Heterojunction thin film photocatalyst and preparation method and application thereof
By preparing ZnO nanorod arrays on a flexible substrate and depositing purple phosphorus nanosheets to form a heterojunction thin film photocatalyst, the problems of low light energy utilization and difficult recycling of ZnO photocatalysts are solved, achieving high efficiency and stability, which is suitable for flexible optoelectronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUAINAN NORMAL UNIV
- Filing Date
- 2026-03-05
- Publication Date
- 2026-06-05
AI Technical Summary
Existing ZnO photocatalysts suffer from problems such as wide bandgap leading to limited ultraviolet light energy absorption, rapid carrier recombination, difficulty in recovering powder morphology, unsuitability of rigid substrates for flexible optoelectronic devices, insufficient carrier transport channels, and weak binding force.
A ZnO nanorod array layer was prepared on a flexible ITO-PEN substrate, and purple phosphorus nanosheets were deposited by self-adsorption method to form a pn-type heterojunction thin film photocatalyst, which combines efficient visible light absorption and carrier separation capabilities.
It improves photocatalytic efficiency, expands the photoresponse range, enhances carrier separation efficiency, and achieves catalyst stability and convenient recovery, making it suitable for flexible optoelectronic devices.
Smart Images
Figure CN122141704A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst preparation technology, specifically to a heterojunction thin-film photocatalyst, its preparation method, and its application. Background Technology
[0002] Antibiotics are widely used in human medicine, animal husbandry, and aquaculture due to their effective therapeutic effects. Levofloxacin (LEV), ciprofloxacin (CIP), norfloxacin (NOR), and gatifloxacin (GAT), as typical representatives of fluoroquinolone antibiotics, are widely used due to their better therapeutic efficacy and broader antibacterial spectrum. However, overuse and their stable chemical structure lead to their continuous accumulation in the environment, causing serious problems such as bacterial resistance and water pollution.
[0003] Semiconductor photocatalysis technology has become a highly promising solution due to its high efficiency, safety, low cost, and sustainability. Currently, commonly used photocatalysts for degrading pollutants such as antibiotics are semiconductor metal oxides, such as ZnO, TiO2, and CuO. Among them, ZnO is considered one of the most mature photocatalysts due to its safety, low price, chemical stability, and non-toxicity. However, single ZnO photocatalysts still face certain application obstacles. For example, its wide bandgap of 3.2 eV means it can only absorb ultraviolet light energy; rapid carrier recombination leads to low photocatalytic activity; in addition, traditional ZnO photocatalysts are mostly in powder form or supported on rigid substrates such as glass and silicon wafers, which presents problems such as difficulty in recycling and difficulty in adapting to flexible optoelectronic devices, thus limiting their practical engineering applications.
[0004] To address the aforementioned shortcomings, ZnO is often modified by constructing heterojunctions. This involves combining ZnO with narrow-bandgap semiconductor materials to expand the photoresponse range and promote photogenerated carrier separation. Currently reported narrow-bandgap materials are all two-dimensional, such as graphitic carbon nitride (g-C3N4), molybdenum disulfide (MoS2), and black phosphorus. Black phosphorus, with its tunable bandgap and high carrier mobility, exhibits excellent photocatalytic performance when combined with ZnO. However, its poor stability due to easy oxidation in air severely limits its practical applications. While g-C3N4 combined with ZnO shows good stability, its low carrier mobility limits the improvement in photocatalytic efficiency. MoS2, on the other hand, suffers from a narrow visible light response range and weak interfacial bonding with ZnO.
