Cu x O-ZnO Heterojunction Piezoelectric Material, Preparation Method Thereof and Multifunctional Application Therein in Catalysis and Oil-Water Separation

Abstract

The present invention discloses a Cu x O-ZnO heterojunction piezoelectric material and a preparation method thereof. A laser acts on the surface of a copper substrate in a cross-scanning manner to generate a Cu x O nanoparticle sheet layer. The Cu x O nanoparticles are used as the active growth sites of ZnO micro-nano structures. ZnO micro-nano structures are grown on the copper substrate through a hydrothermal reaction and applied to catalytic degradation. Further, when the copper substrate is a copper mesh, an oil-water separation film with a degradation function is prepared. The present invention can realize the hydrothermal growth of ZnO micro-nano structures without a seed layer, improve the catalytic degradation performance and the separation and purification performance, and realize multi-functional applications in the fields of wastewater treatment and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a Cu x O-ZnO heterojunction piezoelectric material, a preparation method thereof, and its multifunctional applications in catalysis and oil-water separation. Background Art

[0002] ZnO micro-nano structures, such as zinc oxide nanowires, show great potential due to their special structures and physical and chemical properties. For example, they can be used as photocatalysts to achieve efficient, safe, and environmentally friendly purification; also, since zinc oxide nanowires are non-centrosymmetric and easily bendable, they also belong to piezoelectric catalytic materials, and different forms of mechanical energy (such as sound waves, tides, wind, and atmospheric pressure) can induce piezoelectric catalysis. In addition, due to the rich active groups and hierarchical structures on the surface of metal oxides, the desired wetting behavior can be obtained to improve the separation and purification performance of the substrate, and it is applied to the membrane separation process. The above properties make ZnO micro-nano structures promising to play a comprehensive role in the treatment of polluted wastewater and the like.

[0003] The prior art prepares ZnO micro-nano structures by hydrothermal method. In order to enhance the adhesion between the ZnO micro-nano structures and the substrate, it is necessary to process the seed layer by atomic layer deposition (ALD) or electrochemical deposition before the hydrothermal method. Pretreating the seed layer before hydrothermal growth is a relatively complex process. Exploring how to achieve hydrothermal growth of ZnO without a seed layer is of great significance. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, the present invention provides a Cu x O-ZnO heterojunction piezoelectric material and a preparation method thereof. Using a zinc solution without a seed layer, ZnO micro-nano structures are synthesized on the surface of a copper substrate through laser pretreatment, and have multifunctional applications in fields such as catalytic degradation and oil-water separation.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A preparation method of a Cu x O-ZnO heterojunction piezoelectric material, comprising the following steps:

[0007] 1) In an oxygen-containing atmosphere, a pulsed laser acts on the surface of a copper substrate in a cross-scanning manner to form a grid-like ablation track, and Cu x O nanoparticle sheets are generated on the surface of the copper substrate; the thickness of the copper substrate is 100-500 μm; the power of the pulsed laser is 5-30 W, and the scanning speed is 300-700 mm / s;

[0008] 2) The one with Cu xThe copper substrate with CuO nanoparticle layers is placed in a hydrothermal reaction in a zinc oxide reaction precursor solution. The pH value of the zinc oxide reaction precursor solution is 9 to 11, and the molar concentration of Zn 2+ is 10 to 1000 mM. The temperature of the hydrothermal reaction is 90 to 200 °C, and the time is 1 to 3 h. ZnO micro-nano structures are grown on the copper substrate; among them, Cu x O nanoparticles serve as active growth sites for the ZnO micro-nano structures and form a Cu x O-ZnO heterojunction.

[0009] Preferably, the molar concentration of Zn 2+ is 10 to 200 mM.

[0010] Optionally, the repetition frequency of the pulsed laser is 1 to 50 kHz, the laser spot size is 25 to 35 μm, and the scanning pitch is 50 to 300 μm.

[0011] Optionally, the diameter range of the Cu x O nanoparticles is 20 to 80 nm.

[0012] Optionally, the zinc oxide reaction precursor solution is mixed with an aqueous solution of Zn(NO 3 ) 2 , an aqueous solution of hexamethylenetetramine, and a pH regulator. The pH regulator uses an alkaline solution such as ammonia water.

[0013] Optionally, during the hydrothermal reaction, the copper substrate is placed with the surface of the Cu x O nanoparticle layers inclined downward.

[0014] Optionally, the ZnO micro-nano structures include ZnO nanowires, and the diameter of the ZnO nanowires is 200 to 300 nm and the length is 1 to 4 μm.

[0015] The Cu x O-ZnO heterojunction piezoelectric material prepared by the above preparation method.

