KR101013600B1 - Colloidal-Imprinted carbon structure, Preparing method thereof and ?? carbon supported catalysts for electrodes of fuel cell using thereof - Google Patents

Abstract

The present invention relates to a colloidal-imprinted (CI) carbon structure, a method for preparing the same, and a CI carbon supported catalyst for fuel cell electrodes including the same, in more detail, the CI carbon of the present invention. The structure is a porous carbon having a mesopores of uniform size and a nanoporous structure in which three pores are connected to each other in three dimensions, and may be manufactured through a colloidal-imprinting method. Since the CI carbon structure of the present invention not only has a large surface area and a large pore volume, but also has a high electrical conductivity, it uses a smaller amount of carbon black than the carbon black used as a carrier (support) of the conventional catalyst for fuel cell electrodes. Production of a catalyst for battery electrodes is possible. The CI carbon supported catalyst for fuel cell electrodes prepared using the CI carbon structure of the present invention is a catalytic activity for oxidation or reduction of these fuels in a fuel cell fueled by hydrogen, alcohol, and formic acid. Can be significantly increased than existing catalysts.

Colloidal-imprinting, carbon structure, fuel electrode, oxygen electrode

Description

Colloidal-Imprinted carbon structure, Preparing method etc. and CI carbon supported catalysts for electrodes of fuel cell using Young}

The present invention is a colloidal-imprited, having a uniform size of mesopores prepared by a colloidal-imprinting method and a nanoporous structure in which each pore is connected in three dimensions. CI) relates to a carbon structure. The present invention also relates to a CI carbon supported catalyst for fuel cell electrodes in which a transition metal is supported on the CI carbon structure.

Unlike ordinary batteries, fuel cells do not need to be replaced or recharged. Instead, a fuel cell is a device that converts chemical energy into electrical energy through an electrochemical reaction by supplying fuel such as hydrogen or methanol. The advantages of fuel cells are high efficiency (approximately 60% energy conversion efficiency), the use of various fuels as a pollution-free energy source, and the advantages of low land area and short construction period. Various applications are possible, from decentralized power generation available for power, home and power businesses. Especially, the potential market size is expected to be enormous when the operation of fuel cell vehicles, which is the next generation transportation device, is used in various ways. In particular, hydrogen fuel proton exchange membrane (PEM) fuel cells have attracted attention as energy sources for automobiles and transportation that require greater power.

The principle of the PEM fuel cell is as follows. The fuel cell includes a fuel electrode (oxide electrode), an oxygen electrode (reduction electrode), and a proton exchange membrane that physically separates them. Hydrogen is supplied to the fuel electrode and oxygen is supplied to the oxygen electrode. When a wire is connected to each of the fuel electrode and the oxygen electrode (for example, by connecting an external power consumption circuit), the circuit starts operation.

In the fuel electrode, the supplied hydrogen is decomposed into protons and electrons as shown in Formula 1, and the protons are easily transferred from the fuel electrode to the oxygen electrode through the membrane, whereas the polymer electrolyte membrane, which is an electrical insulator, is transferred from the anode to the oxygen electrode through the membrane. Block it from becoming

H ₂ → 2H ^{+ +} 2e ^-

Accordingly, in the oxygen electrode, the supplied oxygen is reduced as shown in the following formula (2).

_{^{O 2 + 4H + + 4e -}} → 2H 2 O

Therefore, when the operation of the fuel cell is combined, the hydrogen supplied to the anode as the cathode combines with the oxygen supplied to the oxygen as the anode to generate water and electrical energy. In order to improve the function and efficiency of the PEM fuel cell, it is important to use a highly active catalyst material, but it is also very important to improve the characteristics of the electrode. That is, it is also important to improve the conductivity of hydrogen and oxygen gas and the product H ₂ O used in the electrode reaction in the electrode, and to increase the conductivity of hydrogen ions and electrons generated by the electrode reaction. On the other hand, the catalyst is usually used to be supported on a porous carrier, and generally carbon having a nano-sized pore structure is used as a carrier. Accordingly, the electrode has a porous structure in which a catalyst-supported carbon carrier and a polymer electrolyte are combined, and in order to optimize the size and dispersion of the catalyst nanoparticles, it is preferable to use a carrier having a large pore volume and a large pore volume. The carbon carrier is an electron conduction channel and the polymer electrolyte is a hydrogen ion conduction channel. Therefore, the carrier should also be excellent in electrical conductivity, and its manufacturing process should be easy and the manufacturing cost should be low.

Porous pores of the electrode play an important role as supply and discharge channels for oxygen gas, hydrogen gas and water. Therefore, the improvement of the microstructure and manufacturing method of the electrode, the amount of the polymer electrolyte in the electrode is an important factor for improving the characteristics. With regard to the microstructure of the electrode described above, the catalytic activity is greatly changed because the size, stability, and dispersion state of the catalyst nanoparticles supported depend on the properties and the microstructure of the carbon carrier. In addition, depending on the structure of the carbon carrier, the electrode carrier, such as pore distribution, connectivity, surface area, and surface properties, reaction and product movement and discharge, hydrogen ions and electron conductivity change, and thus the characteristics of the fuel cell are greatly changed. Therefore, when the surface area and pore volume of the carbon carrier are large, the size of the supported metal catalyst particles is smaller and more uniformly distributed on the carbon carrier, thereby increasing the active area, and the diffusion of fuel and reaction products can easily occur, thereby improving the activity. have. However, when the size of the carbon carrier inner pores constituting the carbon carrier is large, the specific surface area of the carbon carrier decreases, so that the amount of catalyst material carried thereon decreases and the dispersion state decreases, thereby deteriorating fuel cell characteristics. When the pore size of the carbon material constituting the carbon carrier is extremely small, the specific surface area becomes very high, so that the amount of supported catalyst material is increased, but it is difficult to transfer and diffuse the reaction gas, and the polymer electrolyte can penetrate into the micropores. Since it is not possible, there is a tendency that the utilization efficiency of the catalyst is lowered and the fuel cell characteristics are not improved.

