KR101073981B1 - Nano Composite for Platinum Free Electro-catalyst and Method for Preparation Thereof - Google Patents

Abstract

Embodiments of the present invention relate to nanocomposites for Pt-free electro-catalysts used in fuel cells, and more specifically, gold nanoparticles and silica on the sidewalls of multi-walled carbon nanotubes (MWNT). The present invention relates to a nanocomposite to which particles are bound and a method of manufacturing the same.

Electrocatalyst, multi-walled carbon nanotube, gold nano, silica

Description

Nano Composite for Platinum Free Electro-catalyst and Method for Preparation Thereof}

Embodiments of the present invention relate to nanocomposites for Pt-free electro-catalysts used in fuel cells, and more specifically, gold nanoparticles and silica on the sidewalls of multi-walled carbon nanotubes (MWNT). It relates to a nanocomposite bonded to the particles and a method of manufacturing the same.

While research is being conducted to find effective catalysts for fuel cells, current techniques are at lower energy conversions, higher Pt content of the electrocatalyst, and cathode catalysts. It has defects such as instability of platinum. Platinum-based catalysts have high activity and performance for oxygen reduction, but due to high raw material costs and limited supply, ultimately there are problems in commercial mass production of fuel cells.

However, to manufacture commercially viable fuel cells, it is necessary to overcome the barriers of high catalyst costs caused by the exclusive use of platinum and platinum based electrocatalysts. Importantly, platinum (Pt) catalysts are used for both oxidation of fuel and reduction of oxygen at the electrodes of fuel cells. Apart from the high cost of catalysts and other fuel cell system components (polymer electrolyte membranes, bipolar plates, power systems), fuel cells are characterized by agglomeration, oxidation, catalyst transfer, reduction of electrode active surface area, and carbon support of cathode catalysts. There is a problem that durability is not sufficient due to corrosion.

In the case of DMFC, in addition to the above problems, the Pt of the negative electrode also suffers from performance degradation from the mixed potential due to the methanol diffusion through the membrane from the anode side of the cell.

However, the Pt electrode of PEMFC is even sensitive to very low levels of CO. Therefore, research has been conducted to find efficient, durable, and most importantly low cost Pt material replacement catalysts and support materials.

As one of the platinum replacement electrocatalysts, gold has been shown to exhibit good activity against oxygen reduction in bulk gold. Compared with platinum catalysts, gold catalysts can have better activity. Supported gold (Au) catalysts have already demonstrated higher catalytic activity in various types of reactions (eg, selective reduction of NO by hydrocarbons in the presence of high concentrations of oxygen).

The present invention has found that the activity of the supported Au catalyst is highly dependent on the size of the gold particles, and the catalyst properties are markedly influenced by the interaction between gold and the supported. However, when compared to studies focused on platinum group metals, the field of gold catalysts is still underdeveloped. Even the production of evenly dispersed gold catalysts has not been developed yet, making them difficult. In order to obtain a structure that can promote even dispersion of the gold catalyst, development of a new effective method is necessary.

Since the discovery of carbon nanotubes (CNTs), research on nanocomposites has been actively conducted due to their potential for catalysis, hydrogen storage, sensors, loading and transport of drugs. In order to expand the scope of application of carbon nanotubes, it is necessary to bond functional groups or other nanostructured materials to the surface of carbon nanotubes.

CNT / Metal Nano Particle (MNP) hybrid materials have properties such as high conductivity, large surface area, and catalytic properties, and thus have a wider range of applications. Over the past few years, many studies have been conducted to immobilize MNPs on the surface of organoleptic CNTs, including electrochemical precipitation, electroless precipitation and functionalization of chemical oxidation sidewalls. Covalent and non-covalent functionalization of sulfur-containing compounds, especially CNTs with thiols (-SH), has been of particular interest as the thiols have a high affinity for immobilizing metal nanoparticles (MNP). One of the problems associated with maintaining long term stability of CNT / MNP supported catalysts is the filtration of MNP under operating conditions and the continual decrease in catalyst activity. Therefore, a more advanced method of manipulating the surface of CNTs is required.

