KR20200013994A - Catalyst composition for fuel cell, manufacturing method for same, membrane-electrode assembly and fuel cell - Google Patents

Abstract

The present invention relates to a membrane-electrode assembly, a fuel cell and a method of manufacturing the membrane-electrode assembly. A catalyst composition comprises an ionomer, a catalyst, and a mixed solvent, and enables formation of a thin catalyst layer.

Description

Catalyst composition for fuel cell, preparation method thereof, membrane-electrode assembly and fuel cell {CATALYST COMPOSITION FOR FUEL CELL, MANUFACTURING METHOD FOR SAME, MEMBRANE-ELECTRODE ASSEMBLY AND FUEL CELL}

The present specification relates to a catalyst composition for a fuel cell, a manufacturing method thereof, a membrane-electrode assembly, and a fuel cell.

The recent prediction of the depletion of existing energy resources such as oil and coal has led to the

There is a growing interest in energy that can be replaced. As one of such alternative energy, fuel cells have been particularly noticed for their advantages such as high efficiency, no pollutants such as NOx and SOx, and abundant fuel used.

A fuel cell is a power generation system that converts chemical reaction energy of fuel and oxidant into electrical energy. Hydrogen, hydrocarbons such as methanol, butane, and the like are typically used as fuel, and oxygen is used as the oxidant.

Fuel cells include polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), and solid oxide fuels. Batteries (SOFC) and the like.

Korean Patent Publication 10-2016-0139256 (published: December 7, 2016)

The present specification relates to a catalyst composition for a fuel cell, a manufacturing method thereof, a membrane-electrode assembly, and a fuel cell.

Herein is an ionomer;

catalyst; And

It provides a catalyst composition for a fuel cell comprising a mixed solvent containing a monohydric alcohol and a polyhydric alcohol in a mass ratio of 9: 1 to 5: 5.

In addition, the present specification comprises the steps of adding the ionomer to a mixed solvent containing a monohydric alcohol and a polyhydric alcohol in a mass ratio of 9: 1 to 5: 5;

Injecting a catalyst into the mixture of the mixed solvent and the ionomer; And

It provides a method for producing a catalyst composition for a fuel cell comprising the step of sonicating the mixture in which the catalyst is added.

In addition, the present specification is a membrane-electrode assembly including a cathode catalyst layer, an anode catalyst layer and an electrolyte membrane provided between the cathode catalyst layer and the anode catalyst layer,

At least one of the cathode catalyst layer and the anode catalyst layer provides a membrane-electrode assembly that is made of the catalyst composition for fuel cells described above.

In addition, the present disclosure provides a fuel cell including the membrane-electrode assembly described above.

The catalyst composition for a fuel cell according to an exemplary embodiment of the present specification has an effect of improving the utilization rate of the catalyst by preventing agglomeration of ionomers when forming the catalyst layer.

The catalyst composition for a fuel cell according to the exemplary embodiment of the present specification may form a thin catalyst layer.

The membrane-electrode assembly manufactured using the catalyst composition for fuel cell according to one embodiment of the present specification has excellent performance.

1 is a schematic diagram illustrating a principle of electricity generation of a fuel cell.
2 is a view schematically showing the structure of a membrane-electrode assembly.
3 is a view schematically showing an embodiment of a fuel cell.

Hereinafter, this specification is demonstrated in detail.

In the present specification, when a part "includes" a certain component, this means that, unless specifically stated otherwise, it may further include other components, not to exclude other components.

In this specification, "or" means the meaning of "and / or" when it includes any or all of them listed, unless otherwise defined.

In the present specification, "layer" means covering 70% or more of the area in which the layer exists. It means preferably covering at least 75%, more preferably at least 80%.

In this specification, the "thickness" of a layer means the shortest distance from the lower surface of the layer to the upper surface.

In the present specification, the "monohydric alcohol" means an alcohol in which the number of hydroxy groups (-OH groups) present in one molecule is one.

In the present specification, the "polyhydric alcohol" means an alcohol having two or more hydroxyl groups (-OH groups) present in one molecule. For example, the dihydric alcohol has two hydroxy groups present in one molecule, and the trihydric alcohol has three hydroxy groups present in one molecule.

