BiVO4 / Si pyramid array photoelectric catalyst as well as preparation method and application thereof

Abstract

The invention discloses a BiVO4 / Si pyramid array photoelectric catalyst and a preparation method and application thereof, the photoelectric catalyst is composed of BiVO4 nanoparticles and a silicon pyramid array, the BiVO4 nanoparticles are loaded on the surface of the silicon pyramid array, and the BiVO4 nanoparticles are obtained through wet alkaline etching. Specifically, a silicon pyramid array is prepared by adopting a metal-assisted wet alkaline etching method, and then BiVO4 nanoparticles are loaded on the surface of the silicon pyramid array by adopting a spin coating method. According to the preparation method, the oxidative degradation capability of the silicon pyramid array is improved by utilizing the relatively positive valence band position of BiVO4. In addition, the sample prepared by the method is a blocky solid catalyst, and is more favorable for recycling compared with a traditional powder catalyst.

Description

Technical Field

[0001] The present invention relates to the field of photoelectrocatalytic technology, and particularly relates to a BiVO 4 / Si pyramid array photocatalyst and its preparation method and application. Background Art

[0002] In the medical, livestock and pharmaceutical industries, a large amount of antibiotic wastewater has led to a significant decline in the quality of the natural environment. The residual amount of antibiotics in food is usually very small, but it may accumulate in the continuous food chain cycle, which will cause potential or direct harm to our bodies. Long-term consumption of food with residual antibiotics may lead to the emergence of drug-resistant bacteria, thus seriously affecting disease treatment. In addition, some antibiotics such as ciprofloxacin, amoxicillin, tetracycline, and antibiotic-like substances may cause allergies in susceptible populations even at very low doses. Therefore, from the perspectives of environmental protection and life safety, it is urgent to solve the problem of antibiotic pollution.

[0003] Silicon pyramid arrays have potential application prospects in the field of photoelectrocatalytic water treatment because of their narrow bandgap that can absorb a wider solar spectrum and their large specific surface area that can enhance the utilization rate of light. However, due to the large difference in the hole and electron mobility, the photo-generated charges are easily recombined, and the charge separation efficiency is low; the oxidation ability of valence band holes is not sufficient to oxidize and degrade most organic pollutants. And BiVO 4 nanoparticles, although having a relatively strong oxidation ability at the valence band position, are not easy to recycle and it is difficult to maintain the photocatalytic activity.

[0004] To address the above problems, combining the two to construct a heterojunction to improve the photo-generated charge separation efficiency and preparing nano-sized materials to enhance the oxidation ability of valence band holes, etc., are still urgent problems to be solved in the field of silicon material photoelectrocatalysis. Summary of the Invention

[0005] The purpose of the present invention is to provide a BiVO 4 / Si pyramid array photocatalyst and its preparation method and application, which form a heterojunction between BiVO 4 and the silicon pyramid array, improving the photoelectrocatalytic degradation performance of the silicon pyramid array.

[0006] In one aspect of the present invention, the present invention provides a BiVO 4 / Si pyramid array photocatalyst. According to an embodiment of the present invention, it is composed of BiVO 4 nanoparticles and a silicon pyramid array, and the BiVO 4 nanoparticles are loaded on the surface of the silicon pyramid array.

[0007] In another aspect of the present invention, the present invention provides a BiVO 4Preparation method of BiVO₄ / Si pyramid array photocatalyst. According to an embodiment of the present invention, a silicon pyramid array is prepared by a metal-assisted wet chemical etching method, and then BiVO₄ 4 nanoparticles are loaded on the surface of the silicon pyramid array by a spin coating method.

