Polymer electrolyte membrane fuel cell comprising a bipolar plate without flow channels

Abstract

The present invention relates to a polymer electrolyte membrane fuel cell comprising a separator plate without flow channels. By including a hydrophobically coated metal gas diffusion layer and a separator plate without flow channels, corrosion can be prevented even during long-term operation, and structural deformation of the gas diffusion layer and loss of constituent materials can be prevented. Furthermore, water discharge capability, reaction gas (oxygen) supply efficiency, and fuel cell performance can be improved.

Description

Technology Field

[0001] The present invention relates to a polymer electrolyte membrane fuel cell comprising a separator plate without a Euro channel. Background Technology

[0002] Recently, with the prediction of the depletion of conventional energy resources such as oil and coal, interest in alternative energy sources is growing. As one such alternative energy source, fuel cells are highly efficient and NO x and SO x It is receiving particular attention due to advantages such as not emitting pollutants and having an abundant supply of fuel.

[0003] A fuel cell is a power generation system that converts the chemical reaction energy between a fuel and an oxidizer into electrical energy; typically, hydrocarbons such as hydrogen, methanol, and butane are used as fuels, and oxygen is used as the oxidizer.

[0004] In a fuel cell, the most basic unit for generating electricity is the membrane-electrode assembly (MEA), which consists of an electrolyte membrane and anode and cathode electrodes formed on both sides of the membrane. At the anode electrode, the oxidation of the fuel occurs, generating hydrogen ions and electrons. Hydrogen ions move through the electrolyte membrane to the cathode electrode, where oxygen (the oxidizing agent) reacts with the hydrogen ions and electrons transferred through the membrane to produce water. This reaction causes the movement of electrons to the external circuit.

[0005] Fuel cells include Polymer Electrolyte Membrane Fuel Cells (PEMFC; also known as Proton Exchange Membrane Fuel Cells), Direct Methanol Fuel Cells (DMFC), Phosphoric Acid Fuel Cells (PAFC), Alkaline Fuel Cells (AFC), Molten Carbonate Fuel Cells (MCFC), and Solid Oxide Fuel Cells (SOFC). Among these, Polymer Electrolyte Membrane Fuel Cells are being actively researched due to their high energy density and output.

[0006] Figure 1 is an exploded view showing the configuration of a polymer electrolyte membrane fuel cell according to the prior art. Referring to Figure 1, the conventional gas diffusion layer used in polymer electrolyte membrane fuel cells was fabricated based on carbon fiber or carbon black. However, at the stage of commercialization of polymer electrolyte membrane fuel cells, carbon-based gas diffusion layers faced various problems in terms of durability. Specifically, carbon-based gas diffusion layers had problems such as microporous layer detachment, loss of other resins, fillers, and Teflon on the substrate surface, carbon corrosion, hydrophilization of the gas diffusion layer, carbon fiber cutting, reduction of substrate surface rigidity, deformation of the gas diffusion layer structure, thickness variation, limitations in thinning the gas diffusion layer, performance variation caused by process quality variation during mass production, and uneven control of the penetration rate of the microporous layer into the substrate surface.

[0007] Therefore, there is an urgent need to develop technology that can improve the durability of the gas diffusion layer and enhance capillary pressure by controlling the material and the size of the micropores contained therein, thereby facilitating the removal of water generated by the reduction reaction in fuel cells and improving the power generation efficiency of fuel cells. The problem to be solved

[0008] The problem that the present invention aims to solve is to provide a polymer electrolyte membrane fuel cell comprising a separator plate without flow channels that can easily remove water generated by a reduction reaction in the fuel cell and improve the power generation efficiency of the fuel cell.

[0009] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0010] According to one aspect of the present invention, a polymer electrolyte membrane fuel cell is provided, comprising: a membrane electrode assembly (MEA); a pair of gas diffusion layers positioned opposite each other with the membrane electrode assembly in between; and a separator plate positioned on each of the opposite sides of the faces of the pair of gas diffusion layers, wherein at least one of the pair of gas diffusion layers is a hydrophobic coated metal gas diffusion layer, and the separator plate adjacent to the hydrophobic coated metal gas diffusion layer is in the form of a frame. Effects of the invention

[0011] A polymer electrolyte membrane fuel cell according to one embodiment of the present invention includes a hydrophobic coated metal gas diffusion layer, thereby preventing corrosion even during long-term operation and preventing structural deformation of the gas diffusion layer and loss of constituent materials. In addition, water discharge capability can be improved, and a separator without flow channels can be used.

[0012] A polymer electrolyte membrane fuel cell according to one embodiment of the present invention includes a frame-shaped separator plate without flow channels, thereby improving water discharge capacity and reaction gas (oxygen) supply efficiency, and thus can improve the performance of the fuel cell.

[0013] A polymer electrolyte membrane fuel cell according to one embodiment of the present invention can improve water discharge capability by including a metal gas diffusion layer that is hydrophobically coated and has a microporous layer formed therein, and can use a separator plate without flow channels. In addition, the interfacial resistance between the metal gas diffusion layer that is hydrophobically coated and has a microporous layer formed therein and the catalyst layer of the membrane electrode assembly can be reduced, and the performance of the fuel cell can be improved.