In the present specification, "side-chain" refers to a group of atoms bonded to atoms included in the backbone of the ionomer, wherein the number of atoms in the side-chain is the length of the side chain. It can be expressed as. The length of the side branch chain is smaller than the length of the main chain.

(Catalyst composition for fuel cell)

The present specification provides a catalyst composition for a fuel cell.

Herein is an ionomer;

catalyst; And

It provides a catalyst composition for a fuel cell comprising a mixed solvent containing a monohydric alcohol and a polyhydric alcohol in a mass ratio of 9: 1 to 5: 5.

When the catalyst layer is formed using the catalyst composition for fuel cell, the active area of the catalyst is increased. This is because the ionomers contained in the composition are effectively prevented from agglomeration with each other when the mixed solvent of monohydric alcohol and polyhydric alcohol is used as a solvent. In addition, the ionomers do not agglomerate with each other to form a thin catalyst layer.

If the solvent contains only monohydric alcohol as in the prior art, there is a problem that the solubility of the ionomer is lowered to increase the crack of the catalyst layer and lower the utilization rate of the catalyst. On the other hand, in the case of the organic solvent such as polyhydric alcohol, there is an effect of increasing the solubility of the fluorine-based ionomer compared to the solvent having a low boiling point, such as conventional alcohol. However, when polyhydric alcohol is used alone, there is a problem in that the dispersibility of the catalyst is poor. In the present invention, while the solvent of the composition is a mixed solvent containing both monohydric alcohol and organic solvent, by adjusting the mass ratio of monohydric alcohol and organic solvent, it is possible to maintain the dispersibility of the catalyst and increase the solubility of the ionomer to improve the catalyst utilization The effect could be achieved.

On the other hand, in general, the ionomer included in the composition changes the particle size is dispersed in the catalyst layer according to the solubility of the solvent. When a solvent having a low solubility is used, ionomers may aggregate together, and when a solvent having a high solubility is used, there is a problem of thin and small dispersion.

The catalyst composition according to one embodiment of the present specification uses a solvent having specific physical properties as the type of the polyhydric alcohol, or when the mass ratio of the monohydric alcohol and the polyhydric alcohol is adjusted, the solubility described above is adjusted so that the ionomers aggregate together. Can be effectively prevented. In addition, by using a specific kind of ionomer, it is possible to effectively prevent the agglomeration of the ionomer by adjusting the content of the ionomer or the catalyst in the composition.

In one embodiment of the present specification, the monohydric alcohol may be one or two or more selected from the group consisting of methanol, ethanol, propanol and butanol.

In one embodiment of the present specification, the polyhydric alcohol is diethylene glycol (DEG), propylene glycol (propyleneglycol, PG), dipropylene glycol (DPG), 1,3-butylene glycol (1 , 4-butylene glycol) and dihydroterpineol (DHT), triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. The polyhydric alcohol has the effect of increasing the solubility of the ionomer. In particular, when the type of ionomer is a fluorine ionomer, the solubility of the fluorine ionomer is further increased. This can be confirmed by comparing the Examples and Comparative Examples.

In one embodiment of the present specification, the boiling point of the polyhydric alcohol may be 130 ° C or higher, preferably 130 ° C or higher and 300 ° C or lower, more preferably 150 ° C or higher and 250 ° C or lower. When satisfying the numerical range, when the catalyst composition for fuel cell is dried at a temperature lower than the temperature, the pore size may be evenly distributed without becoming too large.

In one embodiment of the present specification, the content of the mixed solvent is 50% by weight to 95% by weight, preferably 65% by weight to 95% by weight, more preferably based on the total weight of the catalyst composition for fuel cell. 75 wt% or more and 95 wt% or less. When the content of the solvent in the catalyst ink is 50% by weight or more, the viscosity of the catalyst ink is prevented from becoming too high, so that the dispersibility of the catalyst particles and the formation of the catalyst layer can be prevented. When the content of the solvent is 95% by weight or less, since the viscosity of the catalyst ink is prevented from being too low, the thickness of the catalyst layer is thin, thereby preventing the problem of repeating the coating several times.

