Radical scavenger, manufacturing method therefor, membrane-electrode assembly, and fuel cell

Abstract

Disclosed are a radical scavenger for improving durability, a membrane-electrode assembly, a fuel cell, and methods for manufacturing the foregoing. According to one aspect, provided is a radical scavenger comprising radical-scavenging particles and a protective layer formed on the surfaces of the radical-scavenging particles, wherein a ratio of the standard deviation of thickness to the average thickness of the protective layer is 5 % or less.

Description

Radical scavenger, method for preparing the same, membrane-electrode assembly, and fuel cell

[0001] The present disclosure relates to a radical scavenger, a battery member / component using the same, and a method for manufacturing the same, and more specifically, to a radical scavenger having a protective layer, a membrane-electrode assembly including the same, a fuel cell, and a method for manufacturing the same.

[0002] Fuel cells are power generation systems that convert chemical energy generated by the electrochemical reaction of a fuel (hydrogen, methanol, etc.) and an oxidant (oxygen, air, etc.) into electrical energy. They are being researched as a next-generation energy source due to their high energy efficiency and environmentally friendly characteristics of low pollutant emissions. Fuel cells can be classified into high-temperature and low-temperature fuel cells depending on the application, and can be categorized by the type of electrolyte. High-temperature fuel cells include solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC), while low-temperature fuel cells include alkaline fuel cells (AFC) and polymer electrolyte membrane fuel cells (PEMFC).

[0003] Polymer electrolyte fuel cells (PEMFCs) are attracting attention as portable, automotive, and home power sources due to their advantages: low operating temperatures (below 100°C), the absence of leakage issues due to the use of solid electrolytes, rapid startup and response, and excellent durability. In particular, research is underway into portable fuel cells, as they offer high-power fuel cells with higher current densities than other fuel cells, allowing for miniaturization.

[0004] The unit cell structure of a polymer electrolyte fuel cell can be structured as a membrane-electrode assembly (MEA), with an anode and a cathode coated on either side of an electrolyte membrane made of a polymer material. In other words, the MEA is where the electrochemical reaction between hydrogen and oxygen occurs, and can be composed of an anode, a cathode, and a polymer electrolyte membrane positioned between them.

[0005] Radicals generated at the electrodes during fuel cell operation are known to be a major cause of polymer electrolyte membrane deterioration. Hydrogen peroxide (H2O2) is generated during the reduction reaction of oxygen at the cathode, and the generated hydrogen peroxide can generate hydroperoxyl radicals (OOH·) and hydroxyl radicals (OH·). These radicals cause the deterioration of the ionomer, which is essentially responsible for hydrogen ion transport in the polymer electrolyte membrane, reducing its ionic conductivity and ultimately leading to a decline in fuel cell performance.

[0006] Accordingly, a method has been proposed to prevent deterioration of polymer electrolyte membranes and consequent performance degradation of fuel cells by adding a radical scavenger, a substance that traps radicals, to the polymer electrolyte membrane or electrode layer to remove the generated radicals. The radical scavenger reacts with the radicals generated at the electrode to remove them before they deteriorate the polymer electrolyte membrane.

[0007] However, existing radical scavengers have poor durability. Therefore, as the fuel cell's operating time increases, radical removal may not be adequate, leading to a rapid decline in fuel cell performance. Furthermore, existing radical scavenger particles aggregate with each other, hindering the movement of hydrogen ions, thereby reducing the ionic conductivity of the polymer electrolyte membrane.

[0008] Therefore, there is a need for the development of a radical scavenger and a manufacturing method that can minimize agglomeration between radical scavenger particles while maintaining the radical removal effect of the radical scavenger for a long period of time and have excellent functionality and manufacturing efficiency.

[0009] The technical problem to be achieved by the present invention is to provide a method for manufacturing a radical scavenger capable of improving the durability of the radical scavenger, minimizing agglomeration between radical scavenger particles, and ensuring excellent functionality and manufacturing efficiency, and a radical scavenger manufactured by the method.

[0010] In addition, the technical problem to be achieved by the present invention is to provide a polymer electrolyte membrane, a membrane-electrode assembly (MEA) to which the above-described radical scavenger is applied, and a method for manufacturing the same.

[0011] In addition, the technical problem to be achieved by the present invention is to provide a fuel cell including the above-described membrane-electrode assembly (MEA) and a method for manufacturing the same.

[0012] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0013] According to a first aspect of the present invention, a radical scavenger is provided, comprising a radical-scavenging particle and a protective layer formed on the surface of the radical-scavenging particle, wherein a ratio of a thickness standard deviation to an average thickness of the protective layer is 5% or less.

[0014] According to a second aspect of the present invention, in the first aspect, the protective layer may include a titania layer having a multilayer structure.

[0015] According to a third aspect of the present invention, in the first or second aspect, the protective layer may include at least two of a titania layer, a silica layer, and a carbon-based material layer. Specifically, the protective layer may include a titania layer and a silica layer, and more specifically, may include the titania layer and the silica layer sequentially laminated. Here, since the titania layer, unlike the silica layer, is formed in a structure in which a plurality of particles are clustered, when the titania layer and the silica layer are laminated in that order based on the surface of the radical scavenger particle, the stability or durability of the radical scavenger particle may be further improved.

[0016] In some embodiments, the protective layer having the multilayer structure may include the titania layer, the silica layer, and the carbon-based material layer sequentially laminated on the surface of the radical-trapping particle. According to some embodiments of the present invention, since the protective layer includes the titania layer, the silica layer, and the carbon-based material layer, not only is a synergistic effect exhibited for radical trapping, but the radical scavenger can also be effectively prevented from excessively agglomerated, and stability can be further improved.

[0017] In some embodiments, the protective layer may have a two-layer structure or a three-layer structure.

[0018] According to a fourth aspect of the present invention, in any one of the first to third aspects, the protective layer may have a porous structure. For example, the porosity of the protective layer, as a percentage of the volume of pores with respect to the total volume of the protective layer, may be 1 vol% or more and 15 vol% or less, specifically 1 vol% or more, 2 vol% or more, 3 vol% or more, 4 vol% or more, or 5 vol% or more; and 6 vol% or less, 7 vol% or less, 8 vol% or less, 9 vol% or less, 10 vol% or less, 11 vol% or less, 12 vol% or less, 13 vol% or less, 14 vol% or less, or 15 vol% or less.

[0019] According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the protective layer may have a thickness of 0.05 nm or more and 20 nm or less. For example, the thickness of the protective layer may be 0.05 nm or more, 0.1 nm or more, 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, 1.9 nm or more, 2.0 nm or more, 2.5 nm or more, 3.0 nm or more, 3.5 nm or more, 3.8 nm or more, or 3.9 nm or more; 4.0 nm or less, 5 nm or less, 6 nm or less, 7 nm or less, 8 nm or less, 9 nm or less, 10 nm or less, 11 nm or less, 12 nm or less, 13 nm or less, 14 nm or less, 15 nm or less, 16 nm or less, 17 nm or less, 18 nm or less, 19 nm or less, or 20 nm or less; Or any one or more of the plurality of lower limits may be less than or equal to any one or more of the plurality of upper limits of the number of norths. At least any one or more of the plurality of material layers described herein may have a thickness within the numerical range.

