Method for directionally regulating and controlling morphology of ZnO / CuO piezoelectric catalyst based on betulinic acid self-assembly and piezoelectric application of ZnO / CuO piezoelectric catalyst

Abstract

The invention provides a method for directionally regulating and controlling the morphology of a ZnO / CuO piezoelectric catalyst based on betulinic acid self-assembly and piezoelectric application of the ZnO / CuO piezoelectric catalyst, belongs to the technical field of environmental functional materials, and aims to solve the technical problem of low heterojunction catalytic activity. According to the method, betulinic acid is taken as a dynamic soft template and a structure-directing agent, reaction conditions are regulated and controlled, the ZnO / CuO piezoelectric catalyst with the multilevel morphology is successfully prepared, the ZnO / CuO piezoelectric catalyst comprises three representative ZnO / CuO piezoelectric catalysts with a shuttle-shaped structure, a star-shaped structure and a sea urchin-shaped structure, and the three structures have the trend of sharp protrusions and strain gradient increase. The multi-stage morphology piezoelectric material prepared by the invention shows excellent piezoelectric catalytic performance under a low-frequency mechanical stirring condition, and the catalytic activity of the multi-stage morphology piezoelectric material shows UPsgt; sPSgt, SPSgt; aPSgt, APSgt; and the RPS changes regularly. Particularly, the catalyst with the sea urchin-shaped structure shows the most excellent catalytic performance on degradation of rhodamine B dye. The invention not only provides a new way for the application of the high-performance piezoelectric catalyst in the field of environmental restoration, but also provides an important reference for the development of a supermolecule mediated catalyst morphology controllable synthesis strategy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental functional materials, and particularly relates to a low-frequency and low-energy type ZnO / CuO piezocatalyst. BACKGROUND

[0002] Industrial dye wastewater has characteristics such as non-biodegradability and high toxicity, which poses a serious threat to water resource safety. Piezocatalytic technology has shown great application potential in environmental remediation by converting mechanical energy in the environment into polarized charges and then generating reactive oxygen species. However, most existing piezocatalysts rely on high-intensity ultrasonic driving, which greatly limits their practical application range. Therefore, developing piezocatalysts with good biocompatibility and high efficiency under low-frequency mechanical conditions is of great significance for promoting the practical application of the technology in environmental remediation.

[0003] Zinc oxide (ZnO) has attracted widespread attention in the field of piezocatalysis due to its excellent piezoelectric properties, controllable morphology characteristics, good biocompatibility, and low cost. However, pure-phase ZnO has inherent defects such as low piezoelectric coefficient and high carrier recombination rate. For example, patent publication CN 118988282A discloses a ZnO nano piezoelectric photocatalyst and its preparation method and application, which belongs to the field of piezoelectric photocatalysts. The invention uses sol-gel and solvothermal methods to prepare ZnO hexagonal sheets with different thicknesses by adjusting experimental parameters. Existing research shows that constructing a CuO-doped ZnO heterojunction and morphology regulation (including introducing specific anions to adjust the crystal structure and using PEG-400 surfactant to regulate crystal growth) can effectively improve the piezocatalytic activity. For example, patent publication CN 118267995A discloses the application of a copper-based catalyst in degrading methylene blue in organic dye wastewater. The copper-based catalyst is a CuO-ZnO-Cu(OH)2 composite material, which is prepared as follows: Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water, NH3·H2O is added while stirring, and the mixture is reacted at 80℃. Then, 1mol / L NaOH solution is added, and the mixture is reacted at 80℃. After the precipitate is separated and washed, it is dried to obtain the CuO-ZnO-Cu(OH)2 composite material. However, how to achieve the synergistic integration of these two strategies is still a key technical problem in developing efficient ZnO-based piezocatalysts. At present, the controllable synthesis of ZnO / CuO heterojunction still lacks effective methods for precise control of crystal structure, and there are the following technical bottlenecks in morphology optimization and piezoelectric performance improvement: 1) it is difficult to accurately control the transition of the catalyst from one-dimensional rod-like structure to multi-level structure; 2) there is a lack of effective means to regulate the strain gradient and piezoelectric potential distribution of the heterojunction; 3) the existing synthesis method cannot simultaneously consider the biocompatibility and piezoelectric activity of the catalyst.

