Preparation of titanium dioxide composite metal polyphthalocyanine photocatalyst and method for synthesizing hydrogen peroxide by using titanium dioxide composite metal polyphthalocyanine photocatalyst

Abstract

The invention belongs to the technical field of photocatalysis, and particularly discloses a preparation method of a titanium dioxide composite metal polyphthalocyanine photocatalyst and a method for synthesizing hydrogen peroxide by the titanium dioxide composite metal polyphthalocyanine photocatalyst, and the preparation method comprises the following steps: weighing pyromellitic dianhydride, 2, 3-naphthalene dicarboxylic anhydride, chloride, urea, titanium dioxide and ammonium molybdate tetrahydrate, and transferring into a ceramic crucible; putting the ceramic crucible into a muffle furnace to obtain a crude product; extracting the obtained crude product; drying and ball-milling the product; a sample is weighed, treated by an ultrasonic cell disruptor and dried to obtain a final product. By adopting the preparation of the titanium dioxide composite polyphthalocyanine and the method for synthesizing hydrogen peroxide, the edge functionalized polyphthalocyanine composite material P25 (at) Zn-PPc-n chelated by TiO2 and metal sites is successfully synthesized, and the synthesized P25 (at) Zn-PPc-n is ensured to meet the condition of photocatalytic synthesis of H2O2.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photocatalysis, in particular to a preparation method of a titanium dioxide composite metal polyphthalocyanine photocatalyst and a method for synthesizing hydrogen peroxide by using the same. BACKGROUND

[0002] Phthalocyanine is a kind of planar aromatic macrocyclic compound with an 18-π electron system. Phthalocyanine has a stable structure, a clear M-N4 coordination structure, can be chelated with various metal sites, and provides a large number of active sites. In addition, the macrocyclic structure of phthalocyanine compounds can be regulated by modification or modification, thereby deriving a series of phthalocyanine-based covalent organic polymers. These materials have broad application prospects in the field of photocatalytic synthesis of hydrogen peroxide (H2O2). However, at present, there are very limited reports on the photocatalytic synthesis of H2O2 by using phthalocyanine-based covalent organic polymers (COPs). Therefore, in-depth research on phthalocyanine-based covalent organic polymers (COPs) with different topological structures has extremely important scientific significance and application value for promoting the development of this field.

[0003] Titanium dioxide (TiO2) is a common and typical N-type semiconductor material. It not only has reasonable energy band position, strong oxidizing property and high chemical stability, but also has the characteristics of non-toxicity, cleanliness and environmental protection. In addition, the preparation process of TiO2 is simple, and the cost is low, so it has broad application prospects in the field of photocatalysis. However, the band gap of TiO2 is wide, which leads to its low utilization rate of sunlight and can only be excited by ultraviolet light. At the same time, TiO2 also has the defects of high recombination rate of photo-generated electron-hole pairs and limited number of surface catalytic sites, which directly inhibits the improvement of its photocatalytic performance and limits its wide application in the field of photocatalysis. In contrast, phthalocyanine materials have suitable energy band structure and wide visible light absorption range, and their unique M-N4 structure allows metal elements to be coordinated at the center of the phthalocyanine macrocyclic skeleton, thereby enriching the number of surface active sites and improving the photocatalytic activity. Therefore, constructing a TiO2 composite with edge-functionalized polyphthalocyanine chelated with metal sites can not only enrich the surface active sites of the catalyst, but also improve the separation rate of photo-generated electron-hole pairs, which is an important way to solve the low yield of photocatalytic synthesis of hydrogen peroxide (H2O2).

[0004] The application successfully synthesizes an edge-functionalized polyphthalocyanine composite material P25@Zn-PPc-n chelated with TiO2 and metal sites, aiming to significantly improve the yield of polyphthalocyanine (PPc-n) in the process of photocatalytic synthesis of H2O2. In addition, a series of comparative materials are synthesized, and the performance of these materials in photocatalytic synthesis of H2O2 is systematically studied. Starting from two key factors of solution pH value and optical filter, the influence of the two factors on the performance of the catalyst in photocatalytic synthesis of H2O2 is further discussed. Through a series of detailed characterization methods and photoelectrochemical tests, it is confirmed that the composite material P25@Zn-PPc-n is successfully prepared, and the charge transfer characteristics, cycle stability and other key performances of the catalyst are further analyzed, and finally it is confirmed that the catalyst realizes the efficient photocatalytic synthesis of H2O2 through the redox reaction (ORR) mechanism. SUMMARY

[0005] The application aims to provide a preparation method of a titanium dioxide composite metal polyphthalocyanine photocatalyst and a method for synthesizing hydrogen peroxide, successfully synthesizes an edge-functionalized polyphthalocyanine composite material P25@Zn-PPc-n chelated with TiO2 and metal sites, and ensures that the synthesized P25@Zn-PPc-n meets the conditions for photocatalytic synthesis of H2O2.

[0006] To achieve the above-mentioned purpose, the application provides a preparation method of a titanium dioxide composite metal polyphthalocyanine photocatalyst, which comprises the following steps:

[0007] S1, weighing tetracarboxylic dianhydride, 2,3-naphthalene dicarboxylic dianhydride, chloride, urea, titanium dioxide and ammonium molybdate tetrahydrate, mixing uniformly in a mortar and grinding for 10 min, and then transferring the mixture to a ceramic crucible;

[0008] S2, placing the ceramic crucible in a muffle furnace, heating to 220℃ at a heating rate of 5℃ / min, and keeping at this temperature for 7h to obtain a crude product;

[0009] S3, placing the obtained crude product in a Soxhlet extractor and extracting using a mixed solvent;

[0010] S4, after the extraction is completed, placing the product in a vacuum drying box for drying overnight, and placing the dried sample in a ball mill tank containing zirconium dioxide balls, and ball milling at a speed of 500rpm for 6h;

[0011] S5, after the ball milling is completed, weighing the sample and dispersing it in deionized water, treating it with an ultrasonic cell crusher for 1h to realize uniform dispersion of the sample, centrifugally washing the solution treated by ultrasonic treatment for three times, and drying the washed sample in a vacuum drying box overnight to obtain a final product.

[0012] Preferably, in step S1, the chloride includes ammonium chloride and zinc chloride.

[0013] Preferably, in step S1, the titanium dioxide is nano-titanium dioxide P25.

[0014] Preferably, in step S3, the mixed solvent is a mixed solvent of water, ethanol and tetrahydrofuran, and the volume ratio of water, ethanol and tetrahydrofuran is 1:1:1.

[0015] Preferably, in step S5, the centrifugal washing uses an acetone solution.

