KR101808299B1 - Method of preparing porous non-Pt catalysts for a fuel cell - Google Patents

Abstract

The present invention relates to a method for producing a porous non-platinum catalyst for a fuel cell, and more particularly, to a method for manufacturing a porous non-platinum catalyst for a fuel cell, It is possible to improve the performance of the fuel cell by improving the specific surface area of the catalyst.

Description

[0001] The present invention relates to a porous non-Pt catalyst for a fuel cell,

The present invention relates to a method for producing a porous non-platinum catalyst capable of improving the performance and durability of a fuel cell.

Fuel cells, which are attracting attention as a new energy source in place of fossil fuels, are a kind of power generation system that converts chemical energy generated by reduction and oxidation of fuel (oxygen and hydrogen) directly into electric energy. It is particularly important to increase the reaction rate in the case of a polymer electrolyte fuel cell, which is a fuel cell system driven at a low temperature, in which an oxidation reaction of hydrogen occurs at the anode of the fuel cell and a reduction reaction of oxygen occurs at the cathode.

Currently, the catalyst used in the fuel cell system is a platinum (Pt) catalyst which is a noble metal catalyst. Although the platinum catalyst exhibits excellent performance in the fuel cell, it is a major obstacle to the commercialization of the fuel cell in terms of the price and the reserve amount.

Therefore, various attempts have been made to reduce the amount of platinum used to overcome the limitation of the platinum catalyst. However, the most ideal direction is to develop and use a non-platinum-based non-whiteness catalyst. In particular, non-whiteness catalysts based on transition metals (non-noble metal catalysts) have been actively studied.

On the other hand, it is very important that the catalyst of the fuel cell has a macro pore and a high specific surface area in order to exhibit high performance in a unit cell and a high current density region in a half cell and have excellent durability.

When macro pores are present, the diffusion of the fuel of the fuel cell supplied in the form of gas phase occurs well and the reaction becomes active. In addition, the flow of water as reaction product proceeds smoothly, thereby improving performance and durability So that the life of the battery can be prolonged.

However, if the catalyst of the fuel cell has only macro pores, the specific surface area decreases, and the number of active sites decreases, so that the performance of the fuel cell deteriorates.

In order to overcome the problem of macro pores, meso pores having a smaller diameter than those of macro pores may be formed together to improve the specific surface area of the catalyst.

Therefore, development of a technology capable of controlling the pore size and production amount so as to ensure a specific surface area capable of improving the performance of the fuel cell and maintain the excellent performance for a long time by allowing the reaction to proceed smoothly at the fuel cell electrode Is required.

Korean Patent Publication No. 10-2012-0098354 Korean Patent No. 10-1305439 Korean Patent No. 10-1347789 Korean Patent No. 10-1216052 Korean Patent No. 10-1420653

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of manufacturing a porous non-platinum catalyst for a fuel cell capable of controlling the size and amount of pores in the process of producing a porous non-platinum catalyst.

(A) mixing and polymerizing (A) a transition metal precursor, (a2) silica beads and (a3) nitrogen-containing monomers to obtain a silica bead-containing polymer; (B) heat treating the silica bead containing polymer; And (C) reacting the heat-treated silica bead-containing polymer with an alkali solution to remove the silica beads. The present invention also relates to a method for producing a porous non-platinum catalyst for a fuel cell.

According to the present invention, the size and porosity of the pores formed in the catalyst can be controlled by using silica beads in the process of manufacturing the porous non-platinum catalyst for fuel cells.

Since the porous non-platinum catalyst for fuel cells includes macropores, the fuel supplied to the fuel cell in the gas phase can be diffused well to improve the reactivity, and the flow of water, which is the reaction product of the oxygen reduction electrode, Thereby improving performance and durability.

In addition, the porous non-platinum catalyst for fuel cells has a specific surface area due to mesopores smaller than macropores, thereby increasing the number of active sites and improving the performance of the fuel cell.

