A cerium oxide-based catalyst with Ni-Ov dual active sites, a preparation method and application thereof

Abstract

The application relates to the technical field of organic pollutant treatment, in particular to a Ni-Ov double active site cerium oxide-based catalyst and a preparation method and application thereof. The cerium oxide-based catalyst comprises a carrier and an active component loaded on the carrier, the carrier is composed of a cerium oxide carrier and an oxygen vacancy structure on the carrier, and the active component is a nickel monatomic atom. The oxygen vacancy structure can anchor the active center of the nickel monatomic atom, so that the oxygen vacancy structure and the nickel monatomic atom form a double active site. The preparation method comprises the following steps: preparing a metal precursor by combining coprecipitation with a hydrothermal method through cerium salt and nickel salt, washing and drying, and calcining under a reducing atmosphere to obtain a catalyst in which nickel monatomic atoms are stably anchored on the oxygen vacancies of cerium oxide. The cerium oxide-based catalyst prepared by the application can efficiently activate ozone, a stable 'oxygen vacancy-nickel monatomic atom' double active center is constructed, and the catalytic oxidation efficiency and long-term operation stability for various refractory organic pollutants are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of organic pollutant treatment technology, specifically to the invention of a cerium oxide-based catalyst with Ni-Ov dual active sites, its preparation method, and its application. Background Technology

[0002] Heterogeneous ozone catalytic oxidation technology is an important method in the field of advanced water treatment, but it still faces key challenges. Firstly, for electron-deficient pollutants, the oxidation pathway relying on hydroxyl radicals (·OH) of traditional catalysts has limited efficiency, and ·OH is readily converted by common anions in water (such as Cl-). - , (e.g., quenching) leads to a sharp drop in oxidation selectivity and efficiency in complex water conditions. Secondly, the active metal components in traditional catalysts are prone to aggregation and leaching deactivation, resulting in low metal atom utilization. Furthermore, the ozone activation sites and pollutant oxidation sites are often separated, leading to insufficient synergistic effect.

[0003] In recent years, single-atom catalysts and oxygen vacancy engineering have provided new approaches to improving ozone catalytic efficiency. Single-atom catalysts can maximize metal utilization, while oxygen vacancies can modulate the electronic structure and adsorption behavior of the support surface. However, existing technologies still have significant limitations: on the one hand, single-atom metals are prone to migration and aggregation during the reaction, exhibiting poor stability; on the other hand, the concentration and structure of oxygen vacancies are difficult to control precisely, and the activation pathway of a single oxygen vacancy or single-atom site for ozone is limited, leaving room for improvement in catalytic efficiency. Furthermore, in practical water treatment environments, catalyst active sites are easily covered or poisoned by complex matrices in the water, affecting their long-term operation.

[0004] Therefore, developing a catalyst that combines high intrinsic activity, high metal dispersion stability, and strong ozone activation capability is crucial. This invention aims to address these issues by constructing a cerium oxide-based catalyst. Utilizing controllable oxygen vacancies formed on a cerium oxide support, nickel single atoms are strongly anchored, forming a stable "oxygen vacancy-nickel single atom" dual active center. This structure not only prevents nickel atom aggregation through strong interactions, improving catalyst stability, but also enhances the adsorption, activation, and conversion efficiency of ozone through the synergistic effect of the dual active sites, thereby achieving efficient and stable catalytic degradation of various organic pollutants. Summary of the Invention

[0005] To achieve the above effects, the present invention provides a cerium oxide-based catalyst with Ni-Ov dual active sites. This catalyst comprises a support and an active component loaded on the support. The support consists of a cerium oxide support and oxygen vacancy structures thereon. The active component is a nickel single atom. The oxygen vacancy structures can anchor the active centers of the nickel single atoms, thus forming dual active sites with the nickel single atoms. The mass content of nickel single atoms in the above Ni-Ov dual active site cerium oxide-based catalyst is 0.5–2 wt%.

