Silicon nanowire material and preparation method thereof

Abstract

The invention discloses a silicon nanowire material and a preparation method thereof, and belongs to the technical field of secondary resource utilization. The preparation method comprises the following steps: pre-treating a waste photovoltaic silicon plate to obtain a high-purity silicon wafer; putting a high-purity silicon wafer into the deposition solution, and depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafer under the action of an electric field; and putting the high-purity silicon wafer into the etching solution, and etching the high-purity silicon wafer under the action of an electric field to obtain the silicon nanowire material. According to the method, the etching rate can be increased, and the silicon nanowire material which is uniform in distribution, high in morphology consistency, high in specific surface area and excellent in electrochemical performance is obtained.

Description

Technical Field

[0001] The present disclosure relates to the technical field of secondary resource utilization, and in particular to a silicon nanowire material and a preparation method thereof. Background Art

[0002] As the global energy mix shifts toward renewable energy, the photovoltaic power generation industry has experienced explosive growth in recent years. Silicon panels, the foundational material for crystalline silicon photovoltaic solar cells, are discarded in significant quantities. Silicon nanowires, used as negative electrodes in lithium-ion batteries, can stabilize the electrode structure. Therefore, utilizing discarded photovoltaic silicon panels to prepare silicon nanowires for use in high-performance lithium-ion batteries is crucial for achieving high-value recycling of discarded photovoltaic silicon panels.

[0003] In related technologies, the preparation method of silicon nanowire material includes: pre-treating discarded photovoltaic silicon panels to obtain high-purity silicon wafers, depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafers, and then etching the high-purity silicon wafers to obtain silicon nanowire material.

[0004] However, when using traditional chemical deposition to form metal catalyst nanoparticles, the surface energy difference may cause the metal catalyst nanoparticles to agglomerate and be unevenly distributed, and the etching reaction rate is low and the etching direction is random, resulting in poor morphological consistency of silicon nanowire materials and low specific surface area, which affects the electrochemical performance of silicon nanowire materials. Summary of the Invention

[0005] This disclosure provides a silicon nanowire material and a preparation method thereof, which can accelerate the etching rate and obtain a silicon nanowire material with uniform distribution, high morphological consistency, high specific surface area, and excellent electrochemical performance. The technical solution includes at least the following solutions:

[0006] On the one hand, a method for preparing silicon nanowire material is provided, comprising: pre-treating discarded photovoltaic silicon panels to obtain high-purity silicon wafers; placing the high-purity silicon wafers in a deposition solution, and depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafers under the action of an electric field; placing the high-purity silicon wafers in an etching solution, and etching the high-purity silicon wafers under the action of an electric field to obtain the silicon nanowire material.

[0007] Optionally, depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafer under the action of an electric field comprises: using the high-purity silicon wafer as a cathode, using a platinum electrode as an anode and immersing the high-purity silicon wafer in the deposition solution, and applying a current density of 0.1 mA / cm 2 Up to 1mA / cm 2 The metal catalyst nanoparticles are deposited on the surface of the high-purity silicon wafer at a constant current of 0.5V or a constant voltage of 0.5V to 2V.

[0008] Optionally, the duration of deposition under the action of the electric field is 3 minutes to 5 minutes.

[0009] Optionally, etching the high-purity silicon wafer under the action of an electric field comprises: using the high-purity silicon wafer as an anode, using a platinum electrode as a cathode and immersing the wafer in the etching solution, applying a current density of 0.5 mA / cm 2 Up to 2mA / cm 2 The high-purity silicon wafer is etched using a constant current of 0.5V or a constant voltage of 0.5V to 2V.

[0010] Optionally, the duration of etching the high-purity silicon wafer under the action of the electric field is 20 minutes to 40 minutes.

[0011] Optionally, the deposition solution includes a mixed solution of HF with a concentration of 4 mol / L to 5.5 mol / L and AgNO 3 with a concentration of 0.02 mol / L to 0.05 mol / L.

