Preparation method and application of Ce-C3N5 / ZnO composite photocatalytic material

Abstract

The present invention discloses a preparation method and application of a Ce-C3N5 / ZnO composite photocatalytic material. The preparation method comprises the following steps: adding 3-amino-1,2,4-triazole to a cerium nitrate solution, heating and stirring until the water evaporates to obtain a solid product; grinding the obtained solid product and calcining it to obtain Ce-C3N5; adding anhydrous ethanol to a soluble zinc salt solution and stirring to obtain a mixed solution a; dropwise adding sodium hydroxide solution to the mixed solution a, and after the sodium hydroxide solution is completely added, stirring the obtained mixed system at room temperature and then performing ultrasonic treatment and heat treatment in sequence; after the heat treatment is completed, discarding the supernatant in the reaction system to obtain a solid precipitate; washing the solid precipitate and drying and grinding it to obtain ZnO. The present invention dopes cerium with zinc oxide and g-C3N5 to improve the catalytic efficiency of the photocatalytic material.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, in particular to a preparation method and application of a Ce-C3N5 / ZnO composite photocatalytic material. Background Art

[0002] Composite photocatalytic materials are currently widely used for wastewater degradation. They are low-cost, can oxidize water pollutants into water and carbon dioxide, reducing secondary pollution, and the catalysts can be recycled and reused. However, among the photocatalysts currently studied, semiconductor photocatalytic materials have been less effective, suffering from problems such as a narrow response range under sunlight, insufficient visible light absorption, a high recombination rate of photogenerated charges, and slow redox reactions on the catalyst material surface.

[0003] Graphitic carbon nitride (g-C3N5 or C3N5) is a new type of metal-free layered polymer semiconductor photocatalytic material that can be used for photocatalytic decomposition of pollutants. It has good photostability, chemical stability, and a narrow band gap, and a wide range of response to sunlight. However, it has disadvantages such as low electron transfer ability, small specific surface area, high electron-hole recombination rate, and low quantum efficiency, resulting in poor catalytic effect.

[0004] Zinc oxide (ZnO) is abundant, inexpensive, and readily available. It is an environmentally friendly semiconductor photocatalytic material and one of the most widely studied photocatalysts. However, its application range is limited because it only absorbs ultraviolet light and has almost no response in the visible light region.

[0005] To achieve more efficient photocatalytic decomposition, these catalytic materials can be optimized through methods such as metal doping and semiconductor material composites. This can increase the material's specific surface area, broaden the light absorption range, and enhance the efficiency of photogenerated electron-hole separation, thereby achieving better catalytic results. Liu Sile et al. prepared a ZnO / g-C3N4 composite photocatalyst using a hybrid method. This composite photocatalyst has a large specific surface area, providing more active sites for the photocatalytic reaction, but the doping method is relatively simple. Shen Yongjun et al. prepared a ZnO-CeO2 / g-C3N4 ternary composite catalyst using thermal polymerization and hydrothermal methods, enhancing the efficiency of photogenerated electron-hole separation. However, this composite photocatalyst exhibits poor catalytic performance under high pH conditions and is not suitable for treating wastewater containing large amounts of alkali. The question of how to modify semiconductor photocatalytic materials with metals to enhance their catalytic decomposition efficiency and how to modify them with metals for alkaline wastewater treatment remains a pressing issue. Summary of the Invention

[0006] To this end, the technical problem to be solved by the present invention is to provide a preparation method and application of Ce-C3N5 / ZnO composite photocatalytic material. This method can synthesize cerium element, zinc oxide, and graphite phase carbon nitride (g-C3N5) into a composite photocatalytic material. The obtained material has a narrow band gap, a high separation efficiency of electrons and holes generated under sunlight, high stability, can be recycled and collected, and can quickly adsorb and degrade organic pollutants under alkaline conditions.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for preparing a Ce-C3N5 / ZnO composite photocatalytic material comprises the following steps:

[0009] Step A: adding 3-amino-1,2,4-triazole to a cerium nitrate solution, heating and stirring until the water evaporates to obtain a solid product; grinding the solid product and calcining it until the calcination is completed to obtain Ce-C3N5;

[0010] Step B: adding anhydrous ethanol to a soluble zinc salt solution and stirring to obtain a mixed solution a; adding sodium hydroxide solution dropwise to the mixed solution a, and after the sodium hydroxide solution is completely added, placing the obtained mixed system at room temperature and stirring, and then performing ultrasonic treatment and heat treatment in sequence; after the heat treatment is completed, discarding the supernatant in the reaction system to obtain a solid precipitate; washing the solid precipitate and then drying and grinding to obtain ZnO; compared with other zinc salts such as zinc chloride, the zinc oxide prepared using zinc nitrate as a zinc source has a better crystal structure, which is conducive to subsequent composite with Ce-C3N5 to obtain a Ce-C3N5 / ZnO composite photocatalytic material with relatively ideal photocatalytic activity; if other soluble zinc salts, such as zinc chloride, are used, the chloride ions contained therein may have a certain impact on subsequent reactions; ultrasonic treatment can make the zinc oxide particles in the solution smaller, more uniformly dispersed and of better dispersion quality, which is conducive to obtaining zinc oxide with a better crystal structure; if ultrasonic treatment is not performed, the prepared zinc oxide particles are larger, agglomerate, and result in uneven dispersion, and zinc oxide with an ideal crystal structure cannot be obtained;

[0011] Step C: dispersing ZnO in anhydrous ethanol to obtain a ZnO dispersion; adding Ce-C3N5 to the ZnO dispersion to obtain a mixed raw material dispersion; placing the mixed raw material dispersion in a closed container for a solvent thermal reaction; performing solid-liquid separation after the reaction is completed, washing, drying and grinding the solid material obtained by the solid-liquid separation to obtain a Ce-C3N5 / ZnO composite photocatalytic material.

[0012] In the above-mentioned method for preparing the Ce-C3N5 / ZnO composite photocatalytic material, in step A, the mass fraction of cerium nitrate in the cerium nitrate solution is 0.25wt% to 4wt%;

[0013] The mass ratio of the added amount of 3-amino-1,2,4-triazole to the cerium nitrate in the cerium nitrate solution is 1.25-20:1; the temperature during heating and stirring is 70-90°C; the calcination conditions are: heating to 520-550°C at a heating rate of 5°C / min and then keeping the temperature for 180-220 minutes; the particle size of the powder formed by the ground solid product is in the range of 1-100 nm; when the particle size of Ce-C3N5 is in the range of 1-100 nm, the Ce-C3N5 is composited with the self-prepared ZnO of the present invention to prepare a photocatalytic material with better activity in adsorbing and degrading organic pollutants under alkaline conditions.

[0014] In the above-mentioned method for preparing Ce-C3N5 / ZnO composite photocatalytic material, in step A, the mass fraction of cerium nitrate in the cerium nitrate solution is 1.0wt%; the ratio of the amount of 3-amino-1,2,4-triazole added to the mass of cerium nitrate in the cerium nitrate solution is 5:1.