[0004] In the prior art, although the piezoelectric catalytic activity can be improved by constructing CuO-doped ZnO heterojunction and morphology regulation, there is a lack of effective method for precisely regulating the crystal structure of ZnO / CuO heterojunction in the development of efficient ZnO-based piezoelectric catalysts, it is difficult to precisely control the transition of the catalyst from one-dimensional rod-like structure to multi-level structure, and there is a lack of effective means for regulating the strain gradient and piezoelectric potential distribution of the heterojunction, resulting in low electrocatalytic activity and limited application. SUMMARY

[0005] In view of the technical problem of low catalytic activity of ZnO / CuO heterojunction, the present application provides a method for self-assembly directional regulation of ZnO / CuO piezoelectric catalyst morphology based on white birch acid and piezoelectric application thereof, which realizes precise regulation of catalyst morphology and green synthesis. Specifically, the present application innovatively uses the self-assembly fiber structure of a specific triterpenoid compound, white birch acid (BA), as a dynamic soft template and structure directing agent, and introduces a supramolecular regulation mechanism into the traditional hydrothermal synthesis process to realize precise control of the crystal growth of ZnO / CuO heterojunction. This synthesis strategy not only solves the problem of difficult morphology regulation of traditional piezoelectric catalysts, but also provides a new technical approach for developing efficient and environmentally friendly piezoelectric catalysts.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A method for self-assembly directional regulation of ZnO / CuO piezoelectric catalyst morphology based on white birch acid, comprising the following steps:

[0008] (1) Dissolve white birch acid into dimethyl sulfoxide to form a mother liquor, then add water dropwise under ultrasonic conditions to perform self-assembly, and obtain white birch acid self-assembly body;

[0009] (2) Mix zinc salt, copper salt, BA self-assembly body and solvent to obtain a reaction solution, add precipitating agent to the reaction solution after chelation to perform hydrolysis reaction, and obtain ZnO / CuO piezoelectric catalyst.

[0010] The concentration of white birch acid in the mother liquor is 10-20 mmol / L; and the volume ratio of the mother liquor to water in step (1) is 1:10.

[0011] The zinc salt is zinc acetate, zinc chloride or zinc nitrate; the copper salt is copper acetate, copper chloride or copper nitrate; the molar ratio of the zinc salt to the copper salt is 9:1; and the concentration of the zinc salt in the reaction solution is 1.4-12 mmol / L.

[0012] The concentration of the BA self-assembly body in the reaction solution is 0.4-3 mmol / L.

[0013] The solvent is water.

[0014] The solvent is dimethyl sulfoxide and water in a volume ratio of (0.5-2):9.

[0015] The precipitant is NH3·H2O, NaOH, KOH, and the concentration of OH - in the reaction solution after adding the precipitant is 4-48 mmol / L.

[0016] The chelation reaction time is 2-24 h, and the hydrolysis reaction temperature is 50-100 DEG C, and the time is 3-24 h.

[0017] Application of a ZnO / CuO piezoelectric catalyst in degrading organic pollutants.

