KR102414956B1 - Metal Boride based antioxidant for polymer electrolyte membrane for fuel cell and Method for making the same - Google Patents

Abstract

The present invention relates to an antioxidant for improving the chemical durability of a polymer electrolyte membrane fuel cell (PEMFC) and a manufacturing method thereof, and specifically, to a metal boron compound-based antioxidant that prevents chemical deterioration of a polymer electrolyte membrane for a fuel cell and has increased radical antioxidant ability.

Description

Metal boride based antioxidant for polymer electrolyte membrane for fuel cell and Method for making the same

The present invention relates to a fuel cell. More specifically, it relates to an electrolyte membrane used in a fuel cell. More specifically, it relates to an antioxidant used in an electrolyte membrane for a fuel cell.

A fuel cell is a power generation device that produces electricity by an electrochemical reaction between hydrogen and oxygen in the air, and is well known as an eco-friendly next-generation energy source with high power generation efficiency and no emission other than water. In particular, a polymer electrolyte membrane fuel cell (PEMFC) generally operates at a temperature of 95° C. or less and can obtain high power density.

The electricity generation reaction of the fuel cell is a membrane-electrode assembly (MEA) composed of a perfluorinated sulfonic acid ionomer-based electrolyte membrane and an anode/cathode electrode. ), the hydrogen supplied to the anode, which is the oxidation electrode of the fuel cell, is separated into hydrogen ions (protons) and electrons (electrons). In the cathode, oxygen molecules, hydrogen ions, and electrons react together to generate electricity and heat, and water (H ₂ O) is produced as a reaction by-product.

), 히드로페록실 라디칼(

) 등과 같은 산소 함유 라디칼들을 생성하게 된다. 이러한 라디칼은 과불소 술폰산계 전해질막을 공격하여 막의 화학적 열화를 유발하여 결국 연료전지의 내구성 저하 등의 악영향을 미치게 된다.

In general, hydrogen and oxygen in the air, which are reactive gases of a fuel cell, cross-migrate through the electrolyte membrane to promote the generation of hydrogen peroxide (HOOH), which is a hydroxyl radical (

), the hydroperoxyl radical (

) and oxygen-containing radicals. These radicals attack the perfluorinated sulfonic acid-based electrolyte membrane and cause chemical deterioration of the membrane, which eventually adversely affects the durability of the fuel cell, such as deterioration.

Conventionally, as a technique for alleviating the chemical deterioration of the electrolyte membrane, a method of adding various kinds of antioxidants to the electrolyte membrane has been proposed.

Korean Patent Laid-Open No. 2021-0120206 discloses a highly antioxidant antioxidant for a fuel cell comprising a sulfur-containing organic compound adsorbed to a metal oxide, wherein the sulfur-containing organic compound includes a sulfinate anion group.

Korean Patent Laid-Open No. 2020-0114511 discloses a method for manufacturing an antioxidant for fuel cells by heat-treating samarium-doped cerium oxide.

Korean Patent Laid-Open No. 2021-0132807 discloses an antioxidant for fuel cells comprising cerium oxide doped with a doping element selected from the group consisting of a transition metal element, a post-transition metal element, a lanthanide element, and combinations thereof. do.

Korean Patent Laid-Open No. 2020-0006387 discloses an antioxidant for an electrolyte membrane of a fuel cell comprising silicon dioxide, a support in the shape of a nanotube, and a metal oxide supported on the support.

As one of the important components in order to alleviate the chemical deterioration of the electrolyte membrane for fuel cells, metal oxide is used as an antioxidant. A typical example of the metal oxide is cerium oxide, which is dissolved as cerium ions in the polymer electrolyte solution and oxidizes the electrode layer, causing fatal failure. That is, since cerium oxide has poor antioxidant properties, it adversely affects the stability of the electrolyte membrane and shortens the lifespan of the fuel cell.

Therefore, in order to solve the above problems, the present inventors have prepared a metal boron compound system of the present invention that has excellent antioxidant properties and acid resistance, but does not dissolve in the polymer electrolyte solution, thereby ensuring stability and maintaining overall performance by maintaining ionic conductivity. (Metal boride based) It has come to develop an antioxidant.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel antioxidant for fuel cells that can significantly improve antioxidant capacity and chemical durability.

