KR20180028765A - Carbon nanofiber composite having three layer structure and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a carbon nano-fiber composite having a three-layer structure and a preparing method thereof. According to the present invention, the carbon nano-fiber composite having a three-layer structure includes: carbon nano-fibers; a photocatalyst layer capable of absorbing light formed on one surface of the carbon nano-fibers; and another photocatalyst layer for initiating an oxidation or reduction reaction of water formed on the other surface of the carbon nano-fibers. According to the present invention, the method for preparing carbon nano-fiber composite having a three-layer structure includes the steps of: (1) mixing a carbon fiber precursor material and a solvent to prepare a spinning solution; (2) obtaining carbon nano-fibers by electrospinning the spinning solution; (3) heating the carbon nano-fibers to stabilize the carbon nano-fiber; (4) carbonizing the stabilized carbon nano-fibers by heating the carbon nano-fibers in a nitrogen gas atmosphere; (5) coating a photocatalyst layer for absorbing light on one surface of the carbonized carbon nano-fibers; and (6) coating another photocatalyst layer for initiating the oxidation or reduction reaction of water on the other surface of the carbonized carbon nano-fibers.

Description

TECHNICAL FIELD [0001] The present invention relates to a carbon nanofiber composite having a three-layer structure and a method for manufacturing the carbon nanofiber composite.

The present invention relates to a carbon nanofiber composite having a three-layer structure and a method for producing the same, wherein a photocatalyst layer capable of absorbing light is coated on one surface of the carbon nanofiber having a mat shape, Layer structure of a carbon nanofiber composite coated with a photocatalyst layer capable of causing a reaction and a method of manufacturing the same.

Photovoltaic conversion photovoltaic technology absorbs sunlight to cause various oxidation and reduction reactions. Above all, the photocatalyst used must be capable of absorbing light in the visible light region which occupies most of the sunlight. The titanium dioxide photocatalyst most widely used in the photocatalyst absorbs light in the ultraviolet ray region of less than 5%, which does not absorb light in the visible ray region occupying most of the sunlight corresponding to the band gap of 3.0-3.2 eV. Recently, attention has been paid to other photocatalysts such as CdS, WO ₃ , and Fe ₂ O ₃ , which can absorb light in the visible light region because the band gap is small rather than titanium dioxide photocatalyst.

On the other hand, carbon nanofiber has a large specific surface area and fine porous structure as a carbon material having a graphite structure such as activated carbon, and thus is widely used as a carrier of a catalyst material, and recently it is also widely used as an electrode material such as a fuel cell or a secondary battery . Research has been conducted on composite carbon nanofibers for composite use of carbon nanofibers and photocatalyst materials for adsorption and decomposition of refractory organic contaminants (Korean Patent No. 10-0939938 and Korean Patent Laid- -0079470). These photocatalyst-containing carbon nanofiber structures are expected to be useful as filter materials for decomposing organic pollutants using photocatalysts, but they are basically designed to use ultraviolet light. In addition, research has been conducted on a CdS-carbon nanofiber composite material that uniformly forms a CdS photocatalyst layer on the surface of carbon nanofibers that can effectively generate a hydrogen generation reaction under irradiation with sunlight (Korean Patent No. 10-1598896) This is because the CdS-carbon nanofiber composite absorbs sunlight to produce environmentally friendly hydrogen.

Furthermore, in Korean Patent No. 10-1598896, CdS is coated on carbon nanofibers to absorb sunlight, thereby causing oxidation and reduction reactions. However, the CdS-carbon nanofiber composite disclosed in the above document has an advantage of being able to utilize the sunlight well, but the oxidation and reduction reactions take place in one place, and the oxidation and reduction products are mixed in one place. If the results are to be used individually, there is a disadvantage in that the separation process must be followed again.

Therefore, in the present invention, it is possible to effectively generate the hydrogen generation reaction by water decomposition under the irradiation of sunlight. At this time, electrons generated by absorbing sunlight can move through the carbon nanofibers, A carbon nanofiber composite having a three-layer structure capable of ultimately separating the oxidation and reduction reactions was successfully produced by succeeding in allowing the carbon nanofibers to occur on the opposite side of the fiber.

