KR20170072539A - Polymer electrolyte membrane for fuel cell, membrane-electrode assembly for fuel cell including same, and fuel cell system including same - Google Patents

Abstract

The cathode catalyst for a fuel cell includes an active metal including Pt, metals M and S, and has a nano-rod shape.

Description

TECHNICAL FIELD The present invention relates to a cathode catalyst for a fuel cell, a membrane-electrode assembly for a fuel cell including the fuel cell, and a fuel cell system including the same. BACKGROUND ART [0002]

A cathode catalyst for a fuel cell, a membrane-electrode assembly for a fuel cell including the cathode catalyst, and a fuel cell system including the same.

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

This fuel cell is a clean energy source that can replace fossil energy and has advantages of high output density and energy conversion efficiency. It can be used for pollution-free automobiles, household power generation systems, mobile communication equipment, medical equipment, military equipment, And can be widely used in the field of electronic devices. In order to commercialize such a fuel cell, development of a cathode catalyst excellent in oxygen reduction reaction and durability is required.

One embodiment is to provide a cathode catalyst for a fuel cell excellent in an oxygen reduction reaction.

Another embodiment is to provide a membrane-electrode assembly for a fuel cell comprising the cathode catalyst.

Another embodiment of the present invention is to provide a fuel cell system including the membrane-electrode assembly.

One embodiment provides a cathode catalyst for a fuel cell comprising an active metal comprising Pt, metals M and S and having a nanorod form.

The cathode catalyst may be represented by the following formula (1).

[Formula 1]

Pt-M _a -S _b

(Wherein 0? A < 1, 0? B < 1,

M is Co, Fe, Ni, Cu or a combination thereof)

The height (c) and width (d) of the nano-rod may have the relationship of the following formula (2).

[Formula 2]

1.5? C / d < 6

The cathode catalyst may be one in which the active metal is supported on a carrier. At this time, the average particle size of the active metal may be 2 nm to 10 nm. The amount of the active metal supported on the support may be 10 wt% to 70 wt%.

The cathode catalyst may further comprise a Pt shell surrounding the active metal.

Another embodiment of the present invention includes a cathode electrode comprising the cathode catalyst; An anode electrode including an anode catalyst; And a polymer electrolyte membrane positioned between the cathode electrode and the anode electrode.

In another embodiment of the present invention, there is provided a membrane-electrode assembly comprising: a membrane-electrode assembly; and a separator disposed on both sides of the membrane-electrode assembly, Generating part; A fuel supply unit for supplying the fuel to the electricity generation unit, and an oxidant supply unit for supplying the oxidant to the electricity generation unit.

The details of other embodiments are included in the detailed description below.

By applying the polymer electrolyte membrane for a fuel cell, a fuel cell membrane-electrode assembly having high performance and long life characteristics under high temperature and low humidity conditions can be realized.

1 illustrates a cathode catalyst structure for a fuel cell according to one embodiment.
2 is a schematic view showing a membrane-electrode assembly (MEA) for a fuel cell according to one embodiment.
3 is a schematic diagram of a fuel cell system according to one embodiment.
4 is an XRD measurement graph of a cathode catalyst for fuel cells manufactured according to Examples 1 and 2 and Comparative Example 1. Fig.
5 is a TEM photograph of a cathode catalyst for a fuel cell manufactured according to Example 1. Fig.
6 is a TEM photograph of a cathode catalyst for a fuel cell manufactured according to Example 2. Fig.
7 is a TEM-EDX photograph of a cathode catalyst for a fuel cell prepared according to Example 1
8 is a TEM photograph of a cathode catalyst for a fuel cell manufactured according to Comparative Example 1. Fig.
FIG. 9 is a graph illustrating the catalytic activity of a fuel cell including the cathode catalyst for fuel cells manufactured according to Examples 1 and 2 and Comparative Example 1. FIG.
10 is a graph showing the current density of a fuel cell including a cathode catalyst for a fuel cell manufactured according to Examples 1 and 2 and Comparative Example 1, measured.
11 is a partially enlarged view of Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

It is to be understood that where a layer, film, region, plate, or the like is referred to as being "on" another portion, unless stated otherwise in this specification, .