[0016] The application of the above Cu x O-ZnO heterojunction piezoelectric material in the piezoelectric catalytic degradation of organic substances, which is to apply mechanical energy to the Cu x O-ZnO heterojunction piezoelectric material for catalytic degradation of organic substances.

[0017] The application of the above Cu x O-ZnO heterojunction piezoelectric material in the piezoelectric-photocatalytic degradation of organic substances, which is to apply mechanical energy and light energy simultaneously to the Cu x O-ZnO heterojunction piezoelectric material for catalytic degradation of organic substances.

[0018] A preparation method of an oil-water separation membrane with catalytic degradation performance, comprising the following steps:

[0019] a) The thickness of the copper sheet is 100 - 500 μm. An array of through-holes is made on the copper sheet by laser drilling to form a copper mesh; the power range is 5 - 30 W;

[0020] b) Using the copper mesh as a copper substrate, grow ZnO micro-nano structures on the copper mesh by the preparation method of the Cu x O-ZnO heterojunction piezoelectric material described in any one of claims 1 - 6 to obtain an oil-water separation membrane with catalytic degradation performance.

[0021] Optionally, the aperture of the through-holes is 10 - 30 μm, and the hole pitch is 10 - 30 μm.

[0022] Optionally, the scanning trajectory passes through the position of the through-holes.

[0023] An oil-water separation membrane with catalytic degradation performance prepared by the above preparation method.

[0024] Application of the above oil-water separation membrane with catalytic degradation performance in wastewater treatment, wherein the oil-water separation membrane has underwater oleophobic performance, and the kinetic energy generated by oil-water separation is used for piezoelectric catalytic degradation of organic substances in water.

[0025] Among them, the wavelength range of the pulsed laser includes near ultraviolet, visible light, and near infrared.

[0026] Among them, the Cu x O nanoparticle sheet layer includes CuO and Cu 2 O. By changing the number of scans, adjust the ratio of CuO and Cu 2 O, and the range of the number of scans is 3 - 10 times.

[0027] Among them, for the catalytic degradation of organic substances, the organic substances refer to organic dye molecules, organic pesticides, etc.

[0028] Before laser processing the copper substrate material, it also includes a pretreatment step. The pretreatment includes sequentially ultrasonic cleaning the copper substrate material in acetone, ethanol, and deionized water, and drying it on a heating table. The drying temperature is 70 - 130 °C. Too low a drying temperature results in a slow drying speed, and too high a drying temperature causes the surface of the copper substrate material to be oxidized.

[0029] The copper mesh after hydrothermal growth is rinsed with deionized water and dried on a heating table; cleaning with organic solvents will cause carbonization on the surface of the copper mesh, resulting in the copper mesh being non-hydrophilic.

[0030] The above Cu xThe O-ZnO heterojunction piezoelectric material can also be applied to photocatalysis and / or piezocatalysis for anti-microbial purposes, achieving the use as an antibacterial agent.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1) Growth sites are obtained on the surface of the copper substrate through laser ablation, and the Cu x O / ZnO heterojunction micro-nano structure is obtained through hydrothermal growth, reducing the steps of preparing the seed layer and improving the efficiency; moreover, the morphology of the copper substrate surface can be adjusted by controlling the laser parameters, thereby affecting the growth of the ZnO micro-nano structure;

[0033] 2) The Cu x O / ZnO heterojunction has piezocatalytic performance and is polarized under external force to generate a dipole moment, providing a strong driving force for charge separation, promoting the migration of charges in opposite directions, improving the photocatalytic efficiency, and achieving high catalytic performance through the synergistic effect of photocatalysis and piezocatalysis, generating a large amount of reactive oxygen species (ROS), thereby realizing the application in the degradation of organic substances and the killing of microorganisms;

[0034] 3) Modifying the surface of the copper mesh with the Cu x O / ZnO heterojunction micro-nano structure enables the copper mesh to have underwater oil-repellent performance and achieve the function of oil-water separation; at the same time, by utilizing the catalytic performance of the Cu x O / ZnO heterojunction micro-nano structure, the separation and purification performance can be significantly improved, enabling the membrane to have the function of catalytic degradation and avoiding the problem of uneven catalysis; especially in the degradation of harmful organic substances in water, the kinetic energy generated by oil-water separation can be used for piezophotocatalysis to improve the energy utilization efficiency. Description of the Drawings

[0035] Figure 1 Schematic diagram of the preparation method of the Cu x O-ZnO heterojunction piezoelectric material in Example 1;

[0036] Figure 2 SEM surface morphology diagrams of ZnO obtained at different growth concentrations in Example 1, where (a) - (d), (i) - (l) are samples S1 - S8 in sequence, and (e) - (h), (m) - (p) are the corresponding partial enlarged views in sequence;

[0037] Figure 3 Schematic diagram of the comparison of the length (a), diameter (b), and aspect ratio (c) of ZnO obtained at different growth concentrations in Example 1;

[0038] Figure 4 For the Cu in Example 1 xSchematic diagram of the catalytic test results of the O-ZnO heterojunction piezoelectric material. (a) Schematic diagram of the catalytic degradation process of samples S1-S8; (b) Catalytic efficiency of samples S1-S8; (c) UV-visible absorption spectrogram of sample S8 during piezoelectric catalytic degradation; (d) Schematic diagram of the active oxygen capture experiment of hydroxyl radicals of sample S8.

