KR100774590B1 - Supported catalyst for fuel cell and method of producing the same - Google Patents

Abstract

A supported catalyst for a fuel cell, a method for preparing the supported catalyst, a membrane electrode assembly containing the supported catalyst, and a fuel cell containing the supported catalyst are provided to increase the active surface area with increasing the content of a metal catalyst component. A supported catalyst comprises a carbon-based support; and a transition metal nanoparticle supported on the carbon-based support, wherein the transition metal nanoparticle has an average diameter of 1-5 nm, the weight of the transition metal nanoparticle to the total weight of the carbon-based support and the transition metal nanoparticle is 60 wt% or more, and the supported catalyst has a specific surface area of 10-1,000 m^2/g. Preferably the carbon-based support is carbon nanotube, carbon nanowire, carbon nanofiber, carbon nanohorn, carbon nanoring, activated carbon, acetylene black, graphite or their mixture.

Description

Supported catalyst for fuel cell and method of producing the same

1 is a graph showing the results of X-ray diffraction (XRD) analysis performed on the supported catalyst prepared according to Examples 1 to 3 of the present invention.

2 is a transmission electron microscope (TEM) photograph of a supported catalyst prepared according to Example 4 of the present invention.

3 is a graph showing the results of X-ray diffraction (XRD) analysis performed on the supported catalyst prepared according to Example 4 of the present invention.

4A and 4B are transmission electron microscope (TEM) photographs of a supported catalyst prepared according to Example 5 of the present invention.

5 is a graph showing the results of X-ray diffraction (XRD) analysis performed on the supported catalyst prepared according to Example 5 of the present invention.

6 is a graph showing the results of X-ray diffraction (XRD) analysis performed on the supported catalyst prepared according to Comparative Examples 1 to 3 of the present invention.

7A to 7C are TEM photographs of a supported catalyst or a transition metal black catalyst prepared according to Examples 1, 6, and 7 of the present invention.

8 is a graph showing the results of X-ray diffraction (XRD) analysis performed on the supported catalyst or the transition metal black catalyst prepared according to Examples 1, 6 and 7 of the present invention.

The present invention relates to a supported catalyst for a fuel cell and a method of manufacturing the same, and more particularly, to a supported catalyst that is small in particle size and easily supported on carbon nanotubes so as to have a high active surface area while having a high content of a metal catalyst component. A catalyst and a method for producing the same.

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

In the fuel cell, hydrogen or fuel is supplied to the anode electrode, oxygen is supplied to the cathode electrode, and electricity is generated by an electrochemical reaction between the anode electrode and the cathode electrode. Oxidation reaction of hydrogen or organic raw materials occurs at the anode, and reduction reaction of oxygen occurs at the cathode to generate a voltage difference between the two electrodes.

A fuel cell generally has a form in which an anode electrode and a cathode electrode are in close contact with both surfaces of an electrolyte membrane with respect to an electrolyte membrane that delivers protons generated from the anode. Each electrode includes a catalyst layer and a diffusion layer, the catalyst layer serving to promote the chemical reaction carried out at the electrode, the diffusion layer promotes the diffusion and material transfer of the reactants and products of the chemical reaction.

The catalyst layer generally includes a metal particle for catalyzing, a carrier for supporting the metal particle, and a binder for connecting the carrier in the form of particles to maintain the shape. In order to increase the reaction speed of the fuel cell, it is preferable to maximize the surface area by reducing the size of the metal particles. In recent years, with the efforts to reduce the size of the metal particles, studies on a method of supporting a large amount of the metal catalyst on the carrier are actively underway.

In the case of the polymer electrolyte membrane fuel cell (PEMFC), 20 wt% Pt / C catalyst or 20 wt% Pt-Ru / C catalyst has been used in the past, and now, 40 wt% catalyst is used for the research. Where weight percent is the weight percentage of the weight of the metal component to the weight of the total supported catalyst). On the other hand, direct methanol fuel cells (DMFCs) are less active than PEMFCs and therefore require a large amount of catalyst. Therefore, a large amount of metal particles is required, and since the volume of the carrier occupies most of the volume of the catalyst layer, there is a problem in that the volume of the catalyst layer for accommodating a large amount of metal particles increases rapidly in proportion.

As such, when the thickness of the electrode layer is thick, it is difficult to miniaturize the application, and in some cases, it may lead to damage of the electrode. Therefore, there is a high demand for a high supported catalyst for supporting a large amount of metal particles on a small carrier. Here, the high supported catalyst means a catalyst in which the amount of the carrier contained in the catalyst is reduced and the amount of the metal particles is increased. Recently, commercial products of 60 wt% or 80 wt% Pt / C have been published, but little is known about the techniques for the production of higher supported catalysts. However, the sale and / or research for the catalyst without a carrier is in progress, but in the absence of the carrier, since the metal particles easily aggregate and increase in size, the active surface area is reduced and overall performance is not so high.

