparticles are loaded on the surface of SiNWs to form the composite BiOCl / SiNWs material.

[0006] In another aspect of the present invention, the present invention provides a method for preparing a composite BiOCl / SiNWs material. According to an embodiment of the present invention, the method comprises the following steps: synthesizing BiOCl nanoparticles by a steam thermal method, and then loading the BiOCl nanoparticles onto a silicon nanowire substrate by a deposition method to form a composite BiOCl / SiNWs material.

[0007] In addition, the method for preparing a composite BiOCl / SiNWs material according to the above embodiment of the present invention may also have the following additional technical features:

[0008] In some embodiments of the present invention, the steam thermal method comprises the following steps:

[0009] (1) BiCl 3 Put it into ethylene glycol solution and ultrasonicate to obtain BiCl 3 Ethylene glycol mixed solution;

[0010] (2) Pour the isopropanol solution into the container of the reactor and put the bracket into it;

[0011] (3) Place SiNWs in a solution of BiCl 3 The ethylene glycol mixed solution is placed in a container, and the container is placed on a support for steam thermal reaction, wherein the temperature of the steam thermal reaction is 110-120° C. and the reaction time is 10-12 hours;

[0012] (4) Cleaning and drying the silicon wafer after the steam thermal reaction to obtain the composite BiOCl / SiNWs material.

[0013] In some embodiments of the present invention, the BiCl 3 The mass ratio of ethylene glycol and isopropanol is (50-80):(9-13):(31-47).

[0014] In some embodiments of the present invention, in step (3), the preparation method of SiNWs is as follows: the silicon wafer is pretreated and immersed in a Piranha mixed solution, and then sequentially placed in a silver deposition solution, an acid etching solution, and a silver removal solution to perform silver deposition, acid etching, and silver removal operations, and a metal-assisted chemical etching method is used to prepare a silicon nanowire array.

[0015] In some embodiments of the present invention, the Piranha mixed solution is H 2 SO 4 and H 2 O 2 The silver deposition solution is 0.01-0.05 mol / LAgNO 3 A mixed solution of an aqueous solution and a 4.6-5 mol / L HF aqueous solution; the acidic etching solution is 0.3-0.5 mol / L H 2 O 2 The desilvering solution is a mixed solution of nitric acid and deionized water in a volume ratio of 1:1 to 1:2.

[0016] In some embodiments of the present invention, the length and width of the silicon wafer are both 9 to 11 mm, the thickness is 450 to 550 μm, the resistivity is 0.02 to 0.05 Ω / cm, and the crystal orientation is (100); the method for pretreating the silicon wafer is as follows: a single-side polished n-type silicon wafer is sequentially placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning; the pretreated silicon wafer is immersed in the Piranha mixed solution at a temperature of 70 to 80° C. and a soaking time of 20 to 30 min; then the silicon wafer is ultrasonically cleaned with deionized water for 10 to 15 times, each time for 3 to 5 min, and then the silicon wafer is immersed in hydrofluoric acid with a concentration to remove the surface oxide layer; the silicon wafer is kept warm at 25 to 35° C. in the silver deposition solution, and silver particles are deposited for 1 to 10 min; the silicon wafer after the silver particles are deposited is kept warm at 25 to 35° C. in the acid etching solution, and etched for 10 to 30 min; the silicon wafer after acid etching is kept warm at 25 to 35° C. in the silver removal solution and soaked for 1 to 2 h.

[0017] In another aspect of the present invention, the present invention provides a photoanode material. According to an embodiment of the present invention, the photoanode material is the composite BiOCl / SiNWs material.

[0018] In another aspect of the present invention, the present invention provides a method for photoelectrocatalytic degradation of antibiotics. According to an embodiment of the present invention, the method comprises the following steps:

[0019] (1) A square electrolytic cell is used as a reaction cell, the composite BiOCl / SiNWs material is used as a photoanode, a platinum sheet electrode is used as a photocathode, and an aqueous solution containing antibiotics is used as an electrolyte;

[0020] (2) Using a xenon lamp light source to irradiate the photoanode and photocathode described in step (1), applying a bias voltage of 0.5 to 1.5 V to form a photoelectrochemical catalytic reaction, thereby degrading the antibiotics.