[0012] Optionally, the etching solution includes a mixed solution of HF with a concentration of 4.8 mol / L and H2O2 with a concentration of 5% to 30%.

[0013] Optionally, the pre-treatment of the waste photovoltaic silicon panels includes removing organic impurities, metal impurities and oxide impurities in the waste photovoltaic silicon panels by heating treatment and wet treatment.

[0014] Optionally, the method further comprises: cleaning and drying the etched high-purity silicon wafer.

[0015] On the other hand, a silicon nanowire material is provided, wherein the silicon nanowire material is prepared by any of the aforementioned preparation methods.

[0016] The beneficial effects of the technical solutions provided by the embodiments of the present disclosure include at least:

[0017] In the disclosed embodiments, metal catalyst nanoparticles are deposited on the surface of a high-purity silicon wafer under the action of an electric field. The electric field can evenly distribute electrons on the surface of the high-purity silicon wafer, reduce local electron enrichment caused by surface energy differences during the deposition process, and inhibit the agglomeration of the metal catalyst nanoparticles. The electric field can also regulate the reduction rate of the metal catalyst ions so that the reduction rate is more closely matched to the diffusion rate, reducing the size differences of the metal catalyst nanoparticles caused by local concentration gradients, thereby allowing the metal catalyst nanoparticles to be more evenly deposited on the surface of the high-purity silicon wafer. The high-purity silicon wafer is then etched under the action of an electric field. The electric field can accelerate the etching rate, form holes, and drive the holes to migrate in a direction perpendicular to the surface of the high-purity silicon wafer, inhibiting lateral diffusion, thereby performing high-speed and high-quality etching of the high-purity silicon wafer at the evenly distributed metal catalyst nanoparticles, ultimately obtaining a silicon nanowire material with uniform distribution, high morphological consistency, high specific surface area, and excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 This is a flow chart of a method for preparing a silicon nanowire material provided by an embodiment of the present disclosure;

[0020] Figure 2 is a flow chart of another method for preparing silicon nanowire material provided by an embodiment of the present disclosure;

[0021] Figure 3 is a schematic diagram of the morphology of a silicon nanowire material provided by an embodiment of the present disclosure;

[0022] Figure 4 This is a schematic diagram of the first 100 cycle performance and corresponding coulombic efficiency of a lithium battery with a negative electrode made of silicon nanowire material provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar terms used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprising" mean that the elements or objects preceding "include" or "comprising" encompass the elements or objects listed after "include" or "comprising," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. "A and / or B" indicates three situations: A, B, and A and B.

[0024] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0025] Figure 1 This is a flow chart of a method for preparing a silicon nanowire material provided by an embodiment of the present disclosure. Figure 1 As shown, the preparation method comprises:

[0026] In step S101, waste photovoltaic silicon panels are pre-processed to obtain high-purity silicon wafers.

[0027] In step S102 , a high-purity silicon wafer is placed in a deposition solution, and metal catalyst nanoparticles are deposited on the surface of the high-purity silicon wafer under the action of an electric field.

[0028] In step S103, a high-purity silicon wafer is placed in an etching solution, and the high-purity silicon wafer is etched under the action of an electric field to obtain a silicon nanowire material.

[0029] In the disclosed embodiments, metal catalyst nanoparticles are deposited on the surface of a high-purity silicon wafer under the action of an electric field. The electric field can evenly distribute electrons on the surface of the high-purity silicon wafer, reduce local electron enrichment caused by surface energy differences during the deposition process, and inhibit the agglomeration of the metal catalyst nanoparticles. The electric field can also regulate the reduction rate of the metal catalyst ions so that the reduction rate is more closely matched to the diffusion rate, reducing the size differences of the metal catalyst nanoparticles caused by local concentration gradients, thereby allowing the metal catalyst nanoparticles to be more evenly deposited on the surface of the high-purity silicon wafer. The high-purity silicon wafer is then etched under the action of an electric field. The electric field can accelerate the etching rate, form holes, and drive the holes to migrate in a direction perpendicular to the surface of the high-purity silicon wafer, inhibiting lateral diffusion, thereby performing high-speed and high-quality etching of the high-purity silicon wafer at the evenly distributed metal catalyst nanoparticles, ultimately obtaining a silicon nanowire material with uniform distribution, high morphological consistency, high specific surface area, and excellent electrochemical properties.

