KR20130015415A - A fuel cell catalyst support comprosing carbon nanotubes bridged silica-polyaniline and a fuel cell catalyst using the same - Google Patents

Abstract

The present invention relates to a catalyst support for a fuel cell comprising a carbon nanotube crosslinked as an organic-inorganic hybrid, and a catalyst for a fuel cell using the same, and more particularly, to a carbon nanotube formed by crosslinking on a carbon nanotube. A catalyst support for fuel cells consisting of carbon nanobelts of silica-polyaniline and a catalyst for fuel cells incorporating a catalyst metal into the support for fuel cells. The catalyst support for a fuel cell and the fuel cell catalyst using the same according to the present invention have an effect of improving catalyst activity, selectivity and durability.

Description

FUEL CELL CATALYST SUPPORT COMPROSING CARBON NANOTUBES BRIDGED SILICA-POLYANILINE AND A FUEL CELL CATALYST USING THE SAME}

The present invention relates to a catalyst support for a fuel cell comprising a carbon nanotube crosslinked as an organic-inorganic hybrid, and a catalyst for a fuel cell using the same, and more particularly, to a carbon nanotube formed by crosslinking on a carbon nanotube. A catalyst support for fuel cells consisting of carbon nanobelts of silica-polyaniline and a catalyst for fuel cells incorporating a catalyst metal into the support for fuel cells.

In order to increase the energy density and improve the output density and the output voltage, fuel cells need to study electrodes, fuels, and electrolyte membranes. Catalysts used in fuel cells (PEMFC or DMFC) are commonly used alloys between Pt, Pd, Rh, Ru or Pt and other metals. In order to secure price competitiveness, it is necessary to reduce the amount of the metal catalyst used. .

Therefore, as a method of reducing the amount of catalyst while maintaining or increasing the performance of a fuel cell, a conductive carbon material having a large specific surface area is used as a carrier, and Pt and the like are dispersed in fine particles to increase the specific surface area of the catalyst metal. The method is being used. In general, catalysts such as Pt are provided in a paste form, and are uniformly applied on a porous carbon support. However, the degree of dispersion of the catalyst in the support is not uniform and the surface area and the electrical conductivity of the carbon support are not so high.

Carbon nanotubes have good electrical conductivity, excellent mechanical strength, high aspect ratios, and large surface-to-volume ratios, making many attempts to use carbon nanotubes as part of fuel cell electrodes. (Li, et al., Journal of Physical Chemistry, Vol. 107, page 6292 (2003), Wang, et al., Nano Lett. Vol. 4, page 345 (2004)).

The present invention has been made to improve the above-described problems of the conventional fuel cell catalyst, the problem to be solved in the present invention is to provide a catalyst support for a fuel cell comprising a carbon natotube crosslinked with an organic-inorganic mixture.

Another object to be solved by the present invention is to provide a fuel cell catalyst having a catalyst metal supported in the catalyst support for fuel cells of the present invention.

In order to solve the above problems,

The present invention provides a catalyst support for a fuel cell, wherein a silica-polyaniline (PANI) is crosslinked on a carbon nanotube (MWNT) to form a nano belt (NB) of MWNT-silica-PANI.

The present invention also provides a catalyst for a fuel cell, wherein a catalyst metal is supported in the fuel cell support of the present invention.

Preferably, the catalyst metal is selected from the group consisting of Pt, Pd, Co, Fe, Rh, Ru, Pt, Au, Sn, Bi, Cu, Ag, and Ni.

It is preferable that the said catalyst metal is a hollow particle.

The catalyst metal is preferably nanoparticles or nano alloys.

The catalyst support for a fuel cell and the fuel cell catalyst using the same according to the present invention have an effect of improving catalyst activity, selectivity and durability.

1 is a FESEM photograph showing carbon MWNT-silica-PANI-NB,
2 is a FESEM photograph showing hollow gold particles supported on MWNT-silica-PANI-NB,
3 is a graph showing UV spectra of hollow gold particles and hollow gold particles supported on MWNT-silica-PANI-NB, where a is hollow gold particles, b is PTMSPA / hollow gold particles, and c is MWNT-silica-PANI On which hollow gold particles are supported,
4 is a graph showing XRD patterns of hollow gold particles supported on carbon MWNT-silica-PANI-NB, hollow gold particles supported on silica-PANI-NB, and hollow gold particles supported on carbon nanotubes-silica-polyaniline-NB, and a is PTMSPA. B is MWNT-silica-PANI-NB, c is a core shell of hollow gold particles in PTMSPA, d is a hollow gold particle loaded on MWNT-silica-PANI,
5 is a graph showing the electric force of the hollow gold particles supported on MWNT-silica-PANI-NB.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention relates to a catalyst support for a fuel cell comprising a carbon nanotube crosslinked as an organic-inorganic hybrid, and a catalyst for a fuel cell using the same, and more particularly, to a carbon nanotube formed by crosslinking on a carbon nanotube. A catalyst support for fuel cells consisting of carbon nanobelts of silica-polyaniline and a catalyst for fuel cells incorporating a catalyst metal into the support for fuel cells.