[0016] The application also provides a titanium dioxide composite metal polyphthalocyanine photocatalyst prepared by the method for preparing the titanium dioxide composite metal polyphthalocyanine photocatalyst.

[0017] The application also provides a method for synthesizing hydrogen peroxide by using the titanium dioxide composite metal polyphthalocyanine photocatalyst, which is achieved by using the titanium dioxide composite metal polyphthalocyanine photocatalyst and includes the following steps:

[0018] At room temperature, the photocatalyst, deionized water and a sacrificial agent are uniformly dispersed in a glass photocatalytic reactor, O2 is introduced into the solution at a flow rate of 300 mL / min under dark conditions, and stirring is continued for 30 min to achieve O2 adsorption-desorption equilibrium, and a xenon lamp is used to irradiate the solution to generate hydrogen peroxide.

[0019] Preferably, the sacrificial agent is ethanol.

[0020] The application has the following advantages and beneficial effects by using the above-mentioned method for preparing the titanium dioxide composite metal polyphthalocyanine photocatalyst and the method for synthesizing hydrogen peroxide by using the titanium dioxide composite metal polyphthalocyanine photocatalyst.

[0021] 1. A series of edge-functionalized polyphthalocyanine materials are obtained by introducing different edge-functionalized substituents, and the efficiency of photocatalytic synthesis of hydrogen peroxide is improved by edge-functionalizing the polyphthalocyanine, and on this basis, a modified strategy of doping metal Zn and compounding with semiconductor material nano-titanium dioxide P25 is adopted, and a catalyst P25@Zn-PPc-n is successfully prepared, and the photocatalytic performance of the material is further optimized by ball milling and cell crushing and other treatment methods. The synthesized material meets the expected target in structure and function, and lays a solid foundation for subsequent photocatalytic performance test.

[0022] 2. Under the condition that ethanol is used as a sacrificial agent, the yield of P25@Zn-PPc-n photocatalytic synthesis of H2O2 is significantly improved compared with the yield of polyphthalocyanine photocatalytic synthesis of H2O2, which proves the success of the modified strategy of doping metal Zn and compounding with semiconductor material P25.

[0023] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 are structural diagrams of P25@Zn-PPc-n of the present application, wherein (a) is an XRD diagram, (b) is an FT-IR diagram, and (c) is a Raman diagram;

[0025] Figure 2 are SEM diagrams of different sizes of P25@Zn-PPc-n of the present application, wherein (a) is 200 nm, and (b) is 2 μm;

[0026] Figure 3 are N2 adsorption-desorption isotherms and pore size distribution diagrams of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n of the present application, wherein (a) is an isotherm of Zn-PPc-n, (b) is a pore size distribution diagram of Zn-PPc-n, (c) is an isotherm of P25@PPc-n, (d) is a pore size distribution diagram of P25@PPc-n, (e) is an isotherm of P25@Zn-PPc-n, and (f) is a pore size distribution diagram of P25@Zn-PPc-n;

[0027] Figure 4 are XPS energy spectrum diagrams of Zn-PPc-n of the present application, wherein (a) is C1s, (b) is N1s, (c) is O1s, and (d) is Zn 2p;

[0028] Figure 5 are XPS energy spectrum diagrams of P25@Zn-PPc-n of the present application, wherein (a) is C1s, (b) is N1s, (c) is O1s, and (d) is Zn 2p;

[0029] Figure 6 are TGA diagrams of Zn-PPc-n and P25@Zn-PPc-n of the present application;

[0030] Figure 7 are UV-vis DRS diagrams and Tauc diagrams of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n of the present application, wherein (a) is a UV-vis DRS diagram of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n, (b) is a Tauc diagram of Zn-PPc-n, (c) is a Tauc diagram of P25@PPc-n, and (d) is a Tauc diagram of P25@Zn-PPc-n;

[0031] Figure 8 are PL spectrum diagrams of P25@Zn-PPc-n, Zn-PPc-n, and PPc-n of the present application;

[0032] Figure 9are EIS and TPC test figures of Zn-PPc-n, P25@PPc-n, P25@Zn-PPc-n of the application, wherein (a) is an EIS figure, (b) is a TPC figure;

[0033] Figure 10 are Mott-Schottky figures of Zn-PPc-n, P25@PPc-n, P25@Zn-PPc-n of the application, wherein (a) is Zn-PPc-n, (b) is P25@PPc-n, (c) is P25@Zn-PPc-n;

[0034] Figure 11 are band structure schematic diagrams of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n of the application;

[0035] Figure 12 are EIS and TPC test figures of Zn-PPc-n, P25@PPc-n, P25@Zn-PPc-n of the application, wherein (a) is an EIS figure, (b) is a TPC figure;

[0036] are performance and yield comparison figures of P25@Zn-PPc-n for photocatalytic synthesis of H2O2, wherein (a) is a performance comparison figure, (b) is a yield comparison figure;

[0037] Figure 13 are photocatalytic degradation performance test figures of PPc-n and P25@Zn-PPc-n of the application on H2O2 under light and oxygen-free (argon gas passed) conditions, wherein (a) is a photocatalytic degradation figure of PPc-n and P25@Zn-PPc-n on H2O2 under light and oxygen-free conditions; (b) is a photocatalytic cycle experiment figure of P25@Zn-PPc-n; (c) is a yield comparison figure of P25@Zn-PPc-n for photocatalytic synthesis of H2O2 under the action of different quenching agents;

[0038] Figure 14 are performance and yield comparison figures of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n of the application for photocatalytic synthesis of H2O2 under the condition of ethanol as a catalyst and without a 400 nm filter, wherein (a) is a performance comparison figure, (b) is a yield comparison figure;

[0039] Figure 15 are performance and yield comparison figures of P25@Zn-PPc-n of the application for photocatalytic synthesis of H2O2 in different pH environments under the premise of ethanol as a catalyst and without a 400 nm filter, wherein (a) is a performance comparison figure, (b) is a yield comparison figure;

[0040] Figure 16 are EPR figures of P25@Zn-PPc-n of the application under dark conditions and when light is irradiated for 5 min.

[0041] Figure 17 is the RDE test curve of P25@Zn-PPc-n of the present application, wherein (a) is the LSV curve, and (b) is the Koutecky-Levich curve at a potential of -0.4 V. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further described below by means of the accompanying drawings and examples.

[0043] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application belongs.

[0044] Unless otherwise defined, the reagents, devices and other materials used in the present application are all obtained from conventional commercial sources.