However, the high surface area, such as the particle size of such a commercially available high supported catalyst, has not been achieved, which is presumably due to the heat treatment process accompanying the catalyst production. In addition, according to the prior art, the supporting properties of the transition metal particles vary depending on the type of the carbon-based carrier, and thus are restricted from using a carbon-based carrier having excellent physical properties such as carbon nanotubes or carbon nanofibers, which have recently been spotlighted. There was a downside.

The first technical problem to be achieved by the present invention is to provide a supported catalyst for a fuel cell that can be easily supported and supported on a carbon-based carrier such as carbon nanotubes, while maintaining a small active particle size and having a high active surface area.

The second technical problem to be achieved by the present invention is to provide a method for preparing a supported catalyst for a fuel cell that can be easily supported and supported on a carbon-based carrier such as carbon nanotubes while maintaining a small particle size.

The third technical problem to be achieved by the present invention is to provide a method for producing a transition metal black catalyst that can be kept without a particle size while being prepared without a carrier.

The fourth technical problem to be achieved by the present invention is to provide a membrane electrode assembly including the supported catalyst for a fuel cell of the present invention.

The fifth technical problem to be achieved by the present invention is to provide a fuel cell comprising the supported catalyst for a fuel cell of the present invention.

The present invention comprises a carbon-based carrier and the transition metal nanoparticles supported on the carbon-based support, to achieve the first technical problem, the average particle diameter of the transition metal nanoparticles is 1 to 5 nm, the carbon-based support And a supported catalyst having a weight of 60 wt% or more of the transition metal nanoparticles relative to the total weight of the transition metal nanoparticles.

The present invention provides a uniform dispersion by dispersing a transition metal precursor, a carbon-based carrier, a surfactant and a reducing agent in a solvent to achieve the second technical problem; Reacting the dispersion; First heat treating the reaction product in a reducing atmosphere; Performing a second heat treatment of the first heat treatment product in an oxidizing atmosphere; And a third heat treatment of the second heat treatment product in a reducing atmosphere.

The present invention provides a uniform dispersion by dispersing a transition metal precursor, a surfactant and a reducing agent in a solvent to achieve the third technical problem; Reacting the dispersion; First heat treating the reaction product in a reducing atmosphere; Performing a second heat treatment of the first heat treatment product in an oxidizing atmosphere; And a third heat treatment of the second heat treatment result in a reducing atmosphere.

The present invention, the cathode comprising a catalyst layer and a diffusion layer to achieve the fourth technical problem; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst according to the present invention. to provide.

The present invention to achieve the fifth technical problem, the cathode comprising a catalyst layer and a diffusion layer; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst according to the present invention. .

Hereinafter, the present invention will be described in more detail.

A first aspect of the present invention includes a carbon-based carrier and transition metal nanoparticles supported on the carbon-based carrier, wherein the transition metal nanoparticles have an average particle diameter of 1 to 5 nm, and the carbon-based carrier and transition metal nanoparticles. It provides a supported catalyst that the weight of the transition metal nanoparticles relative to the total weight of 60% by weight or more. The weight of the transition metal nanoparticles relative to the total weight of the carbonaceous carrier and the transition metal nanoparticles is more preferably 75% by weight or more.

The carbon-based carrier is a porous substrate having a high surface area and has a large number of pores therein, so that it is possible to carry a metal catalyst having a weight greater than its own weight. However, although the ratio of the weight of the transition metal nanoparticles to the weight of the carbon-based carrier may have an extremely large value (for example, 100 or more), it is generally referred to the total weight of the carbon-based carrier and the transition metal nanoparticles. The weight of the transition metal nanoparticles is within 99% by weight and more generally within 95% by weight. Although the weight fraction of the transition metal nanoparticles is higher than this, there is no big problem as long as the surface area for maintaining high activity is secured.

The carbonaceous carrier may be, for example, carbon nanotubes, carbon nanowires, carbon nanofibers, carbon nanohorns, carbon nanorings, activated carbon, acetylene black, graphite, or mixtures thereof, but is not limited thereto. no.

The transition metal is, for example, platinum (Pt), ruthenium (Ru), osmium (Os), cobalt (Co), palladium (Pd), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al) or alloys thereof, but is not limited thereto. The alloy of these transition metals may be an alloy of two or more metals.

Platinum is a representative metal catalyst of a transition metal component commonly used in electrodes of fuel cells, and ruthenium is generally alloyed to improve carbon monoxide endothelial toxicity.

These transition metals are present on the surface of the carbonaceous carrier in the form of nanoparticles. The average particle diameter of the transition metal nanoparticles is preferably 1 nm to 5 nm. If the particle diameter is smaller than 1 nm, the size is too small to lose activity as a catalyst. If the particle diameter is larger than 5 nm, the active surface area of the catalyst decreases, thereby rapidly decreasing the mass activity. It is not desirable to do so. The average particle diameter of the transition metal nanoparticles is more preferably 2 nm to 4 nm.

