Preparation method and application of a multi-level pore honeycomb nitrogen-doped carbon supported cobalt nanoparticle catalyst

Abstract

This invention discloses a method for preparing and applying a hierarchical porous honeycomb-structured nitrogen-doped carbon-supported cobalt nanoparticle catalyst, belonging to the field of environmental functional material preparation and water pollution control technology. The resulting Co@pHNC catalyst possesses a honeycomb hierarchical porous structure, a nitrogen-doped carbon framework, and Co-N... x Coordination active sites. The presence of honeycomb-like hollow channels facilitates the provision of a spatially confined environment and open material transport pathways, accelerating the diffusion and local enrichment of persulfate and tetracycline molecules to the active interface; Co-N in the nitrogen-doped carbon framework. x The formation of coordination structures facilitates the anchoring of cobalt active centers, inhibits nanoparticle aggregation and metal leaching, and simultaneously regulates the local electron density of cobalt sites, promoting interfacial electron transfer and Co. 2+ / Co 3+ The redox cycle efficiently activates persulfate to generate reactive oxygen species, enabling rapid and deep degradation of tetracycline. This catalyst possesses advantages such as high activity, good stability, and recyclability, showing promising application prospects in the treatment of antibiotic wastewater.

Description

Technical Field

[0001] This invention relates to the fields of environmental functional material preparation and water pollution control technology, specifically to a method for preparing and applying a multi-level porous honeycomb nitrogen-rich doped carbon cobalt nanoparticle catalyst. Background Technology

[0002] Tetracycline (TC), a typical broad-spectrum antibiotic, has been widely used in human medicine, livestock farming, and aquaculture due to its excellent antibacterial properties and low production cost. However, with the rapid development of the pharmaceutical and aquaculture industries, the residues and accumulation of tetracycline antibiotics in aquatic environments have become an increasingly serious global environmental problem. These pollutants are characterized by their recalcitrant biodegradability, high ecotoxicity, and ease of inducing the spread of resistance genes, posing a potential threat to aquatic ecosystems and human health. Therefore, developing efficient and sustainable water treatment technologies to achieve their deep removal is particularly urgent. Advanced oxidation technologies based on persulfate have attracted widespread attention due to their ability to generate highly reactive oxidizing species; the core of this technology lies in developing efficient and stable heterogeneous catalysts.

[0003] Currently, the main methods for treating tetracycline wastewater include physical, chemical, and biological methods. Adsorption is simple to operate, but essentially only achieves interphase transfer of pollutants; regeneration and disposal after adsorption saturation are difficult, and coexisting ions and natural organic matter compete for adsorption sites, leading to decreased removal efficiency. Membrane separation can achieve high-efficiency retention, but membrane fouling is a significant problem, and the concentrate still requires further treatment, failing to fundamentally eliminate pollutants. Traditional biological treatment processes are sensitive to the antibacterial properties of tetracycline, inhibiting microbial activity, resulting in unstable treatment efficiency, and the risk of resistance gene transmission is difficult to control. While Fenton and Fenton-like oxidation methods can generate highly oxidizing hydroxyl radicals (·OH), traditional homogeneous Fenton systems are limited by strict pH application ranges, large iron sludge production, and the safety risks of H2O2 storage and transportation. Heterogeneous Fenton catalysts still face problems such as low oxidant utilization and loss of active components. A single technology cannot simultaneously achieve efficiency, stability, and economy; therefore, the development of new, highly efficient advanced oxidation technologies is urgently needed.

[0004] Advanced oxidation processes based on persulfate (PMS) activation are a rapidly developing new type of Fenton-like technology in recent years. By activating PMS through transition metals, heat, alkalis, ultraviolet light, or carbon materials, sulfate radicals (SO4·4·4) can be generated in situ. - ), hydroxyl radicals (·OH), superoxide radicals (O2· - ) and singlet oxygen ( 1 Cobalt-based materials contain various reactive oxygen species, including O2. 2+ / Co 3+Cobalt oxides are widely recognized as one of the most effective heterogeneous activation systems due to their strong reversible redox cycle capability, strong PMS adsorption, and outstanding interfacial electron transfer ability. They have been extensively studied because of their good thermal stability and catalytic activity. However, traditional cobalt-based catalysts still face many bottlenecks in practical applications: nanoparticles tend to aggregate, leading to reduced utilization of active sites; and the leaching of cobalt ions during the reaction may cause secondary environmental risks.

[0005] To overcome the aforementioned limitations, researchers have explored various strategies. The construction of hierarchical porous structures has been shown to improve mass transfer efficiency; for example, materials with macroporous-mesoporous-microporous composite structures can provide unobstructed diffusion pathways for the reaction. Increasing the nitrogen doping level is believed to enhance the interaction between the metal and the support, thereby stabilizing metal nanoparticles. Furthermore, methods such as carbon layer encapsulation or surface modification can also suppress metal leaching to some extent. However, current technologies still struggle to achieve a synergistic balance between rapid mass transfer and long-term stability while maintaining a high density of active sites. Therefore, developing a novel cobalt-based catalytic material that combines high activity, high stability, and easy recyclability is of significant scientific and practical value for promoting the practical application of PMS activation technology in antibiotic wastewater treatment. Summary of the Invention

[0006] This invention provides a method for preparing and applying a hierarchical porous honeycomb-structured nitrogen-doped carbon-supported cobalt nanoparticle catalyst. Using monodisperse silica (SiO2) nanospheres as a hard template, a nitrogen-containing precursor is deposited on their surface through precipitation polymerization. The template is then removed via high-temperature carbonization and acid etching to form a honeycomb-structured porous nitrogen-doped carbon framework (pHNC). Cobalt ions are further loaded and subjected to a second calcination oxidation process to obtain a honeycomb-structured porous carbon-doped nitrogen-supported cobalt oxide catalyst (Co@pHNC). This catalyst utilizes the confinement effect of the honeycomb hollow structure and the anchoring effect of the nitrogen-doped carbon framework to achieve high dispersion and structural stability of the cobalt active sites. This catalyst has been applied to activate persulfate (PMS) for the degradation of tetracycline (TC), providing a material solution with high activity, stability, and economy for the application of advanced oxidation technologies in practical wastewater treatment.

[0007] The technical solution adopted in this invention is: a method for preparing a multi-level porous honeycomb-shaped nitrogen-rich doped carbon cobalt nanoparticle catalyst, comprising the following steps:

[0008] S1. Using silica nanospheres as a hard template, the silica nanospheres are dispersed in an organic medium. Under a protective atmosphere, the silica nanospheres are surface modified with an organosilane surface modifier to form an organic functional layer on the surface of the silica nanospheres that can interact with the subsequent polymerization system, thereby obtaining modified silica nanospheres v-SiO2.

[0009] S2. The modified silica nanospheres v-SiO2 are dispersed in a polymerization medium. Under the action of a free radical polymerization initiator, nitrogen-containing polymeric monomers are polymerized on the surface of the modified silica nanospheres in a protective atmosphere, forming a nitrogen-containing polymer coating layer on the surface of the modified silica nanospheres, thus obtaining a silica / nitrogen-containing polymer composite material SiO2@Polymer.

[0010] S3. The SiO2@Polymer is subjected to a first heat treatment under a protective atmosphere to carbonize the nitrogen-containing polymer coating layer to form a nitrogen-doped carbon skeleton, thereby obtaining the silicon dioxide / nitrogen-doped carbon composite material SiO2@NC.

[0011] S4. Chemically etch the SiO2@NC using an etching solution to at least partially remove the silicon dioxide nanosphere hard template, so that the nitrogen-doped carbon framework retains the pores formed by the silicon dioxide nanosphere hard template, and obtains a nitrogen-doped carbon material pHNC with a honeycomb hierarchical porous structure.