Therefore, optimizing the structure and shape of the carbon carrier is a method of maximizing the performance and efficiency of a fuel cell, particularly a proton electrolyte membrane (PEM) fuel cell.

However, until now, little research has been conducted on the correlation between the microstructure of the electrode carbon carrier for fuel cells and the characteristics of the fuel cell. For this reason, fuel cells using various carbon materials, including activated carbon, have been manufactured and their characteristics have been examined, but the optimum characteristics have not yet been obtained.

Electrocatalysts currently used for the oxidation and reduction of fuel and air in fuel cells have good electrical conductivity and carbon black having a relatively large surface area, for example about 230 m ² / g, for example Vulcan from Cabot It is prepared by dispersing a metal catalyst in the form of fine particles using XC-72 as a carrier. However, since the Vulcan XC-72 has a non-uniform pore size distribution, and especially contains a large number of micropores that the polymer electrolyte cannot reach well, the catalyst particles supported thereon do not form a three-phase interface and thus do not contribute to the electrochemical reaction. In addition, there was a problem of limiting the activity of the supported catalyst by preventing the diffusion of gas due to the low three-dimensional pore connectivity. For this reason, the development of a new high efficiency carrier is required, and there are several characteristics required for the catalyst for fuel cell electrodes in connection with the improvement of the activity of the fuel cell.

First, the metal catalyst particles must be small in size and uniformly distributed, and have a large surface area of the catalytic active site where oxidation / reduction reactions occur.

Second, the carbon used as a support must have a large surface area and a well-developed porous structure to facilitate the movement of gas and water, and the metal catalyst particles must be strongly supported so that the metal catalyst particles cannot be separated by physical and chemical impacts. do.

Third, the carbon used as a carrier should have high electrical conductivity and smooth the flow of electricity between the catalyst and the electrode to make the loss of power generated as small as possible to increase the efficiency of the battery.

Fourth, the carrier synthesis process should be simple and inexpensive.

Recently, research and interest in environmentally friendly energy and their commercialization in the high oil price environment are increasing more than ever in the world, and in particular, there is a demand for industrial methods to increase the efficiency of fuel cells.

Accordingly, the present inventors have devised a method for manufacturing a carbon structure by a colloidal-imprinting method as a result of trying to solve the above problems, and by supporting the transition metal in the colloidal-imprinted carbon structure thus prepared for various fuel cells As a result of preparing the electrode catalyst, in particular, it was found that the oxidation and reduction reactions of the electrode for fuel cells, fueled with hydrogen, alcohol and formic acid, were activated, thereby completing the present invention.

The present invention for solving the above problem relates to a colloidal-imprinted (CI) carbon structure,

It has a single or two types of pores selected from meso pores and macro pores of uniform size with an average diameter of 5 to 500 nm, and has a BET specific surface area of 100 to 1500 m 2 / g and a honeycomb structure. It is done.

In addition, the present invention relates to a method for producing the CI carbon structure,

A first step of uniformly mixing a mesophase pitch and colloidal inorganic metal oxide particles having an average diameter of 5 to 500 nm at a temperature of 45 to 100 ° C. to prepare a mixture;

A second step of preparing a meso-phase pitch-inorganic metal oxide particle composite by heating the mixture to 240 to 280 ° C. under an inert gas to imprint the colloidal inorganic metal oxide particles onto the mesophase pitch;

A third step of heating the composite to 850 to 2500 ° C. under an inert gas to obtain a graphite carbon composite;

And a fourth step of obtaining the CI carbon structure by removing the inorganic metal oxide particles by etching the graphite carbon composite material.

The present invention also relates to a CI carbon supported catalyst for fuel cell electrodes.

It characterized by including the CI carbon structure and the transition metal.

In addition, the present invention relates to a method for preparing the CI carbon supported catalyst for the fuel cell electrode,

A first step of preparing a mixed solution by mixing an aqueous solution of a slurry of water and a water-soluble transition metal salt of the CI carbon structure;

A second step of diluting and stirring distilled water into the mixed solution such that the concentration of the water-soluble metal salt is 1 mM to 5 mM;

A third step of preparing a reaction solution by adjusting the pH of the diluted mixed solution to 8-9;

A fourth step of preparing a catalyst by adding a reducing agent to the reaction solution to reduce the water-soluble metal salt to form metal particles, and then supporting the formed metal particles on the CI carbon structure; And

And a fifth step of separating the catalyst from the reaction solution.

The CI carbon structure of the present invention is simple to manufacture, has a wider BET specific surface area than commercial carbon black, and has very few fine micropores of 2 nm or less, so that the catalytic nanoparticles do not form a three-phase interface. Very few fail to contribute. In addition, since the CI carbon supported catalyst for fuel cell electrodes of the present invention has a very small size (2-4 nm) of metal particles uniformly dispersed in the CI carbon structure, the active area for catalytic reaction can be wide, and the electrical conductivity This is excellent because of this has the effect of increasing the catalytic activity for the oxidation and reduction of fuels such as hydrogen, alcohol and formic acid.

This invention will be described in detail below.

[CI Carbon Structure]

The present invention relates to a colloidal-imprinted (CI) carbon structure,

It has a single or two types of pores selected from meso pores and macro pores of uniform size with an average diameter of 5 to 500 nm, and has a BET specific surface area of 100 to 1500 m 2 / g and a honeycomb structure. It is done.