The specific surface area of the supported catalyst may be 10 m ² / g to 1000 m ² / g. If the specific surface area of the supported catalyst is less than 10 m ² / g, the active surface area is too narrow, the activity of the supported catalyst may be insufficient, the specific surface area of the supported catalyst is more than 1000 m ² / g is difficult to manufacture It can become too small and lose activity.

A second aspect of the present invention comprises the steps of dispersing the transition metal precursor, the carbon-based carrier, the surfactant and the reducing agent in a solvent to prepare a uniform dispersion; Reacting the dispersion; First heat treating the reaction product in a hydrogen atmosphere; Performing a second heat treatment of the first heat treatment product in an oxygen atmosphere; And a third heat treatment of the second heat treatment product in a hydrogen atmosphere.

The dispersion is 1 part by weight to 70 parts by weight of a carbon-based carrier, 100 parts by weight to 400 parts by weight, 100 parts by weight to 400 parts by weight of reducing agent, and 100 parts by weight of a solvent based on 100 parts by weight of the transition metal precursor of the transition metal precursor. To 5000 parts by weight may be prepared by mixing uniformly. The content of the carbonaceous carrier may be appropriately selected depending on the desired loading of the supported catalyst. When the content of the surfactant is less than 100 parts by weight, there is a fear that the dispersion of the transition metal nanoparticles is insufficient, and when the content of the surfactant exceeds 400 parts by weight, the effect of adding the surfactant is saturated, which is uneconomical. In addition, if the content of the reducing agent is less than 100 parts by weight, the transition metal nanoparticles may not be sufficiently reduced, there is a risk of loss of the transition metal precursor, and if the content of the reducing agent exceeds 400 parts by weight, the effect of the addition of the reducing agent is saturated. It is uneconomical. The amount of the solvent may be appropriately selected depending on the amount of the reactants.

These reaction mixtures may be mixed at a time to produce a uniform dispersion, or alternatively, the transition metal precursor and the carbonaceous carrier may be first dispersed sufficiently in a solvent, followed by addition of a reducing agent and a surfactant to prepare the dispersion.

The transition metal precursor is a salt of a transition metal, and the transition metal is, for example, platinum (Pt), ruthenium (Ru), osmium (Os), cobalt (Co), palladium (Pd), gallium (Ga), Titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), or aluminum (Al), but are not limited thereto It is not. The transition metal precursor may be, but is not limited to, acetates, nitrates, sulfates, chlorides, nitrides, oxides, sulfides, hydrates, carbides, and the like of such transition metals.

The carbonaceous carrier may be the carbonaceous carrier described above.

As the surfactant, nonionic interfaces such as sorbitan monooleate, POE sorbitan monooleate, N, N'-dimethylformamide dicyclohexyl acetal, polyoxyethylene alkylamine, glycerol, fatty acid ester, and the like Active agent; Cationic surfactants such as amine salts and quaternary ammonium salts; Anionic surfactants such as di-alkyl sulfosuccinate, alkyl-alphasulfocarbonate, petroleum sulfonate, alkylnaphthalenesulfonate salts, phosphate ester salts and alkyl phosphates; N-lauryl-beta-acetic acid, N-lauryl-beta-aminopropionic acid, N-lauryl-betaaminobutyric acid (N-lauryl-beta-acetic acid) Amphoteric surfactants, such as (beta) -aminobutyric acid), an aminocarboxylic acid, and a betaine salt, etc. can be used, but it is not limited to this.

As the reducing agent for the transition metal precursor, sodium borohydride (NaBH ₄ ) may be used, but the present invention is not limited thereto.

In particular, it is preferable that it is tetraoctylammonium hydrotriethylborate which can also function as a reducing agent as well as a surfactant.

The solvent is not particularly limited as long as it is a single component or a multi component solvent capable of uniformly dispersing the reaction mixture, but is not limited to halogen, alcohol, ketone, ester, aliphatic hydrocarbon, aromatic hydrocarbon, ether solvent, or these solvents. Mixtures of may be used. Specific and non-limiting examples thereof include water, acetone, methanol, ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, dimethylacetamide (DMAc), dimethylimidazoline (DMI), dimethylformamide, tetrachloro Ethane, dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), tetrabutyl acetate, n-butyl acetate, m-cresol, toluene, xylene ( xylene), ethylene glycol (EG), γ-butyrolactone, or hexafluoroisopropanol (HFIP), and the like, which may be used alone or in combination. In particular, it is preferable to use tetrahydrofuran.

The reaction mixture mixed as above is reacted for 2 to 36 hours at a temperature of 20 ° C to 70 ° C, preferably with stirring. The reaction time may be longer or shorter depending on the amount of reactants and other experimental conditions.

