A Ag3PO4 / Si pyramid array photoelectric catalyst and its preparation method and application

Abstract

The present invention discloses a Ag3PO4 / Si pyramid array photoelectric catalyst and its preparation method and application. The Ag3PO4 nanoparticles and silicon pyramid arrays are composed of Ag3PO4 nanoparticles. The preparation method is to prepare the silicon pyramid array by metal-assisted wet alkaline etching, and to make the Ag3PO4 nanoparticles grow in situ on the silicon pyramid array to form a composite material by an impregnation method. The silicon pyramid array structure in the present invention enhances the scattering probability of the incident light and can improve the light utilization rate; the loaded Ag3PO4 nanoparticles and the silicon pyramid array form a heterojunction to accelerate the separation of photogenerated carriers; the positive valence band position of Ag3PO4 is utilized to enhance the oxidation degradation ability of the silicon pyramid array; the Ag3PO4 / Si pyramid array photoelectric catalyst of the present invention is a block solid catalyst, which is easier to recycle than the traditional powder catalyst.

Description

Technical Field

[0001] The present invention relates to the field of preparation of nanomaterials and photoelectrocatalysis technology, and in particular to an Ag 3 PO 4 / Si pyramid array photoelectric catalyst and its preparation method and application. Background Art

[0002] With the rapid development of industry and agriculture and the acceleration of urbanization, water pollution, especially water shortage caused by organic pollutants, has become a major problem threatening the sustainable development of human society. Compared with traditional physical water treatment methods such as precipitation, adsorption, and filtration, which are complex and cannot completely treat pollutants, photoelectrocatalytic oxidation technology has attracted widespread attention due to its environmental friendliness and simple process.

[0003] Silicon-based materials have potential application prospects in the field of photoelectrocatalytic water treatment because of their narrow band gap and ability to absorb a wider range of solar spectrum. However, the large difference in the mobility of silicon holes and electrons leads to easy recombination of photogenerated charges and low charge separation efficiency; the oxidation capacity of valence band holes is insufficient to oxidize and degrade most organic pollutants. Silver phosphate has a relatively positive valence band position and strong oxidation capacity, but it is prone to photocorrosion and is difficult to maintain photocatalytic activity. In photocatalytic applications, it is difficult to recycle.

[0004] In response to the above problems, constructing heterostructures to improve the efficiency of photogenerated charge separation and preparing nano-sized materials to improve the valence band hole oxidation ability are still urgent issues to be solved in the field of silicon material photoelectrocatalysis. Summary of the invention

[0005] The object of the present invention is to provide a Ag 3 PO 4 / Si pyramid array photoelectric catalyst and its preparation method and application, which uses Ag 3 PO 4 It forms a heterojunction with silicon, which improves the photoelectric catalytic degradation performance of the silicon pyramid array.

[0006] In one aspect of the present invention, the present invention provides an Ag 3 PO 4 / Si pyramid array photoelectric catalyst. According to an embodiment of the present invention, the Ag 3 PO 4 / Si pyramid array photocatalyst composed of Ag 3 PO 4 Nanoparticle silicon pyramid array, Ag 3 PO 4 Nanoparticles are loaded on the surface of silicon pyramid arrays.

[0007] In another aspect of the present invention, the present invention provides an Ag 3 PO 4 / Preparation method of Si pyramid array photoelectric catalyst. According to an embodiment of the present invention, a metal-assisted wet alkaline etching method is used to prepare a silicon pyramid array, and Ag is loaded on the surface of the silicon pyramid array by an immersion method. 3 PO 4 Nanoparticles.

[0008] In addition, according to the above embodiment of the present invention, an Ag 3 PO 4 The method for preparing the Si pyramid array photoelectric catalyst may also have the following additional technical features:

[0009] In some embodiments of the present invention, the method specifically comprises the following steps:

[0010] (1) Pre-treating a silicon wafer, and preparing a silicon pyramid array by a metal-assisted wet alkaline etching method for standby use;

[0011] (2) Preparation of Ag by impregnation method 3 PO 4 / Si pyramid array composite material: an appropriate amount of AgNO 3 Dissolve in ethanol, labeled solution A, and add an appropriate amount of Na 2 HPO 4 Dissolve in deionized water, marked as solution B, immerse the silicon pyramid array in solution A for a period of time, then take out the silicon pyramid array and immerse it in solution B for a period of time, repeat this process several times to obtain the above-mentioned Ag 3 PO 4 / Si pyramid array photocatalyst.

