A method for preparing a porous interconnected hollow carbon nanofiber membrane
The preparation of porous interconnected hollow carbon nanofiber membranes by coaxial electrospinning and pyrolysis processes has solved the application problem of MOF materials in the field of electrocatalysis, and realized the efficient preparation and low-cost production of self-supporting electrocatalytic membranes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH BEIJING
- Filing Date
- 2023-08-07
- Publication Date
- 2026-07-03
AI Technical Summary
Existing porous MOF materials are solid powders, which makes them difficult to apply widely in membrane catalysis, membrane separation, membrane adsorption and other scenarios. In addition, the use of non-conductive binders reduces the electronic and ionic conductivity, which affects the electrocatalytic performance.
Porous interconnected hollow carbon nanofiber membranes are prepared by mixing MOFs with polymers through coaxial electrospinning and pyrolysis. The MOFs form porous structures on the hollow carbon nanofibers, which are interconnected through hollow channels, thus avoiding the use of adhesives.
The preparation of self-supporting electrocatalytic membranes has been achieved, which improves mechanical properties and conductivity, shortens ion/electron transport paths, reduces production costs, is suitable for large-scale synthesis, and has good application prospects.
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Figure CN117046319B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a method for preparing a porous interconnected hollow carbon nanofiber membrane. Background Technology
[0002] Developing high-porosity non-noble metal-based catalysts is crucial in energy and environmental catalysis. Metal-organic frameworks (MOFs) generally possess excellent porosity, abundant specific surface area, regular channels, tunable pore size, and topological diversity, making them widely studied in energy and environmental fields. However, most MOFs are solid powders, which hinders their widespread application in membrane catalysis, membrane separation, and membrane adsorption. Especially in electrocatalytic membrane processes, powdered catalysts typically require additional non-conductive binders (PVDF, PTFE, and Nafion) and conductive gas diffusion layers (carbon cloth, carbon paper) to ensure complete gas diffusion paths and a catalytic environment. The use of non-conductive binders reduces electron and ion conductivity, as well as mass and charge storage / transport. Therefore, improving electrocatalyst performance requires a synergistic effect between a self-supporting support (increasing conductivity), porous structure, and catalytic active centers. For this reason, constructing binder-free, self-supporting, porous, interconnected hollow carbon nanofiber membranes is of great significance for simplifying electrode construction and promoting the development and application of sustainable energy and environmental technologies.
[0003] Electrospinning is a simple method for manufacturing flexible substrates and an effective way to introduce pores into substrates to prepare functional catalytic materials. Carbon nanofibers typically possess near-nanometer diameters, considerable specific surface areas, good mechanical properties, and excellent electrical conductivity, making them a preferred conductive substrate for supporting electrocatalysts and introducing hierarchical pores. MOF-nanofiber composite electrode materials not only facilitate the uniform dispersion of nanoscale MOFs but also promote electron / ion transfer, and structurally inherit the high surface area of nanofibers and the high catalytic activity of MOF derivatives. Nanofibers effectively act as mass transfer pathways for gas or electrocatalysis, while the fine mesoporous and macroporous structures of carbon nanofibers can accommodate more discharge products and expose abundant catalytic active sites.
[0004] Currently, the preparation of porous interconnected hollow carbon nanofiber membranes mainly involves multi-step synthesis, including a four-step synthetic route: coaxial electrospinning of bilayer nanofibers (core layer and shell nanofibers), in-situ growth of MOFs, organic solvent-assisted removal of the core layer nanofibers, and pyrolysis. This process is complex and costly. Our method mixes MOFs with a core layer solution and achieves the two-step synthesis of porous interconnected hollow carbon nanofiber membranes through coaxial electrospinning and pyrolysis. This is undoubtedly a significant innovation in the field and is of great importance for improving synthesis efficiency. Summary of the Invention
[0005] This invention provides a method for preparing porous interconnected hollow carbon nanofiber membranes. This method is simple to operate, involves straightforward steps, and can be mass-produced, making it of significant practical value in the fields of energy catalysis and environmental protection.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] This method first uses a mixture of MOF and polymer as a shell precursor solution and SAN resin or PMMA as a core layer precursor solution to prepare a hybrid matrix membrane material via coaxial electrospinning and subsequent carbonization. In the hybrid matrix membrane, the SAN resin or PMMA acts as a self-sacrificing template, undergoing carbonization and volatilization to induce the formation of hollow carbon nanofibers. Meanwhile, the MOF induces the formation of porous structures on the hollow carbon nanofibers through interfaces, and these structures are interconnected via hollow channels.