One embodiment provides a cathode catalyst for a fuel cell comprising an active metal comprising Pt, metals M and S and having a nanorod form.

The active metal may be represented by the following formula (1).

Pt-M _a -S _b

(Wherein 0? A < 1, 0? B < 1,

M is Co, Fe, Ni, Cu or a combination thereof)

The active metal has a nano-rod shape, and the nano-rod has a height (c) and a width (d), as shown in Fig. In the nano-rods, the height refers to the length of the long side in one direction, and the width means the short side length.

In one embodiment of the present invention, the height (c) and the width (d) of the nanorod may have a relationship expressed by the following equation (2).

[Formula 2]

1.5? C / d < 6

When the relation between the height (c) and the width (d) of the nano rod corresponds to the above formula 2, there is an advantage that the activity of the oxygen reduction reaction can be increased by developing the (111) .

The height c may be 3 nm? C <6 nm, and the width d may be 1 nm? D <12 nm, as the height c and the width d are in the above relationship. The width d may be 2 nm? D <12 nm.

In one embodiment of the present invention, when the active metal has such a nano-rod shape, the terminal crystal plane of the nano-rod may have a (111) single-crystalline structure, (111) plane is most developed, and the oxygen reduction reaction can be further improved.

Particularly, when the ternary alloy catalyst has a nano-rod form, the active metal containing Pt, the metals M and S in the formula 1 of the above formula is obtained by alloying M, which is a transition metal, in the platinum metal, And the oxygen reduction reaction of the catalyst can be increased. Further, the nano rod can develop the activity of the catalyst by developing platinum (111 plane) rich in electrons.

FIG. 1 shows a nano-rod shape of a catalyst according to an embodiment and schematically shows how the alloy of Formula 1 exists in a nano-rod. That is, as shown in Fig. 1, it can be seen that the metals M and S mainly exist inside and Pt mainly exists outside.

The cathode catalyst may be one in which the active metal is supported on a carrier. As the carrier, a carbon-based material such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nano-ball or activated carbon can be used. The carrier may be prepared by heat-treating the carbon-based material. Inorganic metal oxides such as alumina, silica, zirconia and titania, and carbide-based polymers such as FeC ₃ , CoC ₃ , MoC ₃ and SiC, polypyrrole and polyamide may also be used as the carrier.

The specific surface area of the support may be from 50 m ² / g to 1200 m ² / g. When the specific surface area of the carrier is within this range, a high concentration of active metal can be uniformly carried in the carrier.

At this time, the average particle size of the active metal may be 2 nm to 10 nm. When the average particle size of the active metal is less than 2 nm, the crystal surface of platinum does not grow and the catalytic activity decreases. When the average particle size exceeds 10 nm, the specific surface area of the catalyst is small, . The amount of the active metal supported on the support may be 10 wt% to 70 wt%. When the loading amount of the active metal on the carrier is less than 10% by weight, there is a problem that the catalyst is buried in the micropores in the carrier to lower the catalyst utilization rate. When the loading amount exceeds 70% by weight, There is a problem in that it is lowered.

The cathode catalyst may further comprise a Pt shell surrounding the active metal. As the cathode catalyst further includes the Pt shell, the oxygen reduction reaction can be further increased and the durability can be further increased.

The cathode catalyst for a fuel cell having such a configuration is rich in electrons on the surface, and the (111) face of Pt is abundant, which can increase the oxygen reduction reaction.

The cathode catalyst for a fuel cell may be manufactured by the following process.

A metal salt solution is prepared by adding a Pt-containing metal salt and a metal M-containing metal salt to a solvent.

Examples of the Pt-containing metal salt include H ₂ PtCl ₆揃 6H ₂ O, H ₂ PtCl ₄ , Pt (NH ₃ ) ₄ Cl ₂ , PtCl ₂ , Pt (CN) ₂ , -Containing metal salts include FeCl ₃ .6H ₂ O, FeSO ₄ .xH ₂ O, Fe (NO ₃ ) ₃ .9H ₂ O, CoCl ₂ .6H ₂ O, CoSO ₄ .7H ₂ O, Co (NO ₃ ) ₂ · 6H ₂ O, CuCl ₂ , CuSO ₄ · 5H ₂ O, NiCl ₂ · 6H ₂ O, or a combination thereof.

