阅读说明：本技术 内管壁负载氧化锡的中空多孔碳纳米纤维及其制备方法和应用 (Hollow porous carbon nanofiber with tin oxide loaded on inner tube wall and preparation method and application thereof ) 是由 孔方圆 辛斌杰 刘毅 余淼 沈冬冬 于文杰 罗健 袁秀文 于 2021-07-05 设计创作，主要内容包括：本发明提供了一种内管壁负载氧化锡的中空多孔碳纳米纤维及其制备方法和应用,制备方法包括：将聚丙烯腈、聚甲基丙烯酸甲酯和聚乙烯吡咯烷酮混合后得到壳层纺丝溶液；将聚乙烯吡咯烷酮和二水氯化亚锡溶解得到芯层纺丝溶液；将壳层纺丝溶液、芯层纺丝溶液同轴静电纺丝,得到碳纤维前驱体；进行预氧化和碳化处理,得到内管壁负载氧化锡的中空多孔碳纳米纤维；与传统方法制得的多孔碳纳米纤维相比,将氧化锡与碳纤维结合形成网络骨架,不仅使碳纤维具有更多的活性位点和更高的比电容,同时其可控的离子、电子传输通道提高了氧化锡储存电荷的稳定性和高效性,制备的中空多孔碳纳米纤维可应用于锂电池及超级电容器等方面。(The invention provides a hollow porous carbon nanofiber with tin oxide loaded on an inner tube wall, and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing polyacrylonitrile, polymethyl methacrylate and polyvinylpyrrolidone to obtain a shell spinning solution; dissolving polyvinylpyrrolidone and stannous chloride dihydrate to obtain a core layer spinning solution; carrying out coaxial electrostatic spinning on the shell layer spinning solution and the core layer spinning solution to obtain a carbon fiber precursor; carrying out pre-oxidation and carbonization treatment to obtain hollow porous carbon nanofiber with tin oxide loaded on the inner pipe wall; compared with the porous carbon nanofiber prepared by the traditional method, the tin oxide and the carbon fiber are combined to form a network skeleton, so that the carbon fiber has more active sites and higher specific capacitance, and the controllable ion and electron transmission channel of the carbon fiber improves the stability and high efficiency of the charge stored by the tin oxide.)

1. A preparation method of hollow porous carbon nanofiber with tin oxide loaded on inner tube wall is characterized by comprising the following steps: which comprises the following steps:

(1) dissolving polyacrylonitrile, polymethyl methacrylate and polyvinylpyrrolidone in an organic solvent, and stirring at room temperature to obtain a first spinning solution;

(2) dissolving polyvinylpyrrolidone and stannous chloride dihydrate in a mixed solvent of ethanol and an organic solvent to obtain a second spinning solution;

(3) performing coaxial electrostatic spinning by using the first spinning solution as a shell layer solution and the second spinning solution as a core layer solution to obtain a carbon fiber precursor;

(4) pre-oxidizing the carbon fiber precursor to obtain pre-oxidized polymethyl methacrylate/polyvinylpyrrolidone/polyacrylonitrile nano fiber containing tin oxide nano particles;

(5) and carrying out high-temperature carbonization treatment on the preoxidized polymethyl methacrylate/polyvinylpyrrolidone/polyacrylonitrile nanofiber in a nitrogen atmosphere to obtain the hollow porous carbon nanofiber with the inner pipe wall loaded with tin oxide.

2. The method of claim 1, wherein: in the step (1) and the step (2), the organic solvent is one or more selected from the group consisting of N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetone, tetrahydrofuran, and chloroform.

3. The method of claim 1, wherein: in the step (1), the mass of the organic solvent is 10-20g, the mass of polyacrylonitrile is 1.2-3.2g, the mass of polymethyl methacrylate is 5-60 wt% of polyacrylonitrile, and the mass of polyvinylpyrrolidone is 5-20 wt% of polyacrylonitrile.

4. The method of claim 1, wherein: in the step (2), the mass of the organic solvent is 10-20g, the mass of the ethanol is 1-2g, the mass of the polyvinylpyrrolidone is 1.2-3.2g, and the mass of the stannous chloride dihydrate is 5-25 wt% of the polyvinylpyrrolidone.