[0008] Specifically, the method includes the following steps:
[0009] S1. Dissolve the metal salt and 2-methylimidazole separately in 95% methanol solution. Quickly pour the obtained 2-methylimidazole methanol solution into the metal salt methanol solution. Stir magnetically at 200-800 r / min for 2 h. After standing for 12 h, centrifuge and filter to obtain a white precipitate. Wash with 95% methanol 3 times and then with water 3 times to obtain MOF.
[0010] S2. Dissolve the polymer, metal salt, and MOF obtained in step S1 together in an organic solvent and magnetically stir at 200-800 r / min for 6-24 h to obtain a shell precursor solution; use SAN resin with a solubility of 15-45% or PMMA with a concentration of 15-45% as a core layer precursor; use the shell precursor solution and the core layer precursor to obtain a mixed matrix film by electrospinning.
[0011] S3. After pre-oxidizing the mixed matrix film obtained in step S2, carbonize it under an Ar or N2 atmosphere to obtain a porous interconnected hollow carbon nanofiber membrane.
[0012] In step S1, the metal ions of the metal salt are one or more of zinc, cobalt, copper, iron, zirconium, manganese, and nickel.
[0013] In step S1, the molar ratio of metal ions to methanol solution in the metal salt is 1:300, and the molar ratio of 2-methylimidazole to methanol solution is 3 to 5:300.
[0014] In step S2, the polymer is one of polyacrylonitrile, polyvinyl alcohol, bacterial cellulose, polyaniline, and polyimide, and the organic solvent is one of dimethylformamide, dimethylacetamide, acetone, benzene, dichloromethane, dimethyl sulfoxide, and ethylene carbonate.
[0015] In step S2, the mass ratio of metal salt to polymer is 1-30:200, the mass ratio of MOF to polymer is 1-2:1-20, and the mass ratio of polymer to organic solvent is 1-2:10-15.
[0016] The electrospinning technical parameters in step S2 are as follows: applied voltage is 13-25kV, feed rate is 1-3:1-2mL / h, receiving distance is 8-20cm, nozzle size is 19-27G, relative humidity is 20-40%, and temperature is 15-40℃.
[0017] In step S3, the pre-oxidation temperature is 250–300°C, and the pre-oxidation atmosphere is air.
[0018] The pre-oxidation time in step S3 is 1 to 3 hours.
[0019] In step S3, the carbonization temperature is 800–1100℃, and the heating rate is 2–5℃ / min.
[0020] The carbonization time in step S3 is 1 to 2 hours.
[0021] The above technical solution has at least the following advantages compared with the existing technology:
[0022] (1) The porous interconnected hollow carbon nanofiber membrane prepared by the method of the present invention is doped with MOF nanoparticles, which ensures that the MOF nanoparticles can bear part of the bending stress, so that the porous interconnected hollow carbon nanofiber has good mechanical properties and can be directly used as a self-supporting electrocatalytic membrane.
[0023] (2) Porous interconnected hollow carbon nanofibers exhibit a one-dimensional network structure with interconnected pores doped with metal active sites. Hollow nanofibers have the advantages of light weight and large internal space, which can not only effectively alleviate the volume expansion during electrocatalysis and enhance structural stability, but also significantly shorten the ion / electron transport path by creating pores on hollow carbon nanofibers. Therefore, porous interconnected hollow carbon nanofibers have great potential in the field of high-performance flexible electrocatalytic energy storage devices.
[0024] (3) This invention develops a simple and easy-to-operate porous interconnected hollow carbon nanofiber membrane that can be prepared in batches, which can effectively reduce production costs, is suitable for large-scale synthesis, and has good application prospects in the field of energy and environmental catalysis. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a process flow diagram of a method for preparing a porous interconnected hollow carbon nanofiber membrane according to the present invention;
[0027] Figure 2 The images shown are SEM images of the porous interconnected hollow carbon nanofiber membranes prepared in the embodiments of the present invention, where (a) is a magnification of 3 μm and (b) is a magnification of 400 nm. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0029] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0030] This invention provides a method for preparing porous interconnected hollow carbon nanofiber membranes.
[0031] This method first uses a mixture of MOF and polymer as a shell precursor solution and SAN resin or PMMA as a core layer precursor solution to prepare a hybrid matrix membrane material via coaxial electrospinning and subsequent carbonization. In the hybrid matrix membrane, the SAN resin or PMMA acts as a self-sacrificing template, undergoing carbonization and volatilization to induce the formation of hollow carbon nanofibers. Meanwhile, the MOF induces the formation of porous structures on the hollow carbon nanofibers through interfaces, and these structures are interconnected via hollow channels.