As the solvent, ethylene glycol, diethylene glycol, triethylene glycol, methanol, ethanol, isopropyl alcohol or a combination thereof may be used. In one embodiment, ethylene glycol, diethylene glycol, triethylene glycol may be used.

The metal salts may be added to one solvent, or may be added to each solvent, and then the obtained solution may be mixed.

In the case of preparing a catalyst in which an active metal is supported on a carrier, a step of adding a carrier to the solvent may be carried out first. In addition, the carrier may be added to a separate solvent to prepare a carrier liquid, and then the resulting mixture may be mixed with a solvent containing the Pt-containing metal salt and the metal M-containing metal salt.

Sodium citrate may further be added to the obtained metal salt solution .

The S-containing raw material is then added to the resulting mixture. At this time, a reducing agent may be further added to increase the reducing power of the mixture. As the reducing agent, NaH ₂ PO ₂ can be used, but it is not limited thereto . The reducing agent may be used in the form of an aqueous solution.

As the S-containing raw material, (NH ₂ ) ₂ SC, Na ₂ S, CH ₃ SH or a combination thereof may be used. In such an S-containing raw material, S is bonded to the metal M and serves to control the shape of the product so that the form of the product becomes rod-shaped. The S-containing raw material may be added to a separate solvent and then added to the mixture. At this time, water can be used as a solvent.

At this time, the content of the Pt-containing metal salt, the metal M-containing metal salt and the S-containing starting material can be appropriately controlled so as to obtain an active metal having the composition of the above formula (1).

The resulting mixture is then reduced. This reduction process can be performed by a hydrothermal synthesis process. The mixture may be applied to an autoclave type microwave reactor to irradiate microwave electromagnetic waves, preferably ultra-high frequency (UHF), but the heat source of the reduction process is not limited to microwave electromagnetic waves. The microwave electromagnetic waves are preferably irradiated in a range of about 400 W to about 1600 W, and the temperature range of the mixture is preferably controlled at a temperature of about 100 캜 to about 300 캜, for example, about 200 캜 to about 250 캜. The degree of reduction of the metal salts can be increased when the temperature is adjusted to the above range.

The reduction product obtained is subjected to a typical process of filtration, washing and drying, and then subjected to heat treatment and acid treatment to produce a cathode catalyst for a fuel cell.

The heat treatment may be performed at 150 to 750 ° C for 0.5 to 2.5 hours. The acid treatment may be carried out using hydrochloric acid, nitric acid, sulfuric acid or a combination thereof, and may be carried out at 60 to 190 ° C.

Hereinafter, a membrane-electrode assembly for a fuel cell according to another embodiment will be described with reference to Fig.

2 is a schematic view showing a membrane-electrode assembly (MEA) for a fuel cell according to one embodiment.

2, the fuel cell membrane-electrode assembly 20 includes a polymer electrolyte membrane 25, a cathode electrode 21 located on one side of the polymer electrolyte membrane 25, And an anode electrode 22 located on the other surface.

The polymer electrolyte membrane 25 is as described above.

The cathode electrode 21 includes an electrode substrate and a cathode catalyst layer. Wherein the cathode catalyst layer comprises the catalyst for the cathode according to one embodiment.

The anode 22 may include an electrode substrate and an anode catalyst layer. The anode catalyst layer may be formed of at least one of platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Zn), or a combination of these. The catalyst may be used alone or may be supported on a carrier. The carrier may be a carbonaceous material such as graphite, denka black, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs or activated carbon, or may be alumina, silica, zirconia, titania Or the like may be used.

In addition to the catalyst, the catalyst layer may further include an ionomer for improving adhesion of the catalyst layer and transferring hydrogen ions.

The ionomer may be a polymer resin having hydrogen ion conductivity, specifically, a polymer resin having at least one cation-exchange group selected from a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, Can be used. More specifically, examples of the polymer include fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone polymer, poly Ether-ether ketone-based polymer, and polyphenylquinoxaline-based polymer may be used. More specifically, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid group, sulfated polyether ketone, aryl ketone, poly 2,2'-m-phenylene) -5,5'-bibenzimidazole] and poly (2,5-benzimidazole [ ) May be used.