[0014] The effects of the present invention are not limited to those described above, and unmentioned effects will be clearly understood by those skilled in the art from this specification. Brief explanation of the drawing

[0015] Figure 1 is an exploded view showing the configuration of a polymer electrolyte membrane fuel cell according to the prior art. Figure 2 is an exploded view showing a polymer electrolyte membrane fuel cell using a separator plate with a hydrophobic coated metal gas diffusion layer and a flow channel of Comparative Example 2. Figure 3 is an exploded view showing the configuration of a polymer electrolyte membrane fuel cell using a hydrophobic coated metal gas diffusion layer and a separator without flow channels of Example 1. Figure 4 shows the configuration of a polymer electrolyte membrane fuel cell using a metal gas diffusion layer with a hydrophobic coating and a microporous layer formed therein, and a separator plate without flow channels. FIG. 5 shows a separator plate with a Euro channel and a separator plate without a Euro channel according to the present invention. Figure 6 shows the current density measurement results of a hydrophobic coated metal gas diffusion layer according to the concentration of polytetrafluoroethylene aqueous solution. Figure 7a shows the polarization curves of the polymer electrolyte membrane fuel cells prepared in Example 1 and Comparative Example 1, measured under conditions of 30% relative humidity. Figure 7b shows the polarization curves of the polymer electrolyte membrane fuel cells prepared in Example 1 and Comparative Example 1, measured under conditions of 100% relative humidity. Figure 8a shows the polarization curves of the polymer electrolyte membrane fuel cells prepared in Example 2 and Comparative Example 1, measured under conditions of 30% relative humidity. FIG. 8b shows the polarization curves of the polymer electrolyte membrane fuel cells prepared in Example 2 and Comparative Example 1, measured under conditions of 100% relative humidity. Figure 9a shows the polarization curves of polymer electrolyte membrane fuel cells prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3, measured under conditions of 30% relative humidity. Figure 9b shows the polarization curves of polymer electrolyte membrane fuel cells prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3, measured under conditions of 100% relative humidity. Fig. 10a is at a relative humidity of 30% and 1.0 A / cm² 2 This shows the results of electrochemical impedance measurements of the polymer electrolyte membrane fuel cells prepared in Example 1 and Comparative Example 1, measured under conditions. Fig. 10b is at 100% relative humidity and 2.0 A / cm² 2 This shows the results of electrochemical impedance measurements of the polymer electrolyte membrane fuel cells prepared in Example 1 and Comparative Example 1, measured under conditions. Fig. 11a is at a relative humidity of 30% and 1.0 A / cm² 2 This shows the results of electrochemical impedance measurements of the polymer electrolyte membrane fuel cells prepared in Example 2 and Comparative Example 1, measured under conditions. Fig. 11b is at 100% relative humidity and 2.0 A / cm² 2 This shows the results of electrochemical impedance measurements of the polymer electrolyte membrane fuel cells prepared in Example 2 and Comparative Example 1, measured under conditions. Fig. 12a is at a relative humidity of 30% and 1.0 A / cm² 2This shows the results of electrochemical impedance measurements of polymer electrolyte membrane fuel cells prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3 under conditions. Fig. 12b is at 100% relative humidity and 2.0 A / cm² 2 This shows the results of electrochemical impedance measurements of polymer electrolyte membrane fuel cells prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3 under conditions. Specific details for implementing the invention

[0016] In this specification, when a part is described as "comprising" a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0017] Throughout the entire specification, the unit "parts by weight" may refer to the ratio of weight between each component.

[0018] Throughout this specification, terms including ordinal numbers, such as "first" and "second," are used for the purpose of distinguishing one component from another and are not limited by said ordinal numbers. For example, within the scope of the invention, the first component may also be named the second component, and similarly, the second component may be named the first component.

[0019] Throughout this specification, the “thickness direction” may mean a direction extending from one surface where one metal plate and another metal plate come into contact to the other surface of the one metal plate, the “length direction” may mean a direction extending from one surface of the one metal plate, excluding the surface where one metal plate and another metal plate come into contact, to the other surface of the one metal plate, the “width direction” may mean a direction extending from one surface of the one metal plate, excluding the surface where one metal plate and another metal plate come into contact, to the other surface of the one metal plate, and the “length direction” may mean a direction that is longer than the “width direction.”

[0020] The present invention will be described in more detail below.

[0021] One embodiment of the present invention provides a polymer electrolyte membrane fuel cell comprising: a membrane electrode assembly (MEA); a pair of gas diffusion layers positioned opposite each other with the membrane electrode assembly in between; and a separator plate positioned on each of the opposite sides of the faces of the pair of gas diffusion layers, wherein at least one of the pair of gas diffusion layers is a hydrophobic coated metal gas diffusion layer, and the separator plate adjacent to the hydrophobic coated metal gas diffusion layer is in the form of a frame.

