A method for preparing an oxidation stabilizer, an oxidation stabilizer prepared by the method, a method for preparing an ionomer dispersion including the oxidation stabilizer, and an ionomer dispersion prepared by the method

Abstract

The present invention relates to a method for manufacturing an oxidation stabilizer and to a fuel cell electrode and an electrolyte membrane manufactured using the oxidation stabilizer manufactured by the said method. Specifically, the present invention is characterized by a method for manufacturing a core-shell type oxidation stabilizer by modifying the surface of a metal oxide having an electrically neutral surface charge and ionically bonding it with a conductive polymer.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an oxidation stabilizer and to a fuel cell electrode and an electrolyte membrane manufactured using the oxidation stabilizer manufactured by the said method. Specifically, the present invention is characterized by a method for manufacturing a core-shell type oxidation stabilizer by modifying the surface of a metal oxide having an electrically neutral surface charge and ionically bonding it with a conductive polymer. Background Technology

[0002] Oxidation stabilizers have been introduced as chemical radical scavengers to address the issue of fuel cell durability degradation caused by active radicals generated during the operation of polymer electrolyte fuel cells. Representative oxidation stabilizers include ionic oxidation stabilizers in the form of metal salts that can easily ionize into metal ions in aqueous solvents, or metal oxide oxidation stabilizers in the form of oxides of the same metal that possess radical scavenging capabilities. Metal oxide oxidation stabilizers offer good material accessibility as they are readily available in commercially manufactured forms and can be easily introduced into perfluorinated sulfonic acid (PFSA) ionomer dispersions. Furthermore, ionic oxidation stabilizers address the problem of reduced efficacy over time compared to the initial introduction due to the migration of introduced metal ions during fuel cell operation, and the cationic form of the metal (M + ) and the sulfate group (-SO3) at the end of the PFSA side chain - While there is a problem with hydrogen ion conductivity loss due to strong ionic bonding with ), and a limit on the amount introduced to minimize this, metal oxide oxidation stabilizers are preferred and used because they have the advantage of being relatively free from these issues.

[0003] When metal oxide oxidation stabilizers are introduced in particulate form into a PFSA ionomer dispersion, precipitation problems easily occur due to the high density of the metal oxide oxidation stabilizers relative to PFSA. This problem arises because the surface charge of the metal oxide remains neutral in an aqueous alcohol solution, and when directly introduced into an anion-charged PFSA dispersion, self-aggregation occurs, becoming more pronounced as the amount introduced increases. Furthermore, as the particle size becomes progressively smaller and nanoscale is achieved, spontaneous aggregation occurs due to interactions between particle surfaces, and this aggregation cannot be easily resolved even with the application of mechanical stirring or ultrasonic stirring. When aggregated metal oxide nanoparticles exist within an ionomer matrix used as a polymer electrolyte membrane and electrode binder in a fuel cell, they cause incompatibility issues at the interface between the metal oxide and the ionomer. This leads to a weakening of mechanical strength and acts as a cause for reduced reliability and reproducibility of material properties when the fabricated polymer electrolyte membrane and electrode binder are applied. Furthermore, when applied as a polymer electrolyte membrane, the irregularly formed interface causes abnormal permeation of fuel gas, leading to a decrease in performance and durability. Prior art literature

[0004] Korean Patent Publication No. 10-2007-0031133 The problem to be solved

[0005] According to the present invention, the purpose is to provide a method for evenly dispersing metal oxide particles without introducing separate surfactants and dispersants when applying an oxidation stabilizer containing metal oxide particles to a fluorine-based ionomer.

[0006] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become clearer from the following description and will be realized by the means and combinations thereof described in the claims. means of solving the problem

[0007] According to the present invention, a method for manufacturing an oxidation stabilizer is provided, comprising: a preparation step of preparing metal particles; an input step of introducing metal particles into an alkaline solvent; and a mixing step of introducing metal particles into a solvent containing an anion-conducting polymer; wherein, in the input step, the surface of the metal particles is anion-charged, and in the mixing step, the anion-conducting polymer is positively charged.

[0008] The above metal particles may contain metal oxides.

[0009] The above alkaline solvent may contain a basic substance.

[0010] The above basic substance may be contained in the above alkaline solvent at a concentration of 0.001 M to 5 M.

[0011] The above anion-conducting polymer may include at least one anion-conducting functional group among ammonium, imidazolium, and phosphonium.

