KR101270716B1 - Mehod for producing photocatalyst-graphenes-carbon nano-fiber composite - Google Patents

Abstract

The present invention relates to a photocatalyst, and more particularly, to a photocatalyst-graphene-carbon nanofiber composite, a method for preparing the composite, and a filter including the composite, which is a new photocatalyst complex having high photocatalytic activity in the visible light region. .

Description

Photocatalyst-graphene-carbon nanofiber composite manufacturing method {Mehod for producing photocatalyst-graphenes-carbon nano-fiber composite}

The present invention relates to a photocatalyst, and more particularly, to a photocatalyst-graphene-carbon nanofiber composite, a method for preparing the composite, and a filter including the composite, which is a new photocatalyst complex having high photocatalytic activity in the visible light region. .

Various methods and materials have been developed to solve environmental problems. Among these methods, photocatalysts decompose organic pollutants using solar light, which does not cause incidental pollution.

A photocatalyst is a substance that promotes a chemical reaction, although it does not change itself due to irradiation of light, and refers to a substance that advances a catalytic reaction using light as an energy source. The photocatalyst is a semiconducting metal oxide or a sulfur compound. This is used. Such photocatalysts have been known to decompose various biologically hardly decomposable substances that existing microorganisms cannot remove. Examples of such photocatalysts include ZnO, WO ₃ , SnO ₂ , ZrO ₂ , TiO ₂ , and CdS. There is this.

In particular, TiO ₂ photocatalyst has various fields such as low cost, harmlessness of human body, sterilization, effective degradability of various organic matters, stability and continuous durability, etc. Application is possible at As such, TiO ₂ photocatalysts are in the spotlight because they are eco-friendly and economical because they are inexpensive, use light as an energy source, and can be used semi-permanently.

Photocatalytic materials, including semiconducting metals such as TiO ₂ , are excited by electrons from the valence band to the conduction band when a certain region of energy is applied. That is, electrons [e-, electrons] are formed in the conduction band, and holes [h +, electron holes] are formed in the valence band. The hole (h +) reacts with water to produce hydroxyl radical (-OH). In the opposite reduction reaction, oxygen is reduced in air to produce superoxide anion (O ₂ ⁻ ) and two active oxygen. In particular, since radicals have high oxidation and reduction potentials, it has been found to have an excellent effect on NO _x , SO _x , volatile organic compounds (VOCs) and various malodors.

On the other hand, carbon nanofibers are a new type of carbon material that can be used for adsorption, decolorization, water treatment agent, deodorant, humidity control agent to remove moisture by using large adsorption characteristics of fine porous structure. Carbon nanofibers containing photocatalysts use the large specific surface area and shallow pore depth of existing carbon nanofibers to act as a supporter that shows excellent adsorption performance and fast adsorption rate of contaminants, while fixing photocatalysts. Because of the effect, efficient photocatalytic activity can be expected and can be used as a composite in various fields.

Korean Patent Application No. 10-2008-0137971 invented by the present inventors has a photocatalytic property, that is, a decomposability, using carbon nanofibers and a photocatalyst material, and at the same time, it has an inherent property, that is, adsorption capacity, of carbon nanofibers, thereby providing a superior purification function. Disclosed is a method for producing a composite carbon nanofiber having a photocatalytic activity and a composite carbon nanofiber prepared by the method, and more specifically, "Carbon nanofiber obtained by electrospinning a spinning solution in which a carbon nanofiber precursor material is dissolved. Stabilizing the precursor at 200 to 350 ° C. to obtain a flame resistant fiber; preparing a photocatalyst sol solution; immersing and coating the flame resistant fiber in the photocatalyst sol solution; and drying the coated flame resistant fiber It describes a method for producing a composite carbon nanofiber having a photocatalytic activity comprising the step of carbonizing.

However, the composite carbon nanofibers manufactured by the method of manufacturing the composite carbon nanofiber disclosed in the patent not only are not uniformly formed by agglomeration of photocatalytic particles on the surface, but also in the visible light region, which occupies most of the sunlight in the same process as the conventional photocatalytic materials. There was a problem in that it does not exhibit photocatalytic activity.

In other words, despite the photocatalyst number of benefits, including TiO _2, and most of the band gap of the photocatalyst material it is because it is 3.0 ~ 3.2 eV or more light in this order to overcome the band gap short UV than 385 nm region, including TiO ₂ Because it is necessary. However, since the ultraviolet region is less than 5% of sunlight, in order to effectively use solar energy, it must be able to react in the light of visible region, which occupies a high proportion of sunlight, so that transition metal doping, plasma treatment, electron beam irradiation, and non-metal doping Along with various reforming methods such as ion implants and ion implants, many studies have been conducted to improve the reaction efficiency by increasing the surface area of TiO ₂ , but no effective technology has been developed.

In addition, Graphene has a planar structure with a large specific surface area while having both metal and semiconductor properties, and is a material that has recently been in the spotlight in the fields of transparent electrodes, electrochemical electrodes, and catalyst supports. Graphene is characterized by the number of layers formed. In the case of multi-layer graphene, it is characteristic of semiconductor and helps to form nano-sized crystal when combined with metal or metal oxide. A lot of researches are being used as photocatalyst support. However, to produce pure Graphene, it has high production cost and low production efficiency, which makes it difficult to use Graphene materials as catalyst support.

