Preparation method and application method of non-high-temperature pyrolysis metal monatomic catalyst
A three-dimensional porous non-high-temperature pyrolysis metal single-atom catalyst was prepared by a solvothermal method under low-temperature conditions, which solved the problems of low efficiency and secondary pollution of traditional catalysts and achieved efficient and stable degradation of organic pollutants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN AGRICULTURAL UNIVERSITY
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-26
AI Technical Summary
Traditional heterogeneous catalysts suffer from problems such as low atom utilization, insufficient exposure of active sites, and easy precipitation of metal ions when treating recalcitrant organic pollutants, resulting in low catalytic efficiency and easy secondary pollution. High-temperature pyrolysis preparation methods are also prone to metal atom aggregation and support structure collapse.
A non-high-temperature pyrolysis metal single-atom catalyst was prepared under low-temperature conditions using a solvothermal method. Amide solvents were used as dispersants, reducing agents, and nitrogen sources, combined with graphene oxide and transition metal compounds to form a three-dimensional porous non-high-temperature pyrolysis metal single-atom catalyst, thus avoiding metal atom aggregation and support structure collapse caused by high-temperature pyrolysis.
This catalyst achieves high atom utilization and good stability, exhibits high efficiency in catalyzing the degradation of organic pollutants by persulfate, and avoids high energy consumption and secondary pollution. It also features a three-dimensional porous structure that provides abundant mass transfer channels and high catalytic activity.
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Figure CN122076513A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of catalyst technology, and in particular to a method for preparing and applying a non-high-temperature pyrolysis metal single-atom catalyst. Background Technology
[0002] With the acceleration of global industrialization and the expansion of urbanization, water pollution has become an increasingly prominent problem. Various complex organic pollutants, such as organic dyes in textile dyeing wastewater, antibiotic residues in the medical field, chemical fertilizers and pesticides in agricultural production, and various additives in the food industry, are discharged in large quantities into natural water bodies. These pollutants are typically chemically stable and poorly biodegradable (i.e., recalcitrant), and their long-term persistence poses a serious challenge to the balance of aquatic ecosystems. Therefore, developing efficient water pollution treatment and remediation technologies has become a critical issue urgently needing to be addressed in the field of environmental protection.
[0003] Advanced oxidation technologies based on persulfate (PMS) are widely used to treat recalcitrant organic wastewater due to their strong oxidizing power and wide applicability. PMS, under catalysis, can generate highly oxidizing free radicals (such as hydroxyl radicals and sulfate radicals) that efficiently degrade pollutants. However, traditional heterogeneous catalysts suffer from low atom utilization, insufficient exposure of active sites, and easy precipitation of metal ions, resulting in low catalytic efficiency and a high risk of secondary pollution.
[0004] While single-atom catalysts (SACs) boast near 100% atom utilization, current mainstream preparation methods rely on high-temperature pyrolysis (>700℃). This process not only consumes enormous amounts of energy but also readily leads to the migration and aggregation of high-surface-energy metal atoms, resulting in the loss of single-atom properties. Furthermore, the intense heat treatment often causes the collapse of the support's pore structure, limiting substrate transport. Therefore, developing a method for preparing highly stable single-atom catalysts under mild conditions is of great significance. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst and its application method. The catalyst prepared by this method has high atomic utilization, good stability, and high efficiency in catalyzing the degradation of organic pollutants by persulfate.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, embodiments of the present invention provide a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst, the preparation method comprising the following steps: S100, Dispersion: Graphene oxide and transition metal compounds are dispersed in amide solvents to obtain graphene oxide dispersion and metal precursor dispersion, respectively. S200, Mixing: The graphene oxide dispersion and the metal precursor dispersion are mixed and homogenized under physical field-assisted treatment to obtain a mixed precursor suspension. S300, Solvothermal: The mixed precursor suspension is placed in a closed reaction vessel and subjected to a solvothermal reaction under autogenous pressure and heating conditions. After the reaction is completed, the mixture is cooled to obtain an intermediate product containing metal-graphene hydrogel. S400, Purification and Drying: The intermediate product is washed and purified using a polar solvent, and then vacuum dried to obtain a non-high-temperature pyrolysis metal single-atom catalyst. S500, Grinding: The obtained non-high-temperature pyrolysis metal single-atom catalyst is ground into powder.
