KR20080039615A - Composite electrolyte membrane and fuel cell using the same - Google Patents

Abstract

A composite electrolyte membrane is provided to prevent degradation of the membrane by removing hydroxy radicals generated during an operation of a fuel cell, and to exhibit stabler performances at high temperature. A composite electrolyte membrane includes a proton conducting polymer, and carbon nanotubes dispersed in a matrix of the proton conducting polymer. The carbon nanotubes remove hydroxy radicals generated by crossover of a fuel gas. The carbon nanotubes absorb the hydroxy radicals, and the hydroxy radicals absorbed into the carbon nanotubes are removed by combining with the carbon nanotubes or impurities contained in the carbon nanotubes. The carbon nanotube has a length of 10-5000 nm, an outer diameter of 2-50 nm, and an inner diameter of 1-40 nm.

Description

Composite electrolyte membrane and fuel cell using same {COMPOSITE ELECTROLYTE MEMBRANE AND FUEL CELL USING THE SAME}

1 is a graph comparing DMFC performance using a fuel cell having electrolyte membranes of Example 1 and Comparative Example 1, respectively.

The present invention is hydrogen ion conductive polymer; And a composite electrolyte membrane including carbon nanotubes dispersed in a matrix of the hydrogen ion conductive polymer, a membrane electrode assembly including the same, and a fuel cell including the membrane electrode assembly.

Recently, due to the rapid spread of portable electronic devices and wireless communication devices, a lot of interest and research has been progressed in the development of a fuel cell as a battery as a portable power supply source, a fuel cell for a pollution-free automobile and a fuel cell for power generation as a clean energy source.

A fuel cell is an energy conversion device that converts chemical energy of a fuel directly into electrical energy. In other words, the fuel cell is a power generation method that uses fuel gas (hydrogen, methanol, or other organic material) and oxidizing agent (oxygen or air), and generates electric power by using electrons generated during the redox reaction. It is being researched and developed as a next-generation energy source due to its eco-friendly features with low emissions of pollutants and pollutants.

For low humidity polymer electrolyte fuel cell using hydrogen as a fuel (P olymer E lectrolyte M embrane F uel C ell, PEMFC), capable of operating over a wide temperature range because the use of simplified cooling system and the sealing parts, a low humidified hydrogen to the fuel Therefore, it has been spotlighted as a vehicle and home power supply because of the advantages of using a humidifier and fast driving. In addition, it is a high output fuel cell with a higher current density than other types of fuel cells. It operates at a wide range of temperatures, has a simple structure, and has fast startup and response characteristics.

Such a fuel cell has a membrane electrode assembly (MEA) having a hydrogen ion exchange membrane interposed between an anode and a cathode, and a bipolar plate that collects and supplies fuel for electricity generated. It consists of a continuous composite of plates. At the anode, hydrogen or methanol, which is a fuel, is supplied and reacts on the electrode catalyst to generate hydrogen ions (H +, protons). At the cathode, hydrogen ions and oxygen that pass through the hydrogen ion exchange membrane combine to form pure water. Create

The anode and the cathode each consist of a catalyst layer in which oxidation / reduction reactions of reactants occur and a support layer (or gas diffusion layer) supporting the catalyst layer. Porous carbon paper or carbon cloth is widely used as a support layer. In addition to supporting the catalyst layer, the support layer serves as a gas diffusion layer for diffusing the reactants into the catalyst layer, a current collector for moving currents generated from the catalyst layer to the separator plate, a role for passage of the generated water out of the catalyst layer, and a hydrogen ion exchange membrane. It also plays a role in ensuring that adequate moisture is present.

The hydrogen ion exchange membrane uses a polymer electrolyte membrane made of a polymer electrolyte, and its thickness is usually 20 to 300 µm. As a representative polymer electrolyte membrane, a Nafion membrane is known. While sulfonated polymer electrolyte membranes, such as conventional Nafion membranes, exhibit high conductivity and fuel cell performance under sufficient humidification, they are more pronounced in low-humidity conditions due to a drastic decrease in conductivity of hydrogen ions as the moisture in the membrane decreases. The performance degradation is caused. Therefore, use at high temperatures (above 100 ° C.) requires strict water management and requires complex systems.

