KR20040092024A - Method to manufacture polymer electrolyte composite membranes for fuel cells - Google Patents

Abstract

PURPOSE: A method for manufacturing a polymer electrolyte composite membrane for a fuel cell is provided to effectively modify the surface of membrane and to reduce the permeability of fuel. CONSTITUTION: The method comprises the process of treating the entire or a part of one or both surfaces of an ion-conductive polymer electrolyte membrane by plasma treatment, flame treatment, corona treatment, ultraviolet-ray treatment, laser treatment, x-ray treatment, gamma-ray treatment, electronic beam treatment, ionic beam treatment or sputtering. In the plasma treatment, at least one gas selected from the group consisting of argon, aqueous vapor, air, nitrogen, oxygen, hydrogen, freon gas, and a hydrocarbon gas including methane, ethane, ethylene, acetylene, propane and butane are employed. Further, the method may comprise the process of coating a polymer film on the treated surface of electrolyte membrane through grafting reaction and then, optionally the process of sulfonating the coated surface.

Description

Method for manufacturing polymer electrolyte composite membranes for fuel cells

The present invention provides a method for producing an ion conductive polymer electrolyte composite membrane (hereinafter referred to as 'polymer electrolyte composite membrane') that can be used in a fuel cell, which is regarded as a next-generation clean energy source, a polymer electrolyte composite membrane prepared by the method and the composite membrane. The fuel cell used is described in more detail. By treating the surface of the ion conductive polymer electrolyte membrane with plasma, the properties of the membrane surface are modified so that the fuel (alcohol, formic acid, glycerol, hydrogen, etc.) By preventing the permeation and coating a new polymer film on the surface of the polymer electrolyte membrane by plasma induced grafting, the polymer electrolyte composite for fuel cells is stable and thermally stable, giving excellent material permeation selectivity without causing deformation of the base material. Method for producing membrane, composite membrane produced by this method, composite membrane Employing an electrolyte membrane-electrode assembly (membrane-electrode assembly, hereinafter 'MEA'), and relates to a fuel cell employing a composite membrane, or the MEA.

The basic principle of a fuel cell is to produce electricity and water from hydrogen and oxygen using the reverse electrolysis of water. Since the fuel cell is not subject to the thermodynamic limitation (Carnot efficiency) of the heat engine in principle, the power generation efficiency is 40 to 55%, which is very high compared to the existing power generation equipment, and there are no nitrogen compounds or sulfur compounds in the exhaust gas, and noise or vibration This is an almost environmentally friendly way of development.

Among the fuel cells having many of these advantages, the polymer electrolyte fuel cell is defined from the use of the polymer electrolyte membrane as the electrolyte of the cell. In fuel cells, the polymer electrolyte membrane acts as an insulator for electrons and as a conductor for ions.

Such a polymer fuel cell can be used as a power source for electric vehicles, mobile phones, laptops, such as communication devices or electric vehicles that require low weight and low volume, and can be applied as a distributed power source and an auxiliary power source.

Commercially recognized hydrogen ion conductive polymer electrolyte membranes include a perfluoro sulfonic acid-based ion exchange membrane (US Pat. No. 3,282,875; US Pat. No. 4,330,654). Examples include Nafion Membrane (Dupontsa), Dow Chemical Membrane (Dow Chemical Inc.), Flemion Membrane (Asahi Glass Inc.), Aciplex Membrane (Asahi Chemical Inc.), Balm Membrane (BAM, Ballard Co.) Gore, etc. have been reported. These perfluorinated sulfonic acid-based membranes are well received for their high ionic conductivity and excellent mechanical and chemical stability. However, they are expensive and fuel is used at the anode in the operation of alcohol fuel cells using alcohols such as methanol. There is a problem in that the fuel crossover to the cathode occurs seriously.