[0007] In some embodiments, in step S100, the transition metal compound is one or more of transition metal phthalocyanine compounds, transition metal porphyrin compounds, and transition metal salts.
[0008] In some embodiments, in step S100, the amide solvent is at least one of formamide, N,N-dimethylformamide, and N,N-dimethylacetamide.
[0009] In some embodiments, in step S100, the mass ratio of the graphene oxide to the transition metal compound is 2:1 to 10:1.
[0010] In some embodiments, in step S200, the physical field-assisted treatment is at least one of ultrasonic crushing, ultrasonic dispersion, and mechanical stirring; The homogenization process takes 10 to 60 minutes.
[0011] In some embodiments, in step S300, the temperature of the solvothermal reaction is 160°C to 240°C, and the reaction time is 6 hours to 24 hours.
[0012] In some embodiments, in step S400, the polar solvent is a mixed solution of ethanol and water; the washing and purification time is more than 3 hours.
[0013] Secondly, embodiments of the present invention also provide a non-high-temperature pyrolysis metal single-atom catalyst, which is prepared by the preparation method of the non-high-temperature pyrolysis metal single-atom catalyst described above. The catalyst is a non-high-temperature pyrolysis type nitrogen-doped graphene-based supported transition metal single-atom catalyst and has a three-dimensional porous structure.
[0014] Thirdly, the embodiments of the invention also provide a method for applying the non-high-temperature pyrolysis metal single-atom catalyst as described above, the method comprising: The non-high-temperature pyrolysis metal single-atom catalyst is dispersed in wastewater containing organic pollutants and stirred until the non-high-temperature pyrolysis metal single-atom catalyst and the organic pollutants reach an adsorption-desorption equilibrium state. Then, persulfate is added to degrade the organic pollutants.
[0015] In some embodiments, the pH value of the wastewater is 2-14; and / or, The organic pollutants are one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.
[0016] In some embodiments, the mass ratio of the non-high-temperature pyrolytic metal single-atom catalyst to the persulfate is 1:1.5 to 1:16; and / or, The molar ratio of the organic pollutant to the persulfate is 1:1 to 20:1.
[0017] The present invention provides a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst and its application method, which has the following beneficial effects; 1. Green and low-carbon process, avoiding high-temperature pyrolysis: This invention eliminates the inert atmosphere high-temperature calcination (>700℃) step required in the preparation of traditional single-atom catalysts, and adopts a solvothermal one-step method, which can complete the preparation at a lower temperature (e.g., 200℃). This not only significantly reduces the energy consumption and equipment cost of the preparation, but also effectively avoids the problems of metal atom agglomeration and support structure collapse caused by high temperatures.
[0018] 2. Synergistic effect mechanism of multifunctional solvent: This invention innovatively uses amide solvents (such as formamide) as the reaction medium. During the solvothermal process, the amide solvent plays a triple role as a dispersant, reducing agent and nitrogen source: it can not only effectively reduce graphene oxide, but also achieve nitrogen doping of the graphene lattice in situ, and assist metal single atoms to be stably anchored on the carrier surface through coordination bonds, thus simplifying the preparation process.
[0019] 3. Unique three-dimensional structure and excellent performance: The prepared catalyst possesses a three-dimensional graphene hydrogel-derived porous structure, which provides abundant mass transfer channels and greatly increases the exposed area of catalytic active sites. Experiments show that this catalyst exhibits excellent catalytic activity and stability when activating persulfate to degrade organic pollutants, and the metal ion dissolution rate is extremely low, effectively solving the problems of easy deactivation and secondary pollution caused by traditional catalysts.
[0020] 4. This non-high-temperature pyrolysis metal single-atom catalyst has the advantages of mild reaction conditions (room temperature), high removal efficiency of organic pollutants, good stability of nano-metal catalyst, and low dissolution of heavy metal ions when used to activate persulfate degradation to remove organic pollutants. It is superior to traditional nano-metal catalysts and metal oxide catalysts in terms of degradation efficiency and metal ion dissolution. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual process of the method, etc. involved in the embodiments of this disclosure.
