Method for rapidly stabilizing multilevel structure on surface of polymer-derived carbon through transition metal catalysis
By introducing transition metal ions into the polymer and performing rapid heat treatment, the problem of structure collapse of cyano-containing multi-stage structure polymers at high temperatures is solved, and the thermal stability and catalytic performance of highly dispersed metal doped carbon materials are improved.
Patent Information
- Application Number
- CN202510467159.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-15
- Publication Date
- 2025-08-01
AI Technical Summary
Existing cyano-containing monomer polymers are prone to collapse and melt during pyrolysis under high temperature conditions, resulting in multi-stage structural damage and release gas by-products, affecting material stability and performance.
By introducing transition metal ions into cyano-containing multi-stage structure polymers, using metal ions to form coordination bonds with polymer chains, and combining with rapid heat treatment methods, a highly dispersed metal doped carbon material is prepared to maintain the stability and active sites of the multi-stage structure.
Maintaining the integrity of the multi-stage structure under high temperature conditions significantly improves the thermal stability and catalytic properties of the material, especially in oxygen reduction reactions, showing high selectivity and activity.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of materials science and technology, and relates to a method for rapidly and stably constructing a multi-level structure on the surface of polymer-derived carbon through transition metal catalysis. Background Art
[0002] Constructing materials with surface multi-level structures occupies an important position in materials design technology. These structures can significantly improve various properties of materials. The surface multi-level structure refers to a surface structure formed at the nanoscale with multiple levels, pores, or complex geometric morphologies. This structure increases the specific surface area of the material, provides more active sites for catalytic reactions, optimizes the mass transfer path, and improves the contact efficiency between reactants and catalysts. In addition, the multi-level structure helps to improve the mechanical strength, thermal stability, and electrical conductivity of the material, enabling it to remain efficient under extreme conditions. Such materials have shown broad application potential in the fields of energy conversion and storage (such as fuel cells and supercapacitors), environmental governance (such as air purification and wastewater treatment), and biomedicine (such as drug delivery systems and tissue engineering scaffolds). Their unique physical and chemical properties make them key materials for promoting technological progress in these fields.
[0003] Currently, cyano-containing monomers such as cyanoethyl methacrylate, cyanostyrene, acrylonitrile, and copolymers obtained by polymerizing acrylonitrile and acrylic acid are often used to construct surface multi-level structures, but their thermal stability is poor, which greatly limits their application scope and performance. For example, at high temperatures, the molecular chains of PAN (polyacrylonitrile) rich in cyano groups are prone to complex pyrolysis reactions, including dehydrogenation, cyclization, and crosslinking. Without an effective stabilization mechanism, these reactions will cause the collapse or fusion of the PAN structure during heat treatment, thus destroying its original multi-level structure. In addition, unmodified PAN releases a large amount of gaseous by-products during pyrolysis, further exacerbating the structural instability of the material, and it is necessary to reduce the pre-oxidation heating rate to improve the structural stability. Summary of the Invention
[0004] To solve the above technical problems, the present invention proposes a method for rapidly stabilizing the hierarchical structure on the surface of polymer-derived carbon through transition metal catalysis, which improves the thermal stability of the hierarchical structure polymer containing cyano groups and can be applied to different application scenarios by regulating the type and content of the metal. Transition metal ions are introduced into the polymer-derived carbon framework by physical adsorption in the hierarchical structure polymer containing cyano groups and then heat treatment for chemical bonding. The metal ions are used to enhance the stability and conductivity of the polymer chains, thereby optimizing the hierarchical structure on the surface of the obtained carbon-based material. This unique preparation method not only endows the material with a high specific surface area and introduces transition metal elements, but also significantly improves its thermal stability, showing excellent catalytic performance in gas-consuming electrocatalytic reactions: showing a hydrogen peroxide selectivity close to 100% during the ORR (oxygen reduction reaction).
[0005] The technical solution of the present invention is as follows:
[0006] A method for rapidly stabilizing the hierarchical structure on the surface of polymer-derived carbon through transition metal catalysis, comprising the following steps:
[0007] S1: Disperse the hierarchical structure polymer containing cyano groups in a transition metal salt solution and perform water bath stirring, and the water bath temperature is 25 - 70 °C;
[0008] S2: Centrifuge, wash, and dry the dispersion in S1 to obtain a polymer loaded with transition metal;
[0009] S3: Pre-oxidize the polymer loaded with transition metal in an oxygen-containing atmosphere at 200 - 250 °C to obtain a pre-oxidized intermediate;
[0010] S4: Pyrolyze the pre-oxidized intermediate at 600 - 800 °C under inert gas protection to obtain a hierarchical structure polymer-derived carbon material.