[0015] In the aforementioned method for preparing a Ce-C3N5 / ZnO composite photocatalytic material, in step A, the heating and stirring temperature is 80°C; the calcination conditions are: heating to 520°C at a rate of 5°C / min and then holding for 180 minutes; and the solid product, after grinding, forms a powder with a particle size range of 1 to 100 nm. This heating rate is adopted because a too low heating rate results in insufficient decomposition power, while a too high heating rate easily leads to uneven heat transfer. Given a given calcination time, the resulting Ce-C3N5 has poor performance. The reason for adopting this calcination temperature is that calcination temperatures below 520℃ are insufficient to support the polymerization of 3-amino-1,2,4-triazole to form g-C3N5: When the temperature reaches 500℃, characteristic peaks of (100) and (002) crystal planes begin to appear near 13° and 27° in the XRD spectrum. 13° corresponds to the in-plane repeating unit of the tri-s-triazine part, and 27° corresponds to the interlayer stacking of the conjugated aromatic system, but the peaks do not reach the highest. When the temperature rises to 520℃, the intensity of the characteristic peak of the (002) crystal plane of g-C3N5 is the highest, indicating that the crystal structure of g-C3N5 is the best at this calcination temperature. However, when the calcination temperature is further increased, especially above 550℃, the intensity of the (100) and (002) peaks of g-C3N5 decreases, and the crystal structure of g-C3N5 is destroyed as the calcination temperature increases. In addition, if the temperature is too high, the kinetic energy of the reactant molecules will increase too quickly, which is not conducive to the formation of stable crystal nuclei.

[0016] The preparation method of the above-mentioned Ce-C3N5 / ZnO composite photocatalytic material, in step B, the soluble zinc salt solution is a 0.3-0.4 mol / L zinc nitrate solution, and the volume ratio of the zinc nitrate solution to anhydrous ethanol is 1-2:1; the molar concentration of the sodium hydroxide solution is 1-1.33 mol / L; the sodium hydroxide solution is added dropwise over 5-10 minutes; the volume ratio of the mixed solution a to the sodium hydroxide solution is 10:(3-4); the stirring time of the mixed system at room temperature is 20-30 minutes, and the stirring rate at room temperature is 400-500 rpm; the treatment time of the ultrasonic treatment is 30-50 minutes; the heating time of the heat treatment is 600-660 minutes, and the heating temperature is 90-110°C; the solid precipitate is washed alternately with water and alcohol and then dried at 60-70°C for 10-12 hours; the ZnO powder obtained after grinding the solid precipitate has a particle size of 10-20 nm. ZnO powder particles that are too large are not conducive to subsequent compounding with Ce-C3N5. This is because too large particles will lead to too small surface energy of the material, and the specific surface area will also be too small, resulting in fewer active sites for the reaction. Compared with commercially available ZnO, the zinc oxide prepared by the above method has a higher degradation efficiency in the Ce-C3N5 / ZnO composite photocatalytic material formed after compounding with Ce-C3N5. This is because: the photocatalytic activity is directly related to factors such as the crystal structure of zinc oxide. If commercially available zinc oxide is used directly, there are fewer controllable variables, which will affect the overall photocatalytic activity of the material. When ZnO is prepared by the method of the present invention, ZnO with an ideal crystal structure can be obtained by controlling the stirring, ultrasonic treatment or heating treatment time. The photocatalytic material prepared by compounding the zinc oxide with the crystal structure and the Ce-C3N5 prepared by the present invention has better adsorption and degradation activity of organic pollutants under alkaline conditions.

[0017] The preparation method of the above-mentioned Ce-C3N5 / ZnO composite photocatalytic material, in step B, the soluble zinc salt solution is a 0.33 mol / L zinc nitrate solution, and the volume ratio of the zinc nitrate solution to anhydrous ethanol is 1.5:1; the molar concentration of the sodium hydroxide solution is 1.33 mol / L; the sodium hydroxide solution is added dropwise over 10 minutes; the volume ratio of the mixed solution a to the sodium hydroxide solution is 10:3; the room temperature stirring time of the mixed system is 30 minutes, and the room temperature stirring rate is 400 rpm; the ultrasonic treatment time is 30 minutes; the heating time of the heat treatment is 600 minutes, and the heating temperature is 100°C; the solid precipitate is washed alternately with water and alcohol and then dried at 60°C for 12 hours; the ZnO powder obtained after grinding the solid precipitate has a particle size of 10 to 20 nm. The addition of anhydrous ethanol in the present invention facilitates the formation of a precipitate between the mixed solution a and sodium hydroxide. However, adding too little anhydrous ethanol can result in incomplete ion coordination, affecting the subsequent solvent thermal reaction's composite effect. Adding too much anhydrous ethanol can cause other reactions, similarly affecting the subsequent solvent thermal reaction's composite effect and causing unnecessary material loss. The water-alcohol alternating washing method uses 99.7% anhydrous ethanol, which can more effectively remove residual solvent from the solid. Anhydrous ethanol has poor electrical conductivity, and using only anhydrous ethanol for washing can easily lead to static electricity, further causing impurities to be introduced into the sample. Using water-alcohol alternating washing solves this problem.

[0018] The preparation method of the above-mentioned Ce-C3N5 / ZnO composite photocatalytic material, in step C, ZnO is dispersed in anhydrous ethanol and stirred at room temperature for 10 to 15 minutes to obtain a ZnO dispersion; the mass fraction of ZnO in the ZnO dispersion is 0.3 to 0.4wt%; the mass ratio of ZnO to Ce-C3N5 in the mixed raw material dispersion is 0.2 to 5:1, and before conducting a solvent thermal reaction, the mixed raw material dispersion is stirred at room temperature for 50 to 70 minutes; the temperature of the solvent thermal reaction is 80 to 140°C, and the reaction time is 360 to 840 minutes; the solid material is washed with anhydrous ethanol and then dried at 60 to 70°C for 10 to 12 hours; the particle size of the Ce-C3N5 / ZnO composite photocatalytic material obtained after grinding is 2 to 10 nm. Grinding is beneficial to obtaining composite photocatalytic materials with smaller particle size. The smaller the particle size, the more particles are contained in the unit mass of the composite photocatalytic material, and the larger the specific surface area of ​​the particles. As the specific surface area increases, the adsorption performance of the composite photocatalytic material is enhanced, the number of active points per unit surface area increases, the probability of reaction increases accordingly, and the photocatalytic activity is improved.

[0019] The preparation method of the above-mentioned Ce-C3N5 / ZnO composite photocatalytic material, in step C, ZnO is dispersed in anhydrous ethanol and stirred at room temperature for 10 minutes to obtain a ZnO dispersion; the mass fraction of ZnO in the ZnO dispersion is 0.33wt%; the mass ratio of ZnO to Ce-C3N5 in the mixed raw material dispersion is 1:1, and before conducting a solvent thermal reaction, the mixed raw material dispersion is stirred at room temperature for 60 minutes; the temperature of the solvent thermal reaction is 140°C, and the reaction time is 600 minutes; the solid material is washed with anhydrous ethanol and then dried at 70°C for 12 hours; the particle size of the Ce-C3N5 / ZnO composite photocatalytic material obtained after grinding is 2 to 10 nm.