[0022] Figure 1 This is the preparation process and characterization diagram of the non-high-temperature pyrolysis metal single-atom catalyst in Example 1; Figure 2 These are the Fourier transform infrared spectrum, nitrogen adsorption-desorption isotherm, pore size distribution map, and Raman spectrum of the non-high-temperature pyrolysis metal single-atom catalyst in Example 1. Figure 3 This is a graph showing the recycling performance of the non-high-temperature pyrolysis metal single-atom catalyst in this embodiment for removing organic pollutants from water using persulfate, and a comparison of k values at different cycle numbers. Figure 4 This is a performance graph and a comparison graph of k values of the non-high-temperature pyrolysis metal single-atom catalyst in Example 1 under different acid and base conditions; Figure 5 These are X-ray diffraction patterns of five non-high-temperature pyrolysis metal single-atom catalysts in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. Figure 6 This is a comparative performance graph showing the catalytic efficiency of non-high-temperature pyrolysis metal single-atom catalysts for the degradation of Rhodamine B by persulfate using ten different preparation and application methods in Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9. Detailed Implementation
[0023] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.
[0024] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.
[0025] Unless otherwise stated, all raw materials and reagents used in the embodiments of this application were obtained through commercial purchase or synthesized using conventional methods existing in the art. Unless otherwise stated, all experimental methods in the embodiments of this application are conventional methods.
[0026] This invention provides a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst, the preparation method including steps S100~S500.
[0027] S100, Dispersion: Graphene oxide and transition metal compounds are dispersed in amide solvents to obtain graphene oxide dispersion and metal precursor dispersion, respectively.
[0028] S200, Mixing: The graphene oxide dispersion and the metal precursor dispersion are mixed and homogenized under the assistance of a physical field to obtain a mixed precursor suspension.
[0029] S300, solvothermal: The mixed precursor suspension is placed in a closed reaction vessel and subjected to a solvothermal reaction under autogenous pressure and heating conditions. After the reaction is completed, the mixture is cooled to obtain an intermediate product containing a metal-graphene hydrogel.
[0030] S400, purification and drying: The intermediate product is washed and purified using a polar solvent, and then vacuum dried to obtain a non-high-temperature pyrolysis metal single-atom catalyst.
[0031] S500, Grinding: The obtained non-high-temperature pyrolysis metal single-atom catalyst is ground into powder.
[0032] In step S100, the transition metal compound is one or more of the following: transition metal phthalocyanine compounds, transition metal porphyrin compounds, and transition metal salts.
[0033] For example, the transition metal compound is a metal phthalocyanine compound with a macrocyclic conjugated structure, such as cobalt phthalocyanine (Co(II)-Pc), iron phthalocyanine, or nickel phthalocyanine.
[0034] Preferably, the transition metal compound in this application is cobalt phthalocyanine. This application utilizes the strong stacking interaction between the macrocyclic conjugated structure of the cobalt phthalocyanine molecule and graphene oxide and its reduction products to achieve pre-anchoring of the precursor molecule.
[0035] Furthermore, in this preparation method, Co(II)-Pc molecules are uniformly adsorbed onto the surface of graphene sheets by non-covalent bonding forces. Since the Co atoms are pre-coordinated to the four nitrogen atom centers of the phthalocyanine ring (forming a stable cobalt-nitrogen tetrastructure), this rigid macrocyclic ligand produces significant steric hindrance and confinement effects, effectively blocking direct contact between metal atoms. Thus, without high-temperature pyrolysis and carbonization, the aggregation and migration of metal atoms are directly suppressed, ultimately successfully constructing atomically dispersed cobalt active sites on the nitrogen-doped graphene support.
[0036] In step S100, to ensure good dispersion of graphene oxide and transition metal compounds, the amide solvent is at least one of formamide (FA), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC). That is, the amide solvent is one or more of the above three.
[0037] For example, formamide is the preferred amide solvent due to its excellent peeling and reducing properties.
