KR101440850B1 - Method for preparing three-dimensional graphene nano-networks and application thereof - Google Patents

Abstract

(1) depositing colloidal silica on a substrate to form a three-dimensional colloidal silica structure; (2) filling the three-dimensional colloidal silica structure with a solution containing a solid carbon source for graphene growth and a metal precursor; (3) heating the three-dimensional colloidal silica structure packed with the solution to 700 to 1200 占 폚 under hydrogen gas to form a nano-foam structure containing metal; And (4) removing the metal in the graphene of the colloidal silica and the nano foam structure. The present invention relates to a method of manufacturing a three-dimensional graphene nano-network, The method of manufacturing a fin does not require a transfer process causing toxicity or toxic carbon gas, and the graphene of the three-dimensional nano foam structure manufactured according to the method of the present invention can be used as a dye-sensitized solar cell (DSSC ). ≪ / RTI >

Description

[0001] METHOD FOR PREPARING THREE-DIMENSIONAL GRAPHENE NANO-NETWORKS AND APPLICATION THEREOF [0002]

The present invention relates to a method of mass-producing a three-dimensional graphene nano-network (3D-GN) on an inert substrate in a large area and its application.

Graphene is a flat sheet of one atom thick, densely packed with sp ² -bonded carbons in a honeycomb crystal lattice and has high optical transparency, good electrical conductivity, high flexural and mechanical stability, a large theoretical specific surface area, (Zhang, Y .; Tan, Y.-W .; Stormer, HL; Kim, P. Nature 2005, 438, (7065), 201). For the production of graphene sheets having excellent properties, chemical grafting of oxide grains, liquid-phase ultrasonic peeling of graphite, epitaxial growth of SiC or metal phase, and chemical vapor deposition (CVD) ) Growth are being exploited.

The growth of graphene on a metal film by CVD through a mechanism of dissolution and separation of carbon at the surface of the metal catalyst has excellent conductivity due to small defects and relatively large area size. However, CVD growth in metal films has the potential problems that the formation of single-crystalline graphene is limited to a two-dimensional (2D) plane and can only produce small quantities. The possibility of a more sophisticated 3D graphene nanowire network (3D-GN) at the bulk scale is achieved through the use of energy-related materials, heat sinks and heat sinks with large surface area, excellent high electrical / thermal conductivity, Can make important progress in the cell culture plate.

For example, a 3D graphene network grown in a 3D nickel frame has excellent mechanical strength, supercapacitance, and thermal conductivity due to the nature of the 3D structure. However, the size of the structure produced in this way is limited to the size of the nickel frame, is limited to a few hundred micrometers, and can interfere with the potential application of 3D graphene. As a well established method, copper and nickel have been commonly used as metal catalysts for CVD growth of graphene, and recently, the growth of multilayer graphene films in an iron-based catalyst widely used for the growth of carbon nanotubes There was little progress in success. Using iron as a catalyst for graphene growth is likely to become more feasible and attractive as it is the fourth most common element of the earth's crust and is non-toxic, inexpensive, and easy to remove. will be.

3D (3D) bi-continuous structures have been widely applied in photonic crystals, MEMS, biosensors, and tissue engineering due to the controlled periodicity, wide surface area, and effectiveness of three-dimensional reactions to external stimuli Jang, J.-H .; Jhaveri, SJ; Rasin, B .; Koh, C .; Ober, CK; Thomas, EL Nano Lett. 2008, 8 (5), 1456, and literature Jang, J.-H .; Ullal, CK; Gorishnyy, T .; Tsukruk, VV; Thomas, EL Nano Lett. 2006, 6, (4), 740.].

The potential of a 3D network can be expected to be a multifunctional material platform when combined with many of the outstanding properties of graphene. For example, a three-dimensionally connected graphene network can be an ideal structure as an electrode, supercapacitor or catalyst substrate because it provides a large surface area and high conductivity benefits. Besides the high specific surface area, the performance of the supercapacitor is equally important, such as high electrical conductivity, proper pore size and distribution, and electrochemical, thermal and mechanical stability. In consideration of these requirements, porous carbonaceous materials have been proposed as materials for electric double layer capacitors (EDLC), but most porous carbonaceous materials having a high specific surface area have a low conductivity, It is difficult to apply. On the other hand, graphene provides an ideal EDLC material due to its high electrical conductivity, excellent chemical and mechanical stability, and extremely wide surface area. However, parameter values such as electrical conductivity and surface area need to be realized at least to some extent.

On the other hand, graphene has potential as a novel material that can be used as the counter electrode of a fuel-responsive solar cell (DSSC). DSSC is a low cost photovoltaic system that can directly convert solar energy into electrical energy with high energy conversion efficiency, and DSSC is one of the most promising alternative renewable energy devices in that it is a low cost and measurable process. Typical DSSCs generally include a dye, an electrolyte comprising a redox couple, a broadband bandgap nanocrystalline TiO ₂ as a working electrode, and an opposing electrode, as major components. Until now, inefficient Pt has been regarded as the most excellent counter electrode material in DSSC due to its high stability, conductivity and excellent electrochemical activity, and only a few materials have properties comparable to Pt. Therefore, it is crucial to realize an inexpensive and inexpensive DSSC to find an excellent counter electrode material having superior performance to Pt.

Recent studies have reported that some carbon materials could replace Pt due to their low cost, high conductivity and corrosion resistance to oxidation-reduction pairs, but their performance has not yet reached Pt. Given this, graphene is similar in many excellent properties to conventional carbon materials, and has potential as a novel material that can be used as the counter electrode of DSSC. The present inventors have found that two important characteristics of graphene's high conductivity and a large surface area that can be achieved by the formation of a double continuous three-dimensional network of graphenes are to improve the performance of the latest Pt replaceable counter electrode (CE) in DSSC It can be effectively developed.

Thus, the present inventors have found that the use of an iron precursor solution process, a dual continuous 3D-GN structure grown through an inorganic CVD technique, which has dimensional extensibility and mass production capability and can potentially produce grains of any arbitrary shape Of the present invention.

Zhang, Y .; Tan, Y.-W .; Stormer, H. L .; Kim, P. Nature 2005, 438, (7065), 201) Jang, J.-H .; Jhaveri, S. J .; Rasin, B .; Koh, C .; Ober, C. K .; Thomas, E. L. Nano Lett. 2008, 8, (5), 1456 Jang, J.-H .; Ullal, C. K .; Gorishnyy, T .; Tsukruk, V. V .; Thomas, E. L. Nano Lett. 2006, 6, (4), 740.

It is an object of the present invention to provide a method and an application for reliably and directly producing a three-dimensional graphene nano-network (3D-GN) over a large area over an inert substrate.

In order to achieve the above object,

(1) laminating colloidal silica on a substrate to form a three-dimensional colloidal silica structure;

(2) filling the three-dimensional colloidal silica structure with a solution containing a solid carbon source for graphene growth and a metal precursor;

(3) heating the three-dimensional colloidal silica structure packed with the solution to 700 to 1200 占 폚 under hydrogen gas to form a nano-foam structure containing metal; And

(4) removing the metal in the graphene of the colloidal silica and the nano foam structure.

To provide a method of fabricating a three-dimensional graphene nano-network.