[0018] The application has the following beneficial effects: the natural triterpenoid small molecule can form a specific supramolecular structure due to its unique self-assembly characteristics, and the carboxyl and hydroxyl groups on the surface can realize accurate regulation of ZnO / CuO crystal growth through metal chelation. Therefore, natural pentacyclic triterpenoids, such as betulinic acid, are used as a dynamic soft template and structure directing agent, and by regulating the reaction conditions, a multi-level morphology ZnO / CuO piezoelectric catalyst is successfully prepared, including three kinds of ZnO / CuO piezoelectric catalysts with sharp protrusions and strainable gradient gradually increasing, specifically shuttle-shaped structure (APs), star-shaped structure (SPs) and urchin-shaped structure (UPs), and by comparing with the existing rod-shaped structure (RPs) ZnO / CuO, it is found that the three kinds of piezoelectric materials with the above-mentioned morphologies all exhibit excellent piezoelectric catalytic performance under low-frequency mechanical stirring conditions, and the catalytic activity shows a regular change of UPs>SPs>APs>RPs. In particular, the urchin-shaped structure catalyst (UPs) exhibits the most excellent catalytic performance in degrading rhodamine B dye, and the degradation rate constant can reach 40.8*10 -3 min -1 The application not only provides a new way for the application of high-performance piezoelectric catalysts in the field of environmental remediation, but also provides an important reference for the development of a supramolecular-mediated catalyst morphology controllable synthesis strategy. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0020] Figure 1Transmission electron microscope images of four ZnO / CuO piezoelectric reagents with BA self-assemblies: (A) BA self-assemblies; (B) BA@APs prepared in Example 1; (C) BA@SPs prepared in Example 2; (D) BA@UPs prepared in Example 3.

[0021] Figure 2 ESR spectra of (A) hydroxyl radicals and (B) superoxide anions induced by ZnO / CuO with different morphologies were prepared in Examples 1-3 and Comparative Example 1 under static and stirring conditions.

[0022] Figure 3 For XPS analysis of ZnO / CuO, XPS full spectrum (A) and corresponding O1s (B), Zn 2p (C), and Cu 2p (D) spectra of four different morphologies of ZnO / CuO piezoelectric catalysts were prepared in Examples 1-3 and Comparative Example 1.

[0023] Figure 4 The degradation efficiencies of four ZnO / CuO piezoelectric catalysts with different morphologies for MB(A), RhB(B) and MO(C) prepared for Examples 1-3 and Comparative Example 1, as well as the kinetic curves of the degradation reactions of MB(D), RhB(E) and MO(F) under the same concentration conditions, were obtained.

[0024] Figure 5 TEM images of ZnO / CuO piezoelectric catalysts, (A) Example 4; (B) Example 5. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] A method for self-assembly and directional regulation of ZnO / CuO piezoelectric catalyst morphology based on betulinic acid, the prepared ZnO / CuO piezoelectric catalyst is spaceship-shaped, denoted as APs or BA@APs, the preparation method comprises the following steps: first, preparing BA supramolecular self-assembly by reverse precipitation. The step is to dissolve 5 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then add 10 mL of water drop by drop under ultrasonic conditions to complete the self-assembly process. After dispersing the above reaction solution containing BA self-assembly into 19 mL of water, 1 mL of aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h, and finally APs are collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0028] Example 2

[0029] A method for self-assembly and directional regulation of ZnO / CuO piezoelectric catalyst morphology based on betulinic acid, the prepared ZnO / CuO piezoelectric catalyst is star-shaped, denoted as SPs or BA@SPs, the preparation method comprises the following steps: first, preparing BA supramolecular self-assembly by reverse precipitation. The step is to dissolve 5 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then add 10 mL of water drop by drop under ultrasonic conditions to complete the self-assembly process, and 5 mg of BA self-assembly is obtained by centrifugal separation. After dispersing 5 mg of BA self-assembly into 30 mL of water, 1 mL of aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h, and finally SPs are collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0030] Example 3