[0006] As another aspect of the present invention, a method for preparing the above-mentioned Ni-Ov dual-active-site cerium oxide-based catalyst is also provided, the details of which are as follows: S1. Preparation of metal precursors: Will and Dissolve in deionized water, add NaOH solution dropwise while maintaining stirring, precipitate out, and then hydrothermally treat at 100~130℃ for 20~24 h to obtain the metal precursor after the reaction is complete; Let n be the multiplier and ,but The amount added is [10n, 20n] mg. The amount of [1.75n, 3.5n] g added, the amount of deionized water added, the amount of [10n, 12n] mL added, the concentration of NaOH solution is 2~5 mol / L, and the amount of [70n, 80n] mL added; Note: This step employs a hydrothermal co-precipitation method to uniformly mix and precipitate cerium and nickel at the molecular level. The hydrothermal process promotes crystallization and structure orientation, forming a uniformly sized and stable composite metal hydroxide precursor, laying the structural foundation for the subsequent formation of highly dispersed active sites. S2, Precursor drying: First, wash the metal precursor obtained in S1 until the washing solution is neutral. Then, dry the washed metal precursor at 60~130℃ for 6~12 h and then sieve it for later use. Note: Washing aims to remove residual sodium ions and nitrate ions, and prevent them from affecting the purity and structure of the catalyst in subsequent high-temperature treatment; drying and sieving are to obtain dry, loose and uniformly sized solid powder to ensure uniform heating in subsequent calcination steps and improve batch stability. S3, Calcination activation: Under a reducing atmosphere, the precursor treated with S2 was calcined at 300–600 °C for 2–6 h, and after natural cooling to room temperature, it was ground and sieved to obtain a cerium oxide-based catalyst with Ni-Ov dual active sites. catalyst.

[0007] Note: Calcination transforms amorphous precursors into crystalline forms. Under a reducing atmosphere, Oxygen in the surface and bulk phases is partially removed, creating abundant oxygen vacancies in situ; simultaneously, nickel is reduced and, with the anchoring effect of these oxygen vacancies, is highly dispersed in single-atom form. This allows for the construction of a dual active center with oxygen vacancy and nickel single atom cooperation.

[0008] Furthermore, the reducing atmosphere in S3 is or and The mixture of gases.

[0009] As another aspect of the present invention, a method for further modification of the above-mentioned Ni-Ov dual-active-site cerium oxide-based catalyst is also provided, namely, by treating the S3 with a coating-template sacrificial method. The catalyst can be further used to prepare cerium oxide-based catalysts with Ni-Ov dual active sites in a core-cavity-shell structure.

[0010] Furthermore, the S3 is processed using the wrap-template sacrifice method. The steps for using a catalyst are as follows: S1. Preparation of metal precursors: Will and Dissolve in deionized water, add NaOH solution dropwise while maintaining stirring, precipitate out, and then hydrothermally treat at 100~130℃ for 20~24 h to obtain the metal precursor after the reaction is complete; Let n be the multiplier and ,but The amount added is [10n, 20n] mg. The amount of [1.75n, 3.5n] g added, the amount of deionized water added, the amount of [10n, 12n] mL added, and the concentration of NaOH solution is 2~5 mol / L with an added amount of [7n, 10n] L; S2, Precursor drying: First, wash the metal precursor obtained in S1 until the washing solution is neutral. Then, dry the washed metal precursor at 60~130℃ for 6~12 h and then sieve it for later use. S3, Calcination activation: Under a reducing atmosphere, the precursor treated with S2 was calcined at 300–600 °C for 2–6 h, and after natural cooling to room temperature, it was ground and sieved to obtain a cerium oxide-based catalyst with oxygen-rich vacancy-anchored nickel single-atom sites, i.e. catalyst; S4 Catalyst surface amination: In S3 The catalyst was added to anhydrous ethanol and ultrasonically dispersed for 30–40 min to obtain suspension A. Suspension A was then introduced into a reflux condenser, and APTES ((3-aminopropyl)triethoxysilane) was added dropwise under continuous stirring. The mixture was heated to 70–75 °C and refluxed for 4–6 h under a nitrogen atmosphere. After the reaction was completed, the mixture was naturally cooled to room temperature, and the product was washed by centrifugation with anhydrous ethanol and dried under vacuum at 55–60 °C. ; Let n be the multiplier and ,but The amount of [1n, 2n] g added, the amount of anhydrous ethanol added, the amount of [150n, 200n] mL added, and the amount of APTES added, the amount of [0.5n, 2n] mL added; Note: This step involves the hydrolysis and condensation reaction of the silane coupling agent (APTES) to achieve the desired effect. Amino (-NH2) functional groups are grafted onto the particle surface; amylation modification improves the dispersibility of the core particles in polar solvents and provides abundant chemical binding sites for subsequent carbon layer coating. S5, Sacrificial Layer Coverage: Dissolve glucose in deionized water and stir until homogeneous, then add it to the solution prepared in S4. The mixture was ultrasonically dispersed for 30-40 min, then transferred to a reaction vessel and reacted at 160-180℃ for 5-6 h. After naturally cooling to room temperature, the product was washed clean with deionized water and ethanol alternately, and finally dried at 55-60℃ to constant weight. The product was recorded as [product name missing]. ; Let n be the multiplier and ,but The amount of [0.5n, 1n] g added, and the amount of deionized water added, is [40n, 50n] mL. The amount added is [0.5n, 1n] g; Note: This step utilizes the glucose hydrothermal carbonization method to coat the surface of the aminated core with a uniform amorphous carbon layer; this carbon layer serves as a sacrificial template, and its thickness directly determines the cavity size in the final core-cavity-shell structure; the advantage of this method is that the thickness of the carbon layer can be precisely controlled by the glucose concentration and hydrothermal time, and the coating is gentle and uniform. S6, outer shell coating: prepared by the sol-gel method in S5. Externally coated mesoporous structure The outer shell is thus obtained to have a three-layer structure. ; S7. Preparation of core-cavity-shell structure: In S6 The catalyst was placed in a tube furnace and calcined at a stepped temperature. After calcination, it was naturally cooled to room temperature to obtain a cerium oxide-based catalyst with a core-cavity-shell structure and two active sites, denoted as [catalyst name missing]. catalyst.