[0012] In the mixing step, the anion-conducting polymer may be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles.

[0013] In the preparation stage, the surface of the metal particles is in a neutral state, and in the input stage, the surface of the metal particles may be charged with a negative charge.

[0014] In the mixing step, the metal particles with a negatively charged surface and the anionic conductive polymer with a positively charged surface may be ionically bonded.

[0015] The anion-conducting polymer may be ionically bonded in the form of a shell surrounding the metal particles, with the metal particles serving as a core.

[0016] According to the present invention, an oxidation stabilizer is provided that is manufactured by the above-described manufacturing method and has a core-shell structure comprising metal particles in the core and an anion-conducting polymer in the shell.

[0017] The above anion-conducting polymer may be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles.

[0018] According to the present invention, a method for preparing an ionomer dispersion is provided, characterized by comprising the steps of: preparing an ionomer solution containing an ionomer; and adding and mixing an oxidation stabilizer to the ionomer solution.

[0019] The above oxidation stabilizer may be included in an amount of 0.02 to 7 parts by weight based on 100 parts by weight of the ionomer.

[0020] The above ionomer solution may comprise a low-boiling point solvent selected from the group consisting of isopropyl alcohol, ethanol, acetone, and combinations thereof.

[0021] The above ionomer solution may comprise a high-boiling point solvent selected from the group consisting of n-propyl alcohol, ethylene glycol, n-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and combinations thereof.

[0022] According to the present invention, an ionomer dispersion for electrodes is provided, characterized by being prepared by the above method.

[0023] According to the present invention, an ionomer dispersion for an electrolyte membrane is provided, characterized by being prepared by the above method.

[0024] According to the present invention, a fuel cell electrode is provided that is characterized by comprising the above-mentioned ionomer dispersion.

[0025] According to the present invention, a fuel cell electrolyte membrane is provided, characterized by comprising a substrate; and the above-mentioned ionomer dispersion. Effects of the invention

[0026] According to the present invention, a method can be provided to evenly disperse metal oxide particles without introducing separate surfactants and dispersants when applying an oxidation stabilizer containing metal oxide particles to a fluorine-based ionomer.

[0027] The effects of the present invention are not limited to those mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description. Brief explanation of the drawing

[0028] Figure 1 shows a flowchart of the method for manufacturing an oxidation stabilizer according to the present invention. Figure 2 shows a flowchart of the method for preparing an ionomer dispersion according to the present invention. Specific details for implementing the invention

[0029] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0030] In describing each drawing, similar reference numerals have been used for similar components. In the attached drawings, the dimensions of the structures are depicted enlarged from their actual size for clarity of the invention. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0031] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0032] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0033] In this specification, where a range is described for a variable, it will be understood that the variable includes all values ​​within the described range, including the described endpoints of the range. For example, the range “5 to 10” will be understood to include not only the values ​​5, 6, 7, 8, 9, and 10, but also any sub-ranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and any values ​​between integers valid for the category of the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Also, for example, the range “10% to 30%” will be understood to include all integers including values ​​such as 10%, 11%, 12%, 13%, etc. and up to 30%, as well as any sub-range such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between valid integers within the stated range category such as 10.5%, 15.5%, 25.5%, etc.

[0035] The present invention relates to a method for manufacturing an oxidation stabilizer and to a fuel cell electrode and an electrolyte membrane manufactured using the oxidation stabilizer manufactured by the said method.

[0036] FIGS. 1 and 2 show flowcharts relating to the method for manufacturing an oxidation stabilizer and the method for manufacturing an ionomer dispersion of the present invention. With reference to FIGS. 1 and 2, the method for manufacturing an oxidation stabilizer and the method for manufacturing an ionomer dispersion of the present invention will be described, and the composition of each of the oxidation stabilizer and ionomer dispersion manufactured by the above manufacturing method will be described.

[0038] Method for manufacturing an oxidation stabilizer

[0039] The method for manufacturing an oxidation stabilizer according to the present invention includes a preparation step of preparing metal particles, an input step of introducing the metal particles into an alkaline solvent, and a mixing step of introducing the metal particles into a solvent containing an anion-conducting polymer.

[0041] Preparation stage

[0042] This is the step of preparing metal particles.

