Fuel cell membrane electrode assembly containing linear porous silica nanoparticles and fuel cell containing the same

Abstract

This invention provides a membrane electrode assembly with improved performance and durability in low-humidity environments. [Solution] A membrane electrode assembly for a fuel cell comprising: a first catalyst layer containing linear porous silica; a second catalyst layer containing linear porous silica that does not contain linear porous silica or contains a smaller amount of linear porous silica than the first catalyst layer; and a polymer electrolyte membrane; wherein the first catalyst layer is located between the second catalyst layer and the polymer electrolyte membrane, and the linear porous silica in the first catalyst layer is contained in an amount of 1 to 20% by weight relative to the total weight of the first catalyst layer.

Description

Technical Field

[0001] The present invention relates to a membrane electrode assembly for a fuel cell with improved performance in a low-humidity environment.

Background Art

[0002] A fuel cell is a battery equipped with a power generation system that directly converts chemical reaction energy, such as the oxidation / reduction reaction of hydrogen and oxygen contained in hydrocarbon-based fuel substances like methanol, ethanol, and natural gas, into electrical energy. Due to its high energy efficiency and environmentally friendly characteristics of low pollutant emissions, it has attracted attention as a next-generation clean energy source to replace fossil energy.

[0003] Such a fuel cell has the advantage of being able to output a variety of power ranges through a stack configuration formed by stacking unit cells, and shows an energy density 4 to 10 times that of a small lithium battery, so it has attracted attention as a small and portable power source for mobile use.

[0004] The stack that substantially generates electricity in a fuel cell has a structure in which several to dozens of unit cells composed of a membrane electrode assembly (Membrane Electrode Assembly, MEA) and a separator (or also called a bipolar plate) are stacked. The membrane electrode assembly generally has a structure in which an oxidation electrode (anode or fuel electrode) and a reduction electrode (cathode or air electrode) are formed on both sides with an electrolyte membrane sandwiched between them.

[0005] Fuel cells can be classified into alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells (Polymer Electrolyte Membrane Fuel Cell, PEMFC), etc. according to the state and type of the electrolyte. Among them, polymer electrolyte membrane fuel cells have attracted attention as power supply devices for portable, vehicle, and household use due to advantages such as a low operating temperature below 100°C, fast startup and response characteristics, and excellent durability.

[0006] Typical examples of polymer electrolyte fuel cells include hydrogen ion exchange membrane fuel cells (PEMFCs), which use hydrogen gas as fuel, and direct methanol fuel cells (DMFCs), which use liquid methanol as fuel.

[0007] To summarize the reactions that occur in a polymer electrolyte fuel cell, first, when a fuel such as hydrogen gas is supplied to the oxidation electrode, hydrogen ions (H+) and electrons (e-) are produced by the oxidation reaction of hydrogen at the oxidation electrode. The produced hydrogen ions are transferred to the reduction electrode via the polymer electrolyte membrane, and the produced electrons are transferred to the reduction electrode via an external circuit. Oxygen is supplied to the reduction electrode, and the oxygen combines with the hydrogen ions and electrons to produce water through the reduction reaction of oxygen.

[0008] On the other hand, miniaturization of the fuel cell system is essential for applying fuel cells to FCVs (Fuel Cell Vehicles), which requires the development of membrane electrode assemblies (MEAs) that exhibit excellent power density per unit area. In particular, improving the durability of the MEA catalyst layer is necessary for the practical operation of FCVs. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a membrane electrode assembly with improved performance and durability in low-humidity environments.

[0010] Another object of the present invention is to provide a fuel cell to which the membrane electrode assembly structure is applied, thereby improving performance and durability in low-humidity environments. [Means for solving the problem]

[0011] To achieve the above objective, a membrane electrode assembly for a fuel cell according to one embodiment of the present invention includes a first catalyst layer containing linear porous silica and a polymer electrolyte membrane.

[0012] The pores of the linear porous silica may include one or more forms of silica nanotubes and porous silica nanowires.

[0013] The length of the linear porous silica may be 30 to 3,000 nm.

[0014] The linear porous silica may have a diameter of 10 to 200 nm.

[0015] In the first catalyst layer, the linear porous silica may be present in an amount of 1 to 20% by weight relative to the total weight of the first catalyst layer.

[0016] The ionomer content of the first catalyst layer may be 34 to 40% by weight relative to the total weight of the first catalyst layer.

[0017] The thickness of the first catalyst layer may be 0.2 to 5 μm.