In particular, the attachment of gold nanoparticles (Au NPs) to the sidewalls of CNTs has been associated with the development of efficient fuel cells, sensors and photoelectrochemical cells. Several methods have been tried, such as traditional impregnation, sol-gel technique, and chemical vapor deposition. Chen et al. Developed a method for immobilizing Au nanoparticles (NPs) to non-covalent functionalized CNTs. Au nanoparticles are self-assembled into CNTs through a polyelectrolyte or deoxyribonucleic acid (DNA) as a crosslinking material, and Au nanoparticles are attached to the surface sites of the CNTs by a radiation method. . In another attempt, carbon nanotubes (CNTs) were functionalized with conducting polymers, polyaniline (PANI), and used as linkers to attach gold nanoparticles.

Recently, sol-gel chemistry has been used for CNT functionalization due to its simple and easy processability. Silica or its nanospheres have interesting properties such as large aspect ratio, wide band gap and high biocompatibility. Therefore, coating silica on the CNT surface can yield unique nanomaterials bonded in a unique form. Silica-CNT hybrids are prepared by template assembly of silica nanoparticles on the CNT surface. Silica-CNT hybrids were also prepared with silicic acid molecular sieve supported catalysts. Li et al. Synthesized CNT-silica core shell nanowires by chemical vapor deposition. A layer-by-layer self assembly method was used to prepare the CNT-silica core shell composite. A thin silica layer was coated on the CNT surface using 3-aminopropyltriethoxysilane as the crosslinking molecule. The silica layer was coated on poly (4-vinylpyridine) functionalized CNTs by sol-gel method.

It is advantageous to use CNT / silica as a support matrix for the dispersion of MNP. In the manufacturing process of the new CNT-silica-based nanocatalysts, MNP can be induced three-dimensionally in the silica shell to form coaxial nanocables. Guo et al. Reported the use of 1D CNT / SiO ₂ coaxial nanocables as a new support matrix to disperse gold / platinum nanoparticles (Au / Pt NP).

Several manufacturing methods have been developed, such as chemistry, photochemistry, ultrasonic chemistry, electrochemistry and radiolysis to prepare MNPs from metal salts. Among them, radiation synthesis has important advantages over other methods. γ-ray synthesis can be carried out environmentally friendly under reaction conditions of short reaction time at room temperature.

The present invention has an excellent electrocatalyst activity without including platinum, can replace the existing platinum electrode catalyst, to provide a nanocomposite for the electrode catalyst that can be easily mass-produced industrially and reduce the production cost The purpose is.

The present invention relates to a nanocomposite for Pt-free electro-catalyst used in fuel cells, and more specifically, gold nanoparticles and silica particles are bonded to sidewalls of multi-walled carbon nanotubes (MWNT). To a nanocomposite.

The multi-walled carbon nanotubes may be preferably functionalized by a surface containing a sulfur-containing functional group, and more preferably functionalized by a thiol group (-SH).

In addition, the present invention relates to a method for producing a nanocomposite for Pt-free electro-catalyst used in fuel cells, by functionalizing the surface of the multi-walled carbon nanotubes with a thiol group (-SH) A first step of obtaining a thiol functionalized multi-walled carbon nanotube (MWNT (SH)); A second step of mixing the thiol functionalized multi-walled carbon nanotubes (MWNT (SH)) with a silica precursor solution and then stirring; The third step of irradiating γ-rays after the addition of HAuCl ₄ and HCl; characterized in that it comprises a.