1 is a schematic view showing a method for producing a porous non-platinum catalyst for a fuel cell according to the present invention.
2 is an SEM photograph of the porous non-platinum catalyst particles prepared in Example 1. Fig.
3 is a TEM photograph (a) to (c) of the porous non-platinum catalyst particles prepared in Example 1 and an energy-dispersive X-ray spectroscopy (EDS) analysis result (d).
FIG. 4 is a nitrogen adsorption / desorption curve for the porous non-platinum catalyst prepared in Example 1. FIG.
5 is a graph showing initial performances of ORR polarization for a half cell to which the catalysts of Example 1 and Comparative Examples 1 to 3, respectively, are applied.
6 is a graph showing initial performances of ORP polarization for a half-cell to which the porous non-platinum catalyst of Example 1 and the commercial platinum catalyst of Comparative Example 4 are respectively applied.
FIG. 7 is a graph showing currents measured with a constant voltage over a half-cell to which a porous non-platinum catalyst and a conventional platinum catalyst of Comparative Example 4 are respectively applied in Example 1; FIG.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 is a schematic view showing a method for producing a porous non-platinum catalyst for a fuel cell according to the present invention.

Referring to Figure 1, one aspect of the present invention is directed to a method of making a thin film transistor comprising: (A) (a1) a transition metal precursor; (a2) silica beads; And (a3) a nitrogen-containing monomer are mixed and polymerized to obtain a silica bead-containing polymer; (B) heat treating the silica bead containing polymer; And (C) reacting the heat-treated silica bead-containing polymer with an alkali solution to remove the silica beads. The present invention also relates to a method for producing a porous non-platinum catalyst for a fuel cell.

In the step (A), a silica bead-containing polymer may be obtained by mixing (a1) a transition metal precursor, (a2) silica bead and (a3) nitrogen-

The silica bead-containing polymer may include a plurality of silica beads in a spherical particle made of the polymer, or may have a form bonded to a surface.

According to one embodiment, the molar ratio of the (a1) transition metal precursor, (a2) silica bead colloid, and (a3) nitrogen containing monomer may be 1-10: 2-10: 1.

If the molar ratio of the (a1) transition metal precursor to the nitrogen-containing monomer (a3) is less than 1, pores can not be formed sufficiently to improve the performance and durability of the fuel cell. If the mole ratio is more than 10, So that the catalyst may not be able to be produced.

If the molar ratio of the (a2) silica bead colloid to the nitrogen-containing monomer (a3) is less than 2, pores can not be formed sufficiently to improve the performance and durability of the fuel cell, and if it is more than 10, So that the catalyst may not be able to be produced.

According to another embodiment, the transition metal is selected from the group consisting of Fe, Co, Ti, V, Mn, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, It may be at least one selected.

According to another embodiment, the transition metal precursor (a1) may be at least one selected from a chloride, an oxide, a hydroxide, a nitrate, a sulfate, an acetate, an acetylacetonate and a formate of the transition metal.

According to another embodiment, (a2) the silica beads may have a particle diameter of 1-100 nm.

Since the size of the pores formed in the porous non-platinum catalyst can be determined by the particle size of the silica beads, silica beads having an appropriate size can be selected in consideration of characteristics such as performance and durability of the porous non-platinum catalyst.

The pores formed in the porous non-platinum catalyst may be divided into mesopores having a diameter of 2 nm or more and 50 nm or less and macro pores having a diameter of 50 nm or more and 100 nm or less. The mesopore can increase the specific surface area of the catalyst to improve the performance of the catalyst. The macropore can facilitate the supply of reactants and discharge of the reaction occurring in the fuel cell electrode, thereby improving the durability of the battery.

Therefore, considering the performance and durability, it is possible to determine the ratio of the mesopores and macropores formed in the porous non-platinum catalyst, and accordingly, the silica beads having a particle size capable of forming mesopores and the macropores The silica beads having a particle size of 1 nm or less can be selected to produce a porous non-platinum catalyst.

According to another embodiment, (a3) the nitrogen-containing monomer may be at least one selected from aniline, pyrrole, and acrylamide, but monomers containing nitrogen can be widely used.

