KR20100003780A - Process for the polymer electrolyte composite catalysts attached with ionomers - Google Patents

Abstract

PURPOSE: Polymer electrolyte composite catalysts and a manufacturing method thereof are provided to support two kinds of particles uniformly on a carbon support by attaching polymer electrolyte ionomer particles and metal particles on the carbon support. CONSTITUTION: A manufacturing method of polymer electrolyte composite catalysts includes the following steps of: manufacturing a metal nanoparticle dispersed solution by reducing a metal precursor of metal precursor liquid; manufacturing mixed liquid by mixing the metal nanoparticle dispersed solution and an ionomer solution; and forming a metal-ionomer-carbon composite in which the metal nanoparticles and the ionomer are supported. A reducing process is performed by reflux the metal precursor liquid for 30 minutes ~ 2 hours after adjusting the pH of the metal precursor liquid to 7 ~ 14. The manufacturing method of the polymer electrolyte composite catalysts further includes a step for washing the metal-ioner-carbon composite with mixed liquid of ht eater and alcohols.

Description

Process for the polymer electrolyte composite catalysts attached with ionomers}

The present invention relates to a porous electrode material used in a polymer electrolyte fuel cell, and more particularly to a method for producing a polymer electrolyte composite catalyst with an ionomer (iomomer) attached.

A fuel cell is hydrogen or methanol by the reaction of fuel with oxygen and electrochemical do not go through the conventional thermal power generation unlike the Carnot cycle to a device which directly converts chemical energy of fuel into electrical energy with high power generating efficiency NO _X, SO _X Low emissions of pollutants, such as no noise during operation is attracting attention as the next generation of clean energy sources. Depending on the electrolyte used, the fuel cell may be a polymer electrolyte fuel cell (PEMFC), a phosphate acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), or a solid oxide fuel. It is classified into a solid oxide fuel cell (SOFC). Among them, the polymer electrolyte fuel cell has a lower operating temperature and a higher power generation efficiency. The use of mobile and emergency power supplies, military power supplies, etc. is promising.

The polymer electrolyte fuel cell has a seven-layer structure of a separator / gas diffusion electrode / fuel electrode / polymer electrolyte membrane / air electrode / gas diffusion electrode / separator. The five-layer structure excluding the separators on both sides is called a membrane-electrode assembly (MEA). Referring to the operating principle of the fuel cell, first, fuel such as hydrogen or methanol is uniformly supplied to the fuel electrode through the flow path of the separator and the gas diffusion electrode, and air or oxygen is supplied to the air electrode like the fuel electrode. It is supplied evenly through the electrode. At the fuel electrode, the fuel is oxidized to generate hydrogen ions and electrons. At this time, the hydrogen ions move toward the air electrode through the electrolyte membrane, and the electrons move toward the air electrode through the conductor and the load constituting the external circuit. . Hydrogen ions and electrons react with oxygen at the air electrode to produce water, and water is discharged to the outside of the fuel cell.

Both electrodes of the polymer electrolyte fuel cell are manufactured by applying an ink consisting of a catalyst, a polymer electrolyte and a solvent on a carbon species or a carbon cloth to form a catalyst layer in order to activate the redox reaction. As the catalyst, a commonly known platinum-based catalyst having a platinum or platinum / ruthenium alloy having excellent catalytic activity on a carbon granular support is put to practical use.

The characteristics of the catalyst for the polymer fuel cell require a large specific surface area of the metal particles, a strong binding force between the metal particles and the support, endothelial toxicity to carbon monoxide (CO), and chemical uniformity between the metal atoms in the alloy. Metal particles should not be aggregated on the surface of the granular support, but should be supported uniformly and in large amounts, thereby increasing the electrochemical catalytic activity.

In a conventional catalyst preparation method, an aqueous solution of a platinum compound or an aqueous solution of a platinum compound and a ruthenium compound is mixed with a carbon powder as a carrier to disperse and precipitated particles by adding a reducing agent such as sodium borohydride (NaBH ₄ ), alcohol, aldehyde, and the like. Adsorption reduction (J Power Sources, 2005, 250) for reducing or heat treatment in a hydrogen atmosphere is generally used. Although this method is easy and simple, it has been pointed out that when the amount of metal particles is increased, it is difficult to uniformly support them without aggregation and it is very difficult to control the size of the particles.