Another object of the present invention is to provide an antioxidant for a fuel cell that is not soluble in a polymer electrolyte solution and can ensure stability.

Another object of the present invention is to provide an antioxidant for a fuel cell capable of maintaining ionic conductivity to maintain overall performance.

Another object of the present invention is to provide an electrolyte membrane for a fuel cell that is impregnated with the antioxidant to improve antioxidant properties, acid resistance and stability, and maintain ionic conductivity.

Another object of the present invention is to provide a membrane-electrode assembly made of the electrolyte membrane.

Another object of the present invention is to provide a fuel cell manufactured with the membrane-electrode assembly.

The above objects of the present invention can all be achieved by the present invention described below and are not limited to the above-mentioned objects.

The antioxidant for a fuel cell of the present invention is a metal boron compound doped with a boron compound with a metal precursor having a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, and is expressed by the following Chemical Formula 1 or Chemical Formula 2 characterized by being

[Formula 1]

M _x Ce _1-x B _i

[Formula 2]

M _x B _i

In Formulas 1 and 2, M is a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, 0<x≤0.5, and i is a number from 1 to 8.

The transition metal element is manganese (Mn), cobalt (Co), molybdenum (Mo), iron (Fe), yttrium (Y), zirconium (Zr), tungsten (W), chromium (Cr), niobium (Nb) , hafnium (Hf), and combinations thereof.

The lanthanide elements include cerium (Ce), praseodymium (Pr), neodymium (Nd), Pm (promethium), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy) and It is selected from the group consisting of combinations thereof.

The boron compound is lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), beryllium borohydride (Be(BH ₄ ) ₂ ), magnesium borohydride (Mg(BH ₄ ) ₂ ) ), aluminum borohydride (Al(BH ₄ ) ₃ ) and at least one boron compound selected from the group consisting of combinations thereof.

The method for preparing the antioxidant of the electrolyte membrane of the present invention comprises the steps of dissolving a metal precursor and a boron compound in a solvent to prepare a mixture; homogenizing the mixture by stirring or sonicating; and drying the homogenized mixture.

The metal precursor includes a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof.

The solvent is 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bromide, 1-octyl-3 methylimida Zolium bromide, 1-decyl-3-methylimidazolium bromide, 1-dodecyl-3-methyl-docelyimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 1,3-di (N,N-dimethylaminoethyl)-2-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 4-methyl-N-butyl-pyridinium imidazolium bromide, N-octyl It is selected from the group consisting of pyridiniumimidazolium bromide or a combination thereof.

In the step of obtaining the metal boron compound, the stirring or ultrasonication is performed for 30 minutes to 1 hour.

In the step of drying the metal boron compound, the drying may be performed at a temperature of 600° C. to 1000° C. for 3 to 24 hours.

The antioxidant for a metal boron compound-based fuel cell prepared as described above may be used by being impregnated in an electrolyte membrane containing an ionomer. Accordingly, the electrolyte membrane of the present invention includes the ionomer and the antioxidant.

The electrolyte membrane includes one selected from the group consisting of perfluorinated sulfonic acid-based ionomers, hydrocarbon-based ionomers, and mixtures thereof.

The electrolyte membrane contains 50 ppm to 250,000 ppm of antioxidant.

Furthermore, the electrolyte membrane impregnated with the antioxidant may be used in a membrane-electrode assembly, and the membrane-electrode assembly of the present invention includes an electrolyte membrane including the antioxidant; a pair of electrodes provided on both sides of the electrolyte membrane; Including, the membrane-electrode assembly may be used in a fuel cell.

Hereinafter, the specific content of the present invention will be described in detail.