In order to make up for these shortcomings, three directions of research are being conducted. First, the development of a hydrocarbon-based new polymer electrolyte (J. Membr. Sci., 154,175 (1999); Korean Patent Publication No. 2002-0020877) Second, a composite membrane impregnated with a polymer electrolyte material using a porous polymer or an inorganic base material (US Pat. No. 5,547,551; US Pat. No. 5,795,668; US Pat. No. 6,248,469 B1) or polymer and ion conductivity A composite membrane mixed with materials is prepared (US Pat. No. 6,059,943; US Pat. No. 6,227,512 B1; Korean Patent Publication No. 2001-0030409). Third, performance is improved through surface modification of the polymer electrolyte membrane.

In particular, the third example, the surface treatment of the polymer electrolyte membrane has the advantage of adding new other properties while maintaining the high ionic conductivity and mechanical properties of the existing polymer electrolyte membrane. Recently, the surface of Nafion membrane was treated with metal ions (J. Electrochem. Soc., 145, 3798 (1998)), but the effect of reducing methanol permeability was not significant. In addition, attempts have been made to modify the surface properties of the Nafion membrane by plasma treatment (Surf. & Coat. Technol., 116/119, 996 (1999)) and to prevent methanol permeation. There is a disadvantage in that a polymer thin film having new characteristics cannot be formed on the surface of an electrolyte membrane.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to treat the whole or part of one or both surfaces of the polymer electrolyte membrane surface with plasma or the like, thereby modifying the membrane surface properties to permeate fuel. It is to provide a method for producing a polymer electrolyte composite membrane for a fuel cell.

In addition, another object of the present invention is to treat the surface of the polymer electrolyte membrane with plasma or the like, and then to perform a grafting reaction by plasma treatment or the like to coat a new polymer film on the surface of the membrane or to undergo a sulfonation reaction to deform the base material. The present invention provides a method for producing a polymer electrolyte composite membrane for a fuel cell that provides excellent permeation selectivity without thermal induction and is thermally stable.

Still another object of the present invention is to provide a composite membrane produced by the above method, an MEA employing the composite membrane, and a fuel cell employing the composite membrane or MEA.

1 shows a radiofrequency plasma apparatus used in the method for producing a polymer electrolyte composite membrane for a fuel cell of the present invention.

2 is a schematic view showing a plasma treatment, a grafting process and a sulfonation process in the method of manufacturing a polymer electrolyte composite membrane for a fuel cell of the present invention.

FIG. 3 illustrates an embodiment in which the ion conductive polymer electrolyte membrane is partially plasma treated in the method of manufacturing a polymer electrolyte composite membrane for a fuel cell of the present invention.

Figure 4 shows an apparatus for testing the fuel permeability of the composite membrane prepared by the method for producing a polymer electrolyte composite membrane for a fuel cell of the present invention.

Figure 5 shows a cross-sectional electron micrograph of the composite membrane prepared by the method for producing a polymer electrolyte composite membrane for a fuel cell of the present invention.

** Description of the symbols for the main parts of the drawings **

11 copper coil 12 auto matching network

13: RF generator 14: monomer container

15 plasma treatment gas 16 vacuum pump

17: vacuum gauge 18: sample

19: support 21: polymer electrolyte membrane

22: plasma gas 23: radicals generated on the surface of the electrolyte

24: surface of plasma treated electrolyte membrane

25: grafting film 26: sulfonated polymer film

31 polymer electrolyte membrane 32 masking

In the method for producing a polymer electrolyte membrane for a fuel cell according to the present invention for achieving the above object, in order to modify the surface of the ion conductive polymer electrolyte membrane for fuel cells to lower the permeability of the fuel material, one or both sides of the polymer electrolyte membrane A method of manufacturing a composite film which undergoes a surface treatment process for all or part of the surface treatment process, the surface treatment process is plasma treatment, flame treatment, corona treatment, ultraviolet treatment, laser treatment, X-ray treatment, gamma ray treatment, electron beam treatment, ion beam It is characterized in that the process of treating the surface of the polymer electrolyte membrane using a treatment, or sputtering.

In the method for producing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the gas used for plasma irradiation in the plasma treatment is argon, water, air, nitrogen, oxygen, hydrogen, freon gas, and methane, ethane, ethylene, acetylene, It is characterized in that at least one selected from the group consisting of a hydrocarbon gas containing propane, butane.