[0011] Furthermore, the steps for covering the outer shell in S6 are as follows: S6-1. Preparation of template agent solution: Dissolve CTAB (hexadecyltrimethylammonium bromide) in a mixed solution of anhydrous ethanol and deionized water, add 28 wt% ammonia while stirring, and then stir at a constant temperature of 35~40℃ for 30~40 min to obtain solution A; Let n be the multiplier and ,but The amount of [0.2n, 0.25n] g added, and the amount of anhydrous ethanol added, is [70n, 80n] mL. The amount of 28 wt% ammonia added is [0.5n, 2n] mL; Explanation: CTAB acts as a structure directing agent (template) to form micelles in solution; ammonia provides an alkaline environment to catalyze the subsequent hydrolysis of the silicon source; this step constructs the templated reaction system necessary for the formation of ordered mesoporous structures. S6-2, Coating reaction: First, the coating reaction prepared in S5... Disperse in anhydrous ethanol and sonicate for 20-30 min, then mix with solution A and stir; then keep the system at a constant temperature of 35°C and add dropwise a mixed solution of TEOS (tetraethyl orthosilicate) and anhydrous ethanol, and continue stirring for 24 h; Let n be the multiplier and ,but The amount of [0.3n, 0.5n] g added, and the amount of anhydrous ethanol added, is [20n, 30n] mL; Note: Under alkaline conditions, TEOS hydrolyzes and condenses, and its products, using CTAB micelles as templates, [follow this process]. Directional deposition and growth on particle surfaces to form amorphous particles with mesoporous structures shell; S6-3, Post-processing: Centrifuge and collect the reaction product from S6-2, wash thoroughly with anhydrous ethanol, and then dry at 60°C to constant weight to obtain a product with a three-layer structure, denoted as... .

[0012] Explanation: Washing removes physically adsorbed reactants, and drying yields a structurally stable precursor powder. At this point, the material is a "core ( ) - Sacrificial intermediate layer (C) - Shell ( () "Three-layer structure.

[0013] Furthermore, the atmosphere in the S7 tube furnace is air, with an air flow rate of 50~60 sccm; the temperature gradient is as follows: first, the temperature is increased from room temperature to 340~350℃ at a rate of 1~3℃ / min, and held for 1.5~2 h; then, the temperature is increased to 540~550℃ at a rate of 2~4℃ / min, and held for 3.5~4 h.

[0014] Note: In air, the lower temperature range (340~350℃) mainly removes the CTAB template and forms mesoporous channels; the higher temperature range (540~550℃) completely oxidizes and removes the intermediate carbon sacrificial layer, thereby creating a cavity between the core and the shell.

[0015] As another aspect of the present invention, the above-described design The catalyst has an overall particle size range of 81~96 nm, with a core portion of " The particle size is 45~50 nm, and the cavity part is... The thickness of the "mesoporous shell" is 10~13nm. The thickness of the material is 8~10 nm, and the mesopore size is 2~4 nm.

[0016] Note: The above size system is the result of co-design optimization: the 45~50 nm core ensures a high active specific surface area; the 10~13 nm cavity provides a confined reaction space; the 8~10 nm thick shell with 2~4 nm mesopores ensures mechanical strength while enabling the free passage of small molecule pollutants (such as sulfamethoxazole) and the effective sieving of large molecule interfering substances (such as humic acid), ultimately making the catalyst have both high activity and high selectivity.

[0017] As another aspect of the present invention, the present invention is designed catalyst and Catalysts can be used in water systems containing organic pollutants and can degrade organic pollutants by introducing ozone.

[0018] Note: Both catalysts can efficiently catalyze the decomposition of ozone to produce highly reactive oxygen species (·OH), which then oxidize and degrade pollutants. Among them, With its unique core-cavity-shell structure, the catalyst exhibits superior selectivity, anti-interference, and stability in complex water bodies.