The first step, more specifically, multi-walled carbon nanotubes (MWNT) to nitric acid (HNO _{3 )} After refluxing, it was filtered using a polycarbonate membrane, and then the residue was washed with water and dried in vacuo to form MWNT-COOH; The MWNT-COOH was refluxed with thionyl chloride (SOCl ₂ ), filtered using a polycarbonate membrane, and then the residue was washed with tetrahydrofuran (TETRAHYDROFURAN, THF) and dried at room temperature in vacuo to MWNT-COCl Forming a; After refluxing the MWNT-COCl with 4-aminothio phenol (4-aminothio phenol), the residue was washed with water and dried in vacuo to obtain a thiol functionalized multi-walled carbon nanotube (MWNT (SH)). It is characterized in that consisting of, more preferably multi-walled carbon nanotubes (MWNT) in 3 to 5M nitric acid (HNO _{3 )} for 22 to 26 hours After refluxing, the mixture was filtered using a polycarbonate membrane pore having a pore size of 0.2 μm, and then the residue was washed with water and dried under vacuum at 55 to 65 ° C. for 10 to 14 hours to form MWNT-COOH. Making a step; The MWNT-COOH was refluxed in thionyl chloride (SOCl ₂ ) at 60 to 70 ° C. for 22 to 26 hours, filtered using a polycarbonate membrane having a pore size of 0.2 μm, and then the residue was tetrahydrofuran (TETRAHYDROFURAN). , THF) and dried in vacuo at room temperature to form MWNT-COCl; The MWNT-COCl was refluxed with 4-aminothio phenol (4-aminothio phenol) at 90 to 100 ° C. for 22 to 26 hours, and then the residue was washed with water and dried in vacuo to form a thiol-functional multiwalled carbon nanotube. Obtaining (MWNT (SH)).

The second step is to mix and stir the thiol functionalized multi-walled carbon nanotubes (MWNT (SH)) obtained in the first step to the silica precursor solution, the side wall of the thiol functionalized multi-walled carbon nanotubes (MWNT (SH)) As a step of bonding the silica particles to, the silica precursor is not particularly limited in its kind, but trimethoxysilylpropylaniline (TMSPA), tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl It may be preferred to be selected from the group consisting of orthosilicates and mixtures thereof, more preferably trimethoxysilylpropylaniline (TMSPA).

Another aspect of the present invention relates to a platinum (Pt) free electrode catalyst for fuel cells using the nanocomposite.

The nanocomposite according to the present invention, due to the presence of silica and catalyst particles on the surface of the nanotubes, interferes with van der Waals forces between the nanotubes, to evenly disperse the nanotubes and nanoparticles, Due to the even dispersion, the catalyst particles have a high surface area and therefore a high catalytic activity. Catalysts modified with electrodes have the effect of enhanced electrocatalyst activity towards the oxygen reduction reaction at large amounts of positive reduction potential. Therefore, the electrode catalyst using the nanocomposite according to the present invention can replace the existing platinum catalyst, it is easy to mass-produce industrially, and the production cost can be reduced.

As described above, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. The scope of the present invention is shown by the claims to be described later rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. Should be.

<Examples>

1. Compound ( chemicals ) Ready

Multi-walled carbon nanotubes (MWNT) having a diameter of 20 to 50 nm were prepared (Incheon, Korea). Trimethoxysilylpropylaniline (TMSPA), gold chloride (auric chloride, HAuCl ₄ ) and 4-aminothio phenol were purchased from Aldrich (Korea). 2-propanol, thionyl chloride (SOion ₂ ), nitric acid (HNO ₃ ), hydrochloric acid (HCl) and tetrahydrofuran (TETRAHYDROFURAN, THF) were prepared as analytical samples. It was.

2. Thiol Functionalization MWNT ( MWNT ( SH Manufacture of))

Thiol functionalized MWNTs were obtained through continuous chemical modifications to the MWNTs. Typically, 50 mg of MWNTs in 4 M of HNO ₃ After refluxing for 24 hours, it was filtered using a polycarbonate membrane (pore size: 0.2 μm). The residue (carboxylated MWNT (MWNT-COOH)) was then washed with water and dried in vacuo at 60 ° C. for 12 h. 50 mg of MWNT-COOH was refluxed in 100 ml of SOCl ₂ for 24 hours at 65 ° C. The residue (MWNT-COOH) was filtered off, washed with THF and dried at room temperature in vacuo. MWNT-COCl was refluxed with 4-aminothio phenol of THF at 95 ° C. for 24 hours to prepare MWNT (SH). The residue (MWNT (SH)) was washed with water and dried in vacuo.