[0020] According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the protective layer may be formed using a vapor adsorption method of vaporizing a given precursor and adsorbing the precursor or a component decomposed from the precursor onto the surface of the radical trapping particle.

[0021] According to a seventh aspect of the present invention, a method for manufacturing a radical scavenger is provided, comprising the steps of: providing a radical-scavenging particle; and forming a protective layer on the surface of the radical-scavenging particle, wherein a vapor adsorption method is used to vaporize a given precursor and adsorb the precursor or a component decomposed from the precursor onto the surface of the radical-scavenging particle, thereby forming the protective layer obtained from the precursor on the surface of the radical-scavenging particle.

[0022] According to the eighth aspect of the present invention, in the seventh aspect, the precursor may have a vaporization temperature of about 60°C or more and 250°C or less.

[0023] According to a ninth aspect of the present invention, in the seventh or eighth aspect, the protective layer may include at least one of titania, silica, and a carbon-based material, specifically, may include two or more of titania, silica, and a carbon-based material, and more specifically, may include titania and silica, or may include titania, silica, and a carbon-based material. Meanwhile, in the general fuel cell field, titania can be used as a catalyst for an electrochemical reaction or can perform a function of preventing self-humidification or methanol crossover. In addition, silica can be used as a hygroscopic material, and the carbon-based material can perform a function of stably positioning functional particles. According to some embodiments of the present invention, by including titania and silica, or titania, silica, and a carbon-based material, not only a synergistic effect for radical capture is exhibited, but also excessive agglomeration between radical scavengers can be effectively prevented, and the stability of the radical scavenger can be further improved.

[0024] According to the tenth aspect of the present invention, in the ninth aspect, the carbon-based material may further include at least one hetero element among nitrogen (N), phosphorus (P), and sulfur (S).

[0025] According to an eleventh aspect of the present invention, in any one of the seventh to tenth aspects, the protective layer may include titania, and the precursor may include at least one of titanium (tetra)isopropoxide, titanium ethoxide, titanium methoxide, and titanium tetrachloride as a precursor for forming the titania.

[0026] According to a twelfth aspect of the present invention, in any one of the seventh to eleventh aspects, the protective layer may include silica, and the precursor may include at least one of tetraethyl orthosilicate and tetramethyl orthosilicate as a precursor for forming the silica.

[0027] According to a thirteenth aspect of the present invention, in any one of the seventh to twelfth aspects, the protective layer may include a carbon-based material, and the precursor may include at least one of a phenol-formaldehyde resin, a urea-formaldehyde resin, and a pyrrole as a precursor for forming the carbon-based material. Alternatively, the precursor may be any one selected from the group consisting of phenol, formaldehyde, urea, pyrrole, and combinations thereof.

[0028] According to a fourteenth aspect of the present invention, in any one of the seventh to thirteenth aspects, the step of forming the protective layer may include the step of forming a preliminary protective layer obtained from the precursor; and the step of performing a heat treatment process on the preliminary protective layer to form the protective layer from the preliminary protective layer. In some examples, each step of forming the protective layer may be repeated once or multiple times, thereby forming a single-layer or multi-layer structure. In some embodiments, the protective layer may include a titania layer, and the crystal structure of the titania layer may be controlled depending on the temperature of the heat treatment process.

[0029] In some embodiments, the protective layer may include a carbon-based material layer, the pre-protective layer may include a polymer material layer, and the carbon-based material layer may be formed by carbonizing the polymer material layer through the heat treatment process.

[0030] In some embodiments, a method for manufacturing a membrane-electrode assembly (MEA) may be provided, comprising: manufacturing a radical scavenger using a method according to any one of the seventh to thirteenth aspects; and manufacturing a membrane-electrode assembly (MEA) comprising the radical scavenger.

[0031] According to a fifteenth aspect of the present invention, a membrane-electrode assembly (MEA) is provided, comprising: a first electrode; a second electrode disposed spaced apart from the first electrode; a polymer electrolyte membrane disposed between the first electrode and the second electrode; and a radical scavenger provided on at least one of the first electrode, the second electrode, and the polymer electrolyte membrane, wherein the radical scavenger has a characteristic according to any one of the first to fourteenth aspects.

[0032] According to a sixteenth aspect of the present invention, in the fifteenth aspect, the membrane-electrode assembly may further include an interfacial bonding layer (IBL) disposed between the first electrode and the polymer electrolyte membrane and between the second electrode and the polymer electrolyte membrane, and the interfacial bonding layer may include a radical scavenger having any one of the characteristics of the first to fourteenth aspects.

[0033] According to a seventeenth aspect of the present invention, a fuel cell is provided comprising a membrane-electrode assembly according to the fifteenth or sixteenth aspect.

[0034] According to one aspect of the present invention, a protective layer having excellent stability is formed on the surface of a radical-scavenging particle with a relatively thin thickness using a vapor adsorption method, thereby realizing a radical scavenger having excellent durability while preventing or minimizing aggregation between the capturing particles. In addition, depending on the type / material and number of layers of the protective layer, various functionalities (additional characteristics) can be imparted to the protective layer, and as a result, a radical scavenger having excellent functionality can be realized.

[0035] By applying a radical scavenger according to one aspect of the present invention, a membrane-electrode assembly (MEA) with improved durability (chemical durability), stability, and performance can be manufactured, and a fuel cell including the same can be manufactured.

[0036] FIG. 1 is a drawing for explaining a method for manufacturing a radical scavenger according to one embodiment of the present invention and a radical scavenger manufactured by the method.

[0037] FIG. 2 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger manufactured by the method.

[0038] FIG. 3 is a drawing showing a radical scavenger manufactured according to one embodiment of the present invention.

[0039] FIG. 4 is a transmission electron microscope image showing a radical scavenger manufactured according to one embodiment of the present invention.

[0040] FIG. 5 is a transmission electron microscope image showing a radical scavenger manufactured according to a reference example of the present invention.

[0041] FIG. 6 is a drawing showing a radical scavenger manufactured according to another embodiment of the present invention.

[0042] FIG. 7 is a transmission electron microscope image showing a radical scavenger manufactured according to another embodiment of the present invention.

[0043] FIG. 8 is a drawing showing a radical scavenger manufactured according to another embodiment of the present invention.

[0044] FIG. 9 is a transmission electron microscope photograph showing a radical scavenger manufactured according to another embodiment of the present invention.

[0045] FIG. 10 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger manufactured by the method.

[0046] FIG. 11 is a transmission electron microscope photograph showing a radical scavenger manufactured according to another embodiment of the present invention.

[0047] FIG. 12 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger manufactured by the method.

[0048] FIG. 13 is a cross-sectional view showing a membrane-electrode assembly (MEA) to which a radical scavenger is applied, according to one embodiment of the present invention.

[0049] FIG. 14 is a cross-sectional view showing a membrane-electrode assembly (MEA) to which a radical scavenger is applied, according to another embodiment of the present invention.

[0050] FIG. 15 is a cross-sectional scanning electron microscope photograph of a membrane-electrode assembly (MEA) having an interfacial adhesive layer to which a radical scavenger is applied, according to one embodiment of the present invention.

[0051] FIG. 16 is a cross-sectional scanning electron microscope photograph of a polymer electrolyte membrane (PEM) to which a radical scavenger is applied, according to one embodiment of the present invention.