[0018] The first catalyst layer may be located between the second catalyst layer, which contains little to no linear porous silica, and the polymer electrolyte membrane.

[0019] The ionomer content of the first catalyst layer may be even higher than the ionomer content of the second catalyst layer.

[0020] A fuel cell according to another embodiment of the present invention includes the aforementioned membrane electrode assembly for the fuel cell. [Effects of the Invention]

[0021] The membrane electrode assembly of the present invention contains linear porous silica nanoparticles with a large specific surface area in the catalyst layer, so that the catalyst layer can effectively contain the moisture discharged from the electrolyte membrane. Therefore, the problem of reduced ionic conductivity caused by the drying of the electrolyte membrane in a low-humidity environment can be solved.

Brief Description of the Drawings

[0022] [Figure 1] It is a diagram showing various conceptual diagrams of the form of linear porous silica.

[0023] [Figure 2] It is a diagram schematically showing a structure in which linear porous silica is included in the first catalyst layer.

[0024] [Figure 3] It is a schematic diagram showing the overall configuration of the fuel cell.

[0025] [Figure 4] It is a photograph of the linear porous silica used in the embodiment of the present invention taken with a transmission electron microscope (TEM).

[0026] [Figure 5] It is the low-humidity performance evaluation result of the membrane electrode assembly (MEA) manufactured according to the examples and comparative examples of the present invention.

Modes for Carrying Out the Invention

[0027] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described here.

[0028] A fuel cell membrane electrode assembly according to one aspect of the present invention is characterized by containing linear porous silica in the catalyst layer. While the catalyst layer containing linear porous silica can be formed on only one side of the polymer electrolyte membrane, it is also possible to form catalyst layers containing linear porous silica on both sides.

[0029] The pores of linear porous silica may include, for example, one or more forms of silica nanotubes and porous silica nanowires. Figure 1 shows some specific examples of pore forms that can be formed in linear porous silica. Referring to Figure 1, (a) shows a linear microporous silica nanowire as a specific example of porous silica nanowire, demonstrating that pores can be formed to be much smaller than in a linear structure, and even with the formation of fine pores, the specific surface area of ​​silica can be improved compared to when there are no pores. (b) conceptually shows a large tubular pore formed in the linear direction as a specific example of silica nanotubes. (c) shows a horizontal pore structure as a specific example of porous silica nanowire, in which small pores are formed perpendicular to the linear direction, demonstrating that pores are not necessarily limited to the form of holes, and can also exhibit an uneven surface shape on the linear silica. (d) conceptually illustrates a specific example of porous silica nanowires in which pores are irregularly (randomly) formed in linear silica, and examples include linear mesoporous silica nanowires or linear macroporous silica nanowires. (e) illustrates a specific example of porous silica nanowires, showing a vertical pore structure in which multiple fine, elongated pores are formed in the linear direction from linear silica. However, the pore morphology of the linear porous silica of the present invention is not limited to the above examples, and is not limited to the pore morphology as long as it can increase the specific surface area of ​​the linear silica.

[0030] The catalyst layer containing linear porous silica is positioned in contact with the electrolyte membrane and can effectively contain moisture through the large specific surface area of ​​the silica. This suppresses moisture evaporation from the polymer electrolyte membrane, helping the polymer electrolyte membrane and catalyst layer maintain appropriate humidity levels and excellent ion conductivity in low-humidity environments.

[0031] The length of the linear porous silica is preferably 30 to 3,000 nm, 100 to 2,500 nm, 200 to 2,000 nm, or 500 to 1,500 nm. If the length of the porous silica is greater than 3,000 nm, the silica that does not participate in the chemical reaction in the catalyst layer prevents the catalyst and ionomer from being evenly dispersed, resulting in a decrease in content and a reduction in the chemical reaction efficiency of the catalyst layer. Furthermore, if the length of the porous silica is smaller than the above range, pores may not be sufficiently formed in the silica, resulting in a problem where the water content effect of the porous silica is negligible.

[0032] The diameter of the linear porous silica is preferably 10 to 200 nm, 50 to 150 nm, or 70 to 120 nm. If the diameter of the linear porous silica is less than 10 nm, the effect of improving the specific surface area due to the porous properties of silica becomes negligible due to the excessively small diameter. If the diameter of the linear porous silica is greater than 200 nm, the silica greatly interferes with the catalytic reaction and ionomer movement in the catalyst layer, resulting in a significant decrease in the efficiency of the fuel cell.