The polymeric resin having hydrogen ion conductivity may further include a microporous layer on the electrode substrate to improve the diffusion effect. The microporous layer may include a conductive powder having a small particle diameter, for example, carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene or carbon nanotube. The microporous layer may be prepared by coating a composition comprising conductive powder, a binder resin and a solvent on the gas diffusion layer. As the binder resin, H may be replaced with Na, K, Li, Cs or tetrabutylammonium in polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, or a cation exchanger at the cell side chain terminal. In the case of replacing H with Na in the ion exchange group at the side chain terminal, NaOH is substituted in the preparation of the catalyst composition and tetrabutylammonium hydroxide is used in the case of replacing with tetrabutylammonium, and K, Li or Cs is also substituted with a suitable compound . &Lt; / RTI &gt; Since this substitution method is well known in the art, a detailed description thereof will be omitted in this specification.

The ionomer may be used singly or in the form of a mixture, and may optionally be used together with a nonconductive compound for the purpose of further improving the adhesion with the polymer electrolyte membrane. The amount of the nonconductive compound to be used is preferably adjusted to suit the intended use.

Examples of the nonconductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoro (PVdF-HFP), dodecyltrimethoxysilane (DMSO), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer At least one selected from silbenzenesulfonic acid and sorbitol can be used.

The ionomer may be contained in an amount of 15% by weight to 50% by weight with respect to the total amount of the catalyst layer, for example, 20% by weight to 40% by weight. When the ionomer is contained within the above range, the adhesion of the catalyst layer is improved and the hydrogen ion transfer efficiency is increased.

The electrode base plays a role of supporting the electrode, diffuses the reaction source into the catalyst layer to make the reaction source easily accessible to the catalyst layer, and is also referred to as a gas diffusion layer.

As the electrode substrate, a conductive substrate is used. For example, a carbon paper, a carbon cloth, a carbon felt or a metal cloth (a porous film composed of a metal cloth in a fiber state or the like) A metalized polymer fiber is formed on the surface of a cloth formed of polymer fibers), but the present invention is not limited thereto.

The electrode substrate may be a water repellent treated with a fluorine-based resin in order to prevent the gas diffusion efficiency from being lowered by water generated when the fuel cell is driven. As the fluororesin, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, fluoroethylene polymer and the like can be used.

And gaseous toluene acetate may be used. Examples of the solvent include alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol and butyl alcohol, water, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone Can be used. The coating process may be performed by a screen printing method, a spray coating method, a doctor blade coating method, or the like, depending on the viscosity of the composition, but is not limited thereto.

Another embodiment provides a fuel cell system including at least one electricity generating portion, a fuel supplying portion, and an oxidizing agent supplying portion.

The electricity generating unit includes a membrane-electrode assembly and a separator (also referred to as a bipolar plate) according to an embodiment. The electricity generating unit generates electricity through the oxidation reaction of the fuel and the reduction reaction of the oxidant.

The fuel supply unit supplies fuel to the electricity generation unit, and the oxidant supply unit supplies an oxidant such as oxygen or air to the electricity generation unit.

In one embodiment, the fuel may include hydrogen or hydrocarbon fuel in a gaseous or liquid state. Representative examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol or natural gas.

A schematic structure of a fuel cell system according to one embodiment is shown in FIG. 3 and will be described in more detail with reference to FIG. The structure shown in FIG. 3 shows a system for supplying the fuel and the oxidizer to the electricity generating unit by using a pump. However, the fuel cell system is not limited to this structure, and the structure of the fuel cell system using the pump- It is a matter of course.

The fuel cell system 1 according to an embodiment includes at least one electricity generating portion 3 for generating electric energy through oxidation reaction of a fuel and oxidizing agent, a fuel supply portion 5 for supplying the fuel, And an oxidant supply part (7) for supplying an oxidant to the electricity generation part (3).