Therefore, the necessity of developing a new photocatalytic material that maximizes the performance of the photocatalyst and reacts in visible light is urgently required in the area of development of environmental technology, energy technology and new material.

The present inventors have completed the present invention by developing a photocatalytic material that reacts in visible light by utilizing the advantages of Graphene having a high specific surface area as well as excellent electrical properties as a result of research efforts to solve this problem.

Accordingly, an object of the present invention is to absorb light in the visible region, showing high photocatalytic activity not only in the ultraviolet region but also in the visible region, and thus has a high reaction efficiency even under outdoor sunlight and fluorescent lamps in the room. It is to provide a photocatalyst-graphene-carbon nanofiber composite, which can be used in the field and daily life, the composite manufacturing method, and a filter comprising the composite.

It is another object of the present invention to increase the amount of organic matter supported by a large surface area, and because the depth of the pores is shallow because the adsorption and desorption rate is fast photocatalyst-graphene-carbon nanofibers can increase the reaction rate of photocatalytic activity It is to provide a complex, a method for producing the complex, and a filter comprising the complex.

Yet another object of the present invention is that graphene uniformly disperses photocatalytic particles on the surface of the composite in nanoparticle size, as well as performing a trap role to stably hold electrons moving in the photocatalyst, thereby improving photocatalytic activity efficiency. It is to provide a photocatalyst-graphene-carbon nanofiber composite which can be increased, a method for preparing the composite, and a filter including the composite.

Still another object of the present invention is to add a graphene having a high dispersibility in a solvent by combining heteroatoms in a spinning solution to produce carbon nanofibers containing graphene, thereby reducing the production cost through simplifying the cost and manufacturing process. It is to provide a filter comprising a graphene-carbon nanofiber composite, the composite production method, and the composite.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object of the present invention, the present invention provides a photocatalyst-graphene-carbon nanofiber composite comprising graphene having a high photocatalytic activity in the visible region as well as having in the ultraviolet region. .

In a preferred embodiment, the photocatalyst included in the photocatalyst-graphene-carbon nanofiber composite is uniformly dispersed on the surface of the composite through interaction with graphene to form crystals having a size of 20 to 50 nm.

In a preferred embodiment, the photocatalyst included in the photocatalyst-graphene-carbon nanofiber composite is any one selected from the group consisting of ZnO, WO ₃ , SnO ₂ , ZrO ₂ , TiO ₂ .

In a preferred embodiment, when the photocatalyst is TiO ₂ , the crystal structure of anatase and rutile is mixed in a ratio of 1: 1 in the TiO ₂ crystal structure formed on the surface of the composite.

In a preferred embodiment, the photocatalyst-graphene-carbon nanofiber composite is a composite when subjected to light with energy between band gaps ( E _g > 3.0 eV), even though it contains rutile crystals with low photocatalytic efficiency. Graphene contained within creates a trap site of excited electrons or holes to reduce recombination of electron-hole pairs.

In a preferred embodiment, after 30 minutes under visible light of the photocatalyst-graphene-carbon nanofiber composite, the removal efficiency of 15 ppm Methylene blue is 100% and can be reused.

In addition, the present invention comprises the steps of dissolving the carbon nanofiber precursor material and graphene to prepare a graphene-containing fat using solution; Preparing a graphene-containing precursor fiber by electrospinning the spinning solution; Stabilizing the precursor fiber at 200 to 300 ° C. to produce graphene-containing flame resistant fiber; Preparing a photocatalyst sol solution; Coating the graphene-containing chloride resistant fiber by dipping the photocatalyst sol solution; And it provides a photocatalyst-graphene-carbon nanofiber composite manufacturing method comprising the step of carbonizing the coated flame resistant fiber after drying.

In a preferred embodiment, the graphene-containing fat solution contains 1 to 20% by weight of graphene based on the carbon nanofiber precursor material.

In a preferred embodiment, the step of preparing the graphene-containing fat solution includes the step of dispersing the graphene in the DMF using ultrasonic waves and dissolving the PAN in the dispersion solution.

In a preferred embodiment, the coating step is performed by immersing the flame resistant fiber in the photocatalyst sol solution for 1 to 3 hours, the carbonizing step is performed by heating to 800 ~ 1000 ℃.

In a preferred embodiment, the carbon nanofiber precursor material is any one selected from the group consisting of polyacrylo nitrile (PAN), polyimide, polybenzimidazole (PBI), pitch .

In a preferred embodiment, the photocatalyst precursor material comprises any one selected from the group consisting of ZnO, WO ₃ , SnO ₂ , ZrO ₂ , TiO ₂ .

The present invention also provides a filter having a high photocatalytic activity in the visible region, including the photocatalyst-graphene-carbon nanofiber composite described above, in the ultraviolet region.

In a preferred embodiment, the filter includes an air purifier filter, a vehicle exhaust gas purification filter, a water purification filter.