[0020] An application of a Ce-C3N5 / ZnO composite photocatalytic material, wherein the Ce-C3N5 / ZnO composite photocatalytic material prepared by the above-mentioned preparation method of the Ce-C3N5 / ZnO composite photocatalytic material is used for catalytic decomposition of organic pollutants.

[0021] The technical solution of the present invention achieves the following beneficial technical effects:

[0022] 1. The present invention combines Ce-C3N5 (doped with Ce and C3N5) with self-prepared ZnO. By regulating parameters such as the reaction temperature, reaction time, and compounding ratio during the solvothermal compounding reaction, a Ce-C3N5 / ZnO ternary composite photocatalytic material is prepared. This material can catalyze the degradation of organic pollutants and can be used for the remediation of contaminated water bodies. Compared to conventional photocatalytic materials, the Ce-C3N5 / ZnO composite photocatalytic material prepared using the method of the present invention has a narrower band gap, higher electron-hole separation efficiency generated under sunlight, higher stability, and higher catalytic efficiency.

[0023] 2. The Ce-C3N5 / ZnO composite photocatalytic material prepared by the preparation method of the Ce-C3N5 / ZnO composite photocatalytic material in the present invention has high catalytic activity under alkaline conditions and can be used for the catalytic treatment of organic pollutants in alkaline wastewater.

[0024] 3. After five cycle experiments, the degradation efficiency of the Ce-C3N5 / ZnO composite photocatalytic material prepared by the preparation method of the Ce-C3N5 / ZnO composite photocatalytic material in the present invention is still as high as 87%, which proves that the material has high stability and can be recycled and collected for use, which is beneficial to saving materials and energy and reducing production costs, indicating that the composite photocatalytic material is green, stable and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1a XRD spectra of different photocatalytic materials in the embodiment of the present invention 1;

[0026] Figure 1b XRD spectra of different photocatalytic materials in the embodiments of the present invention Figure 2 ;

[0027] Figure 2 FT-IR images of different photocatalysts in the embodiments of the present invention;

[0028] Figure 3a Transmission electron microscope image of Ce-C3N5 / ZnO in the embodiment of the present invention; Figure 3b HRTEM image of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0029] Figure 3c HAADF image of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0030] Figure 3d EDS spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention (zinc, oxygen, carbon, nitrogen and cerium elements);

[0031] Figure 3e EDS spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention (cerium element);

[0032] Figure 3f EDS spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention (nitrogen element);

[0033] Figure 3g EDS spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention (oxygen element);

[0034] Figure 3h EDS spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention (zinc element);

[0035] Figure 3i EDS analysis diagram of Ce-C3N5 / ZnO in the embodiment of this invention;

[0036] Figure 4a XPS measurement spectrum of the composite material of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0037] Figure 4b High-resolution C1s spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0038] Figure 4c High-resolution N1s spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0039] Figure 4d High-resolution O1s spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0040] Figure 4e High-resolution Zn 2p spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0041] Figure 4f High-resolution Ce 2d spectrum of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0042] Figure 5a UV-Vis DRS spectra of different photocatalytic materials in the embodiments of the present invention;

[0043] Figure 5b Band gap calculation diagram of different photocatalytic materials in the embodiments of the present invention;

[0044] Figure 6 Photoluminescence (PL) emission spectra of different photocatalytic materials in the embodiments of the present invention at an excitation wavelength of 389 nm;

[0045] Figure 7a Photocurrent diagrams of samples ZnO, C3N5, and Ce-C3N5 / ZnO in the embodiments of the present invention;

[0046] Figure 7b Electrochemical impedance spectroscopy of samples ZnO, C3N5, and Ce-C3N5 / ZnO in the examples of the present invention;

[0047] Figure 8a The effect of solvent thermal temperature on the photocatalytic effect of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0048] Figure 8b The first-order kinetic fitting curve of Ce-C3N5 / ZnO affected by the solvothermal temperature in the embodiment of the present invention;

[0049] Figure 9a Influence diagram of the catalytic effect of Ce-C3N5 / ZnO on the solvothermal time in the embodiment of the present invention;

[0050] Figure 9b The first-order kinetic fitting curve of Ce-C3N5 / ZnO affected by the solvothermal time in the embodiment of the present invention;

[0051] Figure 10a The effect of Ce doping ratio on the photocatalytic effect of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0052] Figure 10b First-order kinetic fitting curve diagram of the influence of different Ce doping ratios in the embodiment of the present invention;

[0053] Figure 11a Figure 2 shows the effect of the mass ratio of ZnO to Ce-C3N5 on the photocatalytic effect of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0054] Figure 11b First-order kinetic fitting curves of materials with different mass ratios of ZnO and Ce-C3N5 in the embodiment of the present invention;

[0055] Figure 12a Catalytic degradation effect diagram of different photocatalysts in the embodiments of the present invention;

[0056] Figure 12b First-order kinetic fitting curves of different photocatalysts in the embodiments of the present invention;

[0057] Figure 12c Graph showing the degradation rate of methylene blue catalyzed by Ce-C3N5 / ZnO at different pH values ​​in the examples of the present invention;

[0058] Figure 13a Figure 1 shows the stability test results of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0059] Figure 13b Stability test results of Ce-C3N5 / ZnO in the embodiment of the present invention Figure 2 ;

[0060] Figure 14a The effect of free radical scavengers on degradation rate in the embodiment of the present invention;

[0061] Figure 14b ERS free radical detection diagram of Ce-C3N5 / ZnO in the embodiment of the present invention (h + );

[0062] Figure 14c ERS free radical detection diagram (·OH) of Ce-C3N5 / ZnO in the embodiment of the present invention;

[0063] Figure 14d ERS free radical detection diagram of Ce-C3N5 / ZnO in the embodiment of the present invention (·O2 - );

[0064] Figure 15 Mott-Schottky curve of ZnO in the embodiment of the present invention;

[0065] Figure 16 Mott-Schottky curve of Ce-C3N5 in an embodiment of the present invention. DETAILED DESCRIPTION

[0066] 1 Experiment

[0067] 1.1 Preparation of photocatalytic materials

[0068] Preparation of Ce-C3N5: Add 1 wt% cerium nitrate to 30 mL of distilled water. After it is completely dissolved, add 1.5 g of 3-amino-1,2,4-triazole and stir at 80°C until dry and crystallized. Grind the resulting solid product into a powder, transfer it to a crucible, and place it in a muffle furnace for calcination. Set the heating rate to 5°C / min, the calcination temperature to 520°C, and the holding time to 180 min. After cooling to room temperature, take it out, grind it thoroughly, and collect it to obtain Ce-C3N5.