In one embodiment of the present specification, the viscosity at 25 ° C. of the catalyst composition for a fuel cell may be 2.6 cPs or more and 100 cPs or less, preferably 10 cPs or more and 90 cPs or less, more preferably 15 cPs or more and 75 cPs or less. When the numerical range is satisfied, not only the coating property of the catalyst composition is improved but also the composition is easily stored.

The said viscosity can be measured by the method generally used in the field to which this technique belongs. For example, it measures at normal temperature (25 degreeC) using the spindle 18 using a Brookfield viscometer (made by Brook Field). At this time, the amount of the composition is suitably 6.5 to 10mL, and measure the stabilized value within 5 minutes to avoid prolonged exposure to light.

In one embodiment of the present specification, the ionomer serves to provide a passage for ions generated by the reaction between the fuel and the catalyst such as hydrogen or methanol to move to the electrolyte membrane.

In one embodiment of the present specification, the side chain of the ionomer includes a carbon atom or an oxygen atom, and the total sum of the number of carbon atoms and the number of oxygen atoms may be 2-10, or 2-6. In this case, the ionomer may have a short-side-chain, but when an ionomer having a short side-chain is used, there is an advantage in that a thin catalyst layer can be formed. Commercially available products of the ionomers having the short side branched chains include 3M ionomers, aquibions, and hyplons.

In one embodiment of the present specification, the ionomer may use a polymer having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups, and derivatives thereof in the side chain.

In one embodiment of the present specification, the ionomer may be a hydrocarbon-based polymer, a partially fluorine-based polymer or a fluorine-based polymer.

In one embodiment of the present specification, the ionomer is a fluorine-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polyphenylene sulfide-based polymer, polysulfone-based polymer, polyethersulfone-based polymer It may include at least one hydrogen ion conductive polymer selected from polyether ketone-based polymer, polyether-ether ketone-based polymer, or polyphenylquinoxaline-based polymer.

In one embodiment of the present specification, the ionomer is a fluorine-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polyphenylene sulfide-based polymer, polysulfone-based polymer, polyethersulfone-based polymer , A polyether ketone-based polymer, a polyether-etherketone-based polymer, and a polyphenylquinoxaline-based polymer.

In one embodiment of the present specification, the ionomer may be 0.01 wt% or more and 6 wt% or less, 0.05 or more and 5 or less, preferably 0.1 or more and 4 or less, based on the total weight of the catalyst composition for fuel cell. When the content of the ionomer is in the above range, the ionomer does not excessively cover the catalyst layer to facilitate the reaction between the catalyst and the fuel, but the ion transport passage in the catalyst layer is properly formed, so that the movement of ions may be most smooth.

According to one embodiment of the present specification, the catalyst may be a catalyst supported on the surface of the carbon support.

Examples of the carbon support include, but are not limited to, graphite (graphite), carbon black, acetylene black, denka black, cathodic black, activated carbon, mesoporous carbon, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon nano One, two or more mixtures selected from the group consisting of rings, carbon nanowires, fullerenes (C60) and super P may be used.

Examples of the metal include, but are not limited to, platinum, ruthenium, osmium, platinum / ruthenium alloy, platinum / osmium alloy, platinum / palladium alloy, platinum / M alloy (M is Ga, Ti, V, Cr, Mn, Fe , Transition metals of Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru, or a combination thereof, or a combination thereof. Specific examples of the catalyst, Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W , Pt / Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, Pt / Ru / Sn / W, or a combination thereof may be used.

According to one embodiment of the present specification, the catalyst may be platinum supported carbon (Pt / C) or platinum-ruthenium alloy supported carbon (PtRu / C), preferably platinum supported carbon (Pt / C). .

Here, the slash (/) inserted and written together means an alloy of the described metals. For example, Pt / Ru means an alloy of platinum (Pt) and ruthenium (Ru).

According to one embodiment of the present specification, the catalyst may be included in an amount of 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, and more preferably 5 wt%, based on the total weight of the catalyst composition. % To 15% by weight may be included. When the content of the catalyst in the catalyst composition is 1% by weight or more, the viscosity of the catalyst composition is prevented from being too low, so that the thickness of the catalyst layer is thin, thereby preventing the problem of repeating the coating several times. When the content of the catalyst is 20% by weight or less, since the viscosity of the catalyst composition is prevented from becoming too high, it is possible to prevent the lowering of the dispersibility of the catalyst particles and the uneven formation of the catalyst layer.