[0022] In a polymer electrolyte membrane fuel cell according to one embodiment of the present invention, the hydrophobic coated metal gas diffusion layer can prevent corrosion even during long-term operation and can prevent structural deformation of the gas diffusion layer and loss of constituent materials. Furthermore, the hydrophobic coated metal gas diffusion layer can control the thickness of the gas diffusion layer by adjusting the thicknesses of the first metal plate, the second metal plate, and the third metal plate, while simultaneously changing the size of the micropores, thereby allowing water generated by the electrochemical reaction to be discharged with an optimized capillary pressure gradient. Additionally, the gas diffusion layer can be uniformly implemented, thereby preventing problems caused by local differences in the content of constituent materials such as carbon black, other resins, fillers, carbon fibers, or Teflon.

[0023] According to one embodiment of the present invention, a separator plate positioned adjacent to the hydrophobic coated metal gas diffusion layer may have a flat plate structure with through holes, and the through holes may not be flow channels but simply serve as passages for gas and water to pass through. Specifically, the frame-shaped separator plate may have only through holes without flow channels that induce the flow of reaction gas. In conventional separator plates with flow channels, reaction gas (oxygen) is not well supplied to the rib portion, but since the frame-shaped separator plate has through holes larger than flow channels, reaction gas (oxygen) can be supplied more uniformly to the entire active surface area. Accordingly, a polymer electrolyte membrane fuel cell including the frame-shaped separator plate can improve water discharge capacity and reaction gas (oxygen) supply efficiency, thereby improving the performance of the fuel cell.

[0024] According to one embodiment of the present invention, the hydrophobic coated metal gas diffusion layer comprises: a first metal plate having a plurality of first micropores having a first average size; a second metal plate having a plurality of second micropores having a second average size; and a third metal plate having a plurality of third micropores having a third average size; wherein the first to third average sizes may satisfy the following Equation 1:

[0025] [Mathematical Formula 1]

[0026] 1st average size > 2nd average size > 3rd average size.

[0027] As shown in Equation 1 above, if the micropores become smaller in the order of the first micropore, the second micropore, and the third micropore, the capillary pressure gradient of the hydrophobic coated metal gas diffusion layer can be maximized.

[0028] According to one embodiment of the present invention, the first average size, the second average size, and the third average size can be adjusted, and an improved capillary pressure can be derived through the following mathematical formula 2.

[0029] [Mathematical Formula 2]

[0030]

[0031] In the above mathematical formula 2, P c ε is capillary pressure, τ is surface tension, θ c θ is the contact angle, ε is the porosity, J(s) is the Leverett J function, s is the liquid water saturation, and d p represents the pore size. Through the above mathematical formula 2, the average size of the first micropore, second micropore, and third micropore, which improves capillary pressure, can be derived to improve the moisture removal efficiency of the gas diffusion layer.

[0032] Furthermore, due to the improvement in the capillary pressure, moisture generated in the fuel cell can easily escape to the outside (end plate), and as a result, a flow of the reaction gas (oxygen) of the fuel cell is induced toward the inside (membrane electrode assembly). Therefore, by using the hydrophobic coated metal gas diffusion layer, a frame-shaped separator without a separate flow channel can be used, and as mentioned above, the oxygen supply efficiency can be improved, thereby improving the performance of the fuel cell.

[0033] According to one embodiment of the present invention, the first metal plate, the second metal plate, and the third metal plate may be sequentially stacked. Specifically, the first metal plate, the second metal plate, and the third metal plate may be sequentially stacked such that the average size of the micropores becomes progressively smaller. Additionally, in a polymer electrolyte membrane fuel cell, the hydrophobic coated metal gas diffusion layer may be arranged such that the third metal plate, which has the smallest micropore size, faces the membrane electrode assembly. As described above, by stacking and arranging the first metal plate, the second metal plate, and the third metal plate, the capillary pressure gradient of the hydrophobic coated metal gas diffusion layer can be improved, thereby improving the discharge efficiency of water formed by the reduction reaction of oxygen. In addition, it can replace the microporous layer (MPL), microporous layer penetration layer (a layer in which components of the substrate surface penetrate into the microporous layer when the microporous layer and the substrate surface are pressed together under pressure), and the substrate included in the conventional carbon-based gas diffusion layer (GDL).

[0034] According to one embodiment of the present invention, the first micropore may be formed by penetrating the first metal plate in the thickness direction, length direction, and width direction, respectively; the second micropore may be formed by penetrating the second metal plate in the thickness direction, length direction, and width direction, respectively; and the third micropore may be formed by penetrating the third metal plate in the thickness direction, length direction, and width direction, respectively. As described above, by forming the first micropore, the second micropore, and the third micropore by penetrating the first metal plate in the thickness direction, length direction, and width direction, respectively, the permeability of a gas such as a reaction gas can be maximized, and the removal efficiency can be improved by increasing the contact area between the water formed by the reduction reaction of oxygen and the metal plate.