Another method is the colloidal method proposed by Watanabe (Japanese Patent 2005-63713). This method makes it possible to uniformly precipitate particles on colloids using NaHSO ₃ , H ₂ O ₂ as reducing agents, but it is difficult to control the intermediates generated in the pH and reaction stages, and because the phases of particles precipitate in the form of oxides, The problem has been pointed out that the cost of hydrogen is required to increase the production cost.

Another method is the Bonnemann method (Eur. J. Inorg. Chem., 2001, 2455), in which a metal particle stabilized with a surfactant is first synthesized and then attached to a carbon carrier to prepare a catalyst. Problems have been pointed out that using tetrahydrofuran (THF), high temperature hydrogen heat treatment is required, such as the Watanabe method, and the binding strength between the metal particles and the carbon carrier is relatively weak.

As a method of preparing a membrane-electrode composite, a method of directly applying an ink composed of a catalyst, a polymer electrolyte, and a solvent to a polymer electrolyte membrane is generally used. Many attempts have been made to improve the performance of electrode composites.

As an attempt to control the pore structure of the catalyst layer by changing the composition of the ink as in the former, and to improve the electrochemical performance through this, the catalyst carrier and one kind such as to have a three-dimensional network-like porous structure as in Japanese Patent Laid-Open No. 2000-353528. Using the above polymers, the catalyst polymer composite may be synthesized and used in the ink, or alternatively, it may be used in the ink as described in Japanese Patent Application Laid-Open No. 08-264190 and Kim's paper (JH Kim etal, J. Power Sources 135 (2004) 29.). Ionomer, a polymer electrolyte, is colloidalized in a dispersing solvent and adsorbed to catalyst particles to be used in ink. Alternatively, as in Japanese Patent Application Laid-Open No. 2000-188110, Japanese Patent Application No. 2005-108827, the molecular weight of the ionomer contained in the ink is adjusted to be used in the ink. However, there are examples of gas diffusion, ion conductivity, and moisture retention in the applied catalyst layer. The effective reaction area (commonly referred to as the three-phase interfacial reaction area) is low, which makes it difficult to express the performance.The utilization of the catalyst that participates in the electrochemical reaction through the three-phase interface is low, resulting in a cost increase due to overuse of the catalyst. Problems have been pointed out in that it is difficult to select solvents and additives compatible with ionomers in the preparation of catalyst inks and the process is complicated.

An object of the present invention is to improve the utilization of the catalyst to participate in the electrochemical reaction through the three-phase interface of the three components of the polymer electrolyte, metal nanoparticles and carbon carriers of the catalyst layer used in the polymer electrolyte fuel cell The present invention provides a catalyst and a method for preparing the same, and more specifically, a metal electrolyte composite catalyst having a large electrochemically active area and a method for preparing the same, wherein metal catalyst particles and ionomer particles having different roles on the carbon carrier are uniformly dispersed and combined. To provide.

In addition, another object of the present invention is to improve the effective reaction area of the gas diffusion, ion conductivity, and moisture retention by using the polymer electrolyte composite catalyst, thereby improving the performance and durability of the fuel cell membrane-electrode assembly for fuel cells To provide, and to provide a fuel cell comprising the membrane-electrode assembly.

The present invention is designed to solve the above-mentioned problems, by first producing uniform metal nanoparticles of 1 ~ 10nm by applying a generic "in-situ template synthesis method" and then ionomer particles when the metal nanoparticles are supported on a carbon carrier The present invention relates to a method for producing a commonly-known "polymer electrolyte composite catalyst" in which two kinds of particles serving different roles on the same carbon support can be uniformly and evenly loaded on the same carbon support.

According to the present invention, the polymer electrolyte composite catalyst can be prepared with only a solvent without adding an additional ionomer, and thus, when applied to a membrane-electrode assembly (MEA) or a fuel cell using the same, an electrochemical The large active area improves performance, facilitates the manufacturing process, and improves durability.