[0031] A method for self-assembly and directional regulation of ZnO / CuO piezoelectric catalyst morphology based on betulinic acid, the prepared ZnO / CuO piezoelectric catalyst is star-shaped, denoted as SPs or BA@SPs, the preparation method comprises the following steps: first, preparing BA supramolecular self-assembly by reverse precipitation. The step is to dissolve 5 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then add 10 mL of water drop by drop under ultrasonic conditions to complete the self-assembly process, and 5 mg of BA self-assembly is obtained by centrifugal separation. After dispersing 5 mg of BA self-assembly into 30 mL of water, 1 mL of aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h, and finally SPs are collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0032] The preparation method comprises the following steps: firstly, preparing BA supramolecular self-assembly by a reverse precipitation method. The step is to dissolve 20 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, and then 10 mL of water is added dropwise under ultrasonic conditions to complete the self-assembly process, and 20 mg of BA self-assembly is obtained by centrifugal separation. After 20 mg of BA self-assembly is dispersed in 30 mL of water, 1 mL of an aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h, and finally the UPs are collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0033] Comparative Example 1

[0034] Rod-like ZnO / CuO particles (RPs): These particles were synthesized by a widely reported alkaline hydrothermal method. Typically, 13 mg of Zn(CH3COO2·2H2O and 1.31 mg of Cu(CH3COO)2·H2O (zinc ion / copper ion molar ratio of 9:1) were dissolved in 20 mL of water and stirred at 70°C for 1 h. Subsequently, 25 μL of ammonia was slowly added, and then the reaction was continued at 70°C for 12 h to obtain RPs.

[0035] Test Example

[0036] 1. Piezoelectric production of active oxygen free radicals

[0037] The active oxygen free radicals (including hydroxyl radicals ·OH and superoxide anions ·O2-) produced in the piezoelectric catalysis process were systematically detected by electron paramagnetic resonance spectroscopy (EPR). First, four different morphologies of catalysts (RPs, APs, SPs and UPs) were respectively prepared into uniform dispersions with a concentration of 2 mg / mL, and 500 μL of each dispersion was mixed with 5 μL of DMPO free radical trapping agent (5,5-dimethyl-1-pyrroline-N-oxide). To comprehensively evaluate the piezoelectric catalytic performance of the catalysts, the experiments were carried out in two kinds of solvent systems, deionized water and methanol, respectively. The deionized water system is mainly used for detecting hydroxyl radicals, and the methanol system is used for detecting superoxide anions. During the test, 400 rpm mechanical stirring and static conditions were set to compare the promoting effect of mechanical stimulation on the generation of free radicals.

[0038] 2. Analysis of ZnO / CuO element composition and structure

[0039] The surface elemental composition and chemical state of ZnO / CuO composite catalysts were characterized by X-ray photoelectron spectroscopy (XPS). The test was carried out under ultra-high vacuum conditions, and monochromatic Al Kα ray (hv = 1486.6 eV) was used as the excitation source. First, the elemental composition of the sample surface was determined by full-spectrum scanning, and then high-resolution fine scanning was performed on the characteristic peak regions of Zn 2p, Cu 2p, O 1s, etc.

[0040] 3. Evaluation of dye degradation performance

[0041] In this study, the piezocatalytic performance of ZnO / CuO catalysts with different morphologies was evaluated using three typical organic dyes (Rhodamine B, Methyl Orange, and Methylene Blue). The specific experimental process was as follows: First, prepare 5 μg / mL dye solution and 3 mg / mL catalyst stock solution, take 1.8 mL dye solution and add 200 μL catalyst stock solution (final concentration 0.6 mg / mL), and stir at room temperature at a speed of 400 rpm. At 0, 5, 15, 30, 60, and 120 min, take samples, centrifuge at 14,000 rpm for 7 min, and then measure the absorbance at the characteristic wavelength (Rhodamine B: 554 nm; Methyl Orange: 464 nm; Methylene Blue: 664 nm). All experiments were set up in triplicate and performed under light-proof conditions, and a catalyst without mechanical stirring was used as a control.

[0042] The degradation rate constant (k) and degradation rate were calculated by fitting the degradation curve with a first-order kinetic model. This experimental scheme provides mechanical stimulation by controlling the stirring conditions, allowing accurate evaluation of the piezocatalytic performance of the catalyst, and multiple time-point sampling ensures the reliability of the degradation kinetics study.

