CN104805535A - Preparation method of porous carbon nanofiber - Google Patents

Abstract

The invention belongs to the field of functional materials and discloses a preparation method of porous carbon nanofibers. The preparation method is as follows: firstly add the polymer into the solvent and stir to obtain the spinning precursor solution; then set the parameters and perform electrospinning on the spinning precursor solution to obtain nanofibers; at a heating rate of 1-5°C/min , the nanofibers are pre-oxidized in air at 100-300°C for 2-5 hours to obtain pre-oxidized nanofibers; finally, at a heating rate of 3-10°C/min, the pre-oxidized nanofibers are placed in an inert or reducing atmosphere carbonization at 600-1400°C for 2-5 hours to obtain carbon nanofibers. This method has the advantages of simple process, low cost, high yield, and environmental friendliness, which is conducive to industrial production; at the same time, the pore size distribution and specific surface area of the prepared carbon nanofibers are controllable; and the carbon nanofibers can be applied to supercapacitors, batteries, catalysts and catalyst supports , Adsorption filter materials and other fields.

Description

A kind of preparation method of porous carbon nanofiber

technical field

The invention belongs to the field of functional materials, relates to the field of preparation of nano/micro fiber materials, and in particular relates to a preparation method for preparing porous carbon nanofibers by using a variety of polymer mixed solutions as precursors and electrospinning.

Background technique

Carbon nanofiber is a new type of carbon material with excellent physical and chemical properties, such as high specific surface area, good mechanical properties, good electrical conductivity, thermal conductivity and thermal stability, and can be widely used in high Performance electrode materials, high-performance composite materials, catalyst materials, etc. Methods for preparing carbon nanofibers include template synthesis, self-assembly, phase separation, etc., but these methods are complicated in process and high in cost. Electrospinning technology is a simple and efficient method that can use polymers to prepare nanofibers, and the diameters of the prepared fibers range from tens of nanometers to several microns. The electrospinning device is simple, the process is controllable, and the cost is low. Nanofibers with uniform diameter distribution and regular shape can be prepared in large quantities. In addition, carbon nanofibers show the disadvantage of relatively low effective utilization area in application. Compared with the traditional single polymer electrospinning preparation method, the use of a variety of polymers mixed electrospinning can create different polymers according to the different carbonization processes of different polymers by rationally proportioning different polymers. Pore size distribution and specific surface area enrich the pore structure of the material.

Contents of the invention

In order to overcome the shortcomings and deficiencies of the prior art, the object of the present invention is to provide a method for preparing porous carbon nanofibers. In the invention, various polymer mixed solutions are used as a precursor solution, and then electrospinning and carbonization are performed to obtain a porous carbon nanofiber. The preparation method has the advantages of simple process, easy operation, low cost, high yield and environmental friendliness, and the prepared products can have different specific surface areas and pore size distributions.

The object of the invention is achieved through the following technical solutions:

A preparation method of porous carbon nanofibers, specifically comprising the following steps:

(1) Weigh the polymer, add it to the solvent, and magnetically stir to obtain a uniform spinning precursor;

(2) Inject the spinning precursor solution into a syringe with a spinneret, and then fix the syringe on the propulsion pump; set the electrospinning parameters, apply a DC high voltage, and carry out electrospinning of the spinning precursor solution, and the spun The fiber is received by the receiving device to obtain nanofibers;

(3) Pre-oxidize the nanofibers in air, the pre-oxidation temperature is 100-300°C, the pre-oxidation time is 2-5h, and the heating rate is 1-5°C/min, to obtain pre-oxidized nanofibers;

(4) In an inert or reducing atmosphere, carbonize the pre-oxidized nanofibers, the carbonization temperature is 600-1400°C, the carbonization time is 2-5h, and the heating rate is 3-10°C/min to obtain carbon nanofibers .