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

At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art. In addition, repeated description of the same technical configuration and operation as in the prior art will be omitted.

As shown in FIG. 1, the polymer electrolyte composite catalyst according to the present invention is a metal nanoparticle represented by platinum or platinum alloy particles and ionomer particles such as Nafion, simultaneously supported on a carbon carrier when the catalyst is prepared. The size of the metal nanoparticles is 1 to 10 nm, the weight ratio (C: D) of the metal nanoparticles (C) and the ionomer (D) is 1: 0.1 to 10, and the total weight of the metal nanoparticles and the ionomer (C + D) The weight ratio (E: C + D) of the carbon support (E) is 1: 0.01 to 0.9, and the metal nanoparticle dispersion prepared by reducing the metal precursor of the metal precursor solution and the ionomer solution were mixed to prepare a mixed solution. After the mixture is characterized in that it is prepared by mixing the carbon carrier.

The preparation method of the polymer electrolyte composite catalyst according to the present invention specifically includes the following preparation steps.

a) reducing the metal precursor of the metal precursor solution to prepare a metal nanoparticle dispersion;

b) mixing the metal nanoparticle dispersion and ionomer solution to prepare a mixed solution;

c) mixing the carbon carrier with the mixed solution to form a metal-ionomer-carbon composite on which metal nanoparticles and ionomers are supported.

The metal precursor solution of step a) includes a solvent, and the reduction may be performed by adjusting the acidity of the solution to neutral or basic and refluxing, and after the reduction, the step of aging the metal nanoparticle dispersion at room temperature It may further include.

In addition, the step c) may further comprise the step of washing the metal-ionomer-carbon complex with a mixture of water and alcohols.

Figure 1 shows one embodiment of a method for producing a polymer electrolyte composite catalyst according to the present invention with reference to the manufacturing process of Figure 1 will be described in more detail the method for producing a polymer electrolyte composite catalyst of the present invention.

In FIG. 1, the solvent used to prepare uniform metal nanoparticles can be converted into a surface modifier having a functional group upon application of temperature, thereby forming micelles around the particles when the nuclei of the nanoparticles are formed and grown in solution. The solvent which has a functional group which can form and act as a template is preferable, The said functional group is 1 or more types chosen from a hydroxyl group (OH), an aldehyde group (COH), or a carboxy group (COOH), and as a solvent which has the said functional group It can be selected from glycolic acid, glyoxal, oxalic acid, acetaldehyde, ethylene glycol or a mixture thereof.

The metal precursor is preferably a substance soluble in the solvent, and is a metal chloride, a metal hydrochloride, a metal acetylacetone compound, a metal ammonium salt, a metal bromide or a mixture thereof, and the metal is Pt, Pd, Os, Ir, Ru, Metal alloy nanoparticles can be formed using two or more metal precursors which are at least one selected from Co, Fe, Mo, W, Cr, and Ni, and whose metal components are different.

The weight ratio (A: B) of the metal precursor (A) and the solvent (B) is preferably 1: 1 to 1: 200, and when the weight ratio is lower than 1: 1, the process cost increases according to the required production amount, and the weight ratio is 1 When it is higher than 200, there may be an aggregation phenomenon between metal particles.

It is preferable to adjust the acidity of the metal precursor solution to be neutral or basic, more specifically pH 7-14, before the reduction reaction of the metal precursor of step a). It is possible to obtain uniform metal nanoparticles of 1-10 nm by adjusting the acidity of the metal precursor solution to neutral or basic, better basic, and of non-uniform size when the acidity of the metal precursor solution is acidic, more specifically below pH 7. This is because it is disadvantageous to obtain nanoparticles.

The mixed solution of the metal precursor and the solvent is refluxed at the boiling point of the solvent, but a reaction time of 30 minutes to 2 hours is suitable for sufficient particle formation. In less than 30 minutes, the formation of particles is not complete, and in excess of 2 hours, aggregation of the particles may occur.