[0033] Linear porous silica can be manufactured using conventional porous silica manufacturing methods; however, to achieve a linear shape, for example, an AAO (Anodic Aluminum Oxide) membrane can be used as a mold. As an example, the linear porous silica can be manufactured by filling the pores of an AAO membrane with a solution containing a silica precursor containing a pore-forming agent such as a surfactant and silicon, carrying out hydrolysis and condensation reactions, and then calcining. The silica precursor can be, but is not limited to, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, or mixtures thereof. As the surfactant, CTAB (Cetyl Trimethyl Ammonium Bromide), Polyalcohol polyol, ethanol, Polysorbate 20 (or Tween 20), Polysorbate 80 (Tween 80), PVP (Polyvinylpyrrolidone), SDS (Sodium dodecyl sulfate), DoTAB (Dodecyltrimethylammonium Bromide), DeTAB (Decyltrimethylammonium Bromide), Pluronic P123 (Poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol)), Pluronic F127 (Poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol)), or mixtures thereof may be used, but are not limited thereto. The hydrolysis, condensation, and calcination conditions can be appropriately selected by those skilled in the art from ordinary conditions, taking into consideration the reaction conditions and state.

[0034] Figure 2 is a simplified diagram showing the structure of one embodiment of the fuel cell membrane electrode assembly 100 of the present invention. Referring to Figure 2, it is preferable that the linear porous silica 1 is evenly distributed within the first catalyst layer 11, and although the linear porous silica may be distributed separately, two or more linear porous silicas 1 may be distributed within the first catalyst layer 11 with some overlap.

[0035] Linear porous silica helps maintain a moist environment within the membrane electrode assembly in low-humidity environments, but it does not directly participate in the oxidation-reduction reaction of the catalyst layer or in hydrogen ion conduction. Therefore, it is important that it is included in the catalyst layer in an appropriate ratio. Specifically, linear porous silica is preferably included in the first catalyst layer at an amount of 1 to 20% by weight relative to the total weight of the first catalyst layer. If the amount of linear porous silica in the first catalyst layer is less than 1% by weight, the effect of linear porous silica in maintaining a moist environment will be minimal. If the amount of linear porous silica in the first catalyst layer is more than 20% by weight, the oxidation-reduction reaction by the catalyst in the catalyst layer may not occur sufficiently, potentially reducing fuel cell efficiency.

[0036] The first catalyst layer containing linear porous silica contains ionomers, and it is preferable for the ionomer content to be higher than that of a typical catalyst layer without porous silica for smooth hydrogen ion conduction. Specifically, the ionomer content of the first catalyst layer is preferably 34 to 40% by weight relative to the total weight of the first catalyst layer. If the ionomer content in the first catalyst layer is higher than the above range, it inhibits fuel supply to the platinum catalyst active sites, and if the ionomer content in the first catalyst layer is too low, the ion transfer capacity of the catalyst layer is inhibited.

[0037] The ionomer may include one or more ionomers selected from the group consisting of fluorinated ionomers and hydrocarbon ionomers. The hydrocarbon ionomer can be any known hydrocarbon polymer, for example, sulfonated derivatives of poly(aryleneether)s (SPAEs), poly(arylene sulfide)s (SPASs), polyimides (SPIs), polybenzimidazoles (PBIs), polyphenylenes (PPs), or polyether ether ketone (PEEK). The fluorinated polymer can be any known fluorinated polymer, for example, perfluorinated sulfonic acid, polyvinylidene fluoride, hexafluoropropylene, trifluoroethylene, polytetrafluoroethylene, or copolymers thereof.

[0038] However, the ionomer included in the catalyst layer along with the linear porous silica preferably has an equivalent weight (EW) of 600 to 1200 for effective ionic conductivity of the catalyst layer.

[0039] The thickness of the first catalyst layer containing linear porous silica is preferably 0.2 to 5 μm. If the thickness of the first catalyst layer is less than 0.2 μm, the catalyst layer may be too thin to adequately contain linear porous silica, and even if linear porous silica is included in the catalyst layer, the creation of a humid environment in the catalyst layer (improvement of low-humidity characteristics) may not occur sufficiently. Conversely, if the thickness of the first catalyst layer is greater than 5 μm, the efficiency reduction due to the chemical reaction of the catalyst not occurring due to the volume occupied by the porous silica may outweigh the improvement in fuel cell efficiency due to the creation of a humid environment by the inclusion of linear porous silica.

[0040] Therefore, in order to further improve the efficiency of the catalyst layer, the first catalyst layer containing linear porous silica can be formed only in the portion in contact with the polymer electrolyte membrane, and a structure can be applied in which additional catalyst layers containing porous silica or less can be stacked.

