A composite ZnFe2O4 / SiNWs material and its preparation method and use

Abstract

The present invention discloses a composite ZnFe2O4 / SiNWs material, its preparation method, and use. The preparation method uses a metal-assisted chemical etching method to prepare a silicon nanowire array substrate. The array structure can enhance the scattering probability of incident light and improve the silicon substrate's absorption efficiency of visible light. Subsequently, zinc ferrite (ZnFe2O4) nanoparticles are synthesized by a hydrothermal method. The ZnFe2O4 nanoparticles are then loaded onto the silicon nanowire substrate by spin coating and calcination to form a novel composite ZnFe2O4 / SiNWs photoanode material. In the present invention, the ZnFe2O4 and the silicon nanowire array substrate can form a heterojunction structure, accelerating the separation and migration rate of photogenerated carriers and reducing the recombination probability of photogenerated carriers, thereby effectively improving the photoelectric performance of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a composite ZnFe2O4 / SiNWs material and a preparation method and application thereof. Background Art

[0002] With the rapid growth of the antibiotic market, the misuse and improper handling of antibiotics have led to widespread, high-concentration, and diverse antibiotic pollution in water bodies. Furthermore, antibiotic wastewater is characterized by high chroma and large pH fluctuations. Excessive antibiotic concentrations in water bodies not only increase bacterial resistance but also create superbugs, posing a serious threat to human health. Therefore, to address the increasingly difficult problem of water pollution, the search for green, efficient, and environmentally friendly antibiotic treatment technologies is essential and urgent. Currently, photoelectrocatalytic degradation has attracted research attention due to its simple degradation process, environmental friendliness, and excellent degradation performance.

[0003] Silicon (Si) has the advantages of abundant reserves, low price, stable physical and chemical properties and non-toxicity. In addition, silicon's unique narrow band gap (1.12eV) can absorb sunlight from ultraviolet (UV) to near-infrared (NIR), making it a potential photoanode. However, the valence band position of silicon is low. On the one hand, its valence band hole oxidation ability is weak, and it is easily oxidized to SiO2 in water. Silicon is also prone to photocorrosion, which leads to electrolyte instability, excessive overpotential and poor stability. 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 application in photoelectrocatalytic degradation of pollutants. 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 object of the present invention is to provide a composite ZnFe2O4 / SiNWs material and its preparation method and use, which can solve the technical problems raised by the above background technology.

[0005] In one aspect, the present invention provides a method for preparing a composite ZnFe2O4 / SiNWs material. According to an embodiment of the present invention, ZnFe2O4 nanoparticles are loaded on the surface of SiNWs to form the ZnFe2O4 / SiNWs material.

[0006] In addition, the method for preparing a composite ZnFe2O4 / SiNWs material according to the above embodiment of the present invention may also have the following additional technical features:

[0007] In some embodiments of the present invention, the method includes the following steps: preparing ZnFe2O4 nanoparticles by a hydrothermal method, dissolving ZnFe2O4 in anhydrous ethanol to prepare a ZnFe2O4 ethanol solution, and then loading the ZnFe2O4 ethanol solution on the SiNWs surface by spin coating and calcination in sequence to obtain the ZnFe2O4 / SiNWs photoanode material.

[0008] In some embodiments of the present invention, a precursor reagent of ZnFe2O4 nanoparticles is prepared, which includes 9.5 to 10.5 mmol of Fe(NO3)3·9H2O, 5 to 6 mmol of Zn(NO3)2·6H2O and 50 to 60 mL of deionized water, and the pH of the mixture is adjusted to 12 with 1 mol / L NaOH solution; the hydrothermal reaction temperature is 160 to 200°C, and the hydrothermal reaction time is 12 to 18 h; the concentration of the ZnFe2O4 ethanol solution is 0.25 to 1 mg / mL; the rotation rate during spin coating is 500 to 1000 rpm, the rotation time is 30 to 60 s, and the spin coating volume of 1*1 cm SiNWs is 100 to 150 μL; the calcination temperature is 200 to 300°C, the holding time is 2 to 3 h, and the calcination is carried out under a nitrogen atmosphere.