[0030] In addition, the embodiments of the present disclosure use discarded photovoltaic silicon panels as silicon sources, which is conducive to the recycling of resources and reduces the pollution of discarded photovoltaic silicon panels to the environment.

[0031] Figure 2 This is a flow chart of another method for preparing silicon nanowire materials provided by an embodiment of the present disclosure. Figure 2 As shown, the preparation method comprises:

[0032] In step S201, organic impurities, metal impurities and oxide impurities in the discarded photovoltaic silicon panels are removed by heating treatment and wet treatment to obtain high-purity silicon wafers.

[0033] Exemplarily, the mass proportion of silicon in discarded photovoltaic silicon panels is about 5%.

[0034] For example, waste photovoltaic silicon panels include a cover plate, silicon wafers, adhesive, metal layer, oxide layer, backplane, etc. Heat treatment and wet treatment can effectively remove various impurities on the silicon wafers, thereby purifying the silicon in the waste photovoltaic silicon panels.

[0035] Optionally, step S201 may include the following steps:

[0036] The first step is to heat the discarded photovoltaic silicon panels, remove the cover plate, adhesive and back plate, and obtain the bare silicon panels.

[0037] For example, discarded photovoltaic silicon panels can be placed in a muffle furnace and subjected to high-temperature treatment at 440°C for 60 minutes to remove the cover plate, adhesive, and back plate. The temperature of the muffle furnace can be increased by 15°C per minute until the temperature reaches 440°C.

[0038] It should be noted that after this step, some metal impurities and oxide impurities are still attached to the exposed silicon plate.

[0039] In the second step, the exposed silicon plate is wet cleaned to remove metal impurities and oxide impurities.

[0040] For example, Al impurities can be removed by wet treatment with 18wt% to 24wt% HCL for 5min to 10min; then Ag impurities can be removed by wet treatment with 30wt% HNO3 at 50°C for 8min to 10min, and the treated liquid can be collected and separated and purified, and can be used as a raw material for the subsequent deposition solution; then the anti-reflection coating (ARC) can be removed by wet treatment with 20wt% to 30wt% HF at room temperature for 10min to 15min.

[0041] Here, separating and purifying the treatment liquid in the process of removing Ag impurities and using it as a raw material for the subsequent deposition solution can reduce the preparation cost of the silicon nanowire material.

[0042] The third step is to clean the silicon wafer after removing metal impurities and oxide impurities to obtain high-purity silicon wafers.

[0043] For example, the wafer can be first ultrasonically cleaned with pure water, then ultrasonically cleaned with acetone and rinsed with pure water for 30 seconds, then ultrasonically cleaned with ethanol and rinsed with pure water for 30 seconds. Finally, the wafer can be cleaned with a solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heated to 80°C in a water bath, and rinsed with pure water for 30 seconds to obtain a high-purity silicon wafer. After these multiple wet cleaning steps, the remaining lattice defects and active sites on the surface of the silicon wafer are uniformly distributed, providing a uniform substrate for the subsequent reduction nucleation of metal catalyst ions, which facilitates the orderly nucleation and growth of metal catalyst nanoparticles.

[0044] Illustratively, the purity of the high-purity silicon wafer is greater than 99.9%.

[0045] In step S202, a high-purity silicon wafer is placed in a deposition solution, and metal catalyst nanoparticles are deposited on the surface of the high-purity silicon wafer under the action of an electric field.