[0045] Example 1

[0046] The preparation method of the metal polyphthalocyanine (Zn-PPc-n) photocatalyst comprises the following steps:

[0047] S1, weigh phthalic anhydride (0.87 g), 2,3-naphthalene dicarboxylic anhydride (0.2 g), ammonium chloride (0.5 g), urea (2.05 g), zinc chloride (0.6 g), and ammonium molybdate tetrahydrate (12.5 mg), mix them uniformly in a mortar and grind for 10 min, and then transfer the mixture to a ceramic crucible.

[0048] S2, place the ceramic crucible into a muffle furnace, heat it to 220°C at a heating rate of 5°C / min, and keep it at this temperature for 7 h to obtain a crude product.

[0049] S3, place the obtained crude product into a Soxhlet extractor, use a mixed solvent of water, ethanol and tetrahydrofuran (volume ratio of 1:1:1, each 60 mL) for extraction, and the extraction temperature is 120°C, and the extraction lasts for 48 h.

[0050] S4, after the extraction is completed, place the product in a vacuum drying oven at 70°C and dry it overnight, and then place the dried sample into a ball mill jar containing zirconium dioxide balls, and place the ball mill jar into a planetary ball mill, and ball mill it at a speed of 500 rpm for 6 h.

[0051] S5, after the ball milling is completed, weigh 0.2 g of the sample and disperse it in 15 mL of deionized water, and use an ultrasonic cell crusher to treat it for 1 h to achieve uniform dispersion of the sample. Then, centrifugally wash the ultrasonic treated solution three times (use acetone solution for the washing operation). Finally, place the washed sample again in a vacuum drying oven at 70°C and dry it overnight to obtain the final product.

[0052] A method for preparing a titanium dioxide composite polyphthalocyanine (P25@PPc-n) photocatalyst, comprising the following steps:

[0053] A certain amount of pyromellitic dianhydride (0.87 g), 2,3-naphthalene dicarboxylic anhydride (0.2 g), ammonium chloride (0.5 g), urea (2.05 g), nano-titanium dioxide P25 (10 mg), and ammonium molybdate tetrahydrate (12.5 mg) were mixed uniformly in a mortar and ground for 10 min, and then the mixture was transferred to a 50 mL ceramic crucible. The remaining steps were the same as those in the preparation method of Zn-PPc-n, and are not described herein.

[0054] A method for preparing a titanium dioxide composite metal polyphthalocyanine (P25@Zn-PPc-n) photocatalyst, comprising the following steps:

[0055] A certain amount of pyromellitic dianhydride (0.87 g), 2,3-naphthalene dicarboxylic anhydride (0.2 g), ammonium chloride (0.5 g), urea (2.05 g), nano-titanium dioxide P25 (10 mg), and ammonium molybdate tetrahydrate (12.5 mg) were mixed uniformly in a mortar and ground for 10 min, and then the mixture was transferred to a 50 mL ceramic crucible. The remaining steps were the same as those in the preparation method of Zn-PPc-n, and are not described herein.

[0056] A method for synthesizing hydrogen peroxide by using a titanium dioxide composite metal polyphthalocyanine photocatalyst, comprising the following steps:

[0057] At room temperature, 10 mg of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n photocatalysts were uniformly dispersed in a glass photocatalytic reactor with 20 ml of deionized water and 10 ml of a sacrificial agent (ethanol). O2 was introduced into the solution at a flow rate of 300 mL / min under dark conditions at a pH value of 3, and stirring was continued for 30 min to achieve O2 adsorption-desorption equilibrium. A xenon lamp was used to irradiate the solution to generate hydrogen peroxide.

[0058] Test example

[0059] The Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n photocatalysts prepared in Example 1 were tested and characterized.

[0060] 1. Test method

[0061] X-ray diffraction (XRD) was tested by using a D8 Advance X-ray diffractometer, and the specific experimental conditions were as follows: a Cu Kα diffraction target was used, the X-ray wavelength was The scanning range was 2θ = 10°-60°, the working voltage was 40 kV, the current was 40 mA, and the scanning speed was 10° min -1 .

[0062] Scanning electron microscopy (SEM) was used to characterize the morphology of the samples using a JSM-5610LV scanning electron microscope to further explore the microstructure characteristics.

[0063] Fourier transform infrared spectroscopy (FT-IR) was used to accurately analyze the chemical and physical properties of the samples using a Nicolet iS50 Fourier transform infrared spectrometer. Its high resolution and high sensitivity can also accurately provide detailed information about the molecular structure of the material, providing strong support for a deep understanding of the chemical nature and physical behavior of the sample.

[0064] Raman spectroscopy (Raman) was used to quantitatively analyze specific components in the sample using an ATR3000 Raman spectrometer, and to assist in identifying key information such as chemical components and functional groups in the sample, providing accurate spectral data support for the study.

[0065] Thermogravimetric analysis (TGA) was used to evaluate the thermal stability of the synthesized polymer using a Pyris Diamond TGA thermogravimetric analyzer to accurately characterize its thermal behavior and performance at different temperatures.

[0066] X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical composition, valence state, and electronic structure of the material surface using a Nexsa X-ray photoelectron spectrometer with excellent performance, and further explored the catalytic activity of the material, providing key information for understanding its surface chemical behavior.

[0067] BET specific surface area testing method was used to test the specific surface area and pore size of the sample using a 3H-2000PS1 specific surface area and pore size analyzer. The test conditions were as follows: the sample was pretreated at 120°C in a high vacuum environment for 8h to remove surface adsorbed impurities; then N2 physical adsorption-desorption test was carried out at 77K. This test provides strong support for a deep understanding of the microstructure of the sample.

[0068] Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was used to accurately analyze the ultraviolet and visible light absorption characteristics of the samples using a U-3900 ultraviolet-visible diffuse reflectance spectrometer. Through this instrument, not only can the photocatalytic activity of the sample be determined, but also the band gap of the semiconductor material can be calculated using the diffuse reflectance spectrum data, thereby providing a theoretical basis for optimizing the photocatalytic performance of the material.

[0069] Ultraviolet-visible spectrophotometer (UV-Vis Spectrophotometer, UV) was used to characterize the absorbance of the sample using a UH4150 ultraviolet-visible spectrophotometer, and the test wavelength range was 300-500 nm.

[0070] Steady-state and transient fluorescence spectrometer was used to measure and analyze the excitation spectrum and emission spectrum of the sample in detail using a FLS980 steady-state and transient fluorescence spectrometer.

[0071] Electron paramagnetic resonance spectrometer (Electron Paramagnetic Resonance Spectrometer, EPR) was used to detect superoxide free radicals (·O2 - ) in the sample using an EPR200M paramagnetic resonance spectrometer. The free radical trapping agent selected in the experiment was 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), which reacted with superoxide free radicals to form stable adducts, thereby achieving efficient detection of superoxide free radicals.