[0012] S5. The pHNC and cobalt precursor are mixed and dispersed in a solvent, so that the cobalt precursor is loaded on the pHNC. After removing the solvent, a second heat treatment is performed to disperse the cobalt active component at the nanoscale on the surface and / or channels of the nitrogen-doped carbon framework, thereby obtaining a hierarchical porous honeycomb nitrogen-doped carbon-supported cobalt nanoparticle catalyst.

[0013] Specifically, the silica nanospheres are prepared by the following method:

[0014] Ammonia, deionized water, ethanol and silicon-containing precursor were mixed and stirred to react. After the reaction was completed, solid-liquid separation and drying were performed to obtain silica nanospheres (SiO2).

[0015] The ratio of ammonia, deionized water, ethanol to silicon-containing precursor is 2-4 mL: 5-15 mL: 80-100 mL: 4-8 mL;

[0016] The silicon-containing precursor is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, polysiloxane, and sodium silicate;

[0017] The reaction temperature is 20–40°C, and the reaction time is 1–3 h; the drying is vacuum drying, with a vacuum drying temperature of 60–80°C and a vacuum drying time of 12–24 h.

[0018] Specifically, in S1, the ratio of the amount of silica nanospheres, the organic medium, and the organosilane surface modifier is 1.0–3.0 g: 100–300 mL: 4–8 mL;

[0019] The organic medium is toluene;

[0020] The organosilane surface modifier is selected from one or more of γ-(methacryloyloxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and vinyltriacetoxysilane.

[0021] The protective atmosphere is a nitrogen atmosphere. After the nitrogen atmosphere is introduced for 20 to 50 minutes, the surface modification reaction is carried out. The temperature of the surface modification reaction is 80 to 100°C, and the reaction time is 20 to 28 hours.

[0022] After the reaction was completed, the sample was washed with toluene and collected by centrifugation. It was then vacuum dried at 60–80 °C for 12–24 h to obtain the modified silica nanospheres v-SiO2.

[0023] Specifically, in S2, the ratio of the modified silica nanospheres v-SiO2, the polymerization medium, the free radical polymerization initiator, and the nitrogen-containing polymerization monomer is 0.1–0.4 g: 40–80 mL: 60–100 mg: 0.6–1.0 g;

[0024] The polymerization medium is acetonitrile;

[0025] The free radical polymerization initiator is an azo-based free radical polymerization initiator, selected from one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, azobiscyclohexylformonitrile, and dimethyl azobisisobutyrate;

[0026] The nitrogen-containing polymeric monomer is selected from one or more of acrylamide, methylenebisacrylamide, N-isopropylacrylamide, N-vinylpyrrolidone, acrylonitrile, and dimethylaminoethyl methacrylate.

[0027] Specifically, in step S2, the modified silica nanospheres v-SiO2 are dispersed in acetonitrile, the free radical polymerization initiator is added and ultrasonically dispersed, the nitrogen-containing polymerization monomer is added and nitrogen gas is introduced for 20-50 minutes.

[0028] The first stage polymerization reaction was then carried out at 40–60°C and 100–120 rpm for 4–8 hours, and then the temperature was raised to 50–70°C and the second stage polymerization reaction was carried out at 100–120 rpm for 20–28 hours.

[0029] After the reaction was completed, the solid was separated by centrifugation and washed with acetonitrile. Then, it was vacuum dried at 60-80℃ for 12-24 h to obtain the SiO2@Polymer.

[0030] Specifically, in step S3, the SiO2@Polymer is placed in a tube furnace and subjected to the first heat treatment under a nitrogen atmosphere.

[0031] The temperature of the first heat treatment is 400-900℃, the heating rate is 5℃ / min, and the holding time is 1-3h; after the heat treatment is completed, it is naturally cooled under a protective atmosphere to obtain SiO2@NC.

[0032] Specifically, in S4, the SiO2@NC is dispersed in an etching system composed of ethanol and etching solution and then stirred and etched.

[0033] The ratio of SiO2@NC, ethanol, and etching solution is 0.2–0.6 g: 8–10 mL: 10–12 mL.

[0034] The etching solution is 40wt% hydrofluoric acid (HF), and the etching time is 20-28h;

[0035] After etching, solid-liquid separation was performed and the material was washed with ethanol to obtain a nitrogen-doped carbon material pHNC with a honeycomb hierarchical porous structure.

[0036] Specifically, in S5, the cobalt precursor is a soluble cobalt salt, which is selected from one or more of cobalt nitrate hexahydrate Co(NO3)2·6H2O, cobalt chloride hexahydrate CoCl2·6H2O, cobalt sulfate heptahydrate CoSO4·7H2O, and cobalt acetate tetrahydrate Co(CH3COO)2·4H2O;

[0037] The ratio of pHNC, the cobalt precursor, and the solvent is 0.1–0.3 g: 0.4–0.6 g: 60–100 mL, and the solvent is ethanol.

[0038] Specifically, in step S5, the pHNC and the cobalt precursor are added to ethanol and ultrasonically dispersed to ensure that the cobalt precursor and the pHNC are in full contact. Then, an oil bath treatment is performed at 80-100°C for 5-7 hours to remove at least part of the solvent.

[0039] After washing the obtained pHNC of the supported cobalt precursor, it was placed in a tube furnace for the second heat treatment under a nitrogen atmosphere.

[0040] The second heat treatment is performed at a temperature of 300–800°C, with a heating rate of 5°C / min and a holding time of 1–3 h. After the heat treatment, the material is allowed to cool naturally to obtain the multi-level porous honeycomb nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst.

[0041] Specifically, the silica nanospheres maintain a hard template structure during the first heat treatment in S3 and are removed in S4, so that a honeycomb-like cavity corresponding to the silica nanosphere template is formed in the nitrogen-doped carbon framework; the honeycomb-like cavity and the pores in the nitrogen-doped carbon framework together form a multi-level porous mass transfer structure.

[0042] The cobalt precursor is loaded onto the pHNC after the silica nanosphere hard template is removed, and is then subjected to the second heat treatment to form a cobalt-containing nano-active component dispersed on the surface and / or in the pores of the nitrogen-doped carbon framework.

[0043] The resulting catalyst is denoted as Co@pHNC-X℃, where X represents the temperature of the second heat treatment.

[0044] This invention also provides the application of a hierarchical porous honeycomb nitrogen-rich doped carbon cobalt-supported nanoparticle catalyst in the activation of persulfate for the degradation of tetracycline pollutants. The catalyst is a hierarchical porous honeycomb nitrogen-rich doped carbon cobalt-supported nanoparticle catalyst prepared by the above-described preparation method. The catalyst is added to water containing tetracycline pollutants and dispersed, followed by the addition of persulfate. The persulfate is activated by the synergistic effect of the cobalt-containing active sites and the nitrogen-doped carbon framework of the catalyst to oxidatively degrade the tetracycline pollutants.

[0045] The beneficial effects of this invention are as follows:

[0046] (1) Using monodisperse SiO2 nanospheres as hard templates, a honeycomb hierarchical porous structure is constructed by template replication, which provides a large specific surface area and abundant material transport channels. At the same time, the hollow channels provide a spatial confinement environment, which is conducive to the rapid entry of PMS and tetracycline into the active interface, shortening the diffusion path and improving the interface reaction efficiency.

[0047] (2) In the prepared Co@pHNC catalyst, the nitrogen coordination sites of the nitrogen-doped carbon framework can effectively anchor cobalt atoms, forming a highly catalytically active Co-N x Coordination configuration inhibits the aggregation and leaching of cobalt nanoparticles; the confinement effect of the hollow structure in the carbon matrix and the electron transport effect of the conductive network synergistically promote electron transfer between cobalt sites and reactants, thereby improving the activation efficiency of PMS.

[0048] (3) The catalyst can efficiently activate PMS at room temperature and pressure and within a wide pH range without the need for external energy or auxiliary reagents. The reaction conditions are mild and energy consumption is low. Moreover, the catalytic activity has strong resistance to common inorganic anions and natural organic matter in water, making it suitable for actual wastewater treatment scenarios.