After the reaction, the surfactant surrounds the surface of the transition metal nanoparticles. As described above, these surfactants are organic materials, and when thermally treated in an oxidizing atmosphere, a combustion reaction of the surfactant occurs, and a very high temperature is locally formed on the surface of the transition metal nanoparticles. This high temperature leads to particle growth through aggregation of the transition metal nanoparticles resulting in excessive growth of the size of the transition metal nanoparticles. Therefore, there is a need for a method of gradually removing the organic material surrounding the surface of the transition metal nanoparticles so as not to cause rapid combustion.

As such, the reaction product is first subjected to a first heat treatment in order to gradually remove the organic material. The first heat treatment may be performed in a reducing atmosphere for thermal decomposition of the organic material, and may be performed at a temperature of about 200 ° C. to about 500 ° C. If the first heat treatment temperature is less than 200 ℃ thermal decomposition of the organic material surrounding the transition metal nanoparticles may be insufficient, if the first heat treatment temperature exceeds 500 ℃ there is a fear that the particle size may grow, which is not preferable.

The first heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the first heat treatment is shorter than 1 minute, thermal decomposition of the organic material surrounding the transition metal nanoparticles may be insufficient. If the execution time of the first heat treatment is longer than 60 minutes, the effect of the heat treatment may be saturated and uneconomical. to be.

The second heat treatment is performed following the first heat treatment. The second heat treatment may be performed in an oxidizing atmosphere to burn the organic material, and may be performed at a temperature of about 200 ° C. to about 500 ° C. Since decomposition of the organic material which can be thermally decomposed has already been performed in the first heat treatment, even if a combustion reaction occurs in the second heat treatment, the growth of metal nanoparticles due to this can be prevented to a large extent. If the second heat treatment temperature is less than 200 ° C, it may not be sufficient to remove organic substances such as surfactant, and if the second heat treatment temperature exceeds 500 ° C, the particle size may grow excessively, which is not preferable.

The second heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the second heat treatment is shorter than 1 minute, it may not be sufficient to remove organic substances such as a surfactant. If the execution time of the second heat treatment is longer than 60 minutes, the effect of the heat treatment is saturated, which is uneconomical.

The third heat treatment is performed following the second heat treatment. The third heat treatment may be performed in a reducing atmosphere again to reduce transition metal nanoparticles that may have been oxidized in the combustion reaction, and may be performed at a temperature of about 200 ° C. to about 500 ° C. If the third heat treatment temperature is less than 200 ℃, the reduction of the transition metal nanoparticles may be insufficient to reduce the catalytic activity, and if the third heat treatment temperature exceeds 500 ℃ there is a possibility that the particle size may grow excessively is not preferable.

The third heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the third heat treatment is shorter than 1 minute, the reduction of transition metal nanoparticles may be insufficient, and the catalytic activity may be reduced. If the execution time of the third heat treatment is longer than 60 minutes, the effect of the heat treatment is saturated, which is uneconomical. .

The temperature of the first to third heat treatment is more preferably carried out at a temperature of 250 ℃ to 350 ℃, respectively.

The reducing atmosphere of the first heat treatment and / or the third heat treatment may be formed by, for example, adding a reducing gas to the inert gas so as to include 5% by volume to 30% by volume of the reducing gas. The reducing gas may be, for example, hydrogen, but is not limited thereto.

The oxidative atmosphere of the second heat treatment may be formed by, for example, adding an oxidizing gas to the inert gas so as to include 5% by volume to 30% by volume of the oxidizing gas. The oxidizing gas may be, for example, oxygen, but is not limited thereto.

The inert gas may be, for example, a gas such as nitrogen (N ₂ ), helium (He), neon (Ne), argon (Ar), but is not limited thereto.

The first to third heat treatments may be performed using an apparatus having a closed heating space, such as an oven, for example, and is not particularly limited. Preferably, it is preferable to continuously supply the reducing gas or the oxidizing gas and to continuously discharge the gas in the heat treatment space so that the reducing atmosphere or the oxidizing atmosphere can be kept constant.

According to a general method for preparing a supported catalyst, it is difficult to support a metal catalyst well on various carbon-based carriers. That is, in order to change the carbon-based support, any method that can be applied to any particular carbon-based support generally requires a pretreatment of a new carbon-based support. According to the production method of the supported catalyst of the present invention, the supported catalyst can be easily produced without being influenced by the kind of the carbon-based carrier.

A third aspect of the invention provides a method for preparing a uniform dispersion comprising dispersing a transition metal precursor, a surfactant and a reducing agent in a solvent; Reacting the dispersion; First heat treating the reaction product in a reducing atmosphere; Performing a second heat treatment of the first heat treatment product in an oxidizing atmosphere; And a third heat treatment of the second heat treatment result in a reducing atmosphere.