[0019] Compared with existing cerium oxide-based catalysts, the advantages of this invention are: (1) The efficiency and stability of catalysts: This invention constructs an oxygen vacancy structure on a cerium oxide support and utilizes these oxygen vacancies to strongly anchor nickel single atoms, forming a dual active center of "oxygen vacancy-nickel single atom". This structure not only greatly improves the dispersion and stability of nickel atoms, effectively preventing the aggregation and loss of active components, but also significantly enhances the adsorption and activation efficiency of ozone on the catalyst surface, increasing the conversion rate of ozone to highly reactive oxygen species (such as ·OH). Experiments show that this catalyst possesses broad-spectrum and highly efficient removal capabilities for various recalcitrant organic pollutants with different electronic structures (such as SMX, p-NBA, etc.), and maintains excellent catalytic stability during multiple cycles and continuous flow operation, laying a solid foundation for practical applications.

[0020] (2) Catalyst performance improvement: Further design of the present invention The catalyst, while inheriting the high activity of its core, has achieved performance upgrades, specifically manifested in the following ways: Size selectivity and anti-interference capability: The mesoporous SiO2 shell (pore size 2~4 nm) forms a "smart screen" that selectively allows small-molecule target pollutants (such as antibiotic SMX) and ozone to diffuse freely into the internal cavity, while effectively blocking large-molecule interfering substances such as humic acid. This fundamentally solves the core problem of background organic matter competing with and consuming ozone and poisoning active sites in complex water bodies, achieving targeted and selective removal of target pollutants; Enhanced confined catalytic effect: The cavity between the core and the outer shell forms a localized microreactor, which can significantly enrich reactants (pollutants and ozone), improving their performance in confined catalysis. The local concentration around the active site of the catalyst greatly improves the mass transfer efficiency and micro-reaction rate, thereby enhancing the utilization efficiency of ozone. Structure and operational stability: The SiO2 shell provides a physical protective layer for the internal active core, effectively mitigating mechanical effects such as hydraulic shear and particle friction, and isolating the active sites from direct coverage and poisoning by external macromolecular organic matter. This enables the catalyst to exhibit a significantly longer operational lifespan and activity retention rate than traditional catalysts in actual water bodies containing complex matrices. Attached Figure Description

[0021] Figure 1 These are scanning transmission electron microscope images of the catalysts prepared in Example 1 and Comparative Example 1; Figure 2 The electron spin resonance spectra of the catalysts prepared in Example 1 and Comparative Example 1 are shown. Figure 3 The diagram shows the kinetic constants of the first-order reaction for the degradation of 2,4-dichlorophenoxyacetic acid in Examples 1-6. Figure 4The diagram shows the results of the cyclic experiments in Example 1 and Comparative Example 1. Figure 5 The diagram shows the experimental results of continuous flow in Example 1 and Comparative Example 1. Detailed Implementation

[0022] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0023] Example 1: This example describes a cerium oxide-based catalyst with Ni-Ov dual active sites ( The preparation method of the catalyst is as follows.

[0024] S1. Preparation of metal precursors: 10 mg and 1.75 g Dissolved in 10 mL of deionized water, 70 mL of 5 mol / L NaOH solution was added dropwise while stirring. After precipitation, the product was hydrothermally treated at 120℃ for 24 h. After the reaction was completed, the metal precursor was obtained. S2, Precursor drying: First, wash the metal precursor obtained in S1 until the washing solution is neutral. Then, dry the washed metal precursor at 70°C for 12 h and then pass it through a 100-mesh sieve for later use. S3, Calcination activation: Under a mixed atmosphere of H2 and Ar (5% H2), the precursor treated with S2 was calcined at 400℃ for 3 h, naturally cooled to room temperature, and then ground through a 100-mesh sieve to obtain the desired product. Catalyst, denoted as catalyst 1 Example 2: The only difference between this example and Example 1 is that in step S3, the precursor powder is calcined in an air (O2) atmosphere at 400°C for 3 h using a muffle furnace. All other aspects are the same as in Example 1, and it is referred to as Comparative Catalyst 1.

[0025] Example 3: The only difference between this example and Example 1 is that the calcination time in step S3 is 0 h. Everything else is the same as in Example 1, and comparative catalyst 2 is obtained.

[0026] Example 4: The only difference between this example and Example 1 is that the calcination time in step S3 is 1 h. Everything else is the same as in Example 1, and the catalyst 2 is obtained.

[0027] Example 5: The only difference between this example and Example 1 is that the calcination time in step S3 is 2 h. Everything else is the same as in Example 1, and the catalyst 3 is obtained.

[0028] Example 6: The only difference between this example and Example 1 is that the calcination time in step S3 is 5 h. Everything else is the same as in Example 1, and the catalyst 4 is obtained.