(Composition Production Method)

Herein is a step of injecting an ionomer into a mixed solvent comprising a monohydric alcohol and a polyhydric alcohol in a mass ratio of 9: 1 to 5: 5;

Injecting a catalyst into the mixture of the mixed solvent and the ionomer; And

It provides a method for producing a catalyst composition for a fuel cell comprising the step of sonicating the mixture in which the catalyst is added.

In one embodiment of the present specification, the sonicating is performed in a tip type or a bath type.

In the present specification, the ultrasonic treatment refers to the act of dispersing energy having a frequency of 20 kHz or more to the particles, the bath type (bath type) is a relatively low energy of a constant size, the tip type (tip type) It is possible to variably apply about 50 times higher energy than the bath type.

In general, ionomers are aggregated together by electrostatic attraction in a solvent to exist as aggregates having a particle diameter of 0.01 μm to 1 μm. Thus, unit particles formed by agglomeration of ionomers in a solvent are called ionomer clusters. When these are dispersed by sonication, in particular, the tip type or bath type sonication, most of the ionomer clusters have an average of 10 nm to 500 nm, preferably 10 nm to 300 nm. It is uniformly dispersed to have a particle size.

The tip ultrasonic treatment is not limited thereto, but may be performed for 10 to 30 minutes. The bath sonication may be performed for 20 to 120 minutes, preferably 30 to 60 minutes.

When the ultrasonication is performed within the above time range, it is possible to prevent the occurrence of local ionomer agglomeration. When performed in excess of the time range, the dispersion effect may not be large compared to time, and thus may be inefficient.

In addition, sufficient adsorption force between the ionomer and the carbon support in the catalyst is important in order to form a catalyst layer having a uniform structure. If the particle size of the ionomer is controlled to be small through such ultrasonication, the ionomer may be uniformly adsorbed onto the carbon support in the catalyst.

According to one embodiment of the present specification, the composition may further include dispersing the composition in a sonication treatment and a high shear mixer.

The high shear mixer method is not limited thereto, but is preferably performed for 15 minutes to 35 minutes at a speed of 10 m / s to 40 m / s.

The catalyst composition prepared according to the method for preparing the catalyst composition may be used to form an electrode catalyst layer for a fuel cell.

The electrode catalyst layer may be prepared according to conventional methods known in the art, and may be formed, for example, by applying and drying the catalyst composition on a gas diffusion layer. In this case, a plurality of catalyst layers may be formed by sequentially applying and drying a catalyst composition having a different ionomer content.

In this case, the catalyst composition may be coated onto the gas diffusion layer by printing, tape casting, slot die casting, spraying, rolling, or blade coating. ), Spin coating, inkjet coating, or brushing, but are not limited thereto.

The gas diffusion layer is not particularly limited as long as the substrate has a conductivity and a porosity of 80% or more, and may include a conductive substrate selected from the group consisting of carbon paper, carbon cloth, and carbon felt. The thickness of the substrate may be 30 to 500㎛. If the value is within the above range, the balance between the mechanical strength and the diffusivity of the gas and water can be appropriately controlled. The gas diffusion layer may further include a fine pore layer formed on one surface of the conductive substrate, and the fine pore layer may include a carbon material and a fluorine resin. The microporous layer may inhibit the occurrence of flooding phenomenon by promoting the discharge of excess moisture present in the catalyst layer.

In one embodiment of the present specification, the average particle diameter of the ionomer cluster, which is a unit particle formed by agglomeration of ionomers after the sonication, may be 10 nm to 500 nm, or 10 nm to 300 nm.

(Membrane-electrode assembly)

Herein is a membrane-electrode assembly comprising a cathode catalyst layer, an anode catalyst layer and an electrolyte membrane provided between the cathode catalyst layer and the anode catalyst layer,

At least one of the cathode catalyst layer and the anode catalyst layer provides a membrane-electrode assembly that is made of the catalyst composition for fuel cells described above.