[0012] In some embodiments of the present invention, in step (1), the method for pretreating the silicon wafer is as follows: the single-side polished silicon wafer is ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water, and then the silicon wafer is heated in a water bath in a mixed solution of concentrated sulfuric acid and hydrogen peroxide, and finally the silicon wafer is ultrasonically cleaned in deionized water.

[0013] In some embodiments of the present invention, the ultrasonic cleaning time of the single-sided polished silicon wafer is 20 minutes, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3:1, the water bath heating temperature is 75-85°C, the time is 15-30 minutes, and the silicon wafer after water bath heating is ultrasonically cleaned in deionized water for 8-10 times, each time for 3 minutes.

[0014] In some embodiments of the present invention, in step (1), the metal-assisted wet alkaline etching method comprises the following steps: 3, HF and deionized water are stirred evenly to prepare a silver deposition solution, a certain amount of KOH, isopropanol and deionized water are taken and fully mixed to prepare an etching solution; the silicon wafer is immersed in the silver deposition solution for 5-10 seconds, and then put into the etching solution for etching, and then the surface of the etched silicon wafer is rinsed with deionized water; a mixed solution of deionized water and nitric acid is prepared, stirred evenly, and then the etched silicon wafer is immersed in it for 5-10 minutes to remove the silver generated on the surface of the silicon array; the immersed silicon wafer is taken out and repeatedly rinsed with deionized water, and then the silicon wafer is etched in N 2 The silicon pyramid array was obtained by drying under atmospheric pressure.

[0015] In some embodiments of the present invention, in the silver deposition solution, AgNO 3 The concentration is 0.004-0.006 mol / L, and the volume percentage of HF is 5%-10%; in the etching solution, the mass percentage of KOH is 1.5%-3.5%, and the volume percentage of isopropanol is 5%-20%; in the mixed solution, the volume ratio of nitric acid to deionized water is 1:1; the etching time is 30-60 min, and the etching temperature is 70-80°C; the drying time is 30-60 min, and the drying temperature is 30-50°C.

[0016] In some embodiments of the present invention, in step (2), AgNO 3 The concentration of the solution is 0.006-0.012 mol / L, Na 2 HPO 4 The concentration of the solution is 0.002-0.004 mol / L, the immersion time in solution A is 30-60 minutes, the immersion time in solution A and solution B is 1-3 minutes respectively, and the immersion is repeated 10-40 times.

[0017] In another aspect of the present invention, a method for photoelectrocatalytic degradation of antibiotics is provided. 3 PO 4 / Si pyramid array photoelectric catalyst as a photoanode. Specifically, the following steps are included: 3 PO 4 / Si pyramid array photocatalyst was used as photoanode, platinum electrode was used as photocathode, a DC regulated power supply was used to apply a positive bias voltage of 0.5-1.5V to the photoanode, and the light intensity was 100mW / cm 2 A xenon lamp was used as the light source to degrade a 10 mg / L tetracycline hydrochloride aqueous solution.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) Ag 3 PO4 / Si pyramid array photoelectric catalyst Compared with planar silicon as the substrate of photoelectric catalyst, the surface of silicon pyramid array has light trapping effect, which enhances the scattering probability of incident light and can enhance light absorption efficiency.

[0020] 2) The present invention in situ grows Ag on the surface of the silicon pyramid array by a simple immersion method 3 PO 4 Nanoparticles, construct binary heterojunction, use Ag 3 PO 4 The more positive valence band position can enhance the oxidation degradation ability of silicon pyramid arrays.

[0021] 3) Ag 3 PO 4 Nanoparticles can be used as active sites to increase the exposure of active sites. Secondly, the binary heterojunction structure is used as a photoanode, which can effectively improve the light absorption efficiency and reduce the recombination probability of photogenerated electron-hole pairs during the photoelectrocatalytic process, which is conducive to the transfer of charge carriers and improves the antibiotic degradation performance.

[0022] 4) Compared with traditional powdered nanoparticle catalysts, the photoelectrocatalyst of the present invention is not only easy to recycle, but also avoids secondary pollution of water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 In the embodiment of the present invention, Ag 3 PO 4 / Schematic diagram of the preparation method of Si pyramid array photoelectrocatalyst;

[0024] Figure 2 The SEM cross-sectional images of the silicon pyramid array before and after impregnation in Example 1 of the present invention;

[0025] Figure 3 The ultraviolet-visible absorption spectra of the planar silicon before etching and the silicon pyramid array after etching in Example 1 of the present invention;

[0026] Figure 4 Ag prepared in Examples 1-4 of the present invention 3 PO 4 / Si pyramid array and linear scan voltammetric characteristic curve of Si pyramid array;

[0027] Figure 5 Ag prepared in Examples 1-4 of the present invention 3 PO 4 / Si pyramid array photocatalyst and tetracycline hydrochloride degradation performance diagram of Si pyramid array. DETAILED DESCRIPTION

[0028] 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.