The fuel supply unit 5 for supplying the fuel may include a fuel tank 9 for storing the fuel and a fuel pump 11 connected to the fuel tank 9. The fuel pump 11 functions to discharge the fuel stored in the fuel tank 9 by a predetermined pumping force.

The oxidant supply part (7) for supplying the oxidant to the electricity generating part (3) is provided with at least one oxidant pump (13) for sucking the oxidant with a predetermined pumping power.

The electricity generating portion 3 is composed of a membrane-electrode assembly 17 for oxidizing and reducing the fuel and oxidizing agent, and a separator 19, 19 'for supplying fuel and oxidant to both sides of the membrane- , And at least one such electricity generating part 3 is gathered to constitute the stack 15.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

(Example 1)

0.2 g of carbon obtained by heat-treating a carbon-based carrier (Ketjen black 300J (Mitsubishi Chemical's EC-300J) (specific surface area 800 m ² / g) at 2250 ° C, specific surface area 160 m ² / g) 107.6 g in an ultrasonic wave for 30 minutes to prepare a carbon-based carrier dispersion.

H ₂ PtCl ₆ O ₆ H ₂ O (Solvent: ethylene glycol, concentration: 8% by weight) (the content of Pt in H ₂ PtCl ₆ 6H ₂ O is 37.7% by weight) 4.419 g, FeCl _{^3. 6H 2 O (FeCl 3 6H 2} O content of the Fe is being 20.6% by ^weight) solution (solvent: ethylene glycol, concentration: 8 wt%) 2.310g, citrine sodium (sodium citrate, molecular weight 294.1) solution (solvent: Distilled water, concentration: 30 wt%) were mixed to prepare a metal solution.

The metal solution was added to the carbon-based carrier dispersion, followed by stirring for about 30 minutes. Then, to adjust the reducing power and shape of the mixture, 0.915 g of a 2 wt.% NaH ₂ PO ₂ aqueous solution and 0.669 g of a (NH ₂ ) ₂ SC aqueous solution of 2 wt% concentration were added to the obtained stirring product and mixed.

The obtained mixed solution was put into a Teflon sealed autoclave reactor and irradiated with microwave (power: 1600 W) for about 60 minutes to raise the temperature of the autoclave reactor to about 250 ° C to perform a reduction reaction.

When the reaction was completed, the reaction product was filtered, washed and dried, and then the obtained product was heat-treated at 300 ° C for 5 hours. Then, a heat treatment product by using a 1M HNO ₃ 200g treatment at 90 ℃ acid for 30 minutes to elute the Fe ²⁺ and / or Fe ³⁺ ion.

The resultant was filtered, washed and dried again to prepare an electrode catalyst PtFeS / C having a nanorod shape.

The height (c) of the prepared nanorod catalyst was 3 nm, and the width (d) was 2 nm. Therefore, c / d was 1.5.

(Example 2)

(NH ₂ ) ₂ SC was changed to 1.339 g in the same manner as in Example 1 to prepare a nano rod type cathode catalyst. The height (c) of the prepared nanorod catalyst was 4, and the width (d) was 1.5. The ratio c / d was 2.67.

(Comparative Example 1)

A spherical cathode catalyst was prepared in the same manner as in Example 1 except that the amount of (NH ₂ ) ₂ SC was changed to 0.167 g. The height (c) of the prepared nanorod catalyst was 3.2 and the width (d) was 3.2. Therefore, c / d was 1.

* XRD analysis

The X-ray diffraction peak intensities of the cathode catalysts prepared according to Examples 1 and 2 and Comparative Example 1 were measured using a CuK? Line. The results are shown in FIG. 4, and the (111) And the crystalline size (catalyst size) were measured and the results are shown in Table 1.

The peak position of the (111) plane of Pt The crystallization size of the measured catalyst
(crystalline size, nm) Comparative Example 1 40.3439 DEG 3.18 Example 1 40.6125 [deg.] 3.50 Example 2 40.5428 ° 3.62

As shown in Table 1, the peaks of the (111) plane of Pt appear at 2? = 39.8 占 On the other hand, the Pt-Fe alloys were observed in both of Examples 1 and 2 and Comparative Example 1, Able to know.