[0008] In addition, a preparation method of a BiVO₄ 4 / Si pyramid array photocatalyst according to the above embodiment of the present invention may further have the following additional technical features:

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

[0010] (1) Pretreat the silicon wafer, and prepare a silicon pyramid array by a metal-assisted wet chemical etching method for later use;

[0011] (2) Prepare BiVO₄ 4 nanoparticles: Add Bi(NO₃)₃ 3 ·5H₂O and NH₄VO₃ 2 aqueous solutions into an aqueous solution of C₆H₅COONa, stir evenly, and then place them in a reaction kettle to heat up and react to obtain BiVO₄ 4 nanoparticles; 3 17 33 4 4 4 4 (3) Prepare a BiVO₄

[0012] / Si pyramid array composite material by a spin coating method: Disperse the BiVO₄ 4 nanoparticles in toluene and ultrasonically oscillate to obtain a dispersion liquid. Take the dispersion liquid and spin coat it on the silicon pyramid array, and then obtain the BiVO₄ 4 / Si pyramid array photocatalyst after heat treatment. 4 / Si pyramid array photocatalyst.

[0013] In some embodiments of the present invention, in step (1), the method of pre-treating the silicon wafer is as follows: Put the single-side polished silicon wafer into acetone, absolute ethanol, and deionized water for ultrasonic cleaning respectively, then put the silicon wafer into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for water bath heating, and finally put the silicon wafer into deionized water for ultrasonic cleaning.

[0014] In some embodiments of the present invention, the ultrasonic cleaning time of the single-side polished silicon wafer is 10 - 30 min respectively, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3:(1 - 2), the temperature of the water bath heating is 60 - 80 °C, the time of the water bath is 10 - 30 min, and the silicon wafer after water bath heating is ultrasonically cleaned in deionized water 3 - 5 times, with each time being 2 - 3 min.

[0015] In some embodiments of the present invention, in step (1), the metal-assisted wet alkaline etching method comprises the following steps:

[0016] a. AgNO 3 , HF and deionized water are stirred evenly to prepare a silver deposition solution, and KOH, isopropanol and deionized water are mixed thoroughly to prepare an etching solution;

[0017] b. Immerse the silicon wafer in the silver deposition solution for 5-10 seconds, then etch it in the etching solution, and then rinse the etched silicon wafer surface with deionized water;

[0018] c. Prepare a mixed solution of deionized water and nitric acid, stir evenly, and then immerse the etched silicon wafer in it for 5-10 minutes to remove the silver generated on the surface of the silicon array;

[0019] d. Take out the soaked silicon wafer and rinse it repeatedly with deionized water. 2 The silicon pyramid array was obtained by drying under atmosphere.

[0020] In some embodiments of the present invention, in step a, the silver deposition solution contains AgNO 3 The concentration of isopropyl alcohol is 0.004-0.006 mol / L, and the volume percentage of HF is 9%; the mass percentage of KOH in the etching solution is 3.5%, and the volume percentage of isopropyl alcohol is 20%; in step b, the etching time is 20-40 min, and the etching temperature is 70°C; in step c, the volume ratio of nitric acid to deionized water in the mixed solution is 1:(1-2); in step d, the drying time is 30 min, and the drying temperature is 30-50°C.

[0021] In some embodiments of the present invention, in step (2), the Bi(NO) 3 ·5H 2 O、NH 4 VO 3 , C 17 H 33 The molar ratio of COONa is in the range of 1:1:(1-2). The temperature of the temperature-raising reaction is 90-110° C., and the reaction time is 8-10 hours.

[0022] In some embodiments of the present invention, the spin coating method first performs pre-spin coating at a speed of 900-1100 r / min for 30-50 s; then performs spin coating at a speed of 2000-4000 r / min for 50-70 s; 1 cm 2 The loading amount of the dispersion on the silicon pyramid array is 20-80 μL; the temperature of the heat treatment is 180-200° C., and the time is 1.5-2.5 h.

[0023] In another aspect of the present invention, the present invention provides a method for degrading antibiotics using a photocatalyst. According to an embodiment of the present invention, the BiVO 4 / Si pyramid array photocatalyst is used as the photoanode for photocatalysis. The specific steps are as follows: Using the BiVO 4 / Si pyramid array photocatalyst as the photoanode and a platinum sheet electrode as the photocathode, a positive bias voltage of 0.7 - 0.9 V is applied to the photoanode through a DC regulated power supply, and an aqueous solution containing antibiotics is degraded using a xenon lamp with AM 1.5G and a light intensity of 90 - 110 mW / cm 2 .

