MEMBRANE ELECTRODE ASSEMBLY FOR FUEL CELLS CONTAINING LINEAR POROUS SILICA NANOPARTICLES AND FUEL CELLS CONTAINING SAME - Patent application

Abstract

The present invention relates to a membrane electrode assembly for a fuel cell and a fuel cell including the same, and more particularly to a membrane electrode assembly for a fuel cell including linear porous silica in a catalyst layer, which improves fuel cell performance in a low humidification environment, and a fuel cell including the same.

Description

[Technical field]

[0001] The present invention relates to a membrane electrode assembly for a fuel cell with improved performance in low humidification environments. [Background technology]

[0002] Fuel cells are batteries 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 fuel substances such as methanol, ethanol, and natural gas, into electrical energy. Due to their environmentally friendly characteristics of high energy efficiency and low pollutant emissions, fuel cells are attracting attention as a next-generation clean energy source to replace fossil energy.

[0003] Fuel cells have the advantage of being able to produce a wide range of output power due to their stack configuration made up of stacked unit cells, and they are attracting attention as a small and portable power source for mobile use because they have an energy density four to ten times that of small lithium batteries.

[0004] The stack, which actually generates electricity in a fuel cell, has a structure in which several to several tens of unit cells, each consisting of a membrane electrode assembly (MEA) and a separator (also called a bipolar plate), are stacked together. The membrane electrode assembly generally has a structure in which an oxidizing electrode (anode or fuel electrode) and a reducing electrode (cathode or air electrode) are formed on either side of an electrolyte membrane.

[0005] Fuel cells can be classified into alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells (PEMFC), etc. depending on the state and type of electrolyte. Among them, polymer electrolyte fuel cells are attracting attention as portable, vehicle and home power sources due to their advantages such as low operating temperature of less than 100℃, fast start-up and response characteristics and excellent durability.

[0006] Representative examples of polymer electrolyte fuel cells include the Proton Exchange Membrane Fuel Cell (PEMFC), which uses hydrogen gas as fuel, and the Direct Methanol Fuel Cell (DMFC), which uses liquid methanol as fuel.

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

[0008] Meanwhile, in order to apply fuel cells to FCVs (Fuel Cell Vehicles), it is essential to miniaturize the fuel cell system, which requires the development of a membrane electrode assembly (MEA) that exhibits excellent power density per unit area. In particular, the durability of the MEA catalyst layer needs to be improved for the practical operation of FCVs. Summary of the Invention [Problem to be solved by the invention]

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

[0010] Another object of the present invention is to provide a fuel cell to which the membrane electrode assembly structure is applied, which has improved performance and durability in a low humidification environment. [Means for solving the problem]

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

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

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

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

[0015] The linear porous silica in the first catalytic layer may be included in an amount of 1 to 20 wt % based on the total weight of the first catalytic layer.

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

[0017] The first catalyst layer may have a thickness of 0.2 to 5 μm.

[0018] The first catalyst layer may be located between a second catalyst layer that is free of or contains a reduced amount of linear porous silica and the polymer electrolyte membrane.

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

[0020] A fuel cell according to another embodiment of the present invention includes the above-described fuel cell membrane electrode assembly. Effect of the Invention

[0021] The membrane electrode assembly of the present invention contains linear porous silica nanoparticles having a large specific surface area in the catalyst layer, which allows the catalyst layer to effectively contain moisture discharged from the electrolyte membrane, thereby solving the problem of reduced ionic conductivity caused by the electrolyte membrane drying out in a low-humidity environment. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows various conceptual diagrams for linear porous silica morphology.

[0023] [Diagram 2] FIG. 2 is a schematic diagram showing a structure in which linear porous silica is included in a first catalyst layer.

[0024] [Diagram 3] FIG. 2 is a schematic diagram showing the overall configuration of the fuel cell.

[0025] [Figure 4] 1 is a transmission electron microscope (TEM) photograph of linear porous silica used in an embodiment of the present invention.