[0049] (4) The synthesis method adopted in this invention has the advantages of readily available raw materials, controllable process and good reproducibility. By precisely controlling key parameters such as template agent dosage, pyrolysis temperature and doping ratio, the directional control of catalyst structure and performance can be achieved, providing technical feasibility for large-scale preparation. Attached Figure Description

[0050] Figure 1 The image shows scanning electron microscope (SEM) images of pHNC (a1-a3) and Co@pHNC-500℃ (b1-b3) in Example 1 of this invention.

[0051] Figure 2 The images are transmission electron microscope (TEM) images of pHNC (a1-a3) and Co@pHNC-500℃ (b1-b3) in Example 1 of this invention.

[0052] Figure 3 The high-resolution lattice image (a), high-angle annular dark-field imaging (b), and energy-dispersive X-ray spectrum (c) of Co@pHNC-500℃ prepared in Example 1 of this invention are shown.

[0053] Figure 4 The N2 adsorption-desorption curves (a) and pore size distribution diagrams (b) of the pHNC, Co@pHC and Co@pHNC-500℃ catalysts prepared in Example 1 of this invention are shown.

[0054] Figure 5 The image shows the Raman spectrum of the Co@pHNC-500℃ catalyst prepared in Example 1 of this invention.

[0055] Figure 6 The X-ray diffraction patterns are those of the pHNC and Co@pHNC-500℃ catalysts prepared in Example 1 of this invention.

[0056] Figure 7 The high-resolution spectra of the C1s region (a), O1s region (b), N1s region (c), and Co2p region (d) of the pHNC and Co@pHNC-500℃ catalysts prepared in Example 1 of this invention are shown. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the scope of protection of the present invention is not limited thereto.

[0058] like Figures 1-7 As shown, this invention provides a method for preparing a hierarchical porous honeycomb-shaped nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst, comprising the following steps:

[0059] S1. Using silica nanospheres as a hard template, the silica nanospheres are dispersed in an organic medium. Under a protective atmosphere, the silica nanospheres are surface modified with an organosilane surface modifier to form an organic functional layer on the surface of the silica nanospheres that can interact with the subsequent polymerization system, thereby obtaining modified silica nanospheres v-SiO2.

[0060] S2. The modified silica nanospheres v-SiO2 are dispersed in a polymerization medium. Under the action of a free radical polymerization initiator, nitrogen-containing polymeric monomers are polymerized on the surface of the modified silica nanospheres in a protective atmosphere, forming a nitrogen-containing polymer coating layer on the surface of the modified silica nanospheres, thus obtaining a silica / nitrogen-containing polymer composite material SiO2@Polymer.

[0061] S3. The SiO2@Polymer is subjected to a first heat treatment under a protective atmosphere to carbonize the nitrogen-containing polymer coating layer to form a nitrogen-doped carbon skeleton, thereby obtaining the silicon dioxide / nitrogen-doped carbon composite material SiO2@NC.

[0062] S4. Chemically etch the SiO2@NC using an etching solution to at least partially remove the silicon dioxide nanosphere hard template, so that the nitrogen-doped carbon framework retains the pores formed by the silicon dioxide nanosphere hard template, and obtains a nitrogen-doped carbon material pHNC with a honeycomb hierarchical porous structure.

[0063] S5. The pHNC and cobalt precursor are mixed and dispersed in a solvent, so that the cobalt precursor is loaded on the pHNC. After removing the solvent, a second heat treatment is performed to disperse the cobalt active component at the nanoscale on the surface and / or channels of the nitrogen-doped carbon framework, thereby obtaining a hierarchical porous honeycomb nitrogen-doped carbon-supported cobalt nanoparticle catalyst.

[0064] Example 1:

[0065] 1. Preparation of nitrogen-doped cobalt-supported carbon nanoparticles Co@pHNC-500℃ with hierarchical porous honeycomb structure.

[0066] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and stirred at 30 °C for 1 h. Then, the mixture was washed with ethanol and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0067] (2) Weigh 1 g of SiO2 nanospheres and add them to 100 mL of toluene. Purge with nitrogen for 30 min, then add 6.0 mL of γ-methacryloyloxypropyl (KH-570) dropwise using a reflux apparatus. Heat the mixture and maintain it at 90 °C for 24 h. Wash the resulting solution with toluene, collect the precipitate by centrifugation, and then dry it at 80 °C for 24 h. The resulting product is v-SiO2.

[0068] (2) Weigh 0.2 g v-SiO2, 0.08 g azobisisobutyronitrile (AIBN), 0.8 g polymer monomers (acrylamide and methylenebisacrylamide), and 60 mL acetonitrile into a 100 mL single-necked flask. After purging with nitrogen for 30 min, the mixture is ultrasonically dispersed and then placed in a water bath shaker. The mixture is shaken at 50 °C for 6 h, and then the temperature is increased to 60 °C for another 24 h. The product is centrifuged, washed three times with acetonitrile, and then dried at 70 °C for 12 h. The product SiO2@Polymer is obtained.

[0069] (3) The SiO2@Polymer sample was placed in a tube furnace and carbonized at 600°C in a nitrogen atmosphere for 2 hours at a heating rate of 5°C / min. The resulting product was SiO2@NC.

[0070] (4) Weigh 0.5g SiO2@NC, add 9.33mL ethanol and 10.67mL 40wt%HF, and stir at room temperature for 24h. After the reaction is complete, wash the resulting solution with ethanol, collect the precipitate by centrifugation, and obtain the product pHNC;

[0071] (5) Dissolve 0.2 g pHNC and 0.5821 g Co(NO3)2·6H2O in 80 mL of ethanol, sonicate for 30 minutes, then evaporate in an oil bath at 90 °C for 6 hours, and then place in a tube furnace and calcine at 500 °C for 2 hours under a nitrogen atmosphere at a heating rate of 5 °C / min. The resulting product is Co@pHNC-500 °C.

[0072] Depend on Figure 1 Scanning electron microscopy (SEM) images of pHNC (a1-a3) and Co@pHNC-500℃ (b1-b3) show that the materials exhibit a distinct honeycomb-like porous morphology, with interconnected pore walls forming a three-dimensional open framework structure. A relatively uniform pore distribution is observed in localized areas, indicating that the construction strategy using SiO2 nanospheres as a hard template effectively replicates the template morphology and retains a stable porous framework after etching away the SiO2. Furthermore, after loading cobalt and undergoing calcination at 500℃, the Co@pHNC-500℃ samples perfectly preserved their original honeycomb-like three-dimensional framework.

[0073] Depend on Figure 2Transmission electron microscopy of pHNC(a1-a3), Co@pHNC-500℃(b1-b3) Figure 1 The study revealed the hollow confined structure inside the material. The unloaded cobalt pHNC samples (a1-a3) exhibited a honeycomb-like aggregate morphology formed by a large number of tightly stacked and interconnected hollow spherical shells, with obvious light and dark contrast in local areas. This clearly shows that the nitrogen-doped carbon skeleton constructed using SiO2 hard template successfully formed regular and open interconnected channels after template etching, providing excellent channels for material transport. The Co@pHNC-500℃ samples (b1-b3) still firmly maintained the original hollow honeycomb skeleton without structural collapse.

[0074] Depend on Figure 3 The high-resolution lattice image (a) of Co@pHNC-500℃ shows locally clear lattice fringes, with intergranular spacings of 0.28 nm and 0.24 nm, indicating that cobalt oxide nanocrystals have been successfully formed and anchored on the carbon framework surface. The high-angle annular dark-field image (b) shows relatively clear bright spot regions, indicating that elemental Co has been effectively loaded onto the carbon matrix. The energy-dispersive X-ray spectroscopy (c) shows that C, N, O, and Co elements are relatively uniformly distributed in the sample.

[0075] Depend on Figure 4 The N2 adsorption / desorption diagram (a) and pore size distribution diagram (b) show that the prepared catalyst exhibits a distinct microporous-mesoporous-macroporous hierarchical structure. While the adsorption capacity decreases after Co loading, the hierarchical porous framework remains stable and interconnected.