[0011] The transition metal includes one or more of Fe, Co, Ni, Cu, and Zn.
[0012] The concentration of the transition metal salt solution is 0.12 - 0.72 mol / L.
[0013] The mass ratio of the hierarchical structure polymer containing cyano groups to the transition metal salt is 1:1 - 3.
[0014] The transition metal salt includes nitrate.
[0015] During the pre-oxidation treatment, the heating rate is 0.1 °C / min - 5 °C / min. Further, the heating rate is 1 °C / min - 5 °C / min.
[0016] The pre-oxidation time is 1 - 3 h.
[0017] During pyrolysis, the heating rate is 5 °C / min - 10 °C / min, and the gas velocity is 50 - 100 mL / min.
[0018] The pyrolysis time is 1 - 5 h.
[0019] The inert gas is argon or nitrogen.
[0020] The cyanide group-containing multi-level structure polymer is obtained by uniformly mixing a cyanide group-containing monomer and an initiator to obtain a prepolymer solution, and subjecting the prepolymer solution to constant-temperature polymerization and drying.
[0021] Specifically, it includes the following steps:
[0022] S1: Take 5 - 150 ml of the cyanide group-containing monomer and 5 - 150 mg of the initiator and mix them evenly to obtain a prepolymer solution;
[0023] S2: Place the prepolymer solution in a reaction kettle and introduce an inert gas to displace the air;
[0024] S3: React the displaced prepolymer solution at 50 - 90 °C for 1 - 5 h for heat preservation polymerization;
[0025] S4: Place the polymer obtained in S3 in a vacuum oven, evacuate and dry it for 6 - 12 h, and the drying temperature is 50 - 70 °C to obtain a polymer with a flower-like structure.
[0026] The prepolymer solution also includes an organic solvent, and the organic solvent is acetone, ethanol, acetonitrile, methanol, dimethylformamide, acetic acid or tetrahydrofuran.
[0027] The dosage of the organic solvent is 5 - 150 ml.
[0028] The beneficial effects of the present invention are:
[0029] (1) The transition metal catalyzes the cyclization coordination process, quickly stabilizing its original multi-level structure. During pyrolysis, the coordination bond formed between the transition metal and the cyanide group in the polymer chain can effectively reduce the heat generated by the cyclization reaction, thus avoiding the occurrence of local overheating. This heat management during pyrolysis is crucial for maintaining the structural integrity of the material, preventing the collapse and fusion of the cyanide group-containing monomer under high-temperature conditions. Through the participation of the transition metal, the structural thermal stability is effectively improved, and the multi-level structure can still be maintained after rapid high-temperature pyrolysis treatment, and the pre-oxidation heating time is shortened from 2000 min or even longer to 40 min.
[0030] (2) In the present invention, transition metals are introduced at the polymer stage, followed by heat treatment, successfully preparing highly dispersed metal-doped carbon materials. This preparation method not only ensures the uniform distribution of transition metals in the carbon matrix but also significantly enhances the structural stability of the material and the number of active sites due to its transition metal-N coordination structure. Through rotating ring-disk electrode testing (RRDE) in alkaline electrolyte, it exhibits a H2O2 selectivity close to 100%, indicating that this material shows excellent catalytic performance in gas-consuming electrocatalytic reactions. Description of the Drawings
[0031] Figure 1 Scanning electron microscope images of the metal nickel-doped hierarchical carbon spheres Ni-FCS-1 and Ni-FCS-5 prepared in Example 1;
[0032] Figure 2 Scanning electron microscope image of the metal iron-doped hierarchical carbon sphere Fe-FCS prepared in Example 2;
[0033] Figure 3 a-c are scanning electron microscope images of polymers with surface hierarchical structures prepared in Comparative Example 1 and Solvents 4-5; d-f are scanning electron microscope images of carbon spheres prepared in Comparative Example 1 and Solvents 4-5; g-i are scanning electron microscope images of metal nickel-doped hierarchical carbon spheres prepared in Example 1 and Solvents 3-4.