In the method for producing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the polymer electrolyte membrane may be a Nafion membrane, a Dow Chemical membrane, a Flemion membrane, an Aflexex membrane, a chestnut membrane which is a perfluorinated sulfonic acid system; Hydrocarbon based sulfonated polyimide (PI) membranes, polyetheretherketone (PEEK) membranes, sulfonated polyphosphosazine membranes, sulfonated polyethersulfone (PES) membranes, sulfonated polybenzimidazole membranes; Composite membrane premier membrane, polytetrafluoroethylene / polyvinylidene fluoride-hexafluoropropylene-grafted-polystyrene copolymer (PTFE / PVDF-HFP-g-PS) membrane, Nafion-silica blend membrane, na Pion-PVDF blend membrane, Nafion-phosphotungstic acid membrane; Or it is a composite polymer electrolyte membrane containing 30 to 100%, preferably 70 to 97% of the ion conductive polymer electrolyte.

In the method of manufacturing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the plasma is generated using a radiofrequency plasma apparatus or a microwave plasma apparatus, and the plasma generation power is 10 watts (W) to 500 watts, preferably 50 watts. To an intensity range of 200 watts.

In the method for producing a polymer electrolyte composite membrane for a fuel cell according to the present invention, after the surface treatment, plasma treatment, flame treatment, corona treatment, ultraviolet treatment, laser treatment, X-ray treatment, gamma ray treatment, electron beam treatment, ion beam treatment, Alternatively, the method may further include coating a new polymer film on the surface of the electrolyte membrane by performing a grafting reaction on all or part of the surface of the polymer electrolyte membrane using sputtering.

In the method for producing a polymer electrolyte membrane for a fuel cell according to the present invention, the monomer used in the grafting reaction is styrene, a mixture of styrene-divinylbenzene, aryl amine, acrylic acid, pentene, ethylene, butadiene, cyclohexene, vinyl acetate At least one selected from the group consisting of tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride.

When the monomer is used, linear polymers are synthesized. Therefore, in order to modify the properties of the polymer film by crosslinking the polymer, a crosslinking agent should be added during the grafting reaction.

The present invention is a divinyl benzene (DVB), ethylene glycol dimethacrylate (EGDMA), diethylene glycol diacrylate, N, N- methylene bisacrylamide (N, N- methylene bisacrylamide), diaryl phthalate, and 1,3-butanediol dimethacrylate are used together. At this time, the amount of crosslinking agent used is 0.01 to 10 mol%, preferably 1 to 5 mol% based on the monomer. In the present invention, the crosslinking density is controlled by controlling the amount of the crosslinking agent.

In the method of manufacturing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the thickness of the coating membrane by the grafting reaction is characterized in that several tens of nanometers to several hundred micrometers.

In the method of manufacturing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the thickness of the coating membrane by the grafting reaction is preferably 1 micrometer to 20 micrometers.

In the method for producing a polymer electrolyte composite membrane for a fuel cell according to the present invention, after the surface treatment by the plasma or the surface coating by the plasma-induced grafting reaction, and further comprising a sulfonation process for improving the ion conductivity. do.

In the method for producing a polymer electrolyte composite membrane for a fuel cell according to the present invention, the method is performed in order to prevent the permeation of alcohol, glycerol, or formic acid containing hydrogen, methanol, ethanol, isopropanol, which are fuels, in a portion other than the electrode. Surface treatment of the outer portion of the electrolyte membrane that is not in direct contact with the battery electrode is characterized by reducing or eliminating fuel permeability and ion conductivity.

A fuel cell polymer electrolyte composite membrane according to the present invention is produced by the method described above.

The electrolyte membrane-electrode assembly according to the present invention is characterized by comprising the polymer electrolyte composite membrane for a fuel cell.

A fuel cell according to the present invention is characterized by comprising a polymer electrolyte composite membrane for a fuel cell or the above electrolyte membrane-electrode assembly produced by the method described above.