[0052] FIG. 17 is a drawing exemplarily showing a fuel cell including a membrane-electrode assembly (MEA) to which a radical scavenger manufactured according to one embodiment of the present invention is applied.

[0053] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0054] The embodiments of the present invention described below are provided to more clearly explain the present invention to a person having ordinary skill in the art, and the scope of the present invention is not limited by the following embodiments, and the following embodiments can be modified in various other forms.

[0055] The terminology used herein is used to describe particular embodiments and is not intended to limit the present invention. The singular forms used herein may include the plural forms unless the context clearly dictates otherwise. In addition, the terms "comprise" and / or "comprising" used herein specify the presence of a stated feature, step, number, operation, element, element, and / or group thereof, but do not exclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements, and / or groups thereof. In addition, the term "connected" used herein not only means that certain elements are directly connected, but also includes a concept that indirectly connects elements by interposing another element between them.

[0056] When a member is said to be "on" another member in this specification, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members. The term "and / or" as used herein includes any and all combinations of one or more of the listed items. In addition, terms of degree such as "about," "substantially," etc. as used in this specification are used to mean a range of or approximation to a numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly exploiting the disclosure, which mentions exact or absolute numbers provided to aid the understanding of this specification.

[0057] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​stated before and after the term as the lower and upper limits, respectively. For example, if "a" and "b" are stated in the specification, it can be understood that "a" and "b" are stated.

[0058] In the present specification, when multiple numerical values ​​are disclosed as the upper and lower limits of any numerical range, the numerical range disclosed in the present specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit value and the upper limit value, respectively. For example, when a or more, or b or more; and c or less or d or less are described, it can be understood that a or more and c or less, a or more and d or less, b or more and c or less, or b or more and d or less are described.

[0059] In this specification, the term "layer" or film may include cases where it is formed not only over the entire area when observing the area where the layer or film exists, but also cases where it is formed over only a portion of the area. For example, the surface of the layer or film may be defined to include a flat shape, a non-flat shape, and a combination thereof; or a continuous shape, a discontinuous shape, and a combination thereof. For example, when another element is formed as a layer or film directly on top of one element, the coverage of the other element on the surface of the one element may be defined as 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more. For example, even when a plurality of particles form a clustered structure, it may be defined as a "layer."

[0060] In this specification, "or" may be defined to mean "and / or." For example, a or b may be defined to include either a or b alone or both a and b.

[0061] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The sizes and thicknesses of areas or parts depicted in the attached drawings may be somewhat exaggerated for clarity and convenience of explanation. Like reference numbers designate like components throughout the detailed description.

[0062] FIG. 1 is a drawing for explaining a method for manufacturing a radical scavenger according to one embodiment of the present invention and a radical scavenger (50) manufactured by the method.

[0063] Referring to FIG. 1, a method for manufacturing a radical scavenger according to an embodiment of the present invention may include a step of preparing radical-scavenging particles (10) and a step of forming a protective layer (20) on the surface of the radical-scavenging particles (10). In the step of forming the protective layer (20), a vapor adsorption method may be used. The protective layer (20) may be referred to as a type of coating layer or shell layer. The radical scavenger (50) manufactured by the method of the present embodiment may be referred to as a type of 'radical scavenger complex' or 'radical scavenger complex particle'.

[0064] The radical-capturing particles (10) are not particularly limited and can be used as long as they are particles or additives (particle-type additives) having radical scavenging ability, and any material can be utilized to form a complex (i.e., 50) in the embodiment of the present invention. For example, the radical-capturing particles (10) can be one or more selected from the group consisting of transition metals, noble metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof.

[0065] The above transition metal may be, but is not limited to, cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), or neodymium (Nd). The above precious metal may be, but is not limited to, silver (Au), platinum (Pt), ruthenium (Ru), palladium (Pd), or rhodium (Rh). The salt of the above transition metal or noble metal may be a carbonate, acetate, chloride, fluoride, sulfate, phosphate, nitrate, tungstate, hydroxide, ammonium acetate, ammonium sulfate, or acetylacetonate salt, but this is exemplary and the present invention is not limited thereto, and various other radical scavenging materials may be used.

[0066] For example, the radical trapping particle (10) may include at least one selected from the group consisting of cerium oxide, MnO2, and Pt nanoparticles. Here, the cerium oxide may be ceria, i.e., CeO2. The radical trapping particle (10) may be a particle containing ceria or may be a ceria particle. When the radical trapping particle (10) contains ceria or is a ceria particle, it may have relatively excellent radical trapping performance.

[0067] Meanwhile, the diameter of the radical trapping particle (10) may be about 3 nm to 100 nm, and more preferably, about 4 nm to 80 nm. However, the diameter range of the radical trapping particle (10) described above is exemplary and may vary depending on the case. The radical trapping particle (10) may be a type of nanoparticle (nanoscale particle).

[0068] In the step of forming the above protective layer (20), a vapor adsorption method of vaporizing a given precursor and adsorbing the precursor or a component decomposed from the precursor onto the surface of the radical trapping particle (10) can be used to form a protective layer (20) obtained from the precursor on the surface of the radical trapping particle (10).

[0069] By heating the precursor to a predetermined temperature and vaporizing it, the precursor (vaporized precursor) or the component decomposed from the precursor (vaporized precursor) can be adsorbed on the surface of the radical trapping particle (10). The precursor can have a vaporization temperature in the range of, for example, about 60 to 250°C. Any substance capable of 'vaporization' or 'vaporization and decomposition / polymerization' at a temperature in the range of about 60 to 250°C can be used as the precursor.

[0070] The protective layer (20) may include at least one of titania, silica, and a carbon-based material. The protective layer (20) may include at least one of a titania layer, a silica layer, and a carbon-based material layer. Here, the carbon-based material may further include at least one hetero element selected from the group consisting of nitrogen (N), sulfur (S), and the like.

[0071] When the protective layer (20) includes titania, for example, when the protective layer (20) is a titania layer, the precursor may include at least one of titanium tetraisopropoxide, titanium ethoxide, and tetraethyl orthotitanate as a precursor for forming the titania (titania layer). However, the precursor material for forming titania is not limited to the above-described one and may vary depending on the case.

[0072] When the protective layer (20) includes silica, for example, when the protective layer (20) is a silica layer, the precursor may include at least one of tetraethyl orthosilicate (TEOS) and tetramethyl orthosilicate (TMOS) as a precursor for forming the silica (silica layer). However, the precursor material for forming silica is not limited to the above-described one and may vary depending on the case.

[0073] When the protective layer (20) includes a carbon-based material, for example, when the protective layer (20) is a carbon-based material layer, the precursor may include at least one of phenol-formaldehyde resin, urea-formaldehyde resin, and pyrrole as a precursor for forming the carbon-based material (carbon-based material layer). However, the precursor material for forming the carbon-based material is not limited to the above-described one and may vary depending on the case. Here, when the precursor includes a hetero element such as nitrogen (N), sulfur (S), etc., a carbon-based material layer doped with the hetero element may be formed. The carbon-based material layer may be a carbon layer. Therefore, the protective layer (20) may include a carbon layer or a carbon layer doped with a hetero element.