According to another embodiment, the polymer may be at least one nitrogen-containing polymer selected from polyaniline, polypyrrole and polyamide.

In the step (B), the silica bead-containing polymer may be heat-treated.

According to one embodiment, the heat treatment may include a first heat treatment step of heating at 100-300 占 폚 for 30 minutes to 2 hours; And a second heat treatment step of heating at 400-1000 DEG C for 1-5 hours.

In the first heat treatment step, the organic matters remaining in the silica bead-containing polymer can be removed. In the second heat treatment step, the silica bead-containing polymer is carbonized to form transition metals, nitrogen (N), and carbon By forming a carbide, a stabilized catalyst can be produced.

In order to carbonize the silica bead-containing polymer, if only one heat treatment is performed according to the conditions of the second heat treatment process, the remaining organic matters are abundant, so that the carbonization efficiency of the silica bead-containing polymer is lowered, Can be remarkably lowered.

It is necessary to satisfy both of the heat treatment temperature and the time condition according to the first heat treatment step and the second heat treatment step to remove the organic matter and form the stabilized carbide. In other words, if either of the temperature and time conditions of the first heat treatment and the second heat treatment is not satisfied, the organic matter can not completely be removed and carbide formation is also impossible.

The primary and secondary heat treatments may be performed under an inert atmosphere formed by an inert gas selected from argon, nitrogen, neon, krypton, xenon and radon to improve the heat treatment efficiency.

In the step (C), the silica beads may be removed from the silica bead-containing polymer by reacting the heat-treated silica bead-containing polymer with an alkali solution.

According to one embodiment, the alkali solution may be at least one selected from an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide.

When the alkali solution is heated to 90-110 deg. C, the silica bead removal efficiency can be further improved.

The porous non-platinum catalyst for a fuel cell manufactured according to the above-described production method may include a carbide in which a transition metal and nitrogen (N) are supported on carbon (C), and may be in the form of particles having pores having various particle diameters have.

The pores may have a particle diameter of 2-100 nm, macro pores having mesopores of 50 nm or more and 50 nm or less and having diameters of 2 nm or more and 50 nm or less and 100 nm or less, Can be.

For example, when the ratio of the mesopores is high, the specific surface area of the catalyst is increased to increase the active sites, thereby improving the catalytic performance. When the ratio of the macropores is high, the reactant supply and product discharge It is possible to improve the durability of the battery.

In addition, the porous non-platinum catalyst for a fuel cell may be a catalyst for an oxygen reduction electrode of a fuel cell.

Oxygen is supplied to the oxygen reduction electrode and oxygen can be smoothly supplied due to pores formed in the porous non-platinum catalyst.

In addition, water is generated as a reaction product in the oxygen reduction electrode, and the flow of water smoothly proceeds through the pores formed in the porous non-platinum catalyst, so that the durability of the fuel cell can be improved.

Since the porous non-platinum catalyst for fuel cells has a large specific surface area, the number of active sites is increased and thus the reactivity is improved, so that the oxygen reduction reaction of the oxygen reduction electrode can be promoted.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. In addition, it is apparent that, based on the teachings of the present invention including the following examples, those skilled in the art can easily carry out the present invention in which experimental results are not specifically shown.

material

In the following examples and comparative examples, reagent grade ferric chloride hexyhydrate (FeCl ₃ .6H ₂ O, 99%), ammonium persulphate (APS, 98%), aniline (99.5%) purchased from Sigma- , Formaldehyde solution and silica bead colloid (Lodox-HS-40 colloidal silica) were used.

Example 1

(A) Step: Polymerization of aniline centered on silica beads

To 100 ml of a 1 M solution of formaldehyde was added 32.4 g of FeCl ₃ .6H ₂ O and connected to a chiller cooler with continuous stirring and cooled to 2 ° C. At this time, the temperature was maintained at the temperature for 30 minutes so that a temperature gradient of the solution did not occur.

40 mL of silica bead colloid was slowly injected at a constant rate using a syringe and stirred for 10 minutes.

