KR100834008B1 - Metal catalyst electrode supported on conductive polymer and fuel cell comprising same - Google Patents

Abstract

A metal catalyst electrode, and a fuel cell containing the metal catalyst electrode are provided to improve the electrochemical properties of a catalyst electrode by using a metal particle. A metal catalyst electrode comprises a conductive polymer support having the oxidation/reduction activity; and 1-10 % of a metal particle which is supported on the conductive polymer support by electroplating. Preferably the conductive polymer has a conjugated structure, is selected from polyaniline, polypyrrole, polythiophene, polyacetylene and their mixture, and is doped with an organic acid or an inorganic acid. Preferably the metal is selected from Pt, Ru, Ni, Co and an alloy comprising their mixture.

Description

Metal catalyst electrode supported on conductive polymer and fuel cell comprising same {METAL CATALYST ELECTRODE SUPPORTED IN CONDUCTIVE POLYMER AND FUEL CELL COMPRISING SAME}

FIG. 1 shows the results of X-ray diffraction analysis of a metal catalyst electrode supported on a conductive polymer support according to Examples 1 to 5. FIG.

Figure 2 shows the X-ray diffraction analysis of the metal catalyst electrode supported on the graphite nanofiber support according to Comparative Examples 1 to 4.

3 shows the electrochemical activity of the metal catalyst electrode supported on the conductive polymer support according to Examples 1 to 5.

Figure 4 shows the electrochemical activity of the metal catalyst electrode supported on the graphite nanofiber support according to Comparative Examples 1 to 4.

The present invention relates to a metal catalyst electrode having excellent electrochemical activity and a fuel cell comprising the same.

Unlike ordinary batteries, fuel cells do not require replacement or recharging of batteries, and supply gas or liquid fuel to convert chemical energy into electrical energy through an electrochemical reaction. The advantage of the fuel cell is that it can be used for various fuels as a highly efficient and eco-friendly energy source, and can be manufactured for various application aspects by adjusting the volume according to the type of fuel. That is, a variety of applications are possible from mobile power supplies such as mobile portable devices, power supplies for transportation of automobiles, and distributed power supplies that can be used for home and power businesses.

Fuel cells can be classified according to the fuel used and the operating temperature. These include AFCs (alkaline fuel cells), PAFCs (phosphate fuel cells), MCFCs (molten carbonate fuel cells), SOFCs (solid oxide fuel cells), PEMFCs (polymer electrolyte fuel cells), and DMFCs (direct methanol fuel cells). . Among various types of fuel cells, PEMFCs and DMFCs can be used as power sources for mobile devices.

The most commonly used catalysts for the anode and cathode electrode materials of fuel cells are noble metal catalysts such as platinum, and it is common to manufacture a catalyst electrode by supporting such a noble metal catalyst on a carbon support. Precious metal catalysts are very expensive and there is a need to reduce the amount of loading without significantly reducing the electrochemical catalyst activity, and it is important to make the catalyst particles small in size and to be uniformly supported on the support.

On the other hand, as a general method of supporting a metal catalyst on a catalyst support, there is a chemical supporting method in which a metal salt precursor such as platinum is adsorbed on the support and then the metal is reduced using a reducing agent or hydrogen gas. Such a chemical supporting method has a long processing time, a large amount of catalyst may be present in an inactive state, and the electrode manufacturing process and the electrode structure may be complicated, resulting in a fuel cell price increase.

Another method for producing a metal catalyst electrode is an electrochemically supported method, that is, a method of reducing a metal catalyst by adsorbing a catalyst metal precursor to a carbon support and then applying a voltage. The electrochemical supporting method is simpler than the general chemical supporting method and the processing time is short, which can greatly contribute to cost reduction and catalyst performance improvement.

The catalyst support should have a large surface area, large pore volume and high conductivity in the preparation of the catalyst electrode by the electrochemical supporting method. Carbon materials such as graphite nanofibers, which are widely used, have irregular pore structure, low pore volume, low conductivity, etc. In order to use it as a catalyst support, it is generally used in combination with Nafion ^™ . In addition, carbon black having a large specific surface area and excellent electrical conductivity is quite expensive and has a cost problem.