[0076] Depend on Figure 5 Located at 1340 cm in the Raman spectrum -1 The characteristic peak of the D band at 1580 cm⁻¹ and the peak at 1580 cm⁻¹ -1 The characteristic peak of the G band at that location was calculated to yield I. D / I G =1.131, indicating that the prepared catalyst has certain carbon defects.

[0077] Depend on Figure 6 The X-ray diffraction pattern of the pHNC sample shows broadened diffraction peaks around 24°-26°, which can be attributed to the (002) crystal plane diffraction peaks of amorphous carbon or low-graphitized carbon materials, indicating that the sample has formed a porous structure dominated by a carbon skeleton after template etching and high-temperature carbonization. After loading Co, Co@pHNC-500℃ shows obvious diffraction peaks at approximately 19.0°, 36.8°, 38.5° and 44.8°, which are attributed to the (111), (220), (311) and (400) crystal planes of Co3O4, respectively.

[0078] Depend on Figure 7The high-resolution spectra of the C1s region (a), O1s region (b), N1s region (c), and Co2p region (d) of the pHNC and Co@pHNC-500℃ catalysts prepared in Example 1 confirm that cobalt species have been successfully loaded onto the pHNC carbon framework. Furthermore, they reveal abundant nitrogen- and oxygen-containing sites on the sample surface, as well as crucial Co-N sites. x Coordination structure.

[0079] 2. Catalytic activity test.

[0080] 2 mg of TC was weighed and dispersed in 100 mL of deionized water. Then, 10 mg of Co@pHNC-500℃ was added and stirred until homogeneous. 1 mM PMS was weighed and added to the mixture. The reaction was carried out at 20℃ and atmospheric pressure. 3 mL samples were taken at various time points, and 3 mL of methanol was added to stop the reaction. The test samples were filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The test sample solutions were detected using a UV spectrophotometer with a quartz absorption cell. The UV absorption peak of TC was approximately between 350-370 nm. The results showed that the degradation rate of TC reached 98.6% after 15 min of reaction.

[0081] 3. Regeneration performance test.

[0082] In this invention, nitrogen-doped cobalt-supported carbon nanoparticles (Co@pHNC-500℃) with a hierarchical porous honeycomb structure are obtained by centrifugation, separation, and drying. The recovered catalyst is then reintroduced into the aforementioned catalytic experiments to test its catalytic effect; five regeneration experiments are conducted using this method. The detection methods and experimental conditions for the obtained liquid products are the same as those for the aforementioned catalytic experiments. The results show that the catalyst activity loss during regeneration is low; during the first to fifth regeneration experiments, the degradation rate of TC decreases from 98.6% to 88.3%.

[0083] Example 2:

[0084] 1. Preparation of nitrogen-doped cobalt-supported carbon nanoparticles Co@pHNC-600℃ with hierarchical porous honeycomb structure.

[0085] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and stirred at 30 °C for 1 h. Then, the mixture was washed with ethanol and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0086] (2) Weigh 1 g of SiO2 nanospheres and add them to 100 mL of toluene. Purge with nitrogen for 20 min, then add 6.0 mL of γ-methacryloyloxypropyl (KH-570) dropwise using a reflux apparatus. Heat the mixture and maintain it at 90 °C for 24 h. Wash the resulting solution with toluene, collect the precipitate by centrifugation, and then dry it at 70 °C for 24 h. The resulting product is v-SiO2.

[0087] (3) Take 0.2 g v-SiO2, 0.08 g azobisisobutyronitrile (AIBN), 0.8 g polymer monomers (acrylamide and methylenebisacrylamide), and 60 mL acetonitrile and add them to a 100 mL single-necked flask. After blowing nitrogen gas for 30 minutes, shake the reaction at 50 °C for 6 h, then raise the temperature to 60 °C and continue the reaction for 24 h. Centrifuge the product, wash it three times with acetonitrile, and then dry it at 70 °C for 12 h. Obtain the product SiO2@Polymer;

[0088] (4) The SiO2@Polymer sample was placed in a tube furnace and carbonized at 600°C in a nitrogen atmosphere for 2 hours at a heating rate of 5.0°C / min. The resulting product was SiO2@NC.

[0089] (5) Weigh 0.5 g SiO2@NC, add 9.33 mL ethanol and 10.67 mL 40 wt% HF, and treat for 24 h. Then wash with ethanol. Obtain the product pHNC;

[0090] (6) Dissolve 0.2 g pHNC and 0.5821 g Co(NO3)2·6H2O in 80 mL of ethanol, sonicate for 30 min, then evaporate in an oil bath at 90 °C for 6 h, and then place in a tube furnace and calcine at 600 °C in a nitrogen atmosphere for 2 h at a heating rate of 5.0 °C / min. The resulting product is Co@pHNC-600 °C;

[0091] 2. Catalytic activity test.

[0092] 2 mg of TC was weighed and dispersed in 100 mL of deionized water. Then, 10 mg of Co@pHNC-600℃ was added and stirred until homogeneous. 1 mM PMS was weighed and added to the mixture. The reaction was carried out at 20℃ and atmospheric pressure. 3 mL samples were taken at various time points, and 3 mL of methanol was added to stop the reaction. The test samples were filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The test sample solutions were detected using a UV spectrophotometer with a quartz absorption cell, following the same detection method as step 2 in Example 1. The results showed that the degradation rate of TC reached 97.5% after 20 min of reaction.

[0093] 3. Regeneration performance test:

[0094] The regeneration performance test method was the same as in Example 1. The results showed that the catalyst activity was not significantly lost during the regeneration reaction, and the degradation rate of TC decreased from 97.5% to 82.2% during the first to fifth regeneration experiments.

[0095] Example 3:

[0096] 1. Preparation of nitrogen-doped cobalt-supported carbon nanoparticles Co@pHNC-400℃ with hierarchical porous honeycomb structure.

[0097] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and stirred at 30 °C for 1 h. Then, the mixture was washed with ethanol and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0098] (2) Weigh 1 g of SiO2 nanospheres and add them to 100 mL of toluene. Purge with nitrogen for 30 min, then add 6.0 mL of γ-methacryloyloxypropyl (KH-570) dropwise using a reflux apparatus. Heat the mixture and maintain it at 90 °C for 24 h. Wash the resulting solution with toluene, collect the precipitate by centrifugation, and then dry it at 80 °C for 24 h. The resulting product is v-SiO2.

[0099] (3) Take 0.2 g v-SiO2, 0.08 g azobisisobutyronitrile (AIBN), 0.8 g polymer monomers (acrylamide and methylenebisacrylamide), and 60 mL acetonitrile and add them to a 100 mL single-necked flask. After purging with nitrogen for 30 min, shake the reaction at 50 °C for 6 h, then raise the temperature to 60 °C and continue the reaction for 24 h. Centrifuge the product, wash it three times with acetonitrile, and then dry it at 70 °C for 12 h. Obtain the product SiO2@Polymer;

[0100] (4) The SiO2@Polymer sample was placed in a tube furnace and carbonized at 600℃ in a nitrogen atmosphere for 2 hours at a heating rate of 5.0℃ / min. The resulting product was SiO2@NC;

[0101] (5) Weigh 0.5 g SiO2@NC, add 9.33 mL ethanol and 10.67 mL 40 wt% HF, and treat for 24 h. Then wash with ethanol. Obtain the product pHNC;

[0102] (6) Dissolve 0.2 g pHNC and 0.5821 g Co(NO3)2·6H2O in 80 mL of ethanol, sonicate for 30 min, then evaporate in an oil bath at 90 °C for 6 h, and then place in a tube furnace and calcine at 400 °C for 2 h in a nitrogen atmosphere at a heating rate of 5.0 °C / min. The resulting product is Co@pHNC-400 °C.