4, the arrow indicates the peak position of the (111) plane of pure Pt, and its value is about 2? = 39.8 °. The increase in the peak position value of the (111) plane of Pt means that the Fe atoms enter the lattice of Pt more. Therefore, as shown in Fig. 4, the peak positions of the (111) planes of Examples 1 and 2 were found to be higher than those of Comparative Example 1, so that the catalysts of Examples 1 and 2 were more alloyed than the catalyst of Comparative Example 1 And is the same as the result of Table 1 above.

In addition, as shown in Table 1, the crystallization size of the catalyst prepared according to Examples 1 and 2 was larger than that of Comparative Example 1, which means that the (111) plane of Pt was developed more greatly. From these results, it can be seen that the catalysts of Examples 1 and 2 can exhibit a better oxygen reduction reaction.

* ICP (Inductively Coupled Plasma) analysis

The results of ICP analysis (inductively coupled plasma, ICPS-8100, SHIMADZU / RF source, 27.12 MHz / sample uptake rate 0.8 mL / min) of the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 2 .

Pt (% by weight) Fe (% by weight) S (% by weight) Comparative Example 1 35 2.9 0.09 Example 1 35 2.9 0.11 Example 2 34 2.8 0.11

As shown in Table 2, it can be seen that the batteries manufactured according to Examples 1 to 2 and Comparative Example 1 are composed of Pt, Fe and S compositions.

* TEM  Photos and TEM - EDX  Analytical measurement

TEM photographs of the cathode catalysts prepared according to Examples 1, 2 and Comparative Example 1 are shown in FIGS. 5, 6 and 8, respectively. The TEM-EDX mapping of the cathode catalyst prepared according to Example 1 is shown in FIG.

As shown in FIGS. 5 and 6, the cathode catalyst prepared according to Examples 1 and 2 is in the form of a nano rod, whereas, as shown in FIG. 8, the cathode catalyst prepared according to Comparative Example 1 is spherical .

Further, as shown in Fig. 7, the elemental structure of one catalyst particle of Example 1 shows that an element of Pt, Fe, and S is formed of an alloy in the inside, but the surface of the catalyst is made of a Pt shell have.

* Oxygen Reduction Reaction (ORR) Experiment

6 μl of a mixture of 0.03 g of the cathode catalyst prepared in Example 1 and 5 ml of isopropyl alcohol was dropped into a glassy carbon rotary electrode using a micropipette, and the resultant was dried and dissolved in isopropyl alcohol / water 1: 1) was dropwise added in an amount of 7 μl into the electrode dropwise added with the catalyst, and the electrode was prepared by drying in the same process.

The working electrode was mounted on a RDE (rotating disk electrode) apparatus, platinum was used as a counter electrode, and Ag / AgCl (KCl _sat ) was used as a reference electrode. The prepared three-phase electrode was placed in a 0.1 M HClO ₄ electrolyte and bubbled with nitrogen for 30 minutes to remove residual oxygen in the electrolyte. The catalyst is activated by cycling 100 times at 100 mV / s in a range of 0.02 to 1 V (vs. NHE) using a constant potential electrolytic apparatus and a constant current electrolysis apparatus (potentiostat / galvanostat).

(0 to 1.0 V vs. NHE) at which the material limit current occurs at an open circuit voltage (OCV) while rotating the carbon electrode after bubbling the electrolyte into the electrolyte to saturate oxygen in the electrolyte. The ORR current was recorded in the negative direction.

The ORR current was recorded using the electrode catalysts prepared according to Example 2 and Comparative Example 1, respectively, instead of the cathode catalyst prepared according to Example 1, and the results are shown in FIG. 9 .

As shown in FIG. 9, the catalysts of Examples 1 and 2 exhibited higher current than the catalyst of Comparative Example 1 at the same voltage, so that the catalysts of Examples 1 and 2 were found to be superior in catalytic activity to those of Comparative Example 1 .

Among the results shown in Fig. 9, the current value at 0.9 V is shown in Table 3 as the mass activity (A / Pt g) value.