[0029] Example 1

[0030] A kind of Ag 3 PO 4 / Preparation method of Si pyramid array photoelectric catalyst, such as Figure 1 As shown, the following steps are included:

[0031] (1) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 min in sequence, and then placed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 20 min to completely remove the organic matter on the surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 min, and the cleaning was repeated 10 times.

[0032] (2) Weigh 0.17 g of AgNO 3 And measure 18mL of HF solution, pour it into a beaker and stir it evenly to prepare 200mL of silver deposition solution with a silver ion concentration of 0.005mol / L; weigh 8.75g of KOH and dissolve it in an appropriate amount of deionized water, add 25mL of isopropyl alcohol (IPA), mix it thoroughly and transfer it to a 250mL volumetric flask, and transfer it to a reagent bottle after constant volume as an etching solution for standby use. Immerse the silicon wafer in the silver deposition solution for 5s, then immerse it in the etching solution and heat it in a 70℃ water bath for 30min. Prepare a solution of deionized water: nitric acid = 1:1 (volume ratio), stir it evenly, and then immerse the etched silicon wafer for 5min to remove the silver deposited on the surface of the silicon wafer. Finally, take out the soaked silicon wafer and rinse it repeatedly with deionized water, and heat it in N 2 The mixture was dried at 30°C for 60 min under an atmosphere to obtain a silicon pyramid array for later use.

[0033] (3) Weigh 15.3 mg AgNO 3 Dissolve in 10 mL of ethanol and label it as solution A; weigh 10.7 mg Na 2 HPO 4 Dissolve in 10 mL of deionized water and mark it as solution B. Soak the silicon pyramid array in solution A for 30 min, then take out the silicon pyramid array and soak it in solution B for 1 min, then take out the silicon pyramid array and soak it in solution A for 1 min, repeat this 10 times to obtain Ag 3 PO 4 / Si pyramid array composite material.

[0034] Example 2

[0035] A kind of Ag 3 PO 4 / A method for preparing a Si pyramid array photoelectric catalyst comprises the following steps:

[0036] (1) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 min in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 20 min to completely remove the organic matter on the surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 min, and the cleaning was repeated 10 times.

[0037] (2) Weigh 0.17 g of AgNO 3 And measure 18mL of HF solution, pour it into a beaker and stir it evenly to prepare 200mL of silver deposition solution with a silver ion concentration of 0.005mol / L; weigh 8.75g of KOH and dissolve it in an appropriate amount of deionized water, add 25mL of isopropyl alcohol (IPA), mix it thoroughly and transfer it to a 250mL volumetric flask, and transfer it to a reagent bottle after constant volume as an etching solution for standby use. Immerse the silicon wafer in the silver deposition solution for 5s, then immerse it in the etching solution and heat it in a 70℃ water bath for 30min. Prepare a solution of deionized water: nitric acid = 1:1 (volume ratio), stir it evenly, and then immerse the etched silicon wafer for 5min to remove the silver deposited on the surface of the silicon wafer. Finally, take out the soaked silicon wafer and rinse it repeatedly with deionized water, and heat it in N 2 Dry at 30°C for 60 min under ambient temperature and set aside.

[0038] (3) Weigh 15.3 mg AgNO 3 Dissolve in 10 mL of ethanol and label it as solution A; weigh 10.7 mg Na 2 HPO 4 Dissolve in 10 mL of deionized water and mark it as solution B. Soak the silicon pyramid array in solution A for 30 min, then take out the silicon pyramid array and soak it in solution B for 1 min, then take out the silicon pyramid array and soak it in solution A for 1 min, repeat this 20 times to obtain Ag 3 PO 4 / Si pyramid array composite material.

[0039] Example 3

[0040] A kind of Ag 3 PO 4 / A method for preparing a Si pyramid array photoelectric catalyst comprises the following steps:

[0041] (1) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 min in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 20 min to completely remove the organic matter on the surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 min, and the cleaning was repeated 10 times.