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

In the present invention, the surface of the ion conductive polymer electrolyte membrane used in the fuel cell is treated in whole or in part by plasma surface treatment and / or by coating a new polymer film on the surface of the polymer electrolyte membrane through a plasma induced grafting reaction. A polymer electrolyte composite membrane capable of lowering the permeability of alcohols such as hydrogen, methanol, ethanol, and propanol, glycerol, and formic acid, which are used as fuels, is prepared.

Plasma is a gas separated by electrons and ions, and refers to a gas that is neutral in that its ionization degree is considerably higher than that of the neutral atom, and the negative number of charges is almost the same.

Since the electrons in the plasma can excite, dissociate, and ionize gas atoms or molecules through active thermal motions, chemical reactions may occur in the plasma or on the solid surface in contact with the plasma, depending on the type of gas used.

The active chemical properties of the plasma can be used to provide extreme environments that are difficult to obtain by conventional methods to synthesize new materials or to change the properties of the polymer surface to give physical and chemical properties that are different from the body. For example, when the surface of the polymer is treated with nitrogen or oxygen plasma, hydrophilicity or hydrophobicity can be given to the surface of the polymer.

In the present invention, 13.56 MHz (MHz) radio frequency plasma apparatus was used for plasma surface treatment of perfluorinated sulfonic acid polymer electrolyte membrane. However, it is also possible to use microwave plasma apparatus.

In the present invention, a plasma treatment, a flame treatment, a corona treatment, an ultraviolet treatment, a laser treatment, an X-ray treatment, a gamma ray treatment, an electron beam treatment, an ion beam treatment, or sputtering is used to coat a new polymer film on the surface of the polymer electrolyte membrane. .

Plasma surface treatment of the polymer electrolyte membrane of the present invention can be performed using the treatment apparatus shown in FIG.

In the plasma-induced grafting reaction used in the present invention, plasma treatment is performed on the polymer electrolyte membrane using the apparatus of FIG. 1, and then immersed in a desired monomer solution to proceed the grafting reaction at an appropriate temperature. The reaction time and temperature may vary depending on the respective monomers, and at least 48 hours, the composite membrane may be too thick, which is not preferable. In addition, the selected monomer solution can be adjusted from several tens of nanometers to several hundred micrometers depending on the reaction time and conditions.

When the grafting reaction is carried out through the above process, a new nonionic conductive polymer film (hereinafter referred to as 'inert film') is formed on the surface of the polymer electrolyte membrane. Since the material forming the inert film has very low or no ion conductivity, methanol The permeability is very low for alcohols such as or other fuels described above.

In the plasma-induced grafting reaction used in the present invention, after plasma treatment of the polymer electrolyte membrane using the apparatus of FIG. 1, the monomer is vaporized using the vapor pressure of the monomer through the apparatus shown in FIG. 1. By flowing in a gaseous state, the film grafting reaction may be advanced to the polymer electrolyte. In this case, the resulting film may be manufactured as a thin film having a thickness within several micrometers. The flow rate can be within 100 cubic centimeters per minute (SCCM), preferably 20-80 cms, and the reaction time is preferably within 48 hours.

In particular, the present invention involves the partial plasma treatment of a polymer electrolyte membrane. In this method, after plasma treatment of only the portion of the polymer electrolyte membrane that will not be in contact with the electrode, the inert film is coated by the above grafting reaction, so that the part where the electrode touches is maintained to maintain ion conductivity, and the outer part where the electrode does not touch This is a way to significantly reduce the methanol permeability. By removing the ion conductivity and the methanol permeability from the outer portion of the electrode, the MEA can be prevented from being corroded in contact with the metal, and the fuel permeability can be reduced to increase the fuel cell performance.

Partial plasma treatment of the polymer electrolyte membrane is easily described with reference to FIG. Partial plasma treatment of the electrolyte membrane is performed by masking a portion where the plasma surface treatment and / or the plasma induced grafting reaction will not be performed by masking and then performing a plasma treatment.