3. γ-ray irradiation MWNT ( SH ) - Au NPs Of silica Nanocomposite ( NC Manufacturing

MWNT (SH) (1 mg / mL) was dispersed in an emulsion (2-propanol: water = 7: 3 (v / v)) for 30 minutes under sonication (BRANSON digital ultrasonicator, model: 2501). In a representative experiment, 15 mL of the dispersed MWNT (SH) was mixed with 6 mL of 200 mM TMSPA (silica precursor) solution and stirred for 30 minutes. After adding 1 mL of 0.3 mM HAuCl ₄ and 8 mL of 0.3M HCl to the mixed solution, the γ-ray (Co-60 source) of 30 kGy total dose (dose rate = 6.48 x 10 ⁵ Gy / h) was irradiated. Different amounts of MWNT (SH), different doses of radiation, different concentrations of HAuCl ₄ And experiments were performed on TMSPA. MWNT (SH) -Au NPs / silica-NC is the mass of MWNT (SH) in mg, HAuCl ₄ The concentration (μM), the concentration of trimethoxysilylpropylaniline (TMSPA, silica precursor) (mM) and the dose level (kGy) of γ-rays used. (See [Table 1] below)

For example, MWNT (SH) -Au NPs / silica-NC prepared with 15 mg of MWNT (SH), 10 μM of HAuCl ₄ , 40 mM of TMSPA and 30 kGy dose level of γ-rays yielded MWNT (SH) -Au NPs / silica-NC (15: 10: 40: 30).

4. Laboratory apparatus used

MWNT (SH) -Au NPs / silica-NC were analyzed with a UV-vis spectrometer (Shimadzu UV-2101 spectrophotometer) and an FT-IR spectrometer (Perkin-Elmer Lamda 9N-1062 spectrometer). The morphology of the samples was tested by EDAX measurement using scanning electron microscopy (FESEM; Hitachi, S-4200). The microstructures of silica, carbon nanotubes (CNT) and gold nanoparticles (Au NPs) are field emission electrons using high voltage transmission electron microscopy (HVTEM; JEM-ARM 1300s). gun) was operated at 1250 kV. 50 cm ^-1 to The Raman spectra of the complex was investigated using SPEX, Ramalog 9I / Coherenet, and Innova 905 Laser Raman Spectrophotometer in the range of 4000 cm ⁻¹ . Electrochemical experiments were performed using IVIUMSTAT and COMPACTSTAT (The Netherland) in a traditional three-electrode electrochemical cell using twisted platinum wire as an auxiliary electrode and Ag / AgCl as a reference electrode. It was. The platinum (Pt) disc electrode was used as a modified MWNT (SH) -Au NPs / silica-NC working electrode.

5. Measurement of electrical activity and electrode catalyst

The electrical activity of MWNT (SH) -Au NPs / silica-NC was measured using cyclic voltammetry in the presence of 10 mM Fe (CN) ₆ ^{3- / 4-} (0.1 M KCl). Electrode-catalyzed oxygen (O ₂₎ reduction measurements were performed using MWNTs modified with platinum wire (secondary electrode), Ag / AgCl (reference electrode) and platinum disc (Pt disc) in a 0.5 MH ₂ SO ₄ solution saturated with oxygen (O ₂ ). It was performed using a three-electrode cell setup consisting of SH) -Au NPs / silica-NC (working electrode). For electrochemical measurements, working electrodes were assembled as follows: A suspension of MWNT (SH) -Au NPs / silica-NC (1 mL of DMF) was prepared and then the MWNT (SH) -Au NPs / silica- The NC suspension was dropped onto platinum (Pt) disk electrode (area: 0.07 cm ² ) and dried at room temperature. 5 μL of Nafion (0.25%) solution was placed on the MWNT (SH) -Au NPs / silica composite film surface and dried at room temperature.

Hereinafter, look at the test results for the present invention.

