KR20130087248A - A process of preparing electrocatalysts for oxygen reduction reaction by using stabilizers - Google Patents

Abstract

PURPOSE: A manufacturing method of an electrocatalyst is provided to have a narrow particle size distribution, a small alloy particle size, a high carrier dispersion amount and uniformity, and low agglomeration due to temperature. CONSTITUTION: A manufacturing method of an electrocatalyst comprises a step of obtaining a carbon solution; a step of obtaining a precursor solution; a step of obtaining a mixed solution by mixing the carbon solution and the precursor solution; a step of preparing a stabilizer solution; a step of obtaining a stabilizer mixed solution by adding the stabilizer solution into the mixed solution; a step of manufacturing a reductant solution; a step of conduct the reaction between the stabilizer mixed solution and the reductant solution; a step of manufacturing a catalyst by removing suspended materials and washing and drying residues; and a step of treating the catalyst with heat.

Description

A process of preparing electrocatalysts for oxygen reduction reaction by using stabilizers

The present invention relates to a method for producing an electrode catalyst for oxygen reduction reaction using a stabilizer, and more particularly, to a method for producing an electrode catalyst for oxygen reduction reaction using hexadecyltrimethylammonium bromide (CTAB) as a stabilizer.

One of the main research topics for low temperature proton exchange membrane fuel cells (PEMFCs) is the development of Pt-based catalysts with better oxygen reduction reaction (ORR) activity than pure Pt. Pt alloys containing transition metals or other noble metals or nanostructure controlled catalysts comprising core-shell nanoparticles and nanotubes are representative examples of such studies. These findings not only control physical properties such as electron conductivity and surface area, but also change the electronic structure of the catalyst in a more favorable state for oxygen reduction.

Although these recent studies of the complex nanostructures of catalysts have made significant improvements in ORR activity, there are still various problems in commercializing nanostructured catalysts. For example, the complexity of the manufacturing process, durability, membrane electrode assembly (MEA), and the like can be listed as such problems. In this regard, Pt-M alloy catalysts, which replace pure Pt as next-generation catalysts, will be more effective, although stability is threatened due to leaching problems of the second metal (M) during PEMFC operation. It is observed.

When simultaneously reducing the transition metal and Pt to prepare an alloy, the difference in the reduction potential of Pt and the transition metal has a great effect on the reaction. For example, frequently used Pt precursors and Co precursors have redox potentials of 0.735 V (vs. SHE, PtCl ₆ ^-2 / Pt) and -0.277 V (vs. SHE, Co ²⁺ / Co), respectively. Due to the large difference in the reduction potential, Pt ions preferentially reduce to Pt.

For this reason, there are still problems to be solved, directly or indirectly, such as large alloy particle size or wide particle size distribution, agglomeration of catalyst particles in the manufacturing process, low carrier dispersion amount or dispersion uniformity, and the like. As a result, excellent ORR activity and voltage-current characteristics can be exhibited.

In order to solve this problem of the prior art, the oxygen reduction reaction characterized by using hexadecyltrimethylammonium bromide (CTAB) as a stabilizer, especially in the preparation of Pt-Co / C or Pt-Fe / C electrode catalyst The present invention provides a method for preparing an electrode catalyst.

The electrode catalyst for oxygen reduction reaction prepared according to various embodiments of the present invention has a small alloy particle size, a narrow alloy particle size distribution, a high carrier dispersion amount and a uniform carrier dispersion, and agglomeration due to temperature. The occurrence of (agglomerization) is greatly reduced, resulting in excellent effects of ORR activity (mass activity) and voltage-current characteristics (current density).