[0072] Electrochemical testing was performed using a CHI660E electrochemical workstation using a three-electrode system. 2 mg of catalyst was dispersed by ultrasonic dispersion (30 min) in 1 mL of ethanol solution containing Nafion perfluorinated resin (5 wt%, 50 μL). Subsequently, 100 μL of the mixed solution was evenly dropped on a fluorine-doped tin oxide (FTO, 1 cm x 1 cm) glass electrode, which was dried at room temperature and used as the working electrode. In the experiment, a Hg / HgCl2 electrode was used as the reference electrode, and a platinum sheet electrode was used as the counter electrode. The electrolyte was a 0.1 mol·L -1 of Na2SO4 solution. The light source was a 300W xenon lamp (equipped with a 400nm cutoff filter).

[0073] Determination of H2O2 concentration: The concentration of H2O2 was detected by iodometric method. The specific operation is as follows: 1 mL of reaction solution was mixed with 0.5 mL of KI solution with a concentration of 0.4 mol L-1and 0.5 mL of potassium hydrogen phthalate solution with a concentration of 0.1 mol L-1, and was placed for 30 min. Under acidic conditions, H2O2 molecules react with iodine ions to form triiodide ions, which exhibit significant absorption characteristics at 350 nm. The concentration of triiodide ions was determined by UV-visible spectroscopy, and the amount of H2O2 generated in the photocatalytic process was calculated.

[0074] In addition, a series of H2O2 standard solutions with known concentrations were also detected by iodometric method, and a standard curve of H2O2 concentration and absorbance was drawn accordingly. The H2O2 concentration and absorbance showed a good linear relationship, which was fitted as follows:

[0075] Y = 144.66319X - 2.9272

[0076] where X is the absorbance value at 350 nm, and Y is the H2O2 concentration (μmol L -1 ). Based on this standard curve, the concentration of H2O2 in the sample solution can be accurately calculated by measuring the absorbance.

[0077] The cyclic stability test of H2O2 was carried out under the same photocatalytic reaction conditions. First, 10 mg of catalyst was accurately weighed and added to a glass photocatalytic reactor containing 30 mL of deionized water, and the experiment was repeated according to the photocatalytic H2O2 generation experiment method. After each round of photocatalytic reaction, the reaction solution was transferred to a clean centrifuge tube and centrifuged at 10000 rpm for 5 min. Then, the catalyst separated by centrifugation was placed in a vacuum drying oven at 70°C and dried overnight. After drying, the appropriate amount of new catalyst was added to restore the total amount to 10 mg. The above operation was repeated for 4 times, and a series of photocatalytic reaction solutions were obtained. Finally, the concentration of H2O2 in these photocatalytic reaction solutions was detected by iodometric method.

[0078] H2O2 degradation experiment: The H2O2 degradation performance of the catalyst under visible light irradiation was further explored using a 500 μmol·L-1 H2O2 solution. In the experiment, 10 mg of the catalyst was added to a glass photocatalytic reactor containing 30 mL of a 500 μmol·L-1 H2O2 solution. First, in the dark, the system was thoroughly stirred by argon bubbling for 1 h to completely remove O2. Subsequently, the reaction system was irradiated using a 300 W xenon lamp equipped with a 400 nm filter. During the irradiation, 1 mL of the reaction solution was sampled every 20 min, for a total of 4 samples. Finally, the H2O2 concentration in the photocatalytic reaction solution was accurately detected using the iodometric method to evaluate the degradation efficiency of the catalyst.

[0079] Quenching experiment: Before carrying out the photocatalytic reaction, different types of quenchers (concentration of 0.1 mmol·L-1) were added to the solution to carry out systematic quenching experiments. Among them, p-benzoquinone (p-BQ) was used to quench superoxide radicals, and potassium bromate (KBrO3) was used to quench electrons (e - )·-.

[0080] 2. Structure and characterization of photocatalyst.

[0081] The crystal structures of Zn-PPc-n, nano-titanium dioxide P25, and P25@Zn-PPc-n were characterized in detail using X-ray diffraction (XRD) technology, and their XRD patterns were compared with that of PPc-n (a). Figure 1 The XRD results showed that Zn-PPc-n, nano-titanium dioxide P25, and P25@Zn-PPc-n all exhibited good crystallinity. Compared with PPc-n, the intensity of the main peak position of Zn-PPc-n and P25@Zn-PPc-n significantly decreased, and two new strong diffraction peaks appeared near 12° and 24°. This phenomenon clearly confirmed that metal Zn had successfully doped into the macrocyclic framework structure of polyphthalocyanine and did not destroy the original π-π stacking crystal structure of polyphthalocyanine. Further comparison of the XRD patterns of nano-titanium dioxide P25 and P25@Zn-PPc-n found that the characteristic diffraction peaks of nano-titanium dioxide P25 were almost invisible in the pattern of P25@Zn-PPc-n, which was probably due to the low content of nano-titanium dioxide P25 in the composite material.

[0082] The structures of PPc-n, P25@PPc-n, and P25@Zn-PPc-n were characterized and analyzed using Fourier transform infrared spectroscopy (FT-IR) technology. Figure 1(b). These materials exhibit similar infrared absorption peaks, indicating that neither the doping of metal Zn nor the compounding with nano-titania P25 has destroyed the macrocyclic framework structure of polyphthalocyanine. Specifically, the absorption peaks at 1610 cm -1 , 1510 cm -1 and 1330 cm -1 are attributed to the characteristic vibrations of the macrocyclic framework of polyphthalocyanine; the absorption peaks at 1290 cm -1 and 1170 cm -1 are due to the stretching vibrations of C-N bonds. In addition, the absorption peaks in the range of 400-800 cm -1 for P25@PPc-n and P25@Zn-PPc-n can be attributed to the characteristic vibrations of Ti-O-Ti bonds in nano-titania P25; while the absorption peak at 912 cm -1 for P25@Zn-PPc-n is due to the coordination vibration between metal Zn and polyphthalocyanine. The presence of these characteristic absorption peaks strongly proves the successful synthesis of P25@PPc-n and P25@Zn-PPc-n.