Korean Patent No. 10-0939938 Korean Patent Publication No. 10-2010-0079470

Accordingly, an object of the present invention is to provide a carbon nanofiber layer coated with a (photocatalytic) catalyst layer capable of absorbing sunlight on one surface of a carbon nanofiber layer and receiving electrons transferred from carbon nanofibers to the other surface of the carbon nanofiber layer, (Optical) catalyst layer that can form a three-layered carbon nanofiber composite.

Another object of the present invention is to provide a method for producing a carbon nanofiber composite having a three-layer structure.

In order to achieve the above-mentioned object of the present invention,

The present invention relates to carbon nanofibers; A photocatalyst layer capable of absorbing light formed on one surface of the carbon nanofiber; And a photocatalyst layer for causing an oxidation or reduction reaction of water formed on the other surface of the carbon nanofibers.

In one embodiment of the present invention, the carbon nanofibers may be in the form of a mat.

In an embodiment of the present invention, the average thickness of the carbon nanofibers is 200 to 1500 um, the average thickness of the photocatalyst layer capable of absorbing light is 50 to 150 um, and the photocatalyst layer May be 150 to 250 [mu] m.

In one embodiment of the present invention, the photocatalyst layer capable of absorbing light may have a hexagonal structure.

In an embodiment of the present invention, the photocatalyst layer causing the oxidation or reduction reaction of water may have an anatase crystal phase.

In one embodiment of the present invention, the carbon nanofibers are selected from the group consisting of polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene oxide (PEO), polyvinyl difluoride Carbon nanofibers formed from any one of carbon fiber precursors selected from polypyrrole, polyvinyldifluoride, and polypyrrole.

In one embodiment of the present invention, the light-absorbing photocatalyst layer may be CdS (Cadmium Sulfide), modified TiO ₂ (Titanium dioxide), ZnS (Zinc sulfide) or gC ₃ N ₄ (graphitic carbon nitride) have.

In one embodiment of the present invention, the photocatalyst layer to cause the water oxidation or reduction reaction may be a _{Pt-TiO 2 (Pt deposited TiO} 2), Pt (Platinum nanoparticles), RuO (Ruthenium oxide) or CoPi (Cobalt phosphate) have.

The present invention also provides a photocatalyst comprising the carbon nanofiber composite having the three-layer structure according to the present invention.

Further, the present invention provides a method for producing a carbon fiber precursor, comprising the steps of: (1) preparing a spinning solution by mixing a carbon fiber precursor material and a solvent; (2) electrospinning the spinning solution to obtain carbon nanofibers; (3) heating and stabilizing the carbon nanofibers; (4) carbonizing the stabilized carbon nanofibers by heating in a nitrogen gas atmosphere; (5) coating a photocatalyst layer capable of absorbing light on one surface of the carbonized carbon nanofibers; And (6) coating a photocatalyst layer which causes an oxidation or reduction reaction of water on the other surface of the carbonized carbon nanofibers. The present invention also provides a method for producing a carbon nanofiber composite having a three-layer structure.

In one embodiment of the present invention, the carbon fiber precursor material of the step (1) is selected from the group consisting of polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) Polyvinyldifluoride and polypyrrole, and may be contained in an amount of 5 to 15% by weight based on 100% by weight of the spinning solution.

In one embodiment of the present invention, the solvent of step (1) is selected from the group consisting of N, N-dimethylformamide, THF, tetrahydrofuran, gamma-butyroractone, N-methyl pyrrolidone, toluene, acetone and dimethylacetamide (DMAc) may be used.

In one embodiment of the present invention, the electrospinning of step (2) may be performed under an electric field of 15-25 kV.

In one embodiment of the present invention, the step (3) may be performed at a temperature of 200 to 250 ° C for 20 to 40 minutes under an oxygen atmosphere.

In one embodiment of the present invention, the carbonization in the step (4) is carried out by raising the temperature to 700 to 800 ° C at a heating rate of 5 to 7 ° C / min, maintaining the temperature at 700 to 800 ° C for 40 to 60 minutes The temperature is raised to 1200 to 1600 ° C at a heating rate of 5 to 7 ° C / min, and then the heating is continued for 60 to 70 minutes while maintaining the temperature at 1200 to 1600 ° C.