[0043] The above metal particles are used for the purpose of removing active radicals, etc. generated during fuel cell operation, and preferably may include a metal oxide, and preferably include one metal oxide selected from the group consisting of cerium oxide, zirconium oxide, manganese oxide, aluminum oxide, vanadium oxide, cerium-zirconium oxide and combinations thereof.

[0044] The above metal particles are characterized by being electrically neutral until the surface is modified.

[0046] Input stage

[0047] This is the step of introducing metal particles into an alkaline solvent.

[0048] The above alkaline solvent is used to impart a charge to the surface of the metal particles and may preferably contain a basic substance.

[0049] The above basic substance may include at least one of potassium hydroxide (KOH), sodium hydroxide (NaOH), and ammonia (NH4OH).

[0050] The above basic substance may preferably be included in the above alkaline solvent in an amount of 0.001M to 5M. If the amount is less than 0.001M, it is difficult to form the alkaline conditions necessary to charge the surface of the metal particles to a negative charge, and if the amount exceeds 5M, it may cause damage to the anion-conducting ionomer material.

[0051] The surface of the metal particles is negatively charged due to the basic substance contained in the alkaline solvent.

[0053] Mixing step

[0054] It is a mixing step in which metal particles are introduced into a solvent containing an anion-conducting polymer.

[0055] The above-mentioned anion-conducting polymer is characterized by having a surface that is positively charged and preferably including at least one anion-conducting functional group among ammonium, imidazolium, and phosphonium.

[0056] The metal particles introduced into the solvent have a negatively charged surface, and due to this introduction, the metal particles undergo ionic bonding with the anionic conductive polymer contained in the solvent. That is, an oxidation stabilizer having a core-shell structure is produced by ionic bonding between the metal particles with a negatively charged surface and the anionic conductive polymer with a positively charged surface.

[0057] The core preferably comprises metal particles, and the shell comprises an anion-conducting polymer.

[0058] It is preferable that the above anion-conducting polymer be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles. More specifically, the oxidation stabilizer prepared in the present invention can be applied to both the electrode or the electrolyte membrane of a fuel cell, and the mixing ratio of the metal particles and the anion-conducting polymer may vary depending on the application site.

[0059] In manufacturing an oxidation stabilizer for a fuel cell electrode, it is preferable to use the anion-conducting polymer in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles. If the amount is less than 1 part by weight, the anion-conducting ionomer cannot sufficiently coat the surface of the negatively charged metal particles, making it difficult to form a core-shell structure, and if the amount exceeds 50 parts by weight, unnecessary excess ionomer that does not form ionic bonds with the metal particles is generated.

[0060] In manufacturing an oxidation stabilizer for a fuel cell electrolyte membrane, it is preferable to use the anion-conducting polymer in an amount of 1 to 30 parts by weight based on 100 parts by weight of the metal particles. If the amount is less than 1 part by weight, the anion-conducting ionomer cannot sufficiently cover the surface of the negatively charged metal particles, making it difficult to form a core-shell structure; if the amount exceeds 30 parts by weight, unnecessary excess ionomer that does not form ionic bonds with the metal particles is generated, and there is also a risk that the ion conductivity of the electrolyte membrane will decrease due to the excessive thickness of the shell.

[0062] oxidation stabilizer

[0063] The oxidation stabilizer of the present invention is characterized by being manufactured by the method for manufacturing an oxidation stabilizer of the present invention, and the oxidation stabilizer is characterized by having a core-shell form comprising metal particles in the core and an anion-conducting polymer in the shell.

[0064] In an oxidation stabilizer for a fuel cell electrode, it is preferable that the anion-conducting polymer be included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles.

[0065] In an oxidation stabilizer for a fuel cell electrolyte membrane, it is preferable that the anion-conducting polymer be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the metal particles.

[0067] Method for preparing an ionomer dispersion

[0068] The method for preparing an ionomer dispersion of the present invention is characterized by comprising the steps of preparing an ionomer solution containing an ionomer and adding and mixing an oxidation stabilizer of the present invention into the ionomer solution.

[0069] The above ionomer preferably comprises a fluorine-based ionomer, and, for example, includes perfluorosulfonic acids.

[0070] The composition of the above ionomer solution may vary depending on the site where the above ionomer dispersion is applied. That is, when the ionomer dispersion is applied to an electrode, it contains a low-boiling point solvent, and when the ionomer dispersion is applied to an electrolyte membrane, it contains a high-boiling point solvent.