[0074] In the above-described vapor adsorption process, the vaporized precursor or the component decomposed from the vaporized precursor may be adsorbed on the surface of the radical trapping particle (10) to form an adsorption layer (coating layer). In the above-described vapor adsorption process, a predetermined heat treatment process may be performed simultaneously on the vaporized precursor and the radical trapping particle (10), or a predetermined heat treatment process (subsequent heat treatment process) may be performed separately on the adsorption layer (coating layer) after the vapor adsorption process. Through the above-described heat treatment process and / or the subsequent heat treatment process, the protective layer (20) can be formed more easily, and the material composition, physical properties, crystal structure, porosity, etc. of the protective layer (20) can be controlled.

[0075] In some embodiments, pores may be formed in the protective layer (20). The pores may be formed through the heat treatment process and / or the subsequent heat treatment process. For example, the protective layer (20) may have a porous structure. The porosity of the protective layer (20) may be, for example, about 1% to about 15%. The pores may be amorphous pores. The amorphous pores may be micropores having a diameter of less than about 2 nm for the most part, and may also include some mesopores having a diameter of more than about 2 nm and less than about 50 nm. When the protective layer (20) has pores, the radical trapping performance of the radical trapping particles (10) may be partially improved. For example, the proportion of the micropores relative to the total 100 vol% of amorphous pores may be 80 vol% or more, 85 vol% or more, or 90 vol% or more.

[0076] According to another aspect of the present invention, a radical scavenger is provided, comprising: a radical-scavenging particle; and a protective layer formed on the surface of the radical-scavenging particle, wherein the ratio of the standard deviation of the thickness to the average thickness of the protective layer is 5% or less. In some examples, the maximum thickness deviation of the protective layer can be analyzed using a transmission electron microscope.

[0077] In some embodiments of the present invention, the ratio of the thickness standard deviation to the average thickness of the protective layer may be 4.5% or less, 4.0% or less, 3.5% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.98% or less, 1.9% or less, 1.87% or less, 1.8% or less, 1.74% or less, 1.7% or less, 1.6% or less, 1.59% or less, 1.57% or less, 1.40% or less, 1.30% or less, 1.28% or less, or 0.5% or more or less of any one of the plurality of upper limits. If the ratio of the thickness standard deviation to the average thickness of the protective layer is outside the numerical range, a problem may occur in which the protective layer is not uniformly formed or the protective layer is formed in bulk. This may result in a degradation of the radical scavenger's function, resulting in insufficient chemical durability when applied to the electrolyte membrane or electrode. The ratio of the standard deviation of the thickness to the average thickness of the protective layer can be achieved by independently adjusting the precursor type, precursor content, vapor phase adsorption method, or vapor phase adsorption method process conditions.

[0078] Since the protective layer (20) is formed using the above-described vapor absorption method, it can be easily formed with a relatively thin thickness. The thickness of the protective layer (20) may be about 0.05 nm to 20 nm. For example, the thickness of the protective layer (20) may be about 0.05 to 10 nm or about 0.05 to 5 nm. In an embodiment of the present invention, the formation of a bulk protective layer can be suppressed (minimized) or prevented.

[0079] According to an embodiment of the present invention, in relation to forming a protective layer (20) using the above-described vapor adsorption method, a protective layer (20) having excellent film quality and a relatively thin thickness can be easily formed. In addition, aggregation between radical scavengers (50) (i.e., composite particles) can be suppressed or minimized. By forming a protective layer (20) having excellent film quality and stability with a relatively thin thickness on the surface of a radical-capturing particle (10) using the above-described vapor adsorption method, a radical scavenger (50) having excellent durability and in which aggregation between particles can be prevented or minimized can be implemented. In addition, depending on the type / material of the protective layer (20) and the number of layers, etc., various functionalities (additional characteristics) can be imparted to the protective layer (20), and as a result, a radical scavenger (50) having excellent functionality can be implemented.

[0080] FIG. 2 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger (50) manufactured by the method.

[0081] Referring to FIG. 2, a method for manufacturing a radical scavenger according to an embodiment of the present invention may include a step of preparing radical trapping particles (10), a step of forming a preliminary protective layer (20') on the surface of the radical trapping particles (10) using a vapor adsorption method using a precursor, and a step of performing a heat treatment process on the preliminary protective layer (20') to form a protective layer (20) from the preliminary protective layer (20'). The vapor adsorption method used to form the preliminary protective layer (20') may be the same as or similar to that described with reference to FIG. 1. Therefore, the vapor adsorption method described in FIG. 1 may be applied to FIG. 2 within a range that is not contradictory. The heat treatment process may be performed at a temperature of, for example, about 800 to 2400°C.

[0082] When the protective layer (20) is a titania layer or includes a titania layer, the crystal structure of the titania layer can be controlled depending on the temperature of the heat treatment process. Therefore, in this regard, the characteristics of the protective layer (20) can be easily controlled.

[0083] Meanwhile, when the protective layer (20) is a carbon-based material layer or includes a carbon-based material layer, the preliminary protective layer (20') may be a polymer material layer or include a polymer material layer. In this case, the carbon-based material layer can be formed from the polymer material layer by carbonizing the polymer material layer through the heat treatment process. In addition, if necessary, a graphitization process can be further performed on the carbon-based material layer.

[0084] According to an embodiment of the present invention, a protective layer (20) with controlled properties can be formed more easily through a vapor adsorption process and a subsequent heat treatment process.

[0085] FIG. 3 is a drawing showing a radical scavenger manufactured according to one embodiment of the present invention.

[0086] Referring to FIG. 3, the radical scavenger (50a) may include radical-capturing particles (10) and a protective layer (20a) formed on the surface thereof. The protective layer (20a) may be formed using a vapor-phase adsorption process. A precursor of a carbon-based material may be applied to the vapor-phase adsorption process. Therefore, in the present embodiment, the protective layer (20a) may be a carbon-based material layer (e.g., a carbon layer).

[0087] FIG. 4 is an electron microscope image showing a radical scavenger manufactured according to one embodiment of the present invention.

[0088] Referring to Fig. 4, the manufactured radical scavenger (composite particle) has the same configuration as described in Fig. 3. The protective layer of the radical scavenger (composite particle) is a carbonaceous material layer (carbon layer) formed using a gas phase adsorption process using phenol-formaldehyde (a type of phenolic resin) as a precursor of a carbonaceous material.

[0089] FIG. 5 is an electron microscope image showing a radical scavenger manufactured according to a reference example of the present invention.

[0090] Referring to Fig. 5, the manufactured radical scavenger (composite particle) has the same configuration as described in Fig. 3. The protective layer of the radical scavenger (composite particle) is a carbonaceous material layer (carbon layer) formed using a hydrothermal reaction process in a solvent using phenol-formaldehyde (a type of phenolic resin) as a precursor of a carbonaceous material.

[0091] FIG. 6 is a drawing showing a radical scavenger manufactured according to another embodiment of the present invention.

[0092] Referring to FIG. 6, the radical scavenger (50b) may include radical-capturing particles (10) and a protective layer (20b) formed on the surface thereof. The protective layer (20b) may be formed using a vapor-phase adsorption process. A silica precursor may be applied to the vapor-phase adsorption process. Therefore, in the present embodiment, the protective layer (20b) may be a silica layer.

[0093] FIG. 7 is an electron microscope image showing a radical scavenger manufactured according to another embodiment of the present invention.

