Self-healing super-hydrophobic composite nano-photocatalyst, and preparation method and application thereof

Abstract

This invention provides a self-healing superhydrophobic composite photocatalyst, its preparation method, and its application, belonging to the field of composite material technology. The self-healing superhydrophobic composite photocatalyst provided by this invention includes a substrate, a nano-flower-like ZnO / CuS composite material grown on the surface of the substrate, and a superhydrophobic layer modified on the surface of the nano-flower-like ZnO / CuS composite material; the superhydrophobic layer is a composite coating obtained by curing a waxy material, a hydrophobic compound, and a curing agent. This invention constructs a nano-flower-like ZnO / CuS composite material on a substrate, improving the photocatalytic activity of the heterostructure. Modifying the surface of the nano-flower-like ZnO / CuS composite material with a superhydrophobic layer enhances the hydrophobicity of the photocatalyst; the waxy material provides self-healing capabilities and also makes the superhydrophobic properties of the photocatalyst more stable and durable during application.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a self-healing superhydrophobic composite nanocatalyst, its preparation method, and its application. Background Technology

[0002] In recent years, water pollution has become a major environmental concern globally. Photocatalytic degradation, which can degrade various organic pollutants into harmless products (e.g., CO2, H2O), has proven to be a highly efficient, green, and promising wastewater treatment technology. However, the narrow visible light absorption range and high recombination efficiency of photogenerated carriers in semiconductor photocatalysts result in low light utilization efficiency, significantly limiting their photocatalytic activity. To improve light utilization efficiency, infrared light, which accounts for more than 50% of sunlight, is receiving increasing attention. Recently, the thermal effect of infrared light has become a hot research topic in the field of catalysis. Photothermal-assisted photocatalysis, as a novel catalytic technology, can simultaneously utilize both light and heat energy.

[0003] However, common semiconductor photocatalysts are hydrophilic materials, making them susceptible to contamination by microorganisms and mud in water when used for water pollution treatment. They are also easily damaged by oxidants, corrosive liquids, and ultraviolet radiation. Hydrophobic composite materials, on the other hand, can reduce the retention and contact of water, electrolytes, and hydrophilic contaminants on the surface of the composite material, thereby reducing the contamination and corrosion of the photocatalyst.

[0004] Current research involves first creating a superhydrophobic substrate and then preparing photocatalytic nanocomposites on the hydrophobic substrate. While this can improve the hydrophobicity and lifespan of the photocatalyst to some extent, its ability to protect the photocatalyst's durability is weak during practical use as the superhydrophobic substrate breaks down. Summary of the Invention

[0005] The purpose of this invention is to provide a self-healing superhydrophobic composite nanocatalyst, its preparation method, and its application. The photocatalyst provided by this invention has durable superhydrophobic protection and excellent photocatalytic activity.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a self-healing superhydrophobic composite nanophotocatalyst, comprising a substrate, a nanoflower-like ZnO / CuS composite material grown on the surface of the substrate, and a superhydrophobic layer modified on the surface of the nanoflower-like ZnO / CuS composite material; the superhydrophobic layer is a composite coating obtained by curing a waxy material, a hydrophobic compound, and a curing agent.

[0007] Preferably, the waxy material includes one or more of beeswax, paraffin wax, and stearic acid.

[0008] Preferably, the hydrophobic compound includes an organosilicon compound or a polyurethane.

[0009] This invention also provides a method for preparing the self-healing superhydrophobic composite nanocatalyst described in the above technical solution, comprising the following steps: (1) A zinc seed layer is grown on the substrate surface to obtain a substrate with a zinc seed layer; (2) The substrate with the zinc seed layer obtained in step (1) is immersed in a soluble zinc salt solution and subjected to a hydrothermal reaction to obtain a substrate with a ZnO nanostructure. The soluble zinc salt solution is composed of soluble zinc salt, KCl, and ethylenediamine; (3) The substrate with ZnO nanostructure obtained in step (2) is used to obtain a substrate with ZnO / CuS composite material with nanoflower-like structure by continuous ion layer adsorption method. The method of the continuous ion layer adsorption method includes: first impregnating the substrate on which the ZnO nanostructure is grown in a copper cation solution, first cleaning it, then impregnating it in a sulfur anion solution, and then cleaning it again; the molar ratio of copper ions in the copper cation solution to sulfur ions in the sulfur anion solution is 1:1. (4) The substrate of the ZnO / CuS composite material with grown nanoflowers obtained in step (3) is impregnated in a superhydrophobic modified solution for the third time, and then cured to obtain a self-healing superhydrophobic composite nanophotocatalyst. The superhydrophobic modified solution comprises wax material, hydrophobic compound, curing agent and solvent.

[0010] Preferably, in step (2), the concentration of soluble zinc salt in the soluble zinc salt solution is 0.01~0.075 mol / L, and the concentration of KCl is 0.05~0.15 mol / L.

[0011] Preferably, the temperature of the hydrothermal reaction in step (2) is 60~150℃, and the time of the hydrothermal reaction is 0.5~3h.

[0012] Preferably, the time for the first immersion and the second immersion in step (3) is 10 to 60 minutes independently.

[0013] Preferably, the number of cycles in the continuous ion layer adsorption method in step (3) is 2 to 5.

[0014] Preferably, the concentration of wax material in the superhydrophobic modification solution in step (4) is 0.005~0.03 g / mL, and the concentration of hydrophobic compound is 0.01~0.06 g / mL.

[0015] The present invention also provides the application of the self-healing superhydrophobic composite nanophotocatalyst described in the above technical solution or the self-healing superhydrophobic composite nanophotocatalyst prepared by the preparation method described in the above technical solution in the treatment of organic wastewater.

[0016] This invention provides a self-healing superhydrophobic composite photocatalyst, comprising a substrate, a nano-flower-like ZnO / CuS composite material grown on the surface of the substrate, and a superhydrophobic layer modified on the surface of the nano-flower-like ZnO / CuS composite material; the superhydrophobic layer is a composite coating obtained by curing a waxy material, a hydrophobic compound, and a curing agent. This invention constructs a nano-flower-like ZnO / CuS composite material on a substrate. The ZnO / CuS composite material is a ZnO / CuS heterostructure. The inclusion of CuS expands the light absorption range of ZnO, allowing it to utilize sunlight more effectively. Under infrared light irradiation, ZnO / CuS exhibits significant photothermal behavior and higher light absorption, thus improving the photocatalytic activity of the heterostructure. The photocatalyst provided by this invention modifies the surface of a nano-flower-like ZnO / CuS composite material with a superhydrophobic layer. The hydrophobic compound, after curing, enhances the hydrophobicity of the photocatalyst. The introduction of a waxy material provides self-healing capabilities by migrating and repairing damage to the superhydrophobicity and enhancing the corrosion resistance to O2 plasma. It also makes the superhydrophobic properties of the photocatalyst more stable and durable during application. Integrating the superhydrophobic layer into the photocatalyst improves its mechanical strength and lifespan. The results of the examples show that the self-healing superhydrophobic composite nano-photocatalyst provided by this invention exhibits durable superhydrophobic protection and excellent photocatalytic activity. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation method of the self-healing superhydrophobic composite nanocatalyst of the present invention; Figure 2 These are FESEM images of the ZnO nanostructures under different reaction temperatures according to the present invention. Figure 3 The UV-Vis absorption spectra of the ZnO nanostructure under different reaction temperature conditions and the corresponding band gap diagram of the ZnO nanostructure at 100℃ are shown in this invention. Figure 4 The XRD patterns of ZnO nanostructures under different reaction solution concentrations according to the present invention are shown below. Figure 5 These are FESEM images of ZnO nanostructures under different reaction solution concentrations according to the present invention. Figure 6 The light absorption results of the ZnO nanostructure of this invention at different concentrations and the band gap of the sample with a reaction concentration of 1.50C are shown. Figure 7 These are FESEM images of the nanostructures obtained under different sulfide composite conditions according to the present invention. Figure 8 The UV-Vis absorption spectra of the nanostructures under different sulfide semiconductor composite conditions of this invention are shown. Figure 9 The photoluminescence spectra of different sulfides used in this invention at room temperature; Figure 10 The photocurrent response curves of the nanostructure under different sulfide composite conditions of the present invention are shown. Figure 11 XPS spectra of the ZnO / CuS composite nanostructure of this invention; Figure 12 This is a TEM image of the ZnO / CuS composite nanostructure of the present invention; Figure 13 The infrared vibrational spectrum of the superhydrophobic modified ZnO / CuS composite nanostructure in Example 5 of this invention; Figure 14 The images show FESEM images of different composite nanostructures of the present invention and the contact angle results of the composite nanostructures before and after Plasma treatment. Figure 15 These are the superhydrophobic stability cycling test results for the two composite nanostructures in Example 1 and Comparative Example 4 of this invention. Figure 16 This describes the self-healing process of the BP-PDMS superhydrophobic coating prepared in Example 1 of the present invention. Figure 17 The temperature changes of ZnO, ZnO / CuS and BP-ZnO / CuS under 808nm infrared light irradiation according to the present invention; Figure 18 The images show the ultraviolet-visible absorption spectra of different nanostructures of this invention under 808nm infrared light irradiation. Figure 19 This is the photothermal conversion mechanism of the present invention; Figure 20 These are the experimental results of photodegradation of MB in this invention; Figure 21 The photocatalytic degradation reaction mechanism of the ZnO / CuS composite nanostructure of this invention is described. Detailed Implementation