[0083] In addition, Raman characterization further verifies the above conclusion Figure 1 (c). Compared with PPc-n, P25@Zn-PPc-n shows similar A -1 peaks near 685 cm -1 , 1130 cm -1 and 1335 cm 1g , similar B -1 peaks near 747 cm 1g , and similar B -1 peaks near 1450 cm 2g . Although the intensities of these characteristic peaks are slightly reduced, and the positions of some subtle peaks are slightly shifted, these changes can be due to the doping of metal Zn and the compounding with nano-titania P25. These characteristic peaks are all derived from the in-plane vibrations of the phthalocyanine macrocyclic structure, indicating that P25@Zn-PPc-n, like PPc-n, retains the intact phthalocyanine macrocyclic framework structure.

[0084] Figure 2The scanning electron microscope (SEM) images of the composite P25@Zn-PPc-n are shown. It can be clearly observed from the images that P25@Zn-PPc-n presents a larger size flake-like stacked graphenelike structure similar to that of PPc-n, and agglomerated nano-titanium dioxide P25 nanoparticles can be obviously seen on the surface thereof. This result shows that the doping of metal Zn does not destroy the original morphology of PPc-n, and the nano-titanium dioxide P25 has been successfully composited with Zn-PPc-n. In addition, similar to PPc-n, the thickness of P25@Zn-PPc-n is low. This shows that during the synthesis of P25@Zn-PPc-n, after treatment by ball milling and ultrasonic and the like, the thickness thereof is significantly thinned. This treatment mode can effectively expose the active sites of the catalyst, thereby significantly improving the photocatalytic activity of P25@Zn-PPc-n.

[0085] The BET specific surface area and pore size distribution information of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n were obtained by N2adsorption-desorption isotherm analysis.

[0086] The BET specific surface area test method is to use a 3H-2000PS1 type specific surface area and pore size analyzer to test the specific surface area and pore size of the sample. The test conditions are: the sample is pretreated at 120°C in a high vacuum environment for 8h to remove the adsorbed impurities on the surface; and then N2physical adsorption-desorption test is carried out at 77K. This test provides strong support for in-depth understanding of the microstructure of the sample.

[0087] As shown in Figure 3 , the three materials all present typical IV-type adsorption isotherms, indicating that they are all mesoporous materials. Calculation shows that the BET specific surface areas of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n are 9.36m 2 g -1 , 7.15m 2 g -1 and 7.7m 2 g -1 , respectively. Further analysis of the pore size distribution graph shows that their average pore sizes are 15.12nm, 18.74nm and 16.89nm, respectively. Compared with PPc-n, the BET specific surface area and average pore size of P25@Zn-PPc-n are both smaller, which may be due to the doping of metal zinc and the composite effect of P25, causing the original pores of PPc-n to be partially blocked.

[0088] The material composition of Zn-PPc-n and P25@Zn-PPc-n was characterized in detail by XPS analysis, and the results are shown in Figure 4 and Figure 5The doping of metal Zn and the compounding with nano-titania P25 did not destroy the original polyphthalocyanine network and did not affect its core structure. Further, the carbon spectrum of Zn-PPc-n and P25@Zn-PPc-n was peak processed Figure 4 in (a) and Figure 5 in (a)). The comparative results show that the bond energy of C=C, C-NHx, N-C=N and π-π* of P25@Zn-PPc-n is obviously negatively shifted compared with Zn-PPc-n, which indicates that the polyphthalocyanine network has strong electronic affinity.

[0089] The nitrogen spectrum of Zn-PPc-n and P25@Zn-PPc-n was peak processed Figure 4 in (b) and Figure 5 in (b)). The results show that the bond energy of C=N and N-C of P25@Zn-PPc-n is lower than that of Zn-PPc-n, which further proves that the polyphthalocyanine network after compounding with nano-titania P25 can attract more electrons. In addition, after the oxygen spectrum of Zn-PPc-n and P25@Zn-PPc-n is peak processed Figure 4 in (c) and Figure 5 in (c)), it is found that the bond energy of O-C and O=C of P25@Zn-PPc-n is reduced, which indicates that the electron density of oxygen atom increases after compounding with nano-titania P25, so that P25@Zn-PPc-n is more easily adsorbed O2 than Zn-PPc-n, thereby promoting the progress of photocatalytic reaction.

[0090] Finally, the zinc spectrum of Zn-PPc-n and P25@Zn-PPc-n was peak processed Figure 4 in (d) and Figure 5 in (d)). By comparing the Zn 2p 3 / 2 bond energy of the two materials, it is found that it rises from 1021.5 eV to 1022.47 eV. This result shows that after compounding with P25, the metal Zn located in the center of the phthalocyanine macrocycle framework provides more electrons to the polyphthalocyanine network, thereby facilitating the improvement of the photocatalytic activity of the catalyst.

[0091] Through TGA analysis, the thermal stability and decomposition characteristics of Zn-PPc-n and P25@Zn-PPc-n were evaluated. As Figure 6As shown, both materials exhibit good thermal stability when heated to 350℃ under a nitrogen atmosphere. Zn-PPc-n shows a weight loss of 9.17% at 350℃, while P25@Zn-PPc-n shows a weight loss of 10.91% at the same temperature. Although the weight loss of P25@Zn-PPc-n is slightly higher than that of Zn-PPc-n, it still exhibits high thermal stability at 350℃. This excellent thermal stability is crucial for the photocatalytic process because it ensures that P25@Zn-PPc-n does not undergo photothermal decomposition under xenon lamp irradiation, thus avoiding a decrease in photocatalytic efficiency due to material decomposition.

[0092] 3. Research on the performance of photocatalytic materials.

[0093] By calculating and analyzing the UV-Vis diffuse reflectance spectra (UV-Vis DRS) and Tauc plots, the light-harvesting capabilities and bandgap characteristics of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n were clarified. Figure 7 As shown in (a), all three materials exhibit a wide light absorption range, and the absorbance of the catalyst is significantly improved after doping with metallic Zn. Furthermore, based on the Kubelka-Munk equation (αhv=A(hv-Eg)...), 2 The calculated Tauc plot ( Figure 7 Images (b), (c), and (d) clearly reveal their band gap characteristics. The band gap energy (Eg) of Zn-PPc-n is 2.16 eV, that of P25@PPc-n is 1.97 eV, and that of P25@Zn-PPc-n is 2.06 eV. Compared to PPc-n, these materials have smaller band gap energies, which are more conducive to the transfer of photogenerated electrons. This characteristic greatly promotes the photocatalytic synthesis of H2O2 and significantly improves the photocatalytic yield of the catalyst.