The present invention has the following excellent effects.

First, the photocatalyst-graphene-carbon nanofiber composite of the present invention and the filter including the composite can absorb light in the visible region and thus exhibit high photocatalytic activity in the visible region as well as in the ultraviolet region. Because it has high reaction efficiency even under fluorescent lamps and indoors, it can be used in more various industrial sites and daily life.

In addition, the photocatalyst-graphene-carbon nanofiber composite of the present invention and the filter including the complex have a large surface area, which can dramatically increase the amount of organic matter supported, and the depth of the pores is shallow, so that the adsorption and desorption rate is high, thus the photocatalytic activity The reaction rate of can be increased.

In addition, according to the photocatalyst-graphene-carbon nanofiber composite of the present invention, the method for preparing the composite, and the filter including the composite, graphene not only uniformly disperses the photocatalyst particles in nano size on the surface of the composite and is fixed. The efficiency of photocatalytic activity can be increased by performing a trap role to stably hold electrons moving in the photocatalyst.

In addition, according to the method for preparing a photocatalyst-graphene-carbon nanofiber composite according to the present invention, a heteroatom is bonded to a graphene-containing carbon nanofiber by adding graphene having a high dispersion degree to a solvent to a spinning solution, thereby producing a carbon nanofiber containing graphene. By simplifying the manufacturing cost can be lowered.

1 is a flow chart showing an embodiment of a titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -graphene / CNF) in the photocatalyst-graphene-carbon nanofiber composite of the present invention and another comparative photocatalyst ,
2 is a full-domain scan (XPS Survey) graph of X-ray photoelectron spectroscopy (XPS) spectrum of graphene
In Figure 3 (a) is an electron micrograph of TiO ₂ / CNF, (b) is a photocatalyst-graphene-carbon nanofiber composite of the present invention formed by coating TiO ₂ on graphene / CNF according to the manufacturing process of Figure 1 Electron micrograph of the TiO ₂ -graphene / CNF composite as an embodiment,
In Figure 4 (a) is a transmission electron micrograph (TEM) of the TiO ₂ -Graphene / CNF composite of the photocatalyst-graphene-carbon nanofiber composite of the present invention, (b) is a TiO ₂ -Graphene / CNF complex Limited field electron diffraction (SAED) results of the nanoparticles present on the surface of the nanoparticles, (c) are elemental mapping images of the energy dispersive X-ray spectrometer of the TiO ₂ -Graphene / CNF complex,
Figure 5 (a) is an X-ray diffraction pattern graph of the TiO ₂ -Graphene / CNF composite of an embodiment of the photocatalyst-graphene-carbon nanofiber composite of the present invention, (b) is an X-ray diffraction pattern of TiO ₂ -CNF graph,
6 is a Raman spectrum graph of a TiO ₂ -Graphene / CNF composite, which is an embodiment of the photocatalyst-graphene-carbon nanofiber composite of the present invention;
7 is a full-area scan (XPS Survey) graph of the X-ray photoelectron spectroscopy (XPS) spectrum of the TiO ₂ -Graphene / CNF complex of an embodiment of the photocatalyst-graphene-carbon nanofiber composite of the present invention,
Figure 8 (a) is a graph showing the result of separating the peak of Ti2p by X-ray photoelectron spectroscopy (XPS) of TiO ₂ -Graphene, (b) is one of the photocatalyst-graphene-carbon nanofiber composite of the present invention Graph showing the result of separating the peak of Ti2p by X-ray photoelectron spectroscopy (XPS) of the TiO ₂ -Graphene / CNF composite as an example,
9 is a UV-Vis spectrophotometric diagram of the concentration change of 15 ppm Methylene blue solution according to the visible light irradiation time of the TiO ₂ -Graphene / CNF composite and the comparative material of an example of the photocatalyst-graphene-carbon nanofiber composite of the present invention Graph,
10 is a graph showing the decomposition performance of 15ppm methylene blue solution according to continuous use under visible light irradiation of TiO ₂ -Graphene / CNF composite of an embodiment of the photocatalyst-graphene-carbon nanofiber composite of the present invention.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Hereinafter, the technical structure of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals used to describe the present invention throughout the specification denote like elements.

The first technical feature of the present invention is that the nanoparticle photocatalyst particles having graphene (Graphene) and 20 to 50 nm are uniformly dispersed on the surface of the composite to have a high photocatalytic activity in the visible region. Characterized in photocatalyst-graphene-carbon nanofiber composite.

Here, the photocatalyst included in the photocatalyst-graphene-carbon nanofiber composite of the present invention is uniformly dispersed on the surface of the composite to have a nanoparticle size, that is, a particle size of less than 100 nm, as described above. It can be formed into crystals of 20 to 50nm size through the interaction of. That is, since graphene included in the photocatalyst-graphene-carbon nanofiber composite fixes the photocatalyst and disperses the photocatalyst evenly on the surface of the carbon nanofiber composite prepared by high temperature heat treatment, having the nanoparticle size. to be. As such, when the photocatalyst is uniformly formed on the surface of the composite, the contact area is relatively increased to increase the activity of the photocatalyst, and when the photocatalyst particles are formed in nanoscale, the photocatalyst formed of particles larger than the nanosize due to the quantum size effect. Photocatalytic reactions can be seen in visible light with energy lower than the typical bandgap of.