The size of the metal nanoparticles produced in the reduction of the metal precursor is preferably 1 to 10 nm or less. The particle size is directly related to the active area of the catalyst, and the smaller the particle size is, the larger the active area is, but the disadvantage is that durability is poor. When the size of nanoparticles is less than 1nm under the same platinum loading, the activity of nanoparticles themselves increases and the distance between particles increases, so that they may melt or coalesce during fuel cell operation. Due to the large size and long distance between particles, durability is good during fuel cell operation, but the active area is reduced, leading to deterioration of overall fuel cell performance.

The dispersion containing the metal nanoparticles may be subjected to the step of aging for at least 1 hour at room temperature for the purpose of ensuring the stability of the metal nanoparticles. Specifically, about 1 to 5 hours are preferable in consideration of effects and process time.

As a next step, step b) is to uniformly mix the metal nanoparticle dispersion prepared in step a) and the ionomer solution to prepare a mixed solution of the metal nanoparticles and the ionomer.

In the mixing of the metal nanoparticle dispersion and the ionomer solution, the weight ratio (C: D) of the metal nanoparticles (C) and the ionomer (D) is preferably 1: 0.1 to 1:10, which is the weight ratio (C: D). When the amount of ionomer is less than 1: 0.1, the adhesiveness of the electrode is decreased when the MEA is applied, and the conductivity of hydrogen ions may also decrease, and when the amount of the ionomer is too high in excess of 1:10. This is because the nanoparticles are covered by the ionomer and the active area decreases relatively.

The ionomer solution is an ionomer dispersed in water, a lower alcohol or a mixed solvent thereof, and the ionomer may be defined as a copolymer including an electrically neutral repeating unit and an ionized unit as a polyelectrolyte, and a polymer In the field of electrolyte fuel cells, it usually means a fluorine resin having a sulfonic acid group (SO ₃ H), and a sulfonated tetrafluoroethylene copolymer, which is typically referred to as "Nafion", is exemplified. As the ionomer solution, a commercially available Nafion solution (Nafion 5wt% Solution (DE521, Dupont)) may be used.

The next step is to form a metal-ionomer-carbon composite by adding a carbon carrier to the mixed solution of the metal nanoparticles and the ionomer to support the metal nanoparticles and the ionomer on the carbon carrier. In this case, the carbon carrier (E) preferably has a weight ratio (E: C + D) of 1: 0.01 to 1: 0.9 with respect to the total weight (C + D) of the metal nanoparticles and the ionomer. When the weight ratio is less than 1: 0.01 and the total weight of the metal nanoparticles and the ionomer is small, there may be a problem that the electrical activity of the catalyst is lowered. When the weight ratio exceeds 1: 0.9, the metal nanoparticles and the ionomer The amount may be disadvantageous in that the amount of the metal nanoparticle supported dispersion on the carbon support is lowered and may cause secondary aggregation of the metal nanoparticles.

Formation of the three-phase interface of the membrane-electrode assembly largely depends on the weight ratio (C: D) of the metal nanoparticles (C) and the ionomer (D) and the mixing weight ratio of the carbon carrier (E). The weight ratio (C + E: D) of the ionomer (D) to the sum (C + E) of the metal nanoparticles and the carbon support is preferably 1: 0.2 to 1: 0.5. This does not give sufficient bonding force between the electrode and the electrolyte membrane when the ionomer content is smaller than the above range, and decreases the catalytically active area when the ionomer content is above the above range.

The carbon carrier used in the present invention is a conductor having a porous pore structure, and a porous carbon material having electrical conductivity such as carbon black, carbon nanotubes, carbon fibers, and fullerenes is preferable, and when carrying the metal nanoparticles and ionomers, Reactor temperature is below 100 ℃, more preferably from room temperature to 100 Stirring time at ℃ is more than 1 hour, leave enough time to support. If the temperature is more than 100 ℃ solvent may be volatilized, there is a disadvantage that the size of the metal particles can be increased.

It is preferable to further include the step of cleaning the metal-ionomer-carbon composite after the step c). The cleaning is necessary to remove residual reaction solvents and side reaction ions such as Na ⁺ and Cl ^- dissolved in the solvent. The cleaning solution is a mixture of water and alcohols and the weight ratio (water: alcohols) of the composition is 1: 0.1 to 1:10 is suitable. When the weight ratio is less than 0.1, but greater than 10, the ionomer may phase separate. Normally, sufficient cleaning is required four times or more, and the remaining impurities may cause performance deterioration during the development of the membrane-electrode assembly.