[0038] In step S100, the concentration of graphene oxide in the dispersion is 2-10 mg / mL, and the concentration of the metal precursor in the dispersion is 0.5-5 mg / mL.
[0039] In step S100, the mass ratio of graphene oxide to transition metal compound is 2:1 to 10:1.
[0040] In step S200, the physical field-assisted treatment is at least one of ultrasonic crushing, ultrasonic dispersion, and mechanical stirring. That is, the physical field-assisted treatment is one or more of the above three methods.
[0041] For example, this application employs a processing method combining ultrasonic dispersion and mechanical stirring. By combining ultrasonic dispersion with vigorous mechanical stirring, metal phthalocyanine molecules are uniformly adsorbed onto the surface of graphene oxide sheets.
[0042] The ultrasound duration ranges from 10 to 60 minutes, and the ultrasound power ranges from 100W to 500W.
[0043] In step S300, the temperature of the solvothermal reaction is 160℃~240℃, and the reaction time is 6 hours~24 hours.
[0044] For example, the temperature of the solvothermal reaction is preferably 180°C-200°C, and the reaction time is preferably 10-14 hours. Within this temperature and time range, amide solvents (especially formamide) can decompose to generate reducing species, inducing partial reduction of graphene oxide and self-assembly to form a three-dimensional hydrogel, while firmly locking the metal precursor in the interlayer without causing damage to the phthalocyanine ring structure.
[0045] In step S400, the polar solvent is a mixture of ethanol and water; the washing and purification time is more than 3 hours to remove unreacted precursors and solvent residues.
[0046] For example, the volume ratio of the ethanol to water mixture is 1:5 to 1:10.
[0047] This invention also provides a non-high-temperature pyrolysis metal single-atom catalyst, which is prepared by the preparation method of the non-high-temperature pyrolysis metal single-atom catalyst described above. The catalyst is a non-high-temperature pyrolysis type nitrogen-doped graphene-based supported transition metal single-atom catalyst and has a three-dimensional porous structure.
[0048] This invention also provides a method for applying the non-high-temperature pyrolysis metal single-atom catalyst as described above, the method including: A non-high-temperature pyrolysis metal single-atom catalyst is dispersed in wastewater containing organic pollutants and stirred until the non-high-temperature pyrolysis metal single-atom catalyst and organic pollutants reach an adsorption-desorption equilibrium state. Then, persulfate is added to degrade the organic pollutants.
[0049] In some embodiments, the pH value of the wastewater is 2 to 14.
[0050] For example, the pH value of the wastewater is 2, 6, 10, 14, etc. By controlling the pH value of the wastewater, it can be ensured that the non-high-temperature pyrolysis metal single-atom catalyst can have better activity at the pH value of the wastewater, thereby effectively catalyzing persulfate to fully decompose organic pollutants.
[0051] In some embodiments, the organic pollutant is one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.
[0052] For example, organic pollutants may include Rhodamine B, methylene blue, methylene blue, malachite green, Orange G, sulfonamides, tetracycline, oxytetracycline, carbamazepine, bisphenol A, p-chlorophenol, phenol, 2,4,6-trichlorophenol, and aniline, etc. Therefore, this non-high-temperature pyrolysis metal single-atom catalyst can be used to catalyze the decomposition of organic pollutants by persulfate, and it decomposes a wide variety of organic pollutants, thus having broad application prospects.
[0053] In some embodiments, the mass ratio of the non-high-temperature pyrolysis metal single-atom catalyst to persulfate is 1:1.5 to 1:16; and / or, the molar ratio of organic pollutants to persulfate is 1:1 to 20:1.
[0054] For example, the mass ratio of the non-high-temperature pyrolysis metal single-atom catalyst to permonosulfate is 1:1.5, 1:5, 1:10, 1:16, etc., and the molar ratio of organic pollutants to permonosulfate is 1:1, 5:1, 10:1, 15:1, 20:1, etc. By setting the mass ratio of the non-high-temperature pyrolysis metal single-atom catalyst to permonosulfate and the molar ratio of organic pollutants to permonosulfate, it can be ensured that the non-high-temperature pyrolysis metal single-atom catalyst fully catalyzes the permonosulfate and that the permonosulfate fully decomposes the organic pollutants.