In addition, the present invention provides a 3D graphene nano-network manufactured by the above method, a supercapacitor including the same, and a dye-sensitized solar cell (DSSC).

The method of manufacturing a three-dimensional graphene nano-network according to the present invention is a simple and economical method that does not require a transfer process or toxic carbon gas that causes defects, Can be usefully used in the manufacture of nano-networks.

In addition, the 3D graphene nano-network fabricated according to the method of the present invention can be usefully used for manufacturing a supercapacitor or a dye-sensitized solar cell (DSSC).

1 is a diagram schematically showing an example of a method of manufacturing a three-dimensional graphene nano-network according to the present invention.
FIG. 2 is a photograph for confirming the shape of a 3D graphene network (3D-GN) according to an embodiment of the present invention. FIG. 2 is a scanning electron microscope (SEM) image of a PVA-FeCl ₃ / Photo (a); SEM photo (b) of low-density 3D-GN after removal of iron / CS after growth of graphene; A transmission electron microscope (TEM) photograph of the 3D-GN near the edge (c); (D) an enlarged view of one 3D-GN unit cell; And a diffraction photograph (e) of a selected region of the edge of one graphene unit cell.
FIG. 3 is a photograph showing a 3D-GN (a) and a film (b, c) in powder form produced by drop-casting and spin coating; Raman spectra (d) of 3D-GN grown by bulk CVD; XPS spectrum (e) of C in a film of 3D-GN grown by bulk CVD; TEM photograph of 3D-GN (f); And three-layer 3D-GN.
4 is a TEM photograph of 3D-GN photographed in different regions.
(A), 3D-GN-3 (b), 3D-GN-4 (c) and 3D-GN-5 (d) are graphs showing electrical conductivities of the 3D- .
GN-3 (b), 3D-GN-4 (c) and 3D-GN-5 (d) are graphs showing electrical conductivities of the 3D- .
FIG. 7 is a graph showing the BET analysis results of 3D-GN having a pore size of 30 nm, and the inset shows a void distribution curve, and the table shows concrete numerical values.
8 is a PVA-FeCl ₃ / X- ray of the annealing before the SC (red) and after (white) diffraction (XRD) and X- ray photoelectron (XPS) spectrum, a) the untreated iron chloride hexahydrate (FeCl ₃ · 6H ₂ O) (black) and an XRD of an annealed film of PVA-FeCl ₃ / CS composite (iron-containing 3D-GN) (red); And b) to d) XPS spectra of Fe, Cl and C in a film with a FeCl ₃ concentration of 350 phr.
9 is a Raman spectrum of 3D-GN grown by CVD, comprising: a) Raman spectra at various composition ratios and Raman spectrum of untreated PVA after H ₂ environment, annealed at 1000 ° C; And b) Raman spectra of 3D-GN grown on various substrates.
10 is a thermogravimetric analysis (TGA) result of 350 phr of PVA / FeCl ₃ .
11 is a graph showing I _D / I _G and I _2D / I _G as a function of FeCl ₃ .6H ₂ O concentration.
FIG. 12 is a graph showing the electrochemical performance of a 3D-GN type supercapacitor. FIG. 12 is a graph showing a cyclic voltammetric curve with different scan speeds; b) Capacitance change at various scan rates; c) charging / discharging curves when discharging current density is different; d) Nyquist impedance of 3D-GN; e) Capacitance retention table according to number of cycles; And f) plotting the specific capacitance of the EDLC electrode obtained from the various methods.
FIG. 13 is a graph showing the photovoltaic performance of DSSC using 3D-GN CE and Pt CE in AM 1.5 intensity illumination. FIG. 13 is a schematic diagram (a), a photocurrent-voltage (IV) curve (b) of DSSC using 3D- , An electrochemical impedance spectroscopy (EIS) curve (c), and an incident photon-to-electron conversion efficiency (IPCE) spectrum (d).
FIG. 14 is a graph comparing p-doped 3D-GNs at various contents of nitrogen atoms, showing photocell performance (a) of DSSC using 3D-GN CE and Pt CE under a light source of AM 1.5, The cyclic voltammogram (c) and the EIS curve (d) of the iodine species in the DSSC cell at a scan rate of 50 mV / s, Shows an equivalent circuit suitably used for data.
15 is a Tafel curve of symmetric dummy cells of Pt, untreated 3D-GN, 3D-GN-3, 3D-GN-4, and 3D-GN-5.
16 is an IPCE spectrum of a DSSC having CE of Pt, untreated 3D-GN, 3D-GN-3, 3D-GN-4, and 3D-GN-5.
17 is a graph showing the performance stability of DSSC having CE of Pt, untreated 3D-GN, and P-doped 3D-GN.

A method for fabricating a three-dimensional graphene nano-network according to the present invention comprises:

(1) laminating colloidal silica on a substrate to form a three-dimensional colloidal silica structure;

(2) filling the three-dimensional colloidal silica structure with a solution containing a solid carbon source for graphene growth and a metal precursor;

(3) heating the three-dimensional colloidal silica structure packed with the solution to 700 to 1200 占 폚 under hydrogen gas to form a nano-foam structure containing metal; And

(4) removing the colloidal silica and the metal in the graphene of the nano foam structure.

In the present invention, the term "three-dimensional graphene nano-network" refers to a structure in which graphenes on a two-dimensional plane having nano unit thickness (atomic unit thickness) Dimensional network structure).

In step (1), colloidal silica is laminated on the substrate to form a three-dimensional colloidal silica structure.

When the colloidal silica is uniformly dispersed in a pure solvent and then the solvent is removed, the colloidal silica is self-assembled and stacked in a hexagonal shape in order to maintain the thermodynamically most stable state (lowest energy state). That is, the three-dimensional colloidal silica structure is self-assembled on a substrate by face-centered cubic (FCC), by a single crystalline opal and a colvin's method, ).

Examples of the substrate include quartz, Al ₂ O ₃ , GaN, and SiO ₂ / Si substrates. The thickness ranges from 100 to 1,000 nm, from 200 to 800 nm, from 300 to 600 nm, or from 400 to 500 nm Lt; / RTI >

The colloidal silica may have a particle size of 10 to 300 nm, 20 to 250 nm, or 30 to 220 nm, and the 3-dimensional colloidal silica structure may have a thickness of 0.1 to 6 탆, 0.5 to 5 탆, or 1 to 4 탆 As shown in FIG.

In step (2), the three-dimensional colloidal silica structure is filled with a solution containing a solid carbon source for graphene growth and a metal precursor.

Wherein the surface of the colloidal silica constituting the three-dimensional colloidal silica structure is formed by uniformly applying the solid carbon source for graphene growth and the metal precursor contained in the solution filled in the three-dimensional colloidal silica structure, The surface -OH group may be activated by an inorganic acid such as sulfuric acid (H ₂ SO ₄ ).

Examples of the solid carbon source for graphene growth include polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), and mixtures thereof. Preferably, polyvinyl alcohol have.