[0026] [Diagram 5] 1 shows the results of evaluating low humidification performance of membrane electrode assemblies (MEAs) manufactured according to examples and comparative examples of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor memory device according to an embodiment of the present invention;

[0028] According to one aspect of the present invention, a fuel cell membrane electrode assembly includes a catalyst layer including linear porous silica. The catalyst layer including linear porous silica may be formed on only one side of a polymer electrolyte membrane, or the catalyst layers including linear porous silica may be formed on both sides of the polymer electrolyte membrane.

[0029] The pores of the linear porous silica may include, for example, one or more of a silica nanotube and a porous silica nanowire. FIG. 1 shows some specific examples of pore shapes that can be formed in the linear porous silica. Referring to FIG. 1, (a) shows a linear microporous silica nanowire as a specific example of the porous silica nanowire, and indicates that the pores can be formed very small compared to the linear structure, and even if fine pores are formed, the specific surface area of ​​the silica can be improved compared to the case where there are no pores. (b) conceptually shows, as a specific example of the silica nanotube, a tube-shaped large pore formed in a linear direction. (c) shows, as a specific example of the porous silica nanowire, a horizontal pore structure in which small pores are formed perpendicular to the linear direction, and the pores are not necessarily limited to the shape of holes, and the linear silica surface can also have an uneven shape. (d) is a conceptual diagram showing pores formed irregularly (randomly) in linear silica as a specific example of a porous silica nanowire, and examples thereof include linear mesoporous silica nanowires and linear macroporous silica nanowires. (e) is a diagram showing a vertical pore structure in which a plurality of fine, long pores are formed in the linear direction from linear silica as a specific example of a porous silica nanowire. However, the pore shape of the linear porous silica of the present invention is not limited to the above examples, and is not limited to the pore shape as long as it can increase the specific surface area of ​​linear silica.

[0030] The catalyst layer including linear porous silica is positioned in contact with the electrolyte membrane and can effectively contain moisture through the large specific surface area of ​​silica, thereby suppressing water evaporation from the polymer electrolyte membrane, and helping the polymer electrolyte membrane and catalyst layer to maintain appropriate humidity in a low humidity environment and maintain excellent ion conductivity.

[0031] The length of the linear porous silica may be 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 catalyst and ionomer of the catalytic layer cannot be evenly dispersed and arranged due to the silica that does not participate in the chemical reaction in the catalytic layer, and the content is reduced, resulting in a problem of reduced chemical reaction efficiency of the catalytic layer. In addition, if the length of the porous silica is smaller than the above range, there is a possibility that pores are not sufficiently formed in the silica, resulting in a problem of insignificant moisture absorption effect of the porous silica.

[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 characteristics of the silica is insignificant due to the excessively small diameter, and if the diameter of the linear porous silica is more than 200 nm, the silica significantly interferes with the catalytic reaction and the movement of the ionomer in the catalyst layer, resulting in a significant decrease in the efficiency of the fuel cell.

[0033] The linear porous silica can be prepared by using a conventional method for preparing porous silica, but in order to obtain 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 prepared by filling the pores of an AAO membrane with a solution containing a pore-forming agent such as a surfactant and a silica precursor containing silicon, performing 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 a mixture thereof. The surfactant may be, but is not limited to, 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 a mixture thereof. The hydrolysis, condensation, and baking conditions may be appropriately selected from ordinary conditions by a person skilled in the art in consideration of reaction conditions and conditions.

[0034] Fig. 2 is a simplified diagram showing an embodiment of the structure of a fuel cell membrane electrode assembly 100 of the present invention. Referring to Fig. 2, it is preferable that the linear porous silica 1 is uniformly distributed in the first catalyst layer 11, and each linear porous silica may be distributed separately, but two or more linear porous silica 1 may be distributed in the first catalyst layer 11 in a partially overlapping state.

