KR101045001B1 - Fabrication Method of Porous Carbon Fibers Reinforced with Carbon Nanotubes Using Starch and Use for Electrochemical Electrode - Google Patents

Abstract

The present invention relates to a method for producing porous carbon fiber reinforced with carbon nanotubes using starch and an electrode material for electrochemistry using the same. More specifically, carbon nanotubes and fibrous forming polymers are dispersed in a starch solution, which is an environmentally friendly, low-cost, natural fibrillar forming polymer, and is then subjected to a high voltage (˜60 kV) electric field to contain ultra-fine fibers having a diameter of less than 200 nm. Prepare the felt. Oxidative stabilization of the carbon fiber felt and control of the carbonization process to produce carbon nanotube-reinforced porous carbon fiber felt containing a large amount of mesopores of 10 nm size and use of electrode material for electrochemical using the same It is about.

The carbon nanotube-reinforced porous carbon fiber felt manufactured as described above may exhibit high specific surface area and high capacitance, and thus may be used as an electrode material for ultracapacitors, fuel cell electrodes, and the like.

Carbon nanotube, porous carbon fiber felt, starch, electrode material for ultra high capacity supercapacitor, electrode material for fuel cell

Description

Fabrication Method of Porous Carbon Fibers Reinforced with Carbon Nanotubes Using Starch and Use for Electrochemical Electrode

The present invention manufactures microfiber fiber felt by electrospinning starch which is environmentally friendly and low-cost natural polymer, oxidizes and stabilizes it, and improves carbon nanotube-reinforced porous carbon fiber having pores in mesopore region by condition control of carbonization process. To manufacture. Activated carbon fibers electrospun and stabilized, carbonized, and activated using conventional PAN- and Pitch-based polymers contain large amounts of micropores (<1nm) that have a large specific surface area but are difficult to penetrate the electrolyte. . Therefore, in order to use it as an electrode material with a large capacitance, it is important to contain a large amount of mesopores, which are pore structures in which electrolyte is easily penetrated into carbon fibers. Accordingly, an object of the present invention is to use a porous carbon fiber reinforced with carbon nanotubes having pores in the mesoporous region prepared in the present invention as an electrochemical electrode material.

The present invention is to produce a microfiber fiber felt (electrober felt) by electrospinning starch which is an environmentally friendly and low-cost natural polymer and oxidatively stabilizes it to strengthen carbon nanotubes having pores in the mesopore region by condition control of the carbonization process. After preparing a porous carbon fiber felt it is used as an electrode material for electrochemistry.

Research on ultra-capacity supercapacitor electrode materials has approached practical technical limitations at this stage due to the commercialization of ultra-capacitors using activated carbon in Japan since the early 1980s. It's going on. Research on carbon nanotube composites for ultracapacitor electrode materials has been actively conducted in advanced countries such as the United States and Japan, and there are two methods of using carbon nanotubes as electrode materials or manufacturing carbon nanotube composites. Is being studied. Carbon nanotube composites are manufactured by mixing carbon nanotubes with activated carbon, which is widely used as a conventional ultracapacitor electrode material, or depositing conductive polymers such as polyaniline or metal oxides such as RuO ₂ and IrO _2, and depositing them on carbon nanotubes. have. F. Beguin (Adv. Mater. 2005, 17, 2380) and T. Liu (Carbon 2003, 41, 2427), etc., mix carbon nanotubes and polyacrylonitrile, and then carbonize the carbon nanotubes / active carbon. Composite materials were fabricated and exhibited a specific capacitance characteristic per unit weight of 100 F / g.JS Ye (Small 2005, 5, 560), etc., deposited 16.94mF / cm ² by sputtering RuO ₂ on carbon nanotubes. The capacity per unit area of is shown. In addition, V. Gupta (Electrochimica Acta 2006, 52, 1721) showed high capacity per unit weight of 485F / g by electrochemical deposition of polyaniline on carbon nanotubes. Currently, research on the production of an electric double layer supercapacitor electrode material using activated carbon, which is less expensive, has been actively conducted. However, the capacity per unit weight of the carbon nanotube composite electrode using activated carbon is still higher than that of conventional metal oxide (700F). / g) and conductive polymers (500F / g) at a significantly lower level are key challenges to be addressed in the future.