In the present invention, after preparing a polymer electrolyte composite membrane in which an inert film is formed on the surface of the polymer electrolyte membrane by the above method, a sulfonation process may be further included to improve ion conductivity. The sulfonation method can be carried out by the method described in US Pat. No. 3,870,841 when the composite membrane contains aromatics. Sulfonation proceeds through sulfonating agents such as acetic sulfate or chlorosulfuric acid, which is more preferred because of the ease of reaction control. Acetic sulfate is prepared by reacting sulfuric acid with acetic anhydride, and then reacted with a polymer electrolyte composite membrane in 1,2-dichloroethane solution. The reaction proceeds. Reaction temperature is between 40-70 degreeC, 50-60 degreeC is the most preferable, reaction time is between 0.5-48 hours, Preferably 4-6 hours are suitable. The amount of acetic sulfate can be controlled to control the degree of sulfonation. By controlling the molar ratio of the aromatic polymer and the acetic sulfate present in the inert film of the composite membrane, it is possible to control the sulfonation degree between 0 and 95%. If the sulfonation degree is too low, the ion conductivity is low, and if the sulfonation degree is too high, the fuel permeability is increased, so it is preferable to maintain the sulfonation degree between 20 and 70%. Through this method, the fuel permeability of the polymer electrolyte composite membrane can be lowered while the ionic conductivity can be maintained or improved.

In the present invention, various polymer membranes can be produced to improve the performance of fuel cells by controlling various manufacturing conditions in the process of film coating and sulfonation reaction by surface treatment, grafting reaction (linear and crosslinking grafting membrane). can do. For example, by controlling the grafting time and the degree of crosslinking during the preparation of the polymer film through the crosslinking grafting reaction, it is possible to manufacture a polymer film having optimal properties in terms of durability and fuel permeability. In addition, it is possible to control the ion exchange capacity of the composite membrane by changing the sulfonation agent and sulfonation reaction conditions during sulfonation.

The objects, features and advantages of the present invention will become more apparent upon a review of the description of the preferred embodiments of the present invention. The following examples show a method for measuring the polymer electrolyte composite membrane according to the present invention and the performance of the polymer electrolyte composite membrane thus prepared, and the present invention is not limited in scope by these examples.

<Example 1>

In order to induce the grafting reaction of polystyrene on the surface of the Nafion 117 polymer electrolyte membrane of DuPont, a kind of perfluorinated sulfonic acid membrane, the surface of the polymer electrolyte membrane was plasma treated with argon gas using the apparatus of FIG. 1. Plasma equipment was used to plasma treatment the polymer electrolyte membrane at 200 watts for 2 minutes using a 13.56 MHz alternating current power generator and an automatching network (auto electronics.co., Korea). The pressure of argon in the vacuum chamber was maintained at 0.3 Torr.

The plasma treated film was immediately immersed in purified styrene solution (Aldrich Co., USA) without contact with air. As a styrene solution, a grafting reaction was performed using a solution of 30/70 (methanol / styrene: v / v%, 30 ml) with respect to a methanol solution. At this time, the reaction was stirred in a three-necked flask at 50 ° C. in a constant temperature bath at 200 APM (rpm, resolution per minute) using a stirrer for 6 hours (composite membrane 1), 12 hours (composite membrane 2), and 24 hours ( It proceeded for the composite membrane 3). In this manner, a composite membrane coated with a linear polystyrene film on the surface of Nafion was prepared.

After completion of the reaction, soak in 1,2-dichloroethane (Aldrich Co., USA) for at least 24 hours to remove the remaining unreacted monomer and grafted homopolymer. Rinsed in chloroethane and stored in deionized water.

Methanol permeability of the prepared polymer electrolyte composite membrane was measured using the apparatus shown in FIG. Since the measuring method of a methanol permeability coefficient follows the well-known method generally used, the detailed description is abbreviate | omitted.

The methanol permeability coefficient for each composite membrane is shown in Table 1 below.

Grafting Response Time (hr) Composite film thickness (μm) Methanol Permeability (㎠ / s) Nafion Membrane 180 2.42 × 10 ^-6 Composite Membrane 1 6 199 2.35 × 10 ^-6 Composite Membrane 2 12 213 2.17 × 10 ^-6 Composite Membrane 3 24 240 0.77 × 10 ^-6

As shown in Table 1, when the linear polymer film is coated on the surface of the polymer electrolyte membrane by performing a plasma induced grafting reaction after the plasma treatment according to an embodiment of the present invention, the fuel material ( Methanol) can be seen that the permeability is reduced.