[0046] Optionally, the deposition solution includes a mixed solution of HF with a concentration of 4 mol / L to 5.5 mol / L and AgNO3 with a concentration of 0.02 mol / L to 0.05 mol / L. In this way, under the action of the electric field, the Ag in the deposition solution + A reduction reaction can be generated to deposit uniform Ag catalyst nanoparticles on the surface of the high-purity silicon wafer. The Ag catalyst nanoparticles can catalyze the etching of the high-purity silicon wafer in the subsequent steps to obtain silicon nanowire materials.+ The resulting reduction reaction can be represented by the following chemical reaction formula (1):

[0047] Ag + +e-→Ag (1)

[0048] For example, the concentration of HF in the deposition solution may be 4 mol / L, 4.5 mol / L, 5 mol / L, or 5.5 mol / L.

[0049] For example, the concentration of AgNO 3 in the deposition solution may be 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, or 0.05 mol / L, etc.

[0050] Optionally, step S202 may include: using a high-purity silicon wafer as a cathode and a platinum electrode as an anode and immersing them in a deposition solution, applying a current density of 0.1 mA / cm 2 Up to 1mA / cm 2 A constant current of 0.5 V or a constant voltage of 0.5 V to 2 V is applied to deposit metal catalyst nanoparticles on the surface of the high-purity silicon wafer. Under the action of this electric field, the metal catalyst nanoparticles can be deposited more evenly on the surface of the high-purity silicon wafer.

[0051] For example, the current density of the constant current during the deposition process can be 0.1 mA / cm 2 , 0.5mA / cm 2 or 1mA / cm 2 wait.

[0052] For example, the constant voltage during the deposition process may be 0.5V, 1V, 1.5V, or 2V.

[0053] Optionally, the duration of deposition under the action of the electric field is 3 to 5 minutes, which can further improve the uniformity of the distribution of the metal catalyst nanoparticles.

[0054] For example, the duration of deposition under the action of the electric field may be 3 minutes, 4 minutes, or 5 minutes.

[0055] In step S203, the high-purity silicon wafer is placed in an etching solution, and the high-purity silicon wafer is etched under the action of an electric field.

[0056] Optionally, the etching solution includes a mixture of 4.8 mol / L HF and 5% to 30% H2O2. Thus, high-purity silicon wafers can be etched at a high rate and with high quality under the action of an electric field, thereby obtaining silicon nanowire materials with highly consistent morphology.

[0057] Optionally, step S203 may include: using a high-purity silicon wafer as an anode and a platinum electrode as a cathode and immersing them in an etching solution, applying a current density of 0.5 mA / cm 2 Up to 2mA / cm 2 High-purity silicon wafers are etched at a constant current of 0.5V or a constant voltage of 0.5V to 2V. Under the action of this electric field, the etching rate and etching quality can be improved.

[0058] In the above etching solution, the reaction at the anode can be expressed by the following chemical reaction formula (2):

[0059] Si+6HF→H2SiF6+2H + +2e - (2)

[0060] The cathode reaction can be expressed by the following chemical reaction formula (3):

[0061] H2O2+2H + +2e - →2H2O (3)

[0062] Among them, the holes generated by the anode (H + ) will migrate in a direction perpendicular to the surface of the high-purity silicon wafer under the drive of the electric field, preferentially etching the silicon around the metal catalyst nanoparticles to form a vertical etching channel.

[0063] For example, the current density of the constant current during the etching process can be 0.5 mA / cm 2 , 1mA / cm 2 , 1.5mA / cm 2 or 2mA / cm 2 wait.

[0064] For example, the constant voltage during the etching process may be 0.5V, 1V, 1.5V, or 2V.

[0065] Optionally, the duration of etching the high-purity silicon wafer under the action of the electric field is 20 minutes to 40 minutes, which can ensure that the quality of the silicon nanowire material obtained by etching is good.