[0071] The above low-boiling point solvent preferably comprises any one solvent selected from the group consisting of isopropyl alcohol, ethanol, acetone, and combinations thereof.

[0072] The above high-boiling point solvent preferably comprises any one solvent selected from the group consisting of n-propyl alcohol, ethylene glycol, n-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and combinations thereof.

[0073] It is preferable that the above oxidation stabilizer be included in an amount of 0.02 to 7 parts by weight based on 100 parts by weight of the ionomer.

[0074] However, the amount of the oxidation stabilizer prepared in the present invention added to the ionomer solution may vary depending on the application site.

[0075] Specifically, when the above ionomer dispersion is used in an electrode, the oxidation stabilizer may be added in an amount of 0.05 to 7 parts by weight based on 100 parts by weight of the ionomer. At this time, if the amount is less than 0.05 parts by weight, the effect of the oxidation stabilizer is hardly observed, and if the amount exceeds 7 parts by weight, the effect of the oxidation stabilizer becomes saturated, making it impossible to obtain a significant increase in effect, and there is a risk of causing a decrease in the mechanical strength of the electrode.

[0076] When the above ionomer dispersion is used in an electrolyte membrane, the oxidation stabilizer may be added in an amount of 0.02 to 3 parts by weight based on 100 parts by weight of the ionomer. At this time, if the amount is less than 0.02 parts by weight, the effect of the oxidation stabilizer is barely observed, and if the amount exceeds 3 parts by weight, the effect of the oxidation stabilizer becomes saturated, making it impossible to obtain a significant increase in effect, and there is a risk of causing a decrease in the mechanical strength of the electrolyte membrane by inducing aggregation within the ionomer matrix.

[0078] Ionomer dispersion

[0079] The ionomer dispersion of the present invention is characterized by being prepared by the method for preparing an ionomer dispersion of the present invention.

[0080] The above ionomer dispersion can be used as an electrode for a fuel cell or as an electrolyte membrane.

[0082] Electrode / electrolyte membrane for fuel cells

[0083] The ionomer dispersion of the present invention is characterized by being able to be mixed with a metal catalyst and used as an electrode for a fuel cell.

[0084] In addition, the ionomer dispersion of the present invention is characterized in that it can be dried as a single unit and used as an electrolyte membrane for fuel cells, or coated onto a reinforcing film and used as an electrolyte membrane.

[0087] The present invention will be explained in more detail below through specific embodiments. However, these embodiments are intended to illustrate the present invention and do not limit the scope of the present invention.

[0089] ※ Test method

[0090] [Mechanical Strength]

[0091] Mechanical strength was measured using a universal tensile machine (UTM, Model T7000M, KMT, Korea) based on ASTM D882, with a crosshead speed of 10 mm / min and a measurement temperature of 25 degrees.

[0092] [Fluoride Leakage Amount]

[0093] A Fenton solution was prepared by dissolving 0.1 wt.% ferrous ammonium sulfate in 30 wt.% hydrogen peroxide, and the amount of fluoride released was measured using a pH / ISE Meter (Model Orion Star A214, Thermo Fisher Scientific, USA) after reacting the sample at 80 degrees for 2 hours.

[0094] [MEA Performance - Current Density]

[0095] Active area 25 cm 2 The performance of the MEA was measured under conditions of an operating temperature of 65 degrees, RH = 50 / 50 %, and P = 1.0 bar.

[0096] [Electrode Binder Accelerated Durability Characteristics]

[0097] Active area 25 cm 2Under conditions of an operating temperature of 70°C, RH = 100 / 100%, and P = 1.0 bar, the open-circuit voltage (OCV) was gradually reduced to 0.35 V at a rate of 25 mA / sec. After repeating this process, the electrode binder durability characteristics were evaluated by measuring the loss percentage relative to the initial MEA performance (@0.6 V) after 50 hours.

[0098] [Electrolyte Membrane Hydrogen Permeability]

[0099] The hydrogen permeability of the electrolyte membrane was measured by measuring the leak current of the permeated hydrogen gas using Linear Sweep Voltammetry (LSV) with a constant voltage (VMP3, Biologic, France) under operating conditions of 65°C, RH = 50 / 50%, and P = 1.0 bar.