[0035] According to one embodiment of the present invention, the micropores in the metal plate may be formed by irradiating a laser to penetrate the metal plate in the thickness direction, length direction, and width direction, respectively. By forming the micropores in the metal plate using the method described above, the size of the micropores can be uniformly realized, and the micropores can be uniformly sprayed and formed in the metal plate.

[0036] According to one embodiment of the present invention, the first metal plate, the second metal plate, and the third metal plate may each be an alloy comprising one or more selected from titanium, iron, copper, aluminum, chromium, nickel, and molybdenum. Specifically, the first metal plate, the second metal plate, and the third metal plate may be a copper, titanium, or 316L stainless steel alloy. When the first metal plate, the second metal plate, and the third metal plate are the aforementioned alloys, the durability of the hydrophobic coated metal gas diffusion layer can be improved, the shape can be prevented from being deformed by external pressure during the stack formation process due to the compressive strength of the metal plates, and the loss of components can be minimized by not using carbon components.

[0037] According to one embodiment of the present invention, the first metal plate, the second metal plate, and the third metal plate each have an electrical conductivity of 1×10 -6 Ω·cm or more 100×10⁻⁶ -6 It may be Ω·cm or less. When the first metal plate, the second metal plate, and the third metal plate are within the aforementioned electrical conductivity range, the power generation efficiency of the fuel cell using the gas diffusion layer can be improved.

[0038] According to one embodiment of the present invention, the third average size of the third micropore is 1×10 -3 It may be between µm and 20 µm. Specifically, the third average size of the third micropore is 1×10 -3It may be µm or more and 20 µm or less, 0.001 µm or more and 15 µm or less, 0.001 µm or more and 10 µm or less, or 0.002 µm or more and 5 µm or less. When the third average size of the third micropore is within the aforementioned range, the capillary pressure gradient of the hydrophobic coated metal gas diffusion layer can be improved.

[0039] According to one embodiment of the present invention, the second average size of the second micropore is 2 times or more and 24 times or less the third average size of the third micropore, and the first average size of the first micropore may be 50 times or more and 1,000 times or less the third average size of the third micropore. Specifically, the second average size of the second micropore may be 4 times or more and 23 times or less, 6 times or more and 22 times or less, 8 times or more and 21 times or less, 9 times or more and 20 times or less, 10 times or more and 19 times or less, or 19 times or more and 23 times or less the third average size of the third micropore. In addition, the first average size of the first micropore may be 55 times or more and 900 times or less, 60 times or more and 800 times or less, 65 times or more and 700 times or less, 70 times or more and 600 times or less, 75 times or more and 500 times or less, 100 times or more and 400 times or less, 120 times or more and 300 times or less, or 55 times or more and 65 times or less than the third average size of the third micropore. When the second average size of the second micropore and the first average size of the first micropore are within the aforementioned ranges, the capillary pressure gradient of the hydrophobic coated metal gas diffusion layer can be improved.

[0040] According to one embodiment of the present invention, the first average size of the first micropore : the second average size of the second micropore : the third average size of the third micropore is preferably 1 : 15 to 25 : 60 to 100. When the first average size of the first micropore : the second average size of the second micropore : the third average size of the third micropore is within the aforementioned range, the capillary pressure gradient of the hydrophobic coated metal gas diffusion layer can be improved, and water generated in the reduction reaction of the fuel cell can be easily removed.

[0041] According to one embodiment of the present invention, the thickness of the second metal plate may be 20% or more and 99% or less with respect to the thickness of the first metal plate, and the thickness of the third metal plate may be 1% or more and 50% or less with respect to the thickness of the first metal plate. Specifically, the thickness of the second metal plate may be 20% or more and 99% or less, 22% or more and 98% or less, 24% or more and 97% or less, 26% or more and 96% or less, 28% or more and 95% or less, 30% or more and 90% or less, 32% or more and 80% or less, 34% or more and 70% or less, or 90% or more and 99% or less with respect to the thickness of the first metal plate. In addition, the thickness of the third metal plate may be 1% or more and 50% or less, 2% or more and 48% or less, 3% or more and 46% or less, 4% or more and 4% or less, 5% or more and 42% or less, 6% or more and 40% or less, 7% or more and 15% or less, 9% or more and 13% or less, or 6% or more and 10% or less with respect to the thickness of the first metal plate. When the thicknesses of the second metal plate and the third metal plate are within the aforementioned ranges, the durability of the hydrophobic coated metal gas diffusion layer can be improved, and the thickness of the hydrophobic coated metal gas diffusion layer can be reduced, thereby enabling the miniaturization of the fuel cell.