In one embodiment of the present invention, (5) the coating of the photocatalyst layer capable of absorbing light in phase, CdS (Cadmium sulfide), modified TiO ₂ (Titanium dioxide), ZnS (Zinc sulfide) or gC ₃ N ₄ (graphitic carbon nitride) may be coated on one surface of the carbon nanofibers to have an average thickness of 50 to 150 um.

In one embodiment of the present invention, the coating of the photocatalyst layer that generates the 6 stage of the water oxidation or reduction reactions Pt-TiO ₂ (Pt deposited TiO _2), (Platinum nanoparticles), (Ruthenium oxide), RuO Pt or CoPi (Cobalt phosphate) may be coated on the other surface of the carbon nanofibers to have an average thickness of 150 to 250 mu m.

In one embodiment of the present invention, the photocatalyst layer capable of absorbing light may have a hexagonal structure.

In an embodiment of the present invention, the photocatalyst layer causing the oxidation or reduction reaction of water may have an anatase crystal phase.

The three-layered carbon nanofiber composite coated with the photocatalyst layer according to the present invention comprises a mat type carbon nanofiber as a support, a photocatalyst layer capable of absorbing light is coated on one surface thereof, and a photocatalyst layer Or an (optical) catalyst capable of causing a reduction reaction, thereby providing a carbon nanofiber composite having a three-layer structure, thereby separating the oxidation and reduction reaction utilizing the photocatalyst. In this case, The electron transfer reaction can occur rapidly through the nanofiber layer, and thus the oxidation and reduction reactions can be separated so that they can occur in different layers.

FIG. 1 is a photograph showing a transmission electron microscope observation result of a carbon nanofiber composite material having a three-layer structure in which a (catalytic) catalyst layer prepared according to an embodiment of the present invention is coated on both surfaces of carbon nanofibers.
FIG. 2 shows X-ray diffraction analysis results of a carbon nanofiber composite having a three-layer structure coated with (photo) catalyst layers according to Comparative Examples and Examples of the present invention.
FIG. 3 is a graph comparing the amount of hydrogen produced by visible light irradiation of a carbon nanofiber composite having a three-layer structure coated with (optical) catalyst layers according to Comparative Examples and Examples of the present invention.
FIG. 4 is a graph comparing resistance values of carbon nanofiber composites of a three-layer structure coated with (photo) catalyst layers according to an exemplary embodiment of the present invention.
FIG. 5 is a graph comparing the amount of hydrogen generated for 3 hours under visible light irradiation according to the carbon nanofiber thickness of a carbon nanofiber composite having a three-layer structure coated with (optical) catalyst layer prepared according to an embodiment of the present invention.
6 is a schematic view of a carbon nanofiber composite having a three-layer structure according to the present invention.

Conventionally, the CdS-carbon nanofiber composite has advantages in that it can utilize the sunlight well, but since the oxidation and reduction reactions take place in one place, it is troublesome to use the oxidation or reduction products individually.

Accordingly, the inventors of the present invention first produced a carbon nanofiber composite having a three-layer structure capable of effectively generating a hydrogen generation reaction according to water decomposition under irradiation with sunlight.

The carbon nanofiber composite having the three-layer structure provided by the present invention is a carbon nanofiber; A photocatalyst layer capable of absorbing light formed on one surface of the carbon nanofiber; And a photocatalyst layer for causing an oxidation or reduction reaction of water formed on the other surface of the carbon nanofiber.

According to another aspect of the present invention, there is provided a method for producing a carbon nanofiber composite having a three-layer structure, comprising: (1) preparing a spinning solution by mixing a carbon fiber precursor material and a solvent; (2) electrospinning the spinning solution to obtain carbon nanofibers; (3) heating and stabilizing the carbon nanofibers; (4) carbonizing the stabilized carbon nanofibers by heating in a nitrogen gas atmosphere; (5) coating a photocatalyst layer capable of absorbing light on one surface of the carbonized carbon nanofibers; And (6) coating a photocatalyst layer for causing an oxidation or reduction reaction of water on the other surface of the carbonized carbon nanofibers.