In order to solve such a problem, it is important for the activated carbon to be prepared to contain a large amount of mesopores in which electrolyte easily penetrates.

Therefore, the present invention is to produce a carbon fiber having a mesopore of uniform size through a carbonization process using starch, which is a natural polymer in which crystalline and amorphous structures are alternately laminated, not PAN and Pitch-based polymers. Now. As described above, PVA (Polyvinyl alchol) and carbon nanotubes can be added to electrospin starch which is hardly fibrous, and thus, microfiber fiber felt can be manufactured, and finally, carbon nanofibers can be processed through oxidation stabilization and process control of carbonization process. It is expected that carbon fibers containing a large amount of mesopores reinforced with tubes can be manufactured and that the characteristics of the electrode material for electrochemical can be improved by using the same.

The present invention disperses carbon nanotubes and fibrous forming polymers in a starch solution, which is a natural fibrillar forming polymer, and then applies a high voltage (˜60 kV) electric field to produce a felt containing ultra-fine fibers having a diameter of less than 200 nm. Oxidative stabilization of the carbon fiber felt and control of the carbonization process to produce carbon nanotube-reinforced porous carbon fiber felt containing a large amount of mesopores of 10 nm size and use of electrode material for electrochemical using the same It is about.

In the electric double layer supercapacitor electrode material using inexpensive activated carbon, it is important that the activated carbon contains a large amount of mesopores in which electrolyte easily penetrates. The present invention is to produce a carbon fiber having a mesopore of uniform size through a carbonization process using starch, which is a natural polymer in which crystalline and amorphous structures are alternately stacked, not conventional PAN- and pitch-based polymers. There is.

The present invention is to homogeneously disperse the fibrous forming polymer and carbon nanotubes for the electrospinning of starch, which is a non-fibrous forming natural polymer, to prepare a felt consisting of ultra-fine nanofibers and to control the oxidation stabilization and carbonization process It is to provide a method for producing a carbon fiber felt of carbon nanotube reinforced porous. In addition, the present invention provides a method for applying a carbon fiber felt containing a large amount of carbon nanotubes reinforced mesopores prepared by the present invention as an electrode material for electrochemistry.
More specifically, the present invention provides a method for preparing starch composite fiber through the steps of 1) preparing a fibrous starch composite solution by a process of processing fibrous starch forming starch, and 2) fibrous forming process of a fibrous starch composite solution. And 3) preparing a porous carbon fiber containing mesopores through a controlled heat treatment process of the starch composite fiber; The processing step is a first step of preparing a gelling starch solution by heating the starch at 100 ℃ ~ 150 ℃ and cooled to room temperature; And mixing the starch solution obtained in the first step with the fibrous forming polymer in a ratio of 5: 5 to 8: 2, and then treating the organic acid to improve heat resistance and carbonization rate for high temperature heat treatment. Characterized in that, the heat treatment process is a step of oxidizing and stabilizing the starch composite fiber at a temperature range of 150 ~ 300 ℃, carbon fiber by vacuum and inert heat treatment at a temperature range of 500 ~ 1,400 ℃; And a b step of forming a mesopor having an average size of 10 nm on the surface of the carbon fiber by vacuum heat treatment at a temperature range of 1,400 to 2,200 ° C. after the step a. It provides a method for producing a porous carbon fiber.

Porous carbon fiber felt reinforced carbon nanotubes of the present invention has excellent electrochemical properties of specific surface area and high storage capacity, unlike carbon fiber prepared using PAN-based and Pitch-based polymers. Environmentally friendly, low-cost, non-fibrous forming natural polymers can be produced by electrospinning starch, the first carbon fiber. In addition, through the process control of the carbonization process, a porous carbon fiber containing a large amount of mesopores having an average size of 10 nm is produced on the surface of the carbon fiber, and thus contains a large amount of micropores (<1 nm), a structure in which the electrolyte is difficult to penetrate. It can overcome the limitation of carbon fiber.