The CI carbon structure of the present invention has a structure in which a porous structure of an end type selected from among mesopores and macropores of uniform size or a mixture of two or more sizes is interconnected three-dimensionally. The size of the pore average diameter of the CI carbon structure is adjustable, the size of the pore depends on the size of the average diameter of the colloidal-organic metal oxide used in the manufacture. That is, when using colloidal-inorganic metal oxides having an average diameter of about 5 to 500 nm in size, the CI carbon structure has meso or macropores or mixed pores having an average diameter of 5 to 500 nm. Herein, if the average diameter of the CI carbon structure is less than 5 nm, the pore is too small, which may cause a problem of slowing the diffusion of reactants and products during the fuel cell reaction, and when it exceeds 500 nm, the specific surface area becomes small to increase the size of the catalyst particles. The problem may occur, and it is preferable to have a pore size within the above range. More preferably it is best to only have mesopores of the size of 5 to 50 nm. The CI carbon structure of the present invention can be confirmed by SEM and TEM photograph of FIG.

Referring to the method for producing the CI carbon structure having such a honeycomb structure in detail, the manufacturing method of the CI carbon structure of the present invention

A first step of uniformly mixing a mesophase pitch and colloidal inorganic metal oxide particles having an average diameter of 5 to 500 nm at a temperature of 45 to 100 ° C. to prepare a mixture;

Heating the mixture to 240 to 280 ° C. under an inert gas to imprint the colloidal inorganic metal oxide particles onto the mesophase pitch to produce a mesophase pitch-inorganic metal oxide particle composite;

A third step of heating the composite to 850 to 2500 ° C. under an inert gas to obtain a graphite carbon composite;

And a fourth step of obtaining the CI carbon structure by removing the inorganic metal oxide particles by etching the graphite carbon composite material.

In the first step, the colloidal inorganic metal oxide particles are not particularly limited, but any material that is not removed when a temperature of about 300 ° C. is applied, for example, inorganic metals such as copper, silver, gold, etc. may also be used. Although, preferably, an inorganic metal oxide such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , or the like, more preferably silica (SiO ₂ ) may be used. The colloidal inorganic metal oxide particles preferably have a uniform diameter of 5 to 500 nm, more preferably 5 to 50 nm in size. Since the average particle size of the colloidal inorganic metal oxide is the average particle size of the mesopores of the CI carbon structure of the present invention, by adjusting the size of the colloidal inorganic metal oxide used in the manufacturing, it is possible to control the mesopore size of the CI carbon structure Will be. In addition, by using a mixture of colloidal inorganic oxides of different sizes, it is also possible to synthesize a composite porous structure in which pores of different sizes are mixed. In addition, the colloidal inorganic metal oxide may be in the form of a sphere or a rod.

The mesophase pitch is a carbon precursor, which is stirred and mixed with the colloidal inorganic metal oxide particles to prepare a mixture. At this time, the mixing is made under a temperature of 45 ~ 100 ℃. In the mixing method, the inorganic metal oxide particles in the solid phase and the meso-phase pitch carbon precursor are finely ground by a physical method to make a uniform mixture, and then stirred until uniformly mixed in ethanol, and then all the ethanol is evaporated at 50 ° C. Stir.

In the first step, the mixture may mix the mesophase pitch and colloidal inorganic metal oxide particles in a weight ratio of 1: 1.5 to 3.0, wherein the mesophase pitch and colloidal inorganic metal oxide particles If the weight ratio of less than 1: 1.5, the formation of pores is small, there is a problem that the three-space connectivity is inferior, and when exceeding 1: 3.0 may cause the problem of excessive consumption of inorganic metal oxide, so used within the above range It is good.

The second step is imprinting the colloidal inorganic metal oxide particles in the meso phase pitch, and the mixture of the first step is heated at 240 to 280 ° C. for 2 to 3 hours to soften the meso phase pitch. Imprinting the colloidal inorganic metal oxide particles in the meso phase pitch by making the soft state near the point) and penetrating and distributing the colloidal inorganic metal oxide particles in and out of the mesophase pitch. It is to let.

In the third step, the graphite carbon composite may be obtained by carbonizing the mixture by high temperature heat treatment for 5 to 15 hours at a temperature of 850 ℃ to 2500 ℃ under an inert gas such as N ₂ or Ne, Ar, Kr and the like. At this time, a temperature increase rate shall be in the range of 1 degree-C / min-10 degree-C / min.

In the fourth step, the graphite carbon composite is etched with HF solution, NaOH solution or KOH solution to remove the inorganic metal oxide metal from the graphite carbon composite.

The manufacturing method of the CI carbon structure of the present invention

After filtering and washing the CI carbon structure of the fourth step, and drying the fifth step; may further include, the drying is preferably dried at about 70 ~ 80 ℃.

The CI carbon structure may be used as a carrier (support) of a catalyst for a fuel cell electrode by itself, and may be applied to various applications such as an adsorbent, separation and purification, hydrogen and drug storage, and an electrode.

Hereinafter, a catalyst for a fuel cell electrode using the CI carbon structure described above will be described.

[CI Carbon Supported Catalyst for Fuel Cell Electrode]

The present invention relates to a CI carbon supported catalyst for fuel cell electrodes, characterized in that it comprises the above-described CI carbon structure. More specifically, the CI carbon structure and the transition metal, characterized in that it comprises, the CI carbon structure in the catalyst of the present invention, serves as a carrier (support) of the transition metal, the average diameter as described above It has a single or two or more pore sizes selected from mesopores and macropores within the range of 5 ~ 500 nm, BET specific surface area of 100 ~ 1500 m 2 / g, characterized in that the honeycomb structure.