In one embodiment of the present specification, the cathode catalyst layer is made of the catalyst composition for a fuel cell described above.

In one embodiment of the present specification, the hydrogen ion transfer resistance of at least one of the cathode catalyst layer and the anode catalyst layer is 0.2 Ω · cm ⁻² or less, preferably 0.1 Ω · cm ⁻² or less, more preferably 0.05 Ω Cm ^-2 or less, or 0.04? Cm ^-2 or less. In the case of smooth hydrogen ion transfer, there is an advantage to improve the catalyst utilization. At this time, the lower the hydrogen ion transfer resistance of the catalyst layer, the better. Therefore, the lower limit thereof is not particularly limited.

In one embodiment of the present specification, the ohmic resistance of the membrane-electrode assembly may be 200 mΩ · cm ⁻² or less, preferably 100 mΩ · cm ⁻² or less, more preferably 70 mΩ · cm ⁻² or less. . In this case, there is an effect that the performance itself of the membrane-electrode assembly is improved. The ohmic resistance of the membrane-electrode assembly may be achieved by preparing the cathode catalyst layer or the anode catalyst layer of the membrane-electrode assembly with the catalyst composition for a fuel cell.

In one embodiment of the present specification, the hydrogen ion conductivity (σ) of the catalyst layer may be calculated by the following Equation 1.

[Equation 1]

R = t / (A · σ)

In Equation 1, R is the hydrogen ion transfer resistance of the catalyst layer, t is the average thickness of the catalyst layer, A is the area of the catalyst layer.

When the average thickness of the catalyst layer is 10㎛ and the area of the catalyst layer is 25cm ² , the catalyst layer

The hydrogen ion conductivity may be 0.02 mS · cm ^{−1 or} more, and specifically 0.03 mS · cm ^{−1 or} more. In this case, there is an advantage to improve the utilization of the catalyst by a smooth hydrogen ion transfer. At this time, the higher the hydrogen ion conductivity of the catalyst layer is, the better, and therefore the upper limit thereof is not particularly limited.

In one embodiment of the present specification, the catalyst layer may have an average thickness of 3 μm or more and 15 μm or less, and specifically, based on 0.3 mgPt / cm ² (the weight of Pt per reference area (1 cm ² ) is 0.3 mg). 5 micrometers or more and 12 micrometers or less may be sufficient. In this case, there is an advantage to ensure the appropriate porosity and hydrogen ion conductivity.

In this case, the catalyst layer using the catalyst composition may be formed using various coating methods such as bar coating, spraying, screen printing, slot die, etc. on the substrate, but is not limited thereto.

In one embodiment of the present specification, the electrolyte membrane may be a polymer electrolyte membrane.

In one embodiment of the present specification, the polymer electrolyte membrane is provided between the cathode catalyst layer and the anode catalyst layer, the polymer included in the polymer electrolyte membrane may be an ion conductive polymer.

In one embodiment of the present specification, the ion conductive polymer may be a hydrocarbon-based polymer, a partially fluorine-based polymer or a fluorine-based polymer. Specifically, the polymer electrolyte membrane may be a hydrocarbon-based polymer electrolyte membrane or a fluorine-based polymer electrolyte membrane.

In one embodiment of the present specification, the hydrocarbon-based polymer may be a hydrocarbon-based sulfonated polymer without a fluorine group, and the fluorine-based polymer may be a sulfonated polymer saturated with a fluorine group. The partially fluorine-based polymer may be a sulfonated polymer that is not saturated with a fluorine group.

In one embodiment of the present specification, the ion conductive polymer is a perfluorosulfonic acid polymer, a hydrocarbon polymer, an aromatic sulfone polymer, an aromatic ketone polymer, a polybenzimidazole polymer, a polystyrene polymer, a polyester polymer, Polyimide polymer, polyvinylidene fluoride polymer, polyethersulfone polymer, polyphenylene sulfide polymer, polyphenylene oxide polymer, polyphosphazene polymer, polyethylene naphthalate polymer, polyester polymer, Doped polybenzimidazole polymer, polyether ketone polymer, polyether ether ketone polymer, polyphenylquinoxaline polymer, polysulfone polymer, polypyrrole polymer and polyaniline polymer selected from the group consisting of It may be a polymer or more. The polymer may be used by sulfonated and may be a single copolymer, an alternating copolymer, a random copolymer, a block copolymer, a multiblock copolymer or a graft copolymer, but is not limited thereto.