In order to solve the above problems, various types of organic / inorganic composite electrolyte membranes are added to the organic polymers, which are in addition to proton conducting fillers having high hydrogen ion conductivity and hygroscopicity. (crossover) has a problem that the durability of the electrolyte membrane is lowered and the performance is lowered under low humidity conditions.

The present invention includes a hydrogen ion conductive polymer and carbon nanotubes to prevent hydroxy radicals generated during operation of a fuel cell, thereby preventing decomposition of the membrane, and by implementing high hydrogen ion conductivity and cell performance under low humidity conditions. An object of the present invention is to provide a composite electrolyte membrane that can exhibit more stable performance at high temperatures.

In addition, an object of the present invention is to provide a fuel cell having a membrane electrode assembly (MEA) including the composite electrolyte membrane and the membrane electrode assembly with improved performance.

The present invention is hydrogen ion conductive polymer; And an electrolyte membrane comprising carbon nanotubes dispersed in the matrix of the hydrogen ion conductive polymer,

The carbon nanotubes provide a composite electrolyte membrane characterized by removing hydroxy radicals generated by crossover of fuel gas.

In addition, the present invention is a cathode; Anode; And it provides a membrane electrode assembly (MEA) comprising the composite electrolyte membrane positioned between the cathode and the anode.

In addition, the present invention provides a fuel cell having the membrane electrode assembly.

Hereinafter, the present invention will be described in detail.

In the composite electrolyte membrane of the present invention, carbon nanotubes are dispersed in a matrix of a hydrogen ion conductive polymer, and hydroxy radicals (.OH) generated by crossover of fuel gas during driving of a fuel cell employing the same are described above. It is characterized by being removed by carbon nanotubes.

During operation of the fuel cell, fuel gas such as hydrogen or methanol may crossover the electrolyte membrane to generate hydroxy radicals. For example, hydroxy radicals are generated according to the following mechanism, and further reactions may be caused by the generated hydroxy radicals.

^{_{Fe 2+ + H 2 O 2 →}} Fe 3+ + OH + OH and ^-

Fe ³⁺ + H ₂ O ₂ → [FeOOH ²⁺ ] + H ⁺ → Fe ²⁺ + H ₂ O

And OH ^{+ Fe 2+ → Fe 3+ + OH} -

OH · + H ₂ O ₂ → HO ₂ ㆍ + H ₂ O

These hydroxy radicals attack weak portions of the polymer electrolyte or attack adjacent sites of highly reactive ion exchangers. In particular, some polymer chains having hydrogen-containing end groups are the main targets of hydroxy radical attack, and the polymer main chain is broken by this reaction, thereby deteriorating the durability and cell performance of the polymer electrolyte membrane.

Therefore, the composite electrolyte membrane of the present invention can prevent the decomposition of the polymer electrolyte membrane in advance by removing hydroxy radicals which are the main causes of such radical attack by using carbon nanotubes, and prevent aging of the electrolyte membrane, and stable cell performance. Can be implemented.

In this case, the carbon nanotubes act as a capillary tube to absorb the hydroxy radicals inside (capillary phenomenon), and the hydroxy radicals absorbed into the carbon nanotubes are combined with the carbon nanotubes or the carbon nanotubes. It can be removed in combination with the impurities contained. Specifically, the hydroxy radicals may be removed by forming a covalent bond on the surface of the carbon nanotubes, or by combining with impurities contained in the carbon nanotubes to form H ₂ O or CO ₂ .

In addition, the carbon nanotubes serve to store moisture in the empty space in the tube, and serve as a passage for the movement of moisture and hydrogen ions, the composite electrolyte membrane of the present invention comprising the same has a high hydrogen ion conductivity even under low humidity conditions Cell performance can be achieved. In addition, the electrolyte membrane of the present invention may include carbon nanotubes to suppress fuel permeation and improve moldability of the electrolyte membrane. In addition, since the carbon nanotubes have a thin and long fibrous shape and may serve as a support due to entanglement with each other, the mechanical strength of the electrolyte membrane may be increased.

In addition, the composite electrolyte membrane of the present invention, the electrolyte membrane as described above-that is, the hydrogen ion conductive polymer; And an electrolyte membrane including carbon nanotubes dispersed in the matrix of the hydrogen ion conductive polymer may be stacked on one or both surfaces of the microporous membrane.