The transition metal is platinum (Pt), ruthenium (Ru), rhodium (Rh), molybdenum (Mo), osmium (Os), iridium (Ir), rhenium (Re), palladium (Pd), vanadium (V), Cobalt (Co) and Tungsten (W), Cerium (Ce), Iron (Fe), Selenium (Se), Nickel (Ni), Bismuth (Bi), Tin (Sn), Chromium (Cr) and Copper (Cu) A discontinuous metal selected from the group consisting of and the like or two or more alloy metals can be used. For example, monometals such as platinum or platinum-ruthenium (Pt-Ru) alloys, Pt-Ru-Rh alloys, Pt-Ru-Co-W alloys or Pt-Ru-Mo-W alloys, and other alloys may be used. have.

When explaining the CI carbon supported catalyst for fuel cell electrodes of the present invention by the composition ratio, it characterized in that it comprises 10 to 90% by weight of the CI carbon structure and 10 to 90% by weight of the transition metal.

Here, when the amount of the transition metal used is less than 10% by weight, there is a problem that sufficient electrode activity cannot be obtained, and when the amount of the transition metal exceeds 90% by weight, the amount of the CI carbon structure is relatively reduced, so that the catalyst particles are agglomerated and the size of the catalyst is increased, thereby increasing the catalyst efficiency. It is preferable to use a transition metal within this range since a problem of decreasing occurs.

In other words, the electrode catalyst for a fuel cell of the present invention can carry an amount corresponding to a maximum of 9 times the weight of the CI carbon structure as a carrier. This is because the CI carbon structure of the present invention, which is a carrier, has a larger surface area than that of a conventional carbon black carrier, and thus a relatively much larger amount of transition metal can be supported. The particles can be supported. In addition, since the transition metal of a very small size having an average diameter of 2 to 4 nm can be supported on the carrier, it is economically advantageous because expensive precious metals can be efficiently used. For example, in the conventional carbon black supported Pt-Ru catalyst for fuel cell electrodes, the carbon black carrier (E-TEK), which is a carrier, was used in an amount of about 40 to 60% by weight based on the total weight of the catalyst. The CI carbon-supported Pt-Ru catalyst for the fuel cell electrode of the present invention, which is loaded with a platinum-ruthenium alloy, has an electrode than the conventional catalyst even when the catalyst is manufactured using the amount of the CI carbon structure serving as a carrier using 20% or less of the total catalyst weight. Excellent activity

In general, in the preparation of the electrode catalyst, the smaller the supporting ratio of the catalyst metal to the carrier, the more the carrier must be used to support the same amount of the catalyst metal, so that the support used to obtain the same amount of the active catalyst The amount of is also increased. In this case, in manufacturing the electrode of the fuel cell, a large amount of catalyst had to be applied thickly to the carbon sheet or the carbon structure, and cracks were generated during drying or use of the applied catalyst, thereby degrading the performance of the fuel cell. There was a problem. However, the CI carbon supported catalyst for fuel cell electrodes of the present invention has a higher metal loading ratio than a catalyst using a conventional carbon black as a carrier, compared with the 20-60% loading ratio of commercially available E-TEK catalysts. Therefore, since the catalyst of the present invention may contain 80% or more of the amount of metal supported, the amount of carrier used to support the same amount of metal can be reduced to 1/2 or less, so that a small amount of catalyst is used as a whole so that the crack The phenomenon can be prevented. Of course, it is also possible to support the amount of the transition metal which is the catalyst metal to be 10% by weight of the total weight of the catalyst. In other words, the amount of transition metal used can be widely selected depending on the intended use. Furthermore, the CI carbon structure of the present invention has mesopores of uniform size in the range of 5 to 500 nm, preferably 5 to 50 nm in average pore size, excellent electrical conductivity, and three-dimensional The well-developed and interconnected structure frees the movement and diffusion of the fuel, allowing the fuel to reach the catalyst surface easily, so that the oxidation and reduction reactions can proceed quickly and the reaction products can be easily discharged. Have

In the CI carbon supported catalyst for fuel cell electrodes of the present invention, the electrode is characterized in that the anode or the cathode, the fuel cell is characterized in that the polymer electrolyte membrane fuel cell comprising a proton exchange membrane. In addition, the fuel of the fuel cell is hydrogen; Alcohols such as methanol and ethanol; And formic acid; The fuel cell using the selected fuel is characterized in that.

Hereinafter, a method for preparing a CI carbon supported catalyst for a fuel cell electrode of the present invention will be described in detail.

[Manufacturing Method of CI Carbon Supported Catalyst for Fuel Cell Electrode]

Method for producing a CI carbon supported catalyst for fuel cell electrodes of the present invention

A first step of preparing a mixed solution by mixing an aqueous solution of a slurry of water and a water-soluble transition metal salt of the CI carbon structure;

A second step of diluting and stirring distilled water into the mixed solution such that the concentration of the water-soluble transition metal salt is 1 mM to 5 mM;

A third step of preparing a reaction solution by adjusting the pH of the diluted mixed solution to 8-9;

A fourth step of preparing a catalyst by adding a reducing agent to the reaction solution to reduce the water-soluble transition metal salt to form metal particles, and then supporting the formed metal particles on the CI carbon structure; And

And a fifth step of separating the catalyst from the reaction solution.

A schematic diagram of the manufacturing method of the present invention is shown in FIG.