[0042] According to one embodiment of the present invention, the thickness of the hydrophobic coated metal gas diffusion layer may be 100 μm or more and 600 μm or less. Specifically, the thickness of the hydrophobic coated metal gas diffusion layer may be 100 μm or more and 600 μm or less, 110 μm or more and 590 μm or less, 120 μm or more and 570 μm or less, 130 μm or more and 560 μm or less, 140 μm or more and 550 μm or less, 150 μm or more and 540 μm or less, 160 μm or more and 500 μm or less, 170 μm or more and 400 μm or less, 180 μm or more and 300 μm or less, 190 μm or more and 260 μm or less, or 550 μm or more and 600 μm or less. When the thickness of the above-mentioned hydrophobic coated metal gas diffusion layer is within the aforementioned range, the capillary pressure gradient can be improved and the desired capillary pressure gradient can be controlled.

[0043] According to one embodiment of the present invention, the compression ratio of the hydrophobic coated metal gas diffusion layer may be 20% or more and 50% or less. Throughout this specification, the “compression ratio” may refer to the ratio of the thickness of the compressed hydrophobic coated metal gas diffusion layer to the thickness before compression is applied after the hydrophobic coated metal gas diffusion layer is laminated. That is, it may refer to the ratio of the thickness of the compressed hydrophobic coated metal gas diffusion layer to the thickness before pressure is applied, after the hydrophobic coated metal gas diffusion layer is laminated and compressed at a pressure of 1 MPa, and may refer to a ratio adjusted by varying the thickness of the gasket. Specifically, the compressibility of the hydrophobic coated metal gas diffusion layer may be 22% or more and 48% or less, 24% or more and 46% or less, 26% or more and 44% or less, 28% or more and 42% or less, 30% or more and 40% or less, 32% or more and 38% or less, 34% or more and 36% or less, or 38%. When the compressibility of the hydrophobic coated metal gas diffusion layer is within the aforementioned range, the current density can be improved and the power generation efficiency of the fuel cell can be improved.

[0044] According to one embodiment of the present invention, the hydrophobic coated metal gas diffusion layer may be coated with an aqueous solution of a fluorinated resin on at least one surface or part of the surface of at least one of the first metal plate, the second metal plate, and the third metal plate. As described above, the hydrophobic coated metal gas diffusion layer may have its water discharge capacity and the performance of the fuel cell improved by coating at least one surface or part of the surface of at least one of the first metal plate, the second metal plate, and the third metal plate with a fluorinated resin.

[0045] According to one embodiment of the present invention, the concentration of the aqueous fluorinated resin solution may be greater than 0 wt% and less than or equal to 5 wt%. Specifically, the concentration of the aqueous fluorinated resin solution may be greater than 0 wt% and less than or equal to 5 wt%, greater than or equal to 0.5 wt% and less than or equal to 4.5 wt%, greater than or equal to 1.0 wt% and less than or equal to 4.0 wt%, or greater than or equal to 1.0 wt% and less than or equal to 3.5 wt%. When the aqueous fluorinated resin solution is hydrophobically coated at a concentration within the aforementioned range, it is possible to prevent the micropores contained in the first metal plate, the second metal plate, and the third metal plate from being clogged by the fluorinated resin, and to improve the current density of the hydrophobically coated metal gas diffusion layer.

[0046] According to one embodiment of the present invention, the fluorinated resin is polytet

[0047] It may be one or more selected from tetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, and polyfluorovinylidene (PVDF).

[0048] According to one embodiment of the present invention, the third metal plate of the hydrophobically coated metal gas diffusion layer may be further coated with a microporous layer having a fourth average size. Specifically, the microporous layer having a fourth average size may be formed by coating the microporous layer once more on the surface of the third metal plate of the hydrophobically coated metal gas diffusion layer to form a coating layer containing micropores.

[0049] According to one embodiment of the present invention, the fourth average size may be smaller than the third average size. Specifically, a metal gas diffusion layer that is hydrophobically coated and has a microporous layer formed thereon may be stacked in an order in which the average size of the micropores decreases in order. Since the fourth average size is smaller than the third average size, the metal gas diffusion layer that is hydrophobically coated and has a microporous layer having the fourth average size can maximize the capillary pressure gradient.

[0050] According to one embodiment of the present invention, the microporous layer having a fourth average size may be composed of one or more materials selected from carbon black, graphite, silver, and stainless steel. The third metal plate of the hydrophobically coated metal gas diffusion layer has micropores of a fourth average size smaller than the third micropores of the third metal plate, and the water discharge capability can be improved by forming a microporous layer of a carbon material (carbon black) having hydrophobic properties. In addition, it can be positioned between the gas diffusion layer and the catalyst layer included in the membrane electrode assembly to reduce interfacial resistance and improve the performance of the fuel cell.

[0051] According to one embodiment of the present invention, the membrane electrode assembly (MEA) may comprise an electrolyte membrane, a catalyst layer of an anode electrode, and a catalyst layer of a cathode electrode. Specifically, the catalyst layer of the anode electrode and the catalyst layer of the cathode electrode may be arranged to face each other with the electrolyte membrane in between.