[0009] In some embodiments of the present invention, the preparation method of the SiNWs is as follows: after pre-treatment, the silicon wafer is immersed in a Piranha mixed solution, and then sequentially placed in a silver deposition solution, an acidic 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.

[0010] In some embodiments of the present invention, 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 to 0.05 mol / L AgNO3 aqueous solution and 4.6 to 5 mol / L HF aqueous solution; the acidic etching solution is a mixed solution of 0.3 to 0.5 mol / L H2O2 aqueous solution and 4.6 to 5 mol / L HF aqueous solution; the silver removal solution is a mixed solution of nitric acid and deionized water in a volume ratio of 1:1 to 1:2.

[0011] 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: the 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 minutes; after pretreatment, After the silicon wafer is soaked in the Piranha mixed solution, it is ultrasonically cleaned with deionized water for 10 to 15 times, each time for 3 to 5 minutes, and then the silicon wafer is soaked in hydrofluoric acid with a concentration of 5wt% to remove the surface oxide layer; the silicon wafer is kept in a silver deposition solution at 25 to 35°C for 1 to 10 minutes to deposit silver particles; the silicon wafer after the silver particles are deposited is etched in an acidic etching solution at 25 to 35°C for 10 to 30 minutes; and the acid-etched silicon wafer is soaked in a silver removal solution at 25 to 35°C for 1 to 2 hours.

[0012] In another aspect of the present invention, the present invention provides a composite ZnFe2O4 / SiNWs material prepared according to the preparation method of the composite ZnFe2O4 / SiNWs material.

[0013] In another aspect of the present invention, a photoanode material is provided. According to an embodiment of the present invention, the photoanode material is the composite ZnFe2O4 / SiNWs material.

[0014] In another aspect of the present invention, a method for photoelectrocatalytic degradation of antibiotics is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0015] (1) A square electrolytic cell is used as a reaction cell, the photoanode material is used as a photoanode, a platinum electrode is used as a photocathode, and an aqueous solution containing antibiotics is used as an electrolyte;

[0016] (2) Using a xenon lamp light source to irradiate the photoanode and photocathode described in step (1), applying a 1.5V bias voltage to form a photoelectrochemical catalytic reaction, thereby degrading the antibiotics.

[0017] 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:

[0018] In some embodiments of the present invention, the xenon lamp light source is equipped with a filter with a cut-off wavelength of 420 nm and has a power of 300-400 W.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (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.

[0021] (2) ZnFe2O4 nanoparticles (with an average grain size of 15 to 30 nm) were prepared by a hydrothermal method. ZnFe2O4 nanoparticles can enter the silicon nanowire array structure. Due to the synergistic effect of Fe-Zn, ion leaching is reduced while the binding force between ZnFe2O4 and SiNWs is enhanced, thereby improving the stability of the silicon nanowire array substrate. In addition, ZnFe2O4 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 ZnFe2O4 can form a built-in electric field. Under the interaction of interface electrons, e - Migration from CB-ZnFe2O4 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 enhance the photoelectrochemical activity of the silicon nanowire substrate.

[0022] (3) The ZnFe2O4 / SiNWs photoanode material of the present invention is used as a photoanode, which can generate OH under the action of light. - 、O2 - It can degrade antibiotics by removing free radicals, breaking down large-molecule antibiotic pollutants into small-molecule pollutants, water and carbon dioxide, which is environmentally friendly.

[0023] (4) The photoanode generates photogenerated electron-hole pairs (e - / h + ), the applied bias can delay e - / h + Compound. e - and h + They can react to generate active free radicals with strong oxidizing effect such as hydroxyl radical (·OH), hole (h + ) and superoxide radicals (·O2 - ), and then degrade antibiotic pollutants into small molecules such as CO2 and H2O. 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. - They are quickly removed from the conduction band, which greatly suppresses the photogenerated electrons in the photoanode. -With h + The compound, extended h + The photoelectric synergistic effect improves the efficiency of photoelectrocatalytic degradation of antibiotics in ZnFe2O4 / SiNWs samples.