[0103] 2. Catalytic performance test:

[0104] 2 mg of TC was weighed and dispersed in 100 mL of deionized water. Then, 10 mg of Co@pHNC-400℃ was added and stirred until homogeneous. 1 mM PMS was weighed and added to the mixture. The reaction was carried out at 30℃ and atmospheric pressure. 3 mL samples were taken at various time points, and 3 mL of methanol was added to stop the reaction. The test samples were filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The test sample solutions were detected using a UV spectrophotometer with a quartz absorption cell, following the same detection method as step 2 in Example 1. The results showed that the degradation rate of TC reached 91% after 20 min of reaction.

[0105] 3. Regeneration performance test:

[0106] The regeneration performance test method was the same as in Example 1. The results showed that the catalyst activity was not significantly lost during the regeneration reaction, and the degradation rate of TC decreased from 91% to 82.6% during the first to fifth regeneration experiments.

[0107] Example 4:

[0108] 1. Preparation of nitrogen-doped cobalt-supported carbon nanoparticles Co@pHNC-700℃ with hierarchical porous honeycomb structure.

[0109] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and stirred at 30 °C for 1 h. Then, the mixture was washed with ethanol and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0110] (2) Weigh 1 g of SiO2 nanospheres and add them to 100 mL of toluene. Purge with nitrogen for 30 min, then add 6.0 mL of γ-methacryloyloxypropyl (KH-570) dropwise using a reflux apparatus. Heat the mixture and maintain it at 90 °C for 24 h. Wash the resulting solution with toluene, collect the precipitate by centrifugation, and then dry it at 80 °C for 24 h. The resulting product is v-SiO2.

[0111] (3) Take 0.2 g v-SiO2, 0.08 g azobisisobutyronitrile (AIBN), 0.8 g polymer monomers (acrylamide and methylenebisacrylamide), and 60 mL acetonitrile and add them to a 100 mL single-necked flask. After purging with nitrogen for 30 min, shake the reaction at 50 °C for 6 h, then raise the temperature to 60 °C and continue the reaction for 24 h. Centrifuge the product, wash it three times with acetonitrile, and then dry it at 70 °C for 12 h. Obtain the product SiO2@Polymer;

[0112] (4) The SiO2@Polymer sample was placed in a tube furnace and carbonized at 600℃ in a nitrogen atmosphere for 2 hours at a heating rate of 5.0℃ / min. The resulting product was SiO2@NC;

[0113] (5) Weigh 0.5 g SiO2@NC, add 9.33 mL ethanol and 10.67 mL 40 wt% HF, and treat for 24 h. Then wash with ethanol. Obtain the product pHNC;

[0114] (6) Dissolve 0.2 g pHNC and 0.5821 g Co(NO3)2·6H2O in 80 mL of ethanol, sonicate for 30 min, then evaporate in an oil bath at 90 °C for 6 h, and then place in a tube furnace and calcine at 700 °C in a nitrogen atmosphere for 2 h at a heating rate of 5.0 °C / min. The obtained product is Co@pHNC-700 °C.

[0115] 2. Catalytic performance test:

[0116] 2 mg of TC was weighed and dispersed in 100 mL of deionized water. Then, 10 mg of Co@pHNC-700℃ was added and stirred until homogeneous. 1 mM PMS was weighed and added to the mixture. The reaction was carried out at 30℃ and atmospheric pressure. 3 mL samples were taken at various time points, and 3 mL of methanol was added to stop the reaction. The test samples were filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. The test sample solutions were detected using a UV spectrophotometer with a quartz absorption cell, following the same detection method as step 2 in Example 1. The results showed that the degradation rate of TC reached 78.9% after 30 min of reaction.

[0117] 3. Regeneration performance test:

[0118] The regeneration performance test method was the same as in Example 1. The results showed that the catalyst activity was not significantly lost during the regeneration reaction, and the degradation rate of TC decreased from 78.9% to 70.1% during the first to fifth regeneration experiments.

[0119] Example 5

[0120] 1. Nitrogen-doped cobalt-supported carbon nanoparticles with a hierarchical porous honeycomb structure, Co@pHNC-500℃, were prepared using cobalt acetate tetrahydrate.

[0121] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and the mixture was stirred at 30 °C for 1 h. After the reaction was completed, the mixture was centrifuged, the solid product was washed with ethanol and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0122] (2) Weigh 1.0 g of the SiO2 nanospheres obtained in step (1) and add them to 100 mL of toluene for dispersion. Purge the system with nitrogen for 30 min to remove oxygen. Then, add 6.0 mL of γ-(methacryloyloxy)propyltrimethoxysilane KH-570 dropwise to the system using a reflux apparatus. Heat the mixture to 90 °C under continuous stirring and maintain the reaction for 24 h. After the reaction is complete, wash the product with toluene, collect the solid product by centrifugation, and dry it at 80 °C for 24 h to obtain surface-modified SiO2 nanospheres v-SiO2.

[0123] (3) Weigh 0.2g of v-SiO2 obtained in step (2), 0.08g of azobisisobutyronitrile (AIBN), and 0.8g of the polymer monomer composed of acrylamide and methylenebisacrylamide, and add them to a 100mL single-necked flask containing 60mL of acetonitrile. The resulting mixture is ultrasonically dispersed to ensure uniform dispersion of all components. Nitrogen gas is then introduced into the reaction system for 30min. The reaction system is placed in a water bath shaker and shaken at 50℃ for 6h. The temperature is then increased to 60℃, and the shaking reaction continues for 24h. After the reaction is complete, the product is centrifuged, washed three times with acetonitrile, and dried at 70℃ for 12h to obtain SiO2@Polymer.

[0124] (4) The SiO2@Polymer obtained in step (3) is placed in a tube furnace and heated to 600°C at a heating rate of 5°C / min under nitrogen atmosphere protection, and carbonized at this temperature for 2 hours. After carbonization, it is naturally cooled to room temperature under nitrogen atmosphere to obtain a black powder product SiO2@NC.

[0125] (5) Weigh 0.5g of SiO2@NC obtained in step (4) and add it to a mixed solution consisting of 9.33mL of ethanol and 10.67mL of HF with a mass concentration of 40%. Etch the material continuously with stirring at room temperature for 24h to remove the SiO2 hard template. After etching, the obtained product is centrifuged and washed repeatedly with ethanol to obtain the nitrogen-doped carbon material pHNC with a hierarchical honeycomb structure.

[0126] (6) Weigh 0.2g of pHNC obtained in step (5) and 0.4982g of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and add it to 80mL of ethanol. Sonicate for 30min to fully disperse the cobalt acetate tetrahydrate and allow it to fully contact the nitrogen-containing sites and pore structure on the surface of pHNC. Place the resulting mixture in a 90℃ oil bath for 6h to allow the solvent to gradually evaporate and the cobalt precursor to be loaded onto the pHNC framework. Then place the resulting solid product in a tube furnace and heat it to 500℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. Calcinate at this temperature for 2h and allow it to cool naturally to room temperature to obtain a nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst with a hierarchical porous honeycomb structure prepared using cobalt acetate tetrahydrate as a cobalt precursor, denoted as Co@pHNC-500℃.

[0127] In this embodiment, cobalt acetate tetrahydrate is used instead of cobalt nitrate hexahydrate as the cobalt precursor. Cobalt-supported catalytic materials are prepared while keeping the basic process routes of hard template construction, surface functionalization, nitrogen-containing polymer coating, carbonization, template etching, and secondary loading heat treatment unchanged. This is used to illustrate the applicability of the preparation method of this application when different soluble cobalt salts are used as cobalt sources.

[0128] 2. Catalytic activity test

[0129] Weigh 2 mg of tetracycline (TC) and add it to 100 mL of deionized water. Stir thoroughly to disperse the TC evenly, thus preparing an aqueous TC solution. Add 10 mg of the Co@pHNC-500℃ catalyst prepared in this example to the TC aqueous solution and stir continuously to disperse the catalyst evenly in the solution.