[0066] For example, the duration of etching the high-purity silicon wafer under the action of the electric field may be 20 minutes, 30 minutes, or 40 minutes.

[0067] In the embodiments of the present disclosure, the size and etching depth of the silicon nanowires can be precisely controlled by adjusting the current or voltage.

[0068] Optionally, after completing step S203, the preparation method may further include:

[0069] In step S204, the etched high-purity silicon wafer is cleaned and dried to obtain silicon nanowire material.

[0070] The quality of the obtained silicon nanowire material can be ensured to be good by cleaning and drying.

[0071] For example, concentrated nitric acid may be used for cleaning for 5 to 10 minutes to remove Ag catalyst nanoparticles; pure water may be used for ultrasonic cleaning for 5 minutes; and finally, vacuum drying may be performed at 60° C. for 2 hours to obtain silicon nanowire material.

[0072] Figure 3 Schematic diagram of the morphology of a silicon nanowire material provided by the embodiment of the present disclosure. Figure 3 As shown, the silicon nanowire material prepared by the preparation method of the embodiment of the present disclosure is observed under a scanning electron microscope (SEM), which has uniform distribution, consistent diameter, high morphology consistency and high specific surface area.

[0073] Figure 4 This is a schematic diagram of the first 100 cycle performance and corresponding coulombic efficiency of a lithium battery with a negative electrode made of silicon nanowire material provided by an embodiment of the present disclosure. Figure 4 As shown, the negative electrode of a lithium battery was made of the silicon nanowire material prepared by the preparation method of the embodiment of the present disclosure, and a charge and discharge test was performed. The test procedure was 1000 mA / g. It can be seen that after 100 cycles, the coulombic efficiency of the lithium battery was still high and the specific capacity decay was small. Therefore, the electrochemical performance of the silicon nanowire material obtained by the preparation method of the embodiment of the present disclosure is excellent.

[0074] The preparation method using the embodiments of the present disclosure will be described below in conjunction with different embodiments.

[0075] Example 1:

[0076] (1) The discarded photovoltaic silicon panels were placed in a muffle furnace and heated at a heating rate of 15°C per minute to 440°C. The panels were treated at high temperature for 60 minutes to remove organic impurities such as the cover plate, adhesive, back plate, and adhesive to obtain a bare silicon panel.

[0077] (2) Immersing the silicon plate obtained in step (1) in 20wt% HCL and wet-treating it at room temperature for 8 minutes to remove Al impurities; then immersing the treated silicon plate in 30wt% HNO3 and wet-treating it at 50°C for 9 minutes to remove Ag impurities; then immersing the silicon plate in 25wt% HF and wet-treating it at room temperature for 12 minutes to remove ARC; finally, cleaning the silicon wafer: first, ultrasonic cleaning with pure water; then ultrasonic cleaning with acetone, rinsing with pure water for 30 seconds; then ultrasonic cleaning with ethanol, rinsing with pure water for 30 seconds; finally, using a washing solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heating the water bath to 80°C to clean the silicon wafer, and rinsing with pure water for 30 seconds to obtain a high-purity silicon wafer.

[0078] (3) Prepare a mixed solution of 4.5 mol / L HF and 0.03 mol / L AgNO3 as the deposition solution, use a high-purity silicon wafer as the cathode, and immerse the platinum electrode as the anode in the deposition solution. Apply a current density of 0.5 mA / cm 2 A constant current of 100 nm was applied for 4 min to deposit Ag catalyst nanoparticles on the surface of the high-purity silicon wafer. A mixed solution of 4.8 mol / L HF and 10% H2O2 was prepared as an etching solution. The high-purity silicon wafer was used as the anode and the platinum electrode was used as the cathode and immersed in the etching solution. A current density of 1 mA / cm 2 The constant current lasts for 30 minutes to etch high-purity silicon wafers.