[0034] Figure 4 Scanning electron microscope image of the metal-free doped smooth carbon sphere SCS prepared in Comparative Example 2;
[0035] Figure 5 Scanning electron microscope image of the carbon sphere NiNPs-FCS with metal nanoclusters prepared in Comparative Example 3;
[0036] Figure 6 X-ray diffraction patterns (XRD) of Examples 1-2 and Comparative Examples 1-2;
[0037] Figure 7 XPS N1s spectra of Example 1 Ni-FCS-1 and Comparative Example 1;
[0038] Figure 8 X-ray diffraction pattern of the carbon material prepared in Comparative Example 3;
[0039] Figure 9 Double-layer capacitances of the carbon materials prepared in Example 1 and Comparative Examples 1-2;
[0040] Figure 10 Two-electron oxygen reduction selectivity curves of the carbon materials prepared in Example 1 and Comparative Examples 1-2. Specific Embodiments
[0041] The above content of the present invention will be further described in detail through the following embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments. All technologies implemented based on the above content of the present invention belong to the scope of the present invention.
[0042] Example 1
[0043] (Preparation of Ni-FCS-1 and Ni-FCS-5)
[0044] Step S1: Mix 5 ml of acrylonitrile, 5 ml of acetone, and 5 mg of azobisisobutyronitrile evenly to obtain a prepolymer solution.
[0045] Step S2: Add the prepolymer solution in S1 to a 20 ml glass reaction flask with a filling degree of 50%, and place it in a reaction kettle.
[0046] Step S3: Replace the air in the reaction kettle with argon, perform multiple pressurization and deflation, and heat up to 70 °C and keep it for 2 h to obtain a polymer.
[0047] Step S4: Vacuum dry the polymer obtained in S3 at a drying temperature of 50 °C.
[0048] Step S5: Place 1 g of the polymer obtained in S4 into 100 ml of 0.24 M nickel nitrate solution, stir in a water bath at 50 °C for 12 h, and after centrifugation, washing with water and drying, obtain a polymer supported with Ni.
[0049] Step S6: Pre-oxidize the polymer supported with Ni in an air atmosphere by heating it to 230 °C at a rate of 1 °C / min for 1 h (the heating process takes 200 min), and then heat it to 800 °C at a rate of 5 °C / min in argon and keep it for 2 h to obtain Ni-FCS-1; or pre-oxidize the polymer supported with Ni in an air atmosphere by heating it to 230 °C at a rate of 5 °C / min for 1 h (the heating process takes 40 min), and then heat it to 800 °C at a rate of 5 °C / min in argon and keep it for 2 h to obtain Ni-FCS-5.
[0050] Example 2
[0051] (Preparation of Fe-FCS)
[0052] Step S1: Mix 5 ml of acrylonitrile, 5 ml of acetone, and 5 mg of azobisisobutyronitrile evenly to obtain a prepolymer solution.
[0053] Step S2: Add the prepolymer solution in S1 to a 20 ml glass reaction flask with a filling degree of 50%, and place it in a reaction kettle.
[0054] Step S3: Replace the air in the reaction kettle with argon, perform multiple pressurization and deflation, and heat up to 70 °C and keep it for 2 h to obtain a polymer.
[0055] Step S4: Vacuum dry the polymer obtained in S3 at a drying temperature of 50°C;
[0056] Step S5: Place 1 g of the polymer obtained in S4 into 100 ml of 0.24 M iron nitrate solution, stir in a water bath at 50°C for 12 h, and after centrifugation, washing with water and drying, obtain the polymer loaded with Fe;
[0057] Step S6: Heat the polymer loaded with Fe in an air atmosphere from room temperature to 230°C at a rate of 1°C / min for pre-oxidation for 1 h (the heating process takes 200 min), and then heat it to 800°C at a rate of 5°C / min in argon and hold for 2 h to obtain Fe-FCS.
[0058] Example 3
[0059] Same as Example 1, but replace acetone with acetonitrile, and the pre-oxidation heating rate is 1°C / min to obtain Ni-FCS-Acetonitrile.
[0060] Example 4
[0061] Same as Example 1, but without adding acetone solvent, and the pre-oxidation heating rate is 1°C / min to obtain Ni-FCS-Solventfree.