The present invention provides a catalyst ink containing a polymer electrolyte composite catalyst prepared by the above production method. Typically, the ink is prepared by adding a Nafion-based ionomer solution when preparing a catalyst ink for a polymer electrolyte fuel cell, but the polymer electrolyte composite catalyst according to the present invention is mixed with the polymer electrolyte composite catalyst according to the present invention without mixing with the ionomer solution. It can manufacture by disperse | distributing to alcohol, its mixed solvent, etc.

In another aspect, the present invention provides a membrane-electrode assembly (MEA) comprising the polymer electrolyte composite catalyst, the membrane-electrode assembly provides a fuel cell. The fuel cell includes at least one unit fuel cell or fuel cell stack or a fuel cell system using the fuel cell. The unit fuel cell includes a cathode / gas diffusion layer / gasket / membrane-electrode assembly / gasket / gas diffusion layer / anode, and the fuel cell stack includes a current collector / anode / polymer electrolyte membrane / anode / current collector / cathode / polymer electrolyte. And a fuel cell system including a terminal connected to supply fuel and an oxidant to the stack, the cathode and the anode, and a battery case surrounding and enclosing the stack. Include.

As described above, in the polymer electrolyte composite catalyst according to the present invention, the metal nanoparticle and the ionomer are uniformly dispersed and bonded to the carbon carrier, and thus, a membrane-electrode assembly (MEA) or a membrane is used as a catalyst ink containing the same. When applied to a fuel cell using an electrode assembly, the electrochemically active area is larger than that of the conventional catalyst ink, and the effective reaction area (commonly referred to as three-phase interfacial reaction area) that is compatible with gas diffusivity, ion conductivity, and moisture retention is large. The result is a marked improvement in electrical activity and simplicity in the manufacturing process as well as improved durability.

Hereinafter, the present invention will be described in more detail based on the following Examples and Comparative Examples. However, the following examples are merely examples of the present invention, and the scope of the present invention is not limited thereto.

EXAMPLE

(1) Preparation of Polymer Electrolyte Composite Catalyst

0.5 g of platinum chloride (PtCl ₄ , Kojima, 99.9%) is dissolved in 100 ml of EG (Ethylene Glycol, Junsei, 98%) for 1 hour, and the solution is titrated with NaOH so that the solution has a pH of 11. The titrated solution was rapidly heated up to 30 ° C. within 30 minutes to reflux for 3 hours to prepare a dispersion in which platinum nanoparticles of uniform size were formed at an average of 2 nm. Stir at room temperature for 3 hours until the temperature of the dispersion is cooled to room temperature. After stirring, an ionomer solution (Nafion 5wt% Solution (DE521, Dupont)) was added to the dispersion so that the weight ratio of platinum and Nafion was 1: 1 and stirred for 1 hour. Then, carbon particles (Cabot, Vulcan XC 72R) are added to the carbon carrier so that the weight ratio of carbon to platinum is 7: 3, and stirred for 24 hours to simultaneously support platinum and ionomer. To clean the supported catalyst, 5 L of water and alcohol (DI Water: IPA = 5: 5, weight ratio) was mixed 5 times with 1 L each, filtered and dried, and the Pt / The C polymer electrolyte composite catalyst was obtained, and the ionomer content of the Pt / C catalyst was confirmed to be 20 wt% through TGA (Thermogravimetric Analysis) analysis.

(2) Evaluation of Polymer Electrolyte Composite Catalyst

Scanning electron microscopy (SEM) was used for surface analysis and elemental analysis of the polymer electrolyte composite catalyst, and RDE (Rotating Disk Electrode) analysis was performed to evaluate the electrochemical properties.

In order to understand the electrochemical properties and performance of the polymer composite catalyst, a three-electrode cell composed of a reference electrode, a counter electrode, and a working electrode was constructed. SCE (saturated calomel electrode) was used as the reference electrode and carbon was used as the counter electrode. In order to construct a working electrode, a glassy carbon electrode, which is a kind of carbon electrode, was used, and a working electrode was prepared by applying a catalyst on the carbon electrode.