Thus, the present inventors can significantly improve the electrochemical activity of the catalyst in an economical manner when the metal catalyst particles are electrochemically supported on the conductive polymer having a lower cost and redox activity instead of the carbon support as the catalyst support. Discovered and completed the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal catalyst having excellent electrochemical activity and a fuel cell including the same, which are obtained by introducing a new and unknown material.

In accordance with the above object, the present invention provides a metal catalyst electrode in which metal particles are supported on a conductive polymer having redox activity.

Hereinafter, the present invention will be described in detail.

The metal catalyst electrode according to the present invention is characterized in that a conductive polymer is used as a support and metal particles are evenly loaded thereon. Specifically, a voltage is applied after the conductive polymer-attach electrode is inserted into a solution in which the metal particle precursor is dispersed. It can be prepared by supporting the metal particles in the conductive polymer by the electrical redox action.

The electrochemical supporting method applied in the present invention can easily control the size and content of the catalyst in a short time.

In the present invention, the conductive polymer used as the catalyst support has the same electrical conductivity as the conventional carbon support to transfer electrons to the catalyst, and also generates a current upon application of voltage by redoxing itself. Accordingly, the electrical activity of the catalyst can be improved.

The conductive polymer having redox activity usable in the present invention has a conjugated structure having a π bond in the main chain, and preferred examples thereof include polyaniline, polypyrrole, polythiophene, polyacetylene or mixtures thereof. . These compounds may be prepared by known methods or used by purchasing a commercial item.

Such conductive polymers may be doped with inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, or organic acids such as dodecylbenzenesulfonic acid, camphorsulfonic acid and toluene sulfonic acid to improve electrical conductivity. Doping of the conductive polymer may be performed before the polymer is added to the metal catalyst precursor solution, or may be performed by injecting the polymer together with the organic or inorganic acid in the precursor solution, wherein the organic acid or the inorganic acid has a molecular number of doping acid per unit of the conductive polymer monomer. Preference is given to using in amounts that are from 10 to 50%.

In the present invention, metals that can be used as catalyst components include alloys composed of Pt, Ru, Ni, Co, and combinations thereof, and these metals are in the form of precursor compounds in a concentration of 5 to 50 mM in water or an organic solvent. Distributed.

In the metal catalyst electrode according to the present invention, the average particle size of the catalyst supported on the conductive polymer support is 2 to 10 nm, preferably 3 to 8 nm, and the catalyst of this size is supported on the support at a level of 1 to 10%. do.

The metal catalyst electrode of the present invention has a current density at 900 mV of −4 × 10 ⁻³ to 1.5 × 10 ⁻² , which shows excellent electrochemical activity.

In the metal catalyst electrode of the present invention as described above, metal particles are added to the conductive polymer by applying a voltage for a predetermined time after inserting the electrode, the counter electrode, and the reference electrode to which the conductive polymer is attached as a working electrode to the dispersion solution of the metal catalyst precursor. After supporting, the solid powder can be prepared by filtration, washing and drying. At this time, the supporting time of the metal catalyst varies depending on the applied voltage condition, but it is preferably about 15 to 30 minutes, and if the supporting time is too long, agglomeration of the catalyst occurs and the electrochemical activity is reduced.

In this way, the metal catalyst obtained by supporting the metal particles in the conductive polymer capable of redox action by the electrochemical support method can be effectively used in fuel cells as the electrochemical properties are improved as the redox property of the conductive polymer support is added. have.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1

First, to prepare polyaniline to be used as a catalyst support, it was put in 500 ml of 1M HCl in an ice bath to 5 ° C, and then 5 ml of aniline and 100 ml of 0.06 M ammonium persulfate were added. After 24 hours, the mixture was washed with ethanol and water, filtered and dried for 24 hours.

In order to carry out the electrochemical loading of the catalyst, a glassy carbon electrode obtained by attaching the polyaniline obtained above as a working electrode to a solution in which a 1: 1 mixture of 20 mM H ₂ PtCl ₆ and 20 mM RuCl ₃ was dispersed in ethylene glycol, Pt as a counter electrode Ag / AgCl was inserted as the line and reference electrode, and then voltage was applied at a potential of −0.2 to 0.7V and a pulse interval of 0.03 seconds for 6 minutes. The solid powder was then filtered, washed with distilled water and dried to give a catalyst electrode in which platinum-ruthenium particles were supported in polyaniline in the size and amount as shown in Table 1 below.