In addition, when the photocatalyst-graphene-carbon nanofiber composite receives light, electrons and holes of the photocatalyst move toward conductivity and electrons and holes are formed, and the graphene particles included in the composite are multi-layer graphene. ), Which itself is a semiconductor, it acts as a trap to reduce the band gap and to stably hold the electrons, thus recombining the electron-hole pairs when receiving light with energy between band gaps ( E _g > 3.0 eV). Since the photocatalytic activity is increased by the role of reducing the high photocatalytic activity in the visible region as well as the ultraviolet region.

In addition, the photocatalyst included in the photocatalyst-graphene-carbon nanofiber composite of the present invention is a metal oxide, which is selected from the group of semiconducting metal materials, that is, ZnO, WO ₃ , SnO ₂ , ZrO ₂ , TiO ₂ , CdS It may be one, it may be preferable that the TiO ₂ in terms of cost effectiveness.

In addition, when the photocatalyst included in the photocatalyst-graphene-carbon nanofiber composite of the present invention is TiO ₂ , preferably, the TiO ₂ crystal structure formed on the surface of the composite is mixed in a ratio of 1: 1 of the anatase and rutile do.

The photocatalyst-graphene-carbon nanofiber composite of the present invention having such a configuration has a removal efficiency of 15% Methylene blue 100% after 30 minutes under visible light and is reusable. The synergistic effect of photocatalytic activity can be expected.

(1) Graphene: Combined with a photocatalyst, the photocatalyst particles are uniformly dispersed on the surface of the carbon nanofiber composite to help form nanoscale particles, increasing the efficiency of photocatalytic activity, especially in the case of multilayer graphene, narrowing the band gap and By acting as a trap that traps the electrons formed during the excitation reaction, the photocatalytic activity is increased by increasing the duration of the electrons and holes, thereby showing high photocatalytic activity not only in the ultraviolet region but also in the visible region.

(2): Nano-sized photocatalyst particles: Photocatalytic particles uniformly formed on the surface of carbon nanofiber composites with nano-size even in visible light having energy lower than the general bandgap of photocatalysts formed of particles larger than nano-size due to quantum size effect It can show a photocatalytic reaction.

(3) Carbon nanofibers: Carbon nanofibers, which are used as a support for photocatalyst-graphene-carbon nanofiber composites, have a large surface area, which can dramatically increase the amount of organic matter supported. Therefore, the reaction rate of photocatalytic activity is increased.

Next, a second technical feature of the present invention is that a photocatalyst sol is a graphene-containing flame resistant fiber obtained by electrospinning and stabilizing a spinning solution obtained by dispersing graphene and a carbon fiber precursor having high dispersibility in a solvent by combining heteroatoms. It is to inexpensively and simply prepare a photocatalyst-graphene-carbon nanofiber composite having excellent photocatalytic efficiency through a process of carbonization after immersion in a solution.

Therefore, the photocatalyst-graphene-carbon nanofiber composite production method of the present invention comprises the steps of dissolving the carbon nanofiber precursor material and graphene to prepare a graphene-containing emulsion solution; Preparing a graphene-containing precursor fiber by electrospinning the spinning solution; Stabilizing the precursor fiber at 200 to 300 ° C. to produce graphene-containing flame resistant fiber; Preparing a photocatalyst sol solution; Coating the graphene-containing chloride resistant fiber by dipping the photocatalyst sol solution; And carbonizing the coated flame resistant fiber after drying.

Here, it is preferable that the graphene-containing fat solution contains 1 to 20% by weight of graphene based on the carbon nanofiber precursor material.

The graphene-containing fat using solution is preferably prepared comprising the step of dispersing the graphene in DMF using ultrasonic waves and dissolving PAN in the dispersion solution.

The coating step is performed by immersing the flame resistant fiber in the photocatalyst sol solution for 1 to 3 hours, and the carbonizing step is performed by heating up to 800 to 1000 ° C. Through the heat treatment process, the photocatalyst is uniformly dispersed on the surface. It is to prepare a photocatalyst-graphene-carbon nanofiber composite formed.

Meanwhile, the carbon nanofiber precursor material may be any one selected from the group consisting of polyacrylo nitrile (PAN), polyimide, polybenzimidazole (PBI), and pitch. For example, when polyacrylonitrile is used, the polyacrylonitrile for fiber molding (PAN, molecular weight = 160,000) is modified with not only 100% homopolymer but also 5-15% copolymer. It is possible to use acryl, and as the composition of the copolymer, itaconic acid (itaconic acid) or methyl acrylate (methylacrylate, MA) and the like may be used as a copolymer.

The third technical feature of the present invention is a filter having high reaction efficiency under outdoor sunlight and fluorescent lamps because it can absorb light in the visible region and shows high photocatalytic activity not only in the ultraviolet region but also in the visible region. .