5. The method of claim 1, wherein: in the step (3), the electrostatic spinning process parameters are as follows: the coaxial spinning head consists of a No. 16 outer capillary tube and a No. 21 inner capillary tube, the spinning voltage is 15-20kV, the feeding speeds of the core layer solution and the shell layer solution are both 1.0-1.5mL/h, and the receiving distance is 15-20 cm.

6. The method of claim 1, wherein: in the step (4), the temperature rise rate of the pre-oxidation is 1-5 ℃/min, the temperature of the pre-oxidation is 200-300 ℃, and the time of the pre-oxidation is 2-4 h.

7. The method of claim 1, wherein: in the step (5), the temperature rise rate of the high-temperature carbonization is 5-10 ℃/min, the carbonization temperature is 800-1000 ℃, and the carbonization time is 2-4 h.

8. A hollow porous carbon nanofiber with tin oxide loaded on the inner tube wall is characterized in that: which is obtained by the production method according to any one of claims 1 to 7.

9. The hollow porous carbon nanofiber supporting tin oxide on the inner tube wall as recited in claim 8, wherein: the surface of the hollow porous carbon nanofiber comprises mesopores and micropores, the aperture of the hollow pipeline is 100-200nm, the aperture of the mesopores is 2-50nm, and the aperture of the micropores is smaller than 2 nm.

10. Use of the hollow porous carbon nanofiber with tin oxide loaded inner tube wall as claimed in claim 8 in batteries and capacitors.

Technical Field

The invention belongs to the technical field of novel porous carbon nanofiber, and particularly relates to hollow porous carbon nanofiber with tin oxide loaded on an inner tube wall, and a preparation method and application thereof.

Background

The carbon-based flexible porous carbon nanofiber material is an important fiber material, and particularly has important application in the field of new energy. The preparation of the polyacrylonitrile-based carbon nanofiber by electrostatic spinning is a simple and convenient method for preparing the carbon-based flexible porous carbon nanofiber material, and has the advantages of simple operation, low cost, easy adjustment of the product structure and the like. The polyacrylonitrile-based carbon nanofiber prepared by the method has the advantages of three-dimensional structure, high porosity, high specific surface area, high conductivity, high storage performance and the like, and is widely applied to the fields of catalyst carrier materials, supercapacitor electrode materials, lithium ion batteries and the like.

As a derivative of the carbon nanofiber, the hollow porous carbon nanofiber can greatly improve the specific surface area of the carbon nanofiber, and can optimize the problems of single structure and the like of the traditional carbon nanofiber, so that the electrochemical performance and the adsorption performance of the material are improved. The existing methods for preparing the porous carbon nanofiber can be divided into two categories, one is to prepare the carbon nanofiber firstly, then react with a substrate fiber by using an etching agent such as potassium hydroxide, carbon dioxide and plasma to consume carbon and generate holes; the other method is to blend the polymer substrate with pore-forming agent such as polyvinylpyrrolidone, sodium bicarbonate and metal oxide, and then the pore-forming agent is consumed in the subsequent carbonization process or removed by post-treatment after the carbonization is completed, so as to form pores at the original occupied positions. In comparison, the second method is simpler to operate and can utilize different pore formers to adjust the pore structure.

Tin oxide is a novel high-capacity electrochemical material, and is widely concerned by people due to low toxicity, high theoretical specific capacity and lower lithium intercalation potential, and is praised as an ideal lithium ion battery cathode material and a capacitor electrode material. However, agglomeration and pulverization are caused by repeated de-intercalation of ions during the cycle and the volume of tin oxide is easily expanded, and its low energy density and interfacial instability during the cycle hinder its practical application. Therefore, combining tin oxide with carbon fiber to form a network skeleton, thereby improving the cycle performance of tin oxide is a research hotspot at present.

Disclosure of Invention

Aiming at the defects in the prior art, the primary object of the invention is to provide a preparation method of hollow porous carbon nanofiber with tin oxide loaded on the inner tube wall.

It is a second object of the present invention to provide the above hollow porous carbon nanofiber. Namely, the carbon nanofiber has a hierarchical pore and hollow inner tube wall loaded tin oxide structure and has efficient and stable electrochemical performance.