The method for preparing a catalyst for a fuel cell electrode according to the present invention is a relatively simple method, and the metal catalyst particles are reduced by a slow addition of a carbon dispersion solution and a reducing agent to a solution of the metal salt under stirring at a relatively simple method and a large surface area and It is uniformly dispersed in small size on the porous spherical carbon capsule carrier having pore volume. Metal catalyst particles of extremely fine size (2 to 3 nm) can be prepared.

In the first step, the CI carbon structure is the same as described above, wherein the water-soluble transition metal salt represents a salt form of the transition metal, and the water-soluble salt of the transition metal that catalyzes may be an acid salt or a basic salt. have. Examples of the water-soluble transition metal salt include H ₂ PtCl ₆ in the case of platinum, and RuCl ₃ in the case of ruthenium. The use amount of these transition metal salts can be determined stoichiometrically according to the amount of metal to be supported on the catalyst support. For example, when using a Pt-Ru alloy, the use ratio can also be determined by stoichiometric calculation. . The concentration of dissolving the water-soluble transition metal salt in water may also be determined according to the solubility in water according to the type of the salt. The step of preparing the aqueous solution may vary depending on the solubility and concentration of each transition metal salt used, the dissolution temperature and the like, but it is usually sufficient to stir for about 20 minutes to 1 hour. The CI carbon structure is used in the form of a slurry in water as a carrier. For example, a carrier is added to water at an appropriate amount of carbon carrier relative to 100 ml of water, and prepared by stirring. At this time, the carrier aggregate may be separated into individual particles, and sonication may be performed in the middle of stirring to degas the air in the pores of the carrier. The slurry in water is prepared in a separate vessel and mixed with the water-soluble transition metal salt in a reaction vessel.

In the second step, the molar concentration of the water-soluble transition metal salt is preferably 1 mM to 5 mM, preferably 1 mM to 3 mM, more preferably 1.5 mM to 2 mM, and the water-soluble transition metal salt solution It is calculated as the concentration of water soluble metal salts relative to the total water introduced by the water contained and the water contained in the slurry in water and other sources. The dilution of the concentration of the water-soluble transition metal salt is to prevent the transition metal particles from growing when the transition metal particles are agglomerated with each other when the transition metal particles are precipitated through a reduction reaction in the following step. That is, when the molar concentration of the water-soluble transition metal salt is greater than 5 mM, the metal particles may become large due to aggregation of the metal particles. When the water concentration is less than 1 mM, the concentration of the water-soluble transition metal salt is too low, making it difficult to deposit sufficient metal particles. Can occur

In the third step, the reason for adjusting the pH to 8 to 9 is to adjust the appropriate pH range in advance so that the smooth reduction reaction can proceed in the reduction reaction of the fourth step. At this time, the pH control may be used an acid or a basic aqueous solution such as NaOH, such as HCl or HNO ₃ commonly used, the present invention is not particularly limited thereto.

The fourth step is a step of reducing the transition metal in the form of water-soluble transition metal salt in the form of metal particles and supported on the carrier, the reducing agent is NaBH ₄ , LiBH ₄ , HCHO, HCOOH, CH ₃ OH, CH ₃ CH ₂ OH, One or two or more reducing agents selected from HCOONa, N ₂ H ₄ and AlBH ₄ may be used, and an excess is used relative to the number of moles of the water-soluble transition metal salt to be reduced. For example, an excessive amount of aqueous NaBH ₄ solution is used to produce H equivalent to 8 to 12 times, more preferably 10 times, the number of moles of the water-soluble transition metal salt. The transition metal particles have a size of 1 to 4 nm, more preferably 2 to 3 nm. In addition, it can be reduced by using a radiation such as gamma rays, microwaves, and the carbon-metal ion mixture can be reduced by blowing hydrogen gas at 200 ~ 300 ℃.

The fifth step is to precipitate the CI carbon supported catalyst prepared in the fourth step by allowing the reaction solution to stand still, and then separating the CI carbon supported catalyst from the reaction solution.

The preparation method of the present invention may further include a sixth step of repeatedly washing and drying the CI carbon supported catalyst separated from the reaction solution with water in a fifth step. The washing is a process for removing impurities such as chlorine contained in the water-soluble metal salt.

The above steps are carried out under an air atmosphere at room temperature and atmospheric pressure, unless otherwise specified, and the water used is preferably distilled water or deionized water.

The above-described CI carbon supported catalyst for the fuel cell electrode of the present invention and the catalyst prepared by the method of manufacturing the same may be used in a fuel cell, and may also be used in an anode or a cathode of a fuel cell. The CI carbon supported catalyst of the present invention is preferably used for another type of proton exchange membrane (or polymer electrolyte membrane) fuel cell including a hydrogen fuel cell. And the present invention is hydrogen; Alcohols such as methanol and ethanol; And formic acid; It can be used as a catalyst for electrodes of a fuel cell using any one selected from among the fuels.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited thereto.

Fabrication of CI Carbon Structure

Examples and Comparative Examples

CI carbon structure of the present invention was prepared as follows.

A mixture was prepared by uniformly mixing spherical silica (SiO ₂ ) particles (Ludox TM-40 colloidal sillca) having a mesophase pitch of 45 μm or less and an average diameter of about 22 nm in ethanol in a 1: 2 weight ratio. The mixture is then stirred at 50 ° C. under N ₂ gas atmosphere until all of the alcohol has evaporated. The mixture of all ethanol evaporated was heated for 3 hours at about 260 ° C., which is a softening point, to imprint colloidal silica particles to obtain a meso-phase pitch-inorganic metal oxide particle composite. The composite was heated at 900 ° C. for 12 hours in a N ₂ gas atmosphere to obtain a graphite carbon composite by carbonization, and then dissolved silica from the carbon composite using hydrofluoric acid (HF) solution to form IC carbon. The structure was prepared, and SEM and TEM images of the prepared CI carbon structure are shown in FIGS.