[0005] Regarding substrate selection, existing ZnO-based heterojunction photocatalysts typically use rigid substrates such as glass and silicon wafers. Some studies have used common flexible plastics (such as polyethylene terephthalate and polyimide) as substrates. However, rigid substrates such as glass and silicon wafers are hard and difficult to bend, making them unsuitable for emerging applications such as flexible optoelectronic devices and curved surface purification devices. They also suffer from drawbacks such as heavy weight and poor portability. While common flexible plastic substrates possess flexibility, they lack good conductivity, failing to provide an effective channel for the transport of photogenerated carriers. This significantly restricts the improvement of heterojunction photocatalytic efficiency. Furthermore, their poor surface hydrophilicity results in weak bonding between the ZnO-based material and the substrate, making it prone to detachment during use and affecting the stability and lifespan of the catalyst. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a heterojunction thin-film photocatalyst, its preparation method, and its applications. First, a ZnO seed layer is prepared by electrochemical deposition on a flexible ITO-PEN substrate. Then, a ZnO nanorod array layer is obtained by hydrothermal growth on the ITO-PEN substrate containing the ZnO seed layer. A purple phosphorus nanosheet (VPNS) solution is obtained through a simple liquid-phase ultrasonic exfoliation method. The VPNS solution is mixed with the grown ZnO nanorod array layer, and the VPNS is deposited onto the surface layer of the ZnO nanorod array through self-adsorption. After 2–4 hours of deposition, the mixture is vacuum-dried to obtain the heterojunction thin-film catalyst. The heterojunction thin film provided by this invention has advantages such as simple preparation method, high photocatalytic efficiency, good stability, and easy recovery.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows.
[0008] This invention provides a heterojunction thin-film photocatalyst, wherein a ZnO nanorod array layer and a purple phosphorus nanosheet layer are sequentially deposited and grown in a vertical direction on the surface of a flexible substrate, and a pn-type heterojunction is formed between the ZnO nanorod array layer and the purple phosphorus nanosheet layer.
[0009] Preferably, the thickness of the ZnO nanorod array layer is 3 micrometers to 8 micrometers, and the thickness of the purple phosphorus nanosheet layer is 3 nanometers to 15 nanometers.
[0010] Preferably, the flexible substrate is a flexible indium tin oxide conductive film; the flexible indium tin oxide conductive film is ITO-PEN; the ITO-PEN is a composite thin film material formed by depositing an ITO transparent conductive layer on a PEN flexible substrate; wherein, PEN represents polyethylene naphthalate; ITO represents indium tin oxide.
[0011] This invention also provides a method for preparing a heterojunction thin-film photocatalyst, comprising the following steps: Purple phosphorus and organic solvent were mixed, ultrasonically exfoliated, and centrifuged to obtain a purple phosphorus nanosheet solution.
[0012] ZnO seed layers were grown on a flexible substrate by electrochemical deposition using an aqueous solution of inorganic zinc salts. The flexible substrate containing the ZnO seed layers was placed in a precursor solution containing inorganic zinc salts and ammonia, and ZnO nanorod arrays were deposited and grown on the surface of the ZnO seed layers by hydrothermal reaction to form a ZnO nanorod array layer.
[0013] A flexible substrate containing a ZnO nanorod array layer is placed in a purple phosphorus nanosheet solution. Purple phosphorus nanosheets are deposited on the surface of the ZnO nanorod array layer by self-adsorption, forming a purple phosphorus nanosheet layer. A pn-type heterojunction is formed between the ZnO nanorod array layer and the purple phosphorus nanosheet layer, resulting in a heterojunction thin film catalyst.
[0014] Preferably, the concentration of the purple phosphorus nanosheet solution is 0.1 mg / mL to 50 mg / mL; and the concentration of the aqueous solution of the inorganic zinc salt is 5 mg / mL to 50 mg / mL.
[0015] Preferably, the inorganic zinc salt is Zn(NO3)2·6H2O; the mass ratio of ammonia to Zn(NO3)2·6H2O is 1 to 20:1; and the concentration of Zn(NO3)2·6H2O in the precursor solution is 5 mg / mL to 50 mg / mL.
[0016] Preferably, the electrochemical deposition conditions are: temperature 50℃~80℃, deposition time 1min~10min; the hydrothermal reaction conditions are: temperature 60℃~100℃, reaction time 5h~15h.
[0017] Preferably, the organic solvent is anhydrous ethanol or N-methylpyrrolidone.
[0018] Preferably, the drying atmosphere is argon or nitrogen, and the time is 0.5h to 2h.
[0019] Preferably, the ultrasonic time in the ultrasonic stripping process is 10h to 30h; the centrifugation speed is 500rpm to 5000rpm.