Non-limiting examples of the microporous membrane include a polypropylene porous membrane, a polyethylene porous membrane, or a polyolefin porous membrane, and these may be single or mixed two or more kinds.

In the present invention, the carbon nanotubes may have a length of 10 to 5000 nm, an outer diameter of 2 to 50 nm, and an inner diameter of 1 to 40 nm. Preferably the length is 50 to 1000 nm, the outer diameter is 4 to 30 nm, the inner diameter may be 2 to 20 nm.

With such a size, the carbon nanotubes are easily oriented in a predetermined direction, specifically, perpendicular to the electrodes in the electrolyte membrane, and as a result, hydrogen ions are conducted at the shortest distance from the surface (including the inner tube wall). The effect is high and fuel permeation can also be suppressed. When the length of the carbon nanotube is less than 10 nm, the orientation becomes random, and the effect of conducting hydrogen ions (floton) with the shortest surface of the particles, that is, the effect of improving hydrogen ion (floton) conductivity is insufficient. Done. When the length of the carbon nanotubes exceeds 5000 nm, the formability of the electrolyte membrane is lowered, and the permeation of fuels such as hydrogen and methanol tends to increase. In addition, when the outer diameter of the carbon nanotube is less than 2 nm, it is also affected by the length of the carbon nanotube, but the carbon nanotubes are entangled with each other, the orientation becomes random, and a dense electrolyte membrane is not obtained, and hydrogen or methanol is not obtained. It also tends to increase fuel permeability.

In addition, the content range of the carbon nanoparticles in the composite electrolyte membrane is not particularly limited as long as it is a range capable of exhibiting high hydrogen ion conductivity while forming a membrane. For example, 0.0001 to 50% by weight of the composite electrolyte membrane, preferably 0.0001 It may be included in 10% by weight.

The hydrogen ion conductive polymer is not particularly limited as long as it is generally used as an electrolyte membrane polymer. Non-limiting examples of such hydrogen ion conductive polymers include polyaryleneether (PAE), polyetheretherketone (PEEK), polyetherethersulfone (polyetherethersulfone, PEES), polytetrafluoroethylene (PTFE) , Polyvinylidenefluoride (PVDF), Nafion, polyazole, polyvinylalcohol (PVA), polyphenylene oxide, polyphenylene sulfide , Polysulfone, polycarbonate, polystyrene, polyimide, polyamide, polyquinoxaline, polyphosphazene, or polybenzimidazole, and the like, which may be used alone or in combination of two or more thereof. have.

In addition, such a hydrogen ion conductive polymer may have one or more hydrogen ion exchange groups for the stable transfer and transfer of hydrogen ions. Non-limiting examples of the hydrogen ion exchange group include sulfonic acid groups, phosphoric acid groups, hydroxy groups, or carboxylic acid groups.

In particular, the hydrogen ion conductive polymer is preferably a block copolymer including a block in which a hydrophilic functional group such as the hydrogen ion exchange group is dense, and more preferably a multi-block copolymer made of a repeating unit represented by the following formula (1). . This is because the block copolymer has a structure in which the hydrophilic group and the hydrophobic group are selectively concentrated separately compared to the conventional random copolymer, thereby achieving the effect of forming the hydrogen ion conduction channel by the hydrophilic group and increasing the chemical stability by the hydrophobic group.

In Chemical Formula 1,

,

,

,

,

,

,

,

,

,

,

,

, 또는

이고(여기서, R은 -NO₂ 또는 -CF₃임);A, X, and Y are each independently

,

,

,

,

,

,

,

,

,

,

,

, or

And wherein R is —NO ₂ or —CF ₃ ;

,

,

,

,

,

, 또는

이고(여기서, Q는 -SO₃H, -SO₃ ^-M⁺, -COOH, -COO^-M⁺, -PO₃H₂, -PO₃H^-M⁺, 또는 -PO₃ ^2-2M⁺이며, M은 Na 또는 K임);Z is

,

,

,

,

,

, or

And (wherein, Q is ^{_{-SO 3 H, -SO 3 - M}} +, -COOH, -COO - M +, -PO 3 H 2, -PO 3 H - M +, or -PO ₃ ^2- 2M ^+, and , M is Na or K);

,

,

, 또는

이고;B is

,

,

, or

ego;

G is X and G 'is Z;

b / a is 0 <b / a <1 and d / c is 0 <d / c <1;

1 ≦ m <100 and 1 ≦ n <100.