The method for preparing a transition metal black catalyst relates to a method for preparing a transition metal black catalyst not supported on a carbon-based carrier, and is a catalyst composed only of transition metal particles.

The dispersion may be prepared by uniformly mixing 100 parts by weight to 400 parts by weight of surfactant, 100 parts by weight to 400 parts by weight, and 100 parts by weight to 5000 parts by weight of a solvent based on 100 parts by weight of the transition metal precursor of the transition metal precursor. have. If the content of the surfactant is less than 100 parts by weight, there is a fear that the dispersion of the transition metal nanoparticles is insufficient. If the content of the surfactant exceeds 400 parts by weight, the effect of adding the surfactant is saturated and uneconomical. . In addition, when the content of the reducing agent is less than 100 parts by weight, the transition metal nanoparticles may not be sufficiently reduced, there is a fear that the activity of the supported catalyst prepared is insufficient, if the content of the reducing agent exceeds 400 parts by weight to the addition of the reducing agent The effect is saturated and uneconomical. The amount of the solvent may be appropriately selected depending on the amount of the reactants.

These reaction mixtures may be mixed at a time to produce a uniform dispersion, or alternatively, the transition metal precursor and the carbonaceous carrier may be first dispersed sufficiently in a solvent, followed by addition of a reducing agent and a surfactant to prepare the dispersion.

The transition metal precursor is a salt of the transition metal, which is the same as in the description of the second aspect of the present invention.

The said surfactant and a reducing agent are the same as the description regarding the 2nd aspect of this invention. In particular, it is preferable that it is tetraoctylammonium hydrotriethylborate which can also function as a reducing agent as well as a surfactant.

The solvent is the same as in the description of the second aspect of the present invention.

The reaction mixture mixed as above is reacted for 2 to 36 hours at a temperature of 20 ° C to 70 ° C, preferably with stirring. The reaction time may be longer or shorter depending on the amount of reactants and other experimental conditions.

After the reaction, the surface of the transition metal nanoparticles are surrounded by a surfactant. As described above, these surfactants are organic materials, and when thermally treated in an oxidizing atmosphere, a combustion reaction of the surfactant occurs, and a very high temperature is locally formed on the surface of the transition metal nanoparticles. This high temperature leads to particle growth through aggregation of the transition metal nanoparticles resulting in excessive growth of the size of the transition metal nanoparticles. Therefore, there is a need for a method of gradually removing the organic material surrounding the surface of the transition metal nanoparticles so as not to cause rapid combustion.

As such, the reaction product is first subjected to a first heat treatment in order to gradually remove the organic material. The first heat treatment may be performed in a reducing atmosphere for pyrolysis of the organic material, and may be performed at a temperature of about 200 ° C. to about 500 ° C. If the first heat treatment temperature is less than 200 ℃ thermal decomposition of the organic material surrounding the transition metal nanoparticles may be insufficient, if the first heat treatment temperature exceeds 500 ℃ there is a fear that the particle size may grow, which is not preferable.

The first heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the first heat treatment is shorter than 1 minute, thermal decomposition of the organic material surrounding the transition metal nanoparticles may be insufficient. If the execution time of the first heat treatment is longer than 60 minutes, the effect of the heat treatment is saturated, which is uneconomical. to be.

The second heat treatment is performed following the first heat treatment. The second heat treatment may be performed in an oxidizing atmosphere to burn the organic material, and may be performed at a temperature of about 200 ° C. to about 500 ° C. Since decomposition of the organic material which can be thermally decomposed has already been performed in the first heat treatment, even if a combustion reaction occurs in the second heat treatment, the growth of metal nanoparticles due to this can be prevented to a large extent. If the second heat treatment temperature is less than 200 ° C, it may not be sufficient to remove organic substances such as surfactant, and if the second heat treatment temperature exceeds 500 ° C, the particle size may grow excessively, which is not preferable.

The second heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the second heat treatment is shorter than 1 minute, it may not be sufficient to remove organic substances such as a surfactant. If the execution time of the second heat treatment is longer than 60 minutes, the effect of the heat treatment is saturated, which is uneconomical.

The third heat treatment is performed following the second heat treatment. The third heat treatment may be performed in a reducing atmosphere again to reduce transition metal nanoparticles that may have been oxidized in the combustion reaction, and may be performed at a temperature of about 200 ° C. to about 500 ° C. If the third heat treatment temperature is less than 200 ℃, the reduction of the transition metal nanoparticles may be insufficient to reduce the catalytic activity, and if the third heat treatment temperature exceeds 500 ℃ there is a possibility that the particle size may grow excessively is not preferable.

The third heat treatment is preferably performed for 1 to 60 minutes. If the execution time of the third heat treatment is shorter than 1 minute, the reduction of transition metal nanoparticles may be insufficient, and the catalytic activity may be reduced. If the execution time of the third heat treatment is longer than 60 minutes, the effect of the heat treatment is saturated, which is uneconomical. .