[0024] (5) Regarding the preparation method of ZnFe2O4 / SiNWs photoanode material, this process is simple, easy to operate, highly efficient, and low-cost; and the ZnFe2O4 / 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

[0025] Figure 1 This is a flow chart for preparing ZnFe2O4 / SiNWs photoanode materials in an embodiment of the present invention;

[0026] Figure 2 TEM image of the ZnFe2O4 / SiNWs photoanode material in Example 3 of the present invention;

[0027] Figure 3 The linear sweep voltammetry curves of the photoelectrocatalysts (i.e., photoanode materials) in Examples 1-5 of the present invention are shown;

[0028] Figure 4 Graph showing the degradation rates of the photoelectrocatalysts (i.e., photoanode materials) in Examples 1-5 of the present invention;

[0029] Figure 5 This is a mechanism analysis diagram of the photoelectrocatalytic degradation of antibiotic wastewater by ZnFe2O4 / SiNWs photoanode material in the application example of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing SiNWs photoanode material, using a two-step metal-assisted chemical etching method to prepare a silicon nanowire array, comprising the following steps:

[0033] (1) First, pre-treat the n-type silicon wafer. The wafer has a length and width of 10 mm, a thickness of 500 μm, a resistivity of 0.02-0.05 Ω / cm, and a crystal orientation of (100). The wafer is then ultrasonically treated in acetone, anhydrous ethanol, and deionized water for 20 minutes to remove organic matter. After drying, the wafer is placed in a Piranha mixed solution (H2SO4 and H2O2 in a volume ratio of 3:1) and hydrothermally heated at 80°C for 20 minutes to remove the oxide layer. The wafer is then ultrasonically cleaned in deionized water 10 times (3 minutes each time). The wafer is then immersed in 5 wt% hydrofluoric acid to remove the surface oxide layer.

[0034] (2) Place the silicon wafer in a silver plating solution (4.8 mol / L HF and 0.02 mol / L AgNO3) at 25°C for 1 minute. Rinse the excess Ag with deionized water and quickly place it in an etching solution (4.8 mol / L HF and 0.3 mol / L H2O2) for 10 minutes at 25°C. Rinse it with deionized water. Then, place it in a desilvering solution (nitric acid and deionized water in a volume ratio of 1:1) at 25°C for 2 hours. After that, vacuum dry or blow dry with N2 to prepare a silicon nanowire array for use.

[0035] Application Example 1

[0036] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0037] In the CHI660D electrochemical workstation, 100 mL of a 2.1×10 -5 Photoelectrocatalytic experiments were conducted in a three-electrode electrolytic cell using a simulated water source containing 1 mol / L tetracycline hydrochloride as the electrolyte. The silicon nanowire array prepared in Example 1 served as the photoelectrocatalyst, i.e., the working electrode. Pt served as the counter electrode, and Ag / AgCl served as the reference electrode. A 300W xenon lamp equipped with a 420nm cutoff filter was used to simulate natural visible light. A bias voltage of 1.5V was applied. All potentials in the experiments were converted to the reversible hydrogen electrode (RHE).

[0038] Example 2

[0039] A method for preparing a composite ZnFe2O4 / SiNWs material comprises the following steps:

[0040] (1) After 10 mmol of Fe(NO3)3·9H2O, 5 mmol of Zn(NO3)2·6H2O, and 50 mL of deionized water were mixed evenly, the pH of the solution was adjusted to 12 with 1 mol / L NaOH solution, and then the solution was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction at 180°C for 14 h to obtain a suspension containing ZnFe2O4 nanoparticles.