A method for producing a carbon nanofiber composite having a three-layer structure will be described in detail.

First, prepare a spinning solution.

The carbon fiber precursor material used for preparing the spinning solution is not limited thereto, but may be selected from the group consisting of polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) Polyvinyldifluoride and polypyrrole, and may be contained in an amount of 5 to 15% by weight based on 100% by weight of the spinning solution. If the carbon fiber precursor is less than 5 wt%, there may be a problem in continuous fiber formation. If the carbon fiber precursor is more than 15 wt%, the viscosity of the spinning solution may be high and the nozzle may be clogged.

The solvents that can be used for the spinning solution include, but are not limited to, N, N-dimethylformamide, THF, Tetrahydrofuran, gamma-butyroractone ), N-methyl pyrrolidone, toluene, acetone, and dimethylacetamide (DMAc). The solvent may be selected from the group consisting of a polymer It melts.

When the spinning solution is produced, the spinning solution is electrospun to obtain carbon nanofibers.

At this time, the electrospinning can form carbon nanofibers as supports to form carbon nanofibers in the form of mat, and form carbon nanofiber supports having a diameter of several hundred nanometers.

Preferably, the electrospinning can be carried out under an electric field of 15 to 25 kV. If the electric field is less than 15 kV, there may be a problem of not being emitted as a yarn, and if the electric field exceeds 25 kV, There may be problems that can not be achieved.

Thereafter, the step of heating and stabilizing the carbon nanofibers is performed.

The stabilization step stabilizes the carbon nanofibers to carbonize the carbon nanofibers. The carbon nanofibers are stabilized by heating at 200 to 250 ° C for 20 to 40 minutes in an oxygen atmosphere. However, if the heating is carried out in a temperature range exceeding the heating temperature in the stabilization step, a problem may arise in obtaining stable carbon fibers in the subsequent carbonization step.

Next, the stabilized carbon nanofibers are carbonized by heating under a nitrogen gas atmosphere.

The carbonization step is carried out by raising the temperature to 700 to 800 ° C at a heating rate of 5 to 7 ° C / min, heating for 40 to 60 minutes while maintaining the temperature at 700 to 800 ° C, The temperature may be raised to 1200 to 1600 ° C at a heating rate, and then the mixture may be heated at a temperature of 1200 to 1600 ° C for 60 to 70 minutes.

On the other hand, if the temperature raising rate is less than 5 占 폚 / min, there may be a problem with the yield. If the temperature raising rate exceeds 7 占 폚 / min, there may be uneconomical problems. There is a problem that it is not achieved, and if it exceeds 800 ° C, there may be a problem on the CN structure. If the temperature for raising the second temperature is less than 1200 ° C, there may be a problem of removing nitrogen molecules, and if it exceeds 1600 ° C, there may be an uneconomical problem.

When the carbonization step is completed, the carbon nanofibers are coated with a photocatalyst on both surfaces of the carbon nanofibers. That is, a photocatalyst layer capable of absorbing light is coated on one surface of the carbonized carbon nanofibers, and a photocatalyst layer, which causes an oxidation or reduction reaction of water, is coated on the other surface of the carbonized carbon nanofibers.

The coating of the photocatalyst layer capable of absorbing light can be performed by coating CdS (Cadmium sulfide), modified TiO ₂ (Titanium dioxide), ZnS (zinc sulfide) or gC ₃ N ₄ (graphitic carbon nitride) on one surface of the carbon nanofiber and that the coating have a mean thickness of 50 ~ 150um preferably, the coating of the photocatalyst layer to cause the water oxidation or reduction reactions _{Pt-TiO 2 (Pt deposited TiO} 2), (Platinum nanoparticles), (Ruthenium oxide) RuO Pt or CoPi (cobalt phosphate) is preferably coated on the other surface of the carbon nanofiber so as to have an average thickness of 150 to 250 mu m.

The carbon nanofiber composite having the three-layer structure produced by the above-mentioned method is a carbon nanofiber; A photocatalyst layer capable of absorbing light formed on one surface of the carbon nanofiber; And a photocatalyst layer for causing an oxidation or reduction reaction of water formed on the other surface of the carbon nanofibers, wherein the carbon nanofibers have a mat shape.