1 shows the molecular structure of the stabilizer used. (a) SA, (b) TOAB, (c) OAM, (d) CTAB
2A is a result of temperature programed reduction (TPR) analysis for a stabilizer. (a) SA, (b) TOAB, (c) OAM, (d) CTAB
Figure 2b shows the thermal conductivity of the flow gas and gas that may have been decomposed from the stabilizer during the heat treatment process.
3A is an ORR polarization curve of a Pt ₃ Co _x / C alloy electrode catalyst prepared in Examples and Comparative Examples of the present invention. (a) SA, (b) TOAB, (c) OAM, (d) CTAB
FIG. 3B shows the kinetic current density and the amount of stabilizer used for the Pt ₃ Co _x / C alloy electrode catalysts prepared in Examples and Comparative Examples of the present invention.
4 shows the mass activity of a commercial 40 wt% Pt / C and 40 wt% Pt ₃ Co _x / C alloy electrode catalyst prepared in Examples and Comparative Examples of the present invention. The concentration of each stabilizer was chosen in FIG. 3A based on the highest geometric current density at 0.9 V.
5 is a TEM photograph of the Pt ₃ Co _x / C alloy electrode catalyst prepared in Examples and Comparative Examples of the present invention. Left and right are alloy catalyst images before and after heat treatment, respectively. The alloy composition of each sample was obtained from ICP-AAS analysis.
6 is an XRD analysis result of a commercial Pt / C catalyst and a Pt ₃ Co _x / C alloy catalyst prepared in Examples and Comparative Examples of the present invention. (a) before heat treatment, (b) after heat treatment. Particle size was calculated using the Scherrer equation.
In FIG. 7, particle size distributions of 40 wt% Pt / C and 40 wt% Pt ₃ Co _x / C alloy electrode catalysts prepared in Examples and Comparative Examples of the present invention were compared.
8A is a TEM photograph of a PtFe / C catalyst prepared in the presence of (a) a commercial Pt / C catalyst, (b) OAM, (c) CTAB, and (d) TOAB.
8B shows the results of XRD analysis of the PtFe / C catalyst before (a) heat treatment and (b) heat treatment.
FIG. 8C is an IV curve for ORR for commercial Pt / C catalysts and PtFe / C catalysts prepared using OAM, CTAB, TOAB. All PtFe / C catalysts were used after heat treatment, the electrolyte was an O ₂ saturated 0.1 M HClO ₄ solution and the working electrode was rotated at 1600 rpm.
8d is a TEM photograph of the PtFe / C catalyst prepared in Examples and Comparative Examples of the present invention. CTAB with (a) 1 times and (b) 10 times the total moles of Pt and Fe ions.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

One aspect of the present invention is a method for preparing an electrode catalyst for oxygen reduction reaction, wherein the electrode catalyst is Pt-Co / C or Pt-Fe / C, and hexadecyltrimethylammonium bromide (CTAB) is used as a stabilizer. It relates to a method for producing an electrode catalyst for oxygen reduction reaction characterized by.

Thus, it was confirmed that when the CTAB is used as a stabilizer, particularly, the ORR activity is greatly improved as a result of the Pt-Co / C or Pt-Fe / C catalyst.

According to one embodiment, the method for producing an electrode catalyst for the reduction reaction comprises the steps of (a) dissolving carbon in anhydrous ethanol solvent to obtain a carbon solution, (b) the first metal precursor and the second metal precursor anhydrous ethanol solvent Dissolving in to obtain a precursor solution, (c) mixing the carbon solution and the precursor solution to obtain a mixed solution, (d) hexadecyltrimethylammonium bromide (CTAB) in anhydrous ethanol solvent to stabilizer solution (E) adding the stabilizer solution to the mixed solution to obtain a stabilizer mixed solution, (f) dissolving NaBH ₄ in anhydrous ethanol to prepare a reducing agent solution, (g) mixing the stabilizer Performing the reaction by adding the reducing agent solution to the solution, (h) after the reaction, removing suspended solids and washing the residue to dry (first metal)-(second metal) / C Preparing a treated catalyst, (i) a method for producing an electrode catalyst for oxygen reduction reaction is provided it characterized in that it comprises the step of heat-treating the untreated catalyst.

According to another embodiment, the first metal precursor and the second metal precursor are PtCl ₄ and CoCl ₂ .H ₂ O, respectively, or the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively. There is provided a method for producing an electrode catalyst for oxygen reduction reaction. It has been found that the particle size distribution of the resulting alloy particles can be greatly widened when other materials are used without using the material as precursors of the first and second metals.

According to another embodiment, the first metal precursor: the second metal precursor is dissolved in the anhydrous ethanol solvent in a 2.5-3.5: 1 molar ratio to obtain the precursor solution of the electrode catalyst for oxygen reduction reaction A manufacturing method is provided. In the present invention, when the mixing ratio of the first metal precursor and the second metal precursor is out of the above range it was confirmed that the problem of aggregation with each other in the heat treatment step may occur.