[0041] The first catalyst layer may be located between the second catalyst layer and the polymer electrolyte membrane. Here, the second catalyst layer contains linear porous silica in little to no amount, and it is more preferable from the standpoint of battery performance if it contains little to no linear porous silica. If the second catalyst layer contains linear porous silica, its content must be less than that of the first catalyst layer, and may be 1% by weight or more less than that of the first catalyst layer, for example, 1 to 20% by weight, specifically 5% by weight or more, and more specifically 10% by weight or more. Figure 2 shows a simplified membrane electrode assembly 100 as one embodiment of the present invention, in which a multilayer catalyst layer 10 is formed by forming a first catalyst layer 11 on one surface of a polymer electrolyte membrane 20, and a second catalyst layer 12 containing little to no linear porous silica is laminated on the first catalyst layer 11. Figure 2 only discloses a catalyst layer 10 containing the first catalyst layer 11 formed on one surface, but multiple catalyst layers may be formed on both sides of the polymer electrolyte membrane, and the catalyst layer 10 containing the first catalyst layer 11 may be the cathode electrode or the anode electrode, and is not particularly limited.

[0042] In order to further lengthen the hydrogen ion conduction pathway within the catalyst layer due to linear porous silica and to facilitate smooth hydrogen ion conduction between the first and second catalyst layers, it is preferable that the ionomer content of the first catalyst layer 11 in the catalyst layer 10 is greater than that of the second catalyst layer 12, but the present invention is not limited thereto.

[0043] The catalyst layer contains a catalyst, and any catalyst that participates in the reaction of a battery and is normally usable as a catalyst in a fuel cell can be used. Specifically, platinum-based metals can preferably be used.

[0044] Platinum-based metals include, for example, platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), and platinum-M alloys (where M is palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper. The catalyst may include one or more selected from the group consisting of (Cu), silver (Ag), gold (Au), zinc (An), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh), one selected from the group consisting of non-platinum alloys and combinations thereof, and more preferably a combination of two or more metals selected from the platinum-based catalyst metal group may be used, but is not limited thereto, and any platinum-based catalyst metal usable in the art can be used without restriction.

[0045] Specifically, platinum alloys can be used individually or in mixtures of two or more selected from the group consisting of Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Co, Pt-Y, Pt-Ru-W, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, PT-Co, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr-Ir, and combinations thereof.

[0046] Furthermore, non-platinum alloys can be selected from the group consisting of Ir-Fe, Ir-Ru, Ir-Os, Co-Fe, Co-Ru, Co-Os, Rh-Fe, Rh-Ru, Rh-Os, Ir-Ru-Fe, Ir-Ru-Os, Rh-Ru-Fe, Rh-Ru-Os, and combinations thereof, and can be used individually or in mixtures of two or more.

[0047] Such catalysts can be used as catalysts themselves (black), or they can be used supported on a carrier.

[0048] The support material can be selected from carbon-based support materials, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The carbon-based support can be selected from, but is not limited to, graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, Denka Black, acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano- / meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and any combination of one or more of these. Any support available in this art can be used without limitation.

[0049] The catalyst particles may be located on the surface of the support, or they may penetrate into the interior of the support while filling the internal pores.

[0050] When using a precious metal supported on a carrier as a catalyst, commercially available catalysts may be used, or a catalyst manufactured by supporting the precious metal on a carrier may be used. The process of supporting a precious metal on a carrier is widely known in this field, so a detailed explanation in this specification is omitted as it should be easily understood by those working in this field.

[0051] The catalyst particles are contained in catalyst layers 10 and 30 at a concentration of 20% to 80% by weight relative to the total weight. If the concentration is less than 20% by weight, there is a problem of reduced activity, and if it exceeds 80% by weight, there is a problem of reduced catalytic activity due to aggregation of catalyst particles, which reduces the active area.

[0052] Furthermore, the catalyst layers 10 and 30 may contain a binder to improve adhesion and transfer hydrogen ions. It is preferable to use an ion-conducting ionomer as the binder, and since the explanation of ionomers has been given above, a repetitive explanation will be omitted.

[0053] However, ionomers can be used in the form of a single substance or a mixture, and may also be used with non-conductive compounds to selectively improve adhesion to the polymer electrolyte membrane 50. The amount used is preferably adjusted to suit the intended purpose.

[0054] As the non-conductive compound, one or more selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (pVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol may be used.