In one embodiment of the present specification, when the polymer electrolyte membrane includes a hydrocarbon-based polymer, the polymer electrolyte membrane may be a hydrocarbon-based polymer that is a block copolymer including a hydrophilic block and a hydrophobic block.

In one embodiment of the present specification, the average thickness of the polymer electrolyte membrane may be 1 μm or more and 100 μm or less.

In one embodiment of the present specification, the membrane-electrode assembly includes a cathode gas diffusion layer provided on a surface opposite to a surface on which an electrolyte membrane of the cathode catalyst layer is provided; And an anode gas diffusion layer provided on an opposite side of the surface of the anode catalyst layer on which the electrolyte membrane is provided.

In an exemplary embodiment of the present specification, the anode gas diffusion layer and the cathode gas diffusion layer are provided on one surface of the catalyst layer, respectively, and serve as a current conductor, and become a passage for the reaction gas and water, and have a porous structure. Therefore, the gas diffusion layer may include a conductive substrate.

In one embodiment of the present specification, the conductive substrate may be a conventional material known in the art, for example, carbon paper, carbon cloth, or carbon felt. ) May be preferably used, but is not limited thereto.

In one embodiment of the present specification, the average thickness of the gas diffusion layer may be 100 μm or more and 500 μm or less. In this case, there is an advantage of minimizing the reactant gas transfer resistance through the gas diffusion layer and an optimum state in view of the proper moisture content in the gas diffusion layer.

(Fuel cell)

The present specification provides a fuel cell including the membrane-electrode assembly.

FIG. 1 schematically illustrates the principle of electricity generation of a fuel cell. In the fuel cell, the most basic unit for generating electricity is a membrane-electrode assembly (MEA), which is an electrolyte membrane (M) and the electrolyte membrane (M). It is composed of an anode (A) and a cathode (C) formed on both sides of. Referring to FIG. 1, which illustrates the electricity generation principle of a fuel cell, an oxidation reaction of a fuel (F) such as hydrogen or a hydrocarbon such as methanol and butane occurs at the anode (A) to generate hydrogen ions (H ⁺ ) and electrons (e ⁻ ). And hydrogen ions move to the cathode C through the electrolyte membrane M. The cathode C reacts with hydrogen ions transferred through the electrolyte membrane M, an oxidizing agent O such as oxygen, and electrons to generate water W. This reaction causes the movement of electrons in the external circuit.

As shown in FIG. 2, the membrane-electrode assembly may include an electrolyte membrane 10 and a cathode 50 and an anode 51 positioned to face each other with the electrolyte membrane 10 interposed therebetween. In detail, the cathode includes a cathode catalyst layer 20 and a cathode gas diffusion layer 30 sequentially provided from the electrolyte membrane 10, and the anode includes an anode catalyst layer 21 and an anode sequentially provided from the electrolyte membrane 10. It may include a gas diffusion layer (31).

3 schematically illustrates the structure of a fuel cell, in which the fuel cell includes a stack 60, an oxidant supply unit 70, and a fuel supply unit 80.

The stack 60 includes one or two or more membrane-electrode assemblies described above, and includes two or more separators interposed therebetween when two or more membrane-electrode assemblies are included. The separator prevents the membrane-electrode assemblies from being electrically connected and delivers fuel and oxidant supplied from the outside to the membrane-electrode assembly.

The oxidant supply unit 70 serves to supply the oxidant to the stack 60. Oxygen is typically used as the oxidizing agent, and may be used by injecting oxygen or air into a pump.

The fuel supply unit 80 serves to supply fuel to the stack 60, and to the fuel tank 81 storing fuel and the pump 82 supplying fuel stored in the fuel tank 81 to the stack 60. Can be configured. As fuel, hydrogen or hydrocarbon fuel in gas or liquid state may be used. Examples of hydrocarbon fuels include methanol, ethanol, propanol, butanol or natural gas.

Hereinafter, the present specification will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the present specification, but not to limit the present specification.