[0032] like Figure 1 As shown, the method specifically includes the following steps:
[0033] S1. Dissolve the metal salt and 2-methylimidazole separately in 95% methanol solution. Quickly pour the resulting 2-methylimidazole methanol solution into the metal salt methanol solution. Stir magnetically for 2 hours at 200-800 r / min. After standing for 12 hours, centrifuge and filter to obtain a white precipitate. Wash the precipitate three times with 95% methanol and then three times with deionized water to obtain MOF.
[0034] S2. Dissolve the polymer, metal salt, and MOF obtained in step S1 together in an organic solvent and magnetically stir at 200-800 r / min for 6-24 h to obtain a shell precursor solution; use SAN resin with a solubility of 15-45% or PMMA with a concentration of 15-45% as a core layer precursor; use the shell precursor solution and the core layer precursor to obtain a mixed matrix film by electrospinning.
[0035] S3. After pre-oxidizing the mixed matrix film obtained in step S2, carbonize it under an Ar or N2 atmosphere to obtain a porous interconnected hollow carbon nanofiber membrane.
[0036] The following description, in conjunction with specific embodiments, illustrates this point.
[0037] Example 1
[0038] The first step was to prepare metal-organic framework-ZIF-8 nanoparticles.
[0039] Metal salt and 2-methylimidazole were dissolved in 95% methanol solution at molar ratios of 1:300 and 4:300, respectively. The dissolved 2-methylimidazole methanol solution was quickly poured into the metal salt methanol solution, magnetically stirred for 2 hours, and allowed to stand for 12 hours. After centrifugation and filtration, a white precipitate was obtained. The precipitate was washed three times with methanol and water and dried in a constant temperature oven at 100°C for 12 hours to obtain white ZIF-8 nanoparticles.
[0040] The second step is to prepare a Co / Ni-ZIF-8 / SAN resin / PAN nanofiber membrane.
[0041] A shell precursor solution was prepared by stirring a mixture containing 1.2 g ZIF-8 nanocubes, 1.2 g PAN (PAN; MW ~150,000), 150 mg Ni(Ac)₂·4H₂O (purity >99.99%), and 150 mg Co(Ac)₂·4H₂O (purity >99.99%) with 12 mL DMF (N,N-dimethylformimide; purity >99.9%) as solvent. A 25% SAN solution was used as the core layer precursor. Cobalt and nickel-doped ZIF-8 / SAN resin / PAN hybrid matrix films were synthesized under the following conditions: a needle-to-roll receiver distance of 20 cm, a syringe needle of #19, and working voltage, coaxial electrospinning internal and external liquid flow ratio of 17 kV, 2:1, and electrospinning spacing of 12 cm.
[0042] The third step is to prepare a porous interconnected hollow carbon nanofiber membrane doped with bimetallic oxides.
[0043] The hybrid matrix membrane was pre-oxidized in air at 250°C for 1 hour, and then carbonized at 900°C for 1 hour in Ar atmosphere, with a heating rate of 5°C / min. Depending on the specific requirements, this embodiment requires further oxidation at 250°C for 1 hour. Finally, a metal oxide-doped porous interconnected hollow carbon nanofiber membrane was synthesized.
[0044] Example 2
[0045] The first step was to prepare metal-organic framework-ZIF-8 nanoparticles.
[0046] Metal salt and 2-methylimidazole were dissolved in 95% methanol solution at molar ratios of 1:300 and 4:300, respectively. The dissolved 2-methylimidazole methanol solution was quickly poured into the metal salt methanol solution, magnetically stirred for 2 hours, and allowed to stand for 12 hours. After centrifugation and filtration, a white precipitate was obtained. The precipitate was washed three times with methanol and water and dried in a constant temperature oven at 100°C for 12 hours to obtain white ZIF-8 nanoparticles.
[0047] The second step is to prepare a Co-ZIF-8 / SAN resin / PAN nanofiber membrane.
[0048] A shell precursor solution was prepared by stirring a mixture containing 1.5 g ZIF-8 nanocubes, 1.5 g PAN (PAN; MW ~150,000), and 50 mg Co(Ac)₂·4H₂O (purity >99.99%) with 12 mL DMF (N,N-dimethylformimide; purity >99.9%). A 25% SAN solution was used as the core layer precursor. Cobalt-doped ZIF-8 / SAN resin / PAN hybrid matrix films were synthesized under the following conditions: a needle-to-roll receiver distance of 20 cm, a syringe needle of size 19#, and working voltage, coaxial electrospinning internal and external liquid flow ratio of 17 kV, a coaxial electrospinning internal liquid flow ratio of 2:1, and an electrospinning spacing of 12 cm.
[0049] The third step is to prepare a porous interconnected hollow carbon nanofiber membrane anchored by a single metal atom.