[0039] Figure 5 For the surface-modified Cu in Example 2 x Schematic diagram of the preparation method of the copper mesh film (ZnO@Cu film) with the O / ZnO micro-nano structure

[0040] Figure 6 For the Cu on the surface of the copper mesh after laser ablation in Example 2 x SEM morphology diagram of O, where the magnification factors of (a), (b), and (c) increase in sequence

[0041] Figure 7 SEM morphology diagram of ZnO on the surface of the ZnO@Cu film in Example 2, where the magnification factors of (a), (b), and (c) increase in sequence

[0042] Figure 8 Schematic diagram of the XRD test results of the ZnO@Cu film in Example 2. Curve 1 is the test result of the ZnO@Cu film, and curve 2 is the test result of the copper mesh without hydrothermal growth after laser ablation Figure 3 Test result of the copper sheet without laser processing

[0043] Figure 9 XPS spectrogram of the ZnO@Cu film in Example 2. (a) is the total spectrogram, indicating the types of elements present on the surface of the ZnO@Cu film; (b) is the partial spectrogram of zinc, indicating that the zinc present on the surface of the copper mesh is in the divalent oxidation state; (c) indicates the presence of cuprous oxide on the surface of the ZnO@Cu film; (c) confirms the presence of the Zn-O bond

[0044] Figure 10 Schematic diagram of the stability test results of the ZnO@Cu film in Example 2. (a) is the thermal stability test, showing the underwater oleophobic angle after high-temperature heating at 100°C - 300°C; (b) is the chemical stability test, showing the underwater oleophobic angle after immersion in solutions with pH values ranging from 4 to 8

[0045] Figure 11Schematic diagram of the structural changes of ZnO nanowires in the ZnO@Cu film under different reaction conditions in Example 2, where (a) shows the change in the length of the nanowires under different reaction solution concentrations; (b) shows the change in the diameter of the nanowires under different reaction solution concentrations; (c) shows the change in the aspect ratio of the nanowires under different reaction solution concentrations. (d)–(g) show the surface morphologies of the ZnO nanowires grown at the laser ablation sites under hydrothermal durations of 2 h, 4 h, 6 h, and 8 h;

[0046] Figure 12 Photocatalytic and piezocatalytic synergy of the ZnO@Cu film (hydrothermal duration 2 h) in Example 2 for MB, where (a) shows the ultraviolet-visible light absorption spectrum; (b) shows the degradation concentration-time change curve; (c) shows the kinetic curve;

[0047] Figure 13 Concentration-time change curves of the degradation of the ZnO@Cu film obtained under different hydrothermal reaction times in Example 2 under photocatalysis and synergy catalysis;

[0048] Figure 14 Schematic diagram of the structures of different laser-ablated copper meshes in Example 3, where (a) shows the relative positions of the scanning trajectories of three different laser grid-shaped cross-scans of A / B / C and the through-hole array, and (b) shows the SEM morphologies of the surfaces of type B and type A growing zinc oxide;

[0049] Figure 15 For Figure 14 Comparison diagram of the underwater oleophobic angles of the ZnO@Cu film on the type A substrate (a) and the ZnO@Cu film on the type C substrate (b) under different laser parameters;

[0050] Figure 16 Schematic diagram of the oil-water separation test results of the ZnO@Cu film in Example 3; where (a) shows the physical diagram of the oil-water separation; (b) shows the water flux under different pressures; (c) shows the separation efficiency of the ZnO@Cu film obtained with three different laser scanning spacings after 20 separation cycles;

[0051] Figure 17 Schematic diagram of the mechanism of the synergistic effect of the piezoelectric-photocatalytic degradation performance and the oil-water separation performance of the ZnO@Cu film in Example 4. Detailed implementation mode

[0052] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0053] Example 1

[0054] Figure 1 For the Cu x O-ZnO heterojunction piezoelectric material preparation method schematic diagram.