[0042] (2) Weigh 0.17 g of AgNO 3 And measure 18mL of HF solution, pour it into a beaker and stir it evenly to prepare 200mL of silver deposition solution with a silver ion concentration of 0.005mol / L; weigh 8.75g of KOH and dissolve it in an appropriate amount of deionized water, add 25mL of isopropyl alcohol (IPA), mix it thoroughly and transfer it to a 250mL volumetric flask, and transfer it to a reagent bottle after constant volume as an etching solution for standby use. Immerse the silicon wafer in the silver deposition solution for 5s, then immerse it in the etching solution and heat it in a 70℃ water bath for 30min. Prepare a solution of deionized water: nitric acid = 1:1 (volume ratio), stir it evenly, and then immerse the etched silicon wafer for 5min to remove the silver deposited on the surface of the silicon wafer. Finally, take out the soaked silicon wafer and rinse it repeatedly with deionized water, and heat it in N 2 Dry at 30°C for 60 min under ambient temperature and set aside.

[0043] (3) Weigh 15.3 mg AgNO 3 Dissolve in 10 mL of ethanol and label it as solution A; weigh 10.7 mg Na 2 HPO 4 Dissolve in 10 mL of deionized water and mark it as solution B. Soak the silicon pyramid array in solution A for 30 min, then take out the silicon pyramid array and soak it in solution B for 1 min, then take out the silicon pyramid array and soak it in solution A for 1 min, repeat this 30 times, and obtain Ag 3 PO 4 / Si pyramid array composite material.

[0044] Example 4

[0045] A kind of Ag 3 PO 4 / A method for preparing a Si pyramid array photoelectric catalyst comprises the following steps:

[0046] (1) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 min in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide in a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 20 min to completely remove the organic matter on the surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 min, and the cleaning was repeated 10 times.

[0047] (2) Weigh 0.17 g of AgNO 3And measure 18mL of HF solution, pour it into a beaker and stir it evenly to prepare 200mL of silver deposition solution with a silver ion concentration of 0.005mol / L; weigh 8.75g of KOH and dissolve it in an appropriate amount of deionized water, add 25mL of isopropyl alcohol (IPA), mix it thoroughly and transfer it to a 250mL volumetric flask, and transfer it to a reagent bottle after constant volume as an etching solution for standby use. Immerse the silicon wafer in the silver deposition solution for 5s, then immerse it in the etching solution and heat it in a 70℃ water bath for 30min. Prepare a solution of deionized water: nitric acid = 1:1 (volume ratio), stir it evenly, and then immerse the etched silicon wafer for 5min to remove the silver deposited on the surface of the silicon wafer. Finally, take out the soaked silicon wafer and rinse it repeatedly with deionized water, and heat it in N 2 Dry at 30°C for 60 min under ambient temperature and set aside.

[0048] (3) Weigh 15.3 mg AgNO 3 Dissolve in 10 mL of ethanol and label it as solution A; weigh 10.7 mg Na 2 HPO 4 Dissolve in 10 mL of deionized water and mark it as solution B. Soak the silicon pyramid array in solution A for 30 min, then take out the silicon pyramid array and soak it in solution B for 1 min, then take out the silicon pyramid array and soak it in solution A for 1 min, repeat this 40 times, and obtain Ag 3 PO 4 / Si pyramid array composite material.

[0049] In the wavelength range of 300-800nm, the absorbance of the planar silicon before etching and the silicon pyramid array obtained after etching in Example 1 was tested using an ultraviolet-visible spectrophotometer. Figure 3 It can be seen that compared with the planar silicon before etching, the silicon pyramid array after etching has higher absorbance and higher light utilization efficiency.

[0050] In the CHI660D electrochemical workstation, the light intensity was 100 mW / cm 2 The xenon lamp was used as the light source, with 0.1 mol / L Na 2 SO 4 The solution is an electrolyte, using a Pt sheet electrode as a cathode and the Ag prepared in Example 1-4. 3 PO 4 The three-electrode system with Si / Si pyramid array photoelectrocatalyst as photoanode and saturated Ag / AgCl electrode as reference electrode was used to test Ag 3 PO 4 / Photocurrent density of Si pyramid array electrode.

[0051] Figure 4 For silicon pyramid arrays and Ag 3 PO4 Linear sweep voltammetric characteristic curve of Ag / Si pyramid array photocatalyst. It can be seen from the figure that compared with the silicon pyramid array, 3 PO 4 / Si pyramid array photocathode has a significant increase in photocurrent density under the same bias voltage. When the bias voltage is 1V (vs. RHE), the Ag prepared in Example 2 3 PO 4 The photocurrent density of Si pyramid array is 1.94 mA / cm 2 , which is significantly larger than the 0.0004 mA / cm of the silicon pyramid. 2 Therefore, compared with silicon pyramid arrays, Ag 3 PO 4 / Si pyramid array has higher efficiency in transporting photogenerated carriers and better photoelectrocatalytic performance.