The metal precursor may be a nickel precursor, a copper precursor, an iron precursor or a mixture thereof. Specific examples thereof include nickel nitrate hexahydrate {Ni (NO ₃ ) ₂ .6H ₂ O}, nickel acetate {Ni (CH ₃ COO) ₂ , Nickel precursors such as nickel sulfate hexahydrate (NiSO ₄ .6H ₂ O), nickel chloride hexahydrate (NiCl ₂ .6H ₂ O), copper precursors such as copper chloride hexahydrate (CuCl ₂ .6H ₂ O) (FeCl ₃ .6H ₂ O), preferably a nickel precursor such as nickel nitrate hexahydrate, nickel acetate, nickel sulfate hexahydrate, nickel chloride hexahydrate, and more preferably May be nickel chloride hexahydrate.

For example, when a PVA is used as the solid carbon source for graphene growth and a nickel precursor, a copper precursor, or an iron precursor is used as the metal precursor, the electrostatic interaction between the hydroxy group of the PVA and the metal ion contained in the solution Whereby the PVA and the metal precursor can be more uniformly dispersed.

The solid carbon source for graphene growth and the metal precursor may be in a weight ratio of 1: 2 to 1: 4, preferably 1: 3 to 1: 3.5. By including the solid carbon source and the metal precursor in the weight ratio, the amount of the amorphous carbon that can be used as the solid carbon material in the subsequent graphene growth step can be minimized.

Examples of the coating method include spin coating, die coating, gravure coating, micro gravure coating, comma coating, roll coating, dip coating, spray coating and the like, preferably spin coating or spray coating .

In step (3), the three-dimensional colloidal silica structure filled with the solution is heated to 700 to 1,200 占 폚 under hydrogen gas to form a nano-foam graphene structure containing the metal.

According to the heating, the formation of graphene having a nano foam structure containing a metal from the solution may be performed by chemical vapor deposition (CVD).

When the three-dimensional colloidal silica structure filled with the solution is heated (annealed) at a high temperature of 700 to 1,200 ° C, preferably 800 to 1,100 ° C, and more preferably 950 to 1,050 ° C under hydrogen gas, Carbonization of the carbon source contained in the colloidal silica structure is induced to form a nano foam structure. In addition, the solution can reduce the metal ions included in the filled three-dimensional colloidal silica structure. For example, nickel ions (II) can be converted into nickel (0), copper ions (II) The iron ion (III) can be reduced to iron (0).

That is, during the carbonization process of the mixture of the polymer and the metal precursor, which is a solid carbon source for graphen growth, the organic material is lost and nanopores of the nano foam structure are produced. Reduced metal and carbonized C in a three-dimensional nanoframe frame produced by pyrolysis under hydrogen gas are used as catalysts and solid carbon materials for graphene growth in CVD processes, respectively.

In step (4), the metal in the graphene of the colloidal silica and the formed nano foam structure is removed.

In the step (4), the colloidal silica and the metal may be removed using an etchant. Since the colloidal silica and the metal are dissolved and removed in the etchant, only the three-dimensional nano foam structure remains on the substrate.

The etchant may be a solution of hydrofluoric acid, hydrochloric acid, sulfuric acid, ammonium persulfate, or a mixture thereof.

Preferably, the colloidal silica using the etchant and the substrate upon removal of the metal may be removed together to obtain a freestanding three-dimensional nano foam structure graphene.

The above-described three-dimensional graphene nano-network fabrication method of the present invention requires only spin coating of a solution containing a carbon source and a metal precursor in place of a pre-deposition process of expensive metal catalysts, It has the advantage of using commonly used polymers instead of toxic CH ₄ or C ₂ H ₂ gas.

Fig. 1 is a view schematically showing an example of a method for producing a three-dimensional graphene nano-network according to the present invention.

Referring to FIG. 1, the manufacturing process of the 3D-GN can be expressed in four steps.

In step (I), a surface-activated three-dimensional colloidal silica structure is formed to a thickness of 3 탆 on a SiO ₂ / Si substrate with a thickness of 300 nm by surface treatment with sulfuric acid. In step (II), the three-dimensional colloidal silica structure is filled with a PVA / FeCl ₃ solution. In step (III), the three-dimensional colloidal silica structure filled with the PVA / FeCl ₃ solution is heated to 1,000 ° C in a quartz tube. In step (IV), the colloidal silica and the metal are removed by the HF / HCl solution leaving a 3D-GN structure on the SiO ₂ / Si substrate.

As such, the method of the present invention provides a unique and direct method of producing a three-dimensional graphene nano-network (3D-GN) consisting of several layers grown on a substrate by CVD.

According to the method of the present invention, a three-dimensional graphene nano-network can be manufactured reliably and directly.

Further, the three-dimensional graphene nano-network of the present invention has dozens of layers depending on the lamination conditions.

The 3D graphene nano-network fabricated according to the method of the present invention can be usefully used as an opposite electrode material of a dye-sensitized solar cell (DSSC).

Example

≪ Preparation of three-dimensional colloidal silica structure >

Colloidal silica was dispersed in distilled water to a concentration of 10% by weight to prepare a dispersion solution. The prepared dispersion solution was uniformly coated on a SiO ₂ / Si substrate with a thickness of 300 nm by spin coating (3,000 rpm / min) to deposit colloidal silica, and the solution was removed. The process of applying the dispersion solution was repeated 5 times, and then surface-treated with 10 M sulfuric acid to form a surface activated 3-dimensional colloidal silica structure having a thickness of 3 탆.

≪ CS / PVA-FeCl ₃ · 6H ₂ O 3-dimensional structure >

Polyvinyl alcohol (PVA, Mw = 31,000 to 50,000) and FeCl ₂ .6H ₂ O were purchased from Aldrich Chemical Company and used without further purification. After dissolving the PVA (10% by weight) at 90 ℃ in deionized water, FeCl ₃ · mixed in (parts per hundred parts of resin) by weight 6H ₂ O 100, 200, 350 and 600 phr%.

The three-dimensional colloidal silica structure prepared through the above item < Production of a three-dimensional colloidal silica structure > was filled with PVA / FeCl ₃ . Any impurities in the solution were filtered through a 0.2 탆 cellulose acetate syringe filter and then spin-coated onto a 300 nm SiO ₂ / Si substrate. The fabricated PVA / FeCl ₃ filled three-dimensional colloidal silica structure was dried in a vacuum oven for one day. The 3D-graphene nanowire network (3D-GN) was immersed in a 20 mol% HNO ₃ solution for 30 min to improve the conductivity for the measurement of supercapacitance and washed with DI water to remove p- p-doping).

<Fabrication of 3D graphene nano-network 1>

The prepared three-dimensional colloidal silica structure filled with PVA / FeCl ₃ was placed in a quartz tube (Scientech Co.) having an outer diameter of 120 mm, and the resultant was immersed in an atmosphere of 4 Torr H ₂ (100 sccm) / Ar at 20 ° C / Heated to 1,000 DEG C at a heating rate of 1 minute, and then placed (is annealed) for 30 minutes under isothermal condition. After annealing, the sample was cooled to ambient temperature. Then, the SiO ₂ substrate and the iron were simultaneously removed by moving the 3D-GN / Fe on the 300 nm SiO ₂ / Si substrate for 48 hours on a buffer oxide etchant (BOE) composed of HF (5%) and HCl (3% .