[0020] A third objective of this invention is to provide an application of the aforementioned heterojunction thin-film photocatalyst in the photocatalytic removal of pollutants. The photocatalytic degradation of LEV using the heterojunction thin-film photocatalyst was investigated, and its photocatalytic activity was studied. Specifically, a 2cm × 2cm heterojunction thin-film photocatalyst was placed in 10mL of a 10mg / L antibiotic-containing test solution. Adsorption was performed in the dark for half an hour, followed by irradiation under a 300W light source to achieve photocatalytic removal of antibiotics from the test solution. The concentration of the antibiotic-containing test solution was measured every 20 minutes using a UV-Vis spectrophotometer at different time points, and compared with an unirradiated antibiotic-containing test solution to study its photocatalytic efficiency.
[0021] Preferably, the antibiotic is levofloxacin; the light source is a xenon lamp.
[0022] The beneficial effects of this invention are: 1. This invention achieves high visible light utilization and high carrier separation efficiency by constructing a heterojunction between VPNS, which has high visible light absorption capacity and high carrier transport activity, and ZnO nanorod array layer grown on a flexible substrate ITO-PEN. It is then applied to the photocatalytic removal of organic pollutants such as antibiotics, and has the advantages of high pollutant removal efficiency, high catalyst stability, simple preparation method, wider application range, and easy recycling.
[0023] 2. This invention constructs a heterojunction thin-film photocatalyst through a simple self-deposition method. By modifying a traditional ZnO nanorod film with highly active two-dimensional purple phosphorus nanosheets, it not only improves the visible light absorption capacity, carrier separation efficiency, and catalytic activity of the heterojunction, but also significantly expands the catalyst's application range and post-use recovery capabilities on a flexible ITO-PEN substrate. Compared to traditional solutions, this invention offers a simple, efficient, and easy-to-use and recyclable preparation process, and demonstrates high efficiency in photocatalytic removal of organic pollutants. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the preparation process of the heterojunction thin film photocatalyst in an embodiment of the present invention.
[0025] Figure 2 Characterization images of the heterojunction thin-film photocatalyst prepared in Example 2 are shown. (A) is an optical photograph; (B) is a transmission electron microscope (TEM) image; and (C) is a high-resolution transmission electron microscope (HRTEM) image.
[0026] Figure 3 The image shows the elemental distribution of the heterojunction thin-film photocatalyst prepared in Example 2. In the image, (A) represents Zn; (B) represents O; and (C) represents P.
[0027] Figure 4 The images show the XRD patterns of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1.
[0028] Figure 5 The diffuse reflectance diagrams are of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalysts prepared in Comparative Example 1.
[0029] Figure 6 The fluorescence spectra of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1 are shown.
[0030] Figure 7 Transient photocurrent response diagrams of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1.
[0031] Figure 8 Impedance spectra of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1.
[0032] Figure 9 The photocatalytic performance diagrams are shown for the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1.
[0033] Figure 10 The reaction rate constants are plotted for the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1.
[0034] Figure 11 This is a stability test diagram of the heterojunction thin film photocatalyst prepared in Example 2.
[0035] Figure 12 The graph shows the photocatalytic performance of the heterojunction thin film photocatalyst prepared in Example 2 under different acid anions.
[0036] Figure 13 The heterojunction thin film photocatalyst prepared in Example 2 is shown to exhibit photocatalytic performance against different antibiotics.
[0037] Figure 14 The electron spin resonance spectrum of the heterojunction thin-film photocatalyst prepared in Example 2 is shown. In this spectrum, (A) represents hydroxyl radical •OH; and (B) represents superoxide radical •O2. - . Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0039] 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.
[0040] The technical solution of the present invention will be further described below through specific embodiments.
[0041] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.
[0042] The preparation flow chart of the heterojunction thin film photocatalyst of this invention is as follows: Figure 1 As shown, the ground bulk purple phosphorus was exfoliated by liquid-phase assisted ultrasonication, and then a solution of purple phosphorus nanosheets, denoted as VPNS, was obtained by two-stage centrifugation.
[0043] A ZnO seed layer was prepared on a flexible ITO-PEN substrate by electrochemical deposition using an aqueous solution of Zn(NO3)2·6H2O. A precursor solution was prepared by mixing Zn(NO3)2·6H2O and ammonia in a certain ratio. Then, a ZnO nanorod array layer was grown on the flexible ITO-PEN substrate containing the ZnO seed layer by hydrothermal method.