A third object of the present invention is to provide the use of the hollow porous carbon nanofiber as described above.

In order to achieve the above primary object, the solution of the present invention is:

a preparation method of hollow porous carbon nanofiber with tin oxide loaded on inner tube wall comprises the following steps:

(1) dissolving polyacrylonitrile, polymethyl methacrylate and polyvinylpyrrolidone in an organic solvent, and stirring at room temperature to obtain a first spinning solution (namely a shell spinning solution);

(2) dissolving polyvinylpyrrolidone and stannous chloride dihydrate in a mixed solvent of ethanol and an organic solvent to obtain a second spinning solution (namely a core layer spinning solution);

(3) carrying out coaxial electrostatic spinning by taking the first spinning solution as a shell layer solution and the second spinning solution as a core layer solution to obtain a carbon fiber precursor;

(4) pre-oxidizing a carbon fiber precursor in air through a muffle furnace to obtain pre-oxidized polymethyl methacrylate/polyvinylpyrrolidone/polyacrylonitrile nano-fiber containing tin oxide nano-particles;

(5) and (3) carbonizing the preoxidized polymethyl methacrylate/polyvinylpyrrolidone/polyacrylonitrile nano fiber at a high temperature in a nitrogen atmosphere to obtain the hollow porous carbon nano fiber with the inner pipe wall loaded with tin oxide.

In a preferred embodiment of the present invention, in the step (1) and the step (2), the organic solvent is at least one selected from the group consisting of N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetone, tetrahydrofuran and chloroform.

As a preferred embodiment of the present invention, in the step (1), the mass of the organic solvent is 10 to 20g, the mass of polyacrylonitrile is 1.2 to 3.2g, the mass of polymethyl methacrylate is 5 to 60 wt% of polyacrylonitrile, and the mass of polyvinylpyrrolidone is 5 to 20 wt% of polyacrylonitrile.

As a preferred embodiment of the present invention, in the step (2), the mass of the organic solvent is 10 to 20g, the mass of the ethanol is 1 to 2g, the mass of the polyvinylpyrrolidone is 1.2 to 3.2g, and the mass of the stannous chloride dihydrate is 5 to 25 wt% of the polyvinylpyrrolidone.

As a preferred embodiment of the present invention, in step (3), the process parameters of electrostatic spinning are as follows: the spinning solution container is a 5mL injector, the coaxial spinning head consists of a No. 16 outer capillary tube and a No. 21 inner capillary tube, the spinning voltage is 15-20kV, the feeding speeds of the core layer solution and the shell layer solution are both 1.0-1.5mL/h, and the receiving distance is 15-20 cm.

As a preferred embodiment of the present invention, in the step (4), the temperature rise rate of the pre-oxidation is 1-5 ℃/min, the temperature of the pre-oxidation is 200-300 ℃, and the time of the pre-oxidation is 2-4 h.

As a preferred embodiment of the present invention, in the step (5), the temperature rise rate of the high temperature carbonization is 5-10 ℃/min, the carbonization temperature is 800-1000 ℃, and the carbonization time is 2-4 h.

In order to achieve the second objective, the solution of the invention is:

the hollow porous carbon nanofiber with the inner tube wall loaded with tin oxide is prepared by the preparation method. Namely, the structure of the inner pipe wall loaded with tin oxide is that stannous chloride dihydrate is blended with polyvinylpyrrolidone, polyvinylpyrrolidone is decomposed after carbonization, and a small amount of residues of the structure are used as an adhesive to fix the tin oxide on the inner pipe wall while a hollow structure is formed.

The tin oxide is prepared by taking tin chloride as a tin precursor and converting the tin chloride into tin oxide after preoxidation treatment.

As a preferred embodiment of the invention, the surface of the hollow porous carbon nanofiber comprises mesopores and micropores, the pore diameter of the hollow pipeline is 100-200nm, the pore diameter of the mesopores is 2-50nm, and the pore diameter of the micropores is less than 2 nm.