Accordingly, the present invention provides a catalyst support for a fuel cell, wherein the silica-polyaniline is crosslinked on the carbon nanotube to form a nano belt of carbon nanotube-silica-polyaniline.

The present invention also provides a catalyst for a fuel cell, wherein a catalyst metal is supported in the fuel cell support of the present invention.

Preferably, the catalyst metal is selected from the group consisting of Pt, Pd, Co, Fe, Rh, Ru, Pt, Au, Sn, Bi, Cu, Ag, and Ni.

It is preferable that the said catalyst metal is a hollow particle.

The catalyst metal is preferably nanoparticles or nano alloys.

Hereinafter, the present invention will be described in more detail by way of examples.

<Examples>

chemical substance

N- [3- (trimethoxy silyl) propyl] aniline (TMSPA) (99%), 3-mercapto propyl trimethoxytosilane (MPTMS), cetyltrimethyl ammonium bromide (CTAB) and ammonium persulfate were used. Multiwalled carbon nanotubes (MWNTs) (10-50 nm in diameter), gold chloride (HAuCl ₄ ) and other chemicals were used as analytical samples. Distilled water was used during the experiment.

Preparation of Carbon Nanotube-Silica-Polyaniline (MWNT-Silica-PANI) Nanobelt (NB)

There are two main steps in the preparation of MWNT-silica-PANI (NB):

a) amine functionalization of MWNTs

Functionalization of MWNTs (MWNT-A) with amine groups and formation of silica-polyaniline (organic-inorganic hybrid) networks between MWNTs resulted in obtaining carbon nanobelts, which were functionalized. Typically, a mixture of MWNTs (200 mg) and (NH ₄ ) ₂ S ₂ O ₈ (50 g) was dispersed in 96% H ₂ SO ₄ (150 mL) by magnetic stirring (6 hours). Once the mixture was seen to disperse (large particulate matter was not seen), for effective dispersion, 2,5-diaminobenzenesulfonic acid (5.7 g) was added and homogenized continuously for 2 hours. Solid NaNO ₂ (2.208 g) was then added and 2,2-azobisisobutyronitrile (1.2 g) was added slowly. This mixture was then placed in an oil bath at 80 ° C. and homogenized continuously for 48 hours. The resulting product was filtered, washed with deionized water and acetone and then dried in a vacuum oven at 50 ° C. for 24 hours.

b) Preparation of MWNT-Silica-PANI-NB

Functionalized TMSPA in 10 mg MWNT (MWNT-f-TMSPA) was dispersed in 20 mL of 0.1 M HCl and sonicated for 5 minutes. To the MWNT-f-TMSPA dispersion, 5 mL of ammonium persulfate (30 mM) was added dropwise at 5 ° C. The dark green precipitate, MWNT-silica-PANI-NB, was filtered, washed with water and dried in a 35 ° C. vacuum oven.

Preparation of MWNT-Silica-PANI (NB) / Au NB Catalyst by Loading Gold Nanostructures into MWNT-Silica-PANI (NB)

Two methods for the loading of typical catalyst particles were used.

i) In the first case, Hollow Gold Particles (HGP) were loaded. The synthesis of HGP is based on templating using cobalt (Co) nanoparticles as initial seeds through galvanic reaction with Au ³⁺ ions, which in this case is a seed metal ion (Co ^{2+ in} this case). ) Is lower than the oxidation state of the metal ion to be reduced (here Au ³⁺ ) (J. Phys. Chem. B 2006, 110, 19935-9944).

ii) In another case, bulk quantities of metal nanoparticles were loaded by heat treatment including thermochemical reactions. In a typical experiment, the calculated amounts of MWNT-A and gold salts were dry mixed and powdered using a mortar and pestle. This solid mixture was heated to 300-350 ° C. for 4 hours. The product was cooled and collected as a powder.

Measurement of Electroactivity and Electrocatalyst

The electrical activity of MWNT (SH) -Au nanoparticles (NPs) / silica-nanocomplex (NC) was measured by cyclic voltammetry in the presence of 10 mM Fe (CN) ₆ ^{3- / 4-} (0.1 M KCl). Inspected by recording. Electrochemical catalytic O ₂ reduction measurements were carried out using a Pt line (secondary), Ag / AgCl (reference) and MWNT (SH) -Au NPs / silica-NC modified Pt disks (working electrodes). In a 0.5 MH ₂ SO ₄ solution saturated with O ₂ .