The polymer is polyvinylpyrrolidone, polyacrylonitrile, polyvinyl alcohol, polyoxyethylene, polystyrene, polyethylene glycol, polyaniline, nylon 6, nylon 66, phenolic resin, cellulose acetate, polyvinyl chloride, Two or more of polyimide or polyvinylcarbazole.

The solvent is one or more of distilled water, ethanol, chloroform, dimethylformamide, dichloromethane, tetrahydrofuran, formic acid, acetone or dimethylacetamide.

The time for the magnetic stirring is 5-36 hours, and the rotational speed of the magnetic stirring is 100-1000 r/min.

The mass concentration of the polymer in the spinning precursor liquid is 6%-40%.

The electrospinning adopts single nozzle/multiple nozzles.

The receiving device is a metal base receiver such as a flat plate, a rotating cylinder, a wire mesh, a disc, a discus-type collecting wheel, and the like.

The electrostatic spinning parameters are spinning voltage U=8-20kV, the distance L between the receiving device and the spinneret=5-20cm, and the propulsion rate R=1-8mL/h.

The inert or reducing atmosphere refers to the atmosphere of nitrogen, helium, argon or argon-hydrogen mixed gas.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The method of the present invention has the advantages of simple process, easy operation, low cost, high yield, and environmental friendliness, and is beneficial to industrialized large-scale production.

(2) The method of the present invention can prepare carbon nanofibers with different pore size distributions and specific surface areas.

(3) The porous carbon nanofibers prepared by the present invention can be applied to fields such as supercapacitors, lithium-ion batteries, sodium-ion batteries, fuel cells, lithium-air batteries, catalysts and catalyst carriers, and adsorption filter materials.

Description of drawings

Fig. 1 is a flow chart of carbon nanofiber preparation process;

Fig. 2 is the scanning electron micrograph of the porous carbon nanofiber prepared by embodiment 1;

Fig. 3 is the nitrogen adsorption-desorption adiabatic isotherm diagram of the porous carbon nanofiber prepared in Example 1;

Figure 4 is a thermogravimetric diagram illustrating the still-spun nanofibers prepared in Example 1;

FIG. 5 is a thermogravimetric diagram illustrating the still-spun nanofibers prepared in Example 2. FIG.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

A preparation method of porous carbon nanofibers, specifically comprising the following steps:

(1) Weigh polyacrylonitrile and polyvinylpyrrolidone according to the mass ratio of 1:2, add them to the dimethylformamide solvent, the mass fractions of the two polymers are 10% and 20% respectively, stir magnetically for 24 hours, and the magnetic stirring speed Be 100r/min, obtain spinning precursor liquid;

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Spinning voltage U=15kV is set, the distance L=15cm between receiver and spinneret, propulsion rate R=1mL/h, start electrospinning, and the spun fibers are received by the receiver to obtain nanofibers;

(3) Preoxidize the nanofibers in an air atmosphere, the preoxidation temperature is 280° C., preoxidize for 2 hours, and the heating rate is 1° C./min to obtain preoxidized nanofibers;

(4) Carbonize the pre-oxidized nanofibers in a nitrogen atmosphere. The carbonization temperature is 1000° C., the carbonization time is 2 hours, and the heating rate is 5° C./min. After carbonization, cool down to room temperature to obtain carbon nanofibers (i.e. porous carbon nanofibers).

The scanning electron microscope picture of gained carbon nanofiber is as shown in Figure 3, can find out that the shape of gained carbon nanofiber is regular, continuous and uniform, and the diameter of fiber is about 120nm; It is 489m ² /g, and the pore size distribution is mainly around 1.86nm.