[0035] Although linear porous silica helps maintain a moist environment in the membrane electrode assembly in a low humidity environment, it is not directly involved in the oxidation-reduction reaction of the catalyst layer or in hydrogen ion conduction, so it is important that it is contained in an appropriate ratio in the catalyst layer. Specifically, the linear porous silica in the first catalyst layer is preferably contained in an amount of 1 to 20 wt% based on the total weight of the first catalyst layer. If the linear porous silica is contained in the first catalyst layer at less than 1 wt%, the effect of maintaining a moist environment by the linear porous silica is insignificant, and if the linear porous silica is contained in the first catalyst layer at more than 20 wt%, the oxidation-reduction reaction by the catalyst of the catalyst layer may not occur sufficiently, which may reduce the efficiency of the fuel cell.

[0036] The first catalytic layer containing linear porous silica contains an ionomer, and it is preferable that the ionomer content is higher than that of a typical catalytic layer not containing porous silica for smooth conduction of hydrogen ions. Specifically, the ionomer content of the first catalytic layer is preferably 34 to 40 wt% based on the total weight of the first catalytic layer. If the ionomer content in the first catalytic layer is higher than the above range, it inhibits the supply of fuel to the platinum catalytic active sites, and if the ionomer content in the first catalytic layer is too low, it inhibits the ion transfer ability of the catalytic layer.

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

[0038] However, it is preferred that the ionomer included in the catalyst layer along with the linear porous silica comprises an ionomer having an equivalent weight (EW) of 600 to 1200 for effective ionic conductivity of the catalyst layer.

[0039] The thickness of the first catalytic layer containing linear porous silica is preferably 0.2 to 5 μm. If the thickness of the first catalytic layer is less than 0.2 μm, the catalytic layer may be so thin that linear porous silica is not sufficiently contained inside the catalytic layer, and even if linear porous silica is contained inside the catalytic layer, the formation of a moist environment (improvement of low humidification characteristics) of the catalytic layer may not occur sufficiently. On the other hand, if the thickness of the first catalytic layer is more than 5 μm, there may be a problem that the efficiency of the fuel cell is improved by creating a moist environment due to the inclusion of linear porous silica, but the decrease in efficiency due to the lack of catalytic chemical reaction due to the volume occupied by the porous silica is greater than the improvement in efficiency of the fuel cell.

[0040] Therefore, in order to further improve the efficiency of the catalyst layer, the first catalyst layer containing linear porous silica is formed only in the portion in contact with the polymer electrolyte membrane, and a structure in which a catalyst layer containing no or a smaller amount of porous silica is additionally laminated can be applied.

[0041] The first catalyst layer may be located between the second catalyst layer and the polymer electrolyte membrane. Here, the second catalyst layer does not contain linear porous silica or contains a smaller amount of linear porous silica, and it is more preferable in terms of cell performance that the second catalyst layer does not contain linear porous silica or contains almost no linear porous silica. If the second catalyst layer contains linear porous silica, the content of the linear porous silica should be less than that of the first catalyst layer, and may be less than that of the first catalyst layer by 1% by weight or more, for example, 1 to 20% by weight, specifically 5% by weight or more, more specifically 10% by weight or more. FIG. 2 shows a membrane electrode assembly 100 having a multi-layered catalyst layer 10 formed by laminating a first catalyst layer 11 on one side of a polymer electrolyte membrane 20 and a second catalyst layer 12 containing no linear porous silica or a smaller amount of linear porous silica on the first catalyst layer 11, as an embodiment of the present invention. FIG. 2 shows only one surface on which the catalyst layer 10 including the first catalyst layer 11 is formed, but multiple catalyst layers may be formed on both surfaces of the polymer electrolyte membrane, and the catalyst layer 10 including the first catalyst layer 11 may be a cathode electrode or an anode electrode, and is not particularly limited.

[0042] In order to further lengthen the hydrogen ion conduction path in the catalyst layer by the linear porous silica and facilitate 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 the ionomer content 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 cell reaction and can be used as a catalyst for a normal fuel cell can be used. Specifically, a platinum-based metal can be preferably used.