[0055] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.
[0056] Example 1 Example 1 of this invention discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst, the preparation method including steps S100~S500.
[0057] S100, Dispersion: Weigh 100 mg of graphene oxide (GO) and add it to a beaker containing 15 mL of formamide (FA, as an amide solvent). Treat the beaker with an ultrasonic cell disruptor for 15 minutes to obtain a uniformly dispersed graphene oxide dispersion (suspension A). Separately weigh 20 mg of cobalt phthalocyanine (Co(II)-Pc, as a transition metal compound) and add it to another beaker containing 15 mL of formamide. Disperse the mixture with ultrasonication to obtain a metal precursor dispersion (suspension B).
[0058] S200, Mixing: Under ultrasonic dispersion-assisted conditions, the metal precursor dispersion (suspension B) is slowly added to the graphene oxide dispersion (suspension A). After mixing, the mixture is vigorously mechanically stirred at room temperature (as a homogenization treatment) until a homogeneous mixed precursor suspension (suspension C, i.e., a non-pyrolytic metal single-atom suspension) is formed.
[0059] S300, Solvothermal: The mixed precursor suspension (suspension C) was transferred to a stainless steel high-pressure reactor (closed reaction vessel) with a polytetrafluoroethylene liner. The reactor was placed in an oven and heated at 200°C for 12 hours for a solvothermal reaction. During this process, the self-generated pressure and the reducing properties of formamide induced the self-assembly of graphene oxide. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a black intermediate product containing a metal-graphene hydrogel.
[0060] S400, Purification and Drying: The intermediate product was removed and immersed in a 1:9 volume ratio ethanol / water mixture for 6 hours to remove residual solvent and unadsorbed impurities. Subsequently, the purified hydrogel was vacuum dried overnight to obtain a non-high-temperature pyrolysis metal single-atom catalyst.
[0061] S500, Grinding: The obtained non-high temperature pyrolysis metal single-atom catalyst is ground into powder, thus obtaining a non-high temperature pyrolysis nitrogen-doped graphene-based supported cobalt single-atom catalyst.
[0062] This embodiment also discloses a method for applying a non-high-temperature pyrolysis metal single-atom catalyst, the method of which is as follows: Add 100 mL of 10 μM Rhodamine B (RhB) solution to a 250 mL glass beaker and place the glass beaker on a magnetic stirrer and stir at a speed of 500 rpm. Weigh 5 mg of the above-mentioned non-high temperature pyrolysis metal single-atom catalyst using an analytical balance and add it to the above-mentioned Rhodamine B solution. Sonicate for 1 min to disperse the non-high temperature pyrolysis metal single-atom catalyst evenly. Stir for 30 min to allow the non-high temperature pyrolysis metal single-atom catalyst and Rhodamine B molecules to reach an adsorption-desorption equilibrium state. 30.7 mg of persulfate powder was added to a mixed solution of a non-high-temperature pyrolysis metal single-atom catalyst and Rhodamine B to initiate the oxidative degradation reaction. At a predetermined time point, 3 mL of the reaction solution was taken out, filtered, and the residual concentration of Rhodamine B in the solution was tested using a UV spectrophotometer to determine the removal effect.