Catalyst ink was prepared to apply the catalyst on the carbon electrode. The catalyst ink used water and isopropyl alcohol. In order to apply the same amount of catalyst onto the working electrode, the same volume of catalyst ink was used and the electrochemical properties of the catalyst were evaluated after drying in a 70 ° C. oven. As evaluation methods, CV (cyclic voltammetry), LSV (linear sweep voltammetry) and% H ₂ O ₂ were used.

(3) Preparation of composite catalyst ink for membrane electrode assembly

The polymer composite catalyst / water / isopropyl alcohol was mixed in a ratio of 1.3: 6: 6 and then placed in a bath maintained at 4 ° C., followed by a homogenizer at 10,000 RPM for 2 hours. Stirred. The prepared catalyst ink was aged for 24 hours and used after sonication for 10 minutes before coating.

(4) Preparation of membrane-electrode assembly

A 25 cm ² size MEA was prepared by the transfer method. The composite catalyst ink was applied to the Teflon transfer film so that the platinum amount was 0.2 mg / cm ² , and thermocompression-transferred (130 ° C., 1.5 ton, 8 minutes) was applied to the electrolyte membrane (Dupont, NRE212).

(5) Fastening and evaluation of unit cell

End plate / Mono-polar plate / gas diffusion layer / gasket / membrane-electrode assembly / gasket / gas diffusion layer / Mono-polar plate / End plate. Gas diffusion layer was used SGL 10BC, gasket Teflon sheet (280μm), Mono-polar plate and End plate Electrochem, 25 cm ² Single Cell was used. The tightening torque to be fastened was fixed at 100 kgf · cm. Manufactured unit cell is gas supply window, humidifier. After being connected to a heater and an electronic load (pro-digit company), hydrogen and air were supplied to 0.5 SLM and 1.6 SLM, respectively, and the activation step was carried out by the constant voltage circulation method (1 V to 0.4 V, step 0.05 V). After the completion of the activation step, the current-voltage characteristics were measured while maintaining the equivalent ratio of hydrogen and air at 1.2: 2.

Comparative Example 1

(1) Preparation of Pt / C Catalyst

 "Method for Producing Electrochemical Catalyst for Polymer Electrolyte Fuel Cell" A 30wt% Pt / C catalyst was prepared using the conventional method prepared according to Korean Patent Application No. 2006-0083224.

2 g of a Vulcan XC 72R carrier was added to 500 mL of solvent (water: methanol (V / V) = 4: 1) and dispersed for 3 hours while simultaneously operating high power ultrasound and agitator. In a separate reactor, chloroplatinate (H ₂ PtCl ₆ · 6H ₂ O) was added to 500 mL of solvent (water: methanol (V / V) = 4: 1) so that the weight ratio of carbon to platinum was 7: 3. The solution was prepared by stirring. The two solutions are mixed and stirred for another hour. In a separate 30 L reactor, 4 L of solution (water: methanol (V / V) = 4: 1) was maintained at 85 ° C., and the two mixed liquids were added and reacted for 30 minutes. After the reaction, it is cooled, filtered and washed with sufficient water. The washed catalyst was then dried in a 100 ° C. vacuum oven for at least 12 hours to obtain a 42 wt% Pt / C platinum catalyst.

(2) catalyst evaluation

It carried out by the same method as Example.

(3) Preparation of Pt / C catalyst ink for membrane electrode assembly

Pt / C catalyst / water / isopropylalcohol / ionomer (5 wt% Nafion solution) was mixed in a ratio of 1: 6: 6: 6, then placed in a bath maintained at 4 ° C., and then homogenized for 2 hours. Stir at 10,000 RPM using a Niger. The prepared catalyst ink is aged for 24 hours and used after sonication for 10 minutes before coating.

Since the manufacturing method was carried out by the same method as in Example.

Comparative Example 2

Platinum nanoparticles were prepared in the same manner as in Example and prepared on a carbon carrier. Unlike the examples, Pt / C catalyst without ionomer was prepared.