[0043] As shown in Figure 1 A, the BA self-assembled body prepared by reverse precipitation has a fibrous morphology, and the BA self-assembled body exhibits excellent dispersibility in water, and the large number of -COOH and -OH on the surface of the assembly body provides the possibility for metal chelation. Under the induction of BA (5 mg) self-assembled body (system containing DMSO), the successful synthesis of ZnO / CuO (APs) Figure 1 B) with a shuttle shape. When the residual DMSO is removed, star-shaped ZnO / CuO (SPs) Figure 1 C) is successfully synthesized; when the BA content is further increased to 20 mg, urchin-shaped ZnO / CuO (UPs) Figure 1 D) is successfully synthesized. The four morphologies show an increasing trend in strain gradient, that is, the sharp protruding structure gradually increases, which provides the possibility for the occurrence of strain-induced piezoelectric effect.

[0044] As shown in Figure 2As shown, (5,5-Dimethyl-1-pyrroline N-oxide)5,5-dimethyl-1-pyrrole oxide (DMPO) acts as a spin trapping agent to capture free radicals. Transient ESR spectroscopy indicates that the four catalysts exhibit interactions with ·OH and O2 during piezoelectric catalysis. ·- The characteristic peaks corresponding to the spin adducts are DMPO-·OH (1:2:2:1) and DMPO-O2. ·- (1:1:1:1). And DMPO-O2 ·- The characteristic peaks of DMPO-·OH were not observed under static conditions (Control group). Under stirring conditions, DMPO-O2 ·- ( Figure 2 B) and DMPO-·OH( Figure 2 The appearance of characteristic peak A) indicates that O2 ·- ·OH and ·OH are the main active species. Compared with the other three catalysts, the UPs catalyst exhibits the highest ESR signal intensity, which is consistent with the observed trend of piezoelectric catalytic activity. This indicates that all four catalysts can further achieve carrier separation under stirring, with the UPs catalyst exhibiting the highest carrier separation efficiency.

[0045] XPS full spectra of four different ZnO / CuO morphologies are as follows Figure 3 As shown in Figure A, the Zn 2p, Cu 2p, and O 1s peaks are clearly visible. Further high-resolution spectroscopy reveals that the Zn 2p spectrum of ZnO has peaks near 1022 and 1045 eV, respectively. Figure 3 C), corresponding to Zn 2p 3 / 2 and Zn 2p 1 / 2 The dual-state signal indicates that Zn 2+ The presence of the oxidation state. The characteristic peak resolution of these peaks is 23.0 eV. Compared with the original ZnO 2P 3 / 2 Compared to (1021.3 eV), Zn 2p in the XPS spectrum 3 / 2 and Zn 2p 1 / 2 The binding energy shows a deviation, indicating a strong interaction between ZnO and CuO. A peak was observed in Cu 2p near 932 and 952 eV, respectively. Figure 3 D), corresponding to Cu 2p 3 / 2 and Cu 2p 1 / 2 The characteristic peak of these peaks is separated at 20.0 eV, indicating the presence of Cu in the +2 valence state in ZnO / CuO. In addition, two satellite peaks appear near 939.3-945.5 eV and 962.1 eV, belonging to Cu-O respectively, further illustrating the formation of CuO in ZnO / CuO. The O1s spectrum of ZnO / CuO shows two peaks (…).Figure 3 B), associated with lattice oxygen of ZnO / CuO at 530.8 eV, further support the formation of ZnO / CuO heterojunction.

