Method for producing polymer electrolyte membrane

Abstract

The present invention relates to a method for producing a polymer electrolyte membrane using digital printing, specifically, a method for producing a polymer electrolyte membrane, including the steps of preparing a printing composition containing a functional additive, and printing the printing composition onto one or both sides of a polymer electrolyte membrane using a digital printing device to form a digitally printed membrane.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polymer electrolyte membrane, and in particular to a method for producing a polymer electrolyte membrane using digital printing techniques. [Background technology]

[0002] Fuel cells are cells that directly convert chemical energy generated by the oxidation of fuel into electrical energy, and are attracting attention as a next-generation energy source due to their high energy efficiency and environmentally friendly characteristics with low pollutant emissions.

[0003] A fuel cell generally has a structure in which an anode and a cathode are formed on either side of an electrolyte membrane, and this structure is called a membrane electrode assembly (MEA).

[0004] Among fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) have been attracting attention as portable, vehicular, and home power sources due to their advantages such as a low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability. A representative example of such polymer electrolyte fuel cells is the proton exchange membrane fuel cell (PEMFC), which uses hydrogen gas as fuel.

[0005] 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 - ) is produced. The hydrogen ions (H + ) is transferred to the reduction electrode through the polymer electrolyte membrane, and the generated electrons (e - ) is transferred to the reducing electrode via an external circuit. Oxygen is supplied to the reducing electrode, and the oxygen is converted into hydrogen ions (H +) and electrons (e - ) and produces water by oxygen reduction reaction.

[0006] However, there are still many technical hurdles to overcome before polymer electrolyte fuel cells can be commercialized, and essential improvements include achieving high performance, long life, and low cost. The component that has the greatest impact on this is the membrane-electrode assembly, and the polymer electrolyte membrane is one of the key elements that has the greatest impact on the performance and cost of the MEA.

[0007] Polymer electrolyte membranes require both high ionic conductivity and excellent durability. In particular, during long-term operation of fuel cells, the poor chemical durability of the polymer electrolyte membrane leads to deterioration of the fuel cell due to a decrease in the electrolyte membrane thickness and the formation of pinholes.

[0008] Radicals generated during fuel cell operation are known to be a major cause of degradation of the polymer electrolyte membrane. For example, hydrogen peroxide (H2O2) is generated during the oxygen reduction reaction at the anode due to an unwanted reaction. This hydrogen peroxide can then generate hydrogen peroxide radicals (HO2·) and / or hydroxyl radicals (·OH). Furthermore, when oxygen molecules in the air supplied to the anode pass through the polymer electrolyte membrane and reach the cathode, hydrogen peroxide can also be generated at the cathode, potentially generating hydrogen peroxide radicals and / or hydroxyl radicals. These radicals can cause degradation of the ionomer (e.g., a polymer containing sulfonic acid groups) contained in the polymer electrolyte membrane, reducing the ionic conductivity of the electrolyte membrane.

[0009] To mitigate chemical degradation of electrolyte membranes, various antioxidants have been added to the electrolyte membrane. These antioxidants include primary antioxidants, which function as radical scavengers, and secondary antioxidants, which function as hydrogen peroxide decomposers. These antioxidants can be used alone or in combination.

[0010] However, these antioxidants typically have low proton conductivity, and when mixed with a polymer electrolyte solution and cast together to produce a membrane, they can inhibit the movement of protons due to particle aggregation, resulting in a decrease in the ion conductivity of the polymer electrolyte membrane.Furthermore, while the antioxidant reaction is preferably carried out in the catalyst layer, where radicals are generated, existing methods have made it difficult to increase the antioxidant content in areas adjacent to the catalyst layer, or to form the antioxidant area into a fine pattern or apply it uniformly as needed. Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a method for producing a polymer electrolyte membrane, which can form a layer of a functional additive such as an antioxidant on the surface of a polymer electrolyte membrane adjacent to an electrode catalyst layer, and which can easily form a fine pattern on the functional additive layer and adjust the application amount, as needed. [Means for solving the problem]

[0012] The inventors have been able to achieve the above objectives by utilizing digital printing techniques, resulting in the present invention.

[0013] Thus, according to one aspect of the present invention, there is provided a method for manufacturing a polymer electrolyte membrane, comprising the steps of: preparing a printing composition containing a functional additive; and printing the printing composition onto one or both sides of a polymer electrolyte membrane using a digital printing device to form a digitally printed membrane.

[0014] According to one embodiment, the functional additive may be an antioxidant that scavenges peroxides or radicals.

[0015] According to one embodiment, the antioxidant may be at least one selected from the group consisting of transition metals, noble metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof.

[0016] According to one embodiment, the antioxidant may include one or more transition metals selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd).

[0017] According to one embodiment, the functional additive may be contained in the printing composition at a concentration of 0.1 to 20 wt % based on the total weight of the composition.