The present invention shows a method for producing carbon nanotube-reinforced porous carbon fiber using starch and an electrode material for electrochemistry.

The present invention comprises the steps of (1) preparing a fiber-forming starch composite solution by the processing process of the oocyte-forming starch, and (2) manufacturing a starch composite fiber through the fiber molding process of the fibrous forming starch composite solution And, (3) shows a method for producing a porous carbon fiber comprising the step of producing a porous carbon fiber containing a large amount of mesopores through a controlled heat treatment process of the starch composite fiber.

In the above process of processing the fibrous starch-forming starch, the starch may be heated at 100 ° C. to 150 ° C. and cooled to room temperature to prepare a gelized starch solution.

The processing step of the oocyte-forming starch may be carried out by mixing the starch and the fibrous forming polymer in a ratio of 5: 5 to 8: 2.

 In the above process of processing the fibrous starch-forming starch may improve the heat resistance and the rate of carbonization for the high temperature heat treatment by treating the organic acid in the gel (gel) starch solution.

 The fibrous starch composite solution may include gelled starch, a solvent, an organic acid, carbon nanotubes, and a fibrous forming polymer.

 The fiber forming process of the starch composite solution may include an electrospinning method or a wet spinning method.

The heat treatment process of the starch composite fiber in the above can be stabilized by oxidative heat treatment in the temperature range of 150 ~ 300 ℃.

 The heat treatment process of the starch composite fiber may be carbon fiber by vacuum and inert heat treatment in the temperature range of 500 ~ 1,400 ℃.

In the controlled heat treatment process of the starch composite fiber, vacuum heat treatment may be performed at a temperature range of 1,400 to 2,200 ° C. to form a large amount of mesopores having an average size of 5 to 10 nm on the surface of the carbon fiber.

The fibrous forming polymer may include at least one selected from polyvinyl alcohol, polyethylene oxide, Polycarboate, Polylactic acid, Polyvinylcarbazole, Polymethacrylate, Cellulose acetate, Collagen, Polycaprolactone, and Poly (2-hydroxyethyl methacrylate).

The solvent may include any one or more selected from water, ethanol, methanol, Dichloromethane, isopropanol, aceton, Hexafluoro-isopropanol (HFIP).

The organic acid may include any one or more selected from P-toluenesulfonic acid, Methanesulfonic acid, Trifluoromethanesulfonic acid, alkylbenzenesulfonic acid, and P-aminobenzenesulfonic acid.

 The present invention includes a felt made of a porous carbon fiber material produced by the above-mentioned method.

The present invention includes an electrode for ultra-high capacity supercapacitor using the porous carbon fiber felt.

The present invention can be used for producing the electrode for the ultra-high capacity supercapacitor of the porous carbon fiber felt.

The present invention includes an electrode for a fuel cell using the porous carbon fiber felt.

The present invention can use the porous carbon fiber felt in the production of electrodes for fuel cells.

Hereinafter, the present invention will be described in more detail.

The present invention comprises the steps of preparing a fibrous forming starch composite solution by the process of (a) egg fibrous forming starch as shown in Figure 2; (b) preparing a starch composite fiber through a fiber forming process of the fibrous forming starch composite solution; (c) producing a porous carbon fiber containing a large amount of mesopores through a controlled heat treatment process of the starch composite fiber.

More specifically, starch, a natural polymer, has a crystalline and amorphous structure alternately stacked in nano size. In order to contain a large amount of mesopores in carbon fiber after electrospinning and finally carbonizing such starch, the gelatization process of starch is required. Therefore, in the step (a) of the manufacturing process, the starch is boiled at a temperature of 100 ° C. to 150 ° C., the gelation is performed while cooling, and the organic acid is treated, and the amorphous structure in the starch is converted into mesopores through the carbonization step (c). do.

Starch, a natural polymer, is different from conventional fiber-forming polymers because it is egg-fiber formable by electrospinning. Thus, the following process is performed to prepare a fiber-forming starch composite solution. In order to facilitate the electrospinning of starch, carbon nanotubes are dispersed in a solvent with NaDDBS (Sodium Dodecylbenzene Sulfonate) as a dispersant, and then homogeneously mixed with a fibrous forming polymer, and then cooled to room temperature to form carbon nanotubes / fiber forming. Prepare a polymeric polymer solution. After homogeneously mixing the prepared carbon nanotube / fibrous forming polymer solution with the gelled starch solution to prepare a carbon nanotube / starch / fibrous forming polymer solution for electrospinning.