Example 1

3M 825 fluorine ionomer was dispersed in a solvent in which the mass ratio of 1-propanol and dipropylene glycol (DPG) solvent was adjusted to 9: 1. After keeping at low temperature at 2 ° C. for 30 minutes, the mass ratio (I / C) of ionomer (I, Ionomer) and carbon (C, Carbon), commercially available from Tanaka, was added to the solution. The electrode slurry was completed after ultrasonic dispersion for 1 hour. The prepared electrode slurry was cast on a polytetrafluoroethylene (PTFE) film using a doctor blade, followed by primary drying at 35 ° C. for 30 minutes, and secondary drying at 140 ° C. for 30 minutes to finally prepare an electrode catalyst layer. It was.

Evaluation of the membrane-electrode assembly to which the electrode catalyst layer was applied was carried out. At this time, the electrolyte membrane used a sulfonated polyetheretherketone-based hydrocarbon-based membrane, the gas diffusion layer (GDL) was used by JNTG company JNT30-A3, the thickness is used to have a range of 280μm to 320μm did. The compression rate of the gas diffusion layer was set to 25% and a glass fiber sheet gasket was used to maintain it. The active area of the membrane-electrode assembly was made 25 cm ² .

Example 2

In Example 1, it carried out by the method similar to Example 1 except having changed the mass ratio of 1-propanol and dipropylene glycol to 8: 2.

Example 3

In Example 1, it carried out by the method similar to Example 1 except having changed the mass ratio of 1-propanol and dipropylene glycol to 7: 3.

Example 4

In Example 1, it carried out by the same method as Example 1 except having changed the mass ratio of 1-propanol and dipropylene glycol to 6: 4.

Comparative Example 1

It carried out by the method similar to Example 1 except having used the mixed solvent of 1-propanol and water as a solvent.

Experimental Example

Experimental Example 1

The performance of the unit cells of Examples 1 to 4 and Comparative Example 1 was used by Nara Cell PEMFC station equipment was measured IV performance in the constant current mode. Specifically, the 0 to 1,500 mA / cm ² was measured by scanning the range to 100 mA / cm ² steps, compared the performance of mA / cm ² in value of 0.6V. The temperature of the unit cell was measured at 70 ° C. and relative humidity at 100% RH. The results are shown in Table 1 below.

MEA Humidity condition Performance (@ 0.6V)
(mA / cm ² ) Comparative Example 1 100% RH 1129 Example 1 1247 Example 2 1283 Example 3 1168 Example 4 1116

Experimental Example 2

In order to calculate the electrochemically active surface area (ECSA) of Examples 1 to 4 and Comparative Example 1, hydrogen and nitrogen were supplied to the anode and the cathode, respectively, and ECSA was determined using Cyclic voltammetry (CV). Calculated. The area of the 0 to 0.4 V region, which is the portion where hydrogen is adsorbed in the CV graph, can be calculated by integration. The temperature of the unit cell was measured at 70 ° C. and relative humidity at 100% RH.

The results are shown in Table 2. It had the highest ECSA value in Example 2 which is a catalyst layer which produced the ratio of monovalent propanol and dipropylene glycol at 8: 2. This shows that the catalyst and ionomer are the most widely contacted in Example 2, and as a result, the performance was also the highest as shown in Table 2 below.

MEA Humidity ECSA (m ² / g) Comparative Example 1 100% RH 54 Example 1 77 Example 2 79 Example 3 43.5 Example 4 39.5

Experimental Example 3

Through the impedance analysis of Examples 1 to 4 and Comparative Example 1, the ohmic resistance of the MEA and the hydrogen ion transfer resistance in the catalyst layer were measured. Impedance measurements were made under the following conditions when the current in the MEA was 0 A / cm ² .

Fuel supplied: Anode / Cathode = H ₂ / N ₂

Driving temperature: 70 ℃

Drive Humidity: 100% RH

The results are shown in Table 3. The hydrogen ion transfer resistance in the catalyst layer is proportional to the length of the 45 ° upper right region in the high frequency region of the impedance graph. It can be seen that the value is significantly reduced in Examples 1 to 4 compared to Comparative Example 1.