[0041] (2) The suspension was washed three times with deionized water and anhydrous ethanol, and then centrifuged and dried in a vacuum drying oven at 60°C for 12 h before use;

[0042] (3) 1 mg of dried ZnFe2O4 powder was dissolved in 4 mL of ethanol to prepare a 0.25 mg / mL ZnFe2O4 ethanol solution, and 100 μL of the ZnFe2O4 ethanol solution was evenly spin-coated on the surface of the silicon nanowire array prepared in Example 1. The silicon wafer was then placed in a tube furnace and calcined for 2 h at a calcination temperature of 200°C to obtain a ZnFe2O4 / SiNWs material, i.e., a ZnFe2O4 / SiNWs photoelectrocatalyst.

[0043] Application Example 2

[0044] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0045] In the CHI660D electrochemical workstation, 100 mL of a 2.1×10 -5 Photoelectrocatalytic experiments were conducted in a three-electrode electrolytic cell using a simulated water source of 1 mol / L tetracycline hydrochloride. The ZnFe2O4 / SiNWs photoanode material prepared in Example 2 was used as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. A 300W xenon lamp equipped with a 420nm cutoff filter was used to simulate natural visible light. A bias voltage of 1.5V was applied. All potentials in the experiments were converted to the reversible hydrogen electrode (RHE).

[0046] Example 3

[0047] A method for preparing a composite ZnFe2O4 / SiNWs material comprises the following steps:

[0048] (1) After 10 mmol of Fe(NO3)3·9H2O, 5 mmol of Zn(NO3)2·6H2O, and 50 mL of deionized water were mixed evenly, the pH of the solution was adjusted to 12 with 1 mol / L NaOH solution, and then the solution was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction at 180°C for 14 h to obtain a suspension containing ZnFe2O4 nanoparticles.

[0049] (2) The suspension was washed three times with deionized water and anhydrous ethanol, and then centrifuged and dried in a vacuum drying oven at 60°C for 12 h before use;

[0050] (3) 2 mg of dried ZnFe2O4 powder was dissolved in 4 mL of ethanol to prepare a 0.5 mg / mL ZnFe2O4 ethanol solution, and 100 μL of the ZnFe2O4 ethanol solution was evenly spin-coated on the surface of the silicon nanowire array prepared in Example 1. The silicon wafer was then placed in a tube furnace and calcined for 2 h at a calcination temperature of 200°C to obtain a ZnFe2O4 / SiNWs material, which is a photoelectric catalyst.

[0051] from Figure 2 TEM images show that the size of individual SiNWs is around 100 nm. Fine ZnFe2O4 nanoparticles are evenly attached to the surface of the SiNWs, and a small amount of nanoparticles agglomerate at the top of the nanowires, increasing the size of the SiNWs. Therefore, the ZnFe2O4 / SiNWs material was successfully prepared using the spin coating method.

[0052] Application Example 3

[0053] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0054] In the CHI660D electrochemical workstation, 100 mL of a 2.1×10 -5 Photoelectrocatalytic experiments were conducted in a three-electrode electrolytic cell using a simulated water source of 1 mol / L tetracycline hydrochloride. The ZnFe2O4 / SiNWs prepared in Example 3 were used as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. A 300W xenon lamp equipped with a 420nm cutoff filter was used to simulate natural visible light. A bias voltage of 1.5V was applied. All potentials in the experiments were converted to the reversible hydrogen electrode (RHE).

[0055] Example 4

[0056] A method for preparing a ZnFe2O4 / SiNWs photoanode material for photoelectrocatalytic degradation of antibiotics comprises the following steps:

[0057] (1) After 10 mmol of Fe(NO3)3·9H2O, 5 mmol of Zn(NO3)2·6H2O, and 50 mL of deionized water were mixed evenly, the pH of the solution was adjusted to 12 with 1 mol / L NaOH solution, and then the solution was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction at 180°C for 14 h to obtain a suspension containing ZnFe2O4 nanoparticles.