[0052] According to one embodiment of the present invention, the electrolyte membrane may comprise one or more polymers selected from perfluorosulfonic acid polymers, hydrocarbon polymers, polyimide, polyvinylidene fluoride, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, polyesters, doped polybenzimidazoles, polyetherketones, polysulfones, and their acids and bases. When the electrolyte membrane comprises the aforementioned polymers, the mobility of hydrogen ions generated in the fuel cell within the electrolyte can be improved.

[0053] According to one embodiment of the present invention, the catalyst layer of the anode electrode comprises one or more catalysts selected from platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, and platinum-transition metal alloy, and the catalyst layer of the cathode electrode may comprise platinum as a catalyst. When the catalyst layer of the anode electrode comprises the aforementioned catalyst, the efficiency of the oxidation reaction occurring at the anode electrode can be improved. Additionally, when the catalyst layer of the cathode electrode comprises the aforementioned platinum as a catalyst, the efficiency of the reduction reaction occurring at the cathode electrode can be improved.

[0054] According to one embodiment of the present invention, the catalyst may be supported on a carbon-based carrier. Specifically, the catalysts of the catalyst layer of the anode electrode and the catalyst layer of the cathode electrode may each be supported on a carbon-based carrier, thereby maximizing the efficiency of the oxidation reaction occurring at the anode electrode and the reduction reaction occurring at the cathode electrode.

[0055] The process of introducing the catalyst layer described above can be performed using conventional methods known in the art. Specifically, the catalyst layer can be introduced by directly coating a catalyst ink onto a polymer electrolyte membrane. At this time, the coating method of the catalyst ink is not particularly limited, but spray coating, tape casting, screen printing, blade coating, die coating, or spin coating methods may be used. The catalyst ink may consist of a catalyst, a polymer ionomer, and a solvent.

[0056] The above-mentioned polymer ionomer can serve as a channel for ions generated by the reaction between a fuel, such as hydrogen or methanol, and a catalyst to move to the electrolyte membrane. Specifically, examples include sulfonated polymers such as Nafion ionomer and sulfonated polytrifluorostyrene, but are not limited thereto.

[0057] In addition, examples of usable solvents include water, butanol, isopropanol, methanol, ethanol, n-propanol, n-butyl acetate, ethylene glycol, etc., and these solvents can be used alone or in a mixture of two or more. It is preferable to use the same solvent for the anode and the cathode.

[0058] According to one embodiment of the present invention, the polymer electrolyte membrane fuel cell may include a fuel supply unit for supplying fuel. The fuel supply unit serves to supply fuel to the polymer electrolyte membrane fuel cell and may be composed of a fuel tank for storing fuel and a pump for supplying the fuel stored in the fuel tank to the polymer electrolyte membrane fuel cell. The fuel may be hydrogen or hydrocarbon fuel in a gaseous or liquid state, and examples of hydrocarbon fuels include methanol, ethanol, propanol, butanol, or natural gas.

[0059] According to one embodiment of the present invention, the polymer electrolyte membrane fuel cell comprises an oxidant supply unit that supplies an oxidant. The oxidant supply unit serves to supply an oxidant to the polymer electrolyte membrane fuel cell. Oxygen is typically used as the oxidant, and oxygen or air can be injected using a pump.

[0060] Hereinafter, the present invention will be described in detail through examples and experimental examples to specifically explain the invention. However, the examples and experimental examples according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the examples and experimental examples described below. The examples and experimental examples of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0061] Preparation Example 1. Preparation of a metallic gas diffusion layer

[0062] A metal gas diffusion layer was manufactured by sequentially stacking a first metal plate, a second metal plate with a mesh of 50 mesh, and a third metal plate with a mesh of 975 mesh, which are metal foams as shown in Table 1 below.

[0063] Types of metal plates Pore ​​size (㎛) Thickness of the metal plate First metal plate Metal form Long Scale: 800 / Short Scale: 200 290 2nd metal plate 50 mesh 300 280 Third metal plate 975 mesh 13 25

[0064] Preparation Example 2. Preparation of a hydrophobic coated metal gas diffusion layer

[0065] A metal gas diffusion layer prepared in the above Preparation Example 1 was hydrophobically treated with a 2 wt% concentration aqueous solution of poly(tetrafluoroethylene, PTFE), and then dried in a constant temperature and humidity chamber (NEX1200) at 100°C for 1 hour to produce a metal gas diffusion layer in which a hydrophobic coating layer is formed on the surfaces of the first metal plate, the second metal plate, and the third metal plate included in the metal gas diffusion layer.

[0066] Experimental Example 1. Polytetrafluoroethylene Measurement of current density of a hydrophobic-coated metal gas diffusion layer according to aqueous solution concentration

[0067] A hydrophobic coated metal gas diffusion layer was prepared in the same manner as in Preparation Example 2, except that the concentration of the polytetrafluoroethylene aqueous solution was varied. Then, the current density of each prepared hydrophobic coated metal gas diffusion layer was measured using a loader (PLZ64WA, Kikusui Electronic, Corp.) under conditions of 65 ℃, atmospheric pressure, 100% relative humidity, and 0.2 V constant voltage, and the results are shown in Fig. 6.