[0063] like Figure 1 As shown, Figure 1 The image shows the characterization diagram of a non-high-temperature pyrolysis metal single-atom catalyst, in which... Figure 1 Figure 'a' shows the synthesis process of this non-high-temperature pyrolysis metal single-atom catalyst. It illustrates the state of the raw materials before the synthesis reaction, the synthesis reaction vessel, the reaction conditions, and the appearance of the catalyst after the reaction. Its morphology is that of a porous solid material with high mechanical stability. Figure 1 b and Figure 1 c shows the low-magnification and high-magnification scanning electron microscope (SEM) images of this non-high-temperature pyrolysis metal single-atom catalyst. Figure 1 b indicates that the morphological characteristics of this non-high-temperature pyrolysis metal single-atom catalyst exhibit a highly cross-linked porous network structure. Figure 1 Further analysis in c reveals that the network consists of numerous coiled, stacked, and folded sheet-like structures, forming abundant layered pores, which indicates that the material has an extremely high specific surface area. Figure 1 d and Figure 1e is a transmission electron microscope (TEM) image of this non-high-temperature pyrolysis metal single-atom catalyst. Figure 1 The porous and lamellar framework characteristics of the material were confirmed again in section d. Figure 1 The result shows that the edge region of the thin sheet mainly exhibits an irregular short-range ordered structure, without clear long-range ordered lattice fringes, indicating that the material is an amorphous carbon or a carbon structure with a low degree of graphitization. Figure 1 f, Figure 1 h, Figure 1 i, Figure 1 j is the energy dispersive X-ray spectroscopy (EDS) elemental mapping of this non-high-temperature pyrolysis metal single-atom catalyst, showing the distribution of carbon, oxygen, nitrogen, and cobalt on the catalyst. This demonstrates that these elements are uniformly and densely dispersed throughout the porous carbon framework, indicating successful uniform doping or loading. Figure 1 k is a low-resolution, high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of this non-high-temperature pyrolysis metal single-atom catalyst. Figure 1 k clearly reveals the porous, interconnected nanonetwork framework of the material. At this resolution, no obvious nanoparticle aggregation was observed, initially suggesting that the active component has extremely high dispersibility. Figure 1 l is a HAADF-STEM image of this non-high-temperature pyrolysis metal single-atom catalyst under aberration-corrected transmission electron microscopy. From Figure 1 In the image, uniformly dispersed cobalt single atoms are clearly visible scattered on the carbon matrix, and no obvious cobalt metal particles were found.
[0064] Combination Figure 2 As shown, Figure 2 a is the Fourier transform infrared (FT-IR) spectrum of a non-high-temperature pyrolysis metal single-atom catalyst, derived from... Figure 2 As can be seen from a, the surface of this non-high-temperature pyrolysis metal single-atom catalyst contains abundant oxygen- and nitrogen-containing functional groups. Figure 2 b is the nitrogen adsorption-desorption isotherm diagram of this non-high-temperature pyrolysis metal single-atom catalyst, from... Figure 2 b indicates that this non-high-temperature pyrolysis metal single-atom catalyst has a high specific surface area and strong adsorption capacity. Figure 2 c is the pore size distribution diagram of this non-high-temperature pyrolysis metal single-atom catalyst, from Figure 2 c indicates that this non-high-temperature pyrolysis metal single-atom catalyst has a well-developed mesoporous and macroporous structure. Figure 2 d is the Raman spectrum of the non-high-temperature pyrolysis metal single-atom catalyst. From 2d, it can be inferred that the non-high-temperature pyrolysis metal single-atom catalyst has a large number of structural defect sites, which provide anchoring points for the regulation of cobalt.
[0065] In summary, the preparation method provided in Example 1 successfully synthesized a carbon-supported non-high-temperature pyrolysis metal single-atom catalyst, successfully combining highly dispersed metal single-atom active sites with a porous carbon framework possessing rapid transport channels. The high specific surface area, large pore size, and single-atom dispersion of this non-high-temperature pyrolysis metal single-atom catalyst give it enormous application potential in catalysis, energy storage, and sensing.
[0066] Figure 3 The removal of Rhodamine B by persulfate using a non-high-temperature pyrolytic metal single-atom catalyst was investigated in four consecutive cycles. The catalyst's removal efficiency was shown in the diagram. In each cycle, the non-high-temperature pyrolytic metal single-atom catalyst from the previous reaction was repeatedly washed with methanol and deionized water before being added to the next reaction. Figure 3 As shown in a, the non-high-temperature pyrolysis metal single-atom catalyst maintained high activity after four consecutive cycles and was still able to completely degrade Rhodamine B. Figure 3 b represents the rate constant change of the catalyst for the removal of Rhodamine B from persulfate by the non-high-temperature pyrolysis metal single-atom catalyst during four consecutive cycles, demonstrating the good cycle stability and reusability potential of the non-high-temperature pyrolysis metal single-atom catalyst.