[0029] Experimental Example 8: Catalytic ozonation performance test: The catalytic ozone oxidation performance was tested in a batch mode in a blast furnace. Sulfamethoxazole solution or other organic pollutant solutions were added to the reactor. A catalyst was added, and then ozone was introduced into the solution to initiate the reaction. During the catalytic ozone oxidation reaction, samples were drawn using a syringe at 0 min, 2.5 min, 5 min, 7.5 min, and 10 min, and the reaction was quickly quenched with sodium thiosulfate. The concentration of pollutants in the samples was detected by high-performance liquid chromatography on the same day.

[0030] In the catalytic ozone oxidation experiment, The catalyst dosage was 100 mg / L, the ozone concentration was 20 mg / L, the ozone flow rate was 50 mL / min, the pollutant concentration was 10 mg / L, and the pollutant solution volume was 50 mL.

[0031] Figure 1 The following are examples of the preparations shown in Examples 1-2 of the present invention. Scanning transmission electron microscopy (STEM) images of the catalyst. (e.g.) Figure 1 As shown, both catalyst 1 and comparative catalyst 1 achieved dispersed loading of nickel single atoms and formed oxygen vacancies. Catalyst 1 formed a special structure of oxygen vacancy-anchored single-atom nickel, realizing the construction of the Ni-O-Ce pathway, while comparative catalyst 1 did not form this structure. This indicates that the reducing atmosphere calcination process not only achieved the formation of oxygen vacancies on the surface of the metal oxide, but also achieved the special structure of oxygen vacancy-anchored single-atom metal.

[0032] Figure 2 The following are examples of the preparations shown in Examples 1-2 of the present invention. Electron spin resonance spectra of solid catalysts. (e.g.) Figure 2 As shown, asymmetric electron spin resonance signals appeared at g = 2.003 in all embodiments, but the signal was stronger with catalyst 1, while the signal intensity of catalyst 2 was weaker in comparison. Compared to calcination in an oxidizing atmosphere, calcination in a reducing atmosphere achieved better oxygen vacancy loading. This indicates that the hydrothermal synthesis and reducing atmosphere calcination processes significantly increased the concentration of oxygen vacancies on the surface of the metal oxide.

[0033] Figure 3 The following are examples of the preparations shown in Examples 1-6 of the present invention. The effect of catalysts on the ozone oxidation of pollutants 2,4-D. For example... Figure 3 As shown, the first-order reaction kinetic constant of 2,4-D treated with ozone alone within 10 min was 50.2%. After adding the control catalyst 2, which does not contain oxygen vacancies, the first-order reaction kinetic constant increased to 0.35 min. -1 The addition of oxygen-vacant catalysts 1-4 further improved the removal efficiency of 2,4-D, with the first-order reaction kinetic constants all greater than 0.5 min within 10 min. -1 The removal rate was significantly higher than that of ozone oxidation alone and the control catalyst 2. The optimal removal rate was achieved with catalyst 1, with a first-order reaction kinetic constant of 0.61 min at 10 min. -1 There is a clear positive correlation between the concentration of oxygen vacancies and the effectiveness of catalytic ozone oxidation of 2,4-D.

[0034] Table 1 shows the removal rates and first-order reaction rate constants within 10 min for novel pollutants with different electronic structures (from electron-deficient to electron-rich) in Examples 1 and 2 of this invention. After adding catalyst 1, the removal efficiency of the catalytic ozonation system for various pollutants was significantly improved. The results indicate that the oxygen vacancy-anchored Ni single-atom structure catalyst greatly promotes the removal effect of catalytic ozonation on pollutants with different properties.

[0035] Table 1. Experimental results of catalysts obtained with different preparation parameters for the catalytic degradation of various pollutants.

[0036] Figure 4 and Figure 5 The results of cyclic and continuous flow experiments for Examples 1 and 2 are shown. Under the catalyst 1 system, the removal rate of sulfamethoxazole remained at approximately 90% after five cycles, while the removal rate of sulfamethoxazole under the control catalyst 1 system was only 75% after five cycles. The 144-hour continuous flow experiment results show that the removal rate of sulfamethoxazole under the catalyst 1 system remained consistently high, exceeding 85%, while the removal effect of sulfamethoxazole under the control catalyst 1 system was limited, fluctuating between 50% and 75%. These results indicate that the high stability and durability of the cerium oxide catalyst with oxygen vacancy structures anchoring nickel single-atom sites demonstrate significant application potential in catalytic ozone oxidation.

[0037] Example 9: This example describes a cerium oxide-based catalyst with Ni-Ov dual active sites ( The preparation method of ) is as follows.