[0130] PMS was then added to the system to make the initial concentration of PMS in the reaction system 1 mmol / L, and the catalytic degradation reaction was carried out at 20 °C and atmospheric pressure.

[0131] During the reaction, 3 mL of reaction solution was taken at predetermined time intervals. Immediately after each sampling, 3 mL of methanol was added to quench the active species and terminate the subsequent oxidation reaction. The resulting mixture was filtered through a 0.22 μm PTFE membrane, and the filtrate was used for TC concentration detection.

[0132] TC concentration can be determined by ultraviolet spectrophotometry using a quartz absorption cell and measuring absorbance within the characteristic absorption wavelength range of TC. The TC concentration at different reaction times can be calculated based on a pre-established TC standard curve.

[0133] 3. Regeneration performance test

[0134] After the catalytic reaction was completed, the Co@pHNC-500℃ catalyst was separated from the reaction system by centrifugation. The recovered catalyst was washed with deionized water and ethanol to remove residual TC, degradation intermediates and inorganic salts adsorbed on the catalyst surface, and then the catalyst was dried.

[0135] The recovered catalyst was then reintroduced into the TC / PMS reaction system under the same catalytic activity testing conditions as described above for the next catalytic cycle. By repeating the above catalytic, centrifugal, washing, and drying steps, the catalyst can be recycled multiple times to evaluate its cycle stability.

[0136] If necessary, ICP-OES or ICP-MS can be used to detect the Co content in the liquid phase after the cyclic reaction to evaluate the cobalt species loading stability of the catalyst obtained when cobalt acetate tetrahydrate is used as a cobalt precursor.

[0137] Example 6:

[0138] 1. Nitrogen-doped cobalt-supported carbon nanoparticles (Co@pHNC-500℃) with a hierarchical porous honeycomb structure were prepared using composite nitrogen-containing polymer monomers.

[0139] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and the mixture was stirred continuously at 30 °C for 1 h. After the reaction was completed, the product was centrifuged, washed with ethanol, and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0140] (2) Weigh 1.0 g of the SiO2 nanospheres obtained in step (1) and add them to 100 mL of toluene. After dispersing them thoroughly, purge the system with nitrogen gas for 30 min. Then add 6.0 mL of KH-570 to the reaction system and reflux at 90 °C for 24 h under continuous stirring. After the reaction is complete, wash the product with toluene, collect the solid by centrifugation, and dry it at 80 °C for 24 h to obtain v-SiO2.

[0141] (3) Weigh 0.2g of v-SiO2 obtained in step (2) and 0.08g of azobisisobutyronitrile (AIBN) and add them to 60mL of acetonitrile. Add 0.4g of acrylamide, 0.3g of N-vinylpyrrolidone and 0.1g of methylenebisacrylamide, where acrylamide and N-vinylpyrrolidone are the main nitrogen-containing polymer monomers and methylenebisacrylamide is used to participate in the formation of cross-linked polymerization structure.

[0142] The resulting mixture was ultrasonically dispersed to ensure uniform dispersion of v-SiO2, initiator, and monomers in acetonitrile, followed by purging with nitrogen for 30 min. The mixture was then placed in a water bath shaker and reacted at 50 °C for 6 h, followed by increasing the temperature to 60 °C and continuing the reaction for 24 h to allow the nitrogen-containing polymer to form a coating layer on the v-SiO2 surface. After the reaction, the solid product was collected by centrifugation, washed three times with acetonitrile, and dried at 70 °C for 12 h to obtain SiO2@Polymer.

[0143] (4) Place the SiO2@Polymer obtained in step (3) in a tube furnace and heat it to 600°C at a heating rate of 5°C / min under nitrogen atmosphere protection, and carbonize it at 600°C for 2 hours. After carbonization, allow it to cool naturally to obtain SiO2@NC.

[0144] (5) Weigh 0.5g of SiO2@NC obtained in step (4), add 9.33mL of ethanol and 10.67mL of HF with a mass concentration of 40%, and etch at room temperature for 24h. During the etching process, the SiO2 hard template is gradually removed. After the etching is completed, the obtained solid is washed with ethanol and centrifuged to obtain the nitrogen-rich doped carbon material pHNC with a multi-level porous honeycomb structure.

[0145] (6) Weigh 0.2g of pHNC obtained in step (5) and 0.5821g of cobalt nitrate hexahydrate Co(NO3)2·6H2O and add it to 80mL of ethanol. Sonicate for 30min to make cobalt nitrate hexahydrate uniformly dispersed and loaded on the surface and pore structure of pHNC.

[0146] The mixture was then treated in a 90°C oil bath for 6 hours to allow the ethanol to gradually evaporate. The resulting solid was placed in a tube furnace and heated to 500°C at a rate of 5°C / min under a nitrogen atmosphere. It was then calcined at this temperature for 2 hours and allowed to cool naturally to room temperature. This yielded a hierarchical porous honeycomb-like nitrogen-doped carbon-supported cobalt nanoparticle catalyst with a nitrogen-doped carbon framework constructed from composite nitrogen-containing polymer monomers, denoted as Co@pHNC-500°C.

[0147] This embodiment changes the composition of nitrogen-containing polymer monomers, allowing nitrogen-containing polymer monomers with different structures to participate in the polymerization and subsequent carbonization process on the SiO2 template surface. This illustrates that the formation of a nitrogen-containing carbon skeleton is not limited to a single nitrogen-containing polymer monomer system, and provides an implementable technical solution for adjusting different types of nitrogen-containing sites in the carbon skeleton.

[0148] 2. Material Characterization

[0149] The obtained Co@pHNC-500℃ catalyst can be observed for its overall morphology and honeycomb porous structure using scanning electron microscopy, and further observed for its internal hollow structure and the distribution of cobalt-containing active components using transmission electron microscopy.

[0150] The specific surface area, pore volume, and pore size distribution of the obtained material were characterized by N2 adsorption-desorption test to evaluate the characteristics of the pore structure formed after carbonization of the composite nitrogen-containing polymer monomer.

[0151] X-ray diffraction was used to analyze the crystalline phases in the material, and Raman spectroscopy was used to analyze the defect degree and graphitization degree of the obtained carbon framework. X-ray photoelectron spectroscopy was used to analyze the chemical state of C, N, O, and Co elements on the material surface, especially for characterizing different nitrogen-containing chemical states and Co-N. x Coordination structure.

[0152] The spatial distribution of C, N, O and Co elements in the obtained catalyst can be further analyzed by using high-angle annular dark-field scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy.

[0153] 3. Catalytic activity test

[0154] Weigh 2 mg TC and disperse it in 100 mL of deionized water. Add 10 mg of the Co@pHNC-500℃ catalyst prepared in this example to the water. After stirring and dispersing thoroughly, add PMS to make the initial concentration of PMS 1 mmol / L. Carry out the catalytic degradation reaction at 20℃ and normal pressure.

[0155] At preset time intervals, 3 mL of reaction solution was taken, and an equal volume of methanol was added immediately after each sampling for quenching. The resulting samples were filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane, and the changes in TC concentration at different reaction times were detected by ultraviolet spectrophotometry.

[0156] The C / C0 or TC degradation rate can also be calculated based on the TC concentration measured at different time points, and used to evaluate the performance of catalysts prepared using composite nitrogen-containing polymer monomers in the PMS-activated degradation of TC.

[0157] 4. Regeneration performance test

[0158] After the catalytic reaction was completed, the obtained Co@pHNC-500℃ catalyst was recovered by centrifugation, washed with deionized water and ethanol respectively, and dried before being put back into the TC / PMS reaction system under the same conditions.

[0159] The recycling performance of catalysts obtained from composite nitrogen-containing polymer monomers can be evaluated by repeatedly performing catalytic reactions, catalyst recovery, washing, and refeeding.