[0067] Figure 4 The effect of this non-high-temperature pyrolytic metal single-atom catalyst on the removal of Rhodamine B from persulfate was evaluated under different application solution pH values. The reaction was carried out at pH=3, pH=5, pH=7, and pH=9 by using buffer solutions. Figure 4 As shown in a, the non-high-temperature pyrolysis metal single-atom catalyst maintains its removal efficiency for Rhodamine B under different solution pH values. Figure 4 b represents the rate constant change of the non-high-temperature pyrolysis metal single-atom catalyst for the removal of Rhodamine B from persulfate under different solution pH conditions. This indicates that the non-high-temperature pyrolysis metal single-atom catalyst has broad acid-base adaptability and is suitable for practical applications.
[0068] Comparative Example 1 Comparative Example 1 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that the mass of cobalt phthalocyanine is changed to adjust the mass ratio of cobalt phthalocyanine to graphene oxide, that is, the mass ratio of cobalt phthalocyanine to graphene oxide is 1:2.5.
[0069] Comparative Example 2 Comparative Example 2 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that the mass of cobalt phthalocyanine is changed to adjust the mass ratio of cobalt phthalocyanine to graphene oxide, that is, the mass ratio of cobalt phthalocyanine to graphene oxide is 1:10.
[0070] Comparative Example 3 Comparative Example 3 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that this method studies the effect of doping mode on catalytic activity, changes the raw materials used in the synthesis, and uses deionized water as a solvent, i.e., prepares the material under nitrogen-free doping conditions.
[0071] Comparative Example 4 Comparative Example 4 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that this method studies the effect of doping mode on catalytic activity, changes the raw materials used in synthesis, and does not add cobalt phthalocyanine, i.e., prepares the material under metal-free conditions.
[0072] like Figure 5 As shown, Figure 5 These are X-ray diffraction patterns of five non-high-temperature pyrolysis metal single-atom catalysts used in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. Figure 5 It can be seen that the catalyst synthesized by the preparation method in Example 1 has a more advantageous ratio of various raw materials compared with Comparative Examples 1, 2, 3, and 4. The cobalt metal is supported on the carbon-nitrogen support in the form of single atoms, with more prominent exposure of active sites and greater catalytic potential.
[0073] Comparative Example 5 Comparative Example 5 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that the synthesis temperature is changed, i.e., the solvothermal reaction is carried out at a temperature of 120°C.
[0074] Comparative Example 6 Comparative Example 6 discloses a method for preparing a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that the synthesis temperature is changed, i.e., the solvothermal reaction is carried out at a temperature of 160°C.
[0075] Comparative Example 7 Comparative Example 7 discloses a method for applying a non-high-temperature pyrolysis metal single-atom catalyst. The difference between this method and the method for applying a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that no persulfate is added. That is, Rhodamine B is adsorbed solely by the physical adsorption of the non-high-temperature pyrolysis metal single-atom catalyst.
[0076] Comparative Example 8 Comparative Example 8 discloses an application method for the degradation of Rhodamine B using persulfate. The difference between this method and the application method using a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that no non-high-temperature pyrolysis metal single-atom catalyst is added; that is, persulfate is used alone to degrade Rhodamine B.
[0077] Comparative Example 9 Comparative Example 9 discloses a method for applying a catalyst-activated persulfate degradation method for Rhodamine B. The difference between this method and the method for applying a non-high-temperature pyrolysis metal single-atom catalyst in Example 1 is that the non-high-temperature pyrolysis metal single-atom catalyst is not used. Instead, a raw material containing an active metal that may have catalytic activity is used to activate the persulfate degradation method for Rhodamine B. That is, CoPc is used to activate the persulfate degradation method for Rhodamine B.