The solvent is one or more selected from water, ethanol, methanol, dichloromethane, isopropanol, acetone, and Hexafluoro-isopropanol (HFIP), and the organic acid is selected from P-toluenesulfonic acid, Methanesulfonic acid, trifluoromethanesulfonic acid, alkylbenzenesulfonic acid and Any one or more selected may be used. And the fibrous forming polymer is PVA (Polyvinyl alcohol), PEO (Polyethylene oxide), PC (Polycarboate), PLA (Polylactic acid), Polyvinylcarbazole, PMMA (Polymethacrylate), CA (Cellulose acetate), Collagen, Polycaprolactone (PCL) , HEMA (Poly (2-hydroxyethyl methacrylate)) can be selected and used.

In step (b), the prepared carbon nanotube / starch / fibrous forming polymer solution is placed in a syringe and subjected to high voltage to spin through a spinning nozzle to prepare starch / fibrous forming polymer nanofiber felt reinforced with ultrafine carbon nanotubes. do. Figure 3 is a microstructure of the carbon nanotube reinforced starch / PVA nanofiber felt prepared through step (b). In step (c), the fiber-formed felt prepared in step (b) is heat-treated under oxygen atmosphere and carbonized with vacuum or inert gas at a temperature in the range of 500-1,400 ° C. to finally obtain a carbon nanotube-reinforced porous carbon fiber felt. Manufacture. 4 is a microstructure of the carbon nanotubes reinforced carbon nanotubes made of reinforced carbon nanotubes, and it can be seen that the carbon fiber surface contains a large amount of mesopores of 10 nm size.

Hereinafter, the content of the present invention will be described in detail through examples. However, these are intended to explain the present invention in more detail, and the scope of the present invention is not limited thereto.

&Lt; Example 1 >

According to the above manufacturing process, 2g of starch is dissolved in 30ml of water, boiled in the temperature range of 100 ~ 150 ℃, cooled to room temperature and stored at low temperature (5 ℃) in an incubator to gel (gel) and then organic acid p-toluenesulfonic A starch solution was prepared by adding acid to 0.1 mmol per 1 g of starch. In addition, 0.02 g of carbon nanotubes and 0.02 g of NaDDBS were added to 20 ml of water, and PVA (Polyvinyl alchol) 2g was added to prepare a carbon nanotube / PVA solution. After mixing the starch solution and the carbon nanotube / PVA solution, the final solution showed a viscosity of 300-1,500 cP. Carbon nanotubes / starch / PVA nanofiber felts were prepared by electrospinning. The conditions of electrospinning were 10-30 kV, and the distance between the spinneret and spinneret was 15-20 cm.

<Example 2>

The carbon nanotubes / starch / PVA felt prepared in Example 1 was stabilized by oxidative heat treatment at a temperature range of 150 to 300 ° C., and carbonized with a vacuum or an inert gas at a temperature range of 500 to 1,400 ° C. Fiber felt was prepared. And vacuum heat treatment at a temperature range of 1,400 ~ 2,200 ℃ to finally prepare a carbon nanotube / porous carbon fiber felt having an average pore size of 10nm on the surface of the carbon fiber. The specific surface area of the carbon nanotubes / porous carbon fiber felt prepared in this temperature range was in the range of 320m ² / g to 480m ² / g.

<Example 3>

The carbon nanotube reinforced porous carbon fiber felt prepared in Example 2 was cut by 1 cm each in width and length, and the electrical capacitance of the superlayer supercapacitor was measured. The carbon nanotube-reinforced porous carbon fiber felt itself was used as an electrode, and 1 mol of sulfuric acid was used as an electrolyte. The charge / discharge voltage ranged from 0.0 to 0.5V, and the capacitance was calculated by C = I (?? V) / (?? t). 5 is a graph showing the discharge current density according to the applied voltage of the carbon nanotubes reinforced carbon nanotubes having a mesopores of 10nm size on the surface of the carbon fiber, the shape of the graph is almost similar to the ideal rectangular shape The specific capacitance calculated according to the formula was 170F / g.