The temperature of the first to third heat treatment is more preferably carried out at a temperature of 250 ℃ to 350 ℃, respectively.

The reducing atmosphere of the first heat treatment and / or the third heat treatment may be formed by, for example, adding a reducing gas to the inert gas so as to include 5% by volume to 30% by volume of the reducing gas. The reducing gas may be, for example, hydrogen, but is not limited thereto.

The oxidative atmosphere of the second heat treatment may be formed by, for example, adding an oxidizing gas to the inert gas so as to include 5% by volume to 30% by volume of the oxidizing gas. The oxidizing gas may be, for example, oxygen, but is not limited thereto.

The inert gas may be, for example, a gas such as nitrogen (N ₂ ), helium (He), neon (Ne), argon (Ar), but is not limited thereto.

The first to third heat treatments may be performed using an apparatus having a closed heating space, such as an oven, for example, and is not particularly limited. Preferably, it is preferable to continuously supply the reducing gas or the oxidizing gas and to continuously discharge the gas in the heat treatment space so that the reducing atmosphere or the oxidizing atmosphere can be kept constant.

Optionally, the step of removing excess reducing agent and surfactant prior to the first to third heat treatment may be further performed. To remove the reducing agent, for example, it may be washed with acetone, and to remove the surfactant, for example, it may be washed with an alcoholic solvent such as ethanol. However, the method of removing the reducing agent and / or the surfactant is not limited only to these methods.

A fourth aspect of the invention provides a cathode comprising a catalyst layer and a diffusion layer; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst of the present invention. do. The method of forming the catalyst layer from the supported catalyst of the present invention and the addition of the diffusion layer to form the membrane electrode assembly may be by conventional methods known in various documents, and detailed description thereof will be omitted herein.

A fifth aspect of the invention provides a cathode comprising a catalyst layer and a diffusion layer; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst according to the present invention. . In the production of such a fuel cell, since a conventional method known in various documents can be used, detailed description thereof is omitted here.

Hereinafter, the structure and effects of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention and are not intended to limit the scope of the present invention.

<Example 1>

Dark brown mixture by adding 359.2 mg of PtCl ₂ , 280.1 mg of RuCl ₃ , and 100 mg of activated carbon (Vulcan XC-72, Cabot) to a flask with 100 ml of THF in a nitrogen-glove box and stirring for 2 hours to fully disperse Got. To this was slowly added dropwise 4.0 g of tetraoctylammonium hydrotriethylborate, which can also serve as a reducing agent and a surfactant, to obtain a black dispersion.

The dispersion was reacted for 12 hours while maintaining the temperature between 30 ° C and 50 ° C.

Sufficient acetone was added to the flask to remove excess reducing agent and stirred for 1 hour. THF in the flask was removed and ethanol was added and stirred for 2 hours. Then, the resultant was filtered using a filtration device to remove the remaining organics using a sufficient amount of ethanol.

The filtrate was placed in a tube furnace and subjected to a first heat treatment for 10 minutes in a 300 ° C. hydrogen atmosphere, followed by a second heat treatment for 10 minutes in a 300 ° C. oxygen atmosphere. Thereafter, the resultant was further subjected to third heat treatment for 10 minutes in a 300 ° C. hydrogen atmosphere.

As a result, a supported catalyst having 80 wt% PtRu / C transition metal nanoparticles supported on a carrier was obtained.

<Example 2>

The supported catalyst was obtained in the same manner as in Example 1, except that the first to third heat treatments were performed at 200 ° C., respectively.

<Example 3>

The supported catalyst was obtained in the same manner as in Example 1, except that the first to third heat treatments were performed at 100 ° C., respectively.

XRD analysis results of the supported catalysts prepared in Examples 1 to 3 are shown in FIG. 1. Particle diameters of the supported catalysts prepared by using the results of FIG. 1 and the Scherrer equation were measured. The results are summarized in Table 1 below.

TABLE 1

Example 1 Example 2 Example 3 Heat treatment temperature 300 ℃ 200 ℃ 100 ℃ Lattice constant 3.872 Å 3.873 Å 3.874 Å Particle diameter (nm) 2.9 2.7 2.5

As shown in Table 1, it can be seen that the size of the transition metal nanoparticles has a size between 2 nm and 3 nm. This is a desirable particle size distribution that can maximize the active surface area while maintaining the activity as a catalyst.

<Example 4>

A dark brown mixture was obtained by adding 359.2 mg of PtCl ₂ , 280.1 mg of RuCl ₃ , and 100 mg of multiwalled carbon nanotubes (MWNT) to a flask with 100 ml of THF in a nitrogen-glove box and stirring for 2 hours to disperse sufficiently. . To this was slowly added dropwise 4.0 g of tetraoctylammonium hydrotriethylborate, which can also serve as a reducing agent and a surfactant, to obtain a black dispersion.