6. Morphology of MWNT (SH) -Au NPs / silica Nanocomposites

1 is a scanning electron microscope (FESEM) photographs of MWNT (SH) -Au NPs / silica nanocomposites prepared under different conditions, and FIG. 2 is an electron microscope (TEM) photograph. In the MWNT (SH) -Au NPs / silica composite according to the invention, the dispersion of Au nanoparticles, MWNT (SH) and silica (silica) could be understood. According to the FESEM photograph shown in Figures a to e of the nanocomposites, it can be seen that the spherical silica particles having different sizes, respectively. MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30), MWNT (SH) -Au NPs / silica nanocomposites (10: 10: 40: 30) and MWNT (SH) -Au NPs / In the silica nanocomposites (05: 10: 40: 30), the silica particles were 1 μm, 0.85 μm and 500 nm, respectively. 1 through a and d, MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) and MWNT (SH) -Au NPs / prepared by varying the concentration of TMSPA (silica precursor) Scanning electron micrographs of silica nanocomposites (15: 10: 80: 30) can be compared. As the concentration of the silica precursor increased, the size of the silica particles increased from 1 μm to 1.2 μm. This means that the concentration of the silica precursor also affects the size of the silica particles. Again, dispersion of nanotubes can be better seen in MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30) containing larger silica particles. MWNT (SH) -Au NPs / silica nanocomposite prepared at γ-ray 10 kGy (FIG. 1 e) was prepared by irradiation of γ-ray of 30 kGy (MWNT (SH) -Au NPs / silica nanocomposite (FIG. 1). It was found that silica particles (about 300 nm) were three times smaller than a).

In addition, the HAuCl MWNT (SH) -Au NPs / silica nanocomposites prepared from the solution containing the MWNT-SH and a silica precursor with no _{4 (15: 0: 40:} 30) (f in Fig. 1) is produced in the presence HAuCl ₄ 1, MWNT (SH) -AuNPs / silica nanocomposites (15: 10: 40: 30) of FIG. 1 contained silica particles (200 nm) smaller than the size of the silica particles (about 1 μm).

Scanning electron micrographs did not clearly confirm the presence of Au nanoparticles. However, the EDAX results of the composite of FIG. 2 (see Table 1) corresponding to the scanning electron micrographs of FIGS. 1 a to e clearly show the presence of Au with Si (see Table 2 below). .

Ultra high pressure electron microscope images were used to investigate the size and shape of Au nanoparticles. The size and shape of the Au nanoparticles depended on the experimental conditions. The size and shape of Au nanoparticles were compared against nanocomposites prepared with different doses of γ-ray irradiation. Ultrahigh-pressure electron microscopy images of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) at different magnifications showed the size and shape of Au nanoparticles (see a in FIG. 3).

According to a of FIG. 3, Au particles appeared in various masses on the surface of MWNT (SH). The individual masses have a spherical shape (a1 in FIG. 3), a pentagonal shape (a2 in FIG. 3) and an inclined square shape (a3 in FIG. 3).

The size of the individual particles in the mass is about 10-20 nm, regardless of shape. However, the FETEM images (Fig. 3b) of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10) prepared by 10 kGy dose of γ-ray irradiation showed one large chunk of Au nanoparticles. Show crystals (50 nm).

3c shows an ultrahigh pressure electron microscope image of spherical silica particles (about 200 nm) in MWNT (SH) -Au NPs / silica nanocomposites (15: 0: 40: 30) prepared without HAuCl ₄ . It can be seen that a large number of empty pores are visible in the silica particles. However, these pores are filled with gold nanoparticles in MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) (see d in FIG. 3). Thus, gold nanoparticles are also filled in the pores of silica particles.

7. UV-visible spectroscopy

Ultraviolet spectroscopy confirmed the presence of gold nanoparticles in the MWNT (SH) -Au NPs / silica nanocomposites. 4 shows peaks at 250 nm and 305 nm in ultraviolet spectra for MWNT (SH) -Au NPs / silica nanocomposites prepared under different experimental conditions, respectively. Two peaks were designated as π-π * electronic transitions of MWNT and PTMSPA (silica precursor), respectively. The sharp peak (530 nm) shows the surface plasmon resonance absorption of the gold nanoparticles. The location of the surface plasmon resonance bands of gold nanoparticles is known to be sensitive to the surrounding environment. Typically, in FIGS. 4A to 4, MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) and MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30) ), UV spectra for MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10) and MWNT (SH) -Au NPs / silica nanocomposites (15: 0: 40: 30) were compared. . Plasmon resonance bands of gold nanoparticles are MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30), MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30) And in the spectra of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10), respectively, near 560 nm, 605 nm and 550 nm (see FIG. 4).