For electrochemical measurements, the working electrodes were made as follows: A suspension of MWNT (SH) -Au NPs / silica-NC (in 1 mL of DMF) was prepared. A suspension of MWNT (SH) -Au NPs / silica-NC was added dropwise onto a Pt disk electrode (area: 0.07 cm ² ) and dried at room temperature. 5 μL of Nafion (0.25%) solution was placed on the surface of MWNT (SH) -Au NPs / silica composite film and dried at room temperature.

result

The form of MWNT-silica-PANI-NB can be seen by FESEM (FIG. 2). Interestingly, the tubular form of MWNTs has been changed to nanobelt or tape form in the case of MWNT-silica-PANI-NB.

We have incorporated thiol groups into the MWNT-silica-PANI-NBs to support the anchoring of Au NPs or HGPs. The outer diameter of HGPs ranges from 20 to 250 nm, and the thickness of the shell ranges from tens of nanometers. 2 shows FESEM images of HGP distributed MWNT-silica-PANI-NBs. HGPs were found to be uniformly distributed throughout the MWNT-silica-PANI-NBs. Inclusion of -SH groups in MWNT-silica-PANI-NBs provides good fixation of HGPs on the surface of MWNT-silica-PANI-NBs.

UV-visible absorption spectra of HGPs and HGPs distributed MWNT-silica-PANI-NBs are shown in FIG. 3. The absorption spectrum of HGP showed a peak around 570 nm. The spectrum of HGPs distributed MWNT-silica-PANI-NBs showed a peak around 650 nm. The shifting of the peaks compared to pure HGPs is due to the influence of MWNT-silica-PANI-NBs, a matrix that alters the dielectric properties of the medium and shifts the plasmon resonance.

XRD patterns of MWNT-silica-PANI-NB and HGPs distributed MWNT-silica-PANI-NB were shown (FIG. 4). Four peaks located at 2θ values of 38.2, 44.4, 64.7 and 77.7 corresponding to the (111), (200), (220) and (311) lattice planes of cubic Au can be seen in FIG. Peaks are not present at all in the MWNT-silica-PANI-NB (a). This reveals that gold nanoparticles are successfully anchored in MWNT-silica-PANI-NB, further demonstrating the attachment of Au nanoparticles. Importantly, the peaks of the gold nanostructures are stronger in HGPs distributed MWNT-silica-PANI-NB as compared to HGPs distributed silica-PANI-NB (c).

The electroactivity of the HGPs distributed MWNT_silica-PANI-NB modified Pt disk electrode was examined using Fe (CN) ₆ ^{3- / 4-} as redox marker (FIG. 5). The HGPs distributed MWNT-silica-PANI-NB corresponds to Fe (CN) ₆ ^{3- / 4-} with an anodic to cathodic peak potential separation of 130 mV at a scan rate of 50 mV.s ⁻¹ . Redox peaks (260 mV (anode) / 130 mV (cathodic)). CVs of HGPs distributed silica-PANI-NB were recorded for different scan rates (10-100 mV.s ⁻¹ ).

The new material MWNT-silica-PANI-NB has special features for use as a support matrix for catalysts in fuel cell applications. The matrix can provide outstanding catalytic performance that was not expected when using existing catalyst supports such as pristine MWNTs and other carbon materials such as Vulcan, carbon black and the like. MWNT-silica-PANI-NB includes MWNTs, porous silica and conductive polymers in the form of connected networks. The three components in the MWNT-silica-PANI-NB are known to have individual characteristics on catalyst performance. The greatest advantage of the use of nanostructured materials is their high external surface area, which can dramatically increase the contact area between reactants and active sites, and in particular, significantly reduces dispersion problems in liquid reaction media.

The inventors have adopted a novel method for producing a good catalyst support for fuel cells. We used a novel method to interconnect tubular carbon structures using silica-polyaniline crosslinks to obtain a new kind of MWNT-silica-PANI (organic-inorganic hybrid) nanobelt as a result. Incorporation of nitrogen into the carbon matrix has been a widely used method for adjusting the structural, chemical and electrical properties of the resulting carbon. We have designed the method of the present invention to have nitrogen doping of CNTs using PANI links.

Thus, the MWNT-silica-PANI (organic-inorganic hybrid) nanobelt matrix has proven to be suitable for catalyst loading. Synergistic effects such as high surface area, durability and presence are also provided.

Claims (5)

A catalyst support for a fuel cell, wherein silica-polyaniline is crosslinked on carbon nanotubes to form a nano belt of carbon nanotubes-silica-polyaniline. A catalyst for a fuel cell, wherein a catalyst metal is supported in the catalyst support for fuel cell of claim 1. The method of claim 2,
The catalyst metal is a fuel cell catalyst, characterized in that at least one selected from the group consisting of Pt, Pd, Co, Fe, Rh, Ru, Pt, Au, Sn, Bi, Cu, Ag, Ni. The method of claim 2,
The catalyst metal is a catalyst for a fuel cell, characterized in that the hollow particles. The method of claim 2,
The catalyst metal is a catalyst for a fuel cell, characterized in that the nanoparticles or nano alloys.

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