[0055] A copper sheet with a thickness of 300 μm was cut into small pieces of 1 cm × 1 cm, ultrasonically cleaned in acetone, ethanol and deionized water for 3 minutes in turn, and then dried with compressed nitrogen. A nanosecond pulse laser light source with a wavelength of 1064 nanometers and a laser frequency of 25 kHz was used to prepare a grid-type microstructure substrate on the surface of the copper sheet by cross scanning. The laser spot size was 30 μm, the scanning speed was 500 mm / s, the scanning spacing was 50 microns, the scanning power was 25 W, and the number of scans was 10 times. After the scan, compressed nitrogen was used to blow away the nanoparticles with insufficient adhesion on the surface of the copper sheet. After laser irradiation and ablation, CuO and Cu 2 O micro-nanoparticles serve as growth sites for ZnO nanowires.

[0056] Prepare the precursor solution, the precursor solution is Zn(NO 3 ) 2 aqueous solution, hexamethylenetetramine aqueous solution and ammonia water are mixed in proportion, wherein Zn(NO 3 ) 2 The concentration ratio of ammonia to hexamethylenetetramine in the precursor solution is about 1:1, and the pH range of adding ammonia water to the precursor solution is 9-11.

[0057] The laser ablated surface of the copper sheet was placed upside down in a sealed 25 ml polytetrafluoroethylene bottle, 19 ml of the precursor solution was poured into the polytetrafluoroethylene bottle, and the bottle was sealed. After incubation in an oven at 150 ° C for 2 hours, the copper sheet was taken out of the growth solution, repeatedly rinsed with deionized water, and dried at 80 ° C to obtain Cu x O-ZnO heterojunction piezoelectric material.

[0058] Different growth concentrations (Zn(NO3) 2 The concentration of Cu in the precursor solution was obtained under the conditions of x The sample numbers of O-ZnO heterojunction piezoelectric materials are as follows:

[0059] S1 S2 S3 S4 S5 S6 S7 S8 <![CDATA[Zn(NO3) 2 Growth concentration (mM)]]> 1 25 50 100 200 400 600 800

[0060] Figure 2 The SEM images of ZnO nanorod morphologies obtained at growth concentrations ranging from 1 mM to 800 mM. Figure 2 (ap), with the increase of reactant concentration, the length of ZnO nanowires continues to increase; when the growth concentration reaches 400mM, the morphology of ZnO nanowires begins to change from cylindrical rods to hexagonal prisms, with a length of 4.7μm and a diameter of 1.2μm, and there is a small protrusion on the top of the hexagonal prism; when the concentration exceeds 600mM, the small protrusion on the hexagonal prism disappears, and the morphology of ZnO nanowires completely changes to hexagonal prisms, and no longer changes with the increase of reactant concentration.

[0061] At the growth concentration ranging from 1 mM to 800 mM, the variation trends of the length, diameter, and length-to-diameter ratio of ZnO nanowires are as follows Figure 3 shown. With the increase of the growth concentration, the length of ZnO nanowires increases from 0.33 μm to 5.4 μm, the diameter increases from 0.14 μm to 1.6 μm, and the length-to-diameter ratio of zinc oxide nanowires shows a trend of increasing first and then decreasing, with the maximum value at 50 mM.

[0062] Dissolve 0.3 mg of methylene blue powder in 500 ml of deionized water, and then take out 30 ml of methylene blue solution each time for catalytic degradation. At room temperature, put each group of samples into a beaker containing MB solution and keep it in the dark for 5 min to achieve dissociation and adsorption equilibrium. Then place the beaker in an ultrasonic cleaner with a power of 120 W and a frequency of 40 Hz for catalytic degradation experiments. Take out 3 - 4 ml of the solution every five minutes, after centrifugation, measure the change in the concentration of MB with a UV-visible spectrophotometer. To prevent the heat generated by ultrasonic vibration from affecting, the water in the ultrasonic cleaner is changed every ten minutes until the experiment is completed. The piezoelectric catalytic degradation efficiency is defined as (1 - C / C 0 )×100%, where C 0 is the concentration of MB at the adsorption equilibrium when T = 0 min, and C is the concentration of MB after 30 min of piezoelectric catalysis degradation.

[0063] As shown in Figure 4 (a), samples S1 to S8 are the process of piezoelectric catalytic degradation of MB dye by ZnO nanowire heterojunction arrays. Within a certain range, the increase in the length of ZnO nanowires is beneficial to improving the piezoelectric catalytic degradation performance of ZnO nanowire heterojunctions.