[0044] By immersing the grown ZnO nanorod array layer in a VPNS solution of a certain concentration using a self-adsorption method, and then drying it under an inert gas atmosphere, a purple phosphorus nanosheet / ZnO heterojunction thin film photocatalyst, denoted as VPNS / ZnO, can be obtained.
[0045] Example 1 A method for preparing a heterojunction thin-film photocatalyst includes the following steps: S1. Prepare a solution of blocky purple phosphorus and organic solvent at a mass-volume ratio of 1 mg / mL, seal and sonicate for 30 h, then centrifuge at 2000 rpm for 20 min to obtain VPNS, denoted as VPNS-1.
[0046] S2. An ITO-PEN substrate was immersed in an aqueous solution of Zn(NO3)2·6H2O and heated to 70°C in a water bath. A ZnO seed layer was prepared by electrochemical deposition on the flexible ITO-PEN substrate for 3 minutes. Then, a precursor solution was prepared by mixing Zn(NO3)2·6H2O, ammonia, and H2O in a mass ratio of 1:5:100 and stirring. A ZnO nanorod array layer was then obtained on the ITO-PEN substrate by hydrothermal deposition at 80°C for 12 hours. The product was denoted as ZnO.
[0047] S3. The ZnO nanorod array layer was immersed in VPNS solution for 3 hours, and then dried under an inert gas protective atmosphere at a temperature below 40°C to obtain the VPNS / ZnO heterojunction thin film photocatalyst, denoted as VPNS / ZnO-1.
[0048] Example 2 A method for preparing a heterojunction thin-film photocatalyst includes the following steps: S1. Prepare a solution of bulk purple phosphorus and organic solvent at a mass-volume ratio of 2 mg / mL, seal and sonicate for 30 h, then centrifuge at 2000 rpm for 20 min to obtain VPNS, denoted as VPNS-2.
[0049] S2. An ITO-PEN substrate was immersed in an aqueous solution of Zn(NO3)2·6H2O and heated in a water bath at 70°C to prepare a ZnO seed layer by electrochemical deposition on the flexible ITO-PEN substrate for 3 minutes. Then, a precursor solution was prepared by mixing Zn(NO3)2·6H2O, ammonia, and H2O in a mass ratio of 1:5:100 and stirring. A ZnO nanorod array layer was then obtained on the ITO-PEN substrate by hydrothermal deposition at 80°C for 12 hours. The product was denoted as ZnO.
[0050] S3. The ZnO nanorod array layer is immersed in VPNS solution for 3 hours, and then dried under an inert gas protective atmosphere at a temperature below 40°C to obtain VPNS / ZnO heterojunction thin film photocatalyst, denoted as VPNS / ZnO-2.
[0051] Example 3 A method for preparing a heterojunction thin-film photocatalyst includes the following steps: S1. Prepare a solution of blocky purple phosphorus and organic solvent at a mass-volume ratio of 4 mg / mL, seal and sonicate for 30 h, then centrifuge at 2000 rpm for 20 min to obtain VPNS, denoted as VPNS-3.
[0052] S2. An ITO-PEN substrate was immersed in an aqueous solution of Zn(NO3)2·6H2O and heated in a water bath at 70°C to prepare a ZnO seed layer by electrochemical deposition on the flexible ITO-PEN substrate for 3 min. Then, a precursor solution was prepared by mixing Zn(NO3)2·6H2O, ammonia, and H2O in a ratio of 1:5:100 and stirring. A ZnO nanorod array layer was then obtained on the ITO-PEN substrate by hydrothermal method at 80°C for 12 h. The product was denoted as ZnO.
[0053] S3. The ZnO nanorod array layer was immersed in VPNS solution for 3 hours, and then dried under an inert gas protective atmosphere at a temperature below 40°C to obtain the VPNS / ZnO heterojunction thin film photocatalyst, denoted as VPNS / ZnO-3.
[0054] Comparative Example 1 A method for preparing a ZnO nanorod array photocatalyst includes the following steps: A ZnO seed layer was prepared by electrochemical deposition on a flexible ITO-PEN substrate by immersing an ITO-PEN substrate in an aqueous Zn(NO3)2·6H2O solution and heating in a water bath at 70°C for 3 min. Then, a precursor solution was prepared by mixing Zn(NO3)2·6H2O, ammonia, and H2O at a mass ratio of 1:5:00 and stirring. A ZnO nanorod array layer was then obtained on the ITO-PEN substrate via a hydrothermal method at 80°C for 12 h, yielding the product, a ZnO nanorod array photocatalyst.