The multi-block copolymer composed of the repeating unit represented by Chemical Formula 1 may include a branched hydrophobic block that does not include acid substituents and a branch that includes an acid substituent (sulfonic acid group, phosphoric acid group, or carboxylic acid group). By polymerizing the branched hydrophilic block, the brancher directly forms the main chain of the copolymer without performing post-treatment acid introduction reaction or cross-linking of the polymer having an acid substituent. Can be done.

In this case, the repeating unit of Formula 1 is a branched hydrophobic block for maintaining the mechanical density of the thin film and branched hydrophilic block for imparting ion conductivity to the thin film are alternately connected through a chemical bond. Therefore, while having high hydrogen ion conductivity, not only the mechanical properties are excellent and chemically stable, but also the distribution, position, number, etc. of the acid substituents in the polymer skeleton can be easily controlled. There is an advantage that the electrolyte membrane can be configured without deterioration.

Method for producing a multi-block copolymer consisting of a repeating unit represented by the formula (1) is described in detail in Korean Patent Application No. 2004-110487.

The content range of the carbon nanoparticles in the composite electrolyte membrane of the present invention is not particularly limited as long as it is a range capable of exhibiting high hydrogen ion conductivity while forming a membrane. For example, 0.0001 to 50% by weight of the composite electrolyte membrane, preferably It may be included in 0.0001 to 10% by weight.

The composite electrolyte membrane of the present invention may include other components, additives, and the like that are known in the art, in addition to the aforementioned components. In addition, the thickness of the composite electrolyte membrane is not particularly limited and can be adjusted within the range to improve the performance and safety of the fuel cell.

The composite electrolyte membrane according to the present invention can be prepared according to conventional methods known in the art. For example, (i) the hydrogen ion conductive polymer or a polymer solution dissolved in a solvent; And mixing the carbon nanotubes to prepare a complex solution thereof. And (ii) forming a film using the complex solution.

The solvent for dissolving the hydrogen ion conductive polymer has a similar solubility index to the polymer to be used and a low boiling point to facilitate uniform mixing and subsequent solvent removal. However, the present invention is not limited thereto, and conventional solvents known in the art may be used. Non-limiting examples of the solvent for dissolving the hydrogen ion conductive polymer is N, N'-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP), dimethyl Sulfoxide (dimethyl sulfoxide, DMSO), or N, N-dimethylformamide (N, N-dimethylformamide, DMF), phosphoric acid, polyphosphoric acid, and the like, these may be used alone or in combination of two or more.

Molding the membrane using the mixture may proceed by coating and drying the mixture on a substrate and then separating the electrolyte membrane from the substrate. Non-limiting examples of the substrate include glass plates, polymer films, stainless steel plates and the like.

The method of coating the mixture on a substrate may use conventional coating methods known in the art, for example, dip coating, die coating, roll coating, comma coating, Various methods, such as a doctor blade or a mixing method thereof, can be used.

Thereafter, the prepared composite electrolyte membrane may be introduced into an acid solution and stirred or heated, whereby the salt in the polymer is converted into an acid, for example, SO ₃ ^- Na ^+, into SO ₃ H form. In other words, it converts the salted hydrophilic part into H-form to act as a conductor. At this time, the type of acid and the heating temperature range is not particularly limited, for example, may be in the range 80 ~ 90 ℃.

The membrane electrode assembly (MEA) of the present invention is a cathode; Anode; And an electrolyte membrane positioned between the cathode and the anode, wherein the electrolyte membrane is a composite electrolyte membrane according to the present invention.

A membrane electrode assembly (MEA) refers to a conjugate of electrodes (cathodes and anodes) in which an electrochemical catalytic reaction between fuel and air occurs and a polymer membrane in which hydrogen ions are transferred, and a single electrode bonded to an electrode (cathodes and anodes) and an electrolyte membrane. It is an integrated unit of. The present invention comprises a carbon nanotube and a hydrogen ion conductive polymer in the electrolyte membrane, thereby constituting a membrane electrode assembly excellent in operating characteristics in low-humidity conditions.