Importantly, in the MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 80: 10), the plasmon resonance band shifted to a higher wavelength (about 605 nm) (curve in FIG. 4). b). This may be due to the influence of the large size of the silica particles. Plasmon bands of gold nanoparticles were not found in MWNT (SH) -Au NPs / silica nanocomposites (15: 0: 40:10) prepared without HAuCl ₄ (see curve d in FIG. 4).

8. Fourier transform infrared spectroscopy (FTIR) test

5 shows FTIR spectra of MWNT (SH) -Au NPs / silica nanocomposites. The spectra indicate the presence of a silica-specific peak in the MWNT (SH) -Au NPs / silica nanocomposites. The presence of silica-specific peaks confirms the conversion of siloxane groups in TMSPA to silica by γ-rays. Another important feature can be seen in the spectrum of the complexes of the invention. The spectrum of the MWNT (SH) -Au NPs / silica nanocomposite shows a band due to the -CO stretching band of the carbonyl group around 1620 cm ⁻¹ . It can be predicted that a carboxyl group is formed on the surface of MWNT by γ-ray irradiation. It is interesting to note that there is a displacement at the position of the -CO stretching band of the composite of the present invention. MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30), MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10) and MWNT (SH) -Au NPs / The FTIR spectra of silica nanocomposites (15: 10: 80: 30) were compared. The band intensity of the C = O stretching of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) produced by higher γ-ray dose (30 kGy) was 10 kGy. It was higher than the C = O band intensity of the prepared MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10). Also, near 1020 cm ⁻¹ for MWNT (SH) -AuNPs / silica nanocomposites (15: 10: 40: 10) (see curve c) The intensity of the Si-O-Si stretching band peak was reduced when compared with the MWNT (SH) -AuNPs / silica nanocomposites (15: 10: 40: 30) (curve a). This suggests that there may be a hydrogen bonding interaction between the carboxy group of MWNT and the —OH group of silica.

9. Raman analysis Raman studies )

6 shows the Raman spectrum of MWNT (SH) -Au NPs / silica nanocomposites. In general, the band observed near 1300 cm ⁻¹ represents amorphous carbon in the hexagonal structure of the nanotube wall and disordered sp ³ hybrid carbon (see D-band). The band around 1600 cm ⁻¹ is designated the hexagonal mode (G-band) of graphite. Analysis via Raman spectra explains that the location and intensity of the D bands are affected by the conditions of preparation of the complex. Since the D band corresponds to the disordered structure of the carbon nanotubes, variations in the position and intensity of the band arise from the modification of the surface and electrical state of the carbon nanotubes. Curves a to d of FIG. 6 are MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30), MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30), Comparison of the position and intensity of the D bands of MWNT (SH) -Au NPs / silica nanocomposites (15: 30: 40: 30) and MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10) It is shown. MWNT (SH) for -Au NPs / silica nanocomposites, the D band is observed in each of 1305 cm ^-1, 1340cm ^-1 and 1335cm ^-1. Therefore, the presence of silica particles and deposition of gold (Au) nanoparticles on the surface of carbon nanotubes can be expected to exert a molecular force on the MWNT. At low γ-dose, the carboxyl group minimizes the change of MWNTs. This result is consistent with that of the FTIR spectrum.