According to another embodiment, when the first metal precursor and the second metal precursor are PtCl ₄ and CoCl ₂ .H ₂ O, respectively, 22-27 times the total moles of the first metal and the second metal. A CTAB stabilizer is added to the mixed solution to obtain the stabilizer mixed solution, and the total moles of the first metal and the second metal when the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively. Provided is a method for preparing an electrode catalyst for oxygen reduction reaction, wherein the CTAB stabilizer is added to the mixed solution at 0.5-15 times or 4-6 times to obtain the stabilizer mixed solution. In each of the above cases, it was found that the amount of the CTAB stabilizer dispersed in the carbon carrier can be significantly lowered.

According to another embodiment, there is provided a method for producing an electrode catalyst for the oxygen reduction reaction, characterized in that in the step (e) to add the stabilizer solution by dropping the mixed solution to the mixed solution to prepare the stabilizer mixed solution. . As described above, it was confirmed that the catalyst particles may not be uniformly dispersed in the carrier when a large amount of the stabilizer solution was added dropwise to the mixed solution without dropping.

According to another embodiment, the electrode catalyst for the oxygen reduction reaction, characterized in that to dissolve the NaBH ₄ in the anhydrous ethanol at 8-12 times the total moles of the first metal and the second metal. Provided is a method for preparing. When the amount of the NaBH ₄ reducing agent is out of the above range it was confirmed that the size of the alloy particles can be increased and the size distribution can be widened.

According to another embodiment, in (i) the heat treatment is provided a method for producing an electrode catalyst for the oxygen reduction reaction, characterized in that performed at 240-260 ℃. It has been found that when the heat treatment temperature is out of the above range, the stabilizer which is not removed may remain on the alloy catalyst surface or the ORR activity may decrease.

According to another embodiment, in (i) the heat treatment is provided a method for producing an electrode catalyst for the oxygen reduction reaction, characterized in that performed in a mixed gas environment of argon and hydrogen. It was confirmed that the alloy particles may aggregate during the heat treatment when the heat treatment is performed in a single gas environment of argon or hydrogen, or in a different gas environment.

According to another embodiment, in the step (i), the heat treatment is the production of the electrode catalyst for the oxygen reduction reaction, characterized in that the argon and the hydrogen is carried out in a mixed gas environment consisting of a volume ratio of 18-21: 1. A method is provided. When the heat treatment is performed in an environment in which the mixing ratio of argon and hydrogen is out of the above range, it was confirmed that the carrier dispersion amount and the carrier dispersion uniformity may be greatly reduced during the heat treatment process.

According to another embodiment, the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively, and in step (g), the reducing agent solution is reacted by adding the stabilizer mixture solution at room temperature and in an argon environment. There is provided a method for producing an electrode catalyst for the oxygen reduction reaction, characterized in that to perform. Another aspect of the present invention relates to an electrode catalyst for an oxygen reduction reaction prepared according to various embodiments of the present invention.

According to another embodiment, the catalyst for oxygen reduction reaction is provided with an oxygen reduction reaction catalyst, characterized in that the average particle size is 2.7-2.9 nm, the catalyst composition is Fe: Co = 4: 1.

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, if it is based on the disclosure of the present invention including the following examples, it is obvious that a person skilled in the art can also easily implement the present invention that does not specifically present the experimental results.

Example

Preparation Example: Substances and Reagents

Metal precursors can be prepared by using sodium borohydride, for example sodium acetate (SA, C ₂ H ₃ O ₂ Na), oleylamine (OAM, C ₁₈ H ₃₇ N), tetraoctylammonium bromide (TOAB, C ₃₂ H ₆₈ BrN), or hexadecyltrimethylammonium bromide (CTAB, C ₁₉ H ₄₂ BrN), respectively, was used as a stabilizer to reduce. The reaction was carried out in anhydrous ethanol solvent and a catalyst ink solution for electrochemical measurement was prepared using Nafion solution and isopropyl alcohol.