[0064] To further evaluate the piezoelectric catalytic degradation performance of ZnO nanowire piezoelectric catalysts, the UV-visible absorption spectra of sample S8 during the catalytic degradation process were tested. As shown in Figure 4 (b), the catalytic degradation performances of 8 types of zinc oxide nanowire heterojunctions were statistically analyzed. Figure 4 (c) shows the UV-visible absorption spectra (500 - 730 nm) of the MB solution degraded by S8 after different ultrasonic vibration times. The maximum absorption peak is at 664 nm. As the ultrasonic vibration time prolongs, the intensity of the maximum absorption peak of the MB solution gradually decreases, which fully shows that the zinc oxide grown on the copper sheet has piezoelectric catalytic ability. It can be seen from Figure 4 (d) that with the prolongation of the reaction time, the fluorescence spectrum of 2-hydroxyterephthalic acid at 429 nm is significantly enhanced, indicating that a large amount of hydroxyl radicals are generated during the piezoelectric process.

[0065] Example 2

[0066] Figure 5Surface-modified Cu for Example 2 x Schematic diagram of the preparation method of a copper mesh film (ZnO@Cu film) with a surface-modified Cu

[0067] A copper sheet with a thickness of 100 μm was cut into small pieces of 20 mm × 20 mm, ultrasonically cleaned in acetone, ethanol, and deionized water for 3 minutes in sequence, and then dried with compressed nitrogen.

[0068] A nanosecond pulsed laser source with a wavelength of 1064 nm was used, and the laser frequency was 25 kHz. By using the laser ablation method, with a laser power of 30 W, single-point processing was carried out on the copper sheet to form a through-hole array with a hole diameter of 30 μm and a hole pitch of 50 μm to obtain a copper mesh. Then, "well"-shaped grid-like cross-scanning was performed with a laser, the scanning power was 15 W, the laser spot size was 30 μm, the scanning pitch was 50 μm, the scanning speed was 500 mm / s, and the scanning times were 3 times. After the scanning was completed, the nanoparticles with insufficient adhesion force on the surface of the copper mesh were blown away by compressed nitrogen. After laser irradiation ablation, micro-nano particles of its oxide were generated on the surface of the copper mesh and served as the growth surface.

[0069] Prepare a precursor solution, which is prepared by mixing an aqueous solution of Zn(NO 3 ) 2 aqueous solution, hexamethylenetetramine aqueous solution, and ammonia water in proportion. The concentration ratio of zinc ions to hexamethylenetetramine in the precursor solution is about 1:1, and ammonia water is added to adjust the pH value of the precursor solution to 9 - 11. The copper mesh growth surface was inverted downward in a sealed 25 ml capacity polytetrafluoroethylene bottle, 15 mL of the precursor solution was poured into the polytetrafluoroethylene bottle, after sealing, it was hydrothermally treated in an oven at 150 °C for 2 hours, then the copper sheet was taken out from the growth solution, repeatedly rinsed with deionized water, and dried at 80 °C for 1 hour.

[0070] Reference Figure 6 , after laser ablation, there are many fine particles Cu x O with a layered secondary structure on the original smooth copper sheet, which includes Cu 2 O and CuO, with a diameter of about 50 nm. The formation process of the lamellar secondary structure during the laser ablation process includes the formation of plasma, the generation of shock waves, the expansion of the plasma plume, and the dynamic growth of nanoparticles. When the laser energy reaches the ablation threshold, the material is ablated and plasma is generated. Due to the generation of plasma accompanied by the release of a large amount of energy, resulting in high temperature and high pressure, the plasma has a high kinetic energy. Nucleation in low-temperature air leads to the generation and aggregation of fine particles. Under the action of gravity, the fine particles are deposited on the surface of the copper mesh.

[0071] In this example, the scanning trajectory of the laser grid-like cross-scanning passes through the position of the through-holes. Reference Figure 7 , Zn(NO 3 ) 2When the concentration is 45 mM, the ZnO micro-nano structure includes nano-flowers, which are composed of conical nanowires and are distributed in a central rotationally symmetric pattern. The size of a single nanowire is 200 - 300 nm and the length is 1 - 4 μm. The nano-flowers are mainly distributed in the area between the ablation gap (hereinafter referred to as the micro heat-affected zone) that is not directly laser-ablated and the pore wall perpendicular to the surface of the copper mesh. The growth of the nano-flowers depends on the Cu x O nanoparticles deposited on the surface of the copper mesh. A large number of oxygen atoms in the air are adsorbed on the surface of the copper mesh, but the crystals on it are unstable and have a large number of defects. When a liquid droplet is dropped on its surface, it spreads rapidly, showing superhydrophilicity. The surface energy of the secondary layered structure is high, and the coordination ion Zn(OH) 4 2- is easily adsorbed in the solution and can serve as a growth site. The first few atomic layers of ZnO adopt a low-energy configuration different from the bulk lattice and then transform into the (0001) orientation through a slight structural transformation. The crystals grow along the c-axis, which is where they grow the most. Although some smaller-sized (~20 nm) particles are also deposited on the ablation gap surface, only the flaky structure on the ablation block surface can grow ZnO nanowires with strong adhesion. A white substance can be seen on the dried sample. Referring to Figure 8 , the XRD analysis of the laser-ablated copper sheet shows that there are sharp peaks in the pattern, indicating a high crystallinity on the surface of the copper mesh.