[0055] The binder may be included in an amount of 20% to 80% by weight relative to the total weight of the catalyst layers 10 and 30. If the binder content is less than 20% by weight, the generated ions may not be properly transferred, and if it exceeds 80% by weight, there may be insufficient pores, making it difficult to supply hydrogen or oxygen (air) and potentially reducing the reactive surface area.

[0056] The electrode substrate can be a porous conductive substrate to ensure smooth supply of hydrogen or oxygen. Typical examples include, but are not limited to, carbon paper, carbon cloth, carbon felt, or metal cloth (referring to a porous film composed of fibrous metal cloth or a cloth formed of polymer fibers with a metal film formed on its surface). Furthermore, it is preferable to use electrode substrates 40 and 40' that have been treated with a fluororesin to prevent a decrease in the diffusion efficiency of reactants due to water generated during the operation of the fuel cell. Suitable fluororesins include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or copolymers thereof.

[0057] Furthermore, the electrode substrate may further contain a microporous layer to enhance the reactant diffusion effect. This microporous layer may generally contain conductive powders with small particle sizes, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fibers, fullerene, carbon nanotubes, carbon nanowires, carbon nanohorns, or carbon nanorings.

[0058] The microporous layer is manufactured by coating an electrode substrate with a composition containing conductive powder, a binder resin, and a solvent. Preferred binder resins include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate, or copolymers thereof. Preferred solvents include alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol, as well as water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran.

[0059] The coating process may be performed using, but is not limited to, screen printing, spray coating, or a coating method using a doctor blade, depending on the viscosity of the composition.

[0060] A fuel cell according to another embodiment of the present invention may include a membrane electrode assembly according to one embodiment of the present invention.

[0061] Figure 3 is a schematic diagram showing the overall configuration of the fuel cell.

[0062] Referring to Figure 3, the fuel cell 200 includes a fuel supply unit 210 that supplies a mixed fuel of fuel and water, a reforming unit 220 that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 in which the reformed gas containing hydrogen gas supplied from the reforming unit 220 undergoes an electrochemical reaction with an oxidizer to generate electrical energy, and an oxidizer supply unit 240 that supplies the oxidizer to the reforming unit 220 and the stack 230.

[0063] The stack 230 comprises multiple unit cells that generate electrical energy by inducing an oxidation / reduction reaction between a reformed gas containing hydrogen gas supplied from the reforming unit 220 and an oxidant supplied from the oxidant supply unit 240.

[0064] Each unit cell represents a cell that generates electricity and includes a membrane electrode assembly that oxidizes / reduces oxygen in a reforming gas containing hydrogen gas and an oxidizing agent, and a separator plate (also called a bipolar plate, hereinafter referred to as "separator plate") for supplying the reforming gas containing hydrogen gas and the oxidizing agent to the membrane electrode assembly. The separator plates are placed on both sides of the membrane electrode assembly, which is placed in the center. In this case, the separator plates located on the outermost edges of the stack are sometimes specifically called end plates.

[0065] One of the separation plates, an end plate, is equipped with a pipe-shaped first supply pipe 231 for injecting reformed gas containing hydrogen gas supplied from the reforming unit 220, and a pipe-shaped second supply pipe 232 for injecting oxygen gas. Another end plate is equipped with a first discharge pipe 233 for discharging reformed gas containing hydrogen gas that remains unreacted in multiple unit cells to the outside, and a second discharge pipe 234 for discharging oxidizer that remains unreacted in the unit cells to the outside.

[0066] In the aforementioned fuel cell, the separator, fuel supply unit, and oxidizer supply unit constituting the electricity generation unit are the same as those used in a normal fuel cell, except that the membrane electrode assembly 100 according to one embodiment of the present invention is used; therefore, a detailed description is omitted in this specification.

[0067] Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0068]

[0069] [Example 1]

[0070] The pores of an AAO membrane (Whatman) were filled with a surfactant (CTAB) and a silica precursor (TEOS), and hydrolysis and condensation reactions were carried out at 90°C for 2 hours. Subsequently, the membrane was calcined at 550°C for 3 hours to obtain microporous silica nanowires with a diameter of 80 nm and a length of 1200 nm, as shown in Figure 1(a).

[0071] A membrane electrode assembly was manufactured according to a normal manufacturing method, except that the cathode was constructed using a first catalyst layer containing 5% by weight of the linear microporous silica nanowires and a second catalyst layer that did not contain silica. In this case, the total thickness of the catalyst layers was 14 μm, and the thickness of the first catalyst layer was 3 μm. Nafion was used as the ionomer, and a platinum catalyst was used.