Example 2

A preparation method of porous carbon nanofibers, specifically comprising the following steps:

(1) Weigh phenolic resin, polyimide, and polyvinylpyrrolidone according to a mass ratio of 1:1:2, and add them to a mixed solvent of dimethylformamide and ethanol. The mass fractions of the three polymers are 10%, 10%, and %, 20%, magnetically stirred for 30 hours, and the rate of magnetically stirred is 800r/min, to obtain the spinning precursor;

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Setting voltage U=12.5kV, distance L=14cm between receiver and spinneret, propulsion rate R =2mL/h, start electrospinning, the spun fibers are received by the receiver to obtain nanofibers;

(3) Preoxidize the nanofibers in an air atmosphere, the preoxidation temperature is 250°C, the preoxidation time is 3h, and the heating rate is 3°C/min, to obtain preoxidized nanofibers;

(4) Carbonize the pre-oxidized nanofibers in a nitrogen atmosphere. The carbonization temperature is 900°C, the carbonization time is 3h, and the heating rate is 7°C/min. After carbonization, cool down to room temperature to obtain carbon nanofibers (ie porous carbon nanofibers).

The shape of the obtained carbon nanofiber is regular, continuous and uniform, the diameter of the fiber is about 230nm, the specific surface area is 520m ² /g, and the pore size distribution is mainly about 2.46nm.

Example 3

A preparation method of porous carbon nanofibers, specifically comprising the following steps:

(1) Weigh polyaniline and polyoxyethylene according to the mass ratio of 2:1, add them into chloroform, and the mass fractions of the two polymers are 4% and 2% respectively, and magnetically stir for 36h, and the speed of magnetic stirring is 400r/ min to get the spinning precursor solution.

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Spinning voltage U=20kV is set, the distance L=20cm between receiver and spinneret, propulsion rate R=8mL/h, start electrospinning, and the spun fibers are received by the receiver to obtain nanofibers;

(3) Preoxidize the nanofibers in an air atmosphere, the preoxidation temperature is 300°C, the preoxidation time is 3h, and the heating rate is 5°C/min, to obtain preoxidized nanofibers;

(4) Carbonize the pre-oxidized nanofibers in a nitrogen atmosphere. The carbonization temperature is 1400° C., the carbonization time is 3 hours, and the heating rate is 10° C./min. After carbonization, cool down to room temperature to obtain carbon nanofibers (ie porous carbon nanofibers).

The shape of the obtained carbon nanofiber is regular, continuous and uniform, the diameter of the fiber is about 105nm, the specific surface area is 725m ² /g, and the pore size distribution is mainly about 1.60nm.

Example 4

A preparation method of porous carbon nanofibers, specifically comprising the following steps:

(1) Weigh polyaniline and polyvinyl alcohol according to the mass ratio of 1:4, add them to the chloroform solvent, and the mass fractions of the two polymers are 2% and 8% respectively, stir magnetically for 10 hours, and the magnetic stirring speed is 600r /min, to obtain the spinning precursor solution;

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Spinning voltage U=8kV is set, the distance L=5cm between receiver and spinneret, propulsion rate R=1mL/h, start electrospinning, and the spun fibers are received by the receiver to obtain nanofibers;

(3) Preoxidize the nanofibers in an air atmosphere, the preoxidation temperature is 230°C, the preoxidation time is 5h, and the heating rate is 1°C/min, to obtain preoxidized nanofibers;

(4) Carbonize the pre-oxidized nanofibers in a nitrogen atmosphere. The carbonization temperature is 600° C., the carbonization time is 5 hours, and the heating rate is 3° C./min. After carbonization, cool down to room temperature to obtain carbon nanofibers (i.e. porous carbon nanofibers).

The shape of the obtained carbon nanofiber is regular, continuous and uniform, the diameter of the fiber is about 265nm, the specific surface area is 430m ² /g, and the pore size distribution is mainly about 5.7nm.

Illustrative Examples 1-2: Carbonization process of different polymers

Illustrative Example 1

A method for preparing nanofibers, specifically comprising the following steps:

(1) Weigh polyvinyl alcohol pyrrolidone, join in the dimethylformamide solvent, magnetic stirring 24h, the speed of magnetic stirring is 500r/min, obtain spinning precursor solution, the quality of polyvinyl alcohol pyrrolidone in the said precursor solution A score of 20%;

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Spinning voltage U=15kV is set, the distance L=15cm between receiver and spinneret, propulsion rate R=1mL/h, start electrospinning, and the spun fibers are received by the receiver to obtain nanofibers; the thermogravimetric curve is shown in Figure 4.