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) Compared with a planar silicon substrate as the photocatalyst, the BiVO 4 / Si pyramid array photocatalyst has a light trapping effect on the surface of the silicon pyramid array, which enhances the scattering probability of incident light and can improve the light absorption efficiency.

[0026] (2) In the present invention, BiVO 4 nanoparticles are prepared by a simple solvothermal method, and then the particles are attached to the surface of the silicon pyramid array by spin coating to construct a heterojunction. Utilizing the advantage of the valence band and conduction band matching of the two can improve the oxidative degradation ability of the silicon pyramid array.

[0027] (3) Compared with traditional powdered nanoparticle catalysts, the photocatalyst of the present invention is not only easy to recycle but also can avoid secondary pollution of water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the preparation method of the BiVO 4 / Si pyramid array photocatalyst in Example 1 of the present invention;

[0029] Figure 2 is the XRD pattern of the BiVO 4 nanoparticles and the Si pyramid array photocatalyst prepared in Example 1 of the present invention;

[0030] Figure 3 is the SEM image and EDS analysis of the spin-coated silicon pyramid array in Example 1 of the present invention; among them, Figure (a) is the original image of the BiVO 4 / Si pyramid array, and Figures (b), (c), (d), and (e) are the schematic diagrams of the distributions of elements O, Bi, V, and Si, respectively.

[0031] Figure 4Photodegradation performance graph of the photocatalyst and Si pyramid array in Application Example 1 of the present invention. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Embodiment 1

[0034] A preparation method of a BiVO 4 / Si pyramid array photocatalyst, as Figure 1 shown, includes the following steps:

[0035] (1) Ultrasonically clean the silicon wafer with acetone, absolute ethanol, and deionized water in sequence for 20 min, then put it into a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, keep it at a constant temperature of 80 °C in a water bath for 20 min to completely remove the organic substances on its surface. After that, ultrasonically clean the silicon wafer with deionized water for 3 min and repeat the cleaning 10 times.

[0036] (2) Weigh 0.17 g of AgNO 3 and measure 18 mL of HF solution, pour them into a beaker and stir evenly to prepare 200 mL of silver deposition solution with a silver ion concentration of 0.005 mol / L; weigh 8.75 g of KOH and dissolve it in an appropriate amount of deionized water, add 25 mL of isopropyl alcohol (IPA), fully mix and transfer it to a 250 mL volumetric flask, make up the volume and transfer it to a reagent bottle for use as an etching solution. Immerse the silicon wafer in the silver deposition solution for 5 s, then immerse it in the etching solution, and heat it in a water bath at 70 °C for 30 min. Prepare a solution of deionized water:nitric acid = 3:1 (volume ratio), stir evenly, and then immerse the etched silicon wafer in it for 5 min to remove the silver deposited on the surface of the silicon wafer. Finally, take out the immersed silicon wafer and rinse it repeatedly with deionized water, and dry it at 30 °C for 60 min in an N 2 atmosphere to obtain a silicon pyramid array for standby.

[0037] (3) Weigh 0.097 g (0.1 mmol) of Bi(NO) 3 ·5H 2 O and grind it into powder, dissolve 0.0234 g (0.1 mmol) of NH 4 VO 3 in 20 ml of deionized water, and dissolve 0.1218 g (0.2 mmol) of C 17 H33 Dissolve COONa in 20 ml of deionized water, then pour the above solution and powder into a reaction kettle. The reaction time using the solvothermal method is 10 hours and the reaction temperature is 100 °C, and then BiVO 4 nanoparticles can be obtained.

[0038] (4) Disperse the obtained BiVO 4 nanoparticles in toluene and ultrasonically oscillate for 30 min to obtain a uniformly dispersed solution. Use a pipette to transfer 20 μL of the dispersed solution, spin-coat for 40 s under the condition of a pre-spin-coating speed of 1000 r / min, and spin-coat for 60 s under the condition of a spin-coating speed of 3000 r / min, so as to uniformly spin-coat 20 μL of the BiVO 4 nanoparticle dispersion onto the surface of the silicon pyramid array, and then heat-treat at 200 °C for 2 h to increase its binding energy, and then the BiVO 4 / Si pyramid array photocatalyst can be obtained.