[0018] According to one embodiment, the printing composition further comprises a solvent, and the method can further comprise a step of drying after the formation of the digitally printed film.

[0019] According to one embodiment, the solvent may be a mixed solvent containing two or more alcohols.

[0020] According to one embodiment, the solvent may be a mixed solvent in which propyl alcohol and ethanol are mixed in a weight ratio of 6:4 to 2:8.

[0021] According to one embodiment, the digital printing device includes a printer selected from the group consisting of an inkjet printer, a laser printer, an aerosol printer, and a thermal transfer or dye-sublimation printer, and the printing composition can be printed by the printer.

[0022] According to one embodiment, the manufacturing method further includes the steps of designing a pattern image of the digitally printed membrane using computer software and transmitting the pattern image to a printer, and the printing composition can be printed on the polymer electrolyte membrane in a pattern corresponding to the pattern image.

[0023] According to one embodiment, the step of designing the pattern image of the digital print film further includes a step of setting a resolution of the pattern image, and the printing amount of the printing composition may be determined according to the resolution.

[0024] According to one embodiment, the polymer electrolyte membrane may be a reinforced composite membrane including a porous support and an ion conductor.

[0025] According to another aspect, there is provided a method for producing a membrane-electrode assembly, comprising the step of contacting a polymer electrolyte membrane produced by the above-described method with an electrode such that a digitally printed version of the polymer electrolyte membrane faces the electrode. [Effects of the Invention]

[0026] According to the present invention, instead of manufacturing a polymer electrolyte membrane by mixing a functional additive such as an antioxidant with an ion conductor, the functional additive can be directly formed on the surface of the polymer electrolyte membrane as a digitally printed film, thereby achieving excellent functionality with a smaller amount of functional additive than conventional methods. Therefore, the performance of the fuel cell can be maintained for a long period of time without chemical degradation of the electrolyte membrane and / or electrodes due to hydrogen peroxide and radicals generated during fuel cell operation, and the durability of the fuel cell can be significantly improved.

[0027] Furthermore, according to the present invention, the digitally printed film can be formed over the entire surface of a polymer electrolyte membrane, and by using a digital image, the functional additive film can be easily and quickly finely patterned into various fine shapes, such as channels or dots, as needed, allowing for precise structural control with excellent quality. Furthermore, since the amount of coating of the digitally printed film can be controlled according to the image resolution, the additive content can be easily and accurately controlled. Furthermore, polymer electrolyte membranes with different additive contents can be easily produced by using the same polymer electrolyte membrane and printing composition and adjusting only the image resolution, without having to prepare a new polymer electrolyte membrane each time depending on the required additive content. [Brief explanation of the drawings]

[0028] [Figure 1] 1A to 1C are schematic diagrams illustrating polymer electrolyte membranes in the form of reinforced composite membranes, where (a) to (c) are schematic diagrams of polymer electrolyte membranes according to the prior art, and (d) and (e) are schematic diagrams of polymer electrolyte membranes according to one embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating a membrane-electrode assembly according to one embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing the overall configuration of a fuel cell according to one embodiment of the present invention; [Figure 4] 1A and 1B are diagrams illustrating exemplary print patterns of a digitally printed film according to the present invention. [Figure 5]1 is a photograph showing a digital print film produced according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Although the present invention may be embodied in many different forms, it is not intended to be limited to the embodiments set forth herein, and the present invention is not limited to the embodiments set forth herein.

[0030] In the drawings, thicknesses of multiple layers and regions are exaggerated for clarity. Similar parts are designated by the same reference numerals throughout the specification. When a part, such as a layer, film, region, or plate, is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part between them. Conversely, when a part is said to be "directly on" another part, it means that there is no other part between them.

[0031] As used herein, the term "comprising" is used to list materials, compositions, devices, and methods useful in the present invention, but is not limited to the listed examples.

[0032] Hereinafter, a method for producing a polymer electrolyte membrane according to one embodiment will be described with reference to the drawings.

[0033] Like a general polymer electrolyte membrane, the polymer electrolyte membrane of the present invention may be in any form, such as a single membrane formed by casting an ion conductor having ion conductivity in a mold, or a reinforced composite membrane including a composite material prepared by immersing a porous support in a dispersion liquid in which an ion conductor is dispersed.

[0034] FIG. 1 is a schematic diagram illustrating a polymer electrolyte membrane in the form of a reinforced composite membrane, in which (a) to (c) are schematic diagrams of polymer electrolyte membranes according to conventional technology, and (d) and (e) are schematic diagrams of a polymer electrolyte membrane according to one embodiment of the present invention.

[0035] The porous support 5 serves to increase the mechanical strength of the reinforced composite membrane 10 and to increase dimensional stability by suppressing volume expansion due to moisture. A typical porous support used in the field can be used, or the porous support can be produced by chemically strengthening nanofibers of a polymer precursor produced by electrospinning a solution containing a polymer precursor for forming the porous