<Example 4>

Platinum nanoparticles were sputtered by cutting the carbon nanotubes reinforced by the carbon nanotubes prepared in Example 2 by 1 cm in width and length, respectively. 6 (a) shows that the platinum nanoparticles were coated on the surface of the carbon fiber using a scanning electron microscope, and the platinum nanoparticles were coated on the surface of the carbon fiber through EDAX.

The carbon nanotubes coated with the platinum nanoparticles prepared as described above may apply the reinforced porous carbon fiber felt as a fuel cell electrode catalyst.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. It will be appreciated that it can be changed.

The carbon nanotube-reinforced porous carbon fiber felt presented through the present invention has excellent electrochemical properties of high specific surface area and high storage capacity as compared with the carbon fiber manufactured using the PAN-based and Pitch-based polymers. It is possible to produce carbon fiber for the first time by electrospinning starch, which is environmentally friendly and low-cost, non-fibrous forming polymer. In addition, through the process control of the carbonization process, a porous carbon fiber containing a large amount of mesopores having an average size of 10 nm is produced on the surface of the carbon fiber, and thus contains a large amount of micropores (<1 nm), a structure in which the electrolyte is difficult to penetrate. It can overcome the limitation of activated carbon fiber.

In the present invention, nanofiber felt was prepared by electrospinning starch, which is a non-fibrous forming natural polymer, and it was confirmed that it is possible to prepare porous carbon fiber containing a large amount of mesopores through oxidation control and process control of carbonization process. Using this technology, it can be applied to various filter materials as well as ultra-capacity supercapacitors and fuel cell electrode materials, which are electrode materials for electrochemicals that require materials with high specific surface area and high conductivity. This is big.

1 is a basic conceptual view of a carbon nanotube-reinforced porous carbon fiber felt prepared by electrospinning of starch.

2 is a manufacturing process chart of the carbon nanotube reinforced carbon fiber felt prepared in the present invention.

FIG. 3 is a scanning electron micrograph of carbon nanotube-reinforced starch / PVA fibers prepared by the process of FIG. 2.

FIG. 4 is a scanning electron micrograph of a carbon nanotube-reinforced porous carbon fiber having a mesopore of 10 nm size prepared by the process of FIG. 2.

5 is a specific storage capacity per unit weight according to the discharge current density of the ultra-high capacity supercapacitor of the carbon nanotubes reinforced porous carbon fiber prepared by the manufacturing process of FIG. 2 in the present invention.

FIG. 6 is a scanning electron micrograph in which platinum nanoparticles are coated on a carbon nanotube-reinforced porous carbon fiber surface prepared by the process of FIG. 2, and it is confirmed that platinum nanoparticles are coated on a carbon fiber surface through EDAX. .

Claims (15)

1) preparing a fibrous starch composite solution by a processing step of egg fibrous starch; 2) preparing a starch composite fiber through a fiber forming process of the fibrous forming starch composite solution; 3) preparing a porous carbon fiber containing mesopores through a controlled heat treatment process of the starch composite fiber; The processing step is a first step of preparing a gelling starch solution by heating the starch at 100 ℃ ~ 150 ℃ and cooled to room temperature; And mixing the starch solution obtained in the first step with the fibrous forming polymer in a ratio of 5: 5 to 8: 2, and then treating the organic acid to improve heat resistance and carbonization rate for high temperature heat treatment. Characterized in that configured, The heat treatment process is a step of oxidizing and stabilizing the starch composite fiber in the temperature range of 150 ~ 300 ℃, and carbon fiber by vacuum and inert heat treatment in the temperature range of 500 ~ 1,400 ℃; And a b step of forming a mesopor having an average size of 10 nm on the surface of the carbon fiber by vacuum heat treatment at a temperature range of 1,400 to 2,200 ° C. after the step a. Method for producing porous carbon fiber. delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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