[0055] The heterojunction thin film photocatalysts prepared in Examples 1 to 3 of this invention and the ZnO nanorod array photocatalyst prepared in Comparative Example 1 were characterized in a series of ways, and the results are as follows: Figures 2-8 As shown.
[0056] Figure 2 TEM and HRTEM images of the heterojunction thin-film photocatalyst prepared in Example 2 are shown. The HRTEM results indicate that a plane spacing of 0.28 nm is typical of the (100) crystal plane of hexagonal zincblende ZnO. Furthermore, a plane spacing of 0.27 nm corresponds to the (127) crystal plane of VP. This demonstrates the successful preparation of the VPNS / ZnO heterojunction, with the VPNS tightly anchored to the surface of the ZnO nanorods, achieving a close interfacial relationship. This unique morphology of the heterojunction formed by VPNS on the surface of the ZnO nanorods is crucial for the separation and transport of photogenerated carriers.
[0057] Figure 3The image shows the elemental distribution of the heterojunction thin film photocatalyst prepared in Example 2. The elemental distribution further verifies the successful preparation of the VPNS / ZnO heterojunction.
[0058] Figure 4 The image shows the XRD pattern of the heterojunction thin film photocatalyst prepared in Example 2. In the VPNS / ZnO sample, 31.8°, 34.5°, 36.3°, 47.6°, 56.7°, 63.0°, 68.1° and 69.3° correspond to the (100), (002), (101), (102), (110), (103), (112) and (201) crystal planes of hexagonal wurtzite ZnO, respectively.
[0059] Figures 5-8 The diffuse reflectance, fluorescence spectrum, transient photocurrent response, and impedance spectrum of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1 are shown respectively. All of the above indicate that the visible light absorption capacity of the VPNS / ZnO heterojunction thin film photocatalyst is enhanced and the separation efficiency of photogenerated carriers is significantly improved.
[0060] The performance of the heterojunction thin film photocatalysts prepared in Examples 1 to 3 of this invention and the ZnO nanorod array photocatalyst prepared in Comparative Example 1 were tested, and the results are as follows: Figures 9-14 As shown.
[0061] Figure 9 The figures show the photocatalytic performance of the heterojunction thin-film photocatalysts prepared in Examples 1-3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1. Compared with the ZnO nanorod array photocatalyst in Comparative Example 1 without modification by purple phosphorus nanosheets, the VPNS / ZnO heterojunction in the heterojunction thin-film photocatalyst prepared in this invention improves the utilization rate of visible light, significantly enhancing the visible light absorption capacity, photogenerated carrier separation efficiency, and photocatalytic performance of the photocatalyst. Figure 9 The results show that the modified VPNS / ZnO heterojunction film photocatalyst exhibits excellent performance in the photocatalytic degradation of levofloxacin, with a degradation rate as high as 95.8%, which is much higher than the 58.9% of Comparative Example 1.
[0062] Figure 10The graph shows the reaction rate constants for the removal of levofloxacin by the heterojunction thin film photocatalysts prepared in Examples 1 to 3 and the ZnO nanorod array photocatalyst prepared in Comparative Example 1. The graph shows that the reaction rate constant of the VPNS / ZnO heterojunction thin film photocatalyst prepared in Example 2 is 0.0354, which is 3.58 times that of the unmodified ZnO nanorod array photocatalyst in Comparative Example 1 (0.0099). This indicates that the reaction rate of antibiotic removal by the VPNS / ZnO heterojunction thin film photocatalyst is significantly higher than that of the unmodified ZnO nanorod array photocatalyst in Comparative Example 1, and this improvement is reproducible.
[0063] Figure 11 and Figure 12 The graphs show the stability test of the heterojunction thin film photocatalyst prepared in Example 2, the selectivity test of different acid radical anions, and the degradation performance for different types of antibiotics. Figure 11 and Figure 12 This indicates that the VPNS / ZnO heterojunction thin film photocatalyst has good cycle stability and anti-interference ability.