Subsequent processes were carried out in the same manner as in Example 1 to obtain an 80 wt% PtRu / C supported catalyst.

The PtRu / C supported catalyst was photographed using a transmission electron microscope and shown in FIG. 2. In addition, XRD analysis was performed on the PtRu / C supported catalyst and the results are shown in FIG. 3. The particle size was calculated using the XRD results and the Scherler equation. The particle size was found to be about 3 nm.

Example 5

In a nitrogen-glove box, 504.5 mg of PtCl ₂ , 74.3 mg of CoCl ₂ · 6H ₂ O, 83.2 mg of CrCl ₃ · 6H ₂ O, and 100 mg of multilayer wall carbon nanotubes (MWNT) were placed in a flask with 100 ml of THF. A dark brown mixture was obtained by stirring for hours to disperse sufficiently. To this was slowly added dropwise 3.2 g of tetraoctylammonium hydrotriethylborate, which can serve as a reducing agent and a surfactant, to obtain a black dispersion.

Subsequent processes were carried out in the same manner as in Example 1 to obtain an 80 wt% PtCoCr / C supported catalyst.

The PtCoCr / C supported catalyst was photographed using a transmission electron microscope and shown in FIGS. 4A and 4B. In addition, XRD analysis was performed on the PtCoCr / C supported catalyst and the results are shown in FIG. 5. The particle size was calculated using the XRD results and the Scherler equation. The particle size was found to be about 3.4 nm.

Comparative Example 1

80 wt% PtRu / C was prepared in the same manner as in Example 1, except that the first heat treatment was not performed.

Comparative Example 2

80 wt% PtRu / C was prepared in the same manner as in Comparative Example 1 except that the second and third heat treatments were performed at 200 ° C.

Comparative Example 3

80 wt% PtRu / C was prepared in the same manner as in Comparative Example 1, except that the second and third heat treatments were performed at 100 ° C.

XRD analysis results of the supported catalysts prepared in Comparative Examples 1 to 3 are shown in FIG. 6. The particle diameters of the supported catalysts prepared using the results of FIG. The results are summarized in Table 2 below.

TABLE 2

Comparative Example 1 Comparative Example 2 Comparative Example 3 Heat treatment temperature 300 ℃ 200 ℃ 100 ℃ Lattice constant 3.861 Å 3.861 Å 3.860 Å Particle diameter (nm) 11.4 9.5 4.8

As shown in Table 2 above, when the heat treatment temperature is low, the particle diameter is relatively good as 4.8 nm, but when the heat treatment temperature is 300 ° C., the particle diameter becomes excessively large as 11.4 nm. Considering that the heat treatment temperature is preferably about 300 ° C. for the removal of organic substances such as surfactants and the sufficient reduction of the transition metal particles, the active surface area is significantly reduced compared to Examples 1 to 3 in Table 1. Can be.

<Example 6>

A 60 wt% PtRu / C catalyst was prepared in the same manner as in Example 1, except that 269.4 mg of PtCl _{2 and} 210.1 mg of RuCl ₃ were used.

<Example 7>

An unsupported transition metal black catalyst was prepared in the same manner as in Example 1, except that the carbon nanotubes used as the carbon-based carrier were removed in Example 1.

Each catalyst prepared in Examples 1, 6 and 7 was photographed using a transmission electron microscope and shown in FIGS. 7A to 7C, respectively. As shown in Figure 7a and 7b it can be seen that the transition metal nanoparticles are evenly distributed on the multi-walled carbon nanotubes. In addition, as shown in FIG. 7C, it can be observed that the unsupported transition metal black catalyst particles are formed to an appropriate size.

In addition, XRD analysis was performed on these and the results are shown in FIG. 8. The results calculated using the XRD results and the Scherrer equation are summarized in Table 3 below.

TABLE 3

Example 1 Example 6 Example 7 Support State 80 wt% PtRu / C 60 wt% PtRu / C PtRu black Heat treatment temperature 300 ℃ 300 ℃ 300 ℃ Lattice constant 3.872 Å 3.863 Å 3.867 Å Particle diameter (nm) 2.9 2.5 2.7

As shown in Table 3, it was confirmed that the particle diameters of Examples 1, 6, and 7 were appropriately formed in appropriate sizes without excessive growth.

Although described in detail with respect to preferred embodiments of the present invention as described above, those of ordinary skill in the art, without departing from the spirit and scope of the invention as defined in the appended claims Various modifications may be made to the invention. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

According to the method for preparing a supported catalyst for a fuel cell of the present invention, a supported catalyst and a transition metal black catalyst having a high content of a metal catalyst component and a small particle size and easily supported on carbon nanotubes to have a high active surface area It can be manufactured easily.