Wherein, the pores can be formed by the pyrolysis of polymethyl methacrylate, polystyrene, benzoxazine and the like, and the micropores can be formed by the pyrolysis of polyvinylpyrrolidone, phenol-formaldehyde novolac resin, cyclodextrin and the like.

In summary, the hollow porous carbon nanofiber material with tin oxide loaded on the inner tube wall provided by the invention has hollow and porous structural morphology with tin oxide loaded on the inner tube, and is characterized in that the fiber with a core-shell structure is spun through coaxial electrostatic spinning, tin chloride is converted into tin oxide in the pre-oxidation process, then the tin oxide is carbonized at high temperature, polyvinylpyrrolidone is pyrolyzed to form a hollow pore channel, tin oxide is solidified on the inner tube wall by residues of the hollow pore channel, and the polymethyl methacrylate and the polyvinylpyrrolidone form mesopores and micropores on the surface of the fiber respectively, so that the hollow porous carbon nanofiber material with tin oxide loaded on the tube wall is obtained.

The porous structure of the hollow porous carbon nanofiber has the following advantages: the pipeline is provided with longitudinal holes parallel to the fiber direction, the diameter is about 50-150nm, and the specific surface area of the carbon fiber is greatly increased; secondly, due to the fact that the surfaces and the inner carbon walls of the carbon fibers are formed with mesopores and micropores through pyrolysis of the polymethyl methacrylate and the polyvinylpyrrolidone, adsorption and storage capacity of the surfaces of the carbon fibers to charges in an electrolyte is greatly enhanced, and changes of the volumes of the carbon fibers in the charging and discharging processes can be effectively buffered; and thirdly, the tin oxide is ingeniously loaded on the wall of the hollow inner tube, so that the flow and the speed of the electrolyte flowing into the hollow channel can be limited, the transmission path of lithium ions and electrons is shortened by the channeled carbon nanofiber, the impact and stripping effect of the electrolyte on the tin oxide are reduced, the efficient and stable electrochemical performance is favorably kept, and the composite material can be used as novel functional materials such as battery electrodes, supercapacitor electrode materials and the like.

In order to achieve the third object, the solution of the invention is:

the hollow porous carbon nanofiber with the tin oxide loaded on the inner tube wall is applied to the battery and capacitor electrodes.

Specifically, the characteristic of low polyvinylpyrrolidone conversion rate is utilized, the hollow pore channel is formed by pyrolysis at high temperature, tin oxide is adhered to the wall of the hollow pore channel by the residue of the hollow pore channel, and then the characteristic that polymethyl methacrylate and polyvinylpyrrolidone are mutually insoluble with polyacrylonitrile polymer is utilized, and polymethyl methacrylate and polyvinylpyrrolidone are selected and used as pore-forming agents of mesopores and micropores respectively, so that a layered pore structure is formed on the surface. Firstly, a core-shell nanofiber membrane is prepared by adopting a coaxial electrostatic spinning method, then the conversion of tin chloride to tin oxide is realized in the pre-oxidation process, and the conversion of carbon fibers and the generation of a pore structure are completed in one step in the high-temperature carbonization process, so that the complex post-treatment process is avoided. The diameter of the nanofiber is regulated and controlled by the size of the coaxial electrospinning spinneret and the content of PVP (polyvinyl pyrrolidone), the obtained hollow porous carbon nanofiber has adjustable diameter and pore structure, and the hollow characteristic of the hollow porous carbon nanofiber endows the hollow porous carbon nanofiber with a specific electrolyte transmission channel, so that the hollow porous carbon nanofiber is an ideal conductive substrate and can be used as a novel functional material such as a battery electrode material and a supercapacitor electrode material.

Due to the adoption of the scheme, the invention has the beneficial effects that:

firstly, the carbon nanofiber with the hollow porous structure greatly increases the specific surface area of the carbon fiber, and enhances the adsorption and storage capacity of the carbon nanofiber on charges in an electrolyte.

Secondly, the method of loading tin oxide on the hollow porous carbon nanofiber is utilized, metal oxide is loaded on the inner tube wall of the hollow channel, and the nano-scale electrolyte transmission channel limits the volume expansion of tin oxide in the ion circulation process, so that the service life and the service efficiency of tin oxide are improved.