[0018] This invention provides a self-healing superhydrophobic composite nanophotocatalyst, comprising a substrate, a nanoflower-like ZnO / CuS composite material grown on the surface of the substrate, and a superhydrophobic layer modified on the surface of the nanoflower-like ZnO / CuS composite material; the superhydrophobic layer is a composite coating obtained by curing a waxy material, a hydrophobic compound, and a curing agent.

[0019] The self-healing superhydrophobic composite nanocatalyst provided by the present invention includes a substrate.

[0020] This invention does not have any particular limitation on the material of the substrate; any substrate commonly used in photocatalysts can be used. In this invention, the substrate preferably includes FTO, ITO, silicon wafers, or glass slides.

[0021] The self-healing superhydrophobic composite photocatalyst provided by the present invention also includes a nano-flower-like ZnO / CuS composite material grown on the surface of the substrate.

[0022] In this invention, the nanoflower-like ZnO / CuS composite material is preferably a three-dimensional radial flower-like ZnO / CuS heterostructure. The nanoflower-like ZnO / CuS composite material provided by this invention has abundant active sites, and the inclusion of CuS expands the light absorption range of ZnO, allowing it to utilize sunlight more effectively. Under infrared illumination, ZnO / CuS exhibits significant photothermal behavior and higher light absorption, thus improving the photocatalytic activity of the heterostructure.

[0023] In this invention, the molar ratio of ZnO to CuS in the nanoflower-like ZnO / CuS composite material is preferably 1:1 to 1.5. As an embodiment of this invention, the molar ratio of ZnO to CuS in the nanoflower-like ZnO / CuS composite material can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5.

[0024] The self-healing superhydrophobic composite nanophotocatalyst provided by the present invention further includes a superhydrophobic layer modified on the surface of the nanoflower-like ZnO / CuS composite material.

[0025] In this invention, the superhydrophobic layer is a composite coating obtained by curing wax material, hydrophobic compound and curing agent.

[0026] In this invention, the waxy material preferably includes one or more of beeswax, paraffin wax, and stearic acid. By introducing a waxy material, this invention provides self-healing capabilities through the migration and repair of damage to superhydrophobicity and by enhancing the corrosion resistance to O2 plasma.

[0027] In this invention, the hydrophobic compound preferably comprises an organosilicon compound or a polyurethane. The organosilicon compound preferably comprises a long-chain alkylsilane or polydimethylsiloxane (PDMS); the long-chain alkylsilane preferably comprises dodecyltrimethoxysilane, hexadecyltrimethoxysilane, or octadecyltrimethoxysilane. This invention utilizes organosilicon compounds or polyurethane to prepare a superhydrophobic layer, enabling the photocatalyst to possess excellent hydrophobicity.

[0028] In this invention, when the hydrophobic compound is PDMS, the PDMS is preferably vinyl-terminated PDMS, and the curing agent is preferably a platinum catalyst; when the hydrophobic compound is polyurethane, the curing agent is preferably an isocyanate-based curing agent. In this invention, when the hydrophobic compound is a long-chain alkylsilane, a curing agent may not be added. In this invention, the curing agent serves to accelerate the reaction rate; therefore, this invention does not have specific limitations on the type and source of the curing agent, and conventional commercially available products can be used.

[0029] In this invention, the mass ratio of the waxy material to the hydrophobic compound is preferably 1:1 to 2, more preferably 1:1.5.

[0030] This invention also provides a method for preparing the self-healing superhydrophobic composite nanocatalyst described in the above technical solution, comprising the following steps: (1) A zinc seed layer is grown on the substrate surface to obtain a substrate with a zinc seed layer; (2) The substrate with the zinc seed layer obtained in step (1) is immersed in a soluble zinc salt solution and subjected to a hydrothermal reaction to obtain a substrate with a ZnO nanostructure. The soluble zinc salt solution is composed of soluble zinc salt, KCl, and ethylenediamine; (3) The substrate with ZnO nanostructure obtained in step (2) is used to obtain a substrate with ZnO / CuS composite material with nanoflower-like structure by continuous ion layer adsorption method. The method of the continuous ion layer adsorption method includes: first impregnating the substrate on which the ZnO nanostructure is grown in a copper cation solution, first cleaning it, then impregnating it in a sulfur anion solution, and then cleaning it again; the molar ratio of copper ions in the copper cation solution to sulfur ions in the sulfur anion solution is 1:1. (4) The substrate of the ZnO / CuS composite material with grown nanoflowers obtained in step (3) is impregnated in a superhydrophobic modified solution for the third time, and then cured to obtain a self-healing superhydrophobic composite nanophotocatalyst. The superhydrophobic modified solution comprises wax material, hydrophobic compound, curing agent and solvent.

[0031] This invention grows a zinc seed layer on the surface of a substrate to obtain a substrate with a zinc seed layer.

[0032] In this invention, the method for growing a zinc seed layer on a substrate surface preferably includes: The substrate is pretreated to obtain a pretreated substrate; The pretreated substrate was immersed in a zinc ion ethanol solution, then dried. The immersion and drying processes were repeated, followed by annealing to obtain a substrate for growing a zinc seed layer.

[0033] The present invention preferably pre-treats the substrate to obtain a pre-treated substrate. In this invention, the substrate preferably includes FTO, ITO, silicon wafer or glass slide.

[0034] In this invention, the pretreatment method preferably includes: ultrasonically cleaning the substrate sequentially in NaOH solution, ethanol and deionized water, and then drying it for later use.

[0035] In this invention, the concentration of the NaOH solution is preferably 0.05~0.2 mol / L, more preferably 0.1 mol / L.

[0036] In this invention, the ultrasonic cleaning time is preferably 5 to 30 minutes, more preferably 10 minutes.