<Fabrication of 3D graphene nano-network 2>

The prepared three-dimensional colloidal silica structure filled with PVA / FeCl ₃ was placed in a quartz tube (Scientech Co.) having an outer diameter of 120 mm, and the resultant was immersed in an atmosphere of 4 Torr H ₂ (100 sccm) / Ar at 20 ° C / Heated to 1,000 DEG C at a heating rate of 1 minute, and then placed (is annealed) for 30 minutes under isothermal condition. After annealing, the sample was cooled to ambient temperature. 3D-GN / Fe on the 300 nm SiO ₂ / Si substrate was immersed in HF (10%) for 3 hours and immersed in HCl (10%) for 12 hours to simultaneously remove the SiO ₂ substrate and iron.

<Fabrication of 3D graphene nano-network paste>

50 mg of 3D-GN was dispersed in 30 ml of pure ethanol and then 2.75 g of terpineol was added. Ethyl cellulose (0.5 g: 5 g of a 10% solution in ethanol) was added, and then the ethanol was evaporated in an oven at 120 캜 for 5 hours. 4 ml of IPA was added to the dry paste to adjust the viscosity to an appropriate level.

<Production of DSSC>

TiO ₂ paste (18NR-T, manufactured by Dyesol DSL Co., Ltd.) was coated on a TiCl ₄ -treated FTO glass with a doctor blade to a thickness of 40 mM and then dried at 120 ° C for 10 minutes. Then, the coating film was sintered at 500 DEG C for 15 minutes. The doctor blade process (coating, drying, annealing) using the paste was repeated to produce working electrodes of appropriate thickness. The TiO ₂ coating film was treated with 40 mM TiCl ₄ solution at 70 ° C for 30 minutes, rinsed with water and ethanol, and sintered at 500 ° C for 30 minutes. A TiO ₂ electrode having an area of 0.21 cm ² (3 mm ×× mm) was immersed in a 0.5 mM N719 dye solution (manufactured by Solaronix) dissolved in pure ethanol, and left at room temperature for 24 hours.

In order to produce a 3D-GN counter electrode, a 3D-GN paste was coated on an FTO glass, placed in an oven at 400 DEG C for 5 minutes, and then repeated four times. In the case of the Pt counter electrode, a 40 mM H ₂ PtCl ₆ / IPA solution was spin-coated on the FTO glass several times and then sintered at 500 ° C. for 30 minutes.

Dye adsorption TiO ₂ The photoelectrode and the counter electrode (Pt, 3D-GN) were assembled into a sandwich-type cell made of 60 占 퐉 hot melt slurries (manufactured by Solaronix). 0.03 M I ₂ (Sigma Aldrich), 0.1 M guanidinium thiocyanate (Sigma Aldrich) in a mixture of acetonitrile and valeronitrile (volume ratio 85:15), 0.6 M 1- An electrolyte composed of butyl-3-methylimidazolium iodide (manufactured by Sigma Aldrich) and 0.5 M 4-tert-butylpyridine (manufactured by Sigma Aldrich) was injected through the hole on the back surface of the counter electrode.

Characterization of 3D-GN

The structure of the prepared sample (3D-GN) was confirmed by SEM (Nova Nano-SEM 230, 10 kV), TEM (JEM-2100, 200 kV) and Raman spectroscope (WITec, alpha300R, excited by 532 nm laser) Respectively. The X-ray spectroscopic measurement was carried out at 20 DEG to 80 DEG using a high-power X-ray diffractometer (D / MAZX 2500V / PV, manufactured by Rigaku Corporation). The surface area was confirmed by the BET (Brunauer-Emmett-Teller) method using an ASAP 2000 surface area meter (manufactured by Micrometerics Instrument).

The sheet resistance of the prepared sample (3D-GN) was measured by a 4-point probe using a sheet resistance meter (FPP-RS8, pin spacing 1 mm, pin radius 100 탆, manufactured by Dasol-ENGENE). At this time, the manufactured sample (3D-GN) was mechanically milled and then pressed (1,000 kg / cm ² ) to measure the resistance of the powder form of the 3D-GN to have a diameter of 13 mm, 50 탆 pellets and 7 탆 thick pellets were prepared. The resistance values between the film form and the powder form did not show any significant difference. The pellets consisted of 80 wt% 3D-GN, 10 wt% acetylene black, and 10 wt% PVDF.

Electrochemical measurement 1: <supercapacitor electrode>

The electrochemical characteristics of the supercapacitor electrode were measured in a range of -0.2 to 0.8 V at room temperature using a three-electrode system using cyclic voltammetry using a computer controlled electrochemical interface (SI 1287, manufactured by Solartron) Respectively. 1M H ₂ SO ₄ in 3D-GN, platinum mesh, Ag / AgCl and acetonitrile (ACN) was used as a working electrode, a counter electrode, a reference electrode and an electrolyte, respectively . To test the electrode characteristics, 0.5 mg of 3D-GN was mixed with acetylene black (10 wt%) and polyvinylidene fluoride (PVDF, 10 wt%) as a binder, and the mixture was applied to an FTO electrode (2.56 cm ² ) And dried at 150 캜 for 20 minutes in the atmosphere. Cyclic voltammetry was performed at different scan rates ranging from 5 mV / s to 500 mV / s. Electrochemical impedance spectroscopy (EIS) was performed using a potentiostat (Versa STAT 3, manufactured by AMETEK) in the range of 100 KHz to 0.1 Hz. A control sample for EIS measurements was made with 95% ethylene carbon and 5% PVDF.

Electrochemical measurement 2: < DSSC >

Short Circuit Current (J _sc ), Charge Rate (FF), and Open Circuit Voltage (V _oc ) by performing JV characterization under a solar condition with a solar simulator (SOL3A, manufactured by Oriel) , And the overall efficiency (?). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were performed using an electrochemical interface (manufactured by Solartron, SI 1287) and a constant voltage (VMP3 manufactured by Biologic). Cyclic voltametry was carried out using an electrolyte consisting of 0.5 mM I ₂ , 5 mM LiI, and 100 mM LiClO ₄ in acetonitrile and at a scan rate of 50 mV / s.

FIG. 2 is a photograph for confirming the morphological characteristics of a 3D graphene nano-network (3D-GN) according to an embodiment of the present invention. Figure 2 shows the morphological characteristics of 3D-GN obtained by removing a template composed of iron and 220 nm silica particles after CVD growth.

2 (a) is a scanning electron microscope (SEM) photograph of a PVA-FeCl ₃ / CS three-dimensional structure having a thickness of 3 μm, and FIG. 2 (b) It is a photograph.

The proper ratio of PVA to FeCl ₃ was determined by careful control of the gas pressure and flow rate during the CVD process. After removal of the CS template, the thickness of 3D-GN was reduced to about 80% of its original thickness, due to the loss of the carbon source and the collapse of the 3D-GN near the substrate due to the surface tension of the aqueous solvent during the drying process.

However, once the nanoporous structure is formed, it is sufficiently hardened and stabilized to be used in further applications, as would be expected from the high strength of already known graphene (1,100 GPa).

Figures 2c and 2d are transmission electron microscope (TEM) photographs of 3D-GN near the edge clearly showing the nano-cavity of 3D-GN and enlargement of one 3D-GN unit cell of diameter 220 nm Image.

Through Figure 2c, several layers of graphene can be identified, which is consistent with the Raman spectrum at 350 phr in Figure 9a.

On the other hand, pores having a diameter of 40 nm or less were observed on the surface of a single graphene sphere. This is thought to be due to the removal of the iron nanodomain formed by the agglomeration of iron during the annealing process.