Accordingly, the present invention provides a filter having a high photocatalytic activity in the visible light region, including any one of the photocatalyst-graphene-carbon nanofiber composites described above, in the ultraviolet region. It can be widely used for air purifier filter with adsorption and decomposition function, automobile exhaust gas purification filter, etc., and can be widely used for water purification as it can decompose wastewater treatment, water pollutants and pigments. In particular, instead of the conventional TiO ₂ photocatalyst, which exhibited photocatalytic activity only in the ultraviolet region and has a limited use range, it has a high reaction efficiency even under outdoor sunlight and fluorescent lamps in the room, and thus can be used in various industrial sites and daily lives.

Example

A titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -Graphene / CNF composite) was prepared as follows according to the preparation method shown in FIG.

1. Graphene / PAN Chlorinated Fiber Manufacturing

Graphene purchased xGNP-C 750 grade from XG Science and PAN purchased a reagent having a molecular weight of 150,000 and used without purification.

Graphene was dispersed in DMF (N, N-dimethyformamide) using ultrasonic waves, and then PAN was dissolved therein to prepare a graphene-containing solution. Here, graphene was used as the weight ratio of 3 wt% of PAN, a carbon nanofiber precursor. The prepared graphene-containing spinning solution was prepared by using an electrospinning method to prepare a nonwoven web composed of nanofibers, which are photocatalyst-containing precursor fibers. In this case, the electrospinning apparatus applied an applied voltage of 25 kV (variable in the range of 20 to 30 kV) to the nozzle and the collector, respectively, and the distance between the spinneret and the collector was varied as needed about 10 to 30 cm.

Spinning fibers (nonwoven webs) obtained by electrospinning, that is, graphene-containing precursor fibers, were supplied with a compressed air at a flow rate of 5 to 20 mL per minute using a hot air circulation 爐, and maintained at 250 ° C. for 1 hour at a temperature rising rate of 1 ° C. per minute. Stabilization was performed to obtain graphene / PAN chloride fiber.

2. Preparation of Titanium Dioxide-Graphene-Carbon Nanofiber Composite (TiO ₂ -Graphene / CNF Composite)

The TiO ₂ sol solution was prepared by purchasing titanium n -butoxide (Ti (O ⁿ Bu) ₄ ), ethanol (Ethyl alcohol) and toluene (98%) of STREMCHEMICALS as follows: First 1: 1 / v: TiO ₂ sol solution was completed by mixing titanium n -butoxide with ethanol and toluene having a ratio of v.

The TiO ₂ sol solution thus prepared was immersed and coated with graphene / PAN flame retardant fiber for 1 hour, unreacted titanium n- butoxide was removed, washed, dried in air, and then heated to 800 ° C. at a rate of 5 ° C. per minute. Heat treatment to prepare a TiO ₂ -Graphene / CNF composite.

Comparative Example 1

TiO ₂ / CNF was prepared according to the preparation method shown in FIG. 1.

Comparative Example 2

CNF was prepared according to the preparation method shown in FIG.

Comparative Example 3

According to the manufacturing method shown in Figure 2 was prepared graphene / CNF.

Experimental Example 1 Analysis of Physical Properties of Graphene

In order to analyze the physical properties of the graphene elemental analysis by the Mettler method is shown in Table 1 the results.

Elemental analysis C H N O Grapina 88.68 0.79 1.11 7.95

From Table 1, it can be seen that the contents of nitrogen and oxygen are relatively high. That is, since the graphene content of the heteroatom is relatively high, it can be expected to be well sprayed on the organic solvent.

In addition, X-ray photoelectron spectroscopy was performed as a surface analysis to determine the constituent elements and chemical bonding states of the surface and the interface of graphene, and the results are shown in FIG. 2. As shown in FIG. 2, a wide scan (0-1100 eV) of the entire energy region was used to identify elements, and carbon and oxygen atoms were clearly seen and the nitrogen atoms were weak. Based on the XPS Survey's full-area scan (XPS Survey), the area of the photoelectron peak coming from the surface of graphene is derived from C1s (285 eV), N 1s (400 eV), and O 1s (533 eV). The elemental composition ratio of is shown in Table 2.

Sample O / C Elemental composition ratio (Atomic%) C O N Grapina 0.06 93.29 5.90 0.81

Experimental Example 2 Observation of Appearance Electron Microscope

Obtained in Comparative Example 1 TiO ₂ / CNF and the TiO ₂ -Graphene / CNF composite obtained in Example were observed under an electron microscope at 100 nm scale, and the SEM image is shown in FIG. 3 as a result.

As shown in FIG. 3 (a), TiO ₂ / CNF has TiO ₂ particles agglomerated to form large particles of about 100 nm or more. On the other hand, TiO ₂ -Graphene / CNF obtained in the Examples As shown in FIG. 3 (b), it can be seen that TiO ₂ particles having a size of about 30 nm are uniformly distributed on the surface of the composite. As such, the SEM photograph of FIG. 3 (b) shows that when graphene is included in the carbon nanofibers when the metal oxide such as a photocatalyst is formed on the surface of the carbon nanofibers, the graphene and the metal oxide are affected by the graphene included therein. The interaction shows that nanosized TiO ₂ particles are uniformly well dispersed on the surface of the carbon nanofiber composite.