In addition, the photocatalyst layer capable of absorbing light has a hexagonal structure, and the photocatalyst layer causing an oxidation or reduction reaction of the water has an anatase crystal phase.

The inventors of the present invention analyzed the amount of hydrogen produced by visible light irradiation in the carbon nanofiber composite having a three-layered structure prepared by the method of the present invention. As a result, it was found that carbon nanotubes containing no photocatalyst layer causing oxidation or reduction reaction of water It was confirmed that hydrogen generation reaction was not occurred in the carbon nanofiber composite without CdS layer, which absorbs visible light.

In addition, the present inventors have found that, in an embodiment of the present invention, as compared with the composite of Comparative Example 2 in which visible light is absorbed through a CdS layer and then oxidation and reduction reactions occur and hydrogen is generated by water decomposition through a reduction reaction, A carbon nanofiber composite having a three-layer structure in which a CdS layer is coated on one surface and a Pt-TiO ₂ layer is coated on the other surface is formed by a CdS photocatalyst absorbing light, passing by is well transmitted to the Pt-TiO ₂ on the other side, due to the electrons that are transmitted through a carbon nano-fiber layer on the Pt-TiO ₂ layer occurs and the hydrogen generation is the recombination rate of electrons and a major reduction in the process overall hydrogen production the Of the total population.

Further, in order to confirm whether the hydrogen production amount and the resistance value can be influenced by the thickness of the carbon nanofibers, the inventors of the present invention fabricated carbon nanofibers having various thicknesses and fabricated both surfaces by the above- After the carbon nanofiber composites were prepared, the amount of hydrogen production and the resistance value were analyzed.

As a result, it was confirmed that the amount of hydrogen production varies depending on the thickness of the carbon nanofibers layer, which serves to transfer electrons. As the thickness of the carbon nanofibers increases, the resistance value increases. Also, Respectively. In addition, analysis of whether these changes are related to the carbonization temperature revealed that they have higher resistance values at low carbonization temperatures.

Therefore, it can be seen from the above results that if the thickness of the carbon nanofibers in the carbon nanofiber composite having the three-layer structure of the present invention is too thick, the resistance value is increased and the hydrogen production amount can be reduced. Carbon nanofibers were most suitable.

The present invention also relates to a carbon nanofiber composite material having a three-layer structure according to the present invention, in which a photocatalyst layer capable of absorbing light on both surfaces of a carbon nanofiber, which is a stable support, and a photocatalyst layer causing oxidation or reduction reaction of water, The present invention has the technical advantage that hydrogen can be efficiently generated from water under irradiation with sunlight and that the oxidation and reduction reactions can be separated at the boundaries of the carbon nanofiber layer. Electrode or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited to these examples.

< Example  1>

CdS / CNF / Pt- TiO ₂  Three-tiered Carbon nanofiber  Manufacture of Composites

First, polyacrylonitrile (PAN), which is a material of a carbon fiber precursor, is added to a solvent of N, N-dimethylformamide (DMF) at a concentration of 10% by weight 10 g / 100 ml) to prepare a PAN solution. The PAN solution was then electrospun at an electric field of 20 kV to produce nanofibers.

Then, carbonization step is performed to make the nanofibers into carbon fibers. First, the step of oxidizing and stabilizing by heating at 250 ° C for 30 minutes in an oxygen atmosphere was performed. After the stabilization step is completed, nitrogen gas is injected into the nanofibers while the temperature is raised to 750 ° C at a heating rate of 5 ° C / min, heated for 1 hour while maintaining the temperature of 750 ° C, The temperature was gradually increased to 1400 ° C at a heating rate of 5 ° C, and the carbonization step was performed by heating for 1 hour while maintaining the temperature at 1400 ° C. Then, TiO ₂ (Pt-TiO ₂ ) light-impregnated with 5 wt% of platinum was coated on the surface of the carbon nanofibers subjected to the carbonization process, and the other surfaces of the carbon nanofibers thus carbonized were coated with CdS nanoparticles again . Pt-TiO ₂ and CdS nanoparticles were coated by doctor blade method. 20 mg of Pt-TiO ₂ or CdS nanoparticles was mixed with 260 mg of a polyethylene glycol solution (water: polyethylene glycol = 2: 1, weight ratio) to prepare a paste. After a certain amount of the paste was dropped on the surface of the carbon nanofibers, The mixture was poured to fill only one layer of the tape and then baked at 400 ° C for 30 minutes to completely oxidize the polyethylene glycol component to prepare a carbon nanofiber composite of CdS / CNF / Pt-TiO ₂ having the three-layer structure according to the present invention .