2 ml of aniline was added and kept at 2 占 폚 for 30 minutes for the initial polymerization reaction and then polymerized at 5 占 폚 for 24 hours.

After 24 hours, the reaction was recovered and centrifugation was carried out using distilled water to remove unreacted aniline and other substances. After completion of the centrifugation, it was dried with ethanol to obtain silica-bead-containing polyaniline (silica-PANI).

(B) Step: Silica Bead  contain Of the polyaniline (silica-PANI)  Heat treatment

The silica bead-containing polyaniline (silica-PANI) obtained in the step (A) was placed in a tube furnace, subjected to a primary heat treatment at 300 ° C. for 1 hour in an argon atmosphere, followed by a secondary heat treatment at 800 ° C. for 3 hours, The bead-containing polyaniline (silica-PANI) was carbonized, and other unreacted organics and impurities were removed. At this time, the argon gas flow rate is set to a maximum value during the initial 10 minutes, the quartz in the tube furnace is made into an argon quartz, and then a small amount of gas can be flowed by adjusting the flow rate.

(C) Step: Silica bead removal

The silica bead-containing polyaniline (silica-PANI) heat-treated in the step (B) was immersed in an aqueous solution of 1 M NaOH at 100 ° C using an autoclave and reacted for 24 hours to remove the silica beads.

Thereafter, the solution was filtered with distilled water, and the remaining NaOH aqueous solution was washed out to obtain a porous non-platinum catalyst.

Comparative Example  One: Sulfuric acid Ammonium (APS)  Fabricated porous nitrogen-carbon structure

A porous nitrogen-carbon structure was prepared in the same manner as in Example 1 except that ammonium persulfate (APS) was used instead of FeCl ₃ .6H ₂ O.

Comparative Example  2: Sulfuric acid  ammonium( APS )and FeCl ₃ · 6 H ₂ O Fabrication of Porous Iron-Nitrogen-Carbon Structures Using

Embodiment was carried out as Example 1, using a mixture of FeCl ₃ · 6H ₂ O Instead of ammonium persulfate (APS) and FeCl ₃ · 6H ₂ O porous iron-carbon structure - N . At this time, ammonium persulfate (APS) and FeCl ₃ .6H ₂ O were mixed at the same mole number as aniline, respectively.

Comparative Example  3: Manufacture of mixed structure of porous nitrogen-carbon structure and carbon black

In order to confirm the effect of the carbon black on the porous nitrogen-carbon structure prepared in Example 1, the porous nitrogen-carbon structure prepared in Example 1 was mixed with vulcan carbon, which is carbon black, , The carbon black was mixed in a weight ratio of 1: 1 to finally prepare the structure.

Comparative Example 4: Platinum catalyst

Pt / C catalyst, a commercially available platinum catalyst, was prepared.

Test Example 1: Analysis of structure and shape of particles

In order to analyze the structure and shape of the porous non-platinum catalyst particles prepared in Example 1, they were observed with a scanning electron microscope (SEM) and an electron transmission microscope (TEM).

FIG. 2 is a SEM photograph of the porous non-platinum catalyst particles prepared in Example 1, FIG. 3 is a TEM photograph (a) - (c) of the porous non- dispersive X-ray spectroscopy analysis (d).

Referring to FIGS. 2 (a) and 2 (b) and 3 (a) to 3 (c), it can be seen that many pores are formed in the particles.

3 (d), it can be seen that the silica beads are removed.

Test Example 2: Evaluation of specific surface area and pore distribution of particles

Nitrogen adsorption / desorption experiments were carried out to evaluate the specific surface area and pore distribution of the porous non-platinum catalyst particles prepared in Example 1.

FIG. 4 is a nitrogen adsorption / desorption curve for the porous non-platinum catalyst prepared in Example 1. FIG.

Referring to FIG. 4, it can be seen that there are many meso pores having a diameter of 2 nm or more and 50 nm or less, and many macropores having a diameter of 50 nm or more and 100 nm or less.

Table 1 below shows the specific surface area, total pore volume, at desorption, and average pore size at desorption of the porous non-platinum catalyst.