[0021] In addition, the photoelectrocatalytic degradation method of antibiotics according to the above embodiment of the present invention may also have the following additional technical features:

[0022] In some embodiments of the present invention, the xenon lamp light source is equipped with a filter with a cut-off wavelength of 420nm and a power of 300-400W.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Compared with untreated planar silicon, the treated silicon nanowire array has uniform size (about 6 μm in length), higher uniformity, and larger specific surface area. In addition, the nanowire array structure can increase the optical path of the incident light, effectively improving the absorption efficiency of visible light.

[0025] (2) BiOCl nanoparticles (with an average grain size of 6 to 20 nm) were prepared by steam thermal method. BiOCl nanoparticles can enter the silicon nanowire array structure and improve the stability of the silicon nanowire array substrate. In addition, BiOCl nanoparticles can act as active sites to expose more active sites on the silicon nanowire substrate. The heterojunction structure at the interface between SiNWs and BiOCl can form a built-in electric field. Under the interaction of interface electrons, e - Migrating from CB-BiOCl to VB-SiNWs forms a typical Z-scheme charge transfer system, which can effectively inhibit the recombination of photogenerated carriers, effectively improve the light absorption efficiency in the process of photoelectrocatalytic degradation of antibiotics, facilitate the transfer of carriers, and improve the photoelectrochemical activity of the silicon nanowire substrate.

[0026] (3) The composite BiOCl / SiNWs material of the present invention is used as a photoanode. The valence band position of BiOCl is higher than the oxidation potential of hydroxyl radicals. Under the action of light, OH - , ·O 2 - It can degrade antibiotics by free radicals, breaking down large-molecule antibiotic pollutants into small-molecule pollutants, water and carbon dioxide, which is environmentally friendly.

[0027] (4) The photoanode generates photogenerated electron-hole pairs (e - / h + ), the applied bias can delay e - / h + Compound. - and h + They can react to generate active free radicals with strong oxidizing effect, such as hydroxyl radical (·OH), hole (h + ) and superoxide radicals (·O 2 - ), etc., and then degrade antibiotic pollutants into small molecules of CO 2 and H 2 O, etc. The most fundamental way to improve catalytic activity is to inhibit the photogenerated electron-hole pairs (e - / h + ) compound. Applying a bias voltage can be used as an external driving force to - It is quickly transmitted to the external circuit and then transferred to the counter electrode to react with oxygen to produce water. - The photogenerated electrons in the photoanode are quickly removed from the conduction band, which greatly suppresses the photogenerated electrons in the photoanode. - With h + The compound, extending h + The photoelectric synergy improves the efficiency of photocatalytic degradation of antibiotics by BiOCl / SiNWs samples.

[0028] (5) Regarding the preparation method of BiOCl / SiNWs photoanode material, the process is simple, easy to operate, highly efficient and low-cost; and the BiOCl / SiNWs photoanode material is a macroscopic sheet material, which is easier to recycle and reuse than a single powder catalyst, and can effectively avoid secondary pollution of water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart for preparing the composite BiOCl / SiNWs material in Examples 2-5 of the present invention;

[0030] Figure 2 TEM image of the composite BiOCl / SiNWs material in Example 3 of the present invention;

[0031] Figure 3 is a linear sweep voltammetric curve of the photoelectrocatalyst (i.e., photoanode material) in the application example of the present invention;

[0032] Figure 4 is a degradation rate curve of the photoelectrocatalyst (i.e., photoanode material) in the application example of the present invention;

[0033] Figure 5 This is a mechanism analysis diagram of the photoelectrocatalytic degradation of antibiotic wastewater by the composite BiOCl / SiNWs material in the application example of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] A method for preparing SiNWs, using a two-step metal-assisted chemical etching method to prepare a silicon nanowire array, comprising the following steps:

[0037] (1) First, the n-type silicon wafer was pretreated. The length and width of the silicon wafer were both 10 mm, the thickness was 500 μm, the resistivity was 0.02 Ω / cm, and the crystal orientation was (100). The silicon wafer was placed in acetone, anhydrous ethanol, and deionized water for 20 minutes to remove organic matter. After drying, it was placed in a Piranha mixed solution (H 2 SO 4 and H 2 O 2), hydrothermally heated at 80°C for 20 minutes to remove the oxide layer, and then ultrasonically cleaned with deionized water 10 times (3 minutes each time). Then, the silicon wafer was immersed in 5wt% hydrofluoric acid to remove the surface oxide layer.

[0038] (2) Place the silicon wafer in a silver plating solution (4.8 mol / L HF and 0.02 mol / L AgNO 3 ) at 25℃ for 1min, rinse the excess Ag with deionized water and quickly put it into the etching solution (4.8mol / L HF and 0.3mol / L H 2 O 2 ) at 25℃ for 10min, and then cleaned with deionized water. Then put it into a silver removal solution (nitric acid and deionized water with a volume ratio of 1:1) at 25℃ for 2h, and then rinse with N 2 After drying, silicon nanowire arrays (denoted as SiNWs) were prepared and set aside.

[0039] Example 2

[0040] A method for preparing a composite BiOCl / SiNWs material comprises the following steps:

[0041] (1) 50 mg of BiCl 3 After being added to a beaker containing 8 ml of ethylene glycol solution, the mixture was ultrasonicated for 30 min, and the SiNWs prepared in Example 1 were placed in the beaker. Subsequently, the bracket and 40 ml of isopropanol solution were placed in a polytetrafluoroethylene reactor. Finally, the beaker was placed on the bracket of the reactor for steam thermal reaction, wherein the hydrothermal temperature was 110 ° C and the hydrothermal time was 10 h.

[0042] (2) After the steam thermal reaction, the silicon wafer was washed with anhydrous ethanol for several times and dried in a vacuum drying oven at 60° C. for 4 h to obtain the BiOCl / SiNWs material, which was recorded as BiOCl / SiNWs-50.

[0043] Example 3

[0044] like Figure 1 As shown, a method for preparing a composite BiOCl / SiNWs material comprises the following steps:

[0045] (1) 60 mg of BiCl 3 After being added to a beaker containing 8 ml of ethylene glycol solution, the mixture was ultrasonicated for 30 min, and the SiNWs prepared in Example 1 were placed in the beaker. Subsequently, the bracket and 40 ml of isopropanol solution were placed in a polytetrafluoroethylene reactor. Finally, the beaker was placed on the bracket of the reactor for steam thermal reaction, wherein the hydrothermal temperature was 110 ° C and the hydrothermal time was 10 h.

[0046] (2) The silicon wafer after the steam thermal reaction is washed with anhydrous ethanol for multiple times and dried in a vacuum drying oven at 60°C for 4 h to obtain the BiOCl / SiNWs material.

[0047] from Figure 2 It can be seen from the TEM image that the size of a single SiNWAs is about 200nm, and the tiny BiOCl nanoparticles are evenly attached to the surface of SiNWs. A small amount of nanoparticles agglomerate on the top of the nanowires to increase the size of SiNWs. Therefore, the BiOCl / SiNWs material was successfully prepared by steam thermal method, which was recorded as BiOCl / SiNWs-60.

[0048] Example 4

[0049] A method for preparing a BiOCl / SiNWs photoanode material comprises the following steps:

[0050] (1) 70 mg of BiCl 3 After being added to a beaker containing 8 ml of ethylene glycol solution, the mixture was ultrasonicated for 30 min, and the SiNWs prepared in Example 1 were placed in the beaker. Subsequently, the bracket and 40 ml of isopropanol solution were placed in a polytetrafluoroethylene reactor. Finally, the beaker was placed on the bracket of the reactor for steam thermal reaction, wherein the hydrothermal temperature was 110 ° C and the hydrothermal time was 10 h.