< Example  2>

CdS / CNF / Pt- TiO ₂  Three-tiered Carbon nanofiber  Manufacture of Composites

A carbon nanofiber composite was prepared in the same manner as in Example 1, except that the carbonization temperature was changed to 1100 ° C in the process of producing the carbon nanofiber composite having the three-layer structure of Example 1.

< Comparative Example  1>

To prepare a three-layered carbon nanofiber composite material, polyacrylonitrile (PAN), which is a material of a carbon fiber precursor, was added to a solvent of dimethylformamide (DMF) at a concentration of 10 wt% / 100 ml) to prepare a PAN solution. The PAN solution was then electrospun at an electric field of 20 kV to produce nanofibers.

Then, carbonization step is performed to make the nanofibers into carbon fibers. First, the step of oxidizing and stabilizing by heating at 250 ° C for 30 minutes in an oxygen atmosphere was performed. After the stabilization step is completed, nitrogen gas is injected into the nanofibers while the temperature is raised to 750 ° C at a heating rate of 5 ° C / min, heated for 1 hour while maintaining the temperature of 750 ° C, The temperature was gradually increased to 1400 ° C at a heating rate of 5 ° C, and carbonization was carried out by heating at 1400 ° C for 1 hour to produce carbonized carbon nanofibers (CNF).

< Comparative Example  2>

TiO ₂ (Pt-TiO ₂ ) light-impregnated with 5 wt% of platinum on the surface of the carbonized carbon nanofibers prepared in the procedure of Comparative Example 1 was coated by the doctor blade method of Example 1 to obtain CNF / Pt-TiO ₂ Carbon nanofiber composites were prepared.

< Comparative Example  3>

The CdS / CNF carbon nanocomposite was prepared by coating CdS nanoparticles on the surface of the carbonized nanofibers produced in the process of Comparative Example 1 by the doctor blade method of Example 1. [

The carbon nanocomposites prepared in the above Examples and Comparative Examples are summarized in Table 1 below.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 CdS × × ○ ○ ○ Carbon nanofiber ○ ○ ○ ○ ○ Carbonization temperature (℃) 1400 1400 1400 1400 1100 Pt-TiO ₂ × ○ × ○ ○ Manufactured
Carbon nanocomposite CNF CNF / Pt-TiO ₂ CdS / CNF CdS / CNF / Pt-TiO ₂ CdS / CNF / Pt-TiO ₂

< Experimental Example  1>

CdS / CNF / Pt- TiO ₂  The three-layer structure of the present invention Carbon nanofiber  Microscopic observation of the complex

As a result of microscopic observation of the carbon nanofiber composite having a CdS / CNF / Pt-TiO ₂ three-layer structure manufactured by the method of Example 1 of the present invention, as shown in FIG. 1, Coated with Pt-TiO ₂ particles of about 200 μm thickness on the other side.

Therefore, the present inventors have observed through the microscopic observation that the CdS layer is coated on one surface of the carbon nanofiber layer and the Pt-TiO ₂ layer is coated on the other surface of the carbon nanofiber layer, Fiber composite was well formed.

< Experimental Example  2>

Carbon nanofiber  X-ray diffraction analysis of complexes

X-ray diffraction analysis (Rigaku D / MAX-2500, 18 kV) was performed on carbon nanofibers prepared by the method of Example 1 and Comparative Example 1.

As a result of the analysis, as shown in FIG. 2, it was found that carbon nanofibers subjected to the carbonization process of Comparative Example 1 were amorphous graphitized by carbonization of the PAN precursor (26 (deg.) And 43 (deg.)). As a result, it was confirmed that the PAN polymer was a raw material for carbon nanofibers. On the other hand, CdS of hexagonal structure was observed in the CdS layer of Example 1, and a TiO ₂ structure having anatase crystallinity was observed in the Pt-TiO ₂ layer of Example 1.