Examples 2-4

The same process as in Example 1 was carried out except that the supporting time was 12 minutes, 24 minutes, and 36 minutes, respectively.

Example 5

The same process as in Example 1 was carried out except that 500 ml of 1M dodecylbenzenesulfonic acid was used instead of 1M HCl in preparing polyaniline to be used as a catalyst support and the holding time was 24 minutes.

Comparative Example 1

A platinum-ruthenium catalyst supported on GNF was obtained in the same manner as in Example 1 except that graphite nanofiber (GNF) powder was used instead of polyaniline as the catalyst support.

Comparative Examples 2 to 4

The same process as in Comparative Example 1 was carried out except that the supporting time was 12 minutes, 24 minutes, and 36 minutes, respectively.

X-ray diffraction (XRD) analysis results of the platinum-ruthenium catalyst electrode prepared in Examples 1 to 5 and Comparative Examples 1 to 4 are shown in FIGS. 1 and 2, respectively, and are calculated from the XRD analysis results. The average size of the supported catalyst particles, and the catalyst loading measured by an inductively coupled plasma-atomic emission spectrometer (ICP-AES) are shown in Table 1 below.

From Table 1, all of the metal catalysts supported on the conductive polymer polyaniline and the GNF support of the carbon material are dispersed evenly as the supporting time increases, but after 24 minutes, the agglomeration of particles occurs to increase the size and the supporting amount. You can see the decrease.

In addition, in order to analyze the electrical activity of the supported metal catalyst, the prepared catalyst powder is well dispersed with Nafion and then attached to a glassy carbon electrode and dried, and a platinum foil as a counter electrode. And a voltage-current curve was measured by cyclic voltammetry in a range of 300 mV to 1100 mV in a 0.5 MH ₂ SO ₄ and 1.0 M CH ₃ OH mixed solution using Ag / AgCl as a reference electrode.

3 and 4 show the electrochemical activity of the metal catalyst electrodes prepared according to Examples 1 to 5 and Comparative Examples 1 to 4, respectively, from which they were carried in polyaniline as conductive polymers according to Examples 1 to 5, respectively. It can be seen that the electrical activity is remarkably excellent despite the fact that the metal catalyst electrode has a smaller amount of particles than the catalyst electrodes of Comparative Examples 1 to 4 supported on the GNF support, which is a carbon material. In particular, the catalyst supported according to Example 3 showed the best results because the catalyst particles were uniformly dispersed without agglomeration and were supported by the smallest particle size.

In the metal catalyst electrode according to the present invention, the metal particles are supported by the electrochemical method in the conductive polymer having redox activity, thereby exhibiting excellent electrochemical activity compared to the conventional catalyst electrode.

Claims (9)

A metal catalyst electrode in which metal particles are supported by electroplating on a conductive polymer support having redox activity. delete The method of claim 1, The metal catalyst electrode, characterized in that the metal particles are supported on the conductive polymer support in an amount of 1 to 10%. The method of claim 1, A metal catalyst electrode, characterized in that the conductive polymer has a conjugated structure. The method of claim 4, wherein A metal catalyst electrode, characterized in that the conductive polymer is selected from polyaniline, polypyrrole, polythiophene, polyacetylene and mixtures thereof. The method of claim 5, wherein A metal catalyst electrode, characterized in that the conductive polymer is doped with an organic or inorganic acid. The method of claim 6, A metal catalyst electrode, wherein the organic acid is dodecylbenzenesulfonic acid, camphorsulfonic acid, or toluene sulfonic acid, and the inorganic acid is sulfuric acid, hydrochloric acid, or nitric acid. The method of claim 1, A metal catalyst electrode, characterized in that the metal is selected from alloys consisting of Pt, Ru, Ni, Co and combinations thereof. A fuel cell comprising the metal catalyst electrode according to any one of claims 1 to 10.

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