The present invention provides a novel antioxidant for fuel cells that greatly improves antioxidant ability and chemical durability and maintains ionic conductivity, an electrolyte membrane including the antioxidant, a membrane-electrode assembly including the electrolyte membrane, and the membrane-electrode assembly It has the effect of the invention to provide a fuel cell comprising. The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a color photograph showing the antioxidant properties of antioxidants according to Examples 1-5 and Comparative Examples 1-2 of the present invention through a methyl violet (MV) technique.
2 is a fluorine ion release rate (FER) results of electrolyte membranes according to Examples 1-5 and Comparative Examples 3-4 of the present invention.
3 is a result of measuring the proton conductivity of the electrolyte membrane at 80 °C at 100% relative humidity according to Example 1 and Comparative Examples 3-4 of the present invention.

The present invention relates to an antioxidant for a fuel cell for scavenging radicals that reduce the durability of a fuel cell by attacking a perfluorinated sulfonic acid-based electrolyte membrane and causing chemical deterioration of the membrane, comprising a transition metal element, a lanthanide element, and a combination thereof. It is characterized in that it comprises a metal boron compound doped with a boron compound to a metal precursor having a metal element selected from the group.

Unlike the conventional cerium oxide antioxidants that dissolve as ions in the electrolyte solution and cause fatal fuel cell failure, the metal boron compound-based antioxidants for fuel cells do not dissolve even in the electrolyte solution, so it is an antioxidant that improves the durability of the fuel cell. . Hereinafter, an antioxidant for a polymer electrolyte membrane fuel cell, a method for manufacturing the antioxidant, an electrolyte membrane for a fuel cell including the antioxidant, a membrane-electrode assembly and a fuel cell including the antioxidant according to an embodiment of the present invention will be described.

antioxidant

The antioxidant for fuel cell of the present invention is a metal boron compound doped with a boron compound with a metal precursor having a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, represented by the following Chemical Formula 1 or Chemical Formula 2 characterized in that

[Formula 1]

M _x Ce _1-x B _i

[Formula 2]

M _x B _i

In Formulas 1 and 2, M is a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, 0<x≤0.5, and i is a number from 1 to 8.

wherein i is a value for making the compounds of Chemical Formulas 1 and 2 electrically neutral.

The transition metal element is manganese (Mn), cobalt (Co), molybdenum (Mo), iron (Fe), yttrium (Y), zirconium (Zr), tungsten (W), chromium (Cr), niobium (Nb) , hafnium (Hf), and includes at least one element selected from the group consisting of combinations thereof.

The lanthanide elements include cerium (Ce), praseodymium (Pr), neodymium (Nd), Pm (promethium), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy) and and at least one element selected from the group consisting of combinations thereof.

The boron compound is lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), beryllium borohydride (Be(BH ₄ ) ₂ ), magnesium borohydride (Mg(BH ₄ ) ₂ ) ), aluminum borohydride (Al(BH ₄ ) ₃ ) and at least one boron compound selected from the group consisting of combinations thereof.

Antioxidant manufacturing method

The manufacturing method of the antioxidant of the present invention comprises the steps of preparing a mixture by dissolving a metal precursor and a boron compound in a solvent; homogenizing the mixture by stirring or sonicating; and drying the homogenized mixture.

In the step of preparing a mixture by dissolving the metal precursor and the boron compound in a solvent, the metal precursor includes a metal selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof. On the other hand, the solvent is 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bromide, 1-octyl-3 methyl imidazolium bromide, 1-decyl-3-methylimidazolium bromide, 1-dodecyl-3-methyl-docesylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 1,3 -di(N,N-dimethylaminoethyl)-2-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 4-methyl-N-butyl-pyridinium imidazolium bromide, N -Octylpyridinium imidazolium bromide or a combination thereof is selected from the group consisting of the metal precursor and the boron compound serves to help to be easily dispersed and homogenized. In order to improve this effect, the viscosity may be adjusted by adding isopropyl alcohol or the like to the solvent.

Then, the prepared mixture is stirred or sonicated to obtain a metal boron compound in which a metal precursor is doped with a boron compound. The reason for the stirring or ultrasonic treatment is also to more carefully homogenize the mixture to obtain a metal boron compound. At this time, the stirring or ultrasonic treatment is performed for 30 minutes to 1 hour.