Figure 2e is a diffraction image of a selected region of the edge of one graphene unit cell, representing the single crystalline nature of graphene.

In addition to the network formation in the film, a large amount of 3D-GN produced by CVD after drop-casting of the solution also showed similar quality in terms of graphene quality (Raman, resistance, etc.).

(A) and (b), (b) and (c) of powder 3D-GN produced by drop-casting and spin coating, respectively, showing mass synthesis of 3D- The X-ray spectrum (e) of C, the TEM photograph (f) of 3D-GN, and the three-layer 3D-GN film of the 3D-GN grown by a large amount of CVD, Close-up photograph (g) of GN is shown together. 3 (h) shows an image of a low-density 3D-GN near the edge. FIG. 3 (i) shows a close-up TEM photograph of one unit cell of several-layer grains having a particle diameter of 30 nm. A TEM photograph of the 3D-GN of the different regions is also shown in Fig. On the other hand, FIG. 4 shows TEM photographs of 3D-GN photographed in different regions.

Referring to FIG. 3 (d), the maximum ratio of I _2D / I _G and the minimum ratio of I _D / I _G were 0.23, which represents a significant amount of 3D graphene network. Referring to FIG. 3 (e), strong and sharp peaks at 284.18 eV derived from CC or C = C bonds were observed with relatively small defect peaks of 285.5 eV, 287.4 eV and 289.3 eV. A full width at half maximum (FWHM) of 0.87 was obtained, which is slightly higher than that of high quality single layer graphene. Referring to FIG. 3 (h), the nanopores of the 3D-GN can be reliably confirmed. 3 (i) is a photograph of the 3D-GN in g units in which mass synthesis of 3D-GN can be confirmed.

FIG. 5 is a graph showing the electrical conductivity of the 3D-GN powder. Referring to Figure 5, the average conductivity of the untreated 3D-GN powder was 5 S / cm, which is the reported 10 S / cm value for the graphene foam made from the micron-scale nickel nanoframe as ever known (FIG. 6 shows a graph showing the electrical conductivity of the 3D-GN film, and the conductivity of 30 nm 3D-GN in film form was 49 S / cm as shown in FIG. 6).

FIG. 7 shows the BET analysis results of 3D-GN having a pore size of 30 nm. The inset shows the pore distribution curve, and the specific values are shown in the table.

Referring to Figure 7, the surface area of the 3D-GN obtained through the BET measurement was surprisingly high, up to 1,025 m ² / g, with a pore size of 13 nm.

On the other hand, it was confirmed by X-ray diffraction (XRD) measurement that the iron (III) was reduced to iron (0). Fig. 7 (a) shows PVA-FeCl ₃ before and after annealing under H ₂ gas XRD data of the film is shown.

The data obtained from the pristine PVA / FeCl ₃ film represents a large number of large and uncertain peaks in red, whereas the annealed samples (in the case of iron-containing 3D-GN) Two sharp peaks corresponding to the (200) and (110) crystal planes of iron (Fe) (0) and another strong and sharp peak corresponding to the (002) crystal planes of graphene developed.

It can be seen from these peaks that the iron ions are completely reduced to almost one type of ferrous metal together with the preferential growth in the direction of the (110) crystal plane, and the peak appearing at 2? = 26 is the single crystalline graphene, Can be generated successfully. In addition, conversion of PVA / FeCl ₃ to ferrous metals and subsequent graphene growth can be confirmed by analysis of X-ray photoelectron spectroscopy (XPS) of iron, chlorine and carbon of the sample.

There is shown the XPS spectrum of Fe2p, Cl2p and C1 of the PVA / FeCl ₃ untreated (both red) and switch the 3D-GN / Fe (all black) after the CVD growth process b to d in Fig.

The major difference between the iron ion species and the metal iron can be seen in the Fe2p region at about 700 to 730 eV as shown in Figure 8b.

Fe2p the peak of the PVA / FeCl _3, each raw sample FeCl ₃ and Fe ₂ O were root (deconvolute) see Deacon into two major peaks of 711.5 eV and 724.54 eV to correspond to the binding energy of the _third of the Fe ^3+, which FeCl ₃ and oxidized Fe ₂ O ₃ coexist. On the other hand, a peak of about 704 eV, which corresponds to the binding energy of the metal ions appearing in the annealed sample, clearly shows the reduction of iron ions, and the peak between binding energies of 195 eV and 204 eV of the XPS spectrum indicates the presence of chlorine in the sample . In the untreated sample, respectively 2p3 / 2 and 2p1 / 2 chlorine ion (Cl ^-) corresponds to 198.8 eV, and two large red peaks corresponding to the binding energy of 199.95 eV, and chlorine ion peak of the 3D-GN / Fe sample to the Suggesting that chlorine has completely evaporated under high temperature growth conditions of 3D-GN. That is, the strong and sharp peaks at 284.18 eV derived from the CC or C = C bonds of 3D-GN / Fe, compared to the broad and significantly lower C1s peaks of the untreated samples in Figure 8d, Lt; / RTI &gt; For 3D-GN, a full width at half maximum (FWHM) of 0.82 was obtained, which is comparable to the FWHM value of high quality single-layer graphene.

FIG. 9 shows Raman spectra of 3D-GN produced by diffusion and precipitation of carbon on the surface of a three-dimensional iron network having various composition ratios of PVA to iron precursor.

According to heretofore reports describing the growth of graphene in iron, it has been known that the relatively high solubility of carbon in iron can lead to the formation of multilayer graphene with a few defect regions.

The present inventors have found that the initial amounts of iron and carbon have a great influence on the quality of the graphene and the structure formation of 3D-GN, which can be confirmed in the thermogravimetric analysis (TGA) data of FIG. 10 This is because iron and carbon are almost exhausted during the growth process.

Optimized growth conditions of graphene on PVA-FeCl ₃ / 3D-CS were found to be the best for 1000 experiments in all experiments during CVD until the best Raman peaks were obtained Lt; RTI ID = 0.0 &gt; C &lt; / RTI &gt; (see FIG. 11).

Referring to the bottom graph of Figure 9a, a typical Raman spectrum of 3D-GN at various ratios of PVA to Fe, characterized by more than 20 random locations, shows that the untreated FeCl ₃ / PVA has broad and strong D and G peaks .

The creation of graphenes in 3D-GN can be demonstrated by the reduction of the D-band intensity and the sharpening of the G and 2D bands in the high frequency region. The intensity of the G band steadily increased with an increase in the amount of FeCl ₃ accompanying the formation of sp ² bonds (from top to bottom). A significant increase in the intensity of the 2D band of 3D-GN at 350 phr represents a high quality single layer graphene. Since the D band observed from 3D-GN is believed to be due to near-edge or residual carbon, the D peak at about 1350 cm ^-1 for 350 phr is negligible.

As shown in Fig. 11, the maximum ratio of I _2D / I _G optimized at 350 phr and the minimum ratio of I _D / I _G are 1.74 and 0.15, respectively.