This indirectly indicates that ionomers in the catalyst layer were evenly distributed and networked with each other by using a mixed solvent containing DPG.

The ohmic resistance value of MEA also showed that the comparative example 1 prepared using water and 1-propanol showed a high value of 228 mΩ · cm ⁻² , while the examples prepared using a mixed solvent including DPG were all 50 mΩ · cm A result of less than ^-2 was shown.

In the case of Comparative Example 1, the ionomer in the cathode catalyst layer was disconnected without being continuously connected, but in Examples 1 to 4, the ionomer in the cathode catalyst layer was continuously connected well.

MEA Humidity Hydrogen ion transfer resistance in the catalyst layer (Ω · cm ^-2 ) MEA ohm resistor
(mΩcm ^-2 ) Comparative Example 1 100% RH 0.121 228 Example 1 0.038 49 Example 2 0.020 23 Example 3 0.023 40 Example 4 0.020 45

10: electrolyte membrane
20: cathode catalyst layer
21: anode catalyst layer
30: cathode gas diffusion layer
31: anode gas diffusion layer
50: cathode
51: anode
60: stack
70: oxidant supply
80: fuel supply
81: fuel tank
82: pump

Claims (15)

Ionomers;
catalyst; And
A catalyst composition for a fuel cell comprising a mixed solvent containing a monohydric alcohol and a polyhydric alcohol in a mass ratio of 9: 1 to 5: 5. The method of claim 1, wherein the polyhydric alcohol is diethylene glycol (DEG), propylene glycol (propyleneglycol, PG), dipropylene glycol (dipropylene glycol, DPG), 1,3-butylene glycol (1,4-butylene a catalyst composition which is one or two or more mixed solvents selected from the group consisting of glycol) and dihydroterpineol (DHT), triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The catalyst composition for a fuel cell according to claim 1, wherein a boiling point of the polyhydric alcohol is 130 ° C or higher. The catalyst composition for a fuel cell according to claim 1, wherein the content of the mixed solvent is 50 wt% or more and 95 wt% or less based on the total weight of the catalyst composition. The catalyst composition for a fuel cell according to claim 1, wherein a viscosity at 25 ° C. of the catalyst composition for fuel cell is 2.6 cPs or more and 100 cPs or less. The method of claim 1, wherein the ionomer is a fluorine-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polyphenylene sulfide-based polymer, polysulfone-based polymer, polyether sulfone-based polymer, polyether ketone A catalyst composition for a fuel cell, which is a combination of one or two or more selected from the group consisting of a polymer, a polyether-etherketone polymer and a polyphenylquinoxaline polymer. The catalyst composition of claim 1, wherein the ionomer is contained in an amount of 0.01 wt% or more and 6 wt% or less based on the total weight of the catalyst composition for fuel cells. The catalyst composition of claim 1, wherein the catalyst is a catalyst having a metal supported on a surface of a carbon support. The catalyst composition of claim 1, wherein the catalyst is included in an amount of 1 wt% or more and 20 wt% or less based on the total weight of the catalyst composition for fuel cells. Injecting the ionomer into a mixed solvent containing monohydric alcohol and polyhydric alcohol in a mass ratio of 9: 1 to 5: 5;
Injecting a catalyst into the mixture of the mixed solvent and the ionomer; And
The method for preparing a catalyst composition for a fuel cell according to any one of claims 1 to 9, comprising the step of sonicating the mixture into which the catalyst is added. The method of claim 10, wherein the ultrasonication is performed in a tip type or a bath type. A membrane-electrode assembly comprising a cathode catalyst layer, an anode catalyst layer, and an electrolyte membrane provided between the cathode catalyst layer and the anode catalyst layer,
At least one of the cathode catalyst layer and the anode catalyst layer is made of a fuel cell catalyst composition of any one of claims 1 to 9. The membrane-electrode assembly of claim 12, wherein the hydrogen ion transfer resistance of at least one of the cathode catalyst layer and the anode catalyst layer is 0.2 Ω · cm ⁻² or less. The membrane-electrode assembly according to claim 12, wherein the ohmic resistance is 200 mΩ · cm ⁻² or less. A fuel cell comprising the membrane-electrode assembly of claim 12.

Images