[0062] Comparative Example 1
[0063] (Preparation of FCS)
[0064] Step S1: Mix 5 ml of acrylonitrile, 5 ml of acetone, and 5 mg of azobisisobutyronitrile evenly to obtain a prepolymer solution;
[0065] Step S2: Add the prepolymer solution to a 20 ml glass reaction bottle with a filling degree of 50%, and place it in a reaction kettle;
[0066] Step S3: Replace the air in the reaction kettle with argon, perform multiple pressurization and deflation, heat to 70°C and hold for 2 h to obtain a polymer;
[0067] Step S4: Vacuum dry the polymer obtained in S3 at a drying temperature of 50°C;
[0068] Step S5: Heat the polymer in S4 in an air atmosphere from room temperature to 230°C at a rate of 0.1°C / min for pre-oxidation for 1 h (the heating process takes 2000 min), and then heat it to 800°C at a rate of 5°C / min in argon and hold for 2 h to obtain FCS.
[0069] Comparative Example 2
[0070] (Preparation of SCS)
[0071] Same as Comparative Example 1, but the pre-oxidation rate is 1°C / min to obtain SCS.
[0072] Comparative Example 3
[0073] (Preparation of NiNPs-FCS)
[0074] Step S1: Mix 5 ml of acrylonitrile, 5 ml of acetone, 5 mg of azobisisobutyronitrile, and 0.7 g of nickel nitrate evenly to obtain a prepolymer solution;
[0075] Step S2: Add the prepolymer solution to a 20 ml glass reaction flask with a filling degree of 50%, and place it in a reaction kettle; Step S3: Replace the air in the reaction kettle with argon, perform multiple pressurization and deflation operations, and heat up to 70 °C and keep it warm for 2 h to obtain a polymer;
[0076] Step S4: Vacuum-dry the polymer obtained in S3 at a drying temperature of 50 °C;
[0077] Step S5: Heat the polymer in Step 4 to 230 °C at a rate of 1 °C / min in an air atmosphere and pre-oxidize it for 1 h (the heating process takes 200 min), and then heat it to 800 °C at a rate of 5 °C / min in argon and keep it for 2 h to obtain NiNPs-FCS.
[0078] Comparative Example 4
[0079] (Preparation of SCS-Acetonitrile)
[0080] Same as Comparative Example 1, but replace acetone with acetonitrile to obtain SCS-Acetonitrile.
[0081] Comparative Example 5
[0082] (Preparation of SCS-Solvent free)
[0083] Same as Comparative Example 1, but do not add acetone solvent to obtain SCS-Solvent free.
[0084] Result analysis:
[0085] Figure 1-2 They are the scanning electron microscope results of the carbon spheres prepared in Examples 1-2. The diameters of the carbon spheres Ni-FCS-1, Ni-FCS-5, and Fe-FCS with a hierarchical structure after metal doping are 700 nm, and no metal agglomeration is observed.
[0086] Figure 3SEM images of FCS, SCS-Acetonitrile, and SCS-Solvent free prepared in Comparative Examples 1, 4 - 5, and Ni-FCS-1, Ni-FCS-Acetonitrile, and Ni-FCS-Solvent free prepared in Examples 1, 3 - 4. When no metal is doped, the materials synthesized with acetonitrile and solvent-free degrade into a smooth structure after pre-oxidation at 0.1 °C / min, while after doping with metal elements, carbon spheres with a hierarchical structure are obtained after pre-oxidation at 1 °C / min. Not only is the hierarchical structure retained, but the pre-oxidation heating time is significantly shortened.
[0087] Figure 4 SEM image of SCS prepared in Comparative Example 2. The morphology of the polyacrylonitrile carbon spheres without added metal degrades after pre-oxidation at 1 °C / min.
[0088] Figure 5 SEM image of NiNPs-FCS prepared in Comparative Example 3. Introducing metal during the polymerization stage causes metal agglomeration during the pyrolysis process, resulting in the appearance of metal nanoparticles and a slightly degraded morphology.
[0089] Figure 6 XRD results of Examples 1 - 2 and Comparative Examples 1 - 2. After metal doping, no metal diffraction peaks are observed, and the transition metal exists in a highly dispersed form in the carbon spheres.
[0090] Figure 7 N fine spectrum of X-ray photoelectron spectroscopy of Ni-FCS-1 in Example 1 and Comparative Example 1. After metal doping, Ni-N coordination bonds exist.
[0091] Figure 8 XRD results of NiNPs-FCS prepared in Comparative Example 3. The results show that this material has obvious metal diffraction peaks.
[0092] Table 1 shows the cyclization rate and aromatization degree of Examples 1 and Comparative Examples 1 - 2 during the pre-oxidation stage. The aromatization degree directly proves the structural stability of the pre-oxidation product.