[0064] Figure 13 The heterojunction thin film photocatalyst prepared in Example 2 exhibits good photocatalytic removal performance for various antibiotics. It can be seen that the VPNS / ZnO heterojunction thin film photocatalyst has good photocatalytic removal effect for a variety of antibiotics, showing good versatility.
[0065] Figure 14 The EPR signal of the heterojunction thin film photocatalyst prepared in Example 2 shows that the VPNS / ZnO heterojunction thin film photocatalyst has active free groups, which is an important guarantee for high photocatalytic performance.
[0066] In summary, this invention prepares purple phosphorus nanosheets via liquid-phase ultrasonic exfoliation, fabricates ZnO nanorod arrays on a flexible ITO-PEN substrate using a simple hydrothermal method, and prepares a VPNS / ZnO heterojunction thin-film photocatalyst through simple self-assembly. Utilizing the high visible light absorption and high carrier transport properties of VPNS to form a heterojunction with the ZnO nanorod array improves the utilization rate of visible light and significantly enhances the visible light absorption capacity and photogenerated carrier separation efficiency of the photocatalyst. The heterojunction thin-film photocatalyst prepared in this invention exhibits excellent catalytic efficiency and stability in the photocatalytic degradation of organic pollutants. Furthermore, the preparation method is simple and easy to recover, demonstrating significant practical application potential.
[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A heterojunction thin-film photocatalyst, characterized in that, The heterojunction thin-film photocatalyst is formed by sequentially depositing and growing a ZnO nanorod array layer and a purple phosphorus nanosheet layer in a vertical direction on the surface of a flexible substrate, with the ZnO nanorod array layer and the purple phosphorus nanosheet layer forming a pn-type heterojunction.
2. The heterojunction thin-film photocatalyst according to claim 1, characterized in that, The thickness of the ZnO nanorod array layer is 3 micrometers to 8 micrometers, and the thickness of the purple phosphorus nanosheet layer is 3 nanometers to 15 nanometers.
3. The heterojunction thin-film photocatalyst according to claim 1, characterized in that, The flexible substrate is a flexible indium tin oxide conductive film.
4. A method for preparing a heterojunction thin-film photocatalyst according to claim 1, characterized in that, Includes the following steps: ZnO seed layers were grown on a flexible substrate by electrochemical deposition using an aqueous solution of inorganic zinc salts; the flexible substrate containing the ZnO seed layers was placed in a precursor solution containing inorganic zinc salts and ammonia, and ZnO nanorod arrays were deposited and grown on the surface of the ZnO seed layers by hydrothermal reaction to form a ZnO nanorod array layer. A flexible substrate containing a ZnO nanorod array layer is placed in a purple phosphorus nanosheet solution. Purple phosphorus nanosheets are deposited on the surface of the ZnO nanorod array layer by self-adsorption, forming a purple phosphorus nanosheet layer. A pn-type heterojunction is formed between the ZnO nanorod array layer and the purple phosphorus nanosheet layer, resulting in a heterojunction thin film catalyst.
5. The method for preparing a heterojunction thin-film photocatalyst according to claim 3, characterized in that, The concentration of the purple phosphorus nanosheet solution is 0.1 mg / mL to 50 mg / mL; the concentration of the inorganic zinc salt aqueous solution is 5 mg / mL to 50 mg / mL.
6. The method for preparing a heterojunction thin-film photocatalyst according to claim 3, characterized in that, The inorganic zinc salt is Zn(NO3)2·6H2O; the mass ratio of ammonia to Zn(NO3)2·6H2O is 1 to 20:1; the concentration of Zn(NO3)2·6H2O in the precursor solution is 5 mg / mL to 50 mg / mL.
7. The method for preparing a heterojunction thin-film photocatalyst according to claim 3, characterized in that, The electrochemical deposition conditions are: temperature 50℃~80℃, deposition time 1min~10min; The conditions for the hydrothermal reaction are: temperature 60℃~100℃, reaction time 5h~15h.
8. The application of the heterojunction thin-film photocatalyst according to claim 1 in the photocatalytic removal of antibiotics from wastewater, characterized in that, The application method is as follows: the heterojunction thin film photocatalyst is placed in the test solution containing antibiotics, adsorbed in the dark for half an hour, and then irradiated under a 300W light source to achieve photocatalytic removal of antibiotics in the test solution; the antibiotic is levofloxacin.