[0094] Referring to Fig. 7, the manufactured radical scavenger (composite particle) has the same configuration as described in Fig. 5. The protective layer of the radical scavenger (composite particle) is a silica layer formed using a gas phase adsorption process using TEOS (Tetraethyl orthosilicate) as a silica precursor.

[0095] FIG. 8 is a drawing showing a radical scavenger manufactured according to another embodiment of the present invention.

[0096] Referring to FIG. 8, the radical scavenger (50c) may include radical-capturing particles (10) and a protective layer (20c) formed on the surface thereof. The protective layer (20c) may be formed using a vapor phase adsorption process. A titania precursor may be applied to the vapor phase adsorption process. Therefore, in the present embodiment, the protective layer (20c) may be a titania layer.

[0097] FIG. 9 is a transmission electron microscope photograph showing a radical scavenger manufactured according to another embodiment of the present invention.

[0098] Referring to Fig. 9, the manufactured radical scavenger (composite particle) has the same configuration as described in Fig. 7. The protective layer of the radical scavenger (composite particle) is a titania layer formed using a vapor phase adsorption process using titanium tetraisopropoxide as a titania precursor. The titania protective layer is formed in the form of particles with a size of 0.05 to 20 nm due to the characteristics of titania.

[0099] FIG. 10 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger (50A) manufactured by the method.

[0100] Referring to FIG. 10, a radical scavenger (50A) according to the present embodiment may include radical-capturing particles (10) and a protective layer (20A) formed on the surface thereof. The protective layer (20A) may be formed using a vapor-phase adsorption process.

[0101] The protective layer (20A) may have a multilayer structure including at least two different material layers (21, 22). In the present embodiment, the protective layer (20A) has a two-layer structure including a first material layer (21) and a second material layer (22). The first material layer (21) and the second material layer (22) may be sequentially formed (laminated) on the surface of the radical trapping particle (10).

[0102] According to one embodiment, the protective layer (20A) may include a titania layer. In addition, the protective layer (20A) may include two material layers selected from a titania layer, a silica layer, and a carbon-based material layer. As a specific example, the first material layer (21) may be a titania layer, and the second material layer (22) may be either a silica layer or a carbon-based material layer.

[0103] Each of the first and second material layers (21, 22) constituting the protective layer (20A) can be formed using the method described with reference to FIGS. 1 and 2. Each of the first and second material layers (21, 22) can have a thickness of about 0.05 to 20 nm, or a thickness of about 0.05 to 10 nm, or a thickness of about 0.05 to 5 nm.

[0104] As shown in Fig. 10, when the protective layer (20A) has a multi-layer structure, the durability and stability of the radical scavenger (50A) can be further improved. In addition, the characteristics of the radical scavenger (50A) can be improved by the functionality (different functionality) of each of the first and second material layers (21, 22).

[0105] FIG. 11 is a transmission electron microscope image showing a radical scavenger manufactured according to another embodiment of the present invention.

[0106] Referring to Fig. 11, the manufactured radical scavenger (composite particle) has the same configuration as described in Fig. 9. The first material layer of the radical scavenger (composite particle) protective layer is a titania layer formed using a vapor phase adsorption process using titanium tetraisopropoxide as a titania precursor. The titania protective layer forms the protective layer in the form of particles having a size of 0.05 to 20 nm due to the characteristics of titania. The second material layer of the radical scavenger (composite particle) protective layer is a silica layer formed using a vapor phase adsorption process using TEOS as a silica precursor.

[0107] FIG. 12 is a drawing for explaining a method for manufacturing a radical scavenger according to another embodiment of the present invention and a radical scavenger manufactured by the method.

[0108] Referring to FIG. 12, a radical scavenger (50B) according to the present embodiment may include radical-capturing particles (10) and a protective layer (20B) formed on the surface thereof. The protective layer (20B) may be formed using a vapor-phase adsorption process.

[0109] The protective layer (20B) may have a multilayer structure including at least two different material layers (21, 22, 23). In the present embodiment, the protective layer (20B) has a three-layer structure including a first material layer (21), a second material layer (22), and a third material layer (23). The first material layer (21), the second material layer (22), and the third material layer (23) may be sequentially formed (stacked) on the surface of the radical trapping particle (10).

[0110] According to one embodiment, the protective layer (20B) may include a titania layer. In addition, the protective layer (20B) may include at least two material layers selected from a titania layer, a silica layer, and a carbon-based material layer. As a specific example, the first material layer (21) may be a titania layer, the second material layer (22) may be a silica layer, and the third material layer (23) may be a carbon-based material layer.

[0111] Each of the first to third material layers (21, 22, 23) constituting the protective layer (20B) can be formed using the method described with reference to FIGS. 1 and 2. Each of the first to third material layers (21, 22, 23) can have a thickness of about 0.05 to 20 nm, or about 0.05 to 10 nm, or about 0.05 to 5 nm.

[0112] As shown in Fig. 12, when the protective layer (20B) has a multi-layer structure, the durability and stability of the radical scavenger (50B) can be further improved. In addition, the characteristics of the radical scavenger (50B) can be improved by the functionality (different functionalities) of each of the first to third material layers (21, 22, 23). In particular, when the protective layer (20B) has a three-layer structure as shown in Fig. 11, the characteristics of the radical scavenger (50B) can be significantly improved in various aspects. Additionally, the protective layer of the radical scavenger according to an embodiment of the present invention may have a multi-layer structure of three or more layers.

[0113] FIG. 13 is a cross-sectional view showing a membrane-electrode assembly (MEA) to which a radical scavenger is applied, according to one embodiment of the present invention.

[0114] Referring to FIG. 13, a membrane-electrode assembly (MEA) according to some embodiments of the present invention may include a first electrode (110), a second electrode (120) disposed spaced apart from the first electrode (110), and a polymer electrolyte membrane (130) disposed between the first electrode (110) and the second electrode (120). In addition, the membrane-electrode assembly (MEA) may include a radical scavenger (a plurality of particles) (not shown) provided within or between at least one of the first electrode (110), the second electrode (120), and the polymer electrolyte membrane (130). Here, the radical scavenger may have a configuration as described with reference to FIGS. 1 to 11, and may be manufactured by a manufacturing method as described above.

[0115] The first electrode (110) may be an oxidizing electrode, and the second electrode (120) may be a reducing electrode. The first electrode (110) may be or include a first electrode catalyst layer, and the second electrode (120) may be or include a second electrode catalyst layer. The radical scavenger may be applied to at least one of the first and second electrode catalyst layers. As materials for each of the first electrode (110), the second electrode (120), and the polymer electrolyte membrane (130), corresponding constituent materials of a membrane-electrode assembly (MEA) for an existing fuel cell may be applied.

[0116] FIG. 14 is a cross-sectional view showing a membrane-electrode assembly (MEA) to which a radical scavenger is applied, according to another embodiment of the present invention.

[0117] FIG. 15 is a cross-sectional scanning electron microscope photograph of a membrane-electrode assembly having an interfacial adhesive layer to which a radical scavenger is applied, according to one embodiment of the present invention.