0.5 g of platinum chloride (PtCl ₄ , Kojima, 99.9%) was dissolved in 100 ml of EG (Ethylene Glycol, Junsei, 98%) for 1 hour, and then titrated with NaOH (98%) so that the solution had a pH of 11. The titrated solution was rapidly heated to 30 ° C. within 30 minutes to reflux for 3 hours to prepare a platinum nanoparticle dispersion in which uniform platinum nanoparticles (average particle diameter 2 nm) were formed. Stir at room temperature for 3 hours until the temperature of the dispersion is cooled to room temperature. Thereafter, the carbon carrier Vulcan XC 72R was added so that the weight ratio of carbon to platinum was 7: 3, followed by stirring for 24 hours. The supported catalyst was obtained in the same manner as the comparative example by filtration, washing, and drying to obtain a 30 wt% Pt / C platinum catalyst.

Thereafter, the manufacturing process and evaluation were performed by the same method as in Comparative Example 1.

The catalyst prepared according to Example 2 and Comparative Example 2 was prepared by Comparative Example 2 of the polymer electrolyte composite catalyst prepared according to Example 2 by scanning electron microscope and EM (Element Mapping) analysis. Unlike the catalyst, it was confirmed that Nafion ionomer was uniformly distributed.

In addition, a Rotating Disk Electrode (RDE) analysis was performed to evaluate the electrochemical activity, and the results are shown in FIGS. 4 to 6. As shown in the CV (Cyclic Voltammetry) result of FIG. 4, it was confirmed that the active surface area of the composite catalyst prepared by the example was relatively superior to the catalyst prepared by the comparative example. LSV (Linear Sweep Voltage) of Figure 5 is to measure the activity of the oxygen electrode can be seen that the generated current value of the polymer electrolyte composite catalyst prepared in Example under the same voltage is the largest, which is the current generated by the oxygen reduction reaction Means the amount of and is proportional to the electrochemical activity of the catalyst. Oxygen Reduction Rate (ORR) reaction activity was also excellent. 6, H ₂ O ₂ % is a measure of the amount of unreacted oxygen, which is related to the amount of H ₂ O ₂ generated at the cathode side when the membrane-electrode assembly is applied. . In more detail, the oxygen reduction reaction (ORR) at the cathode is carried out by several reactions, in which oxygen is adsorbed on the electrode surface and receives electrons and is reduced. Hydrogen peroxide (H ₂ O ₂ ) and receives four electrons become water (H ₂ O). Hydrogen peroxide also receives electrons and becomes water. The ideal oxygen reduction reaction in a fuel cell is that oxygen receives four electrons and becomes water, and the generated hydrogen peroxide not only causes the efficiency of the fuel cell, but also the hydrogen peroxide is very strong such as HO, O ₂ , HO _2. The formation of radicals has a fatal effect on the operation of fuel cells, leading to reduced durability. It was confirmed from FIG. 6 that the H ₂ O ₂ generation amount was significantly lower in the polymer electrolyte composite catalyst prepared as in the embodiment of the present patent, which greatly improves the durability of the fuel cell as described above.

Electrochemical properties of the membrane-electrode assembly were shown in FIG. 7. As a result of the voltage-current characteristic measurement, the initial performance value of the composite catalyst according to the present invention was 600 mA@0.6V, and it was confirmed that the equivalent value of the catalyst according to the comparative example was 550 mA@0.6V or more.

1 is a manufacturing process chart of an ionomer-attached polymer electrolyte composite catalyst according to the present invention.

Figure 2 is a schematic diagram of a polymer electrolyte composite catalyst with an ionomer prepared according to an embodiment of the present invention.

Figure 3 is a scanning electron micrograph and EM (element mapping) analysis of the ionomer-attached polymer electrolyte composite catalyst (a) and the catalyst (b) of Comparative Example 2 without the ionomer prepared according to an embodiment of the present invention The results are shown.

Figure 4 is a graph showing the results of measuring the CV (Cyclic Voltammetry) of the ionomer-attached polymer electrolyte composite catalyst prepared according to the present invention.

FIG. 5 is a graph showing LSV (Linear Sweeping Voltammetry) measurement results of an ionomer-attached polymer electrolyte composite catalyst prepared according to the present invention.