<Example 2>

In the same manner as in Example 1, after the plasma treatment, a styrene-divinylbenzene monomer was used to form a crosslinked polymer film. At this time, the molar content and reaction time of the divinylbenzene crosslinking agent were changed as variables, and all other conditions were kept the same.

The composite membranes 4 and 5 had a molar content of divinylbenzene 0.5 mol% and the reaction time was 6 hours and 12 hours, respectively. The composite membranes 6 and 7 had a molar content of divinylbenzene 1 mol% and a reaction time was 6 hours and 12 hours, respectively. In addition, the composite films 8 and 9 had a molar content of divinylbenzene 2 mol%, the reaction time was 6 hours and 12 hours, respectively, and the composite films 10 and 11 had a 5 mol% molar content of divinylbenzene, and The time is 6 hours and 12 hours, respectively.

The methanol permeability coefficient for each composite membrane is shown in Table 2 below.

Divinylbenzene molarity (%) Grafting reaction time (hr) Composite film thickness (μm) Methanol Permeability (㎠ / s) Nafion Membrane 0 180 2.42 × 10 ^-6 Composite Membrane 4 0.5 6 201 1.26 × 10 ^-6 Composite Membrane 5 0.5 12 211 1.33 × 10 ^-6 Composite Membrane 6 1.0 6 190 0.32 × 10 ^-6 Composite Membrane 7 1.0 12 201 0.54 × 10 ^-6 Composite Membrane 8 2.0 6 187 0.96 × 10 ^-6 Composite Membrane 9 2.0 12 192 0.75 × 10 ^-6 Composite Membrane 10 5.0 6 183 0.77 × 10 ^-6 Composite Membrane 11 5.0 12 187 0.73 × 10 ^-6

As shown in Table 2, when the cross-linked polymer film is coated on the surface of the polymer electrolyte membrane according to the embodiment of the present invention, the linear polymer film is formed using only styrene (composite membrane 1 and composite membrane 2) and the existing It can be seen that the permeability of fuel material (methanol) is greatly reduced compared to the case of using commercial Nafion membrane. In addition, as the divinylbenzene content increased, the thickness of the polymer film formed on the Nafion surface decreased.

5 is a cross-sectional electron microscope photograph observed to analyze the shape of the cross-section after grafting polystyrene to the Nafion surface using a plasma. As shown in FIG. 5, it can be seen that a polystyrene layer of about 10 micrometers (µm) is formed on the surface of Nafion.

<Example 3>

The crosslinked polystyrene composite membrane prepared in Example 2 was subjected to sulfonation of the aromatic group of polystyrene using a sulfonating agent. Acetic sulfate was prepared by reacting sulfuric acid with acetic anhydride, and then a polymer composite membrane was added to a 1,2-dichloroethane solution, followed by stirring at 50 ° C. for 6 hours under a nitrogen atmosphere. Proceeded. At this time, the amount of acetic sulfate was made to be 5 times the molar ratio of the aromatic group. The methanol permeability of the prepared sulfonated composite membrane was measured in the same manner as in Examples 1 and 2, and the ion conductivity was measured using an alternating current impedance method at room temperature. Ionic conductivity was measured after soaking in ultrapure water for at least 24 hours before measurement.

Composite membranes 12 and 13 had a crosslinking agent concentration of 0.5% and reaction time of 6 hours and 12 hours, respectively. Composites 14 and 15 had crosslinking agent concentrations of 1% and reaction time of 6 hours and 12 hours, respectively. If it is. In addition, the composite membranes 16 and 17 had a crosslinking agent concentration of 2%, and the reaction time was 6 hours and 12 hours, respectively. The composite membranes 18 and 19 had a crosslinking agent concentration of 5%, and the reaction time was 6 hours, respectively. 12 hours.

Ion conductivity and methanol permeability coefficient for each composite membrane are shown in Table 3 below.