Therefore, the Raman spectrum shows that when the ratio of iron to PVA is about 1: 3.5, the amorphous portion of carbonized C is almost exhausted and transformed into a nearly single-layer three-dimensional graphene network. Surprisingly, the average conductivity of 3D-GN from more than 20 film samples was 52 S / cm, which is much greater than the values reported so far. In addition, the average conductivity of 3D-GN before iron removal was ~200 S / cm and potentially implies the possibility of direct use of 3D-GN / iron as a porous 3D electrode.

More importantly, an important advantage of the method of the present invention is that it enables mass production.

Essentially, this type of substrate-free CVD has no manufacturing scale limitations because the iron precursor can be uniformly dispersed with the carbon source to form a graphene frame. For example, 2 g of 3D-GN per CVD can be obtained, which is compared to 2,050 m ² / g of a planar 2D graphene based on the surface of the 3D-GN. Due to this mass production, the BET (Brunauer-Emmett-Teller) method is mainly used.

As shown in Fig. 11, the surface area of 3D-GN obtained by a mold of uniform silica particles of 220 nm (see Fig. 2) was 448 m ² / g, and the pore range of 3D-GN was about 210 to 230 nm And a smaller mesopore of 14 nm in diameter was present. The surface area of 448 m ² / g is larger than that of the CS mold of the same size (13 m ² / g), which is not only a few layers of graphene but also a cavity . It is possible to further improve the physical properties of 3D-GN, such as producing smaller pores using a smaller size of uniform silica mold, and not only growing conditions but also increasing the conductivity by controlling the composition ratio more systematically . In fact, the present inventors have been able to obtain a large amount of 3D-GN having a specific surface area and an average conductivity of 1,025 m ² / g and 5.4 S / cm using a silica particle mold having a particle size of 20 to 30 nm.

As shown in FIG. 11, even though the particle size and uniformity in the overall shape are somewhat lower than those of the larger size particles, uniform large size particles and Raman peaks and other characteristics are similar, 3D-GN was observed.

Another very useful advantage of the present invention over the other methods reported previously is that the growth of graphene is not limited by the choice of substrate due to the use of a metal precursor solution that is inherently scalable. It also allows for dimensional tunability and does not require a transfer process that can invoke additional defects.

Figure 9b shows Raman spectra of 3D-GN grown on an arbitrary substrate such as bare silicon, sapphire, GaN or quartz. The same conditions as in the SiO ₂ / Si substrate were used.

The most preferred Raman spectra with a better 2D band and a lower D band were obtained from 3D-GN grown on a sapphire substrate, which is thought to be very similar to a sapphire (111) plane with a graphene lattice, lt; RTI ID = 0.0 &gt; (epitaxy). &lt; / RTI &gt; The direct growth of 3D-GN in electrical device compatible substrates enables the production of ready-to-use graphene with minimal defects in the semiconductor industry.

To examine the potential application of 3D-GN, the inventors used 3D-GN performance as an electric double layer capacitor (EDLC) electrode using cyclic voltammetry (CV) and galvanostatic charge / discharge measurements Respectively. A large volume of 3D-GN having a specific surface area of 1,025 m ² / g and a conductivity of 5.4 S / cm was used. A 3D-GN was p-doped (doping) was immersed in HNO ₃ to have an improved conductivity than 6.9 S / cm or more.

FIG. 12A is a graph showing CV results obtained in various scan speed ranges of 0 V to 1.0 V based on Ag / AgCl electrodes of three-electrode cells manufactured using 3D-GN as an active material. FIG.

Generally, in the case of a supercapacitor using a carbon-based electrode, the shape of the CV curve and the specific capacity decrease remarkably as the scan speed increases, and the rectangular shape is distorted. At all scan rates, except for the highest scan rate of 100 mV / s, the CV curves of the 3D-GN supercapacitors were nearly rectangular, indicating that 3D-GN is ideal for high capacitance behavior and low contact resistance. Carbon electrode material. A slight departure from ideal double-layer capacitors at a scan rate of 100 mV / s appears to be related to increased resistance.

An excellent cost of 245 F / g in the H ₂ SO ₄ solution obtained at a scan rate of 5 mV / s was calculated from the following equation (1), which is obtained by further optimization of some parameters in cell processing Is very encouraging in that it is possible).

The large specific capacity of 3D-GN compared to the previously reported specific capacity (101 to 205 F / g, see Figure 8, f) of the graphene electrode material is such that a large contact area inside mesopores of appropriate size, It is due to the three-dimensionally interconnected conduction paths of graphene.

More specifically, compared to some known supercapacitors with a high specific surface area of more than 2,000 m ² / S, which have a relatively small capacitance value due to the presence of significant microvoids with a grain size of 2 nm or less, 3D-GN has an adequately large specific surface area of a controlled-size pore size of about 10 nm and can be used effectively and completely as an electrochemical reaction site.

The specific capacity per unit surface area is 23.9 μF / cm ² , which is very high for the bilayer capacitor. As a result of using the constant current charge / discharge method to evaluate the capacitive performance of 3D-GN, the highly symmetrical charging / discharging characteristics of a triangular shape typically represented by ideal capacitors were observed at a high current load of 100 A / g. Importantly, as shown in Fig. 12 (b), the capacitance loss of graphene is 13% or less at a current change of 5 to 100 A / g.

To obtain a comprehensive view of the capacitance response, an electrochemical impedance test was performed.

The Nyquist plot of 3D-GN shown in Fig. 12D shows a straight line in a small semicircle and an intermediate frequency region in a high frequency region. The small diameter of the semicircle in the high frequency region represents a low charge transfer resistance at the interface between the electrode and the electrolyte. The nearly vertical secondary part semicircle in the intermediate frequency domain exhibits a low charge transfer resistance in the adsorption process, which is highly influenced by the electrode surface morphology. The low resistance in both the high frequency and intermediate frequency domains may be due to the improved conductivity of the graphene network interconnected three-dimensionally through the desired diameter nano-passages.

Life-cycle stability is another important characteristic of electroactive materials in practical use as electrochemical capacitors. The 3D-GN based supercapacitor maintains a capacitance retention of more than 96.5% even after 6,000 cycles, suggesting excellent lifetime-cycle stability in practical use in electrochemical capacitors of 3D-GN based electrode materials .

In conclusion, the inventors have developed an easy and direct method for the fabrication of 3D networks of graphene, which is a nearly monolayer capable of growing on inert substrates via CVD techniques from PVA / iron precursors at high capacities.

The inorganic re-CVD process of the present invention involves dimensional tenability of high quality graphene by the possibility of forming a nanowire network.

Further, the present invention does not limit the selection of the substrate. 3D-GN can be grown on any inert substrate such as Al ₂ O ₃ , quartz, or SiO ₂ / Si wafers, and also on any substrate, such as a flexible device, cell culture plates, It can be further transported.

The ratio of I _2D / I _G (= 1.74) to the representative 3D-GN demonstrates the formation of several layers of graphene. The 3D-GN powder showed a conductivity of 5.4 S / cm, a high surface area of 1,025 m ² / g, and a high porosity of about 3.4 cm ³ / g. In the case of the 3D-GN film, the conductivity was also improved to ~ 52 S / cm.

Electrochemical measurements demonstrate that the electrode is a 3D-GN based electrode exhibiting excellent specific supercapacitance, demonstrating both charge through the three-dimensional conduction path and easy contact and transport on both sides of the electrolyte. The superior performance of 3D-GN, produced by an easy and inexpensive method, is not only for energy-related materials, but also for its potential for use in electrical and thermal systems, as well as for achieving nano-textured 3D graphene Provide a direct route.