[0068] As shown in Figure 6, it was confirmed that the current density of the hydrophobically coated metal gas diffusion layer is excellent when the concentration of the polytetrafluoroethylene aqueous solution is greater than 0 wt% and less than or equal to 5 wt%, and in particular, the current density is best when the concentration of the polytetrafluoroethylene aqueous solution is 2 wt%.

[0069] Preparation Example 3. Preparation of a metal gas diffusion layer with a hydrophobic coating and a microporous layer formed therein

[0070] A metal gas diffusion layer with a microporous layer formed on the surface of the third metal plate of the hydrophobic coated metal gas diffusion layer of Manufacturing Example 2 was prepared by coating the hydrophobic coated metal gas diffusion layer of Manufacturing Example 2 with a microporous layer made of carbon black material.

[0071] Comparative Example 1. Polymer electrolyte membrane fuel cell using a conventional carbon-based gas diffusion layer and a separator with flow channels

[0072] Figure 1 shows a polymer electrolyte membrane fuel cell using a conventional carbon-based gas diffusion layer (GDL) and a bipolar plate having a flow channel.

[0073] Specifically, FIG. 1 shows a conventional carbon-based gas diffusion layer in which a microporous layer (MPL), a substrate, a gasket, a bipolar plate having a flow channel, a current collector, and an end plate are disposed on both sides of a membrane electrode assembly (MEA). Additionally, the end plate may include a supply section and an outlet indicated in a cylindrical shape.

[0074] Accordingly, a conventional polymer electrolyte membrane fuel cell as shown in Fig. 1 was manufactured using a microporous layer (MPL), a carbon material gas diffusion layer (Avcarb, GDS2300) as the substrate surface, and a separator having a flow channel.

[0075] Comparative Example 2. Polymer electrolyte membrane fuel cell using a separator plate having a metal gas diffusion layer and a flow channel

[0076] A polymer electrolyte membrane fuel cell was manufactured using a metal gas diffusion layer and a separator with a flow channel in the same manner as Comparative Example 1, except that the metal gas diffusion layer of Manufacturing Example 1 was used instead of a carbon material gas diffusion layer.

[0077] Comparative Example 3. Polymer electrolyte membrane fuel cell using a separator plate having a hydrophobic coated metal gas diffusion layer and a flow channel

[0078] FIG. 2 shows a polymer electrolyte membrane fuel cell using a separator with a hydrophobic coated metal gas diffusion layer and a flow channel (hydrophobic coating layer not shown).

[0079] A polymer electrolyte membrane fuel cell was manufactured using a hydrophobic coated metal gas diffusion layer and a separator with a flow channel in the same manner as Comparative Example 1, except that the hydrophobic coated metal gas diffusion layer of Manufacturing Example 2 was used instead of a carbon material gas diffusion layer.

[0080] Example 1. Polymer electrolyte membrane fuel cell using a hydrophobic coated metal gas diffusion layer and a separator without flow channels

[0081] FIG. 3 shows a polymer electrolyte membrane fuel cell using a hydrophobic coated metal gas diffusion layer and a separator without flow channels (hydrophobic coating layer not shown).

[0082] In addition, FIG. 5 shows a separator plate with a Euro channel and a separator plate without a Euro channel according to the present invention. Specifically, the separator plate with a Euro channel is a separator plate in which a Euro channel with a repeating “L”-shaped pattern is formed, and the separator plate without a Euro channel has an opening formed instead of a Euro channel.

[0083] A polymer electrolyte membrane fuel cell was manufactured using a hydrophobic coated metal gas diffusion layer and a separator without a Eurochannel in the same manner as Comparative Example 3, except that a separator without a Eurochannel was used instead of a separator with a Eurochannel.

[0084] Example 2. Polymer electrolyte membrane fuel cell using a metal gas diffusion layer with a hydrophobic coating and a microporous layer and a separator without flow channels

[0085] Figure 4 shows a polymer electrolyte membrane fuel cell using a metal gas diffusion layer with a hydrophobic coating and a microporous layer formed therein, and a separator without a flow channel.

[0086] A polymer electrolyte membrane fuel cell was manufactured using a hydrophobic coated metal gas diffusion layer and a separator without flow channels, in the same manner as in Example 1, except that the hydrophobic coated metal gas diffusion layer of Manufacturing Example 3 was used instead of the hydrophobic coated metal gas diffusion layer.

[0087] Experimental Example 2. Measurement of Polarization Curve

[0088] The operating voltage according to current density was measured for the polymer electrolyte membrane fuel cells prepared in the above Examples 1, 2, Comparative Examples 1, 2, and 3, respectively, using a loader (PLZ64WA, Kikusui Electronic, Corp.) under conditions of 65 ℃, atmospheric pressure, and relative humidity (30% or 100%), and The results are shown as polarization curves in Figs. 7a, 7b, 8a, 8b, 9a, and 9b.

[0089] Looking at Figures 7a, 8a, and 9a, it was confirmed that the polymer electrolyte membrane fuel cells of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 exhibit similar polarization curves under conditions of 30% relative humidity.