Weight active (A / Pt g) Comparative Example 1 6.77 Example 1 16.11 Example 2 12.85

As shown in the above Table 3, it can be seen that the fuel cell including the cathode catalyst prepared according to Examples 1 and 2 has a larger activity value than the fuel cell comprising the cathode catalyst prepared according to Comparative Example 1 .

* Fuel cell performance evaluation (single cell test)

A unit cell was prepared as described below using the cathode catalysts prepared according to Examples 1 and 2 and Comparative Example 1.

1.54 g of a 10 wt% Nafion solution (Asai Kasi, EW = 550) per 1 g of the catalyst and an appropriate amount of dipropyl ethylene glycol were mixed to prepare a cathode slurry. The cathode slurry was coated on a polyimide polymer-based film with a bar coater, and dried at a temperature ranging from room temperature to 60 ° C step by step, thereby preparing a cathode. The loading amount of the catalyst at the cathode was 0.18 mg / cm ^{2 on the} basis of Pt.

Separately, an anode was prepared using a 10 wt% Pt / C catalyst and the loading of the catalyst at the anode was about 0.02 mg / cm ² on a Pt basis.

A polymer electrolyte membrane (Asai Kasi, thickness 12 占 퐉, Nafion) was placed between the cathode and the anode and placed in an apparatus capable of controlling the temperature and the pressure, so that catalyst layers were formed on both sides of the polymer electrolyte membrane from the polymer base film, A catalyst coated membrane (CCM) method of transferring to an electrolyte membrane was performed, and a carbon paper having a microporous layer was adhered to the catalyst layer to prepare a membrane-electrode assembly.

Air was injected into the cathode of the membrane-electrode assembly and hydrogen was injected into the anode (relative humidity: 50%, 36.2 cc / min A, back press: 150 kPa) , 11.4 cc / min. A, operating pressure: 150 kPa) was evaluated at 90 DEG C for current density and power density. At this time, stoichiometry (amount of hydrogen gas supplied to anode / amount of air supplied to cathode / theoretical value for electrochemical reaction, λ) was adjusted to 1.2 / 1.5.

Among the measured results, the current density results are shown in Fig. In addition, a partially enlarged view of Fig. 10 is shown in Fig.

As shown in FIGS. 10 and 11, it can be seen that the current density of the fuel cell including the cathode catalyst prepared according to Examples 1 and 2 is higher than that of Comparative Example 1.

The results of the measured power density at 0.65 V are shown in Table 4 below.

Power density (mW / cm ² ) Comparative Example 1 0.845 Example 1 0.891 Example 2 0.882

As shown in Table 4, it can be seen that the output density of the fuel cell including the cathode catalyst prepared according to Examples 1 and 2 is superior to that of Comparative Example 1.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (9)

Pt, metals M and S, and has a nano-rod form
Cathode catalysts for fuel cells. The method according to claim 1,
Wherein the active metal is represented by the following formula (1).
Pt-M _a -S _b
(Wherein 0? A < 1, 0? B < 1,
M is Co, Fe, Ni, Cu or a combination thereof) The method according to claim 1,
And the height (c) and the width (d) of the nano rod have a relationship represented by the following formula (2).
[Formula 2]
1.5? C / d < 6 The method according to claim 1,
Wherein the cathode catalyst comprises the active metal supported on a carrier. 5. The method of claim 4,
Wherein the average particle size of the active metal is from 2 nm to 10 nm. 5. The method of claim 4,
And the amount of the active metal supported on the carrier is 10 wt% to 70 wt%. The method according to claim 1,
Wherein the cathode catalyst further comprises a Pt shell surrounding the active metal. A cathode electrode comprising the cathode catalyst of any one of claims 1 to 7;
An anode electrode including an anode catalyst; And
A polymer electrolyte membrane positioned between the cathode electrode and the anode electrode;
Electrode assembly for a fuel cell. At least one electricity generating unit including a membrane-electrode assembly according to claim 8, and a separator positioned on both sides of the membrane-electrode assembly, for generating electricity through an oxidation reaction of the fuel and a reduction reaction of the oxidant;
A fuel supply unit for supplying the fuel to the electricity generation unit; And
An oxidant supply unit for supplying the oxidant to the electricity generating unit,
And a fuel cell system.

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