[0118] Referring to FIGS. 14 and 15, a membrane-electrode assembly (MEA) according to some embodiments of the present invention may include a first electrode (110), a second electrode (120) disposed spaced apart from the first electrode (110), and a polymer electrolyte membrane (130) disposed between the first electrode (110) and the second electrode (120). In addition, the membrane-electrode assembly (MEA) may further include an interfacial bonding layer (IBL) (115, 125) disposed between at least one of the first electrode (110) and the polymer electrolyte membrane (130) and between the second electrode (120) and the polymer electrolyte membrane (130). Here, a case is illustrated where a first interfacial adhesive layer (115) is disposed between a first electrode (110) and a polymer electrolyte membrane (130), and a second interfacial adhesive layer (125) is disposed between a second electrode (120) and a polymer electrolyte membrane (130).

[0119] The membrane-electrode assembly (MEA) according to some embodiments of the present invention may include a radical scavenger (a plurality of particles) (not shown) provided within or between at least one of the first electrode (110), the first interfacial adhesive layer (115), the second electrode (120), the second interfacial adhesive layer (125), and the polymer electrolyte membrane (130). Accordingly, at least a portion of the radical scavenger may be provided within at least one of the first and second interfacial adhesive layers (115, 125). Here, the radical scavenger may have a configuration as described with reference to FIGS. 1 to 12, and may be manufactured by a manufacturing method as described above.

[0120] Meanwhile, the interfacial adhesive layer (115, 125) may include an ionomer, and may serve to improve the durability of the membrane-electrode assembly (MEA) by enabling the membrane-electrode assembly (MEA) to have low hydrogen permeability without lowering ionic conductivity and improving the interfacial bonding between the electrode (110, 120) and the polymer electrolyte membrane (130).

[0121] A method for manufacturing a membrane-electrode assembly (MEA) according to an embodiment of the present invention may include a step of manufacturing a radical scavenger using a method as described with reference to FIGS. 1 to 12 and a step of manufacturing a membrane-electrode assembly (MEA) using the radical scavenger. The membrane-electrode assembly (MEA) manufactured in this manner may have a configuration as described with reference to FIGS. 13 and 14.

[0122] FIG. 16 is a cross-sectional view showing a polymer electrolyte membrane (PEM) to which a radical scavenger is applied, according to one embodiment of the present invention.

[0123] FIG. 17 is a drawing exemplarily showing a fuel cell (200) including a membrane-electrode assembly (MEA) to which a radical scavenger manufactured according to one embodiment of the present invention is applied.

[0124] Referring to FIG. 17, a fuel cell (200) according to an embodiment of the present invention may include a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reforming unit (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reforming unit (220) and the stack (230).

[0125] The stack (230) may be equipped with a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction of a reforming gas containing hydrogen gas supplied from a reforming unit (220) and an oxidizing agent supplied from an oxidizing agent supply unit (240).

[0126] The above unit cell refers to a unit cell that generates electricity, and may include a membrane-electrode assembly that oxidizes / reduces oxygen in a reforming gas containing hydrogen gas and an oxidizing agent, and a separator (also referred to as a 'bipolar plate') for supplying the reforming gas containing hydrogen gas and the oxidizing agent to the membrane-electrode assembly. The separator may be positioned on both sides of the membrane-electrode assembly with the membrane-electrode assembly at the center. In this case, the separator plates each positioned at the outermost side of the stack (230) may be specifically referred to as end plates.

[0127] Among the above separators, one end plate may be provided with a first supply pipe (231) in the shape of a pipe for injecting reformed gas containing hydrogen gas supplied from a reforming unit (220), and a second supply pipe (232) in the shape of a pipe for injecting oxygen gas, and the other end plate may be provided with a first discharge pipe (233) for discharging reformed gas containing hydrogen gas that is ultimately unreacted and remains in a plurality of unit cells to the outside, and a second discharge pipe (234) for discharging oxidant that is ultimately unreacted and remains in the unit cells to the outside.

[0128] In a fuel cell according to an embodiment of the present invention, the membrane-electrode assembly included in the stack (230) may have a configuration as described with reference to FIGS. 13 and 14. Although the configuration of the fuel cell is specifically illustrated and described in FIG. 17, this configuration is merely exemplary and may vary depending on the case.

[0129] According to the embodiments of the present invention described above, a protective layer having excellent stability is formed with a relatively thin thickness on the surface of radical-capturing particles using a vapor-phase adsorption method, thereby realizing a radical scavenger having excellent durability while preventing or minimizing aggregation between the capturing particles. In addition, depending on the type / material and number of layers of the protective layer, various functionalities (additional characteristics) can be imparted to the protective layer, and as a result, a radical scavenger having excellent functionality can be realized. By applying the radical scavenger according to the embodiments of the present invention, a membrane-electrode assembly (MEA) with improved durability (chemical durability), stability, and performance can be manufactured, and a fuel cell including the same can be manufactured.

[0130] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0131] [Manufacturing Example 1: Manufacturing of a Radical Scavenger]

[0132] <Comparative Example: Commercial Radical Scavenger Without a Protective Layer>

[0133] Average diameter (D) 50 ) prepared CeO2 with a thickness of 50 nm.

[0134] <Example 1-1: Radical scavenger including a carbon protective layer>

[0135] 80 parts by weight of phenol (Aldrich) and 70 parts by weight of para-formaldehyde were placed at the bottom of a vacuum infiltration chamber with a mesh in the middle, and the average diameter (D 50 ) was placed at the top of a vacuum infiltration chamber, 100 parts by weight of CeO2 having a thickness of 50 nm, and heated and vaporized in the chamber at 150°C for 30 minutes to form a preliminary carbon protective layer having a thickness of 4 nm on the surface of CeO2 by vapor adsorption.

[0136] The CeO2 having the above-mentioned preliminary carbon protective layer formed thereon was heat-treated at 1,000°C for 60 minutes using a heat treatment device in a tube furnace to form a carbon protective layer (thickness: 3.8 nm, porosity 5 vol%) on the surface of the CeO2. At this time, the porosity of the carbon protective layer means the percentage of the volume of pores with respect to the total volume of the carbon protective layer, and the pore volume before / after the heat treatment was analyzed using a BET nitrogen adsorption / desorption measurement method.

[0137] <Example 1-2: Radical scavenger including a carbon protective layer>

[0138] A radical scavenger was manufactured in the same manner as in Example 1-1, but MnO2 having a size of 50 nm was used instead of CeO2, and a preliminary carbon protective layer having a thickness of 4 nm was manufactured on the surface of MnO2, and then a carbon protective layer (thickness: 3.8 nm, porosity 5 vol%) was formed on the surface of MnO2 through heat treatment.

[0139] <Example 1-3: Radical scavenger Pt nanoparticles containing a carbon protective layer>

[0140] A radical scavenger was manufactured in the same manner as in Example 1-1, but instead of the CeO2, Pt nanoparticles having a size of 20 nm were used, and a preliminary carbon protective layer having a thickness of 2 nm was manufactured on the surface of the Pt nanoparticles, and then a carbon protective layer (thickness: 1.9 nm, porosity 3 vol%) was formed on the surface of the Pt nanoparticles through heat treatment.

[0141] <Example 2: Radical scavenger including a silica protective layer>

[0142] A radical scavenger was manufactured in the same manner as in Example 1-1, except that 150 parts by weight of tetraethyl orthosilicate (silica precursor) was used instead of the phenol-formaldehyde resin precursor, and in the vapor phase adsorption method, the heating temperature and heating time were changed from 100°C to 30 minutes, and the heat treatment temperature and heat treatment time were changed from 550°C to 100 minutes. As a result, a silica protective layer having a thickness of 4 nm and a porosity of 2 vol% was formed.