Drawings

Fig. 1 is a flow chart of a process for preparing a hollow porous carbon nanofiber with tin oxide supported on an inner tube wall in various embodiments of the present invention.

Fig. 2 is a schematic diagram of capacitance stability of the hollow porous carbon nanofiber with tin oxide loaded on the inner tube wall in example 1 under 10000 cycles.

Fig. 3 is a schematic diagram of capacitance stability of the hollow porous carbon nanofiber with tin oxide loaded on the inner tube wall in example 2 of the invention under 10000 cycles.

Fig. 4 is a schematic diagram of capacitance stability of the hollow porous carbon nanofiber with tin oxide loaded on the inner tube wall in example 3 of the invention under 10000 cycles.

Detailed Description

The invention provides a hollow porous carbon nanofiber with tin oxide loaded on an inner tube wall, and a preparation method and application thereof.

The present invention will be further described with reference to the following examples.

Example 1:

as shown in fig. 1, the preparation method of the hollow porous carbon nanofiber with tin oxide supported on the inner tube wall in the embodiment includes the following steps:

(1) mixing 1.4g of Polyacrylonitrile (PAN), 0.5g of polymethyl methacrylate (PMMA) and 0.2g of polyvinylpyrrolidone (PVP), adding the mixture into 17.6g of N, N-dimethylformamide, stirring for 6 hours, and performing ultrasonic treatment for 4 hours to prepare a shell spinning solution.

(2) 2.2g of polyvinylpyrrolidone and 0.2g of stannous chloride dihydrate (SnCl)₂·2H₂O) and then adding the mixture into a mixed solvent of 1g of ethanol and 17.6g of N, N-dimethylformamide, stirring for 6 hours and carrying out ultrasonic treatment for 4 hours to prepare a core layer spinning solution.

(3) Respectively injecting the prepared shell layer spinning solution and the prepared core layer spinning solution into a 5mL injector with a coaxial needle head of 16G/21G, and carrying out coaxial electrostatic spinning under the spinning voltage of 20kV to obtain a carbon fiber precursor; wherein the feeding speed of the spinning process is 1.5mL/h, and the receiving distance is 15 cm.

(4) And raising the temperature of the prepared carbon fiber precursor to 250 ℃ in air at a heating rate of 2 ℃/min for pre-oxidation for 2 h.

(5) And putting the pre-oxidized nanofiber membrane into a tubular furnace, and raising the temperature to 1000 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere for carbonization for 2 hours. And (3) cooling the temperature of the tube furnace to room temperature to obtain the hollow porous carbon nanofiber with the inner tube wall loaded with tin oxide, wherein the material is marked as HPCNF-1. The tin oxide of the component material has strong effect, can be uniformly dispersed on the wall of the hollow pipe, and has the specific surface area of 23.6cm²The specific capacitance is up to 1352.6F/g under the current density of 1A/g, and the electrode material is assembled into a super capacitor, as shown in figure 2, the super capacitor shows excellent cycling stability after 10000 charge-discharge cycles, and the cycling stability is 99.6%.

Example 2:

the amount of stannous chloride dihydrate used in example 1 was changed to 0.1g, the same procedure was followed as in example 1, and the final material was designated as HPCNF-2. The component material has less and unevenly distributed internal channel tin oxide content, so the effect of the tin oxide is less obvious, and the specific surface area is25cm²And/g, the specific capacitance at a current density of 1A/g is 1237.5F/g. The electrode material is assembled into a super capacitor, and as shown in fig. 3, the stability is better and reaches 90.6% after 10000 charge-discharge cycles.

Example 3:

the amount of stannous chloride dihydrate used in example 1 was changed to 0.3g, the same procedure was followed as in example 1, and the final material was designated as HPCNF-3. The hollow fiber channel of the component material is distributed with more tin oxide, but effectively adheres to less tube wall, causes certain blockage to the hollow channel, and has a specific surface area of 19.6cm²And/g, the specific capacitance at a current density of 1A/g is 1024.2F/g. The electrode material is assembled into a super capacitor, and as shown in fig. 4, the stability is good and is 88.2% after 10000 charge-discharge cycles.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.