[0100] [Electrolyte Membrane OCV Durability]

[0101] Active area 25 cm 2 , 20% loss relative to the initial open-circuit voltage (OCV) or 15 mA / cm² under conditions of operating temperature 90°C, RH = 30 / 30%, and P = 1.5 bar 2 (@65 o The OCV endurance characteristics of the electrolyte membrane were observed by checking the elapsed time until a crossover exceeding C / 50% RH, 1.0 bar was observed.

[0103] Electrode comparison experiment

[0104] Example 1

[0105] A metal oxide oxidation stabilizer containing cerium oxide is exposed to an aqueous alcohol solution containing 1 M KOH at room temperature for 1 hour to charge its surface charge to (-), and then an anion-conducting ionomer is introduced in an amount of 10 parts by weight relative to the metal oxide to induce ionic bonding with the (-) charged oxidation stabilizer, thereby producing a core-shell structured oxidation stabilizer encapsulated within the anion-conducting ionomer.

[0106] Subsequently, the oxidation stabilizer was separated through a filtration process, and 0.08 parts by weight of the oxidation stabilizer relative to the weight of the negatively charged PFSA ionomer was introduced into an alcohol aqueous solution (low boiling point solvent, 80°C or lower)-based PFSA ionomer dispersion and stirred to prepare a dispersion for the electrode binder. Prior to introduction into the fuel cell electrode as an electrode binder, a film sample excluding the carbon support was prepared by a solution coating method to evaluate mechanical strength and fluorine leaching amount. To this end, the ionomer dispersion excluding the carbon support was cast onto a glass plate, solidified in a vacuum oven set to 60°C for 4 hours, and heat-treated at 200°C for 1 hour to prepare the film sample. Subsequently, film samples were prepared by treating in a boiling 0.5 M aqueous sulfuric acid solution for 2 hours and boiling in ultrapure water for 2 hours to remove excess sulfuric acid (electrode composition). To evaluate the performance and durability of the fuel cell electrode binder, the dispersion prepared above for the electrode binder was mixed with a commercial 40 wt.% Pt / C catalyst (Johnson Matthey, USA) and isopropyl alcohol (IPA, Sigma-Aldrich, USA), and stirred for 30 minutes to prepare an electrode slurry. Subsequently, the cathode and anode, each with a Pt catalyst content of 0.4 mg / cm², were placed on a commercial perfluorosulfonic acid electrolyte membrane, Nafion 211 (DuPont, USA). 2 (Ionomer content 0.25 mg / cm² 2 A membrane-electrode assembly (MEA) was prepared by repeatedly performing spray coating to achieve the desired result.

[0108] Example 2

[0109] A film sample and an electrode binder were prepared in the same manner as in Example 1, except that the content of the introduced oxidation stabilizer was 0.16 wt.% relative to the weight of the PFSA ionomer.

[0111] Example 3

[0112] A film sample and an electrode binder were prepared in the same manner as in Example 1, except that the content of the introduced oxidation stabilizer was 3.00 wt.% relative to the weight of the PFSA ionomer.

[0114] Comparative Example 1

[0115] A metal oxide oxidation stabilizer was introduced into a dispersion of PFSA ionomer dispersed in an aqueous alcohol solution at a concentration of 0.08 wt.% relative to the weight of the PFSA ionomer, and then stirred. The dispersion was cast onto a glass plate, solidified in a vacuum oven set to 60 degrees for 4 hours, and heat-treated at 200 degrees for 1 hour to prepare a film sample. Subsequently, the film sample was treated in a boiling 0.5 M aqueous sulfuric acid solution for 2 hours and boiled in ultrapure water for 2 hours to remove excess sulfuric acid. Additionally, a fuel cell electrode was prepared using the dispersion in the same manner as in Example 1.

[0117] Comparative Example 2

[0118] A film sample and an electrode binder were prepared in the same manner as in Comparative Example 1, except that the content of the introduced oxidation stabilizer was 0.16 wt.% relative to the PFSA ionomer.

[0120] Experimental Example 1

[0121] Membrane-electrode assemblies prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested for mechanical strength, fluorine effluent, MEA performance-current density, and electrode binder accelerated endurance characteristics, and the results are shown in Table 1 below.