When synthesizing CI carbons with pores of different sizes from 5 to 500 nm other than the commercial Ludox colloidal particle sizes above, first synthesize silica particles of the desired size and process them in the same manner from above. CI carbon can be synthesized.

As a comparative example, a commercial Vulcan carbon XC-72 carbon black carbon structure (hereinafter referred to as "VC") manufactured by Carbot was used.

Experimental Example 1

Brunauer-Emmett-Teller (BET) specific surface area measurement experiment

Measurement of the BET specific surface area of the carbon structure of the embodiment was tested, the results are shown in Figure 3, the characteristics of the carbon structure of the Examples and Comparative Examples in Table 1 below. In Table 1 below, V _total represents the total pore volume per g, V _micro represents the micro pore volume per g, and σ represents the electrical conductivity.

Experimental Example 2

X-ray Diffraction Analysis Pattern Experiment

The X-ray diffraction analysis pattern experiment of the carbon structures of Examples and Comparative Examples was performed, and the results are shown in FIG. 4.

Looking at Figure 4, the CI carbon structure of the embodiment of the present invention was observed a strong and sharp peak at (002), a weak peak at (100) and (004). On the other hand, the commercial VC carbon structure of the comparative example showed a similar pattern to the CI carbon structure of the example in (002), (100) and (004), but showed a significant difference in the intensity of the (002) peak. (002) The peak is a measure of the degree of graphitization. It is shown that the CI carbon structures of the present invention are more graphitized than commercial VC carbon structures.

Preparation of CI Carbon Supported Catalyst for Fuel Cell Electrode

Preparation Example 1

2 × 10 ^-3 mol of H ₂ PtCl ₆ .6H ₂ O (reagent grade from Aldrich, 37.99% Pt) was dissolved in 1.8032g of deionized water was prepared 100㎖ the aqueous metal salt solution. 2.74 g of the CI carbon structure prepared in the above example was suspended in 100 ml of deionized water and stirred for 1 hour to form a uniform slurry in water. 100 ml of the slurry in water was added to 100 ml of the aqueous metal salt solution and stirred for about 30 minutes to prepare a mixed solution. 2.8 L of deionized water was added and diluted so that the total concentration of the water-soluble metal salt was about 2 mM in the mixed solution, followed by stirring for 1 hour. After adjusting the pH of the mixed solution to about 8 using a 3.0 M NaOH solution, 50 ml of excess NaBH ₄ solution (NaBH ₄ / metal molar ratio is approximately 10) was rapidly added into the carbon-metal salt mixed solution under vigorous stirring, The mixture was stirred at room temperature over 2 hours so that the metal particles were supported on the CI carbon structure. After allowing the catalyst to stand to separate the catalyst from the reaction solution, the upper solution was cleared, filtered using 0.2 μm nylon filter paper, washed several times with distilled water and dried at 80 ° C. to obtain Pt metal based on the total weight of the catalyst. A 20 wt% CI carbon supported catalyst for fuel cell electrodes was prepared. The TEM photograph of the prepared catalyst of the present invention is shown in a of FIG. 5.

Production Example 2

In the same manner as in Preparation Example 1, the metal salt solution was 0.9730 g of 2 × 10 ^-3 mol of H ₂ PtCl ₆ H ₂ O (Aldrich's reagent grade, 37.99% Pt) and 2 × 10 ^-3 mol of RuCl ₃ 0.194 g of .xH ₂ O (Aldrich's reagent grade 40.71% Ru) was dissolved in 100 mL of deionized water to prepare a metal salt solution of Pt-Ru alloy. In water slurry, 0.379 g of the CI carbon structure prepared in the above example was suspended in 100 ml of deionized water and stirred for 1 hour to form a uniform slurry in water. The fuel was loaded with 60 wt% Pt-Ru alloy. A CI carbon supported catalyst for battery electrodes was prepared, and a TEM photograph of the prepared catalyst is shown in FIG.

It can be seen that the spherical uniform black dots are uniformly distributed in FIGS. 5 and 6, which are TEM photographs of the CI carbon supported catalyst for fuel cell electrodes of the present invention prepared in Preparation Examples 1 and 2, and FIG. As shown in a of 5 and a of FIG. 6, it can be seen that the catalyst of the present invention has a size of 2 to 3.5 nm and is evenly dispersed.

Comparative Production Example 1 to Comparative Production Example 4

Pt / VC catalyst and Pt-Ru alloy having 20% by weight of Pt supported in the same manner as in Preparation Examples 1 and 2, using a commercially available Vulcan XC-72 carbon black (VC) manufactured by Cabot as a carbon carrier (support) This 60 wt% supported Pt-Ru / VC alloy catalyst (Pt: Ru = 1: 1 molar ratio), US E-TEK Co., Ltd. was prepared, and Comparative Preparation Example 1 and Comparative Preparation Example 2 were carried out, respectively. The TEM photograph of Example 1 is shown in b of FIG. 5 and the TEM photograph of Comparative Preparation Example 2 is shown in b of FIG. 6.

In Comparative Example 3 and Comparative Example 4, Pt / E-TEK catalyst having 20% by weight of Pt of commercially available US E-TEK and Pt-Ru / E having 60% by weight of Pt-Ru alloy were supported. A TEK alloy catalyst was used.

As can be seen in the comparative pictures of FIGS. 5 and 6, the catalyst using the CI carbon structure of the present invention has a smaller average particle size than the catalyst using the VC carbon structure, and is uniformly dispersed.