[0037] In this invention, the drying temperature is preferably 40~90℃, more preferably 60℃.

[0038] After obtaining the pretreated substrate, the present invention preferably soaks the pretreated substrate in a zinc ion ethanol solution, removes it and dries it, repeats the soaking and drying process, and then performs annealing treatment to obtain a substrate for growing zinc seed layers.

[0039] In this invention, the zinc ion ethanol solution is preferably a Zn(CH3COO)2 ethanol solution or a zinc nitrate ethanol solution, and the concentration of the zinc ion ethanol solution is preferably 2~10 mmol / L, more preferably 5~8 mmol / L.

[0040] In this invention, the soaking time is preferably 5-60 seconds, more preferably 15-30 seconds.

[0041] In this invention, the soaking treatment is preferably followed by rinsing with ethanol.

[0042] In this invention, the drying is preferably argon drying.

[0043] In this invention, the repeated soaking and drying processes are preferably repeated 2 to 5 times, more preferably 3 times.

[0044] In this invention, the annealing temperature is preferably 400~700℃, more preferably 400~600℃; the holding time for the annealing is preferably 30~180min, more preferably 60~120min. In this invention, the heating rate to the annealing temperature is preferably 1~5℃ / min, more preferably 2~5℃ / min. This invention, through annealing, enables the formation of a zinc seed layer on the substrate surface.

[0045] After obtaining the substrate with the zinc seed layer, the present invention immerses the substrate with the zinc seed layer in a soluble zinc salt solution and carries out a hydrothermal reaction to obtain a substrate with a ZnO nanostructure.

[0046] In this invention, the soluble zinc salt solution is composed of soluble zinc salt, KCl, and ethylenediamine. Preferably, the preparation method of the soluble zinc salt solution includes: mixing the soluble zinc salt, KCl, and ethylenediamine until clear, and stirring for 30 minutes.

[0047] In this invention, the soluble zinc salt in the soluble zinc salt solution preferably includes zinc nitrate or zinc acetate. In this invention, the concentration of the soluble zinc salt in the soluble zinc salt solution is preferably 0.01~0.075 mol / L, more preferably 0.01~0.025 mol / L, and even more preferably 0.015~0.02 mol / L.

[0048] In this invention, the concentration of KCl in the soluble zinc salt solution is preferably 0.05~0.15 mol / L, more preferably 0.09~0.12 mol / L.

[0049] In this invention, the preferred temperature for the hydrothermal reaction is 60-150°C, and the preferred reaction time is 0.5-3 hours. As an embodiment of this invention, the hydrothermal reaction temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, or 150°C; and the reaction time can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. This invention enables the growth of ZnO nanostructures on a substrate with a zinc seed layer via a hydrothermal reaction.

[0050] After obtaining the substrate with ZnO nanostructures, the present invention uses the continuous ion layer adsorption method to obtain the substrate with nanoflower-like ZnO / CuS composite material.

[0051] In this invention, the continuous ion layer adsorption method includes: first impregnating a substrate with a ZnO nanostructure in a copper-containing cation solution, first cleaning it, then impregnating it in a sulfur-containing anion solution, and then cleaning it again.

[0052] In this invention, the copper-containing cation solution preferably includes copper sulfate solution, copper nitrate solution, or copper acetate solution. In this invention, the concentration of the copper-containing cation solution is preferably 30-70 mmol / L, more preferably 50 mmol / L.

[0053] In this invention, the first impregnation time is preferably 10-60 min, more preferably 30-40 min. In this invention, the first impregnation is preferably performed at room temperature. This invention uses the first impregnation to adsorb copper-containing cations onto the surface of the substrate on which ZnO nanostructures are grown, forming a positively charged thin film.

[0054] In this invention, the reagent used for the first cleaning is preferably deionized water. This invention, through the first cleaning, can remove loosely adsorbed free copper ions, leaving a dense copper ion layer on the surface of the substrate on which the ZnO nanostructure is grown.

[0055] In this invention, the sulfur-containing anion solution preferably includes a Na₂S solution, a sodium sulfate solution, or a sodium thiosulfate solution. In this invention, the concentration of the sulfur-containing anion solution is preferably 30-70 mmol / L, more preferably 50 mmol / L.

[0056] In this invention, the second impregnation time is preferably 10-60 min, more preferably 30-40 min. In this invention, the second impregnation is preferably performed at room temperature. This invention uses the second impregnation to adsorb sulfur-containing anions onto the surface of the substrate on which the ZnO nanostructure is grown, forming a negatively charged thin film, and reacting to form a nanoflower-like ZnO / CuS composite material.

[0057] In this invention, the reagent used for the second cleaning is preferably deionized water. This invention, through the second cleaning process, can remove sulfur-containing anions that are not firmly adsorbed.

[0058] In this invention, the molar ratio of copper ions in the copper-containing cation solution to sulfur ions in the sulfur-containing anion solution is 1:1.

[0059] In this invention, the number of cycles in the continuous ion layer adsorption method is preferably 2 to 5 times, more preferably 3 to 4 times. By controlling the number of cycles in the continuous ion layer adsorption method within the above range, this invention can obtain a film of the desired thickness.

[0060] After obtaining the substrate of the ZnO / CuS composite material with grown nanoflowers, the present invention performs a third impregnation of the substrate of the ZnO / CuS composite material with grown nanoflowers in a superhydrophobic modified solution, and then performs a curing treatment to obtain a self-healing superhydrophobic composite nanophotocatalyst.

[0061] In this invention, the superhydrophobic modified solution comprises a waxy material, a hydrophobic compound, a curing agent, and a solvent. In this invention, the waxy material, hydrophobic compound, and curing agent are the same as those described in the above-mentioned technical solutions, and will not be repeated here.

[0062] In this invention, the curing agent preferably comprises 5-20% by mass of the PDMS hydrophobic compound. As an embodiment of this invention, the curing agent may comprise 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% by mass of the PDMS hydrophobic compound. By controlling the amount of curing agent within the above range, this invention enables the hydrophobic compound to be fully cured.

[0063] In this invention, the solvent is preferably tetrahydrofuran.

[0064] In this invention, the concentration of the waxy material in the superhydrophobic modified solution is preferably 0.005~0.03 g / mL. As an embodiment of this invention, the concentration of the waxy material in the superhydrophobic modified solution can be 0.005 g / mL, 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, 0.025 g / mL, or 0.03 g / mL. In this invention, the concentration of the hydrophobic compound in the superhydrophobic modified solution is preferably 0.01~0.06 g / mL. As an embodiment of this invention, the concentration of the hydrophobic compound in the superhydrophobic modified solution can be 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, 0.03 g / mL, 0.04 g / mL, 0.05 g / mL, or 0.06 g / mL.

[0065] In this invention, the third impregnation time is preferably 30-300 s. As an embodiment of this invention, the third impregnation time can be 30 s, 50 s, 100 s, 150 s, 200 s, 250 s, or 300 s. In this invention, the third impregnation is preferably performed at room temperature. Through the third impregnation, this invention enables the superhydrophobic modified solution to fully wet the nanoflower-like ZnO / CuS composite material.

[0066] In this invention, the curing temperature is preferably 40~80℃; the curing time is preferably 3min~4h. As an embodiment of this invention, the curing temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃; the curing time can be 3min, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, or 4h. This invention enables the hydrophobic compound to be fully cured through the curing process.