Example 1 and Comparative Example 1 Preparation of Alloy Electrode Catalyst

A 40 wt% Pt ₃ Co _x / C alloy electrode catalyst was prepared at room temperature in an argon atmosphere using borohydride reduction. Specifically, 0.966 g of carbon was mixed with 80 mL of anhydrous ethanol solvent and sonicated for 10 minutes. 0.03 mmol PtCl ₄ and 0.1 mmol CoCl ₂ H ₂ O were dissolved in 10 mL anhydrous ethanol solvent and sonicated for 10 min. The carbon solution and the precursor solution were mixed and stirred for 10 minutes. For each of the gastric stabilizers, four kinds of amounts of 10 times, 15 times, 20 times, and 25 times the total moles of Pt (IV) and Co (II) were dissolved in anhydrous ethanol solvent and dropped into the gas mixture solution dropwise. . Then NaBH ₄ was dissolved in 10 mL anhydrous ethanol at 10 times the total moles of metal ions and added to the stomach solution. After reacting overnight, the suspension was finally removed and the residue was washed with ethanol and dried for one day in a 40 ° C. vacuum oven. In order to remove the stabilizer remaining on the surface of the Pt-Co catalyst was heat-treated for 2 hours in a mixed gas environment of 250 ℃ and a volume ratio of argon and hydrogen 19: 1.

Example 2 and Comparative Example 2: Alloy Electrode Catalyst Preparation

0.97 g of carbon was mixed with 80 mL anhydrous ethanol solvent and sonicated for 10 minutes. 0.3 mmol PtCl ₄ and 0.1 mmol FeCl ₃ were dissolved in 10 mL of absolute ethanol and sonicated for 10 minutes. The carbon solution and the precursor solution were mixed and stirred for 10 minutes. For each of the gastric stabilizers, one or ten times the total moles of Pt and Fe were dissolved in anhydrous ethanol solvent, which was added dropwise to the gastric mixture solution. NaBH ₄ was then dissolved in 10 mL anhydrous ethanol at 10 times the total moles of metal ions, and then added to the solution at room temperature and argon. After reacting overnight, the suspension was finally removed and the residue was washed with ethanol and dried for one day in a 40 ° C. vacuum oven. In order to remove the stabilizer remaining on the surface of the Pt-Fe catalyst, heat treatment was performed at 250 ° C. for 2 hours in a mixed gas environment having a volume ratio of argon and hydrogen of 19: 1.

Test Example: Measurement Method

XRD, TEM, ICP-AAS, ORR activity, voltage-current characteristics, etc. were performed by the methods described in detail in International Journal of Hydrogen Energy 36 (2011) 12088-12095.

The test results presented below are only representative of the results of the above Examples and Comparative Examples, and the effects of each of the various embodiments of the present invention, which are not explicitly given below, are described in detail in the corresponding sections.

Since H ₂ -heat treatment also has the effect of removing oxides on the surface of particles formed during the synthesis process, in one embodiment of the present invention, heat treatment under hydrogen atmosphere was selected to remove residual stabilizers. In order to confirm the optimum heat treatment temperature for the individual stabilizers, TPR experiments were performed and the results are shown in FIG. 2A. The Thermal Conductivity Detector (TCD) allows you to monitor the difference in thermal conductivity between the flow gas and the gas produced during heat treatment, which allows you to identify the species degraded from the stabilizer and the corresponding decomposition temperature. . The thermal conductivity of possible gases that may have resulted from stabilizer decomposition during heat treatment is shown in FIG. 2B. Since higher catalytic activity was observed at low heat treatment temperatures due to thermal agglomeration prevention, one embodiment of the present invention chose the lowest temperature at which decomposition of the stabilizer occurs.

As shown in FIG. 2A, the baseline signal of the input gas represents about 1V. The TCD signal is higher than 1 V and vice versa with the generation of cracked gases having a thermal conductivity higher than that of the input gas. For example, H ₂ O and CH ₄ generate TCD signals above 1 V, and NH ₃ , CO ₂ and Br ₂ generate TCD signals below 1 V. Therefore, the signals around 100 ° C. and 200-300 ° C. shown in FIG. 2A represent H ₂ O and CH ₄ resolved from the sample. For SA with the molecular formula of C ₂ H ₃ O ₂ Na (FIG. 2A (a)), a small peak at 300-400 ° C. indicates the production of CO ₂ . Therefore, the initial heat treatment temperature of the SA-mediated Pt ₃ Co _x / C alloy catalyst was determined at 350 ° C. to remove SA from the products of CH ₄ and CO ₂ .