[0038] S1~S3: Core Catalyst ( The preparation of the catalyst was carried out in exactly the same manner as in Example 1, resulting in the core catalyst. S4: Catalyst surface amination: Take 1.0 g of the core catalyst prepared in S3, add 150 mL of anhydrous ethanol, and sonicate for 35 min to obtain suspension A. Place suspension A in a reflux condenser, and slowly add 1.0 mL of APTES under continuous stirring and N2 atmosphere. Heat to 72℃ and reflux for 5 h. After the reaction is complete, cool to room temperature, wash the product three times with anhydrous ethanol by centrifugation, and dry under vacuum at 58℃ for 6 h to obtain the aminated product, denoted as CeO2-Ni-NH2; S5: Sacrificial layer coating: Dissolve 0.75 g of glucose in 45 mL of deionized water and stir until clear. Add 0.75 g of CeO2-Ni-NH2 and sonicate for 35 min. Transfer the mixture to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and hydrothermally react at 170 °C for 5.5 h. After natural cooling, wash the product three times alternately with deionized water and ethanol, and dry at 58 °C to constant weight to obtain CeO2-Ni@C; S6: Outer casing: Preparation of template agent solution: Dissolve 0.225 g CTAB in a mixed solution of 75 mL anhydrous ethanol and 25 mL deionized water, and add 1.0 mL of 28 wt% ammonia solution while stirring. Place the mixture in a 38℃ water bath and stir for 35 min to obtain clear solution A; Coating reaction: 0.4 g CeO2-Ni@C was dispersed in 25 mL anhydrous ethanol and ultrasonically dispersed for 25 min. This dispersion was mixed with solution A, and the system was kept at a constant temperature of 35 °C with continuous stirring. 0.8 mL TEOS was mixed with 10 mL anhydrous ethanol and slowly added dropwise to the above mixture. After the addition was complete, stirring was continued for 24 h. Post-processing: The product was collected by centrifugation, washed three times with anhydrous ethanol, and dried at 60°C to constant weight to obtain an intermediate with a "core-carbon-shell" three-layer structure, denoted as CeO2-Ni@C@SiO2; S7: Preparation of core-cavity-shell structure: CeO2-Ni@C@SiO2 was placed in a tube furnace and calcined in an air atmosphere (flow rate 55 sccm) using a programmed temperature rise method: the temperature was increased from room temperature to 345℃ at a rate of 2℃ / min and held for 1.8 h; then increased to 545℃ at a rate of 3℃ / min and held for 3.8 h. After natural cooling to room temperature, the final core-cavity-shell structured catalyst was obtained, denoted as catalyst C1.

[0039] Example 10: Unlike Example 9, in S4, 1.0 g of core catalyst was taken, 150 mL of anhydrous ethanol was added, ultrasonically dispersed for 30 min, 0.8 mL of APTES was slowly added dropwise, the temperature was raised to 70 °C and refluxed for 4 h, and the product was vacuum dried at 55 °C.

[0040] Example 11: Unlike Example 9, in S4, 2.0 g of core catalyst was taken, 200 mL of anhydrous ethanol was added, ultrasonically dispersed for 40 min, 2.0 mL of APTES was slowly added dropwise, the temperature was raised to 75°C and refluxed for 6 h, and the product was vacuum dried at 60°C.

[0041] Example 12: Unlike Example 9, in S5, 0.5 g of glucose was dissolved in 40 mL of deionized water, and 0.5 g of Ni-CeO2-NH2 was added. The mixture was then subjected to a hydrothermal reaction at 160 °C for 6 h.

[0042] Example 13: Unlike Example 9, in S5, 1.0 g of glucose was dissolved in 50 mL of deionized water, and 1.0 g of Ni-CeO2-NH2 was added. The mixture was then subjected to a hydrothermal reaction at 180°C for 5 h.

[0043] Example 14: Unlike Example 9, in S6-1, 0.2 g CTAB was dissolved in a mixed solution of 70 mL anhydrous ethanol and 20 mL deionized water, and 0.5 mL 28 wt% ammonia was added. The mixture was stirred at a constant temperature of 35°C for 30 min.

[0044] Example 15: Unlike Example 9, in S6-1, 0.25 g CTAB was dissolved in a mixed solution of 80 mL anhydrous ethanol and 30 mL deionized water, and 2.0 mL 28 wt% ammonia was added. The mixture was stirred at a constant temperature in a 40°C water bath for 40 min.

[0045] Example 16: Unlike Example 9, in S6-2, 0.3 g Ni-CeO2@C was dispersed in 20 mL of anhydrous ethanol and then the coating reaction was carried out.

[0046] Example 17: Unlike Example 9, in S6-2, 0.5 g Ni-CeO2@C was dispersed in 30 mL of anhydrous ethanol and then the coating reaction was carried out.