The membrane electrode assembly of the present invention is in a form such that the catalyst layer of the anode and the catalyst layer of the cathode contact the electrolyte membrane, and can be prepared according to conventional methods known in the art. In one example, the cathode; Anode; And it may be prepared by thermal compression at 100 to 400 ℃ in the state in which the electrolyte membrane located between the cathode and the anode in close contact.

In addition, the electrodes (cathode and anode) in the present invention can be prepared according to conventional methods known in the art. For example, a catalyst layer may be formed by applying and drying a catalyst ink including a noble metal catalyst, a hydrogen ion conductive polymer (binder) and a solvent to enhance catalyst dispersion on a gas diffusion layer, and the electrode may be manufactured by the above method. have.

In addition, the present invention provides a fuel cell including the membrane electrode assembly (MEA).

The fuel cell may be manufactured according to conventional methods known in the art using the membrane electrode assembly (MEA) of the present invention. For example, it may be prepared by configuring a membrane electrode assembly (MEA) and a bipolar plate (bipolar plate) prepared above.

The fuel cell may be a polymer electrolyte fuel cell, a direct liquid fuel cell, a direct methanol fuel cell, a direct formic acid fuel cell, a direct ethanol fuel cell, or a direct dimethyl ether fuel cell.

Hereinafter, described in detail through preferred embodiments to help understand the present invention. However, the following examples are merely to illustrate the present invention and the present invention is not limited by the following examples.

EXAMPLE

Example 1 . Preparation of Composite Electrolyte Membrane Blended with Sulfonated Block Copolymer and Carbon Nanotubes

10 g of sulfonated polyether ether ketone block copolymer (a polymer prepared according to Examples 2 and 5 in Korean Patent Application No. 10-2004-0110487) was prepared by dimethylformamide (DMF) 90 After dissolving in g, the solution was filtered through a BORU glass filter (pore size 3) to remove dust and the like.

A blend solution was prepared by dispersing 0.1 wt% of carbon nanotubes (diameter 50 nm, J. Co., Ltd.) in the polymer solution.

The blend solution was poured onto a glass substrate, a solution poured onto the glass substrate with a film applicator was applied, and the solution was dried in an oven at 80 ° C. for at least 2 hours to prepare a composite electrolyte membrane having a thickness of 50 μm.

Example 2. Composite electrolyte membrane using membrane blended sulfonated block copolymer and carbon nanotube and polyethylene microporous membrane

The reinforcement-composite electrolyte membrane was prepared using the blend solution prepared in Example 1 and a polyethylene microporous membrane.

The blend solution was poured onto a glass substrate, applied with a film applicator and poured onto the glass substrate, and then the solution was dried in an oven at 80 ° C. for at least 2 hours, and the polyethylene porous membrane was spread thereon. Then, the blend solution is poured onto the polyethylene porous membrane and the solution poured onto the microporous membrane with a film applicator is then dried in an oven at 80 ° C. for at least 2 hours, and then the blend solution is poured onto the film applicator and After applying the solution poured on the microporous membrane, the copolymer solution was dried for 2 hours or more in an oven at 80 ℃ to prepare a composite electrolyte membrane having a thickness of 50 ㎛.

Comparative Example 1 . Preparation of Pure Electrolyte Membrane Using Only Sulfonated Block Copolymer

After dissolving 10 g of the block copolymer used in Example 1 in 90 g of dimethylformamide (DMF), the solution was filtered through a BORU glass filter (pore size 3) to remove dust and the like.

The polymer solution was poured onto a glass substrate, a solution poured onto the glass substrate with a film applicator was applied, and the solution was dried in an oven at 80 ° C. for at least 2 hours to prepare a pure electrolyte membrane having a thickness of 50 μm.

Experimental Example

For the composite electrolyte membranes prepared in Examples 1 and 2 and the electrolyte membrane prepared in Comparative Example 1, ion exchange capacity (IEC, I on E xchange C apacity), mechanical properties, methanol permeability, Dimensional stability and the like were measured.

Experimental Example 1 . Ion Exchange Capacity (IEC) and Mechanical Properties

0.5 g of the electrolyte membranes prepared in Examples 1, 2 and Comparative Example 1, respectively, were hydrated in ultrapure water at 100 ° C. for 2 hours and then immersed in 100 mL of saturated NaCl aqueous solution for 10 hours or more to form hydrogen ions (H ⁺ ). Substituted by (Na ⁺ ).