Subsequently in the catalyst ink solution preparation, it was observed that the catalyst powder heat-treated at 350 ° C. was not well dispersed due to partial SA residue on the catalyst surface. However, no further problem was found when the heat treatment temperature was raised to 400 ° C. Therefore, the final heat treatment temperature of the SA-mediated Pt ₃ Co _x / C alloy catalyst was chosen to be 400 ° C. Similarly, the heat treatment temperature of OAM (FIG. 2A (b)) was chosen at 350 ° C. at which OAM decomposed CH ₄ , CO ₂ , and NH ₃ without any dispersion problem. In the case of TOAB (C ₃₂ H ₆₈ BrN) and CTAB (C ₁₉ H ₄₂ BrN), the stabilizer decomposes into CH ₄ , CO ₂ , NH ₃ , and Br _{2 up} to 300 ° C.

In consideration of the fact that most of the gas is generated at around 250 ° C. due to decomposition of the dispersant, an embodiment of the present invention uses the catalyst heat-treated at 300 ° C. and 250 ° C. to form an ink solution. It was confirmed that there is no. Therefore, in order to avoid unnecessary agglomeration of the catalyst due to the heat treatment, the heat treatment temperature of the TOAB- and CTAB-mediated catalysts was set at 250 ° C. 3A shows the ORR activity of a catalyst prepared with various stabilizers. All tests were run with heat treated catalyst. Figures in the figure legend represent equivalents to the stabilizers relative to metal precursors. The polarization curves in FIG. 3A show typical ORR characteristics, ie 1.1 V vs. It shows that the oxygen reduction reaction starts in RHE. The curve passes sequentially through the charge transfer control zone, the charge transfer-mass transfer mixing zone, and finally the mass transfer control zone.

0.9 V vs. predominance for all samples showing predominantly catalytic activity. The current density in the RHE is summarized in FIG. 3B. As a reference, commercial catalysts have a geometric current density of 1980 mA / cm ² at 0.9 V. For SA-mediated Pt ₃ Co _x / C alloy catalysts, SA-10 and SA-15 show slightly higher current densities of 2320 and 2496 mA / cm ² at 0.9 V, respectively. As the amount of SA increases, the current densities become 1533 (SA-20) and 1717 (SA-25) mA / cm ² . However, in the case of OAM-mediated Pt ₃ Co _x / C alloy catalysts, all catalysts have a current density lower than that of a commercial catalyst. The best activity was observed for OAM-15 (1656 mA / cm ² ), but still showed lower current density than commercial catalysts. Unlike SA and OAM, catalysts made with TOAB and CTAB show better activity in most cases. TOAB-mediated Pt ₃ Co _x / C catalyst has 2557 mA / cm ² (TOAB-10), 3633 mA / cm ² (TOAB-15), 3475 mA / cm ² (TOAB-20) and 2888 mA / cm ² ( TOAB-25), which is 1.3-1.8 times higher than commercial catalysts.

Catalysts prepared in the presence of CTAB also show similar behavior. Depending on the amount of CTAB added, the current densities were 1931 mA / cm ² (CTAB-10), 3131 mA / cm ² (CTAB-15), 2996 mA / cm ² (CTAB-20), and 4167 mA / cm ² ( CTAB-25). Only CTAB-1 shows slightly lower activity than commercial catalysts. In particular, CTAB-25 has the highest current density of 2.1 times higher than commercial catalysts of all test catalysts.

Similar trends were observed for half-wave potential comparisons of catalysts with the highest current densities for each stabilizer. CTAB-25 (0.92 V) to TOAB-15 (0.92 V)> SA-15 (0.89 V)> commercial catalyst (0.88 V)> OAM-15 (0.87 V). The mass activities of the five catalysts at 0.9 V are shown in FIG. 4. Mass activities were calculated from the results shown in Figure 3a, the composition was analyzed using ICP-AAS analysis of the sample. Mass activities also show a trend very similar to geometric current density. CTAB-25 (31.63 mA / mgPt)> TOAB-15 (27.33 mA / mgPt)> SA-15 (17.49 mA / mgPt)> commercial (15.80 mA // mgPt)> OAM-15 (12.49 mA / mgPt). The above results show that the CTAB-25-mediated Pt ₃ Co _x / C alloy catalyst has the best activity in terms of geometric current density and mass activity.