[0079] (4) Immerse the high-purity silicon wafer etched in step (3) in concentrated nitric acid and wash it at room temperature for 8 minutes to dissolve the Ag catalyst nanoparticles; then use pure water ultrasonic cleaning for 5 minutes; finally, vacuum dry it at 60°C for 2 hours to obtain silicon nanowire material.

[0080] Example 2:

[0081] (1) The discarded photovoltaic silicon panels were placed in a muffle furnace and heated at a heating rate of 15°C per minute to 440°C. The panels were treated at high temperature for 60 minutes to remove organic impurities such as the cover plate, adhesive, back plate, and adhesive to obtain a bare silicon panel.

[0082] (2) Immersing the silicon plate obtained in step (1) in 18 wt% HCL and wet-treating it at room temperature for 10 min to remove Al impurities; then immersing the treated silicon plate in 30 wt% HNO3 and wet-treating it at 50°C for 8 min to remove Ag impurities; then immersing the silicon plate in 20 wt% HF and wet-treating it at room temperature for 15 min to remove ARC; finally, cleaning the silicon wafer: first, ultrasonically cleaning it with pure water; then, ultrasonically cleaning it with acetone, and rinsing it with pure water for 30 s; then, ultrasonically cleaning it with ethanol, and rinsing it with pure water for 30 s; finally, cleaning the silicon wafer with a washing solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heating the water bath to 80°C, and rinsing it with pure water for 30 s to obtain a high-purity silicon wafer.

[0083] (3) A mixed solution of 4 mol / L HF and 0.02 mol / L AgNO3 was prepared as a deposition solution, a high-purity silicon wafer was used as a cathode, a platinum electrode was used as an anode and immersed in the deposition solution, a constant voltage of 1 V was applied for 5 min, and Ag catalyst nanoparticles were deposited on the surface of the high-purity silicon wafer; a mixed solution of 4.8 mol / L HF and 5% H2O2 was prepared as an etching solution, a high-purity silicon wafer was used as an anode, a platinum electrode was used as a cathode and immersed in the etching solution, a constant voltage of 1.5 V was applied for 25 min, and the high-purity silicon wafer was etched.

[0084] (4) Immerse the high-purity silicon wafer etched in step (3) in concentrated nitric acid and wash it at room temperature for 8 minutes to dissolve the Ag catalyst nanoparticles; then use pure water ultrasonic cleaning for 5 minutes; finally, vacuum dry it at 60°C for 2 hours to obtain silicon nanowire material.

[0085] Example 3:

[0086] (1) The discarded photovoltaic silicon panels were placed in a muffle furnace and heated at a heating rate of 15°C per minute to 440°C. The panels were treated at high temperature for 60 minutes to remove organic impurities such as the cover plate, adhesive, back plate, and adhesive to obtain a bare silicon panel.

[0087] (2) Immersing the silicon plate obtained in step (1) in 24 wt% HCL and wet-treating it at room temperature for 5 min to remove Al impurities; then immersing the treated silicon plate in 30 wt% HNO3 and wet-treating it at 50°C for 10 min to remove Ag impurities; then immersing the silicon plate in 30 wt% HF and wet-treating it at room temperature for 10 min to remove ARC; finally, cleaning the silicon wafer: first, ultrasonic cleaning with pure water; then ultrasonic cleaning with acetone, rinsing with pure water for 30 s; then ultrasonic cleaning with ethanol, rinsing with pure water for 30 s; finally, cleaning the silicon wafer with a washing solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heating the water bath to 80°C, and rinsing with pure water for 30 s to obtain a high-purity silicon wafer.

[0088] (3) Prepare a mixed solution of 5.5 mol / L HF and 0.05 mol / L AgNO3 as the deposition solution, use a high-purity silicon wafer as the cathode, and immerse the platinum electrode as the anode in the deposition solution. Apply a current density of 0.8 mA / cm 2 A constant current of 1.5 mA / cm was applied for 3 min to deposit Ag catalyst nanoparticles on the surface of the high-purity silicon wafer. A mixed solution of 4.8 mol / L HF and 20% H2O2 was prepared as the etching solution. The high-purity silicon wafer was used as the anode and the platinum electrode was used as the cathode and immersed in the etching solution. The current density was 1.5 mA / cm 2 The constant current lasts for 35 minutes to etch high-purity silicon wafers.