[0072] Figure 9 The wide-scan XPS spectrum shows the presence of copper, carbon, zinc, and oxygen on the surface of the copper mesh after hydrothermal growth. The presence of Cu, Zn, and O elements on the ZnO@Cu film surface confirms the successful introduction of O and Zn elements. The binding energy difference of ~23 eV between 2p1 / 2 and 2p3 / 2 indicates that the zinc atoms in the nanowires are in the divalent (+2) oxidation state. At ~529.7 eV and ~531.2 eV, there are lattice oxygen and oxygen vacancy peaks in the wurtzite structure of zinc oxide. There are two obvious peaks at 933.6 eV and 953.82 eV, which are Cu2p3 / 2 and Cu 2p1 / 2 respectively. The two main peaks merge into four peaks at 952.46, 955.12, 932.84, and 935.20 eV, indicating the presence of Cu 2 O. Therefore, the presence of appropriate zinc and oxygen peaks in XPS confirms the existence of Zn-O bonds in the ZnO crystal. The hydrothermal copper mesh has obvious crystal peaks at 2θ = 31.74°, 34.37°, and 36.22°, corresponding to the (100), (002), and (101) crystal planes respectively, which are similar to the hexagonal wurtzite of ZnO.

[0073] The stability test of the ZnO@Cu film shows that after 70 min of ultrasonic shock, the ZnO@Cu film still retains a high density of nanowires. Referring to Figure 10, in terms of thermal stability, ZnO@Cu was heated on a hot plate at 100 - 300 °C (in 50 °C steps) for 30 min, and then the underwater oil contact angle of OCA was measured with little change, still maintaining the super - oleophobic state. To study the chemical stability, the samples were immersed in hydroxide or acetic acid solutions with different pH values prepared for 5 hours, and the changes in the underwater oil contact angle (OCA) of the above solutions on the sample surface were measured. It can be seen that within the pH range of 4 - 8, the underwater oil contact angle of OCA changes little.

[0074] Figure 11 (a) to (c) show the changes in the length, diameter, and aspect ratio of ZnO nanowires. As the hydrothermal time increased from 2 h to 8 h, the average length of ZnO nanowires changed little. In the precursor solution with a concentration of 18 - 45 mM of Zn(NO 3 ) 2 , the density of ZnO nanowires changed while their morphology remained unchanged. Figure 11 (d) to (g) show the representative cross - sectional and top - view SEM images of ZnO@Cu films and nanowires when changing the heating time in the growth solution. When the hydrothermal time was too long (such as 6 h), a large number of nanoparticles were deposited on the surface of the micro - heating area. The morphological changes of ZnO nanoflowers on the ablation block over time are as Figure 11 (d) to (g) show. When the hydrothermal time reached 2 h, a considerable number of nanoflowers could be seen forming.

[0075] The catalytic performance of the ZnO@Cu film was tested.

[0076] Through the degradation of MB dye by the ZnO@Cu film under ultraviolet light and ultrasonic action, the catalytic activity of the copper mesh modified with zinc oxide nanowires (hydrothermal reaction time 2 h) was investigated. According to the experimental results, a graph of the relationship between reaction time and concentration was plotted, as Figure 12 shown. Figure 12 (a) shows the absorbance of the MB solution during the degradation process by the ZnO@Cu film; Figure 12 (b) shows the enhanced catalytic activity of the ZnO@Cu film for the degradation of the MB solution under different environmental conditions. The graph shows the relationship between the reaction time and the change in the concentration of the MB dye, where the concentration was detected based on the absorbance. It can be seen that both ultraviolet light and ultrasonic action can achieve the degradation of the MB dye, with degradation efficiencies of 80.53% and 2% respectively, and the combined degradation activity is the highest, with a degradation efficiency of 81.02%; from Figure 12 (c) it can be seen that the combination of photocatalysis and piezoelectric catalysis can promote the degradation of organic substances.

[0077] Figure 13The degradation of copper mesh modified with zinc oxide nanowires obtained at different hydrothermal reaction times under ultraviolet light environment and ultraviolet light / ultrasound coupling environment can be seen. It can be seen that as the aspect ratio increases, the catalytic effect decreases (as the length-width ratio decreases, the catalytic performance decreases).

[0078] It can be seen that photocatalysis combined with piezocatalysis can promote the degradation of organic matter. Ultrasonic oscillation provides conditions for organic substances to fully contact ZnO. The reactive oxygen species (ROS) generated by the piezoelectric effect can cause a certain degree of degradation. The rate constant K value of 2h UV / ultrasound

[0079] is , which is much higher than the rate constant K value of 2h UV ( ), indicating its better piezophotocatalytic activity.