[0093] Table 1 Cyclization rate and aromatization degree of Examples 1 and Comparative Examples 1 - 2 during the pre-oxidation stage
[0094]
[0095] Application Example 1
[0096] Using a rotating ring-disk electrode, the carbon spheres of Example 1 and Comparative Examples 1-2 were used in the electrocatalytic oxygen reduction reaction for the synthesis of hydrogen peroxide. The reaction conditions were as follows: the electrolyte used for testing was 0.1 mol / L KOH solution, the rotation speed of the rotating ring-disk electrode was 1600 RPM, and the test was carried out under oxygen-saturated conditions.
[0097] From Figure 9 , Figure 10 the double-layer capacitance and two-electron oxygen reduction selectivity curves of, it can be clearly seen that the metal-doped hierarchical carbon spheres have significant advantages over the smooth spherical carbon spheres in many aspects. First, in the double-layer capacitance test graph ( Figure 9 ), it is shown that the metal-doped hierarchical carbon sphere Ni-FSC-1 has an electrochemical specific surface area ten times that of the smooth sphere SCS. This greatly increased surface area significantly promotes the mass transfer and diffusion process, enabling oxygen and the electrolyte to more efficiently contact the active sites and helping to improve the accessibility of the active centers, thus significantly enhancing the overall efficiency of the oxygen reduction reaction (ORR). The metal doping introduces new active sites, which not only increase the reaction density on the surface of the carbon spheres but also optimize the electronic structure and improve the selectivity for the target product. Especially in the two-electron oxygen reduction selectivity curve, it can be seen that the flower-like carbon spheres after metal doping have a significant improvement in the selectivity for generating hydrogen peroxide, and Ni-FCS-1 has a nearly ideal H2O2 100% selectivity ( Figure 10 ), which proves their superior performance in promoting the two-electron transfer path rather than the four-electron path.
Claims
1. A method for rapidly stabilizing a multi-level structure on the surface of polymer-derived carbon by transition metal catalysis, characterized in that: It includes the following steps: S1: Disperse the cyanide-containing multi-stage structure polymer in a transition metal salt solution and stir it in a water bath at a water bath temperature of 25 - 70 °C; S2: Centrifuge, wash, and dry the dispersion in S1 to obtain a polymer loaded with a transition metal; S3: Pre-oxidize the polymer loaded with a transition metal in an oxygen-containing atmosphere at 200 - 250 °C to obtain a pre-oxidized intermediate; S4: Pyrolyze the pre-oxidized intermediate at 600 - 800 °C under the protection of an inert gas to obtain a multi-stage structure polymer-derived carbon material.
2. A method for rapidly and stably constructing a hierarchical structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: The transition metal includes one or more of Fe, Co, Ni, Cu, and Zn.
3. A method for rapidly and stably constructing a hierarchical structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: The concentration of the transition metal salt solution is 0.12 - 0.72 mol / L.
4. A method for rapidly and stably fabricating a multi-level structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: The mass ratio of the cyanide-containing multi-stage structure polymer to the transition metal salt is 1:1 - 3.
5. A method for rapidly and stably constructing a multi-level structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: During pre-oxidation, the heating rate is 0.1 °C / min - 5 °C / min.
6. A method for rapidly and stably constructing a hierarchical structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: The pre-oxidation time is 1 - 3 h.
7. A method for rapidly and stably deriving a multi-level structure on the surface of a polymer-derived carbon by transition metal catalysis according to claim 1, characterized in that: During pyrolysis, the heating rate is 5 - 10 °C / min and the gas flow rate is 50 - 100 mL / min.
8. A method for rapidly and stably forming a multi-level structure on the surface of polymer-derived carbon by transition metal catalysis as described in claim 1, characterized in that: The cyanide-containing multi-stage structure polymer is obtained by uniformly mixing a cyanide-containing monomer and an initiator to obtain a prepolymer solution, and subjecting the prepolymer solution to constant-temperature polymerization and drying.
9. A method for rapidly and stably forming a hierarchical structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 8, characterized in that: The prepolymer solution further includes an organic solvent.
10. A method for rapidly and stably constructing a hierarchical structure on the surface of polymer-derived carbon by transition metal catalysis according to claim 9, characterized in that: The organic solvent is acetone, ethanol, acetonitrile, methanol, dimethylformamide, acetic acid, or tetrahydrofuran.