[0089] (4) Immerse the high-purity silicon wafer etched in step (3) in concentrated nitric acid and wash it at room temperature for 10 minutes to dissolve the Ag catalyst nanoparticles; then use pure water ultrasonic cleaning for 5 minutes; finally, vacuum dry it at 60°C for 2 hours to obtain silicon nanowire material.

[0090] Example 4:

[0091] (1) The discarded photovoltaic silicon panels were placed in a muffle furnace and heated at a heating rate of 15°C per minute to 440°C. The panels were treated at high temperature for 60 minutes to remove organic impurities such as the cover plate, adhesive, back plate, and adhesive to obtain a bare silicon panel.

[0092] (2) Immersing the silicon plate obtained in step (1) in 22 wt% HCL and wet-treating it at room temperature for 7 min to remove Al impurities; then immersing the treated silicon plate in 30 wt% HNO3 and wet-treating it at 50°C for 9 min to remove Ag impurities; then immersing the silicon plate in 28 wt% HF and wet-treating it at room temperature for 13 min to remove ARC; finally, cleaning the silicon wafer: first, ultrasonic cleaning with pure water; then ultrasonic cleaning with acetone, rinsing with pure water for 30 s; then ultrasonic cleaning with ethanol, rinsing with pure water for 30 s; finally, cleaning the silicon wafer with a washing solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heating the water bath to 80°C, and rinsing with pure water for 30 s to obtain a high-purity silicon wafer.

[0093] (3) Prepare a mixed solution of 4.8 mol / L HF and 0.04 mol / L AgNO3 as the deposition solution, use a high-purity silicon wafer as the cathode, and immerse the platinum electrode as the anode in the deposition solution. Apply a current density of 0.6 mA / cm 2A constant current of 1.8V was applied for 5 minutes to deposit Ag catalyst nanoparticles on the surface of the high-purity silicon wafer; a mixed solution of 4.8 mol / L HF and 15% H2O2 was prepared as the etching solution, the high-purity silicon wafer was used as the anode, the platinum electrode was used as the cathode and immersed in the etching solution, and a constant voltage of 1.8V was applied for 28 minutes to etch the high-purity silicon wafer.

[0094] (4) Immerse the high-purity silicon wafer etched in step (3) in concentrated nitric acid and wash it at room temperature for 8 minutes to dissolve the Ag catalyst nanoparticles; then use pure water ultrasonic cleaning for 5 minutes; finally, vacuum dry it at 60°C for 2 hours to obtain silicon nanowire material.

[0095] Embodiment 5:

[0096] (1) The discarded photovoltaic silicon panels were placed in a muffle furnace and heated at a heating rate of 15°C per minute to 440°C. The panels were treated at high temperature for 60 minutes to remove organic impurities such as the cover plate, adhesive, back plate, and adhesive to obtain a bare silicon panel.

[0097] (2) Immersing the silicon plate obtained in step (1) in 20wt% HCL and wet-treating it at room temperature for 9 minutes to remove Al impurities; then immersing the treated silicon plate in 30wt% HNO3 and wet-treating it at 50°C for 8 minutes to remove Ag impurities; then immersing the silicon plate in 25wt% HF and wet-treating it at room temperature for 14 minutes to remove ARC; finally, cleaning the silicon wafer: first, ultrasonic cleaning with pure water; then ultrasonic cleaning with acetone, rinsing with pure water for 30 seconds; then ultrasonic cleaning with ethanol, rinsing with pure water for 30 seconds; finally, using a washing solution of H2O2, NH3·H2O, and pure water in a volume ratio of 1:1:5, heating the water bath to 80°C to clean the silicon wafer, and rinsing with pure water for 30 seconds to obtain a high-purity silicon wafer.