[0069] Preparation of ZnO: After dissolving 2.97 g of zinc nitrate hexahydrate in 30 mL of distilled water, 20 mL of anhydrous ethanol (purity of 99.7%) was added to the solution to obtain a mixed solution a; 0.8 g of sodium hydroxide was dissolved in 15 mL of distilled water and then added dropwise to the mixed solution a to obtain a milky white suspension; the suspension was stirred at room temperature for 30 minutes and then ultrasonicated in an ultrasonic machine for 30 minutes. The treated solution was kept at 100° C. for 600 minutes, a portion of the supernatant was poured off, and the remaining reaction solution was washed alternately with water and alcohol three times each, and then dried and ground to obtain ZnO.

[0070] Preparation of Ce-C3N5 / ZnO: The preparation was carried out by a solvothermal method. 0.1 g of ZnO was added to 30 mL of anhydrous ethanol, the container was sealed, and stirred at room temperature for 10 min using a magnetic stirrer. Then, 0.1 g of Ce-C3N5 was added to the container, the container was sealed and stirred for 60 min, and then the contents of the container were transferred to a reactor, covered and fitted with a shell, and kept warm at 140°C for 600 min. After cooling, it was washed three times with anhydrous ethanol, dried at 70°C, and ground with an agate mortar to obtain a Ce-C3N5 / ZnO composite photocatalytic material, recorded as (1%) Ce-C3N5 / ZnO.

[0071] C3N5 was prepared using the above-mentioned Ce-C3N5 preparation method without adding cerium nitrate. Ce-C3N5 with different metal doping ratios was prepared using the above-mentioned Ce-C3N5 preparation method, but with only the mass fraction of cerium nitrate added to the Ce-C3N5 changed to 0.25wt%, 0.5wt%, 2wt%, and 4wt%, respectively. Ce-C3N5 and Ce-C3N5 / ZnO with different metal doping ratios were further prepared. Ce-C3N5 / ZnO with different ZnO contents was prepared using the above-mentioned Ce-C3N5 / ZnO preparation method, but with only the mass ratio of ZnO to Ce-C3N5 changed to 1:5, 1:3, 3:1, and 5:1. C3N5 / ZnO was prepared using the same Ce-C3N5 / ZnO preparation method as the above-mentioned Ce-C3N5 / ZnO, but with Ce-C3N5 replaced by C3N5. Both C3N5 and C3N5 / ZnO were used as controls. The mass ratio of Ce-C3N5 to ZnO is 1:1. When preparing Ce-C3N5, the mass fractions of cerium nitrate added are 0.25wt%, 0.5wt%, 2wt% and 4wt% of Ce-C3N5 / ZnO, which are respectively recorded as (0.25%) Ce-C3N5 / ZnO, (0.5%) Ce-C3N5 / ZnO, (2%) Ce-C3N5 / ZnO and (4%) Ce-C3N5 / ZnO.

[0072] 1.2 Photocatalytic experiment

[0073] A 20 mg / L methylene blue solution was used to simulate industrial wastewater, and a 500 W xenon lamp was used as a simulated sunlight light source for photocatalytic reaction. The reaction temperature was maintained at 20°C through a water circulation system.

[0074] The specific steps are as follows: first, prepare a 20mg / L methylene blue solution, weigh 30mg of photocatalytic material and add it to the photocatalytic tube, add a magnetic particle of appropriate size, measure 40mL of the prepared methylene blue solution, and pour it into the photocatalytic tube. Place it on a photocatalytic stirrer, adjust the rotation and revolution, and react in the dark for 30 minutes under light-proof and stirring conditions to reach adsorption-desorption equilibrium. Take a sample once after the dark reaction. Before turning on the 500W xenon lamp, turn on the water circulation system. After turning on the light, take a sample every 15 minutes, for a total of 7 samples, and sample 3mL each time. After the photocatalytic experiment is completed, centrifuge the small sample tube in a centrifuge at 5000r / min for 5 minutes to separate the catalyst and supernatant, and then use a UV-visible spectrophotometer (Labtech9100B) to measure the absorbance at a wavelength of 665nm.

[0075] Use a standard curve to convert the absorbance to the corresponding concentration. Record the newly prepared methylene blue concentration as C0, and define C as the methylene blue concentration measured at time t. Draw a graph with reaction time t as the horizontal axis and C / C0 as the vertical axis to show the degradation effect of Ce-C3N5 / ZnO composite photocatalytic material on the simulated pollutant methylene blue. The degradation rate calculation formula (1) of the methylene blue solution is as follows:

[0076]

[0077] 1.3XRD analysis

[0078] In order to study the crystal structure of the prepared photocatalytic material, X-ray diffraction (XRD) was used to characterize the material. Figure 1a-Figure 1b As shown in the figure, g-C3N5 and Ce-C3N5 have similar diffraction patterns, with a prominent peak at approximately 27°, corresponding to the (002) plane of graphitic carbon nitride, indicating that the material has interlayer stacking composed of triazine groups. The peak of the zinc oxide particles can be determined to be a hexagonal wurtzite structure. Figure 1b As can be seen in the images, the peak positions of Ce-C3N5 and Ce-C3N5 / ZnO are relatively pure, while the peak position of g-C3N5 shifts slightly toward higher angles, indicating that Ce doping reduces the distance between the graphite-like layers of g-C3N5. Compared to the pure material, the diffraction peaks of the composite material are broadened. According to the Scherrer equation D = Kλ / βCOSθ, smaller grains lead to broadening of the diffraction peaks, but no peak shift occurs, indicating that ZnO is deposited on Ce-C3N5. The composite material also lacks impurity peaks, indicating high purity. The diffraction peaks associated with ZnO and Ce-C3N5 in the composite material confirm the formation of heterojunctions between the material particles.

[0079] 1.4 FT-IR spectroscopy analysis

[0080] The surface functional groups of the prepared samples were measured by FT-IR analysis. The samples were treated with potassium bromide pellet method and the scanning range was 400-4000 cm -1 . Figure 2 FT-IR images of ZnO, C3N5, C3N5 / ZnO, Ce-C3N5, and Ce-C3N5 / ZnO. -1 The peak at 1100~1500cm is caused by the bending vibration of Zn-O. -1 The peak at 812 cm is due to the Zn-OH bond. -1 The peaks observed at 1200-1600 cm-1 correspond to the triazine units in g-C3N5. -1 The absorption in the range can be attributed to the CN / C=N heterocycle (P-C3N5) of the CN unit.-1 The absorption peaks on the left and right are due to the -OH stretching vibration of surface-adsorbed water molecules and the uncondensed -NH2 groups from 3-AT.

[0081] When ZnO is added to g-C3N5, the composite exhibits both g-C3N5 and ZnO absorption peaks, with the peak widths becoming wider, indicating a higher level of interaction between the vibrational modes. FT-IR results confirm the successful synthesis of the ZnO / Ce-C3N5 composite.