[0052] The Ag prepared in Examples 1-4 3 PO 4 / Si pyramid array photoelectrocatalyst is used as photoanode. Under the bias voltage of 0.5V and xenon lamp irradiation (filter: AM 1.5G, light intensity: 100mW / cm 2 ), for the removal of 10 mg / L tetracycline hydrochloride (TC), such as Figure 5 As shown, the three-hour removal rates of the samples prepared in Examples 1-4 are 41.3%, 40.0%, 44.0% and 41.9%, respectively, which are improved compared with the degradation effect (9%) of a single silicon pyramid array.

[0053] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field 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 should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Ag3PO4 / Si pyramid array photoelectric catalyst, characterized in that: The method specifically comprises the following steps: (1) Pre-treating the silicon wafer and preparing a silicon pyramid array by metal-assisted wet alkaline etching for standby use; The method of metal-assisted wet alkaline etching comprises the following steps: AgNO3, HF and deionized water are stirred evenly to form a silver deposition solution, a certain amount of KOH, isopropanol and deionized water are mixed and fully mixed to form an etching solution; a silicon wafer is immersed in the silver deposition solution for 5-10 seconds, and then placed in the etching solution for etching, and then the surface of the etched silicon wafer is rinsed with deionized water; a mixed solution of deionized water and nitric acid is prepared, stirred evenly, and then the etched silicon wafer is immersed in it for 5-10 minutes to remove the silver generated on the surface of the silicon array; the immersed silicon wafer is taken out and repeatedly rinsed with deionized water, and dried in a N2 atmosphere to obtain a silicon pyramid array; (2) The Ag3PO4 / Si pyramid array composite material was prepared by the impregnation method: an appropriate amount of AgNO3 was dissolved in ethanol, marked as solution A, and an appropriate amount of Na2HPO4 was dissolved in deionized water, marked as solution B. The silicon pyramid array was immersed in solution A, and then the silicon pyramid array was taken out and immersed in solution B for a period of time, and then the silicon pyramid array was taken out and immersed in solution A for a period of time. This was repeated several times to obtain the above-mentioned Ag3PO4 / Si pyramid array photoelectric catalyst.

2. The method for preparing a Ag3PO4 / Si pyramid array photoelectrocatalyst according to claim 1, characterized in that: In the step (1), the method for pretreating the silicon wafer is as follows: the single-side polished silicon wafer is respectively placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning, and then the silicon wafer is placed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide for water bath heating, and finally the silicon wafer is placed in deionized water for ultrasonic cleaning.

3. The method for preparing a Ag3PO4 / Si pyramid array photoelectrocatalyst according to claim 2, characterized in that: The single-side polished silicon wafer is ultrasonically cleaned for 20 minutes, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3:1, the water bath heating temperature is 75-85°C, the time is 15-30 minutes, and the silicon wafer after water bath heating is ultrasonically cleaned in deionized water for 8-10 times, each time for 3 minutes.

4. The method for preparing a Ag3PO4 / Si pyramid array photoelectrocatalyst according to claim 1, characterized in that: In the silver deposition solution, the concentration of AgNO3 is 0.004-0.006 mol / L, and the volume percentage of HF is 5%-10%; In the etching solution, the mass percentage of KOH is 1.5%-3.5%, and the volume percentage of isopropanol is 5%-20%; In the mixed solution, the volume ratio of nitric acid to deionized water is 1:1; The etching time is 30-60 min, and the etching temperature is 60-80°C; The drying time is 30-60 minutes and the drying temperature is 30-50°C.

5. The method for preparing a Ag3PO4 / Si pyramid array photoelectrocatalyst according to claim 1, characterized in that: In the step (2), the concentration of the AgNO3 solution is 0.006-0.012 mol / L, the concentration of the Na2HPO4 solution is 0.002-0.004 mol / L, the immersion time in solution A is 30-60 min, the immersion time in solution A and solution B is 1-3 min respectively, and the immersion is repeated 10-40 times.

6. An Ag3PO4 / Si pyramid array photoelectric catalyst prepared by the method for preparing the Ag3PO4 / Si pyramid array photoelectric catalyst according to any one of claims 1 to 5, characterized in that: The Ag3PO4 / Si pyramid array photoelectric catalyst is composed of Ag3PO4 nanoparticle silicon pyramid array, and the Ag3PO4 nanoparticles are loaded on the surface of the silicon pyramid array.

7. A method for photoelectrocatalytic degradation of antibiotics, characterized in that: The Ag3PO4 / Si pyramid array photoelectric catalyst described in claim 6 is used as the photoanode.

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