[0067] A schematic diagram of the preferred method for preparing the self-healing superhydrophobic composite nanocatalyst provided by the present invention is shown below. Figure 1 As shown. From Figure 1As can be seen, this invention uses FTO as a substrate. First, a layer of ZnO is prepared on FTO by hydrothermal method to obtain a substrate for growing ZnO nanostructures (ZnO / FTO). Then, ZnO / CuS composite material is prepared on ZnO / FTO by continuous ion layer adsorption (SILAR Cycles) to obtain a substrate for growing nanoflower-like ZnO / CuS composite material (ZnO / CuS). Finally, through superhydrophobic modification, a self-healing superhydrophobic composite nanophotocatalyst (BP-ZnO / CuS) is obtained.

[0068] The present invention also provides the application of the self-healing superhydrophobic composite nanophotocatalyst described in the above technical solution or the self-healing superhydrophobic composite nanophotocatalyst prepared by the preparation method described in the above technical solution in the treatment of organic wastewater.

[0069] The present invention does not impose any special limitations on the method of applying the self-healing superhydrophobic composite nanophotocatalyst to treat organic wastewater; conventional photocatalyst application methods for treating organic wastewater can be used.

[0070] This invention utilizes a hydrothermal method and the SILAR method to design a ZnO / CuS composite nanocatalyst with photothermal effect, and constructs a superhydrophobic surface by modifying a mixture of beeswax and PDMS. The preparation method is simple to operate and the sample morphology is controllable. A three-dimensional radial flower-like ZnO / CuS heterostructure was prepared on FTO using a hydrothermal method and a continuous ion layer adsorption method. The CuS composite expands the light absorption range of ZnO, allowing it to utilize sunlight more effectively. Under infrared light irradiation, ZnO / CuS exhibits significant photothermal behavior and higher light absorption, improving the photocatalytic activity of the heterostructure. The superhydrophobic modification improves the hydrophobicity of the sample surface, and the introduced beeswax contributes to the self-healing properties of the superhydrophobic surface. The superhydrophobic properties are also more stable and durable during application.

[0071] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0072] Example 1 A method for preparing a self-healing superhydrophobic composite nanocatalyst, comprising the following steps: (1) A zinc seed layer is grown on the substrate surface to obtain a substrate with a zinc seed layer; The method for growing a zinc seed layer on the substrate surface is as follows: FTO with a size of 1cm×2cm is ultrasonically cleaned for 10min in sequence with 0.1mol / L NaOH solution, ethanol and deionized water, and then dried at 60℃ for later use to obtain a pretreated substrate; The pretreated substrate was immersed in a 5 mmol / L Zn(CH3COO)2 ethanol solution for 15 s, then rinsed with ethanol and dried with argon. The immersion and drying were repeated 3 times. Then, the substrate was annealed at 400 °C for 60 min at a heating rate of 2 °C / min to obtain a substrate with a zinc seed layer. (2) The substrate with the zinc seed layer obtained in step (1) is immersed in 40 mL of soluble zinc salt solution, transferred into the liner of a 100 mL hydrothermal reactor, and subjected to hydrothermal reaction at 70 °C for 1.5 h to obtain a substrate with ZnO nanostructure (ZnO / FTO). The soluble zinc salt solution is composed of Zn(NO3)2·6H2O, KCl and ethylenediamine. The preparation method is as follows: Zn(NO3)2·6H2O and KCl are mixed, adjusted to clear with ethylenediamine, and stirred for 30 min. The concentration of Zn(NO3)2·6H2O in the soluble zinc salt solution is 0.075 mol / L, and the concentration of KCl in the soluble zinc salt solution is 0.09 mol / L. (3) The substrate with ZnO nanostructure obtained in step (2) is used to obtain a substrate (ZnO / CuS) with nanoflower-like ZnO / CuS composite material by continuous ion layer adsorption method. The continuous ion layer adsorption method is as follows: at room temperature, the substrate on which the ZnO nanostructure is grown is first immersed in a copper sulfate solution with a concentration of 50 mmol / L for 30 min, and then rinsed repeatedly with deionized water for the first cleaning. Then, it is second immersed in a Na2S·9H2O solution with a concentration of 50 mmol / L for 30 min, and then rinsed repeatedly with deionized water for the second cleaning. The continuous ion layer adsorption method is repeated 3 times. The molar ratio of copper ions in the copper sulfate solution to sulfur ions in the Na2S·9H2O solution is 1:1. (4) The substrate of the ZnO / CuS composite material with grown nanoflowers obtained in step (3) is immersed in a superhydrophobic modification solution (BP mixed solution) for 60s at room temperature, and then cured at 60°C for 180s to obtain a self-healing superhydrophobic composite nanophotocatalyst (BP-ZnO / CuS). The BP mixed solution is composed of beeswax, PDMS, platinum catalyst and tetrahydrofuran. The preparation method of the BP mixed solution is as follows: 0.1g beeswax, 0.15g PDMS and 0.015g platinum catalyst are added to 10mL tetrahydrofuran.

[0073] Example 2 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 1 in that the temperature of the hydrothermal reaction in step (2) is 80°C, while the remaining steps are the same as in Example 1.

[0074] Example 3 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 1 in that the temperature of the hydrothermal reaction in step (2) is 90°C, while the remaining steps are the same as in Example 1.

[0075] Example 4 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 1 in that the temperature of the hydrothermal reaction in step (2) is 100°C, while the remaining steps are the same as in Example 1.

[0076] Example 5 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 1 in that the temperature of the hydrothermal reaction in step (2) is 110°C, while the remaining steps are the same as in Example 1.

[0077] Test Example 1 The ZnO / FTO prepared in step (2) of Examples 1-5 were tested respectively, and the FESEM images of ZnO nanostructures under different reaction temperatures are shown below. Figure 2 As shown. In Figure 2In the figures, (a) represents 70℃, (b) 80℃, (c) 90℃, (d) 100℃, and (e) 110℃. This invention grows radial flower-like ZnO nanostructures on FTO via a hydrothermal method. The seed layer produces a certain epitaxial effect on the growth of the ZnO nanostructures, which can improve the interface roughness and enhance the stability of the nanostructures. On FTO-coated glass, the potential barrier for ZnO crystal nucleation and subsequent growth into perfect crystals is much higher than that of ZnO itself. This section first explores the effect of hydrothermal reaction temperature on the microstructure of ZnO nanostructures. The average grain size of the ZnO nanostructures increases with increasing hydrothermal reaction temperature. As the temperature increases, the morphology of the ZnO nanostructures changes to a 3D clustered flower-like structure composed of nanorods centered on a base point. At lower temperatures, the growth distribution of the ZnO nanostructures is uneven, with inconsistent diameters and irregular directions of the rod-like branches. When the temperature increases to 100℃, the aspect ratio of the nanorods increases, and the nanorod shape transforms into a nanoneedle-like morphology. As the temperature continues to rise to 110℃, the size of each nanorod branch increases. Appropriate aspect ratio and specific surface area are beneficial for providing more photocatalytic sites.

[0078] Test Example 2 The ZnO / FTO prepared in step (2) of Examples 1-5 were tested respectively, and the UV-Vis absorption spectra of the ZnO nanostructures under different reaction temperatures were obtained as follows: Figure 3 As shown in (a); the corresponding band gap diagram of the ZnO nanostructure at 100℃ is as follows. Figure 3 As shown in (b). By Figure 3 (a) It can be seen that the absorption peaks are the same at different temperatures, but the absorption intensities are slightly different. The absorption spectrum shows absorption at 373 nm, which can be attributed to the formation of ultrasmall ZnO crystals. The absorption peak is stronger at 100℃, and high temperature is conducive to the transformation of Zn(OH)2 into ZnO nanorods. Based on the above analysis, 100℃ was finally selected as the optimal reaction temperature, and the calculated band gap value is 2.92 eV.