Finally, in the step of drying the metal boron compound, it is carried out at a temperature of 600° C. to 1000° C. for 3 to 24 hours. In this high-temperature combustion process, all the by-products are decomposed due to combustion, thereby eliminating the need for a filtering process that is normally performed to form metal oxides.

electrolyte membrane

The antioxidant of the present invention is impregnated into an electrolyte membrane for a fuel cell and used to improve the acid resistance and durability of the fuel cell. In addition, as an electrolyte membrane for a fuel cell, an ionomer, which is an ionic copolymer that functions as a physical crosslinking, is used. That is, the ionomer transfers hydrogen ions to the inside of the catalyst layer and acts as an adhesive to attach the catalyst layers to each other.

The electrolyte membrane is characterized in that it includes a perfluorine sulfonic acid-based ionomer, a hydrocarbon-based ionomer, and a mixture thereof.

The electrolyte membrane preferably contains 50 ppm to 250,000 ppm of the antioxidant, wherein the content of the antioxidant is based on the dry weight of the electrolyte membrane. That is, the antioxidant is included in an amount of 50 ppm to 250,000 ppm based on the weight of the ionomer included in the electrolyte membrane. Preferably, the antioxidant is included in the range of 500 ppm to 125,000 ppm. If the content of the antioxidant is less than 50 ppm, the effect of improving the chemical durability of the electrolyte membrane by the antioxidant may be insignificant. This lowering problem may occur.

Membrane-electrode assembly and fuel cell

The membrane-electrode assembly for a fuel cell of the present invention includes an electrolyte membrane and a pair of electrodes provided on both surfaces of the electrolyte membrane, and the electrolyte membrane is characterized in that it includes an antioxidant. On the other hand, the fuel cell of the present invention is characterized in that it includes a membrane-electrode assembly to which an antioxidant is applied.

Hereinafter, the present invention will be described in more detail through specific examples. However, these examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

Cerium boron compound (CeB ₆ ) antioxidants and an electrolyte membrane comprising the same

In a solvent whose viscosity was adjusted by adding 2 ml of isopropyl alcohol to 3 g of 1-butyl-3-methylimidazolium bromide in an alumina crucible, cerium (III) chloride (CeCl ₃ ) and sodium borohydride ( NaBH ₄ ) was added and dissolved so that the molar ratio of cerium: boron was 1:12. Then, it was homogenized by ultrasonication for 30 minutes to obtain a homogeneous solution, and then the homogenized mixture was heated at 800° C. for 4 hours to obtain an antioxidant. Phosphorus cerium boron compound particles were obtained.

The electrolyte membrane impregnated with the antioxidant was synthesized using a solution casting technique. As the electrolyte solution, a Nafion solution, which is a perfluorinated sulfonic acid-based ionomer dispersion (D521), was used. Nafion (Nafion) solution was taken and the desired volume of N,N-dimethylmethanamide (N,N-dimethylmethanamide) (DMF) was added thereto. Then, 1wt% of CeB ₆ nanoparticles of the solution were dispersed and After sonicating and carefully mixing for 2 hours, the mixture was stirred for 8 hours to form a slurry. The slurry was then cast using a 30 μm thick doctor blade and dried by heating.

Manganese boron compound (MnB ₂ ) antioxidant and electrolyte membrane containing the same

In a solvent whose viscosity was adjusted by adding 2 ml of isopropyl alcohol to 3 g of 1-butyl-3-methylimidazolium bromide in an alumina crucible, manganese(II) chloride (MnCl ₂ ) and sodium borohydride ( NaBH ₄ ) was added and dissolved so that the molar ratio of manganese: boron was 1:8. Then, it was homogenized by ultrasonication for 30 minutes to obtain a homogeneous solution, and then the homogenized mixture was heated at 700° C. for 4 hours to obtain antioxidants. Phosphorus manganese boron compound particles were obtained.