[0051] (2) The silicon wafer after the steam thermal reaction was washed with anhydrous ethanol for multiple times and dried in a vacuum drying oven at 60°C for 4 h to obtain the BiOCl / SiNWs material, which was recorded as BiOCl / SiNWs-70.

[0052] Example 5

[0053] A method for preparing a BiOCl / SiNWs photoanode material for photoelectrocatalytic degradation of antibiotics comprises the following steps:

[0054] (1) 80 mg of BiCl 3 After being added to a beaker containing 8 ml of ethylene glycol solution, the mixture was ultrasonicated for 30 min, and the SiNWs prepared in Example 1 were placed in the beaker. Subsequently, the bracket and 40 ml of isopropanol solution were placed in a polytetrafluoroethylene reactor. Finally, the beaker was placed on the bracket of the reactor for steam thermal reaction, wherein the hydrothermal temperature was 110 ° C and the hydrothermal time was 10 h.

[0055] (2) After the steam thermal reaction, the silicon wafer is washed with anhydrous ethanol for multiple times and dried in a vacuum drying oven at 60°C for 4 h to obtain the BiOCl / SiNWs material, which is denoted as BiOCl / SiNWs-80.

[0056] Application Examples

[0057] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0058] In the CHI660D electrochemical workstation, 100 mL of 2.1×10 -5 mol / L tetracycline hydrochloride simulated water source was added as electrolyte to a three-electrode electrolytic cell for photoelectrocatalytic experiments. The silicon nanowire array prepared in Example 1 and the BiOCl / SiNWs materials prepared in Examples 2-5 were used as photoelectrocatalysts, i.e., working electrodes, Pt as counter electrodes, Ag / AgCl as reference electrodes, and a xenon lamp light source with a power of 300W and a cutoff wavelength of 420nm filter was used to simulate natural visible light. The applied bias voltage was 1.5V. In addition, all potentials in the experiment were converted to reversible hydrogen electrodes (RHE).

[0059] As BiCl 3 As the amount of BiOCl nanoparticles increases, the amount of BiOCl nanoparticles attached to the SiNWs surface also increases. When the amount of BiOCl nanoparticles attached is greater than the critical point, too many BiOCl nanoparticles will agglomerate on the SiNWs surface, covering the active sites of BiOCl / SiNWs, resulting in a decrease in performance. Figure 3 , 4 As shown, BiCl 3 When the addition amount increased from 50 mg to 60 mg, the current density and degradation of the BiOCl / SiNWs sample first increased and then decreased.

[0060] like Figure 5 As shown in the figure, when BiOCl / SiNWs is exposed to simulated sunlight, the e - can be excited into e in CB-BiOCl and VB-SiNWs - can also be transferred to CB-SiNWs. Under the action of potential difference and built-in electric field, the e accumulated on CB-BiOCl - will be transferred to VB-SiNWs and recombine with the photogenerated holes at the BiOCl / SiNWs interface. - Migrate to the counter electrode, promoting h + and e - The remaining h in VB-BiOCl can be separated, thereby improving the photoelectrocatalytic performance of BiOCl / SiNWs photoanode. + Oxidation of H 2 O and OH - ·OH is formed, while the remaining e in CB-SiNWs - Will attack O 2 To reduce to O 2 -, these active substances (such as ·OH, ·O 2 - 、e - and h + ) can degrade TC into CO 2 and H 2 O.

[0061] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A composite BiOCl / SiNWs material, characterized in that: BiOCl nanoparticles are loaded on the surface of SiNWs to form the composite BiOCl / SiNWs material.

2. A method for preparing the composite BiOCl / SiNWs material according to claim 1, characterized in that: The following steps are involved: BiOCl nanoparticles were synthesized by a steam thermal method and then loaded onto a silicon nanowire substrate by a deposition method to form a composite BiOCl / SiNWs material.