[0079] Example 6 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 4 in that the concentration of Zn(NO3)2·6H2O in the soluble zinc salt solution in step (2) is 0.02 mol / L, while the remaining steps are the same as in Example 4.

[0080] Example 7 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 4 in that the concentration of Zn(NO3)2·6H2O in the soluble zinc salt solution in step (2) is 0.015 mol / L, while the remaining steps are the same as in Example 4.

[0081] Example 8 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 4 in that the concentration of Zn(NO3)2·6H2O in the soluble zinc salt solution in step (2) is 0.01 mol / L, while the remaining steps are the same as in Example 4.

[0082] Example 9 A method for preparing a self-healing superhydrophobic composite nanophotocatalyst differs from Example 4 in that the concentration of Zn(NO3)2·6H2O in the soluble zinc salt solution in step (2) is 0.025 mol / L, while the remaining steps are the same as in Example 4.

[0083] Test Example 3 The ZnO / FTO prepared in step (2) of Examples 6-9 were tested respectively, and the XRD patterns of ZnO nanostructures under different reaction solution concentrations were obtained as follows: Figure 4 As shown. In Figure 4 In the figure, 0.05C, 1.00C, 1.50C, and 2.00C represent the concentrations of Zn(NO3)2·6H2O as 0.01mol / L, 0.015mol / L, 0.02mol / L, and 0.025mol / L, respectively. From... Figure 4 It can be seen that the diffraction peaks of ZnO are consistent with the results of the JCPDS No. 75-1526 standard card, indicating that the prepared ZnO belongs to the hexagonal wurtzite phase. With the increase of concentration, the change in the ammonia-zinc ratio causes the growth rate of ZnO aspect ratio in various directions to change, and the intensity of the diffraction peak corresponding to the (101) crystal plane is observed to increase significantly. When the concentration is 0.02 mol / L, the nanorods grow more in the (001) direction, and the length increases near the core deposition point, which is consistent with the FESEM morphology results.

[0084] Test Example 4 The ZnO / FTO prepared in steps (2) of Examples 6-9 were tested respectively, and the FESEM images of the ZnO nanostructures under different reaction solution concentrations are shown below. Figure 5 As shown. In Figure 5 In the above, (a) and (b) are 0.50C, (c) and (d) are 1.00C, (d) and (f) are 1.50C, and (g) and (h) are 2.00C.

[0085] from Figure 5 It can be seen that the precursors are solutions of zinc nitrate and hexamethylenetetramine (HMT) in equimolar ratios under different concentration conditions. The ZnO nanorod aggregates can be attributed to [Zn(NH3)4]. 2+ and [Zn(OH)4] 2-The equilibrium between growth units under higher temperature and pressure, according to equations 1 and 2, occurs after Zn(NO3)2 hydrolyzes to Zn(OH)2, which then forms [Zn(NH3)4] with ammonium ions. 2+ Different concentration ratios have a certain impact on the microstructure; a large amount of [Zn(NH3)4] in the solution... 2+ The ions are converted to [Zn(OH)4] according to Equation 4. 2- The growth units form nuclei on the surface of ZnO nanocrystals, and polar ZnO grows along the (001) direction into a perfect hexagonal ZnO nanostructure. At low concentrations, the reaction rate and crystallization rate are slow, and the ZnO nuclei have sufficient growth time in both the vertical and horizontal directions, thus forming a large-diameter ZnO cone structure. As the solution concentration increases, the aspect ratio and cluster state of the ZnO nanorods continuously change, and the ZnO morphology gradually transforms from ellipsoidal to slender hexagonal pyramids. The reaction in this process is as follows: Zn 2+ +2NH3H2O→Zn(OH)2↓+2NH 4+ (1)

[0086] NO3 - +2e - +2H₂O→2OH - +NO2 - (3) [Zn(NH3)4] 2+ →4OH - +[Zn(OH)4] 2- +4NH3 (4) Test Example 6 The ZnO / FTO prepared in step (2) of Examples 6-9 were tested respectively, and the light absorption results of ZnO nanostructures at different concentrations were obtained as follows: Figure 6 As shown in (a), the band gap of the sample with a reaction concentration of 1.50C is as follows: Figure 6 As shown in (b). In Figure 6 It can be seen that ZnO has weak absorption in the visible light region, while the absorption peaks in the ultraviolet region are consistent at different concentrations. The nanostructure at a concentration of 1.50C exhibits better absorption in the ultraviolet region. According to... Figure 6 (b) The corresponding band gap value was calculated to be 2.71 eV. Based on the FESEM and XRD results, 1.50 C was considered to be the optimal concentration ratio.

[0087] Comparative Example 1 A method for preparing a composite nano-photocatalyst, comprising the following steps: (1)~(2) are the same as in Example 1; (3) The substrate for growing ZnO nanostructures was obtained by using the continuous ion layer adsorption method to obtain a substrate for growing nanoflower-like ZnO / CdS composite material (ZnO / CdS). The continuous ion layer adsorption method is as follows: at room temperature, the substrate on which the ZnO nanostructure is grown is immersed in a copper sulfate solution with a concentration of 50 mmol / L for 30 min, and then rinsed repeatedly with deionized water for the first cleaning. Then, it is immersed in a cadmium nitrate solution with a concentration of 50 mmol / L for 30 min, and then rinsed repeatedly with deionized water for the second cleaning. The continuous ion layer adsorption method is repeated twice.

[0088] Comparative Example 2 A method for preparing a composite nano-photocatalyst, comprising the following steps: (1)~(2) are the same as in Example 1; (3) The substrate with the obtained ZnO nanostructure was used to obtain the substrate (ZnO / Ag2S) with the growth of nanoflower-like ZnO / Ag2S composite material by the continuous ion layer adsorption method. The continuous ion layer adsorption method is as follows: at room temperature, the substrate on which the ZnO nanostructure is grown is first immersed in a copper sulfate solution with a concentration of 50 mmol / L for 30 min, and then repeatedly rinsed with deionized water for the first cleaning. Then, it is second immersed in a silver nitrate solution with a concentration of 50 mmol / L for 30 min, and then repeatedly rinsed with deionized water for the second cleaning. The number of cycles for the continuous ion layer adsorption method is preferably 4 times.

[0089] Test Example 7 FESEM images of nanostructures obtained under different sulfide composite conditions in steps (3) of Examples 1 and 2 are shown below. Figure 7 As shown. In Figure 7 In the diagram, (a) and (b) are ZnO / CdS, (c) and (d) are ZnO / Ag2S, and (e) and (f) are ZnO / CuS. From... Figure 7 As can be seen in (a) and (b), after three adsorption-reduction cycles, a small number of CdS nanoparticles are present around the ZnO nanobranches, exhibiting agglomeration and uneven distribution. When Ag₂S is adsorbed, the surface of ZnO becomes less smooth, with Ag₂S densely adsorbed onto the surface of the ZnO nanorods, resulting in large particle agglomerations. Compared to the previous two sulfides, CuS adsorption is more pronounced under the same cycle conditions, clearly showing CuS nanoparticles uniformly covering the surface of the ZnO nanorods, with stratified distribution to create an expanded specific surface area.

[0090] Test Example 8 The UV-Vis absorption spectra of the ZnO prepared in Example 1, and the nanostructures of different sulfide semiconductor composites prepared in step (3) of Examples 1 and 2 are as follows: Figure 8 As shown. From Figure 8 It can be seen that the pure ZnO nanostructure exhibits strong absorption in the ultraviolet region, while the three sulfides show strong light absorption in the visible light region but weak absorption in the ultraviolet region. In contrast to ZnO, CdS absorbs only a portion of the visible light region (540 nm), while Ag₂S and CuS absorb the entire visible light region. The absorption of visible light is improved with the introduction of sulfide semiconductors. Under the same adsorption cycle conditions, CuS significantly enhances the absorption of ZnO nanoflowers in the ultraviolet-visible region, and its overall absorption is stronger than other narrow-bandgap semiconductor composite nanostructures.