[0160] Furthermore, the catalyst can be characterized using XPS, XRD, or electron microscopy before and after the cyclic reaction to evaluate the chemical state of the cobalt-containing active components and the retention of the honeycomb hierarchical porous structure during recycling. At the same time, the Co content of the liquid phase after the reaction can be detected to evaluate the catalyst's resistance to leaching.

[0161] Example 7:

[0162] 1. Preparation of nitrogen-doped cobalt-supported carbon nanoparticles (Co@pHNC-500℃) with hierarchical porous honeycomb structure under low cobalt precursor addition conditions.

[0163] (1) 6.0 mL of tetraethyl silicate was added dropwise to a 200 mL flask containing a mixed solution of 3.14 mL NH3·H2O, 10 mL deionized water and 90 mL ethanol, and the mixture was stirred at 30 °C for 1 h. After the reaction was completed, the solid was collected by centrifugation, washed with ethanol, and dried at 80 °C for 24 h to obtain SiO2 nanospheres.

[0164] (2) Weigh 1.0 g of SiO2 nanospheres and add them to 100 mL of toluene. After purging with nitrogen for 30 min, add 6.0 mL of KH-570. Reflux the reaction at 90 °C for 24 h. After the reaction is complete, wash with toluene, collect the solid by centrifugation, and dry at 80 °C for 24 h to obtain v-SiO2.

[0165] (3) Weigh 0.2 g v-SiO2, 0.08 g azobisisobutyronitrile (AIBN), 0.8 g of the polymer monomer composed of acrylamide and methylenebisacrylamide, and 60 mL of acetonitrile into a 100 mL single-necked flask. Disperse the mixture ultrasonically, then purge with nitrogen for 30 min. Place the resulting reaction system in a water bath shaker and react at 50 °C for 6 h. Then raise the temperature to 60 °C and continue the reaction for 24 h. After the reaction is complete, centrifuge to separate the product, wash three times with acetonitrile, and dry at 70 °C for 12 h to obtain SiO2@Polymer.

[0166] (4) Place the SiO2@Polymer obtained in step (3) in a tube furnace and heat it to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere, and hold it at that temperature for 2 hours to carbonize the polymer coating layer and form a nitrogen-doped carbon skeleton. After calcination, allow it to cool naturally to obtain SiO2@NC.

[0167] (5) Weigh 0.5g of SiO2@NC obtained in step (4), add 9.33mL of ethanol and 10.67mL of HF with a mass concentration of 40%, and stir continuously at room temperature for 24h to etch and remove the SiO2 hard template. After the reaction is complete, wash with ethanol and collect the solid by centrifugation to obtain the nitrogen-doped carbon material pHNC with a hierarchical porous honeycomb structure.

[0168] (6) Weigh 0.2g of pHNC obtained in step (5) and 0.4000g of cobalt nitrate hexahydrate Co(NO3)2·6H2O and add it to 80mL of ethanol. Sonicate for 30min to fully disperse the cobalt precursor and enter the pore structure of pHNC, while making full contact with the nitrogen-containing sites in the nitrogen-doped carbon framework.

[0169] The mixture was then treated in a 90°C oil bath for 6 hours to allow ethanol to gradually evaporate and promote the loading of the cobalt precursor onto the pHNC framework. The resulting solid was placed in a tube furnace and heated to 500°C at a rate of 5°C / min under a nitrogen atmosphere. It was then calcined at 500°C for 2 hours and allowed to cool naturally to obtain a hierarchical porous honeycomb-like nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst prepared under conditions of low cobalt precursor addition, denoted as Co@pHNC-500°C.

[0170] This embodiment reduces the amount of cobalt precursor added compared to the preparation condition using 0.5821gCo(NO3)2·6H2O. This is to demonstrate that, under the condition of reducing the amount of cobalt source added, the corresponding cobalt-supported catalytic materials can still be prepared according to the process route of hard template replication, nitrogen-containing skeleton construction, and post-cobalt loading. It is also used to study the effect of the amount of cobalt precursor added on the dispersion state, utilization efficiency, and stability of the active components.

[0171] 2. Material Characterization

[0172] The honeycomb porous structure and distribution of cobalt-containing active components of the obtained catalyst were observed using scanning electron microscopy and transmission electron microscopy.

[0173] The spatial distribution of Co, N, C and O elements in the material was observed using high-angle annular dark-field scanning transmission electron microscopy and EDS elemental surface scanning, and was used to evaluate the dispersion of cobalt-containing active components after reducing the amount of cobalt precursor added.

[0174] X-ray photoelectron spectroscopy was used to analyze different nitrogen species and Co-N in the obtained material. x Coordination state was analyzed; the actual cobalt content in the obtained catalyst was determined by ICP-OES or ICP-MS to compare the cobalt loading level under different cobalt precursor addition conditions.

[0175] Meanwhile, the specific surface area, pore volume, and pore size distribution of the N2 adsorption-desorption test material can be used to evaluate the effect of different cobalt loading on the hierarchical porous honeycomb framework structure.

[0176] 3. Catalytic activity test

[0177] Weigh 2 mg TC and add it to 100 mL of deionized water for dispersion. Add 10 mg of the low cobalt supported Co@pHNC-500℃ catalyst obtained in this example to the TC solution and stir continuously to make the catalyst evenly dispersed.

[0178] PMS was then added to bring the initial concentration of PMS in the reaction system to 1 mmol / L, and the catalytic reaction was carried out at 20 °C and atmospheric pressure.

[0179] 3 mL of the reaction solution was taken at predetermined time intervals, and 3 mL of methanol was added immediately after each sampling for quenching. The resulting liquid was filtered through a 0.22 μm PTFE membrane, and the TC concentration was measured using a UV spectrophotometer.

[0180] The TC degradation rate can be further calculated based on the TC concentration at each time point, and the reaction kinetics can be analyzed based on the change of TC concentration over time during the reaction process, which can be used to compare the PMS activation capacity of the catalysts obtained under different amounts of cobalt precursor.

[0181] 4. Regeneration performance and cobalt leaching test

[0182] After the catalytic reaction was completed, the obtained low cobalt supported Co@pHNC-500℃ catalyst was separated from the reaction solution by centrifugation, washed with deionized water and ethanol, dried and then reintroduced into the TC / PMS catalytic system under the same conditions.

[0183] The above catalytic reaction and catalyst recovery steps were repeated to evaluate the recycling stability of the low cobalt-supported catalyst.

[0184] After each reaction cycle, a certain amount of the reaction solution is taken and its Co content is detected by ICP-OES or ICP-MS. Combined with the XPS, XRD, SEM, and TEM characterization results of the catalyst before and after each cycle, the stability of the cobalt-containing active component in the catalyst, the retention of the hierarchical porous honeycomb framework, and the leaching of cobalt species are evaluated. By comparing this example with catalysts prepared under conditions with higher cobalt precursor addition, the anchoring and dispersing effects of the nitrogen-doped carbon framework on the cobalt active component, as well as the influence of the cobalt precursor addition amount on the catalyst structure and PMS activation performance, can be further investigated.

[0185] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst, characterized in that, Includes the following steps: S1. Using silica nanospheres as a hard template, the silica nanospheres are dispersed in an organic medium. Under a protective atmosphere, the silica nanospheres are surface modified with an organosilane surface modifier to form an organic functional layer on the surface of the silica nanospheres that can interact with the subsequent polymerization system, thereby obtaining modified silica nanospheres v-SiO2. S2. The modified silica nanospheres v-SiO2 are dispersed in a polymerization medium. Under the action of a free radical polymerization initiator, nitrogen-containing polymeric monomers are polymerized on the surface of the modified silica nanospheres in a protective atmosphere, forming a nitrogen-containing polymer coating layer on the surface of the modified silica nanospheres, thus obtaining a silica / nitrogen-containing polymer composite material SiO2@Polymer. S3. The SiO2@Polymer is subjected to a first heat treatment under a protective atmosphere to carbonize the nitrogen-containing polymer coating layer to form a nitrogen-doped carbon skeleton, thereby obtaining the silicon dioxide / nitrogen-doped carbon composite material SiO2@NC. S4. Chemically etch the SiO2@NC using an etching solution to at least partially remove the silicon dioxide nanosphere hard template, so that the nitrogen-doped carbon framework retains the pores formed by the silicon dioxide nanosphere hard template, and obtains a nitrogen-doped carbon material pHNC with a honeycomb hierarchical porous structure. S5. The pHNC and cobalt precursor are mixed and dispersed in a solvent, so that the cobalt precursor is loaded onto the pHNC. After removing the solvent, a second heat treatment is performed to disperse the cobalt active component at the nanoscale on the surface and / or channels of the nitrogen-doped carbon framework, thereby obtaining a hierarchical porous honeycomb nitrogen-doped carbon-supported cobalt nanoparticle catalyst Co@pHNC.