[0143] <Example 3: Radical scavenger including a titania protective layer>

[0144] A radical scavenger was manufactured in the same manner as in Example 1-1, except that 130 parts by weight of titanium tetraisopropoxide was used instead of the phenol-formaldehyde resin precursor, and in the vapor phase adsorption method, the heating temperature and heating time were changed from 130°C to 30 minutes, and the heat treatment temperature and heat treatment time were changed from 600°C to 60 minutes. As a result, a titania protective layer having a thickness of 8 nm and a porosity of 10 vol% was formed.

[0145] Meanwhile, analysis using a transmission electron microscope (TEM) revealed that the titania protective layer was a cluster of particles with an average diameter of 3 nm.

[0146] <Example 4: Radical scavenger comprising a titania-silica protective layer>

[0147] A radical scavenger prepared in the same manner as in Example 3 except that 60 parts by weight of titanium tetraisopropoxide was used was placed in the chamber, and then 100 parts by weight of tetraethyl orthosilicate (silica precursor) was added to 100 parts by weight of CeO2 on which a titania layer was formed, heated and vaporized in the chamber at 100°C for 20 minutes, and then heat-treated at 600°C for 60 minutes to form a titania-silica protective layer. As a result, it was analyzed using a transmission electron microscope (TEM) method that the titania layer had a thickness of 6 nm (a cluster of particles with an average diameter of 2 nm), the silica layer had a thickness of 3 nm, and the porosity of the titania-silica layer was 4 vol% based on the total volume of the protective layer.

[0148] <Reference example: Manufacturing of a radical scavenger with a carbon protective layer manufactured using a conventional manufacturing method>

[0149] A radical scavenger was manufactured in the same manner as in Example 1-1, except that the protective layer was formed using a method other than a vapor-phase adsorption method as in Example 1-1.

[0150] Specifically, a dispersion was prepared by adding the same amount of radical scavenger (CeO2) as in Example 1-1 and the same amount of polymer precursor (phenol and para-formaldehyde) as in Example 1-1 to a solvent (water). A radical scavenger of the reference example was prepared in the same manner as in Example 1-1, except that the dispersion was heated at 150°C for 30 minutes to induce polymer polymerization.

[0151] [Experimental Example 1: Ratio of the standard deviation of the thickness to the average thickness of the radical scavenger protective layer]

[0152] For each of the radical scavengers manufactured by the methods according to the above-mentioned Reference Examples and Examples 1-1 to 1-3, 2, the ratio of the thickness standard deviation to the average thickness of the protective layer was measured using a transmission electron microscope. Specifically, after sampling five random points from the sample, the thickness of the protective layer for more than five areas or 100 particles of the sampled specimen was measured to determine the average thickness value of the protective layer. Thereafter, the standard deviation for the entire sample was calculated and divided by the average thickness of the protective layer, and the ratio of the thickness standard deviation to the average thickness was shown in Table 1 below.

[0153] In addition, for Examples 3 and 4 including a titania protective layer including a clustered structure of multiple particles, the thickness of the protective layer formed by the agglomeration of particles was measured in the same manner as above, and the ratio of the standard deviation of the thickness to the average thickness was calculated.

[0154] Sample (radical scavenger) Reference Example Example 1-1 Example 1-2 Example 1-3 Example 2 Example 3 Example 4 Protective layer Carbon protective layer Carbon protective layer Carbon protective layer Carbon protective layer Silica protective layer Titania protective layer Titania-silica protective layer Ratio of the thickness standard deviation to the average thickness of the protective layer (%) 6.90% 1.57% 1.59% 1.28% 1.74% 1.98% 1.87%

[0155] Referring to Table 1 above, the radical scavengers of Examples 1-1 to 1-3 showed a result in which the ratio of the standard deviation of the thickness to the average thickness of the protective layer was lowered by forming the protective layer uniformly compared to the reference example in which the protective layer was formed in bulk.

[0156] [Manufacturing Example 2: Manufacturing of a Membrane-Electrode Assembly]

[0157] <Membrane electrode assemblies of comparative examples and examples 1-1 to 1-3 and 2 to 4>

[0158] Preparation steps of electrode slurry:

[0159] 100 parts by weight of a commercial Pt / C catalyst from Tanaka and 100 parts by weight of a binder (a fluorine-based resin having a solid content) were placed in a reaction vessel and wetted with a solvent (water) to prepare a catalyst dispersion. To the catalyst dispersion, 5 parts by weight of each radical scavenger of Preparation Example 1 was added based on 100 parts by weight of the Pt / C catalyst to prepare a mixture. The mixture was dispersed with a homogeneous mixer at 6000 rpm for 30 minutes to prepare an electrode slurry having a total solid content of 15 wt%.

[0160] Preparation steps of polymer electrolyte membrane:

[0161] A polymer electrolyte membrane was prepared by applying a first ionomer dispersion (20 wt%, Nafion D-2020) on a glass substrate, drying at 120°C for 6 hours, and heat-treating at 160°C for 1 hour.

[0162] Manufacturing steps of membrane-electrode assembly:

[0163] After coating the above electrode slurry on the release film, 60 o A catalyst layer was prepared by drying at C for 4 hours. The prepared catalyst layer was transferred onto both sides of the polymer electrolyte membrane at 150°C and 1 MPa for 2 minutes to prepare a membrane-electrode assembly.

[0164] <Example 5: Manufacturing of a membrane-electrode assembly including an additional interfacial adhesive layer, unlike Example 4>

[0165] Preparation of a composition for forming an interface adhesive layer:

[0166] In the Nafion D-520 dispersion, the average diameter (D) is calculated based on 100 parts by weight of the total solid content of the dispersion. 50 ) was added to the CeO22 weight part including the titania-silica protective layer of Example 4 having a thickness of 60 nm, and stirred with a stirrer at 4500 rpm for 30 minutes to prepare a composition for forming an interface adhesive layer.

[0167] Manufacturing steps of membrane-electrode assembly:

[0168] 120 The polymer electrolyte membrane manufactured by the method according to Example 4 o After placing it on a heating plate heated to C, the composition for forming the interfacial adhesive layer was spray-coated on one surface of the polymer electrolyte membrane to form an interfacial adhesive layer (each thickness: 600 nm).

[0169] After coating the above electrode slurry on the release film, 60 o A catalyst layer was prepared by drying at C for 4 hours. The prepared catalyst layer was transferred onto both sides of the polymer electrolyte membrane at 150°C and 1 MPa for 2 minutes to prepare a membrane-electrode assembly.

[0170] <Example 6: Preparation of a membrane-electrode assembly containing a radical scavenger in the electrolyte membrane, unlike Example 4>

[0171] Preparation of a composition for forming a polymer electrolyte membrane:

[0172] Average diameter (D) for 100 parts by weight of total solids of Nafion D-2020 dispersion 50 ) Radical scavenger of the above Example 4 (CeO2 including titania-silica protective layer) having a thickness of 60 nm After adding 2 parts by weight, a composition for forming a polymer electrolyte membrane was prepared by stirring with a stirrer at 4500 rpm for 30 minutes.