[0082] 1.5 Morphology and structure

[0083] The prepared Ce-C3N5 heterojunction was further analyzed using TEM and HRTEM. Figure 3a This is a transmission electron microscopy image of the Ce-C3N5 / ZnO composite photocatalytic material. It can be observed that the Ce-doped C3N5 has a flake-like structure, while the zinc oxide is granular. The zinc oxide nanoparticles are deposited on the Ce-C3N5 nanosheets, indicating that the Ce-C3N5 / ZnO composite photocatalytic material has been successfully constructed and formed a heterojunction. Figure 3b The HRTEM images shown clearly reveal the surface microstructure and interface boundary between ZnO and Ce-C3N5. The lattice fringes of 0.247 nm and 0.281 nm can be indexed to the (101) and (100) planes of normal ZnO (PDF#99-0111), while the lattice fringes of Ce-C3N5 are not clearly detected due to its low crystallinity. These results indicate that an interaction exists between Ce-C3N5 and ZnO in the composite material formed by C3N5 and ZnO. Figure 3c For Ce-C3N5 / ZnO, the distribution of light and heavy elements can be directly seen by combining HAADF images with EDS images. Figure 3d to Figure 3i ) showed that ZnO / Ce-C3N5 was mainly composed of Zn, O, C, N and Ce, and all elements were evenly distributed, further illustrating the successful construction of Ce-C3N5 / ZnO.

[0084] 1.6 XPS analysis

[0085] XPS analysis of Ce-C3N5 / ZnO composite materials was carried out. Figure 4a , the XPS survey spectrum of the composite material showed the presence of all elements (C, N, Ce, O and Zn) related to Ce-C3N5 and ZnO.

[0086] like Figure 4b For high-resolution C1s spectra, two peaks at 284.9 and 287.9 ​​eV were deconvoluted using a Gaussian function, representing CC and NC=N bonds, respectively.

[0087] like Figure 4c The high-resolution N1s spectrum contains two deconvoluted peaks at approximately 398.5 eV and 399.4 eV, which are associated with the CN=C and sp3 N-(C)3 bonds, respectively. The peak at a binding energy of 400.4 eV is due to the residual -NH2 donating additional nitrogen to the edge / bridging azo (CN=NC).

[0088] like Figure 4e , the binding energies are 1022.2 and 1045.3 eV, corresponding to the Zn-O bond Zn 2p 3 / 2 and Zn2p 1 / 2 , the energy difference is about 23.1eV, indicating that Zn in the sample is in a stable (P2) state, which is exactly the same as the characteristics of divalent zinc ions.

[0089] like Figure 4f The peaks at 898.4 and 882.02 eV in Ce-C3N5 / ZnO sample are attributed to Ce 3d spectra. 4+ 3d 5 / 2 Since C3N5 is a layered structure covering the Ce-C3N5 / ZnO surface, the Ce signal is very weak.

[0090] 1.7 Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) analysis

[0091] UV-vis DRS was used to analyze the optical and electronic properties of the composite photocatalytic materials and evaluate the light absorption efficiency and band gap of the composite photocatalytic materials. The scanning range was 200-800 nm. Figure 5a The absorption edge of ZnO is at 397nm, while that of g-C3N5 is around 725nm. g-C3N5 exhibits stronger visible light absorption than pure ZnO, indicating that g-C3N5 can be excited by visible light. This suggests that g-C3N5 is a photoresponsive material that can enhance the light absorption properties of ZnO. The strong absorption of C3N5 is primarily due to the overlap of the N 2p orbital of the bridging azo nitrogen of the triazole unit with the heptazine π-coupling system, expanding the π-coupling system (P-C3N5). The absorption edge of Ce-C3N5 is around 713nm. Compared to pure g-C3N5, the absorption band of Ce-C3N5 is blue-shifted, indicating quantum confinement effects or defects in the g-C3N5 crystal system after Ce doping. However, compared with pure ZnO, the absorption of visible light by Ce-C3N5 / ZnO composite photocatalytic material prepared after coupling Ce-C3N5 and ZnO is significantly increased, and a significant absorption red shift is observed, indicating that the composite photocatalytic material has excellent performance. The band gap value of the photocatalytic material is further estimated using the equation Tauc model, as shown in Figure 2. Figure 5bAs shown in the figure, the band gaps of g-C3N5, ZnO, Ce-C3N5, C3N5 / ZnO, and Ce-C3N5 / ZnO are 1.96 eV, 2.71 eV, 1.77 eV, 2.66 eV, and 2.31 eV, respectively. Due to the incorporation of Ce-C3N5, the light absorption intensity of Ce-C3N5 / ZnO is greatly improved (the band gap is reduced to 2.31 eV), indicating superior photocatalytic activity.

[0092] 1.8 Photoluminescence (PL) intensity

[0093] The photoluminescence (PL) intensity of the prepared samples was characterized by fluorescence spectrometer. Figure 6 The PL emission spectrum at an excitation wavelength of 389 nm is used to determine the carrier transfer efficiency during the photocatalytic process. C3N5 exhibits a strong fluorescence emission peak, indicating a high recombination rate of photogenerated electrons and holes. Its PL emission intensity decreases after Ce doping, and the PL spectrum intensity of ZnO composited with g-C3N5 and Ce-C3N5 is also lower than that of pure ZnO, g-C3N5, and Ce-C3N5. Ce-C3N5 / ZnO has the lowest PL emission peak, indicating the lowest charge recombination, indicating that the recombination of carriers in the heterogeneous composite photocatalyst is significantly suppressed, effectively promoting the migration and separation of carriers.

[0094] 1.9 Transient Current and Impedance

[0095] The charge separation efficiency was further tested by transient photocurrent response and electrochemical impedance spectroscopy (EIS) spectroscopy, and the photocurrent response curve under 50s light on / off cycle irradiation was recorded. Generally speaking, the stronger the photocurrent intensity, the higher the electron-hole separation and migration efficiency. Figure 7a-7b As shown in the figure, under the same voltage conditions, the photocurrent of Ce-C3N5 / ZnO increases rapidly. After the light is turned off, the photocurrent response of C3N5, ZnO, and Ce-C3N5 / ZnO composite photocatalytic materials returns to the original state, indicating that the combination of C3N5 and ZnO enhances the generation of electrons and the dissociation of holes, resulting in a higher efficiency of photogenerated electron transfer. When light-induced electrons ionize in the conduction band of the semiconductor, they leave holes in the valence band, thus generating a strong photocurrent.

[0096] 1.10 Effect of solvent thermal temperature on the photocatalytic effect of Ce-C3N5 / ZnO

[0097] The composite reaction of Ce-C3N5 and ZnO was carried out under the corresponding temperature conditions of 80°C, 100°C, 120°C, 140°C, and 160°C for 10 hours. After subsequent treatment, (1%) Ce-C3N5 / ZnO was prepared under different temperature conditions. The catalytic effect of (1%) Ce-C3N5 / ZnO was then measured using the method described in 1.2 above. During the catalytic effect measurement phase, the total illumination time was 105 minutes, and the sampling interval was 15 minutes.