The substituted hydrogen ions (H ⁺ ) were titrated with 0.1 N NaOH standard solution, and the IEC value of the polymer membrane was calculated from the amount of NaOH used in the titration according to Equation 1 below, and the results are shown in Table 1 below. . The IEC value of Nafion 115 manufactured by DuPont was presented as a comparative value.

IEC (-SO ₃ H mequiv./g) = (consumed NaOH standard solution (mL) × 0.1N) / weight of dried thin film (g)

Mechanical strength of the electrolyte membrane was measured by Zwick® UTM. A dog-bone type film satisfying ASTM D-882 (Standard Test Method for Tensile Properties of Thin Plastic Sheeting) was prepared from each of the electrolyte membranes of Examples 1, 2 and Comparative Example 1 at room temperature and 25% humidity. After measuring the crosshead speed 5 times each at 50 mm / min, the average value of the tensile strength is shown in Table 1.

division Ion exchange capacity (meq./g) Apparent properties Tensile Strength (Mpa) Elongation (%) Example 1 1.38 Transparent (black), excellent 85 19 Example 2 1.35 Transparent (black), excellent 90 21 Comparative Example 1 1.41 Transparent, excellent 70 14 Nafion 112 0.91 Transparent, excellent 43 225

Through Table 1, the composite electrolyte membranes of Examples 1 and 2 prepared according to the present invention have a smaller decrease in IEC than the electrolyte membrane prepared in Comparative Example 1, whereas the electrolyte membranes prepared in Comparative Example 1 Tensile strength was about 20 to 30%, and elongation was about 30 to 50%.

Experimental Example 2 . Methanol permeability (MeOH crossover)

The methanol permeability of the electrolyte membranes prepared in Examples 1, 2 and Comparative Example 1, respectively, was measured using a diffusion cell device.

First, a methanol aqueous solution of a left cell 10 M, the right cell, into the pure water was placed into the above prepared in the middle of the cell, the electrolyte membrane, the methanol concentration in the right cell, according to time (t) obtained while sampling the solution in the right cell The methanol permeability was calculated from the change in ( C _i ( t )).

At this time, the methanol permeability (D _i · K _i) is to the electrolyte thickness (L) with the film exposure area (A) value, the volume (V), and methanol to the initial concentration (C _i0) value of the left cell of the right cell expression Calculated by 2 and the results are shown in Table 2 below, methanol permeability value of Nafion 115 was presented as a comparison value.

_{C i (t) = {(} A · D i · K i · C io) / V · L} × t

division Example 1 Example 2 Comparative Example 1 Nafion 112 Methanol Permeability (10 ^-6 * cm ² / sec) 1.2 0.9 1.8 2.4

Through Table 2, the composite electrolyte membranes of Examples 1 and 2 prepared according to the present invention had a lower methanol permeability than the electrolyte membrane prepared in Comparative Example 1, and methanol barrier properties were compared with those of Nafion used in conventional polymer membranes. It was confirmed that the improvement was very excellent.

Experimental Example 3. Cell performance analysis

Using the electrolyte membrane prepared in Example 1 and Comparative Example 1 was configured a unit cell cell of DMFC (direct methanol fuel cell), and the durability of the cell was confirmed.

Arbin's DMFC test station was used and the cell temperature was 80 ° C, the cell effective area was 9 cm ² , 0.3 M MeOH 3 mL / min, and the air was supplied at a rate of 200 sccm, 80 mA / Measured in cm ² . The results are shown in FIG.

According to FIG. 1, the cell using the electrolyte membrane prepared in Comparative Example 1 (Comparative Example 1) showed a performance of 0.5V at 80 mA / cm ² , but dropped to 0.35V after 1200 hours of driving. On the other hand, since the cell (Example 1) using the electrolyte membrane prepared in Example 1 exhibited 0.4V after driving for 1200 hours, it was confirmed that the electrolyte membrane prepared in Comparative Example 1 exhibited more stable and superior performance. That is, when the cells using the electrolyte membranes prepared in Example 1 and Comparative Example 1 were respectively driven for the same time, the cells using the electrolyte membrane prepared in Example 1 trapped hydroxy radicals in the carbon nanotubes included in the electrolyte membrane. In order to prevent decomposition of the electrolyte membrane, the performance decrease was less than that of the cell using the electrolyte membrane prepared in Comparative Example 1, and durability was improved.