[0044] Examples of platinum-based metals include platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys (wherein 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 (Cu). The platinum-based catalytic metal may include any one selected from the group consisting of platinum (Cu), silver (Ag), gold (Au), zinc (An), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La) and rhodium (Rh), non-platinum alloys and combinations thereof. More preferably, a combination of two or more metals selected from the platinum-based catalytic metal group may be used, but is not limited thereto, and any platinum-based catalytic metal usable in the present technical field may be used without limitation.

[0045] Specifically, the platinum alloy may be 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, and may be used alone or in combination of two or more.

[0046] In addition, the non-platinum alloy 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 alone or in combination of two or more.

[0047] Such a catalyst can be used as a catalyst black or can be supported on a carrier.

[0048] The support can be selected from carbon-based supports, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The carbon-based support may be selected from 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 one or more combinations thereof, but is not limited thereto, and any support available in the art may be used without limitation.

[0049] The catalyst particles may be located on the surface of the support and may permeate the interior of the support, filling the interior pores of the support.

[0050] When using a precious metal supported on a carrier as a catalyst, a commercially available product may be used, or a catalyst produced by supporting a precious metal on a carrier may be used. The process of supporting a precious metal on a carrier is widely known in the art, and therefore, even if a detailed description is omitted in this specification, it is easily understandable to those who are engaged in the art.

[0051] The catalyst particles are contained in an amount of 20 to 80% by weight based on the total weight of the catalyst layers 10 and 30. If the amount is less than 20% by weight, there is a problem of reduced activity, and if the amount is more than 80% by weight, there is a problem of reduced catalytic activity due to agglomeration of the catalyst particles, which reduces the active area.

[0052] In addition, the catalyst layers 10 and 30 may contain a binder to improve adhesion and transport hydrogen ions. It is preferable to use an ionomer having ion conductivity as the binder. The ionomer has been described above, so a repeated description will be omitted.

[0053] However, the ionomer may be used alone or in the form of a mixture, and may be used selectively together with a non-conductive compound for the purpose of further improving the adhesive strength with the polymer electrolyte membrane 50. The amount of the ionomer used is preferably adjusted according to the purpose of use.

[0054] As the non-conductive compound, one or more selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), ethylene / tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene 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 wt % to 80 wt % based on the total weight of the catalyst layers 10 and 30. If the binder content is less than 20 wt %, the generated ions may not be transferred well, and if it exceeds 80 wt %, the pores may be insufficient, making it difficult to supply hydrogen or oxygen (air), and the active area for reaction may be reduced.

[0056] The electrode substrate may be a porous conductive substrate so that hydrogen or oxygen can be smoothly supplied. Representative examples include, but are not limited to, carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film made of fibrous metal cloth or a cloth made of polymeric fibers on which a metal film is formed). In addition, it is preferable to use electrode substrates 40, 40' that have been treated with a fluorine-based resin for water repellency, since this prevents a decrease in the reactant diffusion efficiency due to water generated during the operation of the fuel cell. As the fluorine-based resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkylvinyl ether, polyperfluorosulfonyl fluoride alkoxyvinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or copolymers thereof may be used.

[0057] Also, a microporous layer for enhancing the reactant diffusion effect in the electrode substrate may be further included. The microporous layer may include a conductive powder having a generally small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nano-horn, or carbon nano ring.

[0058] The microporous layer is produced by coating a composition containing a conductive powder, a binder resin, and a solvent on an electrode substrate. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkylvinyl ether, polyperfluorosulfonyl fluoride, alkoxyvinyl ether, polyvinyl alcohol, cellulose acetate, or copolymers thereof can be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol, water, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, and tetrahydrofuran can be preferably used.

[0059] The coating process may be performed by, but is not limited to, a screen printing method, a spray coating method, 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 an embodiment of the present invention.