Example 1 Specific surface area (BET) 1,147 m 2 / g Total pore volume
(at desorption) 3,151 cm3 / g Average pore size
(at desorption) 9.71 nm

As shown in Table 1, the specific surface area of the porous non-platinum catalyst prepared in Example 1 was 1,147 m 2 / g, the total pore volume was 3,151 cm 3 / g, and the average pore size at desorption is 9.71 nm.

Test Example 3: Evaluation of Oxygen Reduction Reaction

The initial performance of the ORR (Oxygen reduction reaction) polarization was evaluated through a half cell employing the catalysts of the Examples and Comparative Examples, respectively.

5 is a graph showing initial performances of ORR polarization for a half cell to which the catalysts of Example 1 and Comparative Examples 1 to 3, respectively, are applied.

The ORR characteristics of the catalyst at 1600 rpm are determined by diffusion at potentials below 0.7 VRHE and by diffusion and reaction at 0.7 VRHE to 0.9 VRHE.

Referring to FIG. 5, it can be seen that the performance of the porous non-platinum catalyst of Example 1 is excellent over the entire range measured in comparison with Comparative Examples 1 to 3.

6 is a graph showing initial performances of ORP polarization for a half-cell to which the porous non-platinum catalyst of Example 1 and the commercial platinum catalyst of Comparative Example 4 are respectively applied.

Referring to FIG. 6, it can be seen that the porous non-platinum catalyst of Example 1 exhibits the same level of performance as that of the commercially available platinum catalyst of Comparative Example 4.

FIG. 7 is a graph showing currents measured over time for a half-cell to which a porous non-platinum catalyst according to Example 1 and a conventional platinum catalyst according to Comparative Example 4 are respectively applied.

Referring to FIG. 7, it can be seen that the porous non-platinum catalyst of Example 1 exhibits the same level of durability as that of the conventional platinum catalyst of Comparative Example 4.

It will be apparent to those skilled in the art that the present invention is not limited to the embodiments described above and that various changes and modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims. As shown in FIG.

It will be understood by those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention as defined by the appended claims and their equivalents. .

Claims (9)

(A) mixing and polymerizing (a1) a transition metal precursor, (a2) silica bead and (a3) nitrogen-containing monomer to obtain a silica bead containing polymer;
(B) heat treating the silica bead containing polymer; And
(C) reacting the heat-treated silica bead-containing polymer with an alkali solution to remove the silica beads from the silica bead-containing polymer, the method comprising:
The transition metal precursor (a1), the silica bead colloid (a2), and the nitrogen-containing monomer (a3) are mixed in a molar ratio of 1-10: 2-10: 1,
The silica bead-containing polymer has a shape in which the silica beads are bonded to the inside and the surface of a spherical particle made of a polymer,
The heat treatment in the step (B) may include: a first heat treatment step of heating at 100-300 ° C for 30 minutes to 2 hours; And a second heat treatment step of heating at 400-1000 DEG C for 1-5 hours,
Wherein the porous non-platinum catalyst comprises mesopores having a diameter of 2 to 50 nm and macropores having a diameter of 50 to 100 nm. delete The method of claim 1, wherein the transition metal is selected from the group consisting of Fe, Co, Ti, V, Mn, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, Platinum catalyst for fuel cells according to claim 1, The method of claim 1, wherein the transition metal precursor (a1) is at least one selected from chloride, oxide, hydroxide, nitrate, sulfate, acetate, acetylacetonate and formate salts of the transition metal. A method for producing a platinum catalyst. The process for producing a porous non-platinum catalyst according to claim 1, wherein the (a2) silica beads have a particle diameter of 1-100 nm. The method of claim 1, wherein the nitrogen-containing monomer (a3) is at least one selected from aniline, pyrrole, and acrylamide. The method of claim 1, wherein the polymer is at least one selected from the group consisting of polyaniline, polypyrrole, and polyamide. delete The method for producing a porous non-platinum catalyst for a fuel cell according to claim 1, wherein the alkali solution is at least one selected from an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide.

Images