[0058] (2) The suspension was washed three times with deionized water and anhydrous ethanol, and then centrifuged and dried in a vacuum drying oven at 60°C for 12 h before use;

[0059] (3) 3 mg of dried ZnFe2O4 powder was dissolved in 4 mL of ethanol to prepare a 0.75 mg / mL ZnFe2O4 ethanol solution, and 100 μL of the ZnFe2O4 ethanol solution was evenly spin-coated on the surface of the silicon nanowire array prepared in Example 1. The silicon wafer was then placed in a tube furnace and calcined for 2 h at a temperature of 200°C to obtain a ZnFe2O4 / SiNWs material, which is a photoelectrocatalyst.

[0060] Application Example 4

[0061] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0062] In the CHI660D electrochemical workstation, 100 mL of a 2.1×10 -5 Photoelectrocatalytic experiments were conducted in a three-electrode electrolytic cell using a simulated water source of 1 mol / L tetracycline hydrochloride. The ZnFe2O4 / SiNWs photoelectrocatalyst prepared in Example 4 was used as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. A 300W xenon lamp equipped with a 420nm cutoff filter was used to simulate natural visible light. A bias voltage of 1.5V was applied. All potentials in the experiments were converted to the reversible hydrogen electrode (RHE).

[0063] Example 5

[0064] A method for preparing a ZnFe2O4 / SiNWs photoanode material for photoelectrocatalytic degradation of antibiotics comprises the following steps:

[0065] (1) After 10 mmol of Fe(NO3)3·9H2O, 5 mmol of Zn(NO3)2·6H2O, and 50 mL of deionized water were mixed evenly, the pH of the solution was adjusted to 12 with 1 mol / L NaOH solution, and then the solution was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction at 180°C for 14 h to obtain a suspension containing ZnFe2O4 nanoparticles.

[0066] (2) The suspension was washed three times with deionized water and anhydrous ethanol, and then centrifuged and dried in a vacuum drying oven at 60°C for 12 h before use;

[0067] (3) 4 mg of dried ZnFe2O4 powder was dissolved in 4 mL of ethanol to prepare a 1 mg / mL ZnFe2O4 ethanol solution, and 100 μL of the ZnFe2O4 ethanol solution was evenly spin-coated on the surface of the silicon nanowire array prepared in Example 1. The silicon wafer was then placed in a tube furnace and calcined for 2 h at a calcination temperature of 200°C to obtain a ZnFe2O4 / SiNWs material, which is a photoelectric catalyst.

[0068] Application Example 5

[0069] A method for photoelectrocatalytic degradation of antibiotics, comprising the following steps:

[0070] In the CHI660D electrochemical workstation, 100 mL of a 2.1×10 -5 Photoelectrocatalytic experiments were conducted in a three-electrode electrolytic cell using a simulated water source of 1 mol / L tetracycline hydrochloride. The ZnFe2O4 / SiNWs photoelectrocatalyst prepared in Example 5 was used as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. A 300W xenon lamp equipped with a 420nm cutoff filter was used to simulate natural visible light. A bias voltage of 1.5V was applied. All potentials in the experiments were converted to the reversible hydrogen electrode (RHE).

[0071] As the spin coating concentration increases, the amount of ZnFe2O4 nanoparticles attached to the SiNWs surface also increases. When the amount of attachment exceeds the critical point, too many ZnFe2O4 nanoparticles will agglomerate on the SiNWs surface, covering the active sites of ZnFe2O4 / SiNWs, resulting in performance degradation. Therefore, Figure 3 、 4 As shown, when the spin coating concentration increases from 0.25 mg / mL to 1 mg / mL, the current density and degradation of the ZnFe2O4 / SiNWs sample first increase and then decrease.