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

[0062] Referring to FIG. 3, the fuel cell 200 includes a fuel supply unit 210 that supplies a mixed fuel obtained by mixing fuel and water, a reformer 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 reformer 220 undergoes an electrochemical reaction with an oxidant to generate electrical energy, and an oxidant supply unit 240 that supplies an oxidant to the reformer 220 and the stack 230.

[0063] The stack 230 includes a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between the reformed gas, including hydrogen gas, supplied from the reformer 220 and the oxidant supplied from the oxidant supplying unit 240 .

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

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

[0066] In the fuel cell, except that the membrane electrode assembly 100 according to one embodiment of the present invention is used, the separator, fuel supply unit and oxidant supply unit constituting the electricity generating unit are the same as those used in conventional fuel cells, and therefore detailed description thereof will be omitted in this specification.

[0067] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may be embodied in various different forms and should not be construed as being limited to the embodiments set forth herein.

[0068]

[0069] [Example 1]

[0070] A surfactant (CTAB) and a 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. Then, it was calcined at 550°C for 3 hours to obtain linear 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 conventional manufacturing method, except that a cathode was constructed using a first catalyst layer containing 5 wt% of the linear microporous silica nanowires and a second catalyst layer containing no silica. At this time, 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. Then, it 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, linear porous silica morphology with disordered pores can be confirmed.

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

[0076]

[0077] [Comparative Example 1]

[0078] A membrane electrode assembly was manufactured in the same manner as in Example 1, except that spherical silica (silica nanospheres, size 50 nm) was used instead of silica nanowires and the second catalyst layer was not provided.

[0079]

[0080] [Comparative Example 2]

[0081] Without using a pore-forming agent, only the silica precursor (TEOS) was filled into the pores of the AAO membrane, and hydrolysis and condensation reactions were carried out at 90°C for 2 hours to obtain non-porous silica nanowires.

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

[0083]

[0084] [Comparative Example 3]

[0085] A membrane electrode assembly was prepared in the same manner as in Example 2, except that a second catalyst layer containing linear porous mesoporous silica nanowires in an amount of 20 wt % was provided.

[0086]

[0087] [Table 1]

[0088]

[0089] [Experimental example: Performance comparison of membrane electrode assemblies]

[0090] The performance of the membrane electrode assemblies according to the configurations in Table 1 in a low humidity environment (humidity 30%) was evaluated and is shown in Figure 5. Referring to Figure 5, it can be seen that the voltages according to the current density of Examples 1 and 2 are measured to be significantly higher than those of Comparative Examples 1 and 2 in a low humidity environment, and in particular, it can be seen that the performance of Example 2 including linear mesoporous silica nanowires is more excellent.

[0091]

[0092] Although the 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 made by those skilled in the art using the basic concept of the present invention 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: Reforming section 230: Stack

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

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

[0104] 240: Oxidant supply unit

Claims

1. a first catalyst layer comprising linear porous silica; and A membrane electrode assembly for a fuel cell comprising: a polymer electrolyte membrane.

2. 2. The fuel cell membrane electrode assembly of claim 1, wherein the linear porous silica pores include at least one of a silica nanotube and a porous silica nanowire.

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

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

5. 2. The membrane electrode assembly for a fuel cell according to claim 1, wherein the linear porous silica in the first catalyst layer is contained in an amount of 1 to 20 wt % based on the total weight of the first catalyst layer.

6. 2. 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 wt % based on the total weight of the first catalyst layer.

7. 2. The fuel cell membrane electrode assembly of claim 1, wherein the first catalyst layer has a thickness of 0.2 to 5 [mu]m.

8. 2. The fuel cell membrane electrode assembly according to claim 1, wherein the first catalyst layer is located between a second catalyst layer that is free of linear porous silica or that contains a smaller amount of linear porous silica and the polymer electrolyte membrane.

9. 9. The fuel cell membrane electrode assembly of claim 8, wherein the ionomer content of the first catalyst layer is greater than the ionomer content of the second catalyst layer.

10. A fuel cell comprising the fuel cell membrane electrode assembly of any one of claims 1 to 9.

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