[0122] furtherance Electrode binder properties Oxidation stabilizer content [parts by weight] relative to PFSA ionomer Mechanical strength [MPa] Fluoride effluent [ppm] MEA performance [A / cm 2 @0.6V] Electrode Binder Accelerated Durability Characteristics [Loss % Compared to Initial MEA Performance at 0.6V] Example 1 0.08 25 0.52 0.92 8% Example 2 0.16 26 0.45 0.92 4% Example 3 3.00 25 0.32 0.91 1.8% Comparative Example 1 0.08 9 0.88 0.70 15% Comparative Example 2 0.16 NA 0.70 0.61 13%

[0123] Based on the results of Table 1 above, the following conclusions were obtained.

[0124] - Mechanical strength: The mechanical strength of an electrode composition prepared in film form for measuring mechanical strength (Comparative Example 1, film without catalyst) with 0.08 wt.% of an oxidation stabilizer introduced through conventional technology and excluding the carbon support, and an electrode composition prepared through the present invention with the same amount of the same oxidation stabilizer (Example 1), showed that the electrode composition of Example 1 exhibited improved mechanical strength compared to the electrode composition of Comparative Example 1 due to differences in dispersibility.

[0125] The electrode composition of Comparative Example 2, which contains 0.16 wt.% of an oxidation stabilizer—the highest possible content for conventional technology—had very low mechanical strength, making it impossible to measure the strength.

[0126] In the case of Examples 1-3 of the present invention, mechanical strength was maintained regardless of the introduced content due to uniform dispersion.

[0127] - Fluorine leaching amount: It was confirmed that the electrode composition of Example 1 of the present invention, manufactured in film form excluding the carbon support for measuring the fluorine leaching amount, showed a significantly lower fluorine leaching amount compared to the electrode composition of Comparative Example 1.

[0128] - MEA Performance - Current Density: It was confirmed that the fuel cell electrode of the embodiment of the present invention exhibits higher MEA performance compared to the comparative example. In the fuel cell electrode of the comparative example, depending on the content of the introduced oxidation stabilizer, self-aggregation phenomena and interfacial issues among the oxidation stabilizers within the PFSA ionomer matrix are intensified, resulting in a decrease in MEA performance. On the other hand, it was confirmed that the electrode of the embodiment maintains MEA performance above a certain level regardless of the introduction of the oxidation stabilizer, which is a heterogeneous additive, due to improved dispersibility.

[0129] - Electrode binder accelerated durability characteristics: It was confirmed that the fuel cell electrode of the embodiment of the present invention exhibits improved accelerated durability characteristics (Accelerated stress test; AST) compared to the comparative example.

[0130] It was confirmed that the fuel cell electrode of Example 1 has improved accelerated durability characteristics due to uniform dispersion characteristics compared to the fuel cell electrode of Comparative Example 1, which introduced the same amount of the same oxidation stabilizer.

[0131] When the technology of the present invention was applied, the accelerated durability characteristics were continuously improved with increasing content of the oxidation stabilizer, whereas when the existing technology was adopted, the effect of additionally introducing the oxidation stabilizer was insufficient compared to Comparative Example 1, despite introducing an oxidation stabilizer with a high limit content (Comparative Example 2 fuel cell electrode).

[0133] Electrolyte membrane comparison experiment

[0134] Example 4

[0135] A metal oxide oxidation stabilizer is exposed to an aqueous alcohol solution containing 1 M KOH at room temperature for 1 hour to induce a negative surface charge. Then, an anion-conducting ionomer is introduced at 10 wt.% relative to the metal oxide to induce ionic bonding with the negatively charged oxidation stabilizer, thereby preparing an organic-inorganic hybrid oxidation stabilizer with a core-shell structure encapsulated within the anion-conducting ionomer. Subsequently, the organic-inorganic hybrid oxidation stabilizer is separated through a filtration process, and 0.08 wt.% relative to the weight of the negatively charged PFSA ionomer is introduced into a PFSA ionomer dispersion based on an aqueous alcohol solution (high-boiling point solvent, 100–250°C) and stirred. After casting the above dispersion onto a glass plate, it was solidified in a vacuum oven set to 60 degrees for 4 hours and heat-treated at 200 degrees for 1 hour to produce an electrolyte membrane. Subsequently, the electrolyte membrane was prepared by treating it in a boiling 0.5 M aqueous sulfuric acid solution for 2 hours and boiling it in ultrapure water for 2 hours to remove excess sulfuric acid.