[0098] like Figure 8a-8b As shown in the figure, at the same temperature interval, when the temperature is in the range of 80-140℃, the photocatalytic activity of the composite material (1%) Ce-C3N5 / ZnO gradually increases with the increase of temperature. When the solvent thermal temperature reaches 140℃, the degradation rate of (1%) Ce-C3N5 / ZnO is 91.53% and the degradation rate is 0.01835min -1 . When the temperature is further increased, the photocatalytic activity of (1%) Ce-C3N5 / ZnO for methylene blue shows a downward trend. It can be seen that when the temperature is 140°C, the photocatalytic degradation effect of (1%) Ce-C3N5 / ZnO on methylene blue is the best. It may be that the structure of (1%) Ce-C3N5 / ZnO is more complete and the specific surface area is larger at this time. When the temperature is too low, the material has not yet formed a relatively complete structure; when the temperature is too high, it may cause the surface of the material to agglomerate, the specific surface area becomes smaller, and the photocatalytic effect is poor.

[0099] 1.11 Effect of solvent thermal time on the photocatalytic effect of Ce-C3N5 / ZnO

[0100] The composite reaction of Ce-C3N5 and ZnO was carried out at 140°C, and the reaction times were 6h, 8h, 10h, 12h, and 14h, respectively. After the reaction was completed, (1%) Ce-C3N5 / ZnO under different temperature conditions was prepared, and then the catalytic effect of (3%) Ce-C3N5 / ZnO was measured by the method in the above 1.2.

[0101] like Figure 9a-9b When the reaction time is between 6 and 8 hours, the photocatalytic activity of the composite material (3%) Ce-C3N5 / ZnO gradually increases with time. When the solvent thermal time reaches 8 hours, the degradation rate is 91.53% and the degradation rate is 0.01945min -1When the reaction time exceeds 8 hours, the photocatalytic activity of (3%) Ce-C3N5 / ZnO for methylene blue shows a gradually decreasing trend. During the composite reaction, the interaction between ZnO and C3N5 will change. As the reaction time increases, the two form an interactive chemical bond, so the photocatalytic activity is enhanced. However, when the reaction time is too long, it may cause the material to aggregate or the surface bond of the material to disappear, resulting in a weakening of the photocatalytic performance.

[0102] 1.12 Effect of Ce doping ratio on photocatalytic performance of Ce-C3N5 / ZnO

[0103] According to the experimental plan in 1.2 above, the mass fraction of cerium nitrate added in the preparation of Ce-C3N5 was set to 0.25wt%, 0.5wt%, 1wt%, 2wt%, and 4wt%, and Ce-C3N5 with different Ce-doping ratios was prepared. Then, these Ce-C3N5 were compounded with ZnO under the previously screened conditions (reaction at 140℃ for 8h) to study the effect of the Ce-doping ratio on the photocatalytic performance of Ce-C3N5 / ZnO.

[0104] like Figure 10a-Figure 10b Compared with C3N5 / ZnO, the Ce-C3N5 / ZnO obtained after doping with Ce has higher adsorption performance and photocatalytic degradation performance. Under the equal doping ratio gradient set in this experiment, when the mass fraction of added cerium nitrate is lower than 1wt%, as the mass fraction of added cerium nitrate gradually increases, the photocatalytic activity of the composite material Ce-C3N5 / ZnO gradually increases. When the mass fraction of added cerium nitrate reaches 1wt%, the degradation rate is 91.53% and the degradation rate is 0.02852min -1 At this point, Ce-C3N5 / ZnO exhibited the best adsorption and photocatalytic performance. When the mass fraction of added cerium nitrate exceeded 1wt%, both the adsorption and photocatalytic activity of Ce-C3N5 / ZnO for methylene blue decreased, indicating that the photocatalytic performance of Ce-C3N5 / ZnO was optimal when the mass fraction of added cerium nitrate was 1wt%. This may be because Ce doping changes the structure of the C3N5 portion, narrowing its band gap and accelerating the electron-hole transfer rate.

[0105] 1.13Effect of the mass ratio of ZnO and Ce-C3N5 on photocatalytic performance

[0106] Using the method described in 1.1 above, Ce-C3N5 / ZnO with ZnO and Ce-C3N5 (the mass fraction of cerium nitrate added during preparation was 1 wt%) in mass ratios of 1:5, 1:3, 1:1, 3:1, and 5:1 were prepared. The photocatalytic performance of these Ce-C3N5 / ZnO was measured using the method described in 1.2 above. The mass ratio of Ce-C3N5 to ZnO added during the solvothermal synthesis affected the adsorption and photocatalytic degradation properties of Ce-C3N5 / ZnO.

[0107] like Figure 11a When the mass of added ZnO is greater than that of Ce-C3N5, the adsorption performance of Ce-C3N5 / ZnO will decrease slightly as the amount of ZnO added increases; when the amount of Ce-C3N5 added increases, the adsorption performance of the composite material will increase slightly. Figure 11b When the mass ratio of Ce-C3N5 and ZnO is 1:1, the first-order kinetic rate of Ce-C3N5 / ZnO is 0.03120min -1 , with the best adsorption and photocatalytic properties. Both ZnO and Ce-C3N5 play an important role in the photocatalytic performance of the composite material. During the composite process, a certain chemical bond surface may be formed between the two, which reduces the energy required for electron transition and thus improves the photocatalytic effect. When the Ce-C3N5:ZnO ratio is 1:1, the material surface provides more sites for photocatalytic reactions.

[0108] 1.14 Comparison of photocatalytic performance of ZnO, C3N5, Ce-C3N5, C3N5 / ZnO, and Ce-C3N5 / ZnO

[0109] Using methylene blue dye as a model pollutant, the photocatalytic effect of the prepared photocatalytic material under UV-visible light irradiation was evaluated using the method described in 1.2. Figure 12a As shown, the photocatalytic performance of pure ZnO and g-C3N5 is relatively poor, with degradation rates of methylene blue (MB) of 69% and 55%, respectively, after 90 minutes of irradiation. This indicates that the photoinduced electron-hole pair recombination rate is relatively fast in the ZnO and g-C3N5 single-component systems. Compared with the single-component materials, all doped and composite photocatalytic materials exhibit significantly better photocatalytic performance. Under 90 minutes of UV-visible light irradiation, the (1%) Ce-C3N5 / ZnO composite photocatalyst exhibited the highest MB degradation rate of 97%, which was significantly higher than Ce-C3N5 (76%), C3N5 / ZnO (77%), (0.25%) Ce-C3N5 / ZnO (92%), and (0.2%) Ce-C3N5 / ZnO (86%). Therefore, the effectively formed heterojunction, under the synergistic effect of ZnO and Ce-C3N5, plays a crucial role in the degradation of MB.

[0110] The pseudo-first-order kinetics of degradation under UV-visible light conditions is shown in Figure 12b As shown. The rate constant of (1%) Ce-C3N5 / ZnO composite photocatalytic material is 0.312min -1 , which are 5 times that of g-C3N5, 2.9 times that of ZnO, 3 times that of Ce-C3N5, and 2.5 times that of C3N5 / ZnO. The results show that the (1%) Ce-C3N5 / ZnO composite photocatalytic material exhibits good photocatalytic degradation efficiency in the degradation of methylene blue.