[0094] The separation efficiency of photogenerated electron-hole pairs in Zn-PPc-n and P25@Zn-PPc-n was investigated in depth using photoluminescence (PL) spectroscopy. Figure 8As shown, the PL signal peak intensity of P25@Zn-PPc-n is significantly lower than that of PPc-n. The intensity of the PL signal peak is closely related to the recombination rate of photo-generated carriers in the catalyst: the stronger the signal peak, the easier the photo-generated carriers recombine; while the weaker the signal peak, the lower the recombination rate of the photo-generated carriers, and the higher the separation efficiency. Therefore, P25@Zn-PPc-n exhibits a higher separation efficiency of photo-generated electron-hole pairs than PPc-n. Notably, Zn-PPc-n exhibits the lowest PL signal peak intensity, which can be attributed to the π-π stacking between the catalyst molecules. These results show that the polyphthalocyanine material after doping with metal Zn and compounding with P25 can significantly inhibit the recombination of photo-generated carriers, thereby effectively improving its photocatalytic efficiency for synthesizing H2O2, making P25@Zn-PPc-n exhibit a higher yield in the photocatalytic reaction.

[0095] As Figure 9 As shown in (a) and (b), the separation efficiency of photo-generated carriers of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n was further investigated by using two testing methods, electrochemical impedance spectroscopy (EIS) and thermogravimetric method programmed current analysis (TPC), and the activity of these three materials in the photocatalytic synthesis of H2O2 reaction was further evaluated. The EIS test results show that P25@Zn-PPc-n has a smaller circular arc radius than P25@PPc-n, which indicates that P25@Zn-PPc-n has a lower charge transfer resistance. Therefore, the interface electron transfer rate of P25@Zn-PPc-n is significantly higher than that of P25@PPc-n. In addition, Zn-PPc-n has the lowest circular arc radius, which is also attributed to the ordered π-π stacking between the catalyst molecules. Zn-PPc-n has lower water solubility and a tendency to agglomerate, which will hinder the generation of photocatalytic H2O2, so P25@Zn-PPc-n is more suitable for the photocatalytic synthesis of H2O2 reaction than Zn-PPc-n. The TPC test results also clearly show that the photocurrent intensity of P25@Zn-PPc-n is significantly higher than that of Zn-PPc-n and P25@PPc-n, which further confirms that P25@Zn-PPc-n has a lower recombination rate of photo-generated electron-hole pairs. In summary, it can be concluded that the polyphthalocyanine material after doping with metal Zn and compounding with nano-titanium dioxide P25 can significantly inhibit the recombination of photo-generated carriers, thereby effectively improving its photocatalytic efficiency for synthesizing H2O2. This result reveals that doping with metal and compounding with other semiconductors can effectively improve the photocatalytic performance of polyphthalocyanine materials, and exhibit excellent photocatalytic activity.

[0096] Figure 10(a), (b), and (c) show the Mott-Schottky spectra of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n, respectively. Using these curves, the flat-band potentials of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n were determined to be -0.75V, -0.53V, and -0.73V, respectively. Since a saturated calomel electrode (SCE) was used, the electrode potential conversion formula (E0) can be further utilized. NHE =E SCE The CB positions of PPc-p and PPc-n are estimated using +0.2V (NHE is a general hydrogen electrode) and are -0.55V, -0.33V, and -0.53V, respectively. Further, according to formula E... g =E VB -E CB The VB positions of Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n can be calculated to be 1.61V, 1.64V, and 1.53V, respectively.

[0097] like Figure 11 As shown, the band structure of P25@PPc-n barely satisfies the requirement of converting O2 into ·O2. - Thermodynamic conditions, and the band structures of these three materials all satisfy the thermodynamic conditions of ORR (E O2 / H2O2 =0.68V vs. NHE), therefore, Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n can all achieve photocatalytic synthesis of H2O2 via the ORR process. Specifically, ethanol is used as a sacrificial agent, and the redox potential (E) of ethanol oxidation is specifically indicated. C2H5OH / CH3CHO = -0.21V vs. NHE).

[0098] The performance of synthesized Zn-PPc-n, P25@PPc-n, and P25@Zn-PPc-n in the photocatalytic synthesis of H2O2 was systematically studied, and the results are as follows: Figure 12(a) and (b). Three groups of photocatalytic experiments were designed and implemented, and their results were compared with the photocatalytic synthesis of H2O2 performance of PPc-n. During the experiment, 10 mg of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n were weighed respectively, which were dispersed in 30 mL of solution (prepared by 10 mL of ethanol and 20 mL of water), and the experiment of photocatalytic synthesis of H2O2 was carried out. The experimental results clearly show that Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n all exhibit significantly better performance than PPc-n in photocatalytic synthesis of H2O2. Among them, P25@Zn-PPc-n shows the highest photocatalytic synthesis of H2O2 activity. After 100 min of light, the photocatalytic synthesis of H2O2 yield of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n is 241.33 μmol g -1 h-1, 287.15 μmol g -1 h-1 and 315.79 μmol g -1 h-1, respectively. Compared with the photocatalytic synthesis of H2O2 performance of PPc-n (174.15 μmol g -1 h-1), the photocatalytic synthesis of H2O2 yield of P25@Zn-PPc-n is significantly improved by 81.33%. Based on the above results, under the condition of using ethanol as a sacrificial agent, it is not only successfully proved that the strategy of doping metal Zn and compounding with semiconductor material nano-titanium dioxide P25 can significantly improve the photocatalytic performance of the material, but also further verifies the feasibility of chemical modification of polyphthalocyanine structure to enhance its photocatalytic activity.

[0099] The photocatalytic degradation performance of P25@Zn-PPc-n on H2O2 under light and oxygen-free (argon gas) conditions was compared with that of PPc-n, and the results are shown in Figure 13 (a). As can be seen from the figure, after 80 min of light, the degradation rate of P25@Zn-PPc-n and PPc-n on H2O2 is low, both less than 20%. It is worth noting that the degradation rate of P25@Zn-PPc-n is significantly lower than that of PPc-n. This result shows that in the process of photocatalytic synthesis of H2O2, the degradation of P25@Zn-PPc-n on H2O2 is weaker than that of PPc-n, so it will not significantly affect the photocatalytic yield of H2O2.

[0100] The cyclic stability of P25@Zn-PPc-n was explored, and the results are shown in Figure 13The results show that the H2O2 production rates of the four groups of experiments are basically consistent, and the H2O2 production rate of the fourth group of experiments only decreases by 3.11% compared with that of the first group of experiments. This result fully indicates that P25@Zn-PPc-n has high photocatalytic stability and can maintain high H2O2 production rate in multiple cycles.

[0101] A series of quenching experiments were carried out on the P25@Zn-PPc-n catalyst to further explore the ORR pathway involved in the photocatalytic synthesis of H2O2. The results are shown in Figure 13 (c).