[0137] Example 5

[0138] An electrolyte membrane was prepared in the same manner as in Example 4, except that the content of the introduced oxidation stabilizer was 0.16 wt.% relative to the weight of the PFSA ionomer.

[0140] Example 6

[0141] An electrolyte membrane was prepared in the same manner as in Example 4, except that the content of the introduced oxidation stabilizer was 3.00 wt.% relative to the weight of the PFSA ionomer.

[0143] Comparative Example 3

[0144] A metal oxide oxidation stabilizer was introduced into a dispersion of PFSA ionomer dispersed in an aqueous alcohol solution at a concentration of 0.08 wt.% relative to the weight of the PFSA ionomer, and then stirred. The dispersion was cast onto a glass plate, solidified in a vacuum oven set to 60 degrees for 4 hours, and heat-treated at 200 degrees for 1 hour to produce an electrolyte membrane. Subsequently, the electrolyte membrane was treated in a boiling 0.5 M aqueous sulfuric acid solution for 2 hours and boiled in ultrapure water for 2 hours to remove excess sulfuric acid.

[0146] Comparative Example 4

[0147] An electrolyte membrane was prepared in the same manner as Comparative Example 3, except that the content of the introduced oxidation stabilizer was 0.16 wt.% relative to the weight of the PFSA ionomer.

[0149] Experimental Example 2

[0150] Mechanical strength, fluorine effluent, hydrogen permeability, MEA performance-current density, and OCV endurance time were tested on the electrolyte membranes prepared in Examples 4 to 6 and Comparative Examples 3 to 4 above, and the results are shown in Table 2 below.

[0151] furtherance Electrolyte membrane properties Oxidation stabilizer content [parts by weight] relative to PFSA ionomer Mechanical strength [MPa] Fluoride effluent [ppm] Hydrogen permeability [mA / cm²] 2 @0.45V] MEA performance [A / cm 2 @0.6V] OCV Duration[h] Example 4 0.08 25 0.52 2.80 1.12 555 Example 5 0.16 26 0.45 2.72 1.10 700 or more Example 6 3.00 25 0.32 2.73 1.11 700 or more Comparative Example 3 0.08 9 0.88 3.20 0.91 325 Comparative Example 4 0.16 NA 0.70 5.10 0.72 100

[0152] Based on the results of Table 2 above, the following conclusions were obtained.

[0153] - Mechanical strength: The mechanical strength of the electrolyte membrane prepared by introducing 0.08 wt.% of an oxidation stabilizer through conventional technology (Comparative Example 1) and the electrolyte membrane prepared through the present invention with the same amount of the same oxidation stabilizer (Example 1) showed that the electrolyte membrane of Example 1 had improved mechanical strength compared to the electrolyte membrane of Comparative Example 1 due to the difference in dispersibility.

[0154] The electrolyte membrane of Comparative Example 2, containing 0.16 wt.% of an oxidation stabilizer, which is the highest possible content for conventional technology, had very low mechanical strength, making it impossible to measure the strength.

[0155] In the case of Examples 1-3 of the present invention, mechanical strength was maintained regardless of the introduced content due to uniform dispersion.

[0156] - Fluorine effluent amount: It was confirmed that Example 1 of the present invention showed a significantly lower fluorine effluent amount compared to Comparative Example 1.

[0157] - Hydrogen permeability, LSV: It was confirmed that the electrolyte membrane of the embodiment of the present invention exhibits lower hydrogen permeability (Linear Sweep Voltammetry; LSV) compared to the comparative example. While the electrolyte membrane of the comparative example has high hydrogen permeability because the ionomer matrix of the electrolyte membrane and the introduced oxidation stabilizer form a non-uniform interface, the electrolyte membrane of the embodiment shows low hydrogen permeability as a result of improved hydrogen gas barrier properties, which form a uniform interface due to improved dispersibility.

[0158] - MEA Performance - Current Density: It was confirmed that the electrolyte membrane of the embodiment of the present invention exhibits higher MEA performance compared to the comparative example.

[0159] In the electrolyte membrane of the comparative example, depending on the content of the introduced oxidation stabilizer, self-aggregation phenomena and interfacial issues among the oxidation stabilizers within the PFSA ionomer matrix are intensified, resulting in a degradation of MEA performance. On the other hand, it can be confirmed that the electrolyte membrane of the example maintains MEA performance above a certain level regardless of the introduction of the heterogeneous additive, the oxidation stabilizer, due to improved dispersibility.