Crosslinking agent concentration (%) Sulfonation reaction time (hr) Ion Conductivity (S / cm) Methanol Permeability (㎠ / s) Nafion Membrane 0 0 0.096 2.42 × 10 ^-6 Composite Membrane 12 0.5 6 0.075 1.63 × 10 ^-6 Composite Membrane 13 0.5 12 0.073 1.65 × 10 ^-6 Composite Membrane 14 1.0 6 0.083 0.95 × 10 ^-6 Composite Membrane 15 1.0 12 0.081 1.07 × 10 ^-6 Composite Membrane 16 2.0 6 0.091 1.32 × 10 ^-6 Composite Membrane 17 2.0 12 0.090 1.18 × 10 ^-6 Composite Membrane 18 5.0 6 0.095 1.20 × 10 ^-6 Composite Membrane 19 5.0 12 0.094 1.13 × 10 ^-6

After sulfonation of the composite membrane of Example 2, the ion conductivity showed a value similar to that of the Nafion membrane, and the methanol permeability coefficient was higher than that before the sulfonation, but still lower than that of the Nafion membrane.

<Example 4>

One surface of the perfluorinated sulfonic acid membrane was plasma treated using argon plasma in the same reactor as that of Example 1, and then the surface-modified composite membrane was prepared by aging in air. The process of forming the film did not go through. At this time, the pressure of the reactor was 0.3 Torr and the plasma reaction time was 5 minutes. The plasma power of the composite film 20 was 50W, and the composite film 21 was 200W. Methanol permeability and ion conductivity of the plasma-treated polymer electrolyte membrane were measured in the same manner as in Examples 1 and 3.

Ion conductivity and methanol permeability coefficient for each composite membrane are shown in Table 4 below.

Plasma Power (W) Methanol Permeability Coefficient (㎠ / S) Ion Conductivity (S / cm) Nafion Membrane 2.42 × 10 ^-6 0.096 Composite Membrane 20 50 1.52 × 10 ^-6 0.081 Composite Membrane 21 200 1.13 × 10 ^-6 0.080

As shown in Table 4, the composite membranes 20 and 21 prepared according to the present invention can be seen that the methanol permeability is greatly reduced without changing the ion conductivity.

In the present invention, the surface of the polymer electrolyte membrane is treated with plasma, thereby modifying the properties of the membrane surface to reduce fuel permeability. In addition, the present invention by treating the surface of the polymer electrolyte membrane with a plasma and then proceeding the plasma-induced grafting reaction to coat the membrane surface, giving excellent permeation selectivity without causing deformation of the base material, thermally stable polymer An electrolyte composite membrane was prepared.

The plasma surface coating film prepared according to the present invention can be controlled to a very thin (hundreds of nanometers to hundreds of micrometers) film without defects, and has excellent permeability selectivity due to the compactness and high crosslinkability of the formed film. Stable. In the present invention, by coating the surface of the film using plasma, the adhesion is better than when using the conventional deposition method, and the deposition temperature can be lowered, so that deformation and modification of the base metal accompanying conventional high temperature heating conditions can be reduced. Therefore, the fuel cell employing the polymer electrolyte composite membrane according to the present invention improves battery performance.

In addition, the present invention has the advantage that the conventional commercial membrane can be used as it is, furthermore, by treating the outer portion of the electrolyte membrane that does not contact the electrode with methanol impermeability, while reducing the fuel permeability while using the high ion conductivity of the polymer electrolyte. The polymer electrolyte composite membrane can be prepared.