< Experimental Example  3>

Analysis of hydrogen production by visible light irradiation

The carbon nanofiber composite prepared according to the above Examples and Comparative Examples was irradiated with visible light having a wavelength of 420 nm or more for 3 hours, and the average amount of generated hydrogen was measured.

As a result of the analysis, as shown in FIG. 3, in Comparative Example 2, no hydrogen generation occurred due to visible light irradiation. This is because there is no CdS photocatalyst that absorbs visible light, I can see that this does not happen at all. On the other hand, in Comparative Example 3, visible light was absorbed through a CdS photocatalyst that absorbs visible light, and then an oxidation and reduction reaction occurred. At this time, the water was decomposed by the reduction reaction to generate hydrogen. However, in the carbon nanofiber composite material of Example 1 having the three-layer structure according to the present invention, the hydrogen generation amount was about four times higher than that of Comparative Example 3. [ This is because the CdS photocatalyst absorbs light and the generated electrons pass through the carbon nanofiber layer to the Pt-TiO ₂ layer on the opposite side. Hydrogen generation occurred in the Pt-TiO ₂ layer due to the electrons transferred through the carbon nanofiber layer. In this process, the recombination ratio of electrons and electrons decreased, and the amount of generated hydrogen was increased.

< Experimental Example  4>

Carbon nanofiber layer  Resistance analysis by thickness

Further, the present inventors manufactured carbon nanofiber composites with different thicknesses of the carbon nanofibers in the course of manufacturing the composite of the present invention having a three-layer structure, and compared the resistance values thereof. At this time, the carbon nanofiber thicknesses were prepared so as to have the thicknesses shown in the following table, and the carbon nanofiber thicknesses were produced by the methods of Examples 1 and 2 except for the difference of the carbon nanofiber thicknesses. Since the electronic conductivity of the carbon nanofibers may be greatly affected by the carbonization temperature, the carbon nanofiber composites described in the following table were prepared under the thickness and different temperature conditions. Were analyzed.

As a result of the analysis, as shown in Table 2 and FIG. 4, the resistance value was increased as the thickness of the carbon nanofiber layer was increased in both Example 1 and Example 2, 2 showed higher resistance values.

< Experimental Example  5>

Carbon nanofiber layer  Analysis of hydrogen production by thickness

The degree of hydrogen production in the carbon nanofiber composites prepared in Experimental Example 4 was compared and analyzed.

As a result of the analysis, as shown in FIG. 5, as the thickness of the carbon nanofiber layer became thicker, the hydrogen generation amount decreased, and the decrease in the generation amount was more prominent in Example 2. This is considered to be because the resistance was much higher as shown in Fig. 4 because Example 2 was manufactured at a lower carbonization temperature condition, and the amount of hydrogen generation was also lower than that of Example 1. Fig.

As described above, the carbon nanofiber composite of the present invention having the CdS / CNF / Pt-TiO ₂ three-layer structure produced by the method of the present invention exhibits a considerable amount of hydrogen production due to the presence of the CdS layer under visible light irradiation of 420 nm or more may be, and the Pt-TiO ₂ layer on the opposite side exist as the reduction by electron is actively by to take place, an electron transfer reaction via the carbon nano fiber layer to a support role in the Pt-TiO ₂ layer taking place very quickly, thus The oxidation and reduction reactions were separated from each other and could be widely used for electrodes for photoelectrochemical energy conversion.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (19)