We also evaluated the photovoltaic performance of DSSC cells fabricated in 3D-GN to develop the potential applicability of 3D-GN as a single component counter electrode (CE) in DSSC devices.

13 shows the photovoltaic performance of the DSSC using 3D-GN CE and Pt CE in the AM 1.5 intensity illumination. The photocurrent performance of the DSSC using the 3D-GN CE, the photocurrent-voltage (IV) curve (b) (C), and an incident photon-to-electron conversion efficiency (IPCE) spectrum (d) of the incident photon.

13A shows a DSSC cell (top), a photograph of the device (bottom left), and a SEM photograph (bottom right) of the 3D-GN CE. Referring to FIG. 2A, it is confirmed that the 3D graphenes are stacked and stacked in the CE through the SEM image, and that the 3D graphene is tightly coupled.

Figure 13b shows the photocurrent-voltage curves of DSSC with Pt CE in AM 1.5 intensity illumination and DSSC with untreated 3D-GN CE. Referring to FIG. 13B, the power conversion efficiency (η) showed 7.9% of Pt, while the untreated 3D-GN showed a maximum value of 7.91%. A slightly larger open circuit voltage (V _oc ) of ~ 0.8 for Pt (0.79) was observed in the 3D-GN CE and the improved band gap difference between the Fermi level of the TiO ₂ electrode and the redox potential of I ^- / I ₃ ^- And thus represents a recombination rate of the excited electrons that is slower, as is consistent with previously reported for carbon-based CE materials. In addition, a rather large short circuit current density (J _sc ) of ~ 15.6 mA / cm ² was observed in the 3D-GN system samples as expected from the large surface area (1,025 cm ² / g) of the 3D-GN CE. However, 3D-GN CE cells (see 63.6% vs. 66.5%, Table 1) shows a relatively low charging rate (fill factor, FF) to Pt than CE, if the charging rate to the resistance (R _s) and other internal resistance , It exhibits a higher resistance between the rough surfaces of the 3D-GN and the FTO, or between the 3D-GN electrode and the electrolyte.

As shown in Figure 13c, electrochemical impedance spectroscopy (EIS) for 3D-GN CE and Pt CE was performed to investigate the internal resistance and the charge transfer resistance at the interface between the electrode and the electrolyte . The first half-circle (high frequency: 100-1 kHz) in the impedance curve related to the charge transfer resistance (R _ct ) of the electrode surface is widely used to evaluate the catalytic activity of CE. The diffusion of the electrolyte species is related to the second semicircle (low frequency: less than 1 kHz), which is accounted for by the Nernst diffusion component (N). The sheet resistance determined from the start of the first half-circle (~ 100 kHz) is similar for Pt and 3D-GN (21.96 vs. 22.02) and represents the electrically tight bonding of 3D-GN on the FTO substrate. As can be expected from fairly low fill rate values, the overall impedance curve of the 3D-GN CE is slightly larger than the corresponding Pt CE. However, a very reduced charge transfer resistance (R _ct , the smallest first curve) was observed at the interface between the iodine electrolyte and the 3D-GN CE compared to Pt. This suggests that the surface of the untreated 3D-GN is effectively activated by existing oxygen atoms to improve the catalytic properties in the defect region. In addition, the synergistic effect of good conductivity due to the double-continuous 3D nature of CVD growth graphene and the large surface area caused by the 3D-GN nanoporous nature appears to promote faster electron transfer. It is well known that electrolytes exhibit lower diffusion rates due to the bypassed passage of electrolyte through the nanopore, thus the second circle of 3D-GN exhibits a significantly larger diameter.

As shown in FIG. 13 d, the number of photo-generated electrons per incident electron as a means of incident photon-to-electron conversion efficiency (IPCE) . To address the UV-visible spectrum at 300 to 800 nm, the reference Pt CE and 3D-GN CE with similar shape and maximum absorption values exhibited a maximum IPCE value of 58.9% and 60.25% at 540 nm, respectively, -GN DSSC will provide a slightly larger IPCE.

R _s (Ω) R _ct (Ω) V _oc (V) J _sc (mAcm ^-2 ) FF (%) 侶 (%) Pt 21.91 8.33 0.789 15.1 66.5 7.90 3D-GNs 22.02 5.13 0.799 15.6 63.6 7.91

Table 1 summarizes the photovoltaic properties of Pt-based DSSCs with efficiencies similar to those of untreated 3D-GN based DSSCs, along with EIS parameters.

From the obtained results, it can be concluded that the lower filling rate of 3D-GN can be sufficiently compensated by the improved V _oc and J _sc , which is also supported by the very low R _ct and the larger IPCE.

It is already known that the properties of graphene produced by incorporating other functional groups onto the graphene matrix can be further adjusted. For example, the improved electrical conductivity of graphene can be achieved by depositing dopant atoms on the graphene lattice, and the optimal catalytic effect of graphite in the DSSC can be achieved by adding small amounts of oxygen containing functionalities to the graphene surface.

In addition, the CVD growth untreated 3D-GN can be further optimized as CE in the DSSC through simple doping of heteroatoms. Through the p-doping process of 3D-GN, the conductivity and catalytic activity were significantly increased as the nitrogen and oxygen contents slightly increased. It is possible to easily achieve the optimum conditions through a slight modification of the graphene lattice through the light doping process and at the same time to ensure the sufficient conductivity of the graphene synthesized through the CVD process and also the improvement of the conductivity and the catalytic activity, The method in the present invention differs from other methods in that it aims to improve the conductivity of chemically produced graphene.

FIG. 14 is a graph showing an improvement in photovoltaic cell performance by immersing 3D-GN in various concentrations of HNO ₃ solution to improve the conductivity and catalytic activity of p-doped 3D-GN. On the other hand, the chemical composition of p-doped graphene obtained by elemental analysis (EA) is shown in Table 2 below.

The fraction of nitrogen atoms in 3D-GN immersed in HNO ₃ solution of 50%, 75%, and 100% for 30 minutes was measured to be 0.3, 0.4 and 0.5%, corresponding examples were 3D-GN-3, 3D- GN-4, and 3D-GN-5, respectively. The linear relationship between the measured conductivity and the nitrogen atom content of p-doped graphene improved to 7 S / cm. An additional increase in immersion time did not affect the conductivity of the sample.

14A is a J-V curve of untreated 3D-GN and p-doped 3D-GN with various nitrogen and oxygen content values under a light source of AM 1.5. The detailed photovoltaic cell performance with conductivity and nitrogen and oxygen content values are shown in Table 2 below. The power conversion efficiency of p-doped 3D-GN increased with the increase of N and / or O contents, and it was 8.42% at the optimized condition of 0.5% nitrogen content and the conductivity was 7 S / cm.

There is b, the XPS spectrum of O1 in Figure 14 shows, a peak of 531.8 eV area increases with the increasing concentration of HNO ₃ solution, and, as in the EA data, the degree of incorporation of oxygen atoms to determine a more high. It can be seen that the highest O content value of the sample with the highest conversion efficiency at 0.5% N content further activates the surface of 3D-GN by the maximum amount of oxygen for improved catalytic properties. Importantly, although the conductivity may be adversely affected by a large amount of oxygen content, as shown in Table 2, it can be confirmed that the conductivity is not deteriorated by such an oxygen content.