Experimental Example 3: Structural Analysis of Titanium Dioxide-Graphene-Carbon Nanofiber Composite (TiO ₂ -Graphene / CNF Complex)

In order to analyze the structure of the titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -Graphene / CNF composite) obtained in the Example, the following experiment was carried out, and the results are shown in FIGS. It was.

1. Observation with transmission electron microscope (TEM)

Observation was made with a transmission electron microscope (TEM), and the photograph is shown in FIG.

From the transmission electron microscope (TEM) image of the TiO ₂ -Graphene / CNF composite shown in Figure 4 (a) it can be seen that the average crystal size of 30 nm is well dispersed on the surface of the carbon nanofiber composite.

2. Check the internal structure of the material

TiO ₂ -Graphene / CNF to know the internal structure of materials Limited field electron diffraction (SAED) of the nanoparticles present on the surface of the composite was carried out, and the resulting photograph is shown in FIG. 4 (b). Is shown in Figure 4 (c).

As shown in (b) of FIG. 4B, the superlattice diffraction points of the (110), (211), and (101) forms are shown as the diffraction pattern, thereby confirming the rutile crystalline diffraction pattern of the TiO ₂ nanoparticles. .

In addition, C, Ti, and O elements were identified from FIG. 4 (c), and the dispersion distribution of Ti and O were similar, indicating that the crystal was TiO ₂ due to the intensive distribution of nanocrystals.

3. Confirmation of TiO ₂ crystallinity by graphene

TiO ₂ -Graphene / CNF to determine TiO ₂ crystallinity by graphene X-ray diffraction analysis of the composite and TiO ₂ -CNF is shown in Figure 5 the results.

TiO ₂ -Graphene / CNF as shown in FIG. 5 (a) In the case of composites, there are two broad peaks representing low crystalline carbon centered on θ = 23 ° and two TiOs: anatase (2θ = 25 °) and rutile (2θ = 28, 36.02, 41.27, 54.38, 56.62 °). ₂ crystalline peaks were observed. In addition, the crystal structures of anatase and rutile were mixed in a ratio of almost 1: 1.

On the other hand, TiO ₂ -CNF as shown in Figure 5 (b) was confirmed that the crystal structure of anatase and rutile is 1: 4.

These experimental results show that graphene contained in carbon nanofibers prevents TiO ₂ from agglomerating at high temperatures by preventing TiO ₂ particles and molecules from moving, thereby increasing particle size and inhibiting phase transition from anatase to rutile. It can be expected to.

4. Raman spectrum analysis

In addition, TiO ₂ -Graphene / CNF The complex was analyzed by Raman spectrum and the results are shown in FIG. 6.

As shown in FIG. 6, D-band and G-band of carbon were observed at 1360 cm ⁻¹ and 1580 cm ⁻¹ , respectively, and four peaks of 143, 256, 431, 612 cm ⁻¹ and 144 cm representing rutile on TiO ₂ were observed. A peak indicating anatase crystals at ^-1 was found.

5. Confirmation of constituent elements and chemical bonding state of surface and interface

TiO ₂ -Graphene / CNF X-ray photoelectron spectroscopy was used to analyze the constituent elements and chemical bonding states of the surface and the interface of the composite. In order to identify the element, a full scan (0-1100 eV) was performed in the entire energy region, and the photograph is shown in FIG. In addition, TiO ₂ -Graphene / CNF The elemental composition ratios of C1s (285V), N1s (400eV), O1s (530eV), Ti2p (459eV) were analyzed through the area of the photoelectron peak coming from the surface of the composite, and the results are shown in Table 3.

Sample Elemental composition ratio (Atomic%) C O N Ti Graphene-TiO ₂ / CNF 47.5 36.0 2.78 13.7

6. Ti peak separation by XPS

Synthesis of TiO ₂ -CNF and TiO ₂ -Graphene / CNF Composites Using XPS Ti peaks were separated and the results are shown in FIGS. 8 (a) and 8 (b), respectively.

As shown in Fig. 8 (a), of Ti ⁴⁺ Ti2p _1/2 and Ti2p _3/2 corresponding to peak at 459.62 and 465.23 eV binding energy was observed that in, TiO ₂ for -Graphene / CNF composite as shown in Fig. 8 (b) Ti ^4+, as well as 461.90 and Ti ³⁺ at 458.58 eV Ti2p _1/2 and Ti2p _3/2 peaks were observed at the same time.

These experimental results show that the Ti oxidation state of TiO ₂ surface was changed in TiO ₂ -Graphene / CNF composite containing graphene. Thus, the changed Ti oxidation state, especially Ti ^3+, is a trap of carriers generated by photo-excitation. action by electron (e ^-) were predicted to reduce the recombination rate of the positive hole (h ⁺⁾ to promote the conclusion as photoactive.