[0091] Test Example 9 The photoluminescence spectra of ZnO prepared in Example 1, and the different sulfides prepared in step (3) of Examples 1 and 2 are as follows: Figure 9 As shown. From Figure 9 It can be seen that ZnO has two emission bands: an ultraviolet emission band at 397 nm and a visible light emission band around 480 nm, which correspond to the wide bandgap edge emission of ZnO and the internal defects generated by exciton recombination in ZnO, respectively.

[0092] Furthermore, a distinct green fluorescence peak and a deep blue emission peak appeared near 450 nm. Electrons in this process transition from higher to lower energy levels, releasing photons; the energy difference between these high and low energy levels plays a decisive role in the photon energy. The increase or decrease in photoluminescence intensity (PL) is due to the presence of other non-radiative processes, such as electron-phonon interactions competing with radiative recombination. Higher photoluminescence intensity indicates higher electron-hole recombination efficiency and lower photocatalytic activity. Analysis of PL characteristics will help elucidate the structure of natural defects in ZnO. Spectroscopy shows that single ZnO nanostructures have the highest intensity, while sulfide recombination significantly reduces the photoluminescence intensity of composite structures, indicating a decrease in electron-hole recombination rate and a corresponding increase in photocatalytic activity. The ZnO / CuS composite nanostructure exhibits the lowest PL absorption intensity.

[0093] Test Case 10 Photocurrent is a current generated by light excitation. Through the action of circularly polarized light, the magnetic moments of atoms are precisely oriented, allowing light emitted from a helium lamp to pass through the absorption chamber and be focused onto the photosensitive element by a lens, ultimately generating a photocurrent. Its magnitude reflects the separation efficiency of electron-hole pairs; the larger the current, the better the separation efficiency. In this test example, a ZnO film was used as the photocathode, a Pt foil as the counter electrode, and Ag / AgCl as the reference electrode. The photochemical performance of the electrodes was tested in a three-electrode system. A 0.1 mol / L Na₂SO₄ aqueous solution was used as the electrolyte, and a 300W xenon lamp was used as the light source. Before performing photoelectrochemical measurements, argon gas was introduced into the solution to purge internal air for approximately 15 minutes. A chopper was used to cut off the light between the light source and the photocathode at 20 s / 20 s on / off intervals. Then, the current density and potential response of the electrodes were recorded using an electrochemical workstation (China, Chenhua, CHI-66OE).

[0094] The photocurrent response curves of the ZnO prepared in Example 1, and the nanostructures prepared in steps (3) of Examples 1 and 2, under different sulfide composite conditions are shown below. Figure 10 As shown, the bias voltage range is ±0.15. Photocurrent testing was used to evaluate the separation efficiency of photogenerated carriers. The photocurrent intensity is proportional to the separation efficiency of photogenerated electrons and holes; the higher the photocurrent intensity, the higher the photocatalytic performance. Under visible-ultraviolet light excitation, the photocurrent of a single ZnO nanostructure is the lowest. After sulfide recombination, the photocurrent is significantly enhanced, which is attributed to the heterostructure formed between ZnO and sulfides, which suppresses the photogenerated carriers of ZnO. It can be seen that the photocurrent is significantly enhanced after CuS recombination. After irradiation of the ZnO / CuS heterostructure, photogenerated electrons generated in the CB of the CuS surface migrate to the CB of ZnO, and then photogenerated holes in the VB of the ZnO surface migrate to the VB of CuS. When using 808nm, 2.5W / cm 3 When the surface of the composite photocatalyst (NIR-ZnO / CuS) was stably irradiated with near-infrared light, a significant increase in photocurrent density was observed, indicating that the photocatalyst was heated in situ due to the photothermal effect.

[0095] Test Example 11 The XPS pattern of the ZnO / CuS composite nanostructure prepared in Example 1 of this invention is as follows: Figure 11 As shown. In Figure 11 In the image, (a) Zn 2p, (b) Cu 2p, (c) O 1s, and (d) elemental distribution spectra are shown. Figure 11 In (b), the peak values ​​of 932.2 eV and 952.1 eV correspond to Cu 2p 3 / 2 and Cu 2p 1 / 2 represents Cu 2+ and Cu +The presence of Cu, similar to CuS, is possible during the deposition process. + It is in the oxidized state and forms another heterostructure with ZnO. Meanwhile, the peak value of 531.9 eV is consistent with the O content in ZnO. 2- This indicates that ZnO has been successfully synthesized. Figure 11 As shown in (a), the two peaks at 1044.9 eV and 1021.8 eV are assigned to Zn. 2p 1 / 2 and Zn 2p 3 / 2, they have the same effect as O1s. These results demonstrate the successful synthesis of ZnO / CuS composite nanocatalysts.

[0096] Test Example 12 TEM image of the ZnO / CuS composite nanostructure prepared in Example 1 of this invention is shown below. Figure 12 As shown in (a), the schematic diagram of the lattice fringes of CuS and ZnO is as follows. Figure 12 As shown in (b). From Figure 12 (a) Dispersed conical ZnO rods with attached CuS nanoparticles can be clearly seen, forming ZnO / CuS heterostructures at different locations. Measurement data show that the diameter of ZnO nanoclusters is approximately 30~70 nm, and the diameter of CuS nanoclusters is approximately 15~20 nm. The lattice spacing of 0.26 nm corresponds to the (002) crystal plane of hexagonal ZnO. Figure 12 (b) Due to the adsorption of a large number of CuS nanoparticles, the surface of the ZnO / CuS nanorods is rough (inset), and the lattice spacing of the CuS nanoparticles is 0.180 nm, corresponding to... Figure 11 (b) The (107) crystal plane of CuS.

[0097] Comparative Example 3 A method for preparing a composite nano-photocatalyst, which differs from Example 1 in that it only includes steps (1) to (3) and does not include step (4). The prepared composite nano-photocatalyst is simply referred to as ZnO / CuS.

[0098] Comparative Example 4 A method for preparing a composite nano-photocatalyst, comprising the following steps: (1) to (3) are the same as in Example 1; (4) Unlike Example 1, no paraffin was added. The prepared composite nano-photocatalyst is a superhydrophobic modified ZnO / CuS composite nanostructure.

[0099] Test Example 13 Example 5: Infrared vibrational spectrum of the superhydrophobic modified ZnO / CuS composite nanostructure as shown in Figure 5. Figure 13 As shown in (a), the contact angle diagram of the ZnO / CuS composite nanostructure prepared in Comparative Example 3 is as follows. Figure 13As shown in (b), the contact angle diagram of the BP-ZnO / CuS (i.e., the ZnO / CuS composite nanostructure after superhydrophobic modification solution treatment of beeswax-PDMS mixture) prepared in Example 1 is as follows. Figure 13 As shown in (c), the contact angle diagram of the ZnO / CuS composite nanostructure modified with PDMS after superhydrophobic modification prepared in Comparative Example 4 is as follows. Figure 13 As shown in (d). From Figure 13 As can be seen, the surface of the unmodified ZnO / CuS composite nanostructure is hydrophilic. Extending the previous superhydrophobic work, after immersing the composite nanostructure in a mixture of PDMS and beeswax (BP solution) for 60 s and then curing it, the contact angle (CA) reached 160°, also exhibiting excellent superhydrophobicity. Infrared vibrational spectroscopy confirmed the successful modification for superhydrophobicity, with a wavelength of 800 cm⁻¹. -1 and 1080cm -1 It is the infrared vibrational frequency of the Si-O bond. Beeswax is a small molecule compound, including alkanes and unsaturated esters. According to the spectral results, it is at 1735 cm⁻¹. -1 2960cm -1 2840cm -1 11375cm -1 and 1600cm -1 An absorption peak appears at the specified wavelength. PDMS is composed of repeating siloxane units, while hydrophilic ZnO / CuS exhibits a large number of -OH groups. When the sample is immersed in BP solution, the inherent hydrophobicity of organosilicon allows the siloxane groups and ester bonds to crosslink with the hydroxyl groups on the ZnO surface to form a self-assembled film, exhibiting superhydrophobicity.