The electrolyte membrane impregnated with the antioxidant was synthesized using a solution casting technique. As the electrolyte solution, a Nafion solution, which is a perfluorinated sulfonic acid-based ionomer dispersion (D521), was used. Nafion (Nafion) solution was taken and the desired volume of N,N-dimethylmethanamide (N,N-dimethylmethanamide) (DMF) was added thereto. Then, 1wt% of CeB ₆ nanoparticles of the solution were dispersed and After sonicating and carefully mixing for 2 hours, the mixture was stirred for 8 hours to form a slurry. The slurry was then cast using a 30 μm thick doctor blade and dried by heating.

Molybdenum boron compound (MoB ₄ ) antioxidant and electrolyte membrane containing the same

In a solvent whose viscosity was adjusted by adding 2 ml of isopropyl alcohol to 3 g of 1-butyl-3-methylimidazolium bromide in an alumina crucible, molybdenum chloride (V) (MoCl ₅ ) and sodium borohydride ( NaBH ₄ ) was added and dissolved so that the molybdenum: boron molar ratio was 1:12. After that, it was homogenized by ultrasonication for 30 minutes to obtain a homogeneous solution, and then the homogenized mixture was heated at 800° C. for 4 hours to obtain an antioxidant. Phosphorus molybdenum boron compound particles were obtained.

The electrolyte membrane impregnated with the antioxidant was synthesized using a solution casting technique. As the electrolyte solution, a Nafion solution, which is a perfluorinated sulfonic acid-based ionomer dispersion (D521), was used. Nafion (Nafion) solution was taken and the desired volume of N,N-dimethylmethanamide (N,N-dimethylmethanamide) (DMF) was added thereto. Then, 1wt% of CeB ₆ nanoparticles of the solution were dispersed and After sonicating and carefully mixing for 2 hours, the mixture was stirred for 8 hours to form a slurry. Then, the slurry was cast using a 30 μm thick doctor blade and dried by heating.

Manganese-cerium boron compound (Mn _It's Ce _1-i Bx) antioxidant and electrolyte membrane comprising same

In a solvent whose viscosity was adjusted by adding 2 ml of isopropyl alcohol to 3 g of 1-butyl-3-methylimidazolium bromide in an alumina crucible, cerium (III) chloride (CeCl ₃ ), manganese (II) chloride ) (MnCl ₂ ) and sodium borohydride (NaBH ₄ ) were added and dissolved so that a molar ratio of cerium:manganese:boron was 0.5:0.5:12. After that, it was homogenized by ultrasonication for 30 minutes to obtain a homogeneous solution. The homogenized mixture was heated at 800° C. for 4 hours to obtain antioxidant manganese-cerium boron compound particles.

The electrolyte membrane impregnated with the antioxidant was synthesized using a solution casting technique. As the electrolyte solution, a Nafion solution, which is a perfluorinated sulfonic acid-based ionomer dispersion (D521), was used. Nafion (Nafion) solution was taken and the desired volume of N,N-dimethylmethanamide (N,N-dimethylmethanamide) (DMF) was added thereto. Then, 1wt% of CeB ₆ nanoparticles of the solution were dispersed and After sonicating and carefully mixing for 2 hours, the mixture was stirred for 8 hours to form a slurry. Then, the slurry was cast using a 30 μm thick doctor blade and dried by heating.

Molybdenum-cerium boron compound (Mo _It's Ce _1-i Bx) antioxidant and electrolyte membrane comprising same

In a solvent whose viscosity is adjusted by adding 2 ml of isopropyl alcohol to 3 g of 1-butyl-3-methylimidazolium bromide in an alumina crucible, cerium (III) chloride (CeCl ₃ ), molybdenum chloride (V ) (MoCl ₅ ) and sodium borohydride (NaBH ₄ ) were added and dissolved so that the molar ratio of cerium: molybdenum: boron was 0.5: 0.5: 12. After that, it was homogenized by ultrasonication for 30 minutes to obtain a homogeneous solution. The homogenized mixture was heated at 800° C. for 4 hours to obtain the antioxidant molybdenum-cerium boron compound particles.