[0111] Figure 12c The effect of pH on the UV-visible light-assisted degradation of methylene blue in the presence of (1%) Ce-C3N5 / ZnO composite photocatalyst is shown. The photocatalytic activity of (1%) Ce-C3N5 / ZnO composite photocatalyst is highest at a pH of 13, degrading methylene blue to about 99%. When the pH decreases from 13 to 2, the degradation rate of (1%) Ce-C3N5 / ZnO composite photocatalyst decreases from 99% to 42%, indicating that the reducing environment is conducive to the adsorption and photodegradation of methylene blue. This is because when the pH is in the range of 2 to 4.8, the H at the active sites of the (1%) Ce-C3N5 / ZnO composite photocatalyst will be degraded. + Ion accumulation gives it a positive charge, which repels cationic organic compounds. In the pH range of 10-13, the photocatalyst acquires a more negatively charged surface, increasing the electrostatic attraction between the positively charged cationic dye and the negatively charged photocatalyst, leading to an increase in the photocatalytic efficiency of the photocatalyst.

[0112] 1.15 Photocatalytic material performance stability test

[0113] The stability of the material is also one of the important properties for degrading organic dyes. To test the stability of (1%) Ce-C3N5 / ZnO, under the same experimental conditions, after each photocatalytic test, (1%) Ce-C3N5 / ZnO was recovered, repeatedly washed with distilled water, and centrifuged to pour out the supernatant until the supernatant was almost free of dye color. Then, (1%) Ce-C3N5 / ZnO was dried and used as the material for the next cycle experiment. Figure 13a-13bAs shown, after five photocatalytic cycles, the photocatalytic degradation efficiency did not decrease significantly, with the degradation efficiency difference between each cycle ranging from approximately 2% to 4%. After the fifth cycle, the (1%) Ce-C3N5 / ZnO composite photocatalytic material had a degradation rate of 87.67%, maintaining good photocatalytic activity. These experimental results indicate that the frequent distilled water washings and extended use of the catalyst during the cyclic experiment may have reduced the surface area, thereby limiting the access of methylene blue to active sites and resulting in a slight decrease in photodegradation efficiency. However, the (1%) Ce-C3N5 / ZnO composite photocatalytic material still demonstrated good stability and reusability.

[0114] 1.16Main active substances in Ce-C3N5 / ZnO composite photocatalytic materials

[0115] The main active species in (1%) Ce-C3N5 / ZnO composite photocatalytic material were identified. Potassium iodide (KI), isopropyl alcohol (IPA) and benzoquinone (BQ) were used as trapping agents to capture holes (h + ), hydroxyl radical (·OH), superoxide anion (·O2 - ).like Figure 14a The degradation rate of methylene blue in Ce-C3N5 / ZnO without capture agent (1%) was 97%, and the degradation rate was 52% after adding potassium iodide (KI), indicating that the hole (h + ) plays a leading role in the photocatalytic degradation process; after adding isopropyl alcohol (IPA), the degradation rate is 67%, indicating that hydroxyl radicals (·OH) are an important factor affecting the degradation; the addition of benzoquinone (BQ) also has a certain inhibitory effect on the degradation of methylene blue catalyzed by (1%) Ce-C3N5 / ZnO, with a degradation rate of 81%, indicating that superoxide anions (·O2 - ) is one of the substances involved in photocatalytic degradation. The experimental results show that holes (h + ) is the main active substance in the photocatalytic degradation process, hydroxyl radicals (·OH) also play an important role, superoxide anions (·O2 - ) also made certain contributions.

[0116] In order to further verify the above active oxidizing species generated in (1%) Ce-C3N5 / ZnO material, ESR experiment was performed using DMPO as a probe to detect possible free radicals. Figure 14b-14d ,

[0117] Under dark conditions, h + The strong active substance signal was shown. With the increase of illumination time, the signal intensity gradually decreased. This is because TEMPO has strong oxidizing ability. + Oxidation to TEMPO +. This indicates that there are holes (h + ), (1%) Ce-C3N5 / ZnO composite photocatalytic material can retain a large amount of h + , indicating that the dominant role of the photocatalytic process is h + .

[0118] like Figure 14d As shown in the figure, (1%) Ce-C3N5 / ZnO has almost no characteristic signal of active species under dark conditions. After 10 minutes of visible light irradiation, DMPO-·O2 - Significant characteristic peaks appeared in the photocatalytic reaction, indicating that more photogenerated carriers were generated, which is of great significance for the photocatalytic reaction.

[0119] 1.17 Semiconductor type, flat band potential, and valence band potential of ZnO and Ce-C3N5

[0120] The semiconductor type and flat band potential of ZnO and Ce-C3N5 were determined and studied based on the Mott-Schott equation. Figure 15 and Figure 16 It can be seen that the slopes of the Mott-Schott curves of ZnO and Ce-C3N5 are positive, indicating that ZnO and Ce-C3N5 are n-type semiconductors. The flat band potentials of ZnO and Ce-C3N5 are approximately -0.49eV and -0.59eV (Ag / AgCl pH = 7) respectively, which correspond to the normal hydrogen electrode conduction band potentials of -0.29eV and -0.39eV (NHE pH = 7) respectively. Figure 5b It can be seen that the band gap (Eg) of ZnO and Ce-C3N5 are 2.71eV and 1.77eV, respectively. The calculated valence band potentials of ZnO and Ce-C3N5 are 2.42eV and 1.38eV, respectively.

[0121] 2 Conclusion

[0122] In the present embodiment, Ce-C3N5 / ZnO prepared by calcination and solvent thermal method is a composite photocatalytic material. The results of infrared spectroscopy and ultraviolet characterization measurements prove that Ce, C3N5, and ZnO can be successfully doped. It is not a simple physical mixture. The band gap of Ce-C3N5 / ZnO formed after doping is narrower and the light response range is increased. The above-mentioned catalytic methylene blue degradation experiment of the present embodiment shows that under suitable conditions, the catalytic efficiency of Ce-C3N5 / ZnO is higher than that of photocatalytic materials such as ZnO, C3N5, Ce-C3N5, and C3N5 / ZnO. The photocurrent test shows that the separation rate of photogenerated electrons in Ce-C3N5 / ZnO is faster. In the stability test, Ce-C3N5 / ZnO showed high stability and can be recycled and collected for use. The degradation rate test under different solution pH conditions shows that Ce-C3N5 / ZnO can work well under alkaline conditions. The present invention provides a green, efficient and stable photocatalyst, which has a good development prospect in degrading organic pollutants in water.