[0047] Example 18: Unlike Example 9, in S7, at an air flow rate of 50 sccm, the temperature was first increased to 340°C at 1°C / min and held for 2 h, and then increased to 540°C at 2°C / min and held for 4 h.

[0048] Example 19: Unlike Example 9, in S7, at an air flow rate of 60 sccm, the temperature was first increased to 350°C at 3°C / min and held for 1.5 h, and then increased to 550°C at 4°C / min and held for 3.5 h.

[0049] Example 20: This example describes the structural characterization and performance verification experiments of catalyst C1.

[0050] Transmission electron microscopy (TEM) revealed that the C1 catalyst exhibited a uniform spherical core-cavity-shell structure. Statistical analysis showed an overall particle size of approximately 90 ± 5 nm, a core (CeO2-Ni) particle size of approximately 48 ± 2 nm, a cavity layer thickness of approximately 12 ± 1 nm, and an outer mesoporous SiO2 shell thickness of approximately 9 ± 1 nm. Nitrogen adsorption-desorption tests indicated that the mesopore size of the outer shell was concentrated in the range of 2.5–3.5 nm.

[0051] Performance verification experiments: To verify its size selectivity and anti-interference ability, two sets of control experiments were designed: System A (clean water): 50 mL of 10 mg / L sulfamethoxazole solution.

[0052] System B (complex water body): 50 mL of a mixed solution containing 10 mg / L sulfamethoxazole and 20 mg / L humic acid (HA, average molecular weight >1000 Da, hydrated size >5 nm).

[0053] Add 100 mg / L of catalyst C1 to systems A and B respectively, introduce ozone (concentration 20 mg / L, flow rate 50 mL / min), react for 10 minutes, and monitor the removal rate of SMX.

[0054] Experimental results: In system A (clean water), catalyst C1 achieved a 99.5% removal rate of SMX within 10 minutes.

[0055] In system B (complex water body), the removal rate of SMX by catalyst C1 remained at 98.1% after 10 minutes.

[0056] Conclusion: The removal efficiency of catalyst C1 for the target small molecule pollutant (SMX) was almost unaffected in the presence of a large amount of macromolecular interference (humic acid), which proves that its shell has excellent size sieving function and can effectively prevent humic acid from entering the internal poisoning active sites or ineffectively consuming ozone.

[0057] Example 21: Comparative experiment on excessively large pore size in mesoporous shells.

[0058] This embodiment aims to demonstrate that when the pore size of the outer shell is too large, the catalyst will lose its size selectivity.

[0059] Preparation steps: The preparation steps were basically the same as in Example 9, except that the template agent in the S6 shell coating was changed. CTAB was replaced with an equal mass of F127 (ethylene oxide-propylene oxide-ethylene oxide triblock copolymer), and the amount of ammonia was adjusted to 0.5 mL, with the water bath temperature raised to 40°C. All other steps and parameters were identical to those in Example 9.

[0060] The prepared catalyst is designated as control catalyst C2. TEM shows that it still has a core-cavity-shell structure, but BET testing indicates that the mesopore size of its shell has increased to 8-10 nm.

[0061] Performance verification experiment: Using comparative catalyst C2, SMX degradation experiments were conducted in the same systems A (clean water) and B (complex water) as in Example 20.

[0062] Experimental results: In system A, the removal rate of SMX by catalyst C2 within 10 minutes was 98.8%, which was comparable to that of C1.

[0063] In system B, the removal rate of SMX by catalyst C2 dropped sharply to 62.3% after 10 minutes.

[0064] Conclusion: Because the shell pore size (8-10 nm) is much larger than the hydration size of humic acid molecules, humic acid can enter the cavity, compete with SMX for active sites, and consume ozone, resulting in a significant decrease in SMX degradation efficiency. This conversely demonstrates that the 2.5-3.5 nm pore size shell in Example 9 is crucial for achieving size selectivity.

[0065] Example 22: Comparative Experiment of Mesoporous Shell (Core Only) This embodiment aims to demonstrate that without the physical sieving protection of the outer shell, the performance of the core catalyst in complex water bodies will be severely compromised.

[0066] Preparation steps: The catalyst 1 prepared in Example 1 was used directly for testing.

[0067] Performance verification experiment: Using catalyst 1, SMZ degradation experiments were conducted in systems A and B, which were identical to those in Example 20.

[0068] Experimental results: In system A, catalyst 1 achieved a 99.8% removal rate of SMX within 10 minutes (consistent with the data in Table 1).

[0069] In system B, the removal rate of SMX by catalyst 1 decreased significantly to 45.7% within 10 minutes.

[0070] Conclusion: When high-performance core catalysts are directly exposed to complex water bodies, their active sites are rapidly covered and poisoned by humic acid, ozone is largely and ineffectively consumed, and catalytic efficiency drops sharply. This highlights the necessity of encapsulating them with a mesoporous shell that has sieving function.