[0046] As Figure 4 shown, we evaluated the catalytic performance by monitoring the changes in characteristic absorbance at 465 nm (methyl orange), 554 nm (rhodamine B), and 664 nm (methylene blue). Figure 4 A-C show the relative concentration (C t / C0) of the three dyes as a function of time under mechanical stirring. The experimental results show that all catalyst samples exhibit significant degradation effects on the three dyes. Specifically: for methylene blue Figure 4 A), the degradation efficiency of UPs catalyst within 2 h is the highest, reaching 72%; the degradation rate of rhodamine B Figure 4 B) is the highest, reaching 89.8%; while the degradation rate of methyl orange Figure 4 C) is relatively low, reaching 26.8%.

[0047] Degradation kinetics analysis Figure 4 D-F) shows a good linear relationship between ln(C0 / C t ) and time, consistent with the first-order reaction kinetics model (C = C0e -kt ). The first-order reaction rate constant (k) calculated by linear fitting shows that there are significant differences in the degradation efficiency of the three dyes by UPs catalyst, among which the degradation rate of rhodamine B is the highest (k = 40.8 x 10 -3 min -1 ), followed by methylene blue (k = 11.7 x 10 -3 min -1 ), and the degradation rate of methyl orange is the lowest (k = 3 x 10 -3 min -1 ). These results fully confirm that UPs catalyst has excellent piezocatalytic performance, and the degradation effect on different dyes shows obvious selectivity.

[0048] Example 4

[0049] A method for self-assembly of white birch acid to directionally regulate the morphology of ZnO / CuO piezocatalyst, the preparation process is basically the same as that of SPs, the difference is that the amount of BA used for self-assembly is increased to 10 mg, and the residual DMSO is also removed by centrifugation before the subsequent metal chelation and alkaline hydrolysis reaction.

[0050] The preparation method comprises the following steps: firstly, preparing BA supramolecular self-assembly by reverse precipitation. The step is to dissolve 10 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then add 10 mL of water drop by drop under ultrasonic conditions to complete the self-assembly process, and centrifugal separation to obtain 10 mg of BA self-assembly. After dispersing 10 mg of BA self-assembly into 30 mL of water, 1 mL of an aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h. Finally, ZnO / CuO is collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0051] Example 5

[0052] A method for self-assembly of white birch acid to directionally regulate the morphology of ZnO / CuO piezoelectric catalysts, the preparation process is basically the same as that of SPs, the difference is that the amount of BA used for self-assembly is increased to 15 mg, and the residual DMSO is removed by centrifugation before the subsequent metal chelation and alkaline hydrolysis reaction.

[0053] The preparation method comprises the following steps: firstly, preparing BA supramolecular self-assembly by reverse precipitation. The step is to dissolve 10 mg of BA in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then add 10 mL of water drop by drop under ultrasonic conditions to complete the self-assembly process, and centrifugal separation to obtain 10 mg of BA self-assembly. After dispersing 10 mg of BA self-assembly into 30 mL of water, 1 mL of an aqueous solution containing 0.656 mg of Cu(CH3COO)2·H2O and 6.49 mg of Zn(CH3COO)2·2H2O is added to the system, and the reaction is carried out under magnetic stirring for 4 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 70°C for 4 h. Finally, ZnO / CuO is collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0054] As Figure 5 shown, when the same preparation method of SPs and UPs is used, only the initial amount of BA is changed to 10 mg (Example 4) and 15 mg (Example 4), both of which obtain ZnO / CuO with increased sharp protrusions and irregular morphology, and contain urchin-like, star-like, and shuttle-like structures, indicating that BA indeed regulates the growth of ZnO / CuO crystals, confirming the role of BA templating directional regulation.