Experimental Example 3

X-ray diffraction analysis pattern experiment of catalyst

The results of the X-ray diffraction analysis pattern experiments of the catalysts of Preparation Example 1 and Comparative Preparation Example 1 are shown in A of FIG. 7, and the experimental results of the Catalysts of Preparation Example 2 and Comparative Example 2 are shown in FIG. Indicated.

Looking at Figure 7, it can be seen that there is no other ruthenium or ruthenium oxide phase and all have a pure face centered cubic structure of platinum.

Experimental Example 4

Catalytic Reaction Characteristic Experiment

The reaction characteristics of the catalysts prepared in Preparation Examples 1 to 2 and Comparative Preparation Examples 1 to 4 were confirmed through cyclic voltammetry (CV) and unit cell performance tests, and the results are illustrated in FIGS. 8 to 10. Shown in

(1) Cyclic Voltametry Measurement Experiment

FIG. 8A is a cyclic voltammogram of an experiment measured in the presence of sulfuric acid showing the electrochemical surface area of the catalysts of Preparation Example 1, Comparative Preparation Example 1 and Comparative Preparation Example 3, and FIG. It is a cyclic voltamogram measured in the presence of sulfuric acid showing the electrochemical surface area of the catalyst prepared in Preparation Example 2, Comparative Preparation Example 2 and Comparative Preparation Example 4. In view of this, compared to the catalysts of the comparative examples, the catalysts of the preparations include a wider hydrogen adsorption region, i.e., an electrochemically active surface region, in the hydrogen redox-related cyclobologram. This shows that Preparation CI carbon supported catalysts have a larger available electrochemically active surface area.

(2) Performance test on cathode

The unit cell performance test of the hydrogen fuel proton exchange membrane fuel cell which tested the platinum catalyst of manufacture example 1, the comparative manufacture example 1, and the comparative manufacture example 3 under oxygen conditions at 60 degreeC and 80 degreeC temperature was performed. The results are shown in A and B of FIG. 9, respectively, and the anode was used as a commercial catalyst (20 wt% Pt-Ru / E-TEK catalyst), and the cathode was prepared in Preparation Example 1, Comparative Preparation Example 1 and Each of the 20 wt% supported platinum catalysts of Comparative Preparation Example 3 was used. Single cell reaction conditions were performed on electrode cross-sectional area 6.25 cm <2>, 200 sccm hydrogen, and 1000 sccm oxygen conditions.

Referring to FIG. 9, it can be seen that the catalyst of Preparation Example 1 of the present invention has a higher current density at the same voltage for oxygen reduction than the catalysts of Comparative Preparation Example 1 and Comparative Preparation Example 3, and also has a higher power at the same current. Shows density. This shows that the catalyst of the present invention has excellent reaction activity for oxygen reduction.

(3) Performance test on anode

Of a direct formic acid fuel cell using formic acid as a test of the supported Pt-Ru catalysts of Preparation Example 2, Comparative Preparation Example 2 and Comparative Preparation Example 4 under oxygen conditions at 60 ° C and 80 ° C Unit cell performance experiments were conducted. The results are shown in A and B of FIG. 10, respectively. In the experiment, the anode was prepared by using 60 wt% Pt-Ru / E-TEK catalysts of Preparation Example 2, Comparative Preparation Example 2 and Comparative Preparation Example 4, respectively. The electrode used commercially available platinum black. Reaction conditions of the unit cell were carried out under an electrode cross-sectional area of 2.56 cm 2, 1.1 cc formic acid, and 1000 sccm oxygen.

Referring to FIG. 10, it can be seen that the catalyst of Preparation Example 2 of the present invention has a higher current density at the same voltage for oxidation of formic acid than the catalysts of Comparative Preparation Example 2 and Comparative Preparation Example 4, and also at the same current. It shows high power density. From this, it can be seen that the catalyst of the present invention has excellent reaction activity in formic acid oxidation reaction.

Experimental Example 5

Chronoamperogram Experiment

Experiments were carried out to measure the change of current density with respect to the time of the catalysts of the Preparation Example and Comparative Preparation Example under a constant voltage condition, and the chronoamperogram as a result of the experiment is shown in FIG. 11. FIG. 11A shows the results of a change in current density with respect to the time of a hydrogen fuel proton exchange membrane fuel cell unit cell reaction measured at 60 ° C. and 0.75 V using the catalysts of Preparation Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 3, respectively. FIG. 11B is an experimental result of the direct formic acid fuel cell unit cell reaction measured at 30 ° C. and 0.5V using the catalysts of Preparation Example 2, Comparative Preparation Example 2, and Comparative Preparation Example 4, respectively.

Referring to the chronoampogram of Figure 11, the platinum supported catalyst of Preparation Example 1 compared to the catalysts of Comparative Preparation Examples 1 and 3 for the oxygen reduction reaction (11a), the platinum-ruthenium alloy catalyst of Preparation Example 2 is Comparative Preparation Example Compared to the same alloy catalyst of 2 and 4, it showed higher initial and final current densities for formic acid oxidation reaction (11b), which showed the electrochemically active surface area results of FIG. 8 and the unit cell reaction results showing the power density of FIG. In addition, the slow decrease in current density during the measurement shows the excellent stability of the catalyst of the present invention.

From the above experimental results, it can be seen that the catalyst prepared using the CI carbon structure according to the present invention shows excellent activity against hydrogen, formic acid or alcohol oxidation and oxygen reduction.

1 is a schematic diagram of a method for producing a CI carbon structure according to the present invention.