[0078] like Figure 6 As shown, Figure 6 This is a comparative performance chart showing the catalytic efficiency of ten different preparation and application methods of non-high-temperature pyrolysis metal single-atom catalysts for the degradation of Rhodamine B by persulfate in Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9. Figure 6 It can be seen that the non-high-temperature pyrolytic metal single-atom catalyst prepared by the method in Example 1 exhibits significantly better catalytic efficiency in the degradation of Rhodamine B using persulfate than the six non-high-temperature pyrolytic catalysts in Comparative Examples 1, 2, 3, 4, 5, and 6. Furthermore, the application method of the non-high-temperature pyrolytic metal single-atom catalyst in Example 1 demonstrates significantly better catalytic efficiency in the degradation of Rhodamine B using persulfate than the three application methods in Comparative Examples 7, 8, and 9.
[0079] The foregoing has provided a detailed description of the non-high-temperature pyrolysis metal single-atom catalyst, its preparation method, and its application method disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the non-high-temperature pyrolysis metal single-atom catalyst, its preparation method, its application method, and its core ideas. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for preparing a non-high-temperature pyrolysis metal single-atom catalyst, characterized in that, The preparation method includes the following steps: S100, Dispersion: Graphene oxide and transition metal compounds are dispersed in amide solvents respectively to obtain graphene oxide dispersion and metal precursor dispersion. S200, Mixing: The graphene oxide dispersion and the metal precursor dispersion are mixed and homogenized under physical field-assisted treatment to obtain a mixed precursor suspension. S300, Solvothermal: The mixed precursor suspension is placed in a closed reaction vessel and subjected to a solvothermal reaction under autogenous pressure and heating conditions. After the reaction is completed, the mixture is cooled to obtain an intermediate product containing metal-graphene hydrogel. S400, Purification and Drying: The intermediate product is washed and purified using a polar solvent, and then vacuum dried to obtain a non-high-temperature pyrolysis metal single-atom catalyst. S500, Grinding: The obtained non-high-temperature pyrolysis metal single-atom catalyst is ground into powder.
2. The preparation method according to claim 1, characterized in that, In step S100, the transition metal compound is one or more of transition metal phthalocyanine compounds, transition metal porphyrin compounds, and transition metal salts.
3. The preparation method according to claim 1, characterized in that, In step S100, the amide solvent is at least one of formamide, N,N-dimethylformamide and N,N-dimethylacetamide.
4. The preparation method according to claim 1, characterized in that, In step S100, the mass ratio of the graphene oxide to the transition metal compound is 2:1 to 10:
1.
5. The preparation method according to claim 1, characterized in that, In step S200, the physical field-assisted treatment is at least one of ultrasonic crushing, ultrasonic dispersion, and mechanical stirring; The homogenization process takes 10 to 60 minutes.
6. The preparation method according to claim 1, characterized in that, In step S300, the temperature of the solvothermal reaction is 160℃~240℃, and the reaction time is 6 hours~24 hours.
7. The preparation method according to claim 1, characterized in that, In step S400, the polar solvent is a mixed solution of ethanol and water; the washing and purification time is more than 3 hours.
8. A non-high-temperature pyrolysis metal single-atom catalyst, prepared by the method for preparing a non-high-temperature pyrolysis metal single-atom catalyst as described in any one of claims 1-7, characterized in that, The catalyst is a non-high-temperature pyrolysis type nitrogen-doped graphene-based supported transition metal single-atom catalyst with a three-dimensional porous structure.
9. A method for applying the non-high-temperature pyrolysis metal single-atom catalyst as described in claim 8, characterized in that, The application method includes: The non-high-temperature pyrolysis metal single-atom catalyst is dispersed in wastewater containing organic pollutants and stirred until the non-high-temperature pyrolysis metal single-atom catalyst and the organic pollutants reach an adsorption-desorption equilibrium state. Then, persulfate is added to degrade the organic pollutants.
10. The application method as described in claim 9, characterized in that, The pH value of the wastewater is 2-14; and / or, The organic pollutants are one or more of the following: organic dyes, antibiotics, organic pesticides, and food additives.
11. The application method as described in claim 9, characterized in that, The mass ratio of the non-high-temperature pyrolysis metal single-atom catalyst to the persulfate is 1:1.5 to 1:16; and / or, The molar ratio of the organic pollutant to the persulfate is 1:1 to 20:1.