[0055] Example 6

[0056] A method for self-assembly and directional regulation of ZnO / CuO piezoelectric catalyst morphology based on betulinic acid, comprising the following steps: 5 mg of BA is dissolved in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then 5 mL of water is added dropwise under ultrasonic conditions to complete the self-assembly process, and 5 mg of BA self-assembly body is obtained by centrifugal separation. After dispersing 5 mg of BA self-assembly body into 30 mL of water, 1 mL of aqueous solution containing 0.242 mg of copper nitrate trihydrate and 0.545 mg of zinc chloride is added to the system, and the reaction is carried out under magnetic stirring for 2 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 50°C for 24 h, and finally ZnO / CuO is collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0057] Example 7

[0058] A method for self-assembly and directional regulation of ZnO / CuO piezoelectric catalyst morphology based on betulinic acid, comprising the following steps: 5 mg of BA is dissolved in 1 mL of dimethyl sulfoxide (DMSO) to form a mother liquor, then 5 mL of water is added dropwise under ultrasonic conditions to complete the self-assembly process, and 5 mg of BA self-assembly body is obtained by centrifugal separation. After dispersing 5 mg of BA self-assembly body into 30 mL of water, 1 mL of aqueous solution containing 0.242 mg of copper nitrate trihydrate and 0.545 mg of zinc chloride is added to the system, and the reaction is carried out under magnetic stirring for 2 h to realize metal chelation. Subsequently, 25 μL of NH3·H2O with a concentration of 25 wt% is added, and the reaction is carried out at 50°C for 24 h, and finally ZnO / CuO is collected by centrifugation (12000 rpm) and washed thoroughly with distilled water.

[0059] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for self-assembly and directional regulation of morphology of ZnO / CuO piezocatalyst based on betulinic acid, characterized in that, The method comprises the following steps: (1) dissolving betulinic acid into dimethyl sulfoxide to form a mother liquor, and then adding water drop by drop under ultrasonic condition to form a self-assembly of betulinic acid; (2) mixing a zinc salt, a copper salt, the self-assembly of betulinic acid and a solvent to form a reaction liquid, and then adding a precipitant to the reaction liquid after chelation to perform a hydrolysis reaction, thereby obtaining a ZnO / CuO piezoelectric catalyst.

2. The method according to claim 1, wherein the self-assembly of betulinic acid is used to direct the morphology of ZnO / CuO piezocatalyst. The concentration of betulinic acid in the mother liquor is 10-20 mmol / L; and the volume ratio of the mother liquor to water in step (1) is 1:5-20.

3. The method according to claim 2, wherein the self-assembly of betulinic acid is used to direct the morphology of ZnO / CuO piezoelectric catalysts. The zinc salt is zinc acetate, zinc chloride or zinc nitrate; the copper salt is copper acetate, copper chloride or copper nitrate; and the molar ratio of the zinc salt to the copper salt is 5-20:1-5; and the concentration of the zinc salt in the reaction liquid is 1.4-12 mmol / L.

4. The method according to claim 3, wherein the self-assembly of betulinic acid is used to direct the morphology of ZnO / CuO piezoelectric catalysts. The concentration of the self-assembly of betulinic acid in the reaction liquid is 0.4-3 mmol / L.

5. The method for self-assembly of birch tar acid based directional regulation of ZnO / CuO piezoelectric catalyst morphology according to any one of claims 1-4, characterized in that, The solvent is water.

6. The method for self-assembly of birch tar acid based directional regulation of ZnO / CuO piezoelectric catalyst morphology according to any one of claims 1-4, characterized in that, The solvent is dimethyl sulfoxide and water with a volume ratio of (0.5-2):

9.

7. The method according to claim 1, wherein the self-assembly of betulinic acid is used to direct the morphology of ZnO / CuO piezoelectric catalysts. The precipitant is NH3H2O, NaOH, KOH, the concentration of OH - in the reaction solution after adding the precipitant is 4-48 mmol / L.

8. The method according to claim 7, wherein the self-assembly of betulinic acid is used to direct the morphology of ZnO / CuO piezoelectric catalysts. The reaction time for chelation is 2-24 h; and the temperature for the hydrolysis reaction is 50-100 ℃, and the time is 3-24 h.

9. The ZnO / CuO piezoelectric catalyst prepared by the method according to any one of claims 1-8.

10. The use of the ZnO / CuO piezoelectric catalyst according to claim 9 in degrading organic pollutants.

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