2. The method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst according to claim 1, characterized in that, The silica nanospheres were prepared by the following method: Ammonia, deionized water, ethanol and silicon-containing precursor were mixed and stirred to react. After the reaction was completed, solid-liquid separation and drying were performed to obtain silica nanospheres (SiO2). The ratio of ammonia, deionized water, ethanol to silicon-containing precursor is 2-4 mL: 5-15 mL: 80-100 mL: 4-8 mL; The silicon-containing precursor is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, polysiloxane, and sodium silicate; The reaction temperature is 20–40°C, and the reaction time is 1–3 h; the drying is vacuum drying, with a vacuum drying temperature of 60–80°C and a vacuum drying time of 12–24 h.

3. The method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst according to claim 2, characterized in that, In step S1, the ratio of the amount of silica nanospheres, the organic medium, and the organosilane surface modifier is 1.0–3.0 g: 100–300 mL: 4–8 mL. The organic medium is toluene; The organosilane surface modifier is selected from one or more of γ-(methacryloyloxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and vinyltriacetoxysilane. The protective atmosphere is a nitrogen atmosphere. After the nitrogen atmosphere is introduced for 20 to 50 minutes, the surface modification reaction is carried out. The temperature of the surface modification reaction is 80 to 100°C, and the reaction time is 20 to 28 hours. After the reaction was completed, the sample was washed with toluene and collected by centrifugation. It was then vacuum dried at 60–80 °C for 12–24 h to obtain the modified silica nanospheres v-SiO2.

4. The method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst according to claim 3, characterized in that, In step S2, the ratio of the modified silica nanospheres v-SiO2, the polymerization medium, the free radical polymerization initiator, and the nitrogen-containing polymerization monomer is 0.1–0.4 g: 40–80 mL: 60–100 mg: 0.6–1.0 g. The polymerization medium is acetonitrile; The free radical polymerization initiator is an azo-based free radical polymerization initiator, selected from one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, azobiscyclohexylformonitrile, and dimethyl azobisisobutyrate; The nitrogen-containing polymeric monomer is selected from one or more of acrylamide, methylenebisacrylamide, N-isopropylacrylamide, N-vinylpyrrolidone, acrylonitrile, and dimethylaminoethyl methacrylate.

5. The method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst according to claim 4, characterized in that, In step S2, the modified silica nanospheres v-SiO2 are dispersed in acetonitrile, the free radical polymerization initiator is added and ultrasonically dispersed, the nitrogen-containing polymerization monomer is added and nitrogen gas is introduced for 20-50 minutes. The first stage polymerization reaction was then carried out at 40–60°C and 100–120 rpm for 4–8 hours, and then the temperature was raised to 50–70°C and the second stage polymerization reaction was carried out at 100–120 rpm for 20–28 hours. After the reaction was completed, the solid was separated by centrifugation and washed with acetonitrile. Then, it was vacuum dried at 60-80℃ for 12-24 h to obtain the SiO2@Polymer.

6. The method for preparing a multi-level porous honeycomb Co-nanoparticle catalyst doped with nitrogen-rich carbon according to claim 5, wherein the step of preparing the Co-nanoparticle catalyst doped with nitrogen-rich carbon is performed by a method comprising the steps of: (a) preparing a Co-nanoparticle catalyst; (b) preparing a nitrogen-rich carbon; and (c) mixing the Co-nanoparticle catalyst and the nitrogen-rich carbon. In step S3, the SiO2@Polymer is placed in a tube furnace and subjected to the first heat treatment under a nitrogen atmosphere. The temperature of the first heat treatment is 400-900℃, the heating rate is 5℃ / min, and the holding time is 1-3h; after the heat treatment is completed, it is naturally cooled under a protective atmosphere to obtain SiO2@NC.

7. The method for preparing a multi-level porous honeycomb N-doped carbon supported cobalt nanoparticle catalyst according to claim 6, characterized in that, In step S4, the SiO2@NC is dispersed in an etching system composed of ethanol and etching solution and then stirred and etched. The ratio of SiO2@NC, ethanol, and etching solution is 0.2–0.6 g: 8–10 mL: 10–12 mL. The etching solution is 40wt% hydrofluoric acid (HF), and the etching time is 20-28h; After etching, solid-liquid separation was performed and the material was washed with ethanol to obtain a nitrogen-doped carbon material pHNC with a honeycomb hierarchical porous structure.

8. The method for preparing the hierarchical porous honeycomb nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst as described in claim 7, characterized in that, In S5, the cobalt precursor is a soluble cobalt salt, which is selected from one or more of cobalt nitrate hexahydrate Co(NO3)2·6H2O, cobalt chloride hexahydrate CoCl2·6H2O, cobalt sulfate heptahydrate CoSO4·7H2O, and cobalt acetate tetrahydrate Co(CH3COO)2·4H2O. The ratio of pHNC, the cobalt precursor, and the solvent is 0.1–0.3 g: 0.4–0.6 g: 60–100 mL, and the solvent is ethanol.

9. The method for preparing the hierarchical porous honeycomb nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst as described in claim 8, characterized in that, In step S5, the pHNC and the cobalt precursor are added to ethanol and ultrasonically dispersed to ensure that the cobalt precursor and the pHNC are in full contact. Then, an oil bath treatment is performed at 80-100°C for 5-7 hours to remove at least part of the solvent. After washing the obtained pHNC of the supported cobalt precursor, it was placed in a tube furnace for the second heat treatment under a nitrogen atmosphere. The second heat treatment is performed at a temperature of 300–800°C, with a heating rate of 5°C / min and a holding time of 1–3 h. After the heat treatment, the material is allowed to cool naturally to obtain the multi-level porous honeycomb nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst.

10. The method for preparing the hierarchical porous honeycomb nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst as described in claim 9, characterized in that, The silica nanospheres maintain a hard template structure during the first heat treatment in S3 and are removed in S4, so that a honeycomb-like cavity corresponding to the silica nanosphere template is formed in the nitrogen-doped carbon framework; the honeycomb-like cavity and the pores in the nitrogen-doped carbon framework together form a multi-level porous mass transfer structure. The cobalt precursor is loaded onto the pHNC after the silica nanosphere hard template is removed, and is then subjected to the second heat treatment to form a cobalt-containing nano-active component dispersed on the surface and / or in the pores of the nitrogen-doped carbon framework. The resulting catalyst is denoted as Co@pHNC-X℃, where X represents the temperature of the second heat treatment.

11. The application of a hierarchical porous honeycomb-shaped nitrogen-rich doped carbon-supported cobalt nanoparticle catalyst in the degradation of tetracycline pollutants by activated persulfate, characterized in that, The catalyst is a hierarchical porous honeycomb nitrogen-doped carbon cobalt-supported nanoparticle catalyst prepared by the preparation method according to any one of claims 1 to 10; the catalyst is added to water containing tetracycline pollutants and dispersed, and then persulfate is added, so that the persulfate is activated under the synergistic effect of the cobalt-containing active sites of the catalyst and the nitrogen-doped carbon framework, so as to oxidatively degrade the tetracycline pollutants.

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