[0072] like Figure 5 As shown in the figure, when ZnFe2O4 / SiNWs is exposed to simulated sunlight, the e - can be excited to the e in CB-ZnFe2O4 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-ZnFe2O4 - will be transferred to VB-SiNWs and recombine with the photogenerated holes at the ZnFe2O4 / SiNWs interface. - Migrate to the counter electrode, promoting h + and e - The separation of h in VB-ZnFe2O4 can improve the photoelectrocatalytic performance of ZnFe2O4 / SiNWs photoanode. + Will oxidize H2O and OH - ·OH is formed, while the remaining e in CB-SiNWs - Will attack O2 to convert it back into O2 - , these active substances (such as ·OH, ·O2 - 、e- and h + ) can degrade TC into CO2 and H2O.

[0073] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments 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 should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a composite ZnFe2O4 / SiNWs material, characterized by: The method comprises the following steps: preparing ZnFe2O4 nanoparticles by a hydrothermal method, dissolving ZnFe2O4 in anhydrous ethanol to prepare a ZnFe2O4 ethanol solution, and then loading the ZnFe2O4 ethanol solution on the surface of SiNWs by spin coating and calcining in sequence to obtain the ZnFe2O4 / SiNWs photoanode material; Among them, the precursor reagent for preparing ZnFe2O4 nanoparticles is a mixture of 9.5-10.5mmol Fe(NO3)3·9H2O, 5-6mmol Zn(NO3)2·6H2O and 50-60mL deionized water, and the pH of the mixture is adjusted to 12 with 1mol / L NaOH solution; The hydrothermal reaction temperature is 160-200°C, and the hydrothermal reaction time is 12-18 hours; The concentration of ZnFe2O4 ethanol solution is 0.25-1 mg / mL; During the spin coating process, the rotation rate was 500-1000 rpm, the spin time was 30-60 s, and the spin coating volume of 1*1 cm SiNWs was 100-150 μL; The calcination temperature is 200-300° C., the holding time is 2-3 hours, and the calcination is carried out under a nitrogen atmosphere.

2. The method for preparing a composite ZnFe2O4 / SiNWs material according to claim 1, characterized in that: The SiNWs preparation method is as follows: a silicon wafer is pretreated and immersed in a Piranha mixed solution, and then sequentially placed in a silver deposition solution, an acidic etching solution, and a silver removal solution for silver deposition, acid etching, and silver removal operations, and a metal-assisted chemical etching method is used to prepare a silicon nanowire array.

3. The method for preparing a composite ZnFe2O4 / SiNWs material according to claim 2, characterized in that: The Piranha mixed solution is a mixed solution of H2SO4 and H2O2 with 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 silver removal solution is a mixed solution of nitric acid and deionized water in a volume ratio of 1:1 to 1:

2.

4. The method for preparing a composite ZnFe2O4 / SiNWs material according to claim 2, characterized in that: The silicon wafer has a length and width of 9 to 11 mm, a thickness of 450 to 550 μm, a resistivity of 0.02 to 0.05 Ω / cm, and a crystal orientation of (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. After the pre-treated silicon wafer is soaked in the Piranha mixed solution, the silicon wafer is ultrasonically cleaned with deionized water 10 to 15 times, each time for 3 to 5 minutes, and then the silicon wafer is immersed in 5wt% hydrofluoric acid to remove the surface oxide layer; The silicon wafer is placed in a silver deposition solution and kept at 25 to 35° C. to deposit silver particles for 1 to 10 minutes; After the silver particles are deposited, the silicon wafer is etched in an acidic etching solution at a temperature of 25 to 35°C for 10 to 30 minutes. After acid etching, the silicon wafer is soaked in the silver removal solution at a temperature of 25-35°C for 1-2 hours.

5. A composite ZnFe2O4 / SiNWs material prepared according to the preparation method of the composite ZnFe2O4 / SiNWs material according to any one of claims 1 to 4.

6. A photoanode material, characterized in that: The photoanode material is the composite ZnFe2O4 / SiNWs material according to claim 5.

7. 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 photoanode material according to claim 5 is used as a photoanode, a platinum 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 1.5V bias voltage to form a photoelectrochemical catalytic reaction, thereby degrading the antibiotics.

8. The method for photoelectrocatalytic degradation of antibiotics according to claim 7, 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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