[0100] Figure 14 (a) is the FESEM image of the ZnO / CuS composite nanostructure modified with PDMS after superhydrophobic modification prepared in Comparative Example 4. Figure 14 (b) is the FESEM image of BP-ZnO / CuS prepared in Example 1. Figure 14 (c) and (d) show the contact angle results of the BP-ZnO / CuS composite nanostructure before and after Plasma treatment. Figure 14 (e) and (f) show the contact angle results of the P-ZnO / CuS composite nanostructure before and after Plasma treatment; P-ZnO / CuS refers to the composite nanophotocatalyst prepared in Comparative Example 4 without the addition of paraffin.

[0101] A transparent gel-like substance was observed on the surface of the composite nanostructure obtained by PDMS modification, with a coating thickness of approximately 10 nm. After adding beeswax, significant amorphous colloidal adhesion was observed, but the coating did not completely cover the surface, thus retaining the photocatalytic active sites of the ZnO / CuS composite nanostructure. The decomposition of low surface energy substances on the coating surface was simulated by treating the coating with O2 plasma, and the self-healing ability of the superhydrophobic coating before and after adding beeswax was compared.Figure 14 (c)~(f)). After 3 min of O2 plasma treatment, the two coatings became hydrophilic to different degrees. The covalently bonded self-assembled layer on the coating surface was etched away by the O2 plasma, generating oxygen-containing hydrophilic groups on the coating surface. After treatment, the surface CA of the BP composite was 34±2°, and the surface CA of the single PDMS coating was 10±2°. The highly rough and porous coating structure combined with polyelectrolytes and hydrophilic oxygen-containing groups. After being placed in an environment with a relative humidity of 60℃ for 2.5 h, the BP-PDMS coating recovered its superhydrophobicity after O2 plasma treatment, with a contact angle of 159°.

[0102] Test Example 14 The superhydrophobic stability cycling test results of the two composite nanostructures in Example 1 and Comparative Example 4 are shown in the figure. Figure 15 As shown. For a single PDMS coating, it takes 3.5 hours to recover the superhydrophobic state, and the contact angle is approximately 156°. Figure 15 Cyclic testing results for superhydrophobic stability show that the introduction of beeswax enhances the plasma erosion resistance of the superhydrophobic coating and leads to rapid self-healing. The restoration of superhydrophobicity means that the B-PDMS coating treated with O2 plasma is again crosslinked with silicon-oxygen and ester bonds. Furthermore, the composite structure achieves reversible transformation between superhydrophobic and superhydrophilic states for at least five cycles. During the wettability transition, the contact angle of the BP-ZnO / CuS composite nanostructure recovers its superhydrophobicity with minimal change, indicating stronger stability in practical applications.

[0103] The self-healing process of the BP-PDMS superhydrophobic coating prepared in Example 1 is as follows: Figure 16 As shown, beeswax contains a large number of mobile small molecule compounds. When a mixture of PDMS and beeswax is attached to the surface of a composite nanostructure, the superhydrophobic coating's performance is compromised after multiple degradation cycles. Potentially hydrophobic molecules can migrate to the exposed ZnO / CuS composite nanostructure surface, replenishing necessary substances to ensure continued superhydrophobicity. For hydrophobic materials, increasing the heat treatment temperature will accelerate the recovery of superhydrophobicity. Superhydrophobicity and self-healing properties will help improve the durability of photocatalysts in complex environments.

[0104] Test Example 15 Figure 17 (a) shows the temperature change curves of three nanostructures over time under 808 nm infrared light irradiation (the inset is an infrared image of the ZnO nanostructure). Figure 17 (b) Images of the ZnO / CuS composite nanostructure acquired by an infrared imager. Figure 17(c) Infrared image of the BP-ZnO / CuS composite nanostructure. This experiment used an infrared imager to record the temperature changes of ZnO, ZnO / CuS, and BP-ZnO / CuS under 808nm infrared light irradiation. Figure 17 Under the same illumination, ZnO slowly heats up to a maximum of only 42℃ within 600s, while after composite with CuS, the composite photocatalyst heats up rapidly, with the ZnO / CuS composite nanostructure reaching approximately 100℃ within 200s. Even after introducing superhydrophobicity, the surface of the composite material still heats up, rapidly reaching 90℃ within 200s, demonstrating a significant photothermal conversion effect.

[0105] Compared to the ZnO / CuS composite nanostructure, the composite nanostructure exhibits a slight increase in absorption intensity and a redshift at the absorption edge in the UV-vis spectrum under near-infrared radiation. It has been reported that under high-temperature conditions, electron-phonon coupling is weaker, and the band gap of the semiconductor decreases with increasing temperature. The light absorption capability of the composite nanostructure is further improved, and the same results are obtained for the BP-ZnO / CuS composite nanostructure.

[0106] Figure 18 (a) and (b) are the UV-Vis absorption spectra of the nanostructures under 808 nm infrared light irradiation. Figure 18 (c) and (d) are the UV-Vis absorption spectra of the superhydrophobic nanostructure under 808 nm infrared light irradiation. The corresponding Tauc plots show that the band gap of the ZnO / CuS composite nanostructure decreases slightly under infrared light irradiation. Figure 18 The results show that CuS can absorb infrared light and convert it into heat energy, thereby improving the scope of solar energy utilization. The superhydrophobic modified composite nanostructure also exhibits photothermal conversion, indirectly proving the successful integration of photothermal effect and superhydrophobic function.

[0107] Photothermal conversion mechanism such as Figure 19 As shown, the photothermal effect originates from the weak electron-phonon collisional relaxation coupling in CuS under infrared irradiation, which leads to a local temperature increase. The band gap and hole diffusion length of the semiconductor are inversely proportional to the operating temperature. At higher temperatures, the transfer is accelerated, which promotes the separation of electrons and holes. Furthermore, thermal energy helps to lower the apparent activation energy of photocatalysis and improve the photocatalytic degradation efficiency.

[0108] Application Example 1 A colorant (methylene blue MB) was used as the model pollutant. A 300W high-pressure xenon lamp with a wavelength range of 200-800 nm was selected as the simulated light source and placed 10 cm vertically above the reaction tank during the photocatalytic reaction. Before formal degradation, a 30-minute dark treatment was performed. 20 mL of a 12 mg / L MB aqueous solution was poured into the photocatalytic container, the sample was placed inside, and the mixture was stirred in the dark for 30 minutes until adsorption-desorption equilibrium was reached. The absorption spectrum of the supernatant was analyzed using a UV-Vis spectrometer, and the concentration value converted from the intensity of the main absorption peak was recorded as C0. Then, the xenon lamp was turned on, and the water circulation was used for the photodegradation experiment. At room temperature, the suspension was continuously agitated by a magnetic field. Within a specific time period, 2 mL aliquots were centrifuged to remove the catalyst, and the MB concentration was determined by measuring its absorption spectrum using a UV-2600 UV-Vis spectrophotometer, denoted as Ct. The degradation efficiency of MB is expressed as "(C0-Ct)". t ) / C0)” to represent.