[0050] The mixed matrix membrane was pre-oxidized in air at 250°C for 1 hour, and then carbonized at 900°C for 1 hour in Ar atmosphere, with a heating rate of 5°C / min. Depending on the specific requirements, this embodiment requires further immersion in 4.0M H2SO4 aqueous solution overnight to remove cobalt and zinc-derived nanoparticles, ultimately obtaining a porous interconnected hollow carbon nanofiber membrane anchored by metal single atoms.
[0051] The preparation process of this invention is very simple, such as... Figure 1 First, ZIF-8 particles with uniform morphology were obtained through a solvothermal reaction using Zn(NO3)2·6H2O as the metal source, dimethylimidazole as the ligand, and an aqueous solution as the solvent, at a set temperature. Second, a bimetallic oxide-doped porous interconnected hollow carbon nanofiber membrane was prepared using a mixture of ZIF-8 particles, polyacrylonitrile, and Co / Ni metal salt as the shell precursor solution and SAN resin as the core precursor solution via coaxial electrospinning and subsequent carbonization. In the mixed matrix film, the SAN resin acts as a self-sacrificial template to derive the hollow carbon nanofibers, while the ZIF-8 particles form a hollow porous structure during carbonization, creating a porous interconnected structure with the hollow carbon nanofibers. In summary, this invention demonstrates the feasibility of a simple, streamlined, and scalable strategy for preparing porous interconnected hollow carbon nanofibers anchored to metal single atoms.
[0052] like Figure 2 The image shown is a field emission scanning electron microscope (FESEM) image of the fiber membrane prepared in Example 2 of this invention. It indicates that the electrocatalytic membrane exhibits a porous, interconnected hollow carbon nanofiber structure. No obvious short or broken fibers are observed in the morphology; all fibers exhibit an ultra-long, interconnected 1D network structure and are uniformly arranged. Furthermore, it can be seen that almost every nanofiber exhibits a hollow, channel-like structure.
[0053] In summary, the method of this invention enables the indiscriminate preparation of electrocatalytic membranes, ensuring the possibility of large-scale production of hollow materials prepared by coaxial electrospinning in practical applications, and providing a new perspective for the development of flexible devices, electric vehicles, and energy storage devices. This invention has significant application value in the fields of energy and environmental electrocatalysis.
[0054] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing a porous interconnected hollow carbon nanofiber membrane, characterized in that, The steps include the following: S1. Dissolve the metal salt and 2-methylimidazole separately in 95% methanol solution. Quickly pour the resulting 2-methylimidazole methanol solution into the metal salt methanol solution. Stir magnetically at 200~800 r / min for 2 h. After standing for 12 h, centrifuge and filter to obtain a white precipitate. Wash the precipitate three times with 95% methanol and then three times with deionized water to obtain MOF. S2. Dissolve the metal salt, polymer and MOF obtained in step S1 together in an organic solvent, and magnetically stir at 200~800 r / min for 6~24 h to obtain a shell precursor solution; use SAN resin with a concentration of 15~45% or PMMA with a concentration of 15~45% as the core layer precursor. A mixed matrix film was obtained by electrospinning a shell precursor solution and a core precursor. S3. The mixed matrix film obtained in step S2 is pre-oxidized in air at a temperature of 250~300℃, and then carbonized in Ar or N2 atmosphere at a heating rate of 2~5℃ / min and a temperature of 800~1100℃ to obtain a porous interconnected hollow carbon nanofiber membrane. In step S1 and step S2, the metal ions of the metal salt are one or more of nickel and cobalt.
2. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, In step S1, the molar ratio of metal ions to methanol solution in the metal salt is 1:300, and the molar ratio of 2-methylimidazole to methanol solution is (3~5):
300.
3. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, In step S2, the polymer is one of polyacrylonitrile, polyvinyl alcohol, bacterial cellulose, polyaniline, and polyimide, and the organic solvent is one of dimethylformamide, dimethylacetamide, acetone, benzene, dichloromethane, dimethyl sulfoxide, and ethylene carbonate.
4. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, In step S2, the mass ratio of metal salt to polymer is (1~30):200, the mass ratio of MOF to polymer is (1~2):(1~20), and the mass ratio of polymer to organic solvent is (1~2):(10~15).
5. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, The electrospinning technical parameters in step S2 are as follows: applied voltage is 13~25kV, feed rate is (1~3):(1~2)mL / h, receiving distance is 8~20cm, nozzle size is 19~27G, relative humidity is 20~40%, and temperature is 15~40℃.
6. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, The pre-oxidation time in step S3 is 1~3h.
7. The method for preparing a porous interconnected hollow carbon nanofiber membrane according to claim 1, characterized in that, The carbonization time in step S3 is 1~2 hours.