The electrolyte membrane impregnated with the antioxidant was synthesized using a solution casting technique. As the electrolyte solution, a Nafion solution, which is a perfluorinated sulfonic acid-based ionomer dispersion (D521), was used. Nafion (Nafion) solution was taken and the desired volume of N,N-dimethylmethanamide (N,N-dimethylmethanamide) (DMF) was added thereto. Then, 1wt% of CeB ₆ nanoparticles of the solution were dispersed and After sonicating and carefully mixing for 2 hours, the mixture was stirred for 8 hours to form a slurry. The slurry was then cast using a 30 μm thick doctor blade and dried by heating.

Comparative Example 1

The methyl violet test solution itself, which does not contain a separate antioxidant, was used.

Comparative Example 2

A methyl violet test solution containing ceria (CeO ₂ ) as an antioxidant was used.

Comparative Example 3

In Comparative Example 1, the same sulfonic acid-based ionomer dispersion (Nafion solution) as in Example 1 was added and mixed, followed by casting and drying to prepare an electrolyte membrane.

Comparative Example 4

The cerium oxide particles were prepared by co-precipitation using cerium nitrate and ammonium hydroxide as precipitating agents. Cerium nitrate brine (Ce(NO ₃ ) ₃ .6H ₂ O) was added to 50 ml of distilled water (DI) to make the total concentration of the solution 0.1 mol, and then stirred for 30 minutes to completely dissolve the cerium salt in deionized water. Next, after adjusting the hydrogen ion concentration to pH9 using an ammonium hydroxide (NH ₄ OH) solution, the mixture was stirred at 60° C. for additional 2 hours. The solvent was volatilized through the stirring to obtain a cerium oxide precipitate, which is Comparative Example 2 of the present invention. The precipitate was washed with ethanol three times, filtered, and then the obtained powder was dried in an oven at 80° C. for about 24 hours to obtain cerium oxide particles.

The electrolyte membrane impregnated with the cerium oxide was prepared in the same manner as in Examples 1 to 5.

Physical property measurement and property evaluation

Antioxidant Assessment - Methyl Violet Test

The methyl violet technique is a fast and effective method to evaluate the radical scavenging properties of a material by visual inspection of color change of methyl violet dye by mixing methyl violet with iron sulfate hydrate, hydrogen peroxide, deionized water and antioxidants.

The higher the antioxidant property, the better the purple color of methyl violet is maintained.

In the present invention, in order to evaluate the antioxidant properties of the antioxidants according to Example 1-5 and Comparative Example 1-2, 1.2 x 10-5 M MV (methyl violet), 0.15 mM iron (II) sulfate heptahydrate (FeSO ₄ 7H ₂ O) of Fenton's reagent, 1.0 MH ₂ O ₂ , 0.1 M Tris-HCl buffer (pH 4.7), and appropriate CeO ₂ or metal boron compound to a final volume of 10 mL, and left at room temperature for at least 5 minutes The color change was observed. The result is shown in FIG. 1 .

As shown in FIG. 1, S1 (Comparative Example 1) of FIG. 1 was almost colorless with the methyl violet test solution to which only Fenton reagent was added without a separate antioxidant, and S2 in FIG. 1 (Comparative Example 2) ), it can be seen that the methyl violet test solution containing ceria (CeO ₂ ) has a pale purple color.

On the other hand, in FIG. 1, S3 is a cerium boron compound (Example 1), S4 is a manganese boron compound (Example 2), S5 is a molybdenum boron compound (Example 3), and S6 is a manganese-cerium boron compound (Example 4) , S7 is the methyl violet test result containing the molybdenum-cerium boron compound (Example 5), and the methyl violet test solution containing the metal boron compound antioxidant of Examples 1-5 showed that the purple retention properties were improved with the naked eye. Able to know.

Accordingly, it can be confirmed that the antioxidant properties of the molybdenum (Mo), manganese (Mn), and cerium (Ce)-based boron compounds according to Examples 1-5 of the present invention can be greatly improved.