10. MWNT ( SH ) - Au NPs Of silica  Electrical Activity of Nanocomposites

The electrical activity of the MWNT (SH) -Au NPs / silica nanocomposites transformed into Pt disc electrodes was measured using Fe (CN) ₆ ^{3- / 4-} as a redox marker. For comparison, the original MWNT (SH) and MWNT (SH) -Au nanoparticle modified electrodes were also investigated (see FIG. 7). The MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 30) modified electrode is a Fe (CN) ₆ ^3- with positive to negative peak potential separation of 130 mV at 50 mV.s ^-1 scan rate. ^The redox peak (260 mV (anode) / 130 mV (cathode)) corresponding to ^{/ 4-} is shown. However, the redox peaks of Fe (CN) ₆ ^{3- / 4-} were not clear at the MWNT (SH) and MWNT (SH) -Au nanoparticle modified electrodes. This means that the Pt / MWNT (SH) -Au NPs / silica nanocomposite electrode has an excellent electrical activity compared to other electrodes. Again, CVs of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) at different scan rates (10-100 mV.s ⁻¹ ) were recorded (see FIG. 8). The linear dependence of the peak current at the scan rate (R ² = 0.9938) (see the internal graph in FIG. 8) is due to the electron transfer process at the MWNT (SH) -Au NPs / silica nanocomposite strain electrode ( electron transfer process) is a surface limiting element.

11. MWNT ( SH ) - Au NPs Of silica  Electrocatalyst of Nanocomposite electro - catalyst ) activation

Electrode of Pt / MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 30) in the direction of oxygen reduction reaction (ORR) using cyclic voltammetry Catalyst activity was investigated (see FIG. 9). O ₂ Cyclic voltammograms (CVs) of Pt / MWNT (SH) -Au NPs / silica nanocomposite modified electrodes were recorded for saturated 0.5MH ₂ SO ₄ solution. For comparison, the electrocatalyst efficiencies of the Pt / MWNT and Pt / MWNT-Au nanoparticles were also examined and the peaks corresponding to the ORR of the MWNT (SH) and MWNT (SH) -Au nanoparticle modified electrodes were 330 mV and It was confirmed at 390 mV. However, ORR occurred at about 460 mV potential in the Pt / MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 30) modified electrode. Therefore, MWNT (SH) -Au NPs / silica nanocomposite modified electrodes have positive potential shifts of 130 mV and 70 mV for ORR, respectively, when compared to Pt / MWNT and Pt / MWNT-Au nanoparticle modified electrodes. excellent electrode catalyst activity with potential shift). The peak potential for ORR found in the Pt / MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 30) modified electrodes is based on gold nanoparticle dispersed polyamino thiophenol-cyclodextrin inclusion complex modified electrodes, Much better electrocatalyst than polyaniline / Co strain electrodes, polypyrrole / Co strain electrodes, poly (3-methyl thiophene) / Co strain electrodes, gold nanoparticles / glass carbon electrodes and Au NPs / highly oriented pyrolytic graphite strain electrodes Has activity. The generation of ORR at large positive potentials with many important peak currents is considered to be an important beneficial property of MWNT (SH) -Au NPs / silica nanocomposite catalysts.

The increased catalytic activity of MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) is expected to result from the mutual contribution of MWNT (SH), silica and gold (Au) nanoparticles.

 Due to the even dispersion of the nanotubes and gold nanoparticles, the MWNT (SH) -Au NPs / silica nanocomposites have excellent electrocatalytic activity in the oxygen reduction reaction (ORR). Therefore, the nanocomposite of the present invention is expected as an electrocatalyst of methanol / oxygen fuel cells.

As described above, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. The scope of the present invention is shown by the claims to be described later rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. Should be.

1 shows a scanning electron microscope (FESEM) photograph of MWNT (SH) -Au NPs / silica nanocomposites prepared under different experimental conditions, and a is MWNT (SH) -Au NPs / silica nanocomposites (15: 10:40:30), b is MWNT (SH) -Au NPs / silica nanocomposite (10: 10: 40: 30), c is MWNT (SH) -Au NPs / silica nanocomposite (05:10:40: 30), d is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 80: 30), e is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 10), f Is MWNT (SH) -Au NPs / silica nanocomposite (15: 0: 40: 30), g is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 30) (prepared in the absence of HCl) Are shown respectively.

2 shows EDAX results of MWNT (SH) -Au NPs / silica nanocomposites prepared under different experimental conditions, and a is MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30). , b is MWNT (SH) -Au NPs / silica nanocomposite (10: 10: 40: 30), c is MWNT (SH) -Au NPs / silica nanocomposite (05: 10: 40: 30), d is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 80: 30), e is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 10), f is MWNT (SH)- Au NPs / silica nanocomposites (15: 0: 40: 30), g represent MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) (prepared in the absence of HCl), respectively.