[0039] Figure 2 shows the X-ray diffraction pattern of the prepared sample. The typical peaks at 28.8° and 30.5° correspond to the (121) and (040) crystal planes respectively. The diffraction pattern of BiVO 4 can refer to the standard XRD pattern (PDF No. 14-0688), indicating that it is BiVO with a monoclinic scheelite structure 4 .

[0040] Figure 3 was taken using a thermal field emission scanning electron microscope with a resolution of 2-3 nm. Figure 3 (a) is the BiVO 4 / Si pyramid array. EDS analysis shows that the BiVO 4 nanoparticles are dispersed on the surface of the silicon pyramid array.

[0041] Example 2

[0042] The preparation method of a BiVO 4 / Si pyramid array photocatalyst in this example is different from that of Example 1 only in that: the spin-coating amount of the BiVO 4 dispersed solution in step (4) is 40 μL, and the other steps and parameters are the same.

[0043] Example 3

[0044] The preparation method of a BiVO 4 / Si pyramid array photocatalyst in this example is different from that of Example 1 only in that: the spin-coating amount of the BiVO 4 dispersed solution in step (4) is 60 μL, and the other steps and parameters are the same.

[0045] Example 4

[0046] A kind of BiVO 4 / Si pyramid array photocatalyst preparation method is only different from that of Example 1 in that: the spin coating amount of the BiVO 4 dispersion liquid is 80 μL, and other steps and parameters are the same.

[0047] Comparative Example 1

[0048] A kind of Si pyramid array photocatalyst, which is the silicon pyramid array obtained in step (2) of Example 1.

[0049] Application Example 1

[0050] A method for degrading antibiotics by a photocatalyst, comprising the following steps:

[0051] Respectively use the BiVO 4 / Si pyramid array photocatalyst prepared in Examples 1-4 and the Si pyramid array photocatalyst of Comparative Example 1 as the photoanode, use a platinum sheet electrode as the photocathode, apply a positive bias voltage of 0.8 V to the photoanode through a DC regulated power supply, and use a xenon lamp with AM 1.5G and a light intensity of 100 mW / cm 2 as the light source to degrade a 10 mg / L aqueous solution of tetracycline hydrochloride (TC).

[0052] As Figure 4 shown, the degradation effect of a single silicon pyramid array is 40%. When the spin coating amount of the dispersion liquid is 20 μL, the photocatalytic degradation efficiency of this sample for tetracycline hydrochloride is only 84.4%. When the spin coating amount of the dispersion liquid is 40 μL, the photocatalytic degradation efficiency of this system for tetracycline hydrochloride is only 88.2%. According to subsequent analysis, it can be seen that due to too little spin coating amount, the BiVO 4 nanoparticles cannot completely cover the surface of SiMPs and cannot reach the optimal efficiency. When the spin coating amount of the dispersion liquid reaches 60 μL, the photocatalytic degradation efficiency of this system for tetracycline hydrochloride is increased to 97.9%. According to subsequent analysis, it can be seen that at this time, the appropriate spin coating amount enables the BiVO 4 nanoparticles to better cover the surface of SiMPs and does not affect the performance of SiMPs itself, thus reaching the optimal efficiency. When the spin coating amount of the dispersion liquid increases to 80 μL, the photocatalytic degradation efficiency of this system for tetracycline hydrochloride drops to 80.1%. According to subsequent analysis, it can be seen that due to too much spin coating amount, the BiVO 4 nanoparticles accumulate in the grooves of SiMPs and affect its light absorption performance. At the same time, BiVO 4If too many nanoparticles are spin-coated, they are extremely prone to aggregation, ultimately leading to a decrease in efficiency. In summary, compared with the degradation effect of a single silicon pyramid array, the photocatalysts of Examples 1-4 have a certain improvement.