[0173] Preparation steps of polymer electrolyte membrane:

[0174] After applying the composition for forming the polymer electrolyte membrane on a glass substrate, the polymer electrolyte membrane was prepared by drying at 120°C for 6 hours and heat-treating at 160°C for 1 hour.

[0175] A membrane-electrode assembly was manufactured in the same manner as in Example 4 above.

[0176] <Example 7: Manufacturing of a membrane-electrode assembly additionally including an interfacial adhesive layer and an electrolyte membrane, unlike Example 4>

[0177] An interfacial adhesive layer was formed on one side of the polymer electrolyte membrane of Example 6 in the manner of Example 5, and a membrane-electrode assembly was manufactured in the same manner as Example 4.

[0178] [Experimental Example 2: Chemical Durability Evaluation]

[0179] Table 1 shows the results of measuring the voltage retention rate after 500 hours by performing the OCV retention method using the chemical durability evaluation protocol of the Department of Energy (DOE) for the membrane-electrode assemblies according to comparative examples, reference examples, and examples 1-1 to 1-3, and 2 to 7. It can be seen that when there is no protective layer, the voltage retention rate drops sharply, whereas when a protective layer is used, the voltage retention rate changes little and is stably maintained.

[0180] Sample (MEA) Comparative Example Reference Example Example 1-1 Example 1-2 Example 1-3 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Protective Layer Not Applicable Bulk Carbon Protective Layer Carbon Protective Layer Carbon Protective Layer Carbon Protective Layer Silica Protective Layer Titania Protective Layer Titania-Silica Protective Layer Titania-Silica Protective Layer Titania-Silica Protective Layer Titania-Silica Protective Layer Interfacial Adhesive Layer XXXXXXXXOXO Electrolyte Membrane XXXXXXXXXOOOCV Retention (%@ After 500 hours) 76% 77% 95% 90% 91% 93% 90% 94% 96% 95% 98%

[0181] Referring to Table 2 above, it can be confirmed that in the reference example where the ratio of the standard deviation of the thickness to the average thickness of the protective layer exceeds 5%, the carbon protective layer is formed in bulk, so that the original function of the radical scavenger cannot be performed. As a result, the membrane-electrode assembly including the radical scavenger of the reference example exhibited a problem in that the voltage retention rate was rapidly reduced after 500 hours. On the other hand, in Example 1-1, since the ratio of the standard deviation of the thickness to the average thickness of the protective layer was 5% or less, the carbon protective layer could be uniformly formed, and accordingly, it could be confirmed that the chemical durability of the membrane-electrode assembly was further improved compared to the reference example.

[0182] When comparing Examples 1-1 to 1-3 from the viewpoint of chemical durability according to the type of radical trapping particle, Example 1-1 using CeO2 as the radical trapping particle showed an effect of further improving chemical durability compared to Example 1-2 using MnO2 as the radical trapping particle and Example 1-3 using Pt nanoparticles.

[0183] In this specification, preferred embodiments of the present invention have been disclosed, and although specific terms have been used, they have been used in a general sense only to easily explain the technical contents of the present invention and to help the understanding of the invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present invention are possible in addition to the embodiments disclosed herein. For example, those skilled in the art will recognize that the radical scavenger, the membrane-electrode assembly, the fuel cell, and the manufacturing method thereof according to the embodiments described with reference to FIGS. 1 to 17 can be modified in various ways. Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the technical idea described in the claims.

[0184] [Explanation of symbols]

[0185] 10: Radical trapping particles

[0186] 20, 20a, 20A, 20b, 20B, 20c, 20C: Protective layer

[0187] 20': Preliminary protective layer

[0188] 21: First material layer

[0189] 22: Second material layer

[0190] 23: Third material layer

[0191] 50, 50a, 50A, 50b, 50B, 50c, 50C: Radical Scavenger

[0192] 110: First electrode

[0193] 115: First interface adhesive layer

[0194] 120: Second electrode

[0195] 125: Second interface adhesive layer

[0196] 130: Polymer electrolyte membrane

[0197] 200: Fuel cell

Claims

1. Radical-scavenging particle; and A protective layer formed on the surface of the radical trapping particle; The ratio of the standard deviation of the thickness to the average thickness of the above protective layer is 5% or less, Radical scavenger.

2. In paragraph 1, The above protective layer is, Containing a titania layer having a multilayer structure, Radical scavenger.

3. In paragraph 1, The above protective layer is, Comprising at least two of a titania layer, a silica layer, and a carbon-based material layer, Radical scavenger.

4. In paragraph 1, The above protective layer has a porous structure, Radical scavenger.

5. In paragraph 1, The above protective layer has a thickness of 0.05 nm or more and 20 nm or less, Radical scavenger.

6. In paragraph 1, The above protective layer is, It is formed by using a vapor adsorption method that vaporizes a given precursor and adsorbs the precursor or a component decomposed from the precursor onto the surface of the radical trapping particle. Radical scavenger.

7. A step of preparing radical-scavenging particles; and A step of forming a protective layer on the surface of the radical trapping particle, comprising: forming the protective layer obtained from the precursor on the surface of the radical trapping particle using a vapor adsorption method of vaporizing a given precursor and adsorbing the precursor or a component decomposed from the precursor onto the surface of the radical trapping particle; Method for manufacturing a radical scavenger.

8. In paragraph 7, The above precursor has a vaporization temperature of 60°C or higher and 250°C or lower, Method for manufacturing a radical scavenger.

9. In paragraph 7, The protective layer comprises at least one of titania, silica and carbon-based materials. Method for manufacturing a radical scavenger.

10. In paragraph 9, The above carbon-based material further comprises at least one hetero element among nitrogen (N), phosphorus (P), and sulfur (S). Method for manufacturing a radical scavenger.

11. In paragraph 7, The above protective layer comprises titania, The precursor comprises at least one of titanium (tetra)isopropoxide, titanium ethoxide, titanium methoxide and titanium tetrachloride as a precursor for forming the titania. Method for manufacturing a radical scavenger.

12. In paragraph 7, The above protective layer contains silica, The precursor comprises at least one of tetraethyl orthosilicate and tetramethyl orthosilicate as a precursor for forming the silica. Method for manufacturing a radical scavenger.

13. In paragraph 7, The above protective layer comprises a carbon-based material, The precursor comprises at least one of phenol-formaldehyde resin, urea-formaldehyde resin and pyrrole as a precursor for forming the carbon-based material. Method for manufacturing a radical scavenger.

14. In paragraph 7, The step of forming the above protective layer is: A step of forming a preliminary protective layer obtained from the above precursor; and A step of performing a heat treatment process on the preliminary protective layer to form the protective layer from the preliminary protective layer; Method for manufacturing a radical scavenger.

15. First electrode; a second electrode positioned spaced apart from the first electrode; and A polymer electrolyte membrane disposed between the first electrode and the second electrode; and A radical scavenger is provided in at least one of the first electrode, the second electrode, and the polymer electrolyte membrane, The radical scavenger has the composition described in claim 1, Membrane-electrode assembly.

16. In paragraph 15, Further comprising an interfacial bonding layer (IBL) disposed between the first electrode and the polymer electrolyte membrane and between the second electrode and the polymer electrolyte membrane; The above interfacial adhesive layer comprises the radical scavenger, Membrane-electrode assembly.

17. A fuel cell comprising a membrane-electrode assembly as described in claim 15.

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