Claims

1. A method for preparing a Ce-C3N5 / ZnO composite photocatalytic material, characterized in that: The steps include: Step A: Adding 3-amino-1,2,4-triazole to a cerium nitrate solution, heating and stirring until the water evaporates to obtain a solid product; grinding the solid product and calcining it until the calcination is completed to obtain Ce-C3N5; the mass ratio of the added amount of 3-amino-1,2,4-triazole to the cerium nitrate in the cerium nitrate solution is 1.25 to 20:1; Step B: adding anhydrous ethanol to the soluble zinc salt solution and stirring to obtain a mixed solution a; adding sodium hydroxide solution dropwise to the mixed solution a, and after the sodium hydroxide solution is completely added, stirring the obtained mixed system at room temperature and then performing ultrasonic treatment and heating treatment in sequence; After the heating treatment is completed, the supernatant in the reaction system is discarded to obtain a solid precipitate; The solid precipitate is washed, dried and ground to obtain ZnO; Step C: dispersing ZnO in anhydrous ethanol to obtain a ZnO dispersion; adding Ce-C3N5 to the ZnO dispersion to obtain a mixed raw material dispersion, wherein the mass ratio of ZnO to Ce-C3N5 in the mixed raw material dispersion is 0.2 to 5:1; placing the mixed raw material dispersion in a closed container for a solvent thermal reaction; after the reaction is completed, performing solid-liquid separation, washing, drying and grinding the solid material obtained by the solid-liquid separation to obtain a Ce-C3N5 / ZnO composite photocatalytic material.

2. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 1, characterized in that: In step A, the mass fraction of cerium nitrate in the cerium nitrate solution is 0.25 wt% to 4 wt%; the temperature during heating and stirring is 70 to 90°C; the calcination conditions are: heating to 520 to 550°C at a heating rate of 5°C / min and then keeping the temperature for 180 to 220 minutes; the particle size of the powder formed by the solid product after grinding is in the range of 1 to 100 nm.

3. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 2, characterized in that: In step A, the mass fraction of cerium nitrate in the cerium nitrate solution is 1.0 wt %; and the ratio of the amount of 3-amino-1,2,4-triazole added to the mass of cerium nitrate in the cerium nitrate solution is 5:

1.

4. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 2, characterized in that: In step A, the temperature during heating and stirring is 80°C; the calcination conditions are: heating to 520°C at a heating rate of 5°C / min and then keeping the temperature for 180 min.

5. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 1, characterized in that: In step B, the soluble zinc salt solution is a 0.3-0.4 mol / L zinc nitrate solution, and the volume ratio of the zinc nitrate solution to anhydrous ethanol is 1-2:1; the molar concentration of the sodium hydroxide solution is 1-1.33 mol / L; the sodium hydroxide solution is added dropwise over 5-10 minutes; the volume ratio of the mixed solution a to the sodium hydroxide solution is 10:(3-4); the stirring time of the mixed system at room temperature is 20-30 minutes, and the stirring rate at room temperature is 400-500 rpm; the ultrasonic treatment time is 30-50 minutes; the heating time of the heat treatment is 600-660 minutes, and the heating temperature is 90-110°C; the solid precipitate is washed alternately with water and alcohol, and then dried at 60-70°C for 10-12 hours; the ZnO powder obtained after grinding the solid precipitate has a particle size of 10-20 nm.

6. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 5, characterized in that: In step B, the soluble zinc salt solution is a 0.33 mol / L zinc nitrate solution, and the volume ratio of the zinc nitrate solution to anhydrous ethanol is 1.5:1; the molar concentration of the sodium hydroxide solution is 1.33 mol / L; the sodium hydroxide solution is added dropwise over 10 minutes; the volume ratio of the mixed solution a to the sodium hydroxide solution is 10:3; the stirring time of the mixed system at room temperature is 30 minutes, and the stirring rate at room temperature is 400 rpm; the treatment time of the ultrasonic treatment is 30 minutes; the heating time of the heat treatment is 600 minutes, and the heating temperature is 100°C; the solid precipitate is washed alternately with water and alcohol and then dried at 60°C for 12 hours.

7. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 1, characterized in that: In step C, ZnO is dispersed in anhydrous ethanol and stirred at room temperature for 10 to 15 minutes to obtain a ZnO dispersion; the mass fraction of ZnO in the ZnO dispersion is 0.3 wt% to 0.4 wt%; before performing a solvothermal reaction, the raw material dispersion is stirred and mixed at room temperature for 50 to 70 minutes; the solvothermal reaction temperature is 80 to 140°C, and the reaction time is 360 to 840 minutes; the solid material is washed with anhydrous ethanol and then dried at 60 to 70°C for 10 to 12 hours; and the particle size of the Ce-C3N5 / ZnO composite photocatalytic material obtained after grinding is 2 to 10 nm.

8. The method for preparing the Ce-C3N5 / ZnO composite photocatalytic material according to claim 7, characterized in that: In step C, ZnO is dispersed in anhydrous ethanol and stirred at room temperature for 10 minutes to obtain a ZnO dispersion; the mass fraction of ZnO in the ZnO dispersion is 0.33 wt%; the mass ratio of ZnO to Ce-C3N5 in the mixed raw material dispersion is 1:1, and the mixed raw material dispersion is stirred at room temperature for 60 minutes before performing a solvothermal reaction; the solvothermal reaction temperature is 140°C, and the reaction time is 600 minutes; the solid material is washed with anhydrous ethanol and then dried at 70°C for 12 hours.

9. The method for preparing a Ce-C3N5 / ZnO composite photocatalytic material according to any one of claims 1 to 8, characterized in that: In step A, the mass fraction of cerium nitrate in the cerium nitrate solution is 1.0 wt %; the mass ratio of 3-amino-1,2,4-triazole to cerium nitrate in the cerium nitrate solution is 5:1; the temperature during heating and stirring is 80°C; the calcination conditions are: heating to 520°C at a heating rate of 5°C / min and holding for 180 min; the particle size of the powder formed by the ground solid product ranges from 1 to 100 nm; In step B, the soluble zinc salt solution is a 0.33 mol / L zinc nitrate solution, and the volume ratio of the zinc nitrate solution to anhydrous ethanol is 1.5:1; the molar concentration of the sodium hydroxide solution is 1.33 mol / L; the sodium hydroxide solution is added dropwise over 10 minutes; the volume ratio of the mixed solution a to the sodium hydroxide solution is 10:3; the stirring time of the mixed system at room temperature is 30 minutes, and the stirring rate at room temperature is 400 rpm; the ultrasonic treatment time is 30 minutes; the heating time of the heat treatment is 600 minutes, and the heating temperature is 100°C; the solid precipitate is washed alternately with water and alcohol and then dried at 60°C for 12 hours; the ZnO powder obtained after grinding the solid precipitate has a particle size of 10 to 20 nm; In step C, ZnO is dispersed in anhydrous ethanol and stirred at room temperature for 10 minutes to obtain a ZnO dispersion; the mass fraction of ZnO in the ZnO dispersion is 0.33 wt%; the mass ratio of ZnO to Ce-C3N5 in the mixed raw material dispersion is 1:1, and the mixed raw material dispersion is stirred at room temperature for 60 minutes before the solvothermal reaction; the solvothermal reaction temperature is 140°C and the reaction time is 600 minutes; the solid material is washed with anhydrous ethanol and then dried at 70°C for 12 hours; the particle size of the Ce-C3N5 / ZnO composite photocatalytic material obtained after grinding is 2 to 10 nm.

10. An application of Ce-C3N5 / ZnO composite photocatalytic material, characterized in that: The Ce-C3N5 / ZnO composite photocatalytic material prepared by the preparation method of the Ce-C3N5 / ZnO composite photocatalytic material as described in claim 1 is used to catalytically decompose organic pollutants.

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