[0109] The photocatalysts used in this application example are ZnO, BP-ZnO / CuS prepared in Example 1, and ZnO / CuS prepared in Comparative Example 3, respectively.

[0110] Test Example 16 Figure 20 (a) is a graph showing the efficiency of photodegradation of MB by three photocatalysts. Figure 20 (b) shows the UV spectrum of MB during the photodegradation of the BP-ZnO / CuS composite nanostructure. Figure 20 (c) is a histogram of the ultraviolet absorption intensity values ​​of MB.

[0111] The photocatalytic performance of ZnO nanoflowers and BP ZnO / CuS and ZnO / CuS composite nanostructures was evaluated using photodegradation experiments via MB, with the active area of ​​the photocatalyst controlled at 0.5 cm². 2 The photodegradation rate of MB by the sample is as follows: Figure 20 As shown in (a), the MB degradation rate of the three samples increased slowly until it slowed down after 40 min. For the ZnO / CuS composite nanostructure before and after superhydrophobic modification, there was no significant difference in the degradation rate between the two samples, which reached over 95% at 80 min. The degradation efficiency of the pure ZnO nanostructure was consistently lower than that of the composite nanostructure, reaching only 76% at 80 min.

[0112] The UV-vis absorption spectrum of MB during the photodegradation of BP-ZnO / CuS is as follows: Figure 20 As shown in (b), the photodegradation time increases, and the decrease in the intensity of the characteristic peak of MB indicates a gradual decrease in the corresponding concentration. Most of the MB degrades within 80 minutes. Histograms were prepared based on the UV absorbance values ​​of three samples at approximately 650 nm.Figure 20 (c) It can be seen that the composite nanostructures have a significant degradation effect on MB. The photodegradation activities of the BP-ZnO / CuS and ZnO / CuS self-assembled nanostructures are similar, indicating that the superhydrophobic modification does not cause the loss of photocatalytic performance, and the photothermal agent can still play a photothermal conversion role. Analysis shows that the grafting modification of the PDMS and beeswax mixture does not completely cover the ZnO / CuS nanostructure, and a certain amount of ZnO / CuS nanostructure photocatalytic reaction sites are retained at the microscopic level, which can effectively realize the photoabsorption conversion and photodegradation reaction of the nanostructure.

[0113] Figure 21 The photocatalytic degradation mechanism of the ZnO / CuS composite nanostructure is shown. The introduction of narrow bandgap sulfides and ZnO forms a PN heterostructure, which facilitates the separation and transfer of photogenerated carriers and broadens the light absorption range of ZnO. Under light, electron-hole pairs are generated on the CuS surface, initiating valence band electrons to absorb energy and rise to the conduction band, then migrate to the conduction band of the ZnO nanoflowers at lower energy. This improves electron-hole recombination to some extent, and electrons in the CB of ZnO react (Equations 5-11). The formation of hydroxyl radicals participates in photocatalytic degradation. Holes in the VB of CuS react with water molecules to form hydroxyl radicals, which further react with organic molecules to generate CO2 and H2O.

[0114] CuS / ZnO+h v →CuS(h + ) / ZnO(e - Equation (5) ZnO(e - )+O2→O 2- Equation (6) O 2- · + H2O → H2O2 + OH· Equation (7) H2O2→OH· Equation (8) OH·+MB→CO2+water Formula (9) CuS(h + ) + H2O → OH· Equation (10) OH·+MB→CO2+water Formula (11) The results show that the photocatalyst provided by this invention exhibits significant photothermal behavior and higher light absorption under infrared irradiation, enhancing the photocatalytic activity of the heterostructure. The introduced beeswax contributes to the superhydrophobic self-healing properties, resulting in more stable and durable superhydrophobic performance during application. This invention first grows radially clustered flower-like ZnO nanostructures on an FTO seed layer using a hydrothermal method, and then uses the SILAR method to achieve self-assembly of CuS nanoparticles with the ZnO nanostructures through adsorption. On one hand, CuS acts as a heterostructure to improve electron-hole recombination. On the other hand, as a photothermal agent, the ZnO / CuS composite nanocatalyst increases its operating temperature under infrared irradiation, thereby prolonging light absorption and improving photocatalytic activity. Both the ZnO / CuS heterostructure and the BP-ZnO / CuS composite nanostructure exhibit excellent photocatalytic activity for methanogenic photocatalysis (MB).

[0115] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-healing superhydrophobic composite nanocatalyst, characterized in that, The invention includes a substrate, a nano-flower-like ZnO / CuS composite material grown on the surface of the substrate, and a superhydrophobic layer modified on the surface of the nano-flower-like ZnO / CuS composite material; the superhydrophobic layer is a composite coating obtained by curing a waxy material, a hydrophobic compound, and a curing agent.

2. The self-healing superhydrophobic composite nanocatalyst according to claim 1, characterized in that, The waxy material includes one or more of beeswax, paraffin, and stearic acid.

3. The self-healing superhydrophobic composite nanocatalyst according to claim 1, characterized in that, The hydrophobic compound includes organosilicon compounds or polyurethane.

4. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) A zinc seed layer is grown on the substrate surface to obtain a substrate with a zinc seed layer; (2) The substrate with the zinc seed layer obtained in step (1) is immersed in a soluble zinc salt solution and subjected to a hydrothermal reaction to obtain a substrate with a ZnO nanostructure. The soluble zinc salt solution is composed of soluble zinc salt, KCl, and ethylenediamine; (3) The substrate with ZnO nanostructure obtained in step (2) is used to obtain a substrate with ZnO / CuS composite material with nanoflower-like structure by continuous ion layer adsorption method. The method of the continuous ion layer adsorption method includes: first impregnating the substrate on which the ZnO nanostructure is grown in a copper cation solution, first cleaning it, then impregnating it in a sulfur anion solution, and then cleaning it again; the molar ratio of copper ions in the copper cation solution to sulfur ions in the sulfur anion solution is 1:

1. (4) The substrate of the ZnO / CuS composite material with grown nanoflowers obtained in step (3) is impregnated in a superhydrophobic modified solution for the third time, and then cured to obtain a self-healing superhydrophobic composite nanophotocatalyst. The superhydrophobic modified solution comprises wax material, hydrophobic compound, curing agent and solvent.

5. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to claim 4, characterized in that, In step (2), the concentration of soluble zinc salt in the soluble zinc salt solution is 0.01~0.075 mol / L, and the concentration of KCl is 0.05~0.15 mol / L.

6. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to claim 4, characterized in that, In step (2), the temperature of the hydrothermal reaction is 60~150℃ and the time of the hydrothermal reaction is 0.5~3h.

7. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to claim 4, characterized in that, In step (3), the time for the first immersion and the second immersion are independently 10 to 60 minutes.

8. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to claim 4, characterized in that, The number of cycles for the continuous ion layer adsorption method in step (3) is 2 to 5.

9. The preparation method of the self-healing superhydrophobic composite nanocatalyst according to claim 4, characterized in that, In step (4), the concentration of wax material in the superhydrophobic modification solution is 0.005~0.03 g / mL, and the concentration of hydrophobic compound is 0.01~0.06 g / mL.

10. The application of the self-healing superhydrophobic composite nanophotocatalyst according to any one of claims 1 to 3 or the self-healing superhydrophobic composite nanophotocatalyst prepared by the preparation method according to any one of claims 4 to 9 in the treatment of organic wastewater.

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