The composite electrolyte membrane of the present invention can prevent the decomposition of the membrane in advance by removing hydroxy radicals that can be generated during operation of the fuel cell, and can prevent the aging of the electrolyte membrane. In addition, even under low-humidity conditions, high hydrogen ion conductivity and cell performance may be realized to exhibit stable performance even at high temperatures, fuel crossover is suppressed, and mechanical strength may be improved. In addition, the membrane electrode assembly and the fuel cell of the present invention including such a composite electrolyte membrane can implement improved performance in the above-mentioned range.

Although described in detail above with reference to the specific embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention, and such variations and modifications belong to the appended claims. It is also natural.

Claims (13)

Hydrogen ion conductive polymer; And an electrolyte membrane comprising carbon nanotubes dispersed in the matrix of the hydrogen ion conductive polymer, The carbon nanotube is a composite electrolyte membrane, characterized in that to remove the hydroxy radicals generated by the crossover (crossover) of the fuel gas. The method of claim 1, wherein the carbon nanotubes absorb the hydroxy radicals therein, and the hydroxy radicals absorbed into the carbon nanotubes are combined with carbon nanotubes or with impurities contained in the carbon nanotubes. Composite electrolyte membrane, characterized in that to be removed. The composite electrolyte membrane of claim 1, wherein the electrolyte membrane is stacked on one or both surfaces of the microporous membrane. The composite electrolyte membrane of claim 3, wherein the microporous membrane is at least one selected from the group consisting of a polypropylene porous membrane, a polyethylene porous membrane, and a polyolefin porous membrane. The composite electrolyte membrane of claim 1, wherein the carbon nanotubes have a length of 10 to 5000 nm, an outer diameter of 2 to 50 nm, and an inner diameter of 1 to 40 nm. The composite electrolyte membrane of claim 1, wherein the carbon nanotubes are present in an amount of 0.0001 to 50% by weight in the composite electrolyte membrane. The method of claim 1, wherein the hydrogen ion conductive polymer is polyarylene ether (PAE), polyether ether ketone (PEEK), polyether ether sulfone (PEES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride ( PVDF), Nafion, Polyazole, Polyvinyl Alcohol (PVA), Polyphenylene Oxide, Polyphenylene Sulphide, Polysulfone, Polycarbonate, Polystyrene, Polyimide, Polyamide, Polyquinoxaline, Polyphosphazene And polybenzimidazole. The composite electrolyte membrane, characterized in that at least one selected from the group consisting of. The composite electrolyte membrane of claim 7, wherein the hydrogen ion conductive polymer has at least one hydrogen ion exchange group selected from the group consisting of sulfonic acid groups, phosphoric acid groups, hydroxyl groups, and carboxylic acid groups. The composite electrolyte membrane of claim 1, wherein the hydrogen ion conductive polymer is a multi-block copolymer made of a repeating unit represented by the following Chemical Formula 1. 3. [Formula 1]

In Chemical Formula 1, A, X, and Y are each independently

,

,

,

,

,

, ,

,

,

,

,

, or

And wherein R is —NO ₂ or —CF ₃ ; Z is

, ,

,

,

,

, or

And (wherein, Q is ^{_{-SO 3 H, -SO 3 - M}} +, -COOH, -COO - M +, -PO 3 H 2, -PO 3 H - M +, or -PO ₃ ^2- 2M ^+, and , M is Na or K); B is

,

,

, or

ego; G is X and G 'is Z; b / a is 0 <b / a <1 and d / c is 0 <d / c <1; 1 ≦ m <100 and 1 ≦ n <100. The composite electrolyte membrane of claim 9, wherein the repeating unit of Chemical Formula 1 polymerizes the branched hydrophobic block and the branched hydrophilic block so that the branched hydrophobic block and the branched hydrophilic block are alternately connected by chemical bonds. Cathode; Anode; And a composite electrolyte membrane according to any one of claims 1 to 10, positioned between the cathode and the anode. A fuel cell comprising the membrane electrode assembly of claim 11. 13. The fuel cell of claim 12, wherein the fuel cell is a polymer electrolyte fuel cell, a direct liquid fuel cell, a direct methanol fuel cell, a direct formic acid fuel cell, a direct ethanol fuel cell, or a direct dimethyl ether fuel cell.

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