[0072]

[0073] [Example 2]

[0074] PSS nanoparticles (10 to 70 nm) and silica precursor (TEOS) were filled into the pores of an AAO membrane (Whatman), and hydrolysis and condensation reactions were carried out at 90°C for 2 hours. Subsequently, the mixture was calcined at 550°C for 5 hours to obtain linear mesoporous silica nanowires with a diameter of 100 nm and a length of 1,000 nm, as shown in Figure 1(d). Figure 4 shows the results of TEM analysis of the linear porous silica used in Example 2. Referring to Figure 4, the morphology of linear porous silica with disordered pores can be confirmed.

[0075] The membrane electrode assembly was manufactured in the same manner as in Example 1, except that the linear porous mesoporous silica nanowires manufactured as described above were used.

[0076]

[0077] [Comparative Example 1]

[0078] The film electrode assembly was manufactured using the same method as in Example 1, except that spherical silica (silica nanospheres, size 50 nm) was used instead of silica nanowires and a second catalyst layer was not installed.

[0079]

[0080] [Comparative Example 2]

[0081] Non-porous silica nanowires were obtained by filling the pores of an AAO membrane with only a silica precursor (TEOS) without using a pore-forming agent, and then carrying out hydrolysis and condensation reactions at 90°C for 2 hours.

[0082] The membrane electrode assembly was manufactured in the same manner as in Example 1, except that the non-porous silica nanowires were used.

[0083]

[0084] [Comparative Example 3]

[0085] The membrane electrode assembly was manufactured in the same manner as in Example 2, except that a second catalyst layer containing 20% ​​by weight of linear porous mesoporous silica nanowires was installed.

[0086]

[0087] [Table 1]

[0088]

[0089] [Experimental Example: Performance Comparison of Membrane Electrode Assemblies]

[0090] The performance of the membrane electrode assemblies configured in Table 1 in a low-humidity environment (30% humidity) was evaluated and is shown in Figure 5. Referring to Figure 5, it can be confirmed that the voltage due to current density of Examples 1 and 2 is measured to be significantly higher than that of Comparative Examples 1 and 2 in a low-humidity environment, and in particular, the performance of Example 2, which includes linear mesoporous silica nanowires, is even better.

[0091]

[0092] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art that utilize the basic concepts of the present invention as defined in the following claims also fall within the scope of the present invention.

[0093]

[0094] [Explanation of symbols]

[0095] 100: Membrane electrode assembly

[0096] 1: Linear porous silica

[0097] 10, 30: Electrode

[0098] 11: First catalyst layer 12: Second catalyst layer

[0099] 20:Polymer electrolyte membrane

[0100] 200: Fuel cell 210: Fuel supply section

[0101] 220: Modification section 230: Stack

[0102] 231: 1st supply pipe 232: 2nd supply pipe

[0103] 233: 1st discharge pipe 234: 2nd discharge pipe

[0104] 240: Oxidizing agent supply unit

Claims

1. A first catalyst layer containing linear porous silica, a second catalyst layer containing linear porous silica or not containing linear porous silica, or containing a smaller amount of linear porous silica than the first catalyst layer; and a polymer electrolyte membrane; The first catalyst layer is located between the second catalyst layer and the polymer electrolyte membrane. In the first catalyst layer, the linear porous silica is present in an amount of 1 to 20% by weight relative to the total weight of the first catalyst layer. Membrane electrode assembly for fuel cells.

2. The membrane electrode assembly for a fuel cell according to claim 1, wherein the pores of the linear porous silica include one or more forms of silica nanotubes and porous silica nanowires.

3. The membrane electrode assembly for a fuel cell according to claim 1, wherein the length of the linear porous silica is 30 to 3,000 nm.

4. The fuel cell membrane electrode assembly according to claim 1, wherein the linear porous silica has a diameter of 10 to 200 nm.

5. The membrane electrode assembly for a fuel cell according to claim 1, wherein the ionomer content of the first catalyst layer is 34 to 40% by weight relative to the total weight of the first catalyst layer.

6. The membrane electrode assembly for a fuel cell according to claim 1, wherein the thickness of the first catalyst layer is 0.2 to 5 μm.

7. The membrane electrode assembly for a fuel cell according to claim 1, wherein the ionomer content of the first catalyst layer is greater than the ionomer content of the second catalyst layer.

8. A fuel cell comprising the membrane electrode assembly for a fuel cell according to claim 1.

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