[0053] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the structure of the present invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A BiVO4 / Si pyramid array photoelectric catalyst, characterized in that: The invention is composed of BiVO4 nanoparticles and silicon pyramid arrays, wherein the BiVO4 nanoparticles are loaded on the surface of the silicon pyramid arrays.

2. A method for preparing the BiVO4 / Si pyramid array photoelectrocatalyst according to claim 1, characterized in that: The silicon pyramid array is prepared by metal-assisted wet alkaline etching, and then BiVO4 nanoparticles are loaded on the surface of the silicon pyramid array by spin coating.

3. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 2, characterized in that: The following steps are involved: (1) Pre-treating a silicon wafer, and preparing a silicon pyramid array by a metal-assisted wet alkaline etching method for standby use; (2) Preparation of BiVO4 nanoparticles: Bi(NO)3·5H2O and NH4VO3 aqueous solution were added to C 17 H 33 COONa aqueous solution, stirred evenly, put into a reactor and heated to react to obtain BiVO4 nanoparticles; (3) The BiVO4 / Si pyramid array composite material is prepared by spin coating: BiVO4 nanoparticles are dispersed in toluene and ultrasonically vibrated to obtain a dispersion, the dispersion is spin coated on a silicon pyramid array, and the BiVO4 / Si pyramid array photoelectric catalyst is obtained after heat treatment.

4. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 3, characterized in that: 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, respectively, 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.

5. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 4, characterized in that: The ultrasonic cleaning time of the single-sided polished silicon wafer is 10-30 minutes, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3:(1-2), the water bath heating temperature is 60-80°C, the water bath time is 10-30 minutes, and the silicon wafer after water bath heating is ultrasonically cleaned in deionized water for 3-5 times, each time for 4-5 minutes.

6. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 3, characterized in that: In step (1), the metal-assisted wet alkaline etching method comprises the following steps: a. AgNO3, HF and deionized water are stirred to prepare a silver deposition solution, and KOH, isopropanol and deionized water are mixed to prepare an etching solution; b. Immerse the silicon wafer in the silver deposition solution for 5-10 seconds, then etch it in the etching solution, and then rinse the etched silicon wafer surface with deionized water; c. Prepare a mixed solution of deionized water and nitric acid, stir evenly, and then immerse the etched silicon wafer in it for 5-10 minutes to remove the silver generated on the surface of the silicon array; d. Take out the soaked silicon wafer and rinse it repeatedly with deionized water, and dry it in a N2 atmosphere to obtain a silicon pyramid array.

7. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 6, characterized in that: In step a, the concentration of AgNO3 in the silver deposition solution is 0.004-0.006 mol / L, and the volume percentage of HF is 9%; the mass percentage of KOH in the etching solution is 3.5%, and the volume percentage of isopropanol is 20%; In step b, the etching time is 20-40 minutes, and the etching temperature is 60-80°C; In step c, the volume ratio of nitric acid to deionized water in the mixed solution is 1:(1-2); In step d, the drying time is 20-40 minutes and the drying temperature is 30-50°C.

8. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 3, characterized in that: In step (2), the Bi(NO)3·5H2O, NH4VO3, C 17 H 33 The molar ratio of COONa is 1:1:(1-2), the temperature of the temperature-raising reaction is 90-110° C., and the reaction time is 8-10 hours.

9. The method for preparing a BiVO4 / Si pyramid array photoelectrocatalyst according to claim 3, characterized in that: In step (3): The spin coating method first performs pre-spin coating at a speed of 900-1100 r / min for 30-50 s; then performs spin coating at a speed of 2000-4000 r / min for 50-70 s; 1cm 2 The loading amount of the dispersion on the silicon pyramid array is 20-80 μL; The heat treatment temperature is 180-200° C. and the time is 1.5-2.5 hours.

10. A method for degrading antibiotics using a photoelectrocatalyst, characterized in that: The BiVO4 / Si pyramid array photoelectric catalyst described in claim 1 is used as the anode for photoelectric catalysis.

Images