Illustrative Example 2

A method for preparing nanofibers, specifically comprising the following steps:

(1) Weigh polyacrylonitrile, join in dimethylformamide solvent, magnetically stir 24h, the speed of magnetic stirring is 300r/min, obtain spinning precursor solution, the mass fraction of polyacrylonitrile in said precursor solution 10%;

(2) Spinning precursor liquid is injected into the syringe that has spinneret, then syringe is fixed on the propulsion pump; Spinning voltage U=15kV is set, the distance L=15cm between receiver and spinneret, propulsion rate R=1mL/h, start electrospinning, and the spun fibers are received by the receiver to obtain nanofibers; the thermogravimetric curve is shown in Figure 5.

The above-mentioned examples 1, 2, 3 and 4 are specific implementations of the present invention, but the implementation of the present invention is not limited by the examples, as the above-mentioned electrospinning precursor can be polyvinylpyrrolidone, polyacrylonitrile , polyvinyl alcohol, polyoxyethylene, polystyrene, polyethylene glycol, polyaniline, nylon 6, nylon 66, phenolic resin, cellulose acetate, polyvinyl chloride, polyimide or polyvinyl carbazole Or more than two kinds can be designed in combination according to the desired microstructure. Any other changes made without departing from the spirit and principle of the present invention are included within the protection scope of the present invention.

Claims (9)

1. a preparation method for porous carbon nanofiber, is characterized in that: specifically comprise the following steps:

(1) take polymer, add in solvent, magnetic agitation obtains uniform spinning precursor liquid;

(2) spinning precursor liquid is injected the syringe with spinning head, then syringe is fixed on boost pump; Arrange electrospinning parameters, apply DC high voltage, spinning precursor liquid is carried out electrostatic spinning, spun fiber is received device and receives, and obtains nanofiber;

(3) nanofiber is carried out pre-oxidation in atmosphere, Pre oxidation is 100 ~ 300 DEG C, and the time of pre-oxidation is 2 ~ 5h, and heating rate 1 ~ 5 DEG C/min, obtains the nanofiber of pre-oxidation;

(4) in inertia or reducing atmosphere, the nanofiber of pre-oxidation is carried out carbonization, the temperature of carbonization is 600 ~ 1400 DEG C, and the time of carbonization is 2 ~ 5h, and heating rate 3 ~ 10 DEG C/min, obtains carbon nano-fiber.

2. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described polymer is two or more in polyvinylpyrrolidone, polyacrylonitrile, polyvinyl alcohol, polyoxyethylene, polystyrene, polyethylene glycol, polyaniline, nylon 6, nylon66 fiber, phenolic resins, cellulose acetate, polyvinyl chloride, polyimides or polyvinylcarbazole.

3. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described solvent is more than one in distilled water, ethanol, chloroform, dimethyl formamide, carrene, oxolane, formic acid, acetone or dimethylacetylamide.

4. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: the time of described magnetic agitation is 5 ~ 36h, and magnetic agitation rotating speed is 100 ~ 1000r/min.

5. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: in described spinning precursor liquid, the mass concentration of polymer is 6% ~ 40%.

6. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described electrospinning parameters is spinning voltage U=8 ~ 20kV, the distance L=5 between receiving system and spinning head ~ 20cm, advances speed R=1 ~ 8mL/h.

7. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described inertia or reducing atmosphere refer to the atmosphere of nitrogen, helium, argon gas or argon hydrogen gaseous mixture.

8. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described electrostatic spinning adopts single injector or multiinjector.

9. the preparation method of porous carbon nanofiber according to claim 1, is characterized in that: described receiving system is metallic substrates receiver.