Claims (22)

A transition metal nanoparticle comprising a carbon carrier and a transition metal nanoparticle supported on the carbon carrier, the average particle diameter of the transition metal nanoparticle being 1 to 5 nm, and the transition metal to the total weight of the carbon carrier and the transition metal nanoparticle. A supported catalyst having a nanoparticle weight of 60% by weight or more and a specific surface area of 10 m ² / g to 1000 m ² / g. The supported catalyst according to claim 1, wherein the weight of the transition metal nanoparticles to the total weight of the carbonaceous carrier and the transition metal nanoparticles is 75% by weight or more. The supported catalyst according to claim 1, wherein the carbonaceous carrier is carbon nanotube, carbon nanowire, carbon nanofiber, carbon nanohorn, carbon nanoring, activated carbon, acetylene black, graphite or a mixture thereof. The supported catalyst according to claim 1, wherein the average particle diameter of the transition metal nanoparticles is 2 to 4 nm. The method of claim 1, wherein the transition metal nanoparticles are platinum (Pt), ruthenium (Ru), osmium (Os), cobalt (Co), palladium (Pd), gallium (Ga), titanium (Ti), vanadium (V). ), Chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al) or an alloy thereof. Dispersing the transition metal precursor, the carbonaceous carrier, the surfactant, and the reducing agent in a solvent to prepare a uniform dispersion; Reacting the dispersion; First heat treating the reaction product in a reducing atmosphere; Performing a second heat treatment of the first heat treatment product in an oxidizing atmosphere; And And a third heat treatment of the second heat treatment product in a reducing atmosphere. According to claim 6, wherein the dispersion is 1 part by weight to 70 parts by weight of carbon-based carrier, 100 parts by weight to 400 parts by weight of surfactant, 100 parts by weight to 400 parts by weight with respect to 100 parts by weight of the transition metal precursor of the transition metal precursor And 100 parts by weight to 5000 parts by weight of a solvent, which is prepared by mixing uniformly. The method of claim 6, wherein the first heat treatment, the second heat treatment, or the third heat treatment is performed at a temperature of 200 ° C to 500 ° C. The method of claim 6, wherein the first heat treatment, the second heat treatment, or the third heat treatment is performed at a temperature of 250 ° C to 350 ° C. The supported catalyst according to claim 6, wherein the carbonaceous carrier is carbon nanotube, carbon nanowire, carbon nanofiber, carbon nanohorn, carbon nanoring, activated carbon, acetylene black, graphite, or a mixture thereof. Manufacturing method. The method of claim 6, wherein the transition metal precursor is a carbide, oxide, chloride, nitride, sulfide, sulfate, or nitrate of the transition metal, the transition metal is platinum (Pt), ruthenium (Ru), osmium (Os) ), Cobalt (Co), palladium (Pd), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu) ), Zinc (Zn), aluminum (Al) or an alloy thereof. 7. The process for producing a supported catalyst according to claim 6, wherein the surfactant is tetraoctylammonium hydrotriethylborate. 7. The method of claim 6, wherein the first to third heat treatments are performed for 1 to 60 minutes, respectively. Dispersing the transition metal precursor, the surfactant and the reducing agent in a solvent to produce a uniform dispersion; Reacting the dispersion; First heat treating the reaction product in a reducing atmosphere; Performing a second heat treatment of the first heat treatment product in an oxidizing atmosphere; And And a third heat treatment of the second heat treatment product in a reducing atmosphere. 15. The method according to claim 14, wherein the dispersion is 100 parts by weight to 400 parts by weight of surfactant, 100 parts by weight to 400 parts by weight of reducing agent and 100 parts by weight to 5000 parts by weight of solvent with respect to 100 parts by weight of transition metal of the transition metal precursor. Method for producing a transition metal black catalyst, characterized in that to be prepared by mixing. 15. The method of claim 14, wherein the first heat treatment, the second heat treatment, or the third heat treatment is performed at a temperature of 200 ° C to 500 ° C. The method of claim 14, wherein the first heat treatment, the second heat treatment, or the third heat treatment is performed at a temperature of 250 ° C. to 350 ° C. 15. The method of claim 14, wherein the transition metal precursor is a carbide, oxide, chloride, nitride, sulfide, sulfate, or nitrate of the transition metal, the transition metal is platinum (Pt), ruthenium (Ru), osmium (Os) ), Cobalt (Co), palladium (Pd), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu) ), Zinc (Zn), aluminum (Al) or an alloy thereof. 15. The method of claim 14, wherein the surfactant is tetraoctylammonium hydrotriethylborate. 15. The method of claim 14, wherein the first to third heat treatments are performed for 1 to 60 minutes, respectively. A cathode comprising a catalyst layer and a diffusion layer; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst according to claims 1 to 5. Membrane electrode assembly. A cathode comprising a catalyst layer and a diffusion layer; An anode comprising a catalyst layer and a diffusion layer; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the catalyst layer of the cathode and the catalyst layer of the anode comprises a supported catalyst according to claims 1 to 5. Fuel cell.

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