[0102] In the experiment, when KBrO3 (an electron quencher) and p-BQ (·O2 - quencher) were added to the reaction system respectively, the photocatalytic synthesis H2O2 production rate of P25@Zn-PPc-n decreased by 65.22% and 28.69% respectively. This phenomenon shows that photo-excited electrons play a crucial role in the photocatalytic synthesis of H2O2. In addition, when no ethanol is added as a sacrificial agent, the photocatalytic synthesis H2O2 production rate of P25@Zn-PPc-n decreases significantly by 84.35%, which further highlights the importance of ethanol as a sacrificial agent in the process of photocatalytic synthesis of H2O2. In summary, the above results can confirm that P25@Zn-PPc-n mainly realizes the photocatalytic synthesis of H2O2 through the ORR pathway.

[0103] Further, the effect of the optical filter (400 nm) on the photocatalytic synthesis of H2O2 of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n was studied. As shown in Figure 14 (a) and (b), after removing the optical filter, the photocatalytic synthesis of H2O2 experiments were carried out on the three materials respectively. The results show that after removing the optical filter, the photocatalytic synthesis of H2O2 performance of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n is significantly improved. After 100 min of light irradiation, the photocatalytic synthesis H2O2 production rate of Zn-PPc-n, P25@PPc-n and P25@Zn-PPc-n reaches 751.44 μmol g -1 h-1, 803.51 μmol g -1 h-1 and 872 μmol g -1h-1. Compared with the use of a 400 nm filter, the photocatalytic H2O2 synthesis yields of these three materials increased by 2.11 times, 1.80 times, and 1.76 times, respectively. These results fully demonstrate that expanding the light absorption range can significantly improve the photocatalytic H2O2 synthesis yield. In particular, the nano-titanium dioxide P25 composite catalyst P25@Zn-PPc-n, excited only by ultraviolet light, exhibited the highest photocatalytic H2O2 synthesis activity after the filter was removed.

[0104] The effect of acidic pH environment on the photocatalytic synthesis of H2O2 by P25@Zn-PPc-n is shown in the following results. Figure 15 As shown in (a) and (b), solutions with pH values ​​of 4, 3.5, 3, and 2.5 were prepared under conditions of ethanol as a sacrificial agent and without a 400 nm filter, and experiments were conducted on the photocatalytic synthesis of H2O2. The experimental results showed that under strongly acidic conditions (pH = 2.5), the photocatalytic synthesis of H2O2 by P25@Zn-PPc-n was almost completely inhibited; after 100 min of irradiation, the yield of H2O2 was only 26.5 μmol g. - 1 h-1. Under pH conditions of 4 and 3.5, the photocatalytic synthesis performance of H2O2 from P25@Zn-PPc-n was not improved, and the H2O2 yield after 100 min of illumination was 711.34 μmol g. -1 h-1 and 782.42 μmol g -1 h-1. The performance under these two conditions was slightly lower than that under the original conditions. This may be due to experimental errors, or the weakly acidic environment may have a slight inhibitory effect on the photocatalytic activity of P25@Zn-PPc-n. However, when the pH value was 3, the photocatalytic activity of P25@Zn-PPc-n was significantly improved, and the yield of H2O2 reached 1031.09 μmol g after 100 min of illumination. -1 The pH value was 1 h-1, which was 18.24% higher than the original conditions. This result indicates that the photocatalytic activity of P25@Zn-PPc-n was significantly enhanced at pH 3, which may be attributed to the improved catalytic activity of the active sites of metal Zn at this pH value.

[0105] Electron paramagnetic resonance (EPR) spectroscopy was performed on P25@Zn-PPc-n using the spin trapping agent 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) to investigate the reactive oxygen species generated under illumination. Figure 16 As shown, no obvious EPR signal peak was detected in P25@Zn-PPc-n under dark conditions, but after 5 minutes of illumination, its EPR spectrum showed DMPO-·O2. -characteristic peaks with a peak shape of 2:2:1:2:1:2. This result indicates that P25@Zn-PPc-n successfully captured the key intermediates in the photocatalytic process. This finding not only fully confirms that P25@Zn-PPc-n generates H2O2 through the ORR pathway by photocatalysis, but also further proves that the doping of metal Zn and the composite strategy with semiconductor material nano-titanium dioxide P25 can significantly improve its photocatalytic efficiency for synthesizing H2O2. In addition, the intermediates detected in the EPR spectrum can effectively promote the formation of peroxyl radicals (·OOH), which is a key step in the photocatalytic synthesis of H2O2 reaction.

[0106] Rotating disc electrode (RDE) tests were performed for the study. The rotating disc electrode is an advanced electrochemical experimental device that precisely controls the diffusion layer thickness and mass transfer process on the electrode surface through the rotation of the electrode. This device can study the electrochemical reaction kinetics by adjusting the rotation speed of the electrode. The RDE test was performed on an electrochemical workstation system using a classic three-electrode system (reference electrode, counter electrode, and working electrode). The reference electrode was a saturated Ag / AgCl electrode, and the working electrode was a self-made catalyst modified electrode prepared as follows: 3 mg of catalyst was dispersed in a mixed solvent containing 0.5 ml of isopropanol, 0.5 ml of deionized water, and 20 μL of Nafion solution (5 wt%), and ultrasonically treated for 30 min to ensure uniform dispersion of the catalyst. Then, 3 μL of the prepared solution was dropped on the surface of the disc electrode and dried at room temperature. Linear sweep voltammetry (LSV) tests were performed in 0.1 M phosphate buffer solution (pH = 7) saturated with O2, with a scan rate of 10 mVs -1 After 1 h of ultrasonic treatment, the electron transfer number (n) involved in the ORR process was calculated by fitting the slope of the LSV curve with the Koutecky-Levich equation. The calculation formula (1) is as follows:

[0107]

[0108] B = 0.2 n Fv -1 / 6 CD 2 / 3 (1)

[0109] K = B -1

[0110] where j represents the current density, j k represents the kinetic current density, ω represents the rotation speed (unit: rpm), n represents the electron transfer number, F represents the Faraday constant (96485 C mol -1 ), C represents the volume concentration of O2 in water (1.2 x 10 -6 mol cm -3D represents the diffusion coefficient of O2 (1.9 × 10⁻⁶). -5 cm 2 s -1 ), where v represents the dynamic viscosity of water (0.01 cm⁻¹). 2 s -1 K represents the slope.