Figure 6 is a graph showing the residual hydrogen peroxide (H ₂ O ₂ ) measurement results of the ionomer-attached polymer electrolyte composite catalyst prepared according to the present invention.

7 is a graph showing the current-voltage characteristic results of the membrane-electrode assembly prepared from the polymer composite catalyst prepared according to the present invention.

Claims (17)

a) reducing the metal precursor of the metal precursor solution to prepare a metal nanoparticle dispersion; b) mixing the metal nanoparticle dispersion and ionomer solution to prepare a mixed solution; c) mixing the carbon carrier with the mixed solution to form a metal-ionomer-carbon composite on which metal nanoparticles and ionomers are supported; Method for producing a polymer electrolyte composite catalyst comprising a. The method of claim 1, The solution of step a) comprises a solvent having at least one functional group selected from a hydroxyl group (OH), an aldehyde group (COH), or a carboxy group (COOH). The method of claim 2, Said solvent is glycolic acid, glyoxal, oxalic acid, acetaldehyde, ethylene glycol or a mixture thereof. The method of claim 1, The metal precursor is a metal chloride, a metal hydrochloride, a metal acetylacetone compound, a metal ammonium salt, a metal bromide or a mixture thereof and the metal is Pt, Pd, Os, Ir, Ru, Co, Fe, Mo, W, Cr, and Method for producing a polymer electrolyte composite catalyst, characterized in that at least one selected from Ni. The method of claim 1, The carbon support is a method for producing a polymer electrolyte composite catalyst, characterized in that the porous carbon material selected from carbon black, carbon nanotubes, carbon fiber, or fullerene. The method of claim 2, Method for producing a polymer electrolyte composite catalyst, characterized in that the weight ratio (A: B) of the metal precursor (A) and the solvent (B) is 1: 1 to 200. The method of claim 1, The b) weight ratio (C: D) of the metal nanoparticles (C) and the ionomer (D) in the mixed solution is 1: 0.1 ~ 10 method for producing a polymer electrolyte composite catalyst. The method of claim 1, Method for producing a polymer electrolyte composite catalyst, characterized in that the weight ratio (E: C + D) of the carbon carrier (E) to the total weight (C + D) of the metal nanoparticles and the ionomer is 1: 0.01 to 0.9. The method of claim 8, The weight ratio (C + E: D) of the ionomer (D) to the sum (C + E) of the metal nanoparticles and the carbon carrier is 1: 0.2 to 1: 0.5, wherein the polymer electrolyte composite catalyst is prepared. . The method of claim 1, Reduction of the step a) is a method for producing a polymer electrolyte composite catalyst, characterized in that it is carried out by reflux for 30 minutes to 2 hours after adjusting the pH of the metal precursor solution to 7 ~ 14. The method of claim 1, The method of producing a polymer electrolyte composite catalyst, characterized in that the step of aging the metal nanoparticle dispersion at room temperature after reduction in step a). The method of claim 1, And c) washing the metal-ionomer-carbon composite with a mixture of water and alcohol after step c). The method of claim 1 A method for producing a polymer electrolyte composite catalyst, wherein the size of the metal nanoparticles supported on the metal-ionomer-carbon composite is 1 to 10 nm. In the polymer electrolyte-catalyst composite in which metal nanoparticles and ionomers are supported on a carbon carrier, The size of the metal nanoparticles is 1 to 10 nm, the weight ratio (C: D) of the metal nanoparticles (C) and the ionomer (D) is 1: 0.1 to 10, and the total weight of the metal nanoparticles and the ionomer (C + D) The weight ratio (C + D: E) of the carbon support (E) is 1: 0.01 to 0.9, and the metal nanoparticle dispersion prepared by reducing the metal precursor of the metal precursor solution and the ionomer solution were mixed to prepare a mixed solution. After the polymer electrolyte composite catalyst, characterized in that the mixture is prepared by mixing the carbon carrier. A catalyst ink comprising the polymer electrolyte composite catalyst according to claim 14. A membrane-electrode assembly comprising the polymer electrolyte composite catalyst according to claim 14. A fuel cell comprising the membrane-electrode assembly according to claim 16.

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