Carbon nanofibers;
A photocatalyst layer capable of absorbing light formed on one surface of the carbon nanofiber; And
And a photocatalyst layer for causing an oxidation or reduction reaction of water formed on the other surface of the carbon nanofiber.
A carbon nanofiber composite having a three-layer structure. The method according to claim 1,
Wherein the carbon nanofibers are in the form of a mat. The method according to claim 1,
The average thickness of the photocatalyst layer capable of absorbing light is 50 to 150 um and the average thickness of the photocatalyst layer causing oxidation or reduction reaction of the water is 150 to 250 um Carbon nanofiber composite having a three-layer structure. The method according to claim 1,
Wherein the photocatalyst layer capable of absorbing light has a hexagonal structure. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt; The method according to claim 1,
Wherein the photocatalyst layer causing the oxidation or reduction reaction of water has an anatase crystal phase. The method according to claim 1,
The carbon nanofibers may be selected from among polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene oxide (PEO), polyvinyldifluoride, and polypyrrole Wherein the carbon nanofibers are carbon nanofibers formed from any one carbon fiber precursor. The method according to claim 1,
Wherein the photocatalyst layer capable of absorbing the light is at least one selected from the group consisting of Cadmium sulfide (CdS), modified TiO ₂ (Titanium dioxide), ZnS (zinc sulfide) or gC ₃ N ₄ (graphitic carbon nitride) Nanofiber composite. The method according to claim 1,
Wherein the photocatalyst layer causing the oxidation or reduction reaction of water is Pt-TiO ₂ , Pt (Platinum nanoparticles), RuO (Ruthenium oxide) or CoPi (Cobalt phosphate). A photocatalyst comprising a carbon nanofiber composite having a three-layer structure according to any one of claims 1 to 8. (1) preparing a spinning solution by mixing a carbon fiber precursor material and a solvent;
(2) electrospinning the spinning solution to obtain carbon nanofibers;
(3) heating and stabilizing the carbon nanofibers;
(4) carbonizing the stabilized carbon nanofibers by heating in a nitrogen gas atmosphere;
(5) coating a photocatalyst layer capable of absorbing light on one surface of the carbonized carbon nanofibers; And
(6) coating a photocatalyst layer for causing an oxidation or reduction reaction of water on the other surface of the carbonized carbon nanofibers; and
A method for producing a carbon nanofiber composite having a three-layer structure. 11. The method of claim 10,
The carbon fiber precursor material in the step (1) may be at least one selected from the group consisting of polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyethylene oxide (PEO), polyvinyldifluoride Polypyrrole, and is contained in an amount of 5 to 15% by weight based on 100% by weight of the spinning solution. 11. The method of claim 10,
The solvent in the step (1) may be selected from the group consisting of N, N-dimethylformamide, THF, G-butyroractone, N-methylpyrrolidone Wherein the solvent is at least one selected from the group consisting of methyl pyrrolidone, toluene, acetone and dimethylacetamide. 11. The method of claim 10,
Wherein the electrospinning of step (2) is carried out under an electric field of 15-25 kV. 11. The method of claim 10,
Wherein the step (3) is performed under an oxygen atmosphere at a temperature of 200 to 250 ° C for 20 to 40 minutes. 11. The method of claim 10,
The carbonization in the step (4) is carried out by raising the temperature to 700 to 800 ° C at a heating rate of 5 to 7 ° C / min, heating it for 40 to 60 minutes while maintaining the temperature at 700 to 800 ° C, The temperature is raised to 1200 to 1600 占 폚 at a heating rate of 占 폚 / min, and then the mixture is heated for 60 to 70 minutes while maintaining the temperature at 1200 to 1600 占 폚. 11. The method of claim 10,
The coating of the photocatalyst layer capable of absorbing light in the step (5) may be carried out by coating CdS (Cadmium sulfide), modified TiO ₂ (Titanium dioxide), ZnS (sulfide) or gC ₃ N ₄ (graphitic carbon nitride) Lt; RTI ID = 0.0 &gt; 50-150 &lt; / RTI &gt; um. 11. The method of claim 10,
The coating of the photocatalyst layer causing the oxidation or reduction reaction of water in the step (6) is performed by coating Pt-TiO ₂ , Pt (platinum nanoparticles), RuO (Ruuthenium oxide) or CoPi (cobalt phosphate) &Lt; / RTI &gt; to 250 &lt; RTI ID = 0.0 &gt; um. &Lt; / RTI &gt; 11. The method of claim 10,
Wherein the photocatalyst layer capable of absorbing light has a hexagonal structure. 11. The method of claim 10,
Wherein the photocatalyst layer causing the oxidation or reduction reaction of water has an anatase crystal phase.

Images