[0160] - Electrode binder accelerated durability characteristics: It was confirmed that the electrolyte membrane of the embodiment of the present invention exhibits improved OCV (Open Circuit Voltage) durability characteristics compared to the comparative example.

[0161] It was confirmed that the electrolyte membrane of Example 1, compared to Comparative Example 1 which introduced the same amount of the same oxidation stabilizer, has significantly improved OCV durability characteristics due to improved hydrogen barrier properties resulting from uniform dispersion characteristics.

[0162] In the case of the electrolyte membrane of Comparative Example 2, which was manufactured by introducing the highest limit content of oxidation stabilizer when adopting existing technology, it exhibited the lowest durability despite the high content of oxidation stabilizer due to low dispersibility and failure to secure mechanical strength.

Claims

Claim 1 A method for manufacturing an oxidation stabilizer comprising: a preparation step for preparing metal particles; an input step of introducing metal particles into an alkaline solvent; and a mixing step of introducing metal particles into a solvent containing an anion-conducting polymer; wherein, in the input step, the surface of the metal particles is anion-charged, and in the mixing step, the anion-conducting polymer is positively charged. Claim 2 A method for manufacturing an oxidation stabilizer according to claim 1, wherein the metal particles comprise metal oxides. Claim 3 A method for manufacturing an oxidation stabilizer according to claim 1, wherein the alkali solvent comprises a basic substance. Claim 4 A method for manufacturing an oxidation stabilizer according to claim 3, wherein the basic substance is contained in the alkaline solvent at a concentration of 0.001 M to 5 M. Claim 5 A method for manufacturing an oxidation stabilizer according to claim 1, wherein the anion-conducting polymer comprises at least one anion-conducting functional group selected from ammonium, imidazolium, and phosphonium. Claim 6 A method for manufacturing an oxidation stabilizer according to claim 1, wherein in the mixing step, the anion-conducting polymer is included in an amount of 1 to 50 parts by weight based on 100 parts by weight of the metal particles. Claim 7 A method for manufacturing an oxidation stabilizer according to claim 1, wherein the surface of the metal particles is in a neutral state during the preparation stage and the surface of the metal particles is charged with a negative charge during the input stage. Claim 8 A method for manufacturing an oxidation stabilizer according to claim 7, wherein, in the mixing step, the metal particles having a negatively charged surface and the anion-conducting polymer having a positively charged surface are ionically bonded. Claim 9 A method for manufacturing an oxidation stabilizer according to claim 8, wherein the anion-conducting polymer is ionically bonded to the metal particles in a shell form surrounding the metal particles, with the metal particles serving as a core. Claim 10 An oxidation stabilizer manufactured by the manufacturing method of claim 1 above, characterized by having a core-shell structure comprising metal particles in the core and an anion-conducting polymer in the shell. Claim 11 In claim 10, the oxidation stabilizer comprises 1 to 50 parts by weight of the anion-conducting polymer based on 100 parts by weight of the metal particles. Claim 12 A method for preparing an ionomer dispersion characterized by comprising: a step of preparing an ionomer solution containing an ionomer; and a step of adding and mixing the oxidation stabilizer of claim 10 into the ionomer solution. Claim 13 A method for preparing an ionomer dispersion according to claim 12, wherein the oxidation stabilizer is included in an amount of 0.02 to 7 parts by weight based on 100 parts by weight of the ionomer. Claim 14 A method for preparing an ionomer dispersion according to claim 12, wherein the ionomer solution comprises a low-boiling point solvent selected from the group consisting of isopropyl alcohol, ethanol, acetone, and combinations thereof. Claim 15 A method for preparing an ionomer dispersion according to claim 12, wherein the ionomer solution comprises a high-boiling point solvent selected from the group consisting of n-propyl alcohol, ethylene glycol, n-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, and combinations thereof. Claim 16 An ionomer dispersion for electrodes characterized by being manufactured by the method of claim 14 above. Claim 17 An ionomer dispersion for an electrolyte membrane characterized by being prepared by the method of claim 15 above. Claim 18 A fuel cell electrode characterized by comprising the ionomer dispersion of claim 16 above. Claim 19 A fuel cell electrolyte membrane characterized by comprising: a substrate; and the ionomer dispersion of claim 17.

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