[0080] The bending deformation of ZnO nanowires generates electron-hole pairs. Electrons and holes diffuse to the surface of the nanowires, which helps the degradation of organic molecules. Therefore, the content of organic matter in the experiment shows a downward trend. Photo-generated carriers are carriers generated under light irradiation. Some carriers migrate to the surface and react with O 2 and H 2 2O to form highly reactive free radicals, which participate in the degradation of pollutants, while another part of the carriers tend to recombine due to random motion. Under the shearing action of dynamic water, ZnO nanowires deform and generate a piezoelectric field distribution.

[0081] In addition, due to the generation of a large amount of reactive oxygen species (ROS), similarly, it can participate in the killing of microorganisms to achieve its antibacterial / sterilization function and be applied to photocatalytic / piezocatalytic antibacterial materials.

[0082] The potential field in the piezoelectric material will cause internal charge accumulation, resulting in energy band rearrangement, which is an effective tool for regulating the carrier transport behavior. Therefore, photo-generated electrons (e) are attracted to the positive electrode of the piezoelectric field, while holes (h) will be repelled in the opposite direction. In addition, after the ZnO nanowires are impacted by random turbulence, the stress recovers, resulting in continuous changes in the direction of the piezoelectric field. The shorter the growth time of ZnO, the larger the aspect ratio and the vibration amplitude under external force, and the higher the separation efficiency of electron-hole pairs.

[0083] Example 3

[0084] Prepare the ZnO@Cu film by referring to the preparation method of Example 2, and test the oil-water separation performance of the ZnO@Cu film.

[0085] Change the relative position of the scanning trajectory of the laser grid-like cross-scanning and the through-hole array, such as Figure 14As shown, one type of through-hole is at the position of the line intersection of the through-hole serving as a scanning trajectory (Type A), another is at the position of the copper hole on the ablation block scanned by the grid (Type B), and the last one is to increase the scanning density (Type C). First, perform Type B scanning, and then perform Type A scanning. Different ZnO@Cu films are obtained with other parameters unchanged. It can be seen from SEM that the distribution of nanowires in the Type A mode is significantly higher than that in the Type B mode.

[0086] The ZnO@Cu film is applied to the oil-water separation film. Due to the modification of its ZnO nanowires, the separation and purification performance of the substrate can be significantly improved. Copper also has good biocompatibility and is suitable as a membrane for oil-water separation, thus having excellent hydrophilicity and underwater superoleophobicity. The contact angle of the oil droplet in water is determined by the solid-water surface tension, solid-oil surface tension, and oil-water surface tension. During the laser ablation process, the roughness of the copper substrate can be effectively controlled by changing the ablation depth of the grid-like cross-scanning.

[0087] ZnO@Cu films are prepared using the Type A substrate pattern and the Type C substrate pattern under different scanning laser power ablations respectively, and the underwater OCA is tested. The results are as Figure 15 shown. It can be seen that within the range of the scanning laser power from 13.5 W to 21 W, all ZnO@Cu films can achieve an underwater OCA of more than 150°. As the laser power increases, the corresponding surface roughness of the copper substrate also increases. The underwater OCA of the Type A and Type C substrates with the same roughness is compared, and there is no difference in OCA, indicating that only the roughness affects the underwater oleophobicity, and the specific morphology of the substrate has no effect.

[0088] The oil-water separation ability of the ZnO@Cu film is characterized by its flux and separation efficiency. As Figure 16 shown, Figure 16 (a) shows the oil-water separation process; Figure 16 (b) shows the relationship between pressure and flux, and the maximum flux of the oil-water mixture is 3.25×10 4 (l3·h·m-2); as Figure 16 (c) shows that for all tested oil-water mixtures, the separation efficiency of the ZnO@Cu film is greater than 99%. After 20 cycles, the separation efficiency can be maintained above 99%

[0089] Example 4

[0090] A method for treating polluted wastewater containing organic pollutants and oil uses the ZnO@Cu film of Example 3. On the one hand, its underwater oil-repellent property is utilized to achieve oil-water separation and purification. On the other hand, its piezo-photocatalytic degradation property is used to degrade organic pollutants, realizing a dual-functional membrane with an oil-water separation efficiency of 99% and a catalytic degradation efficiency of 70%. Among them, the kinetic energy generated by oil-water separation can be used for piezo-photocatalysis to improve the energy utilization efficiency. Reference Figure 17 , the ZnO nanowires are bent and deformed under the action of the kinetic energy of oil-water separation, and then electron-hole pairs are generated. These electron-hole pairs diffuse to the surface of the nanowires, contributing to the decomposition of organic molecules.