In order to confirm the origin of better activity of the CTAB-mediated Pt ₃ Co _x / C alloy catalyst, TEM analysis was performed on five catalysts, and the results are shown in FIG. 5. TEM images were obtained from samples before and after heat treatment. For the 15 equivalent SA-mediated Pt ₃ Co _x / C catalyst, the sample produced had a small particle size but showed local aggregation. After the heat treatment, violent particle growth occurred and showed a distribution of various sizes of 3-10 nm. Pt ₃ Co _x / C prepared using OAM has better dispersibility than SA-mediated catalyst. The particle size was about 1-2 nm and sporadic aggregation was observed. Particle growth after heat treatment became more intense in many places, and the size distribution was wider in the range of 1-12 nm.

The surface morphology of the samples prepared in the presence of TOAB is similar to that of SA. After the heat treatment there was again large grain growth with a particle size in the range of 5-10 nm. The most uniform and well dispersed Pt ₃ Co _x / C is obtained from preparation by CTAB. Even after the heat treatment, the catalyst particles are much more dispersed in carbon in a relatively uniform size of 2-3 nm.

Alloying components were analyzed by ICP-AAS and the results provided at the top of the image. In most cases, the composition of Co in Pt ₃ Co _x / C (x) was lower than the expected value of Co in the alloy (x <1). This is due to the significant reduction potential difference between Pt and Co ions, even with the addition of various stabilizers. The particle size and alloy formation according to the type of stabilizer and heat treatment were further analyzed by XRD, and the results are shown in FIG. 6. Each stabilizer sample was selected based on the best ORR activity shown in FIG. 3A.

For comparison, a commercial 40 wt% Pt / catalyst was also analyzed and shown in FIG. 6. At 2-theta values of 39.7 °, 46.3 °, 67.5 ° and 81.2 ° the peaks of the commercial catalysts correspond to the typical peaks of Pt (111), Pt (200), Pt (220), and Pt (311), respectively. The particle size calculated from the XRD data is about 3.3 nm. In the case of the Pt ₃ Co _x / C catalyst, the Pt 220 peak was shifted at a high angle regardless of the type of stabilizer because of the lattice shrinkage by the alloy with small Co atoms. Pt (220) peak positions are 69.12 ° (TOAB-15)> 69.10 ° (SA-15)> 68.74 ° (CTAB-25) to 68.73 ° (OAM-15), respectively.

In all cases, the measured particle size of Pt ₃ Co _x / C is smaller than the commercial Pt / C catalyst, in order of commercial catalyst (3.3 nm)> SA-15 (2.7 nm)> TOAB-15 (2.5 nm)> OAM-15 to CTAB-25 (2.2 nm). However, after heat treatment (Fig. 6 (b)), most of the particles grow largely from 2.7 to 10.6 nm (SA-15), 2.2 to 7.6 nm (OAM-15), and 2.5 to 5.0 nm (TOAB-15). . Interestingly, a relatively slight increase in particle size was observed with the CTAB-mediated Pt ₃ Co _x / C catalyst (increased from 2.2 to 2.8 nm). This is mainly due to the relatively low heat treatment temperature of the CTAB-mediated Pt ₃ Co _x / C catalyst, whereby temperature-induced aggregation is suppressed.

In the present invention, it was confirmed that CTAB mediated Pt ₃ Co _x / C having a particle size of 2.8 nm and a composition of 4: 1 (Pt: Co) after heat treatment had the highest activity against ORR. Based on ORR results and TEM / XRD analysis, it can be concluded that, among the various stabilizer types, CTAB is most suitable for the preparation of the Pt ₃ Co _x / C alloy catalyst. In the present invention, the particle size distribution and dispersion at carbon between commercial 40 wt% Pt / C and CTAB-mediated 40 wt% Pt ₃ Co _x / C catalyst are compared, and the results are shown in FIG. 7. In the case of commercial catalysts (Fig. 7 (a)), the particle size ranges from 1 to 5 nm or more without heat treatment, showing the highest frequency at 2.5-3.5 nm. However, after heat treatment, the CTAB-mediated Pt ₃ Co _x / C catalyst (FIG. 7 (b)) had the highest frequency and narrow size distribution at 2.5 nm, which is consistent with the XRD results shown in FIG. The dispersion of Pt-Co particles on the carbon support was more uniform than commercial Pt / C catalysts. This physical feature may also contribute to the enhanced ORR activity of the CTAB-mediated Pt ₃ Co _x / C catalyst.