Claims (14)

In order to reduce the permeability of the fuel material by modifying the surface of the ion conductive polymer electrolyte membrane for a fuel cell, a composite membrane manufacturing method that is subjected to the surface treatment process on all or part of one side or both sides of the polymer electrolyte membrane, The surface treatment process is a process of treating the surface of the polymer electrolyte membrane using plasma treatment, flame treatment, corona treatment, ultraviolet treatment, laser treatment, X-ray treatment, gamma ray treatment, electron beam treatment, ion beam treatment, or sputtering. A method for producing a polymer electrolyte composite membrane for a fuel cell. The method of claim 1, The gas used for the plasma irradiation in the plasma treatment is at least one from the group consisting of argon, water, air, nitrogen, oxygen, hydrogen, freon gas, and a hydrocarbon gas containing methane, ethane, ethylene, acetylene, propane, butane Method for producing a polymer electrolyte composite membrane for a fuel cell, characterized in that selected. The method according to claim 1 or 2, The polymer electrolyte membrane may be a perfluorosulfonic acid-based Nafion membrane, Dow Chemical membrane, Flemion membrane, Aciplex membrane, chestnut membrane; Hydrocarbon based sulfonated polyimide (PI) membranes, polyetheretherketone (PEEK) membranes, sulfonated polyphosphosazine membranes, sulfonated polyethersulfone (PES) membranes, sulfonated polybenzimidazole membranes; Composite membrane premier membrane, polytetrafluoroethylene / polyvinylidene fluoride-hexafluoropropylene-grafted-polystyrene copolymer (PTFE / PVDF-HFP-g-PS) membrane, Nafion-silica blend membrane, na Pion-PVDF blend membrane, Nafion-phosphotungstic acid membrane; Or a composite polymer electrolyte membrane containing 30 to 100% of an ion conductive polymer electrolyte. The method according to claim 1 or 2, The plasma is generated using a radiofrequency plasma apparatus or a microwave plasma apparatus, the plasma generation output is a method of producing a polymer electrolyte composite membrane for a fuel cell, characterized in that the intensity range of 10 watts (W) to 500 watts. The method of claim 1, After the surface treatment, plasma treatment, flame treatment, corona treatment, ultraviolet treatment, laser treatment, X-ray treatment, gamma ray treatment, electron beam treatment, ion beam treatment, or sputtering is used to graf all or part of the surface of the polymer electrolyte membrane. The method of manufacturing a polymer electrolyte composite membrane for a fuel cell, characterized in that further comprising the step of proceeding the reaction to coat a new polymer film on the surface of the electrolyte membrane. The method of claim 5, Monomers used in the grafting reaction include styrene, a mixture of styrene-divinylbenzene, aryl amine, acrylic acid, pentene, ethylene, butadiene, cyclohexene, vinyl acetate, tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride Method for producing a polymer electrolyte composite membrane for a fuel cell, characterized in that at least one selected from the group consisting of. The method of claim 6, Divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol diacrylate, N, N-methylene bisacrylamide, diaryl phthalate, or 1,3-butanediol dimethacrylate, which are crosslinking agents, are used as the monomer. A method for producing a polymer electrolyte composite membrane for a fuel cell, which is used together. The method of claim 5, The thickness of the coating film by the grafting reaction is a method of manufacturing a polymer electrolyte composite membrane for a fuel cell, characterized in that several tens of nanometers to several hundred micrometers. The method of claim 8, The thickness of the coating film by the grafting reaction is a method for producing a polymer electrolyte composite membrane for a fuel cell, characterized in that 1 to 20 micrometers. The method according to claim 1 or 5, After the surface treatment by the plasma or the surface coating by the plasma induced grafting reaction, a method for producing a polymer electrolyte composite membrane for a fuel cell, characterized in that further comprising a sulfonation process for improving the ion conductivity. The method according to claim 1 or 5, The method is to surface-treat the outer portion of the electrolyte membrane that is not in direct contact with the fuel cell electrode in order to prevent the permeation of alcohol, glycerol, or formic acid, including fuel, hydrogen, methanol, ethanol, isopropanol, from the parts other than the electrode A method for producing a polymer electrolyte composite membrane for a fuel cell, characterized by reducing or eliminating fuel permeability and ion conductivity. A polymer electrolyte composite membrane for a fuel cell, which is produced by the method according to claim 1. An electrolyte membrane-electrode assembly comprising the polymer electrolyte composite membrane for a fuel cell of claim 12. A fuel cell comprising a polymer electrolyte composite membrane for a fuel cell or an electrolyte membrane-electrode assembly according to claim 13 produced by the method according to claim 1.