Long-Term Durability Assessment - Fluoride Ion Release Rate Analysis (FER)

In order to verify the chemical durability of the electrolyte membranes of Examples 1 to 5, the perfluorine-based ionomer was reacted with a Fenton solution to measure a fluorine emission rate (FER) and compared with Comparative Examples 3 and 4 The antioxidant expression properties of the antioxidants added to it were compared and verified.

In order to evaluate the chemical durability by cutting the electrolyte membrane prepared as described above, deionized water and hydrogen peroxide were prepared by mixing in a weight ratio of 1:0.43, and 10 ppm of iron sulfate heptahydrate was added to prepare the Fenton solution of the Examples and Comparative Examples. Prepared according to the number.

The electrolyte membranes of Examples 1 to 5 and Comparative Examples 3 to 4 were immersed in Fenton solution, reacted at 80° C., and the experiment was conducted for 10 days. According to the reaction between the fenton solution and the electrolyte membrane, the electrolyte membrane is decomposed by radicals contained in the fenton solution to release fluoride ions (F ^- ). Durability and stability were compared and verified.

The results for the above experiment are shown in FIG. 2 . Based on the 10-day reaction time results, the fluoride ion release concentration follows the following trend:

Nafion (Comparative Example 3) > CeO ₂ (Comparative Example 4) > CeB ₆ (Example 1) > MnB ₂ (Example 2) > MoB ₄ (Example 3) > Mn _i Ce _1-i Bx (Example 4) > Mo _i Ce _1-i Bx (Example 5).

Referring to FIG. 2 , in the case of Example 1, values of about 3.7% of Comparative Example 3 and about 16% of Comparative Example 4 were shown, and in the case of Example 2, the values of Comparative Example 3 It exhibited a value of about 2.4% and about 10% of Comparative Example 4, and in the case of Example 3, about 3% of Comparative Example 3, about 13% of Comparative Example 4, and Comparative Example 3 in Example 4 of about 2%, about 13% of Comparative Example 4, about 2.3% of Comparative Example 3, and about 10% of Comparative Example 4 in Example 5. Through this, it was confirmed that the electrolyte membrane to which the metal boron compound antioxidant added with a boron compound doped with a metal element selected from the group consisting of novel transition metal elements, lanthanide elements, and combinations thereof exhibits excellent chemical durability and stability. .

Ionic Conductivity Assessment

3 shows the pure Nafion membrane of Comparative Example 3 and the Nafion membrane, which is an electrolyte membrane impregnated with ceria (CeO ₂ ) of Comparative Example 4, and Examples 1-3 of 30 μm thick cerium boron compound, manganese boron compound, and molybdenum boron The proton conductivity of the Nafion membrane impregnated with the compound is shown. The conductivity data were performed at 80 °C under 100% relative humidity conditions. Referring to FIG. 3, compared to Comparative Example 3, which is a pure Nafion film, and Comparative Example 4, impregnated with a cerium oxide-based antioxidant, Example 1-3 impregnated with a cerium boron compound, a manganese boron compound, and a molybdenum boron compound antioxidant The degree of decrease of the ionic conductivity of the metal boron compound was low, so that the ionic conductivity of the electrolyte membrane could be maintained, and it was confirmed that the characteristics for maintaining the overall performance were secured.

Therefore, the metal boron compound according to an embodiment of the present invention may have high antioxidant activity, and the electrolyte membrane including the metal boron compound-based antioxidant has excellent long-term durability and stable ionic conductivity.

As described above, the present invention provides a novel antioxidant having excellent antioxidant activity and long-term stability, so that the durability of the membrane-electrode assembly to which the antioxidant is introduced can be greatly improved, and accordingly, such a membrane-electrode assembly Lifespan of a fuel cell comprising

Simple modifications or changes of the present invention can be easily carried out by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (16)