3. The method for preparing a composite BiOCl / SiNWs material according to claim 2, characterized in that: The specific steps include: (1) placing BiCl3 in an ethylene glycol solution and performing ultrasonication to obtain a BiCl3 ethylene glycol mixed solution; (2) Pour the isopropanol solution into the container of the reactor and put the bracket into it; (3) placing SiNWs in a container containing a BiCl3 ethylene glycol mixed solution, and placing the container on a support for a steam thermal reaction, wherein the temperature of the steam thermal reaction is 110 to 120° C. and the reaction time is 10 to 12 hours; (4) Cleaning and drying the silicon wafer after the steam thermal reaction to obtain the composite BiOCl / SiNWs material.

4. The method for preparing a composite BiOCl / SiNWs material according to claim 3, characterized in that: The mass ratio of BiCl3, ethylene glycol and isopropanol is (50-80):(9-13):(31-47).

5. The method for preparing a composite BiOCl / SiNWs material according to claim 3, characterized in that: In step (3), the preparation method of SiNWs is as follows: the silicon wafer is pretreated and then immersed in a Piranha mixed solution, and then sequentially placed in a silver deposition solution, an acid etching solution, and a silver removal solution for silver deposition, acid etching, and silver removal operations, and a silicon nanowire array is prepared by a metal-assisted chemical etching method.

6. The method for preparing a composite BiOCl / SiNWs material according to claim 5, characterized in that: The Piranha mixed solution is a mixed solution of H2SO4 and H2O2 in a volume ratio of 3:1 to 3:2; The silver deposition solution is a mixed solution of 0.01-0.05 mol / L AgNO3 aqueous solution and 4.6-5 mol / L HF aqueous solution; The acidic etching solution is a mixed solution of 0.3-0.5 mol / L H2O2 aqueous solution and 4.6-5 mol / L HF aqueous solution; The desilvering solution is a mixed solution of nitric acid and deionized water in a volume ratio of 1:1 to 1:

2.

7. The method for preparing a composite BiOCl / SiNWs material according to claim 5, characterized in that: The length and width of the silicon wafer are both 9 to 11 mm, the thickness is 450 to 550 μm, the resistivity is 0.02 to 0.05 Ω / cm, and the crystal orientation is (100); The silicon wafer pretreatment method is as follows: a single-side polished n-type silicon wafer is sequentially placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning; The pretreated silicon wafer is immersed in the Piranha mixed solution at a temperature of 70 to 80° C. for 20 to 30 minutes; the silicon wafer is then ultrasonically cleaned with deionized water for 10 to 15 times, each time for 3 to 5 minutes, and then the silicon wafer is immersed in hydrofluoric acid with a concentration of 1 to 5 minutes to remove the surface oxide layer; The silicon wafer is placed in a silver deposition solution, kept at 25-35° C., and silver particles are deposited for 1-10 minutes; After the silver particles are deposited, the silicon wafer is placed in an acidic etching solution at a temperature of 25 to 35°C for etching for 10 to 30 minutes. The acid-etched silicon wafer is immersed in the desilvering solution at a temperature of 25 to 35°C for 1 to 2 hours.

8. A photoanode material, characterized in that: The photoanode material is the composite BiOCl / SiNWs material according to claim 1.

9. A method for photoelectrocatalytic degradation of antibiotics, characterized in that: The following steps are involved: (1) A square electrolytic cell is used as a reaction cell, the composite BiOCl / SiNWs material according to claim 1 is used as a photoanode, a platinum sheet electrode is used as a photocathode, and an aqueous solution containing antibiotics is used as an electrolyte; (2) Using a xenon lamp light source to irradiate the photoanode and photocathode described in step (1), applying a bias voltage of 0.5 to 1.5 V to form a photoelectrochemical catalytic reaction, thereby degrading the antibiotics.

10. The method for photoelectrocatalytic degradation of antibiotics according to claim 9, characterized in that: The xenon lamp light source is equipped with a filter with a cut-off wavelength of 420nm and a power of 300-400W.

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