[0111] like Figure 17 As shown in (a) and (b), not only were the LSV curves of P25@Zn-PPc-n obtained at different rotational speeds, but the electron transfer number in the ORR pathway was also calculated using the Koutecky-Levich equation. The calculation results show that the electron transfer number of P25@Zn-PPc-n is approximately 2.24. This result clearly indicates that in the photocatalytic synthesis of H2O2, the catalyst P25@Zn-PPc-n mainly catalyzes the reaction through the two-electron transfer ORR pathway.

[0112] This invention employs a modification strategy of doping metallic Zn with semiconductor material nano-titanium dioxide P25 to successfully prepare the catalyst P25@Zn-PPc-n and a series of comparative materials. Subsequently, the photocatalytic performance of the materials was further optimized through ball milling and cell disruption. To comprehensively characterize and analyze the synthesized materials, various testing methods were employed, including XRD, FT-IR, SEM, Raman spectroscopy, BET, TGA, XPS, EPR, RDE, and some photoelectrochemical tests. The performance of the synthesized P25@Zn-PPc-n in the photocatalytic synthesis of H2O2 was investigated. The effects of filters and different acidic pH environments on the photocatalytic activity of P25@Zn-PPc-n in the H2O2 synthesis were also explored, and the mechanism of the material's photocatalytic H2O2 synthesis was further analyzed. The main conclusions are as follows:

[0113] (1) A synthesis strategy involving modification of polyphthalocyanine materials by doping with metallic Zn and combining it with the semiconductor material P25 was successfully implemented, resulting in the synthesis of P25@Zn-PPc-n and a series of comparative materials. A series of characterization methods not only confirmed the success of these synthesis strategies but also ensured that the synthesized P25@Zn-PPc-n met the conditions for photocatalytic synthesis of H2O2. These results indicate that the synthesized materials achieved the expected goals in both structure and function, laying a solid foundation for subsequent photocatalytic performance testing.

[0114] (2) Performance testing of the photocatalytic synthesis of H2O2 using the catalyst P25@Zn-PPc-n. Under the condition of ethanol as a sacrificial agent, the yield of H2O2 synthesized by the P25@Zn-PPc-n photocatalytic synthesis was 315.79 μmol g. -1h-1 increased the yield. This result demonstrates the success of the modification strategy of doping metallic Zn and combining it with the semiconductor material P25.

[0115] (3) The effect of the filter on the photocatalytic performance of P25@Zn-PPc-n was further investigated. Under the condition of ethanol as a sacrificial agent and without using a 400nm filter, the yield of H2O2 synthesized by the photocatalytic synthesis of P25@Zn-PPc-n was 872 μmol g. -1 The yield was 1.76 times higher than when using a 400 nm filter. Furthermore, the photocatalytic synthesis of H2O2 by P25@Zn-PPc-n under different acidic pH conditions was tested. At pH 3, the yield of H2O2 synthesized by P25@Zn-PPc-n was 1031.09 μmol g. -1 The photocatalytic performance was further improved by 18.24% at h-1. These results demonstrate that the filter and the pH of the photocatalytic reaction solution have a significant impact on the performance of the P25@Zn-PPc-n catalyst in the photocatalytic synthesis of H2O2.

[0116] (4) P25@Zn-PPc-n exhibits a low degradation rate of H2O2 and good cycling stability. Through analysis of quenching experiment results, EPR analysis, band structure analysis, and RDE analysis, we clarified that the catalyst P25@Zn-PPc-n reacts via the ORR pathway of indirect two-electron transfer during the photocatalytic generation of H2O2.

[0117] Therefore, this invention utilizes the above-mentioned method for preparing titanium dioxide composite metal polyphthalocyanine photocatalysts and synthesizing hydrogen peroxide to successfully synthesize the edge-functionalized polyphthalocyanine composite material P25@Zn-PPc-n, which chelates TiO2 with metal sites, ensuring that the synthesized P25@Zn-PPc-n meets the conditions for photocatalytic synthesis of H2O2.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a titanium dioxide composite metal polyphthalocyanine photocatalyst, characterized in that, Includes the following steps: S1. Weigh out pyromellitic anhydride, 2,3-naphthalenedicarboxylic anhydride, chloride, urea, titanium dioxide and ammonium molybdate tetrahydrate, mix them evenly in a mortar and grind for 10 minutes, then transfer the mixture to a ceramic crucible. S2. Place the ceramic crucible in a muffle furnace and heat it to 220°C at a heating rate of 5°C / min. Maintain this temperature for 7 hours to obtain the crude product. S3. Place the obtained crude product in a Soxhlet extractor and extract it using a mixed solvent; S4. After extraction, place the product in a vacuum drying oven and dry overnight. Then, place the dried sample in a ball mill jar containing zirconium dioxide balls and ball mill at 500 rpm for 6 hours. S5. After ball milling, weigh the sample and disperse it in deionized water. Use an ultrasonic cell disruptor to treat it for 1 hour to achieve uniform dispersion of the sample. Perform three centrifugal washings on the ultrasonically treated solution. Place the washed sample in a vacuum drying oven to dry overnight to obtain the final product.

2. The preparation method of the titanium dioxide composite metal polyphthalocyanine photocatalyst according to claim 1, characterized in that: In step S1, the chlorides include ammonium chloride and zinc chloride.

3. The preparation method of the titanium dioxide composite metal polyphthalocyanine photocatalyst according to claim 1, characterized in that: In step S1, the titanium dioxide is nano-titanium dioxide P25.

4. The preparation method of the titanium dioxide composite metal polyphthalocyanine photocatalyst according to claim 1, characterized in that: In step S3, the mixed solvent is a mixture of water, ethanol and tetrahydrofuran, with a volume ratio of 1:1:

1.

5. The preparation method of the titanium dioxide composite metal polyphthalocyanine photocatalyst according to claim 1, characterized in that: In step S5, acetone solution is used for centrifugal washing.

6. A titanium dioxide composite metal polyphthalocyanine photocatalyst, characterized in that: It is prepared by the preparation method described in any one of claims 1-5.

7. A method for synthesizing hydrogen peroxide using a titanium dioxide composite metal polyphthalocyanine photocatalyst, characterized in that: This is achieved through the photocatalyst described in claim 6, comprising the following steps: At room temperature, the photocatalyst, deionized water, and sacrificial agent were uniformly dispersed in a glass photocatalytic reactor. Under dark conditions, O2 was introduced into the solution at a flow rate of 300 mL / min and stirred continuously for 30 min to achieve the adsorption-desorption equilibrium of O2. The solution was then irradiated with a xenon lamp to generate hydrogen peroxide.

8. The method for synthesizing hydrogen peroxide using a titanium dioxide composite metal polyphthalocyanine photocatalyst according to claim 7, characterized in that: The sacrificial agent is ethanol.

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