In FIG. 2, A is a scanning electron microscope (SEM) photograph of the CI carbon structures prepared in Example, and B is a transmission electron microscope (TEM) photograph.

3 is a liquid nitrogen adsorption and desorption isotherm of the CI carbon structure prepared in Example.

Figure 4 is a graph showing the X-ray diffraction analysis pattern of the CI carbon structure of the example performed in Experimental Example 2 and the commercial VC (Vulcan carbon XC-72 carbon black carbon structure) of the comparative example.

5 is a TEM photograph of a 20 wt% Pt / CI catalyst prepared in Preparation Example 1 (average size 2 to 3.5 nm), and b is a 20 wt% Pt / VC catalyst prepared in Comparative Preparation Example 1 (average size) 4-5 nm) TEM image.

6 is a TEM photograph of a 60 wt% Pt-Ru / CI catalyst (average size 2 to 3.5 nm) prepared in Preparation Example 2, and b is 60 wt% Pt-Ru / VC prepared in Comparative Preparation Example 2 TEM image of catalyst (average size 4-5 nm).

7 is an X-ray diffraction pattern measurement test result of the catalyst carried out in Experimental Example 3, A is the catalyst of Preparation Example 1 and Comparative Preparation Example 1, B is the result of experimenting the catalyst of Preparation Example 2 and Comparative Preparation Example 2 It is a graph comparing.

8 is a cyclic voltametry experiment conducted in Experimental Example 4, where A is the catalyst of Preparation Example 1, Comparative Preparation Example 1 and Comparative Preparation Example 3, and B is Preparation Example 2, Comparative Preparation Example 2 and Comparative Preparation Example 4. Is a cyclic voltamogram showing the hydrogen adsorption capacity in the presence of sulfuric acid for the catalyst of.

FIG. 9 is a cell performance test of a hydrogen fuel proton exchange membrane fuel cell obtained by using different cathode catalysts performed in (2) of Experimental Example 4, where A is a unit cell test result at 60 ° C. and B is 80 ° C. FIG.

FIG. 10 is a cell performance test of a direct formic acid fuel cell obtained by using different anode catalysts in (3) of Experimental Example 4, where A is a unit cell test result at 60 ° C. and B is 80 ° C. FIG.

11 is a chronoamperogram showing the results of the experiment conducted in Experimental Example 5. FIG.

Claims (12)

delete A first step of uniformly mixing a weight ratio of mesophase pitch 1 at a temperature of 45 to 100 ° C. and 1.5 to 3.0 weight ratios of colloidal inorganic metal oxide particles having an average diameter of 5 to 500 nm; Heating the mixture to 240 to 280 ° C. under an inert gas to imprint the colloidal inorganic metal oxide particles on the mesophase pitch to produce a mesophase pitch-inorganic metal oxide particle composite; A third step of heating the composite to 850 to 2500 ° C. under an inert gas to obtain a graphite carbon composite; Etching the graphite carbon composite to remove the inorganic metal oxide particles to obtain a colloidal-impregnated carbon structure; a method of manufacturing a colloidal-impregnated carbon structure comprising the . The colloidal inorganic metal oxide according to claim 2, wherein the colloidal inorganic metal oxide is one or more selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), titanium dioxide (TiO ₂ ), and silica (SiO ₂ ). Method of manufacturing a printed carbon structure. delete A colloidal-impregnated carbon supported catalyst for a fuel cell electrode, comprising a colloidal-imprinted carbon structure prepared by the method of claim 2 and a transition metal. [Claim 6] The colloidal-impregnated carbon supported catalyst for fuel cell electrode according to claim 5, comprising 10 to 90 wt% of the colloidal-imprinted carbon structure and 10 to 90 wt% of the transition metal. . The method of claim 5, wherein the transition metal is platinum (Pt), ruthenium (Ru), rhodium (Rh), molybdenum (Mo), osmium (Os), iridium (Ir), rhenium (Re), palladium (Pd), Vanadium (V), cobalt (Co) and tungsten (W), Ce (cerium), iron (Fe), selenium (Se), nickel (Ni), bismuth (Bi), tin (Sn), chromium (Cr) And one or more selected from copper (Cu). A colloidal-impregnated carbon supported catalyst for fuel cell electrodes, characterized in that the fuel cell electrode. 8. The colloidal-impregnated carbon supported catalyst for fuel cell electrodes according to any one of claims 5 to 7, wherein the fuel cell electrode is an anode or a cathode. A fuel cell comprising the catalyst of any one of claims 5 to 7. A first step of preparing a mixed solution by mixing an aqueous solution of a water-soluble slurry and a water-soluble transition metal salt of the colloidal-imprinted carbon structure prepared by the method of claim 2; A second step of diluting and stirring distilled water into the mixed solution such that the concentration of the water-soluble transition metal salt is 1 mM to 5 mM; A third step of preparing a reaction solution by adjusting the pH of the diluted mixed solution to 8-9; A fourth step of preparing a catalyst by adding a reducing agent to the reaction solution to reduce the water-soluble metal salt to form metal particles, and then supporting the formed metal particles on the CI carbon structure; And And a fifth step of separating the catalyst from the reaction solution. The method of claim 1, further comprising a colloidal-impregnated carbon supported catalyst for a fuel cell electrode. The fuel according to claim 10, wherein the reducing agent is at least one selected from NaBH ₄ , LiBH ₄ , HCHO, HCOOH, CH ₃ OH, CH ₃ CH ₂ OH, HCOONa, N ₂ H ₄ and AlBH ₄ . A method for producing a colloidal-imprinted carbon supported catalyst for battery electrodes. 12. The method of claim 10, wherein the metal particles have an average size of 1 to 4 nm.

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