A metal boron compound doped with a boron compound with a metal precursor having a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, and is represented by the following Chemical Formula 1 or Chemical Formula 2 Antioxidant for fuel cells :
[Formula 1]
M _x Ce _1-x B _i
[Formula 2]
M _x B _i
In Formulas 1 and 2, M is a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, 0<x≤0.5, and i is 1 to 8. According to claim 1, wherein the metal precursor comprises a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, wherein the transition metal element is manganese (Mn), cobalt (Co), molybdenum (Mo) ), iron (Fe), yttrium (Y), zirconium (Zr), tungsten (W), chromium (Cr), niobium (Nb), at least one element selected from the group consisting of hafnium (Hf) and combinations thereof An antioxidant for fuel cells, comprising: According to claim 1, wherein the lanthanide element is cerium (Ce), praseodymium (Pr), neodymium (Nd), Pm (promethium), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb) Antioxidant for fuel cell, characterized in that it contains at least one element selected from the group consisting of , dysprosium (Dy), and combinations thereof. According to claim 1, wherein the boron compound is lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), beryllium borohydride (Be(BH ₄ ) ₂ ), magnesium borohydride ( Mg(BH ₄ ) ₂ ), aluminum borohydride (Al(BH ₄ ) ₃ ), and at least one boron compound selected from the group consisting of combinations thereof Antioxidant for fuel cells. preparing a mixture by dissolving a metal precursor and a boron compound in a solvent;
homogenizing the mixture by stirring or sonicating; and
drying the homogenized mixture;
including,
A method for producing an antioxidant for a fuel cell, characterized in that the mixture is represented by the following Chemical Formula 1 or Chemical Formula 2:
[Formula 1]
M _x Ce _1-x B _i
[Formula 2]
M _x B _i
In Formulas 1 and 2, M is a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, 0<x≤0.5, and i is 1 to 8. According to claim 5, wherein the metal precursor comprises a metal element selected from the group consisting of a transition metal element, a lanthanide element, and a combination thereof, wherein the transition metal element is manganese (Mn), cobalt (Co), molybdenum (Mo) ), yttrium (Y), zirconium (Zr), tungsten (W), chromium (Cr), niobium (Nb), hafnium (Hf), characterized in that it contains at least one element selected from the group consisting of A method for manufacturing an antioxidant for fuel cells comprising: According to claim 5, wherein the lanthanide element is cerium (Ce), praseodymium (Pr), neodymium (Nd), Pm (promethium), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb) , Dysprosium (Dy), and a method for producing an antioxidant for a fuel cell comprising at least one element selected from the group consisting of combinations thereof. According to claim 5, wherein the boron compound is lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), beryllium borohydride (Be(BH ₄ ) ₂ ), magnesium borohydride ( Mg(BH ₄ ) ₂ ), aluminum borohydride (Al(BH ₄ ) ₃ ), and a method of manufacturing an antioxidant for fuel cell, characterized in that it contains at least one boron compound selected from the group consisting of combinations thereof. 6. The method of claim 5, wherein the solvent is 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bromide, 1- Octyl-3 methylimidazolium bromide, 1-decyl-3-methylimidazolium bromide, 1-dodecyl-3-methyl-docesylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide ,1,3-di(N,N-dimethylaminoethyl)-2-methylimidazolium bromide, 1-butyl-2,3-dimethylimidazolium bromide, 4-methyl-N-butyl-pyridinium imida A method for producing an antioxidant for a fuel cell, characterized in that it is selected from the group consisting of zolium bromide, N-octylpyridinium imidazolium bromide, or a combination thereof. The method according to claim 5, wherein the homogenizing is performed for 30 minutes to 1 hour. The method of claim 5 , wherein the drying is performed at 600° C. to 1000° C. for 3 to 24 hours. An electrolyte membrane for a fuel cell made of an ionomer and the antioxidant according to any one of claims 1 to 4. The electrolyte membrane according to claim 12, wherein the ionomer is selected from the group consisting of perfluorinated sulfonic acid-based ionomers, hydrocarbon-based ionomers, and mixtures thereof. The electrolyte membrane for a fuel cell according to claim 12, wherein the antioxidant is contained in an amount of 50 ppm to 250,000 ppm. The electrolyte membrane according to claim 12; and
a pair of electrodes provided on both sides of the electrolyte membrane;
Membrane-electrode assembly for fuel cells, characterized in that consisting of. A fuel cell comprising the membrane-electrode assembly according to claim 15.

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