Figure 3 shows the ultra-high pressure electron microscope (HVTEM) image of the MWNT (SH) -Au NPs / silica nanocomposite prepared under different experimental conditions, a is MWNT (SH) -Au NPs / silica nanocomposite (15: 10:40:30), b is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 10), c is MWNT (SH) -Au NPs / silica nanocomposite (15:10: 80:30), and d represents MWNT (SH) -Au NPs / silica nanocomposites (15: 0: 40: 30), respectively.

4 shows ultraviolet spectra of MWNT (SH) -Au NPs / silica nanocomposites prepared under different experimental conditions, and a is MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30). ), b is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 80: 30), c is MWNT (SH) -Au NPs / silica nanocomposite (15: 10: 40: 10), d is MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) (prepared in the absence of HCl) are shown respectively.

5 shows FTIR spectra of MWNT (SH) -Au NPs / silica nanocomposites prepared under different conditions, and (a) shows MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30). ), (b) are MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30), and (c) are MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10 Respectively).

6 shows Raman spectra of MWNT (SH) -Au NPs / silica nanocomposites prepared under different conditions, and (a) shows MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30). ), (b) MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 80: 30), (c) MWNT (SH) -Au NPs / silica nanocomposites (15: 30: 40: 30 ) and (d) are shown for MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 10), respectively.

7 shows 50 mV.s ⁻¹ . (A) MWNT (SH), (b) MWNT-Au nanoparticles, (c) MWNT (SH) -Au NPs / silica nanocomposites (15) at 10 mM Fe (CN) ₆ ^{3- / 4-} (0.1MKCl) 10:40:30) Each of the CVs (Cyclic voltammograms) is shown.

FIG. 8 shows MWNT (SH) -Au NPs / silica nanocomposites (15:10) at 10 mM Fe (CN) ₆ ^{3- / 4-} (0.1MKCl) for various scan rates from 10 to 100 mV ^{· s −1} . The cyclic voltammograms (CVs) of 40:30) are shown, and the internal graph shows the calibration plot.

9 is O ₂ of 50 mV.s ⁻¹ . Each of (a) MWNT (SH), (b) MWNT-Au nanoparticles, (c) MWNT (SH) -Au NPs / silica nanocomposites (15: 10: 40: 30) at saturation 0.5 MH ₂ SO ₄ Cyclic voltammograms (CVs) are shown.

Claims (6)

A nanocomposite in which gold nanoparticles and silica particles are bonded to a sidewall of a thiol functionalized multiwalled carbon nanotube (MWNT) functionalized by a thiol group (-SH). delete A first step of functionalizing a surface of a multiwalled carbon nanotube with a thiol group (-SH) to obtain a thiol functionalized multiwalled carbon nanotube (MWNT (SH)); A second step of mixing the thiol functionalized multi-walled carbon nanotubes (MWNT (SH)) with a silica precursor solution and then stirring; After the addition of HAuCl ₄ and HCl third step of emitting γ-rays; method of manufacturing a nanocomposite comprising a. The method of claim 3, The first step is multi-walled carbon nanotubes (MWNT) to nitric acid (HNO ₃₎ After refluxing, it was filtered using a polycarbonate membrane, and then the residue was washed with water and dried in vacuo to form MWNT-COOH; The MWNT-COOH was refluxed with thionyl chloride (SOCl ₂ ), filtered using a polycarbonate membrane, and the residue was washed with tetrahydrofuran (TETRAHYDROFURAN, THF) and dried at room temperature in vacuo to MWNT- Forming COCl; After refluxing the MWNT-COCl with 4-aminothio phenol (4-aminothio phenol), the residue was washed with water and dried in vacuo to obtain a thiol functionalized multi-walled carbon nanotube (MWNT (SH)). Method for producing a nanocomposite, characterized in that consisting of. The method of claim 3, The second step is any one selected from the group consisting of silica precursor trimethoxysilylpropyl aniline (TMSPA), tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate and mixtures thereof Method for producing a nanocomposite, characterized in that. A platinum (Pt) free electrode catalyst for fuel cells using the nanocomposite of claim 1.

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