[0098] (3) A mixed solution of 4.2 mol / L HF and 0.03 mol / L AgNO3 was prepared as a deposition solution, a high-purity silicon wafer was used as a cathode, a platinum electrode was used as an anode and immersed in the deposition solution, a constant voltage of 1.2 V was applied for 5 min, and Ag catalyst nanoparticles were deposited on the surface of the high-purity silicon wafer; a mixed solution of 4.8 mol / L HF and 25% H2O2 was prepared as an etching solution, a high-purity silicon wafer was used as an anode, a platinum electrode was used as a cathode and immersed in the etching solution, and a current density of 1.2 mA / cm was applied. 2 The constant current lasts for 32 minutes to etch high-purity silicon wafers.

[0099] (4) Immerse the high-purity silicon wafer etched in step (3) in concentrated nitric acid and wash it at room temperature for 9 minutes to dissolve the Ag catalyst nanoparticles; then use pure water ultrasonic cleaning for 5 minutes; finally, vacuum dry it at 60°C for 2 hours to obtain silicon nanowire material.

[0100] The present disclosure also provides a silicon nanowire material. The silicon nanowire material is Figure 1 or Figure 2 Prepared according to the preparation method shown.

[0101] The above description is merely an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A method for preparing a silicon nanowire material, characterized in that: include: Pre-process discarded photovoltaic silicon panels to obtain high-purity silicon wafers; placing the high-purity silicon wafer in a deposition solution, and depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafer under the action of an electric field; The high-purity silicon wafer is placed in an etching solution, and the high-purity silicon wafer is etched under the action of an electric field to obtain the silicon nanowire material.

2. The preparation method according to claim 1, characterized in that The step of depositing metal catalyst nanoparticles on the surface of the high-purity silicon wafer under the action of an electric field comprises: The high-purity silicon wafer was used as cathode and the platinum electrode was used as anode and immersed in the deposition solution, and a current density of 0.1 mA / cm was applied. 2 Up to 1mA / cm 2 The metal catalyst nanoparticles are deposited on the surface of the high-purity silicon wafer at a constant current of 0.5V or a constant voltage of 0.5V to 2V.

3. The preparation method according to claim 2, characterized in that The duration of deposition under the action of the electric field is 3 to 5 minutes.

4. The preparation method according to claim 1, characterized in that The etching of the high-purity silicon wafer under the action of an electric field comprises: The high-purity silicon wafer was used as the anode and the platinum electrode was used as the cathode and immersed in the etching solution, and a current density of 0.5 mA / cm was applied. 2 Up to 2mA / cm 2 The high-purity silicon wafer is etched using a constant current of 0.5V or a constant voltage of 0.5V to 2V.

5. The preparation method according to claim 4, characterized in that The duration of etching the high-purity silicon wafer under the action of the electric field is 20 minutes to 40 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that The deposition solution includes a mixed solution of HF with a concentration of 4 mol / L to 5.5 mol / L and AgNO 3 with a concentration of 0.02 mol / L to 0.05 mol / L.

7. The preparation method according to any one of claims 1 to 5, characterized in that The etching solution includes a mixed solution of HF with a concentration of 4.8 mol / L and H2O2 with a concentration of 5% to 30%.

8. The preparation method according to any one of claims 1 to 5, characterized in that The pre-processing of discarded photovoltaic silicon panels includes: Organic impurities, metal impurities and oxide impurities in the waste photovoltaic silicon panels are removed through heating treatment and wet treatment.

9. The preparation method according to any one of claims 1 to 5, characterized in that The method further comprises: The etched high-purity silicon wafer is cleaned and dried.

10. A silicon nanowire material, characterized in that: The silicon nanowire material is prepared by the preparation method according to any one of claims 1 to 9.

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