[0090] On the other hand, referring to FIGS. 7b, 8b, and 9b, under 100% relative humidity conditions, the polymer electrolyte membrane fuel cells of Examples 1 and 2 exhibited 1.0 A / cm² higher than the polymer electrolyte membrane fuel cells of Comparative Examples 1, 2, and 3 due to their excellent water discharge capacity and excellent oxygen supply. 2 It can be seen that the voltage is improved above the current density.

[0091] Experimental Example 3. Measurement of Electrochemical Impedance

[0092] The electrochemical impedance of the polymer electrolyte membrane fuel cells prepared in Examples 1 and 2, and Comparative Examples 1, 2, and 3 above was measured using a KRM 2150 and PLZ-4W fuel cell impedance meter (Kikusui Elextronics Co.) at 65 °C, atmospheric pressure, and 30 % relative humidity as 1.0 A / cm² 2 Or 2.0 A / cm at 100% relative humidity 2 Measurements were taken under certain conditions, and the results are shown in Figs. 10a, 10b, 11a, 11b, 12a, and 12b.

[0093] Referring to Figs. 10a, 11a, and 12a, the relative humidity is 30% and 1.0 A / cm² 2 Under the conditions, the polymer electrolyte membrane fuel cells of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 exhibited similar polarization curves, confirming that their resistances were similar.

[0094] Referring to Figs. 10b, 11b, and 12b, relative humidity 100% and 2.0 A / cm 2 Under the conditions, the polymer electrolyte membrane fuel cells of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 have similar high-frequency resistance, but the low-frequency resistance of the polymer electrolyte membrane fuel cells of Example 1 and Example 2 is significantly lower, so it can be seen that the power density of the fuel cell is improved.

[0095] Although the present invention has been described above by limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

Claim 1 A polymer electrolyte membrane fuel cell comprising: a membrane electrode assembly (MEA); a pair of gas diffusion layers positioned opposite each other with the membrane electrode assembly in between; and a separator plate positioned on each of the opposite sides of the faces of the pair of gas diffusion layers, wherein at least one of the pair of gas diffusion layers is a hydrophobic coated metal gas diffusion layer, and the separator plate adjacent to the hydrophobic coated metal gas diffusion layer is in the form of a frame without a flow channel. Claim 2 In claim 1, the hydrophobic coated metal gas diffusion layer comprises: a first metal plate having a plurality of first micropores having a first average size; a second metal plate having a plurality of second micropores having a second average size; and a third metal plate having a plurality of third micropores having a third average size; wherein the first to third average sizes satisfy the following Equation 1: [Equation 1] First average size > Second average size > Third average size. Claim 3 A polymer electrolyte membrane fuel cell according to paragraph 2, wherein the first metal plate, the second metal plate, and the third metal plate are each alloys comprising one or more selected from titanium, iron, copper, aluminum, chromium, nickel, and molybdenum. Claim 4 A polymer electrolyte membrane fuel cell according to paragraph 2, wherein the hydrophobic coated metal gas diffusion layer has at least one surface of the first metal plate, the second metal plate, and the third metal plate coated with an aqueous solution of a fluorinated resin. Claim 5 A polymer electrolyte membrane fuel cell according to claim 4, wherein the concentration of the aqueous fluorinated resin solution is greater than 0 wt% and less than or equal to 5 wt%. Claim 6 A polymer electrolyte membrane fuel cell according to claim 4, wherein the fluorinated resin is one or more selected from polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, and polyfluorovinylidene (PVDF). Claim 7 A polymer electrolyte membrane fuel cell according to claim 1, wherein the thickness of the hydrophobic coated metal gas diffusion layer is 100 μm or more and 600 μm or less. Claim 8 A polymer electrolyte membrane fuel cell according to paragraph 2, wherein the third metal plate of the hydrophobic coated metal gas diffusion layer is further coated with a micropore layer having a fourth average size. Claim 9 A polymer electrolyte membrane fuel cell according to claim 8, wherein the fourth average size is smaller than the third average size. Claim 10 A polymer electrolyte membrane fuel cell according to claim 8, wherein the microporous layer having the fourth average size is composed of one or more selected from carbon black, graphite, silver, and stainless steel. Claim 11 A polymer electrolyte membrane fuel cell according to claim 1, wherein the membrane electrode assembly (MEA) comprises an electrolyte membrane, a catalyst layer of an anode electrode, and a catalyst layer of a cathode electrode, and the electrolyte membrane comprises one or more polymers selected from perfluorosulfonic acid polymer, hydrocarbon polymer, polyimide, polyvinylidene fluoride, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, polyester, doped polybenzimidazole, polyetherketone, polysulfone, and acids and bases thereof. Claim 12 A polymer electrolyte membrane fuel cell according to claim 11, wherein the catalyst layer of the anode electrode comprises one or more catalysts selected from platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, and platinum-transition metal alloy, and the catalyst layer of the cathode electrode comprises platinum.

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