Claims (13)

A method of preparing an electrode catalyst for oxygen reduction reaction, wherein the electrode catalyst is Pt-Co / C or Pt-Fe / C, and is used for oxygen reduction reaction characterized by using hexadecyltrimethylammonium bromide (CTAB) as a stabilizer. Method for producing an electrode catalyst. The method of claim 1, wherein the reduction electrode catalyst
(a) dissolving carbon in anhydrous ethanol solvent to obtain a carbon solution,
(b) dissolving the first metal precursor and the second metal precursor in anhydrous ethanol solvent to obtain a precursor solution,
(c) mixing the carbon solution and the precursor solution to obtain a mixed solution,
(d) dissolving hexadecyltrimethylammonium bromide (CTAB) in anhydrous ethanol solvent to prepare a stabilizer solution,
(e) adding the stabilizer solution to the mixed solution to obtain a stabilizer mixed solution,
(f) dissolving NaBH ₄ in anhydrous ethanol to prepare a reducing agent solution,
(g) performing the reaction by adding the reducing agent solution to the stabilizer mixed solution,
(h) removing the float after the reaction and washing the residue to dry to prepare a (first metal)-(second metal) / C untreated catalyst,
(i) a method of producing an electrode catalyst for an oxygen reduction reaction, comprising the step of heat treating the untreated catalyst. The method of claim 2, wherein the first metal precursor and the second metal precursor are PtCl ₄ and CoCl ₂ · H ₂ O, respectively,
Or the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively. The method of claim 3, wherein the first metal precursor: the second metal precursor is dissolved in the anhydrous ethanol solvent in a 2.5-3.5: 1 molar ratio to prepare the electrode catalyst for the oxygen reduction reaction, characterized in that to obtain the precursor solution. Way. The CTAB of claim 4, wherein the CTAB is 22-27 times the total moles of the first metal and the second metal when the first metal precursor and the second metal precursor are PtCl ₄ and CoCl ₂ .H ₂ O, respectively. A stabilizer is added to the mixed solution to obtain the stabilizer mixed solution,
When the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively, the CTAB stabilizer is added to the mixed solution at 0.5-15 times the total moles of the first metal and the second metal. A method for producing an electrode catalyst for oxygen reduction reaction, characterized by obtaining a mixed solution. The method of claim 5, wherein in the step (e), the stabilizer solution is added by dropwise addition to the mixed solution to prepare the stabilizer mixed solution. The electrode catalyst for oxygen reduction reaction according to claim 6, wherein the NaBH ₄ is dissolved in the anhydrous ethanol at 8-12 times the total moles of the first metal and the second metal. Manufacturing method. The method of claim 7, wherein the heat treatment in step (i) is performed at 240-260 ° C. 9. The method of claim 8, wherein the heat treatment in the step (i) is a method of producing an electrode catalyst for oxygen reduction reaction, characterized in that carried out in a mixed gas environment of argon and hydrogen. The method of claim 9, wherein in the step (i), the heat treatment is performed in an environment of a mixed gas having argon and hydrogen in a volume ratio of 18-21: 1. . 8. The method of claim 7, wherein the first metal precursor and the second metal precursor are PtCl ₄ and FeCl ₃ , respectively, and in step (g), the reducing agent solution is reacted by adding the stabilizer mixture solution at room temperature and in an argon environment. Method for producing an electrode catalyst for the oxygen reduction reaction, characterized in that carried out. An electrode catalyst for an oxygen reduction reaction, according to any one of claims 1 to 11. The catalyst for oxygen reduction reaction according to claim 12, wherein the catalyst for oxygen reduction reaction has an average particle size of 2.7-2.9 nm and a catalyst composition of Fe: Co = 4: 1.

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