14C, in order to compare the electrochemical catalytic activities of the four types of p-doped 3D-GN and Pt, the cyclic voltammetry was performed using 0.1 M LiClO ₄ , 10 Mm LiI, and 0.5 mM I ₂ solution Of the electrolyte. The relatively negative potential peak between the two positive current peaks corresponds to the oxidation reaction of 3I ^- → I ₃ ^- + 2e ^- , and the relatively negative potential peak between the two negative current peaks is I ₃ ^- + 2e ^- &gt; 3I &lt; ^{- &} gt ;. The oxidation / reduction current increased with increasing catalyst surface area. The separation between the peaks of the I ₃ / I ^- redox reaction (ΔE _p ) decreased with the increase in the feasibility of the catalytic reactions.

N (%) O (%) Ω ^-1 (S / cm) V _oc (V) J _sc (mAcm ^-2 ) FF (%) 侶 (%) 3D-GN 0 2.5 5.0 0.799 15.6 63.6 7.91 3D-GN-3 0.3 8.3 6.0 0.799 15.8 64.0 8.10 3D-GN-4 0.4 9.1 6.3 0.783 16.0 65.4 8.17 3D-GN-5 0.5 9.6 7.0 0.781 16.3 66.0 8.42

As shown in following Table 3, the relationship between the negative effect a beneficial effect on performance, and positive relationship between the amount of current and the absolute peak value of the dopant, and the amount of _p dopant, and ΔE was observed. In addition, all of the 3D-GNs exhibited greater electrochemical catalytic activity and catalyst surface area, thus exhibiting a higher current density and lower ΔE _p than the Pt electrode. 3D-GN-5 has the lowest E _p Values and the highest current peak values, reflecting excellent control of the wide surface area, strong catalytic effect and high conductivity of optimized 3D-GNs (certainly more of P-doped 3D-GNs than Pt A large electrochemical catalysis, and a tapel curve of a symmetric dummy cell that provides a monotonic relationship between the dopant content and the logarithmic current density is shown in FIG. 15).

ΔE _p (mV) I _re (mAcm ^-2 ) R _s (Ω) R _ct1
(Ω) Pt 386 -1.64 21.91 8.34 3D-GN 331 -1.75 22.03 5.13 3D-GN-3 314 -1.76 22.08 4.88 3D-GN-4 289 -1.82 22.03 2.49 3D-GN-5 269 -1.96 22.25 1.29

The doping effect of untreated 3D-GN in the performance of the DSSC can be further confirmed by EIS data. As can be found from the impedance curve of the 14 d, as the content of both N and O of the 3D-GN is increased, the unresolved (unresolved) second and semicircle diameter of the third did not change significantly R _ct Respectively. 3D-GN-5 with the highest N and O content has the smallest R _ct value with the optimal total impedance curve comparable to Pt, and has a strong catalytic activity, as well as a broad catalytic surface area. It represents a fast electronic transfer mechanism.

16 shows the IPCE spectrum of DSSC having CE of Pt, untreated 3D-GN, 3D-GN-3, 3D-GN-4 and 3D-GN-5, A graph showing the performance stability of DSSC with CE of doped 3D-GN is shown.

Referring to FIG. 16, as the degree of doping increases, a higher IPCE graph is shown. In the case of 3D-GN-5, the best IPCE performance is shown, which is in agreement with the best performance of a DSSC cell. Also, referring to FIG. 17, the doped samples exhibited a performance stability of 88% or more even after 25 days, which is comparable to Pt. Thus, for the doped sample, an impressive energy conversion efficiency of 8.42%, which is over 6.4% enhanced compared to the entire untreated 3D-GN, is obtained in p-doped 3D-GN CE. Importantly, an average of 6% greater efficiency for Pt was observed from more than 20 samples under the experimental conditions in the present invention. This is very promising, considering that the efficiency of 3D-GN based DSSCs can be further enhanced through precise tuning of some parameters for the fabrication of devices, such as improvement in adhesion under study and optimization of additional doping conditions .

In conclusion, the present inventors have developed a direct method for achieving mass production of DSSCs with large surface area and good conductivity through precursor-assisted CVD growth 3D-GN. 3D-GN having an average conductivity of 5 S / cm, a large surface area of 1,025 cm ² / g, and an excellent porosity of 3.4 cm ³ / g form a CS structure having an iron precursor and a PVA solid carbon source, The graphenes are sequentially grown under the conditions and are manufactured on a large scale. DSSC based on untreated, untreated, single component 3D-GN showed comparable efficiency to Pt. Most importantly, the efficiency of a DSSC cell fabricated with optimized p-doped 3D-GN CE was 6.6% better than that obtained from a Pt CE cell, suggesting the potential of 3D-GN as an excellent single component as an alternative to Pt do. All electrochemical measurements, such as CV curves, impedance data, and tapel curves, provide clear evidence of the high conductivity, large surface area, and high catalytic activity of p-doped 3D-GN, Which is the reason for their excellent power conversion efficiency.

The excellent performance of 3D-GN as the counter electrode in the DSSC fabricated by the easy and inexpensive method of the present invention is the result of the intuitive route of nano-woven 3D gravure which has excellent potential for use in energy- Can be used for the development of pins.

Claims (9)

(1) laminating colloidal silica on a substrate to form a three-dimensional colloidal silica structure having a thickness of 0.1 to 5 탆;
(2) filling the three-dimensional colloidal silica structure with a solution containing a solid carbon source for graphene growth and a metal precursor in a weight ratio of 1: 2 to 1: 4;
(3) heating the three-dimensional colloidal silica structure packed with the solution to 700 to 1200 占 폚 under hydrogen gas to form a nano-foam structure containing metal; And
(4) removing the metal in the graphene of the colloidal silica and the nano foam structure.
Method of manufacturing a three dimensional graphene nano-network.
delete The method according to claim 1,
Wherein the solid carbon source for graphene growth is selected from the group consisting of polymethylmethacrylate (PMMA), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), and mixtures thereof. Way.
The method according to claim 1,
The metal precursor may be selected from the group consisting of nickel nitrate hexahydrate {Ni (NO ₃ ) ₂ .6H ₂ O}, nickel acetate {Ni (CH ₃ COO) ₂ }, nickel sulfate hexahydrate (NiSO ₄ .6H ₂ O) (NiCl ₂揃 6H ₂ O), copper chloride hexahydrate (CuCl ₂揃 6H ₂ O), ferric chloride hexahydrate (FeCl ₃揃 6H ₂ O), or a mixture thereof. &Lt; / RTI &gt;
delete The method according to claim 1,
The step of removing the colloidal silica and the metal in the step (4) is carried out using an etching solution selected from the group consisting of hydrofluoric acid, hydrochloric acid, nitric acid, ammonium persulfate solution and mixtures thereof. - a method of manufacturing a network.
A three dimensional graphene nano-network fabricated by a manufacturing method according to any one of claims 1, 3, 4 or 6.
10. A super-capacitor comprising a three-dimensional graphene nano-network according to claim 7.
A dye-sensitized solar cell (DSSC) comprising a three-dimensional graphene nano-network according to claim 7.

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