[0091] The above embodiments are only used to further illustrate a Cu of the present invention x O-ZnO heterojunction piezoelectric material, its preparation method and its multifunctional application in catalysis and oil-water separation. However, the present invention is not limited to the embodiments. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the technical solution of the present invention.

Claims

1. A kind of Cu x Preparation method of O-ZnO heterojunction piezoelectric material It is characterized in that It includes the following steps: 1) In an oxygen-containing atmosphere, a pulsed laser acts on the surface of a copper substrate in a cross-scanning manner to form grid-shaped ablation tracks, and a Cu x O nanoparticle sheet layer is generated on the surface of the copper substrate. The diameter range of the Cu x O nanoparticles is 20 - 80 nm; the thickness of the copper substrate is 100 - 500 μm; the power of the pulsed laser is 5 - 30 W, and the scanning speed is 300 - 700 mm / s; 2) Place the copper substrate with Cu x O nanoparticle sheets into the zinc oxide reaction precursor solution for hydrothermal reaction. The pH value of the zinc oxide reaction precursor solution is 9 - 11, and the molar concentration of Zn 2+ is 10 - 1000 mM. The temperature of the hydrothermal reaction is 90 - 200 °C, and the time is 1 - 3 h. Grow ZnO micro-nano structures on the copper substrate. The ZnO micro-nano structures include ZnO nanowires. Among them, Cu x O nanoparticles serve as the active growth sites of the ZnO micro-nano structures and form Cu x O-ZnO heterojunctions. The Cu x O-ZnO heterojunction piezoelectric material has both photocatalytic performance and piezocatalytic performance.

2. The Cu x preparation method of the O-ZnO heterojunction piezoelectric material according to claim 1 It is characterized in that: The repetition frequency of the pulsed laser is 1 - 50 kHz, and the laser spot size is 25~35 μm , and the scanning pitch is 50 - 300 μm .

3. The Cu x Preparation method of O-ZnO heterojunction piezoelectric material, It is characterized in that: The zinc oxide reaction precursor solution is a mixture of an aqueous solution of Zn(NO 3 ) 2 , an aqueous solution of hexamethylenetetramine, and a pH regulator.

4. The Cu according to claim 1 x Preparation method of O-ZnO heterojunction piezoelectric material It is characterized in that: During the hydrothermal reaction process, the Cu on the copper substrate x O nanoparticle sheets are placed with their surfaces inclined downward.

5. The Cu x preparation method of the O-ZnO heterojunction piezoelectric material according to claim 1, It is characterized in that: The diameter of the ZnO nanowires is 200~300 nm and the length is 1~4 μm.

6. Cu x O-ZnO heterojunction piezoelectric material prepared by the preparation method according to any one of claims 1 to 5.

7. The Cu x application of the O-ZnO heterojunction piezoelectric material in the piezoelectric catalytic degradation of organic substances It is characterized in that: Apply mechanical energy to the Cu x O-ZnO heterojunction piezoelectric material for catalytic degradation of organic substances.

8. The application of the Cu x O-ZnO heterojunction piezoelectric material in the piezoelectric-photocatalytic degradation of organic substances It is characterized in that: Apply mechanical energy and light energy simultaneously to the Cu x O-ZnO heterojunction piezoelectric material for catalytic degradation of organic substances.

9. The application of the Cu x O-ZnO heterojunction piezoelectric material in photocatalysis and / or piezocatalytic antimicrobial 10. A preparation method of an oil-water separation membrane with catalytic degradation performance It is characterized in that It includes the following steps: a) The thickness of the copper sheet is 100~500 μm. An array of through holes is made on the copper sheet by laser drilling to form a copper mesh; the power range is 5~30W; b) Using the copper mesh as the copper substrate, grow ZnO micro-nano structures on the copper mesh by the preparation method of the Cu x O-ZnO heterojunction piezoelectric material according to any one of claims 1 to 6 x , obtaining An oil-water separation membrane with catalytic degradation performance.​ 11. The preparation method of the oil-water separation membrane with catalytic degradation performance according to claim 10 It is characterized in that: The aperture of the through hole is 10 to 30 μm, and the hole pitch is 10~30 μm.

12. The preparation method of the oil-water separation membrane with catalytic degradation performance according to claim 10 It is characterized in that: The scanning trajectory passes through the position of the through hole.

13. The oil-water separation membrane with catalytic degradation performance prepared by the preparation method according to claim 10.

14. The application of the oil-water separation membrane with catalytic degradation performance according to claim 13 in wastewater treatment It is characterized in that: The oil-water separation membrane has underwater oleophobic performance, and the kinetic energy generated by oil-water separation is used for piezoelectric catalytic degradation of organic substances in water.

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