[0071] Example 23: Verification experiment on the effect of cavity thickness on mass transfer.

[0072] This embodiment aims to investigate the effect of cavity thickness (sacrificial carbon layer thickness) on catalytic performance.

[0073] Preparation steps: The preparation steps are basically the same as in Example 9, except that the amount of glucose added in the S5 sacrificial layer coating is changed.

[0074] Catalyst C3 was implemented with glucose addition reduced to 0.3 g (otherwise the same as C1), which is expected to form a thinner carbon layer (~5 nm) and a narrower cavity.

[0075] Catalyst C4 was implemented by increasing the amount of glucose added to 1.5 g (others are the same as C1), which is expected to form a thicker carbon layer (~20 nm) and a wider cavity.

[0076] Performance verification experiment: In system A (clean water), the degradation kinetics of SMX by C1, C3, and C4 were compared.

[0077] Experimental results: Catalyst C1 (cavity ~12 nm): First-order reaction rate constant k = 0.66 min -1 .

[0078] Catalyst C3 (cavity ~5 nm): k = 0.58 min -1 An excessively small cavity may limit the accumulation of reactants around the active site, leading to restricted mass transfer.

[0079] Catalyst C4 (cavity ~20 nm): k = 0.63 min -1 Increasing the cavity size has a slight benefit to mass transfer, but an excessively large cavity may reduce the density of active sites per unit volume, and the mechanical strength of the shell may be weakened.

[0080] Conclusion: There is an optimal range for cavity thickness (approximately 10-13 nm). Too thin a cavity limits mass transfer, while too thick a cavity may sacrifice mechanical strength with limited benefits, thus proving the rationality of the parameter design in Example 9.

[0081] As can be seen from the series of comparisons of Examples 9, 20 to 23, the following can be observed: The implementation of catalyst C1 (standard) successfully achieved "size selectivity," enabling efficient and selective degradation of small molecule targets in complex water bodies. This selectivity is lost if the shell pore size is too large (compared to catalyst C2) or if there is no shell at all (using catalyst 1). The cavity size in the core-cavity-shell structure needs to be optimized (e.g., compared to C1, C3, and C4) to balance enhanced mass transfer with structural stability. These experiments collectively validate... Advantages of catalyst "intelligent targeting" design.

Claims

1. A cerium oxide-based catalyst with Ni-Ov dual active sites, characterized in that, The Ni-Ov dual-active-site cerium oxide-based catalyst comprises a support and an active component supported on the support. The support consists of a cerium oxide support and oxygen vacancy structures thereon, and the active component is a single nickel atom. The oxygen vacancy structure can anchor the active center of a nickel single atom, making the oxygen vacancy structure and the nickel single atom form a dual active site. The mass content of nickel single atoms in the cerium oxide-based catalyst with Ni-Ov dual active sites is 0.5–2 wt%.

2. The method for preparing a Ni-Ov dual-active-site cerium oxide-based catalyst as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of metal precursors: Will and Dissolve in deionized water, add NaOH solution dropwise while maintaining stirring, precipitate out, and then hydrothermally treat at 100~130℃ for 20~24 h to obtain the metal precursor after the reaction is complete; Let n be the multiplier and Then the The amount added is [10n, 20n] mg. The amount of [1.75n, 3.5n] g added, the amount of deionized water added, the amount of [10n, 12n] mL added, the concentration of NaOH solution is 2~5 mol / L, and the amount of [70n, 80n] mL added; S2, Precursor drying: First, wash the metal precursor obtained in S1 until the washing solution is neutral. Then, dry the washed metal precursor at 60~130℃ for 6~12 h and then sieve it for later use. S3, Calcination activation: Under a reducing atmosphere, the precursor treated with S2 was calcined at 300–600 °C for 2–6 h, and after natural cooling to room temperature, it was ground and sieved to obtain a cerium oxide-based catalyst with Ni-Ov dual active sites. catalyst.

3. The method for preparing a Ni-Ov dual-active-site cerium oxide-based catalyst as described in claim 2, characterized in that, The reducing atmosphere described in S3 is or and The mixture of gases.

4. The method for preparing a Ni-Ov dual-active-site cerium oxide-based catalyst as described in claim 2, characterized in that, The S3 is treated by the coating-template sacrifice method. The catalyst can be further used to prepare cerium oxide-based catalysts with Ni-Ov dual active sites in a core-cavity-shell structure.

5. The application of a cerium oxide-based catalyst with Ni-Ov dual active sites prepared by the method according to any one of claims 2 to 4, characterized in that, The cerium oxide-based catalyst is used in a water system containing organic pollutants, and the organic pollutants are degraded by introducing ozone.

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