Experimental Example 4 Measurement of Specific Surface Area of Titanium Dioxide-Graphene-Carbon Nanofiber Composite (TiO ₂ -Graphene / CNF Composite)

In order to evaluate the specific surface area value of the titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -Graphene / CNF composite) prepared in the example, a total of four types of samples were prepared together with the comparative photocatalysts obtained in Comparative Examples 1 to 3. TiO ₂ -Graphene / CNF composite, TiO ₂ / CNF, Graphene / CNF, CNF) was prepared to measure the specific surface area and the results are shown in Table 4.

TiO ₂ -Graphene / CNF Graphene / CNF TiO ₂ -CNF CNF BET Surface area (m ² / g) 434 447 361 405 Total pore volume (cm ³ / g) 0.235 0.177 0.149 0.183 Average pore diameter
(nm) 2.17 1.58 1.60 1.81

From Table 4, it can be seen that the TiO ₂ -Graphene / CNF composite, Graphene / CNF, TiO ₂ -CNF, CNF exhibited specific surface area values of 434, 447, 361, and 405 m ² / g, respectively. In the case of TiO ₂ -CNF, the crystal size of TiO ₂ particles is increased (110 nm) and the specific surface area of CNF is reduced by preventing the dispersion of crystals. As a result, TiO ₂ -Graphene / CNF composites with higher specific surface area can store organic contaminants than TiO ₂ -CNF composites with lower specific surface area (409.63 m ² / g), which results in higher capacity and faster desorption rate. It shows that the photocatalytic activity can be increased. In addition, since Graphene / CNF removes organic substances using only the adsorptive structure of the porous structure rather than the photocatalytic effect, the purification ability is sharply reduced when the adsorption is completed.

On the other hand, the TiO ₂ -Graphene / CNF composite has a specific surface area similar to that of Graphene / CNF, but it can be seen that the photodegradation ability is superior in the MB photolysis experiment described below. It can be seen that the photocatalyst-graphene-carbon nanofiber composite of the present invention simultaneously exhibits the characteristics of the porous photocatalyst complex which removes MB by TiO ₂ photocatalytic activity while adsorbing MB by using the adsorption characteristics of pores. In addition, unlike conventional photocatalysts that react only in the ultraviolet region, graphene is introduced to create a new trap site between the band gaps of TiO ₂ , increasing the retention time of electrons and holes. It can be confirmed that the activity was shown.

Experimental Example 5 Evaluation of Visible Light Activity of Titanium Dioxide-Graphene-Carbon Nanofiber Composite (TiO ₂ -Graphene / CNF Composite)

In order to evaluate the visible light activity of the titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -Graphene / CNF composite) prepared in Example, a total of four types of samples (TiO) together with the comparative photocatalysts obtained in Comparative Examples 1 to 3 _2- Graphene / CNF complex, TiO ₂ / CNF, Graphene / CNF, CNF) was prepared and performed as follows, the results are shown in Figure 10.

Methylene blue (MB) dye was prepared at a concentration of 15 ppm to evaluate photocatalytic activity according to each concentration. 100 mL of the prepared solution and 0.1 g of a sample prepared in powder form were placed in a beaker and irradiated with a light source to observe dye degradation performance. The light source used for the evaluation of the photocatalytic activity was tested using Visible light (13W, 400-800nm, FRX13EX-D) as a light source.

After the reaction, 3 mL of the reaction solution was taken at intervals of 30 minutes to confirm the change in concentration of MB. The solution was separated using a 0.45 μm (Millipore millex filter) filtration membrane to obtain a pure solution containing no TiO ₂ particles. . The concentration of MB according to reaction time was measured by UV-Vis spectroscopy.

FIG. 9 is a graph showing MB photodegradation and photolysis reaction rates for a total of four samples in the visible region, and the 15 ppm MB removal efficiencies shown in FIG. 9 are summarized in Table 5 below.

TiO _2-
Graphene / CNF Graphene / CNF TiO ₂ -CNF CNF MB removal efficiency *
(30 minutes later) 100% 31.3% 31.3% 18.7% MB removal efficiency *
(After 180 minutes) 100% 35.0% 35.5% 21.3%

* MB removal efficiency =

MB decomposition efficiency of TiO ₂ -Graphene / CNF composite of the present invention showed the highest removal efficiency. In other words, the TiO ₂ -Graphene / CNF composite showed 100% MB removal efficiency in 30 minutes under visible light, but the graphene / CNF and TiO ₂ -CNF showed low degradation efficiency of about 35% after 180 minutes and CNF. In the case of, the lowest decomposition efficiency was 21.3%.

These experimental results show that the TiO ₂ -Graphene / CNF composite of the present invention exhibits high photocatalytic activity efficiency even in visible light having low energy, unlike other photocatalyst complexes.

The reason why the TiO ₂ -Graphene / CNF composite of the present invention exhibits high photocatalytic activity efficiency even in visible light is that nano-sized photocatalytic particles (TiO ₂ particles in the embodiment) are uniformly formed on the surface of the photocatalytic composite under the influence of graphene. As a result, the contact area with contaminants increases relatively, and since multi-layer graphene has its own characteristics as a semiconductor, it reduces the band gap and at the same time, the photocatalyst excited by the photocatalytic reaction ( In this case, it is expected that photocatalytic activity is increased by increasing the duration of electrons and holes by acting as an acceptor to hold electrons of TiO ₂ ).

Experimental Example 6: Repeated photoactive reaction of titanium dioxide-graphene-carbon nanofiber composite (TiO ₂ -Graphene / CNF composite)

The TiO ₂ -Graphene / CNF composite prepared in Example was subjected to the photoactivity reaction experiment. In spite of the application of 15 ppm higher than the MB concentration which is generally applied to the photoactivity evaluation, the TiO ₂ -Graphene / CNF composite was obtained in 30 minutes. It was confirmed through Experimental Example 4 described above that all 15 ppm of MB were removed. The photocatalytic activity was repeated and the results are shown in FIG. 10. In this experiment, visible light was used as a light source. After preparing 100 ppm of 15 ppm of MB, 0.1 g of photocatalytic composite powder was placed in a beaker and irradiated with a light source. When MB was removed 100% in the first cycle, MB was added to adjust the concentration to 15 ppm, and the decomposition experiment was repeated by examining the next visible light.

As shown in FIG. 10, in the TiO ₂ -Graphene / CNF composite of the present invention, 100% of 15 ppm of MB was removed until 4 cycles, and the photocatalytic activity was slightly decreased at 5 cycles.

From these experimental results, it can be predicted that each component constituting the TiO ₂ -Graphene / CNF composite obtained in the embodiment of the present invention performs the role described in Table 6 below.

TiO ₂ -Graphene / CNF Composite Graphene In combination with TiO ₂ and given to help uniformly disperse the TiO ₂ particles of nano size increases the efficiency of the photocatalytic activity.
ㆍ Graphene has the same characteristics as semiconductors and it has a high photocatalytic activity in visible light by increasing the duration of electrons and holes by narrowing the band gap of TiO2 and trapping electrons formed during photoexcitation reaction. Nano size TiO ₂ Electrons and holes are generated when light with energy above a certain bandgap occurs, and reactions such as oxidation of various organic substances occur through this electron-hole pair
Nano sized TiO2 shows photocatalytic reaction in visible light with energy lower than the band gap (3.2eV) of TiO2 due to quantum size effect. CNF  High specific surface area increases organic loading and adsorption and desorption rate, increasing reaction rate of photocatalytic activity

Although not disclosed in specific examples, the photocatalyst-graphene-carbon nanoparticle composite of the present invention including ZnO, WO ₃ , SnO ₂ , ZrO ₂ , and CdS, which is not titanium dioxide (TiO ₂ ) as a photocatalyst, may be prepared by doping with metal ions. It was found that the Schottky barrier has a higher visible light photocatalytic effect than Ag-TiO ₂ / CNF having a photocatalytic activity in visible light.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

Claims (14)

delete delete delete delete delete delete Preparing a graphene-containing spinning solution by dissolving carbon nanofiber precursors and graphene;
Preparing a graphene-containing precursor fiber by electrospinning the spinning solution;
Stabilizing the precursor fiber at 200 to 300 ° C. to produce graphene-containing flame resistant fiber;
Preparing a photocatalyst sol solution;
Coating the graphene-containing chloride resistant fiber by dipping the photocatalyst sol solution; And
Carbonizing the coated flame resistant fiber after drying,
The graphene-containing fat using solution is a photocatalyst-graphene-carbon nanofiber composite manufacturing method characterized in that it comprises 1 to 20% by weight of graphene relative to the carbon nanofiber precursor material.
delete Preparing a graphene-containing spinning solution by dissolving carbon nanofiber precursors and graphene;
Preparing a graphene-containing precursor fiber by electrospinning the spinning solution;
Stabilizing the precursor fiber at 200 to 300 ° C. to produce graphene-containing flame resistant fiber;
Preparing a photocatalyst sol solution;
Coating the graphene-containing chloride resistant fiber by dipping the photocatalyst sol solution; And
Carbonizing the coated flame resistant fiber after drying,
The step of preparing the graphene-containing emulsion using the photocatalyst-graphene-carbon nanofiber composite manufacturing method comprising the step of dispersing the graphene in the DMF using ultrasonic waves and dissolving PAN in the dispersion solution .
10. The method according to claim 7 or 9,
The coating step is performed by immersing the flame resistant fiber in the photocatalyst sol solution for 1 to 3 hours, and the carbonizing is performed by heating to 800 to 1000 ° C. The photocatalyst-graphene-carbon nano Fiber composite manufacturing method.
10. The method according to claim 7 or 9,
The carbon nanofiber precursor material is any one selected from the group consisting of polyacrylo nitrile (PAN), polyimide, polybenzimidazole (PBI), and pitch. -Graphene-carbon nano fiber composite manufacturing method.
10. The method according to claim 7 or 9,
The photocatalyst precursor material is ZnO, WO ₃ , SnO ₂ , ZrO ₂ , TiO ₂ , characterized in that it comprises any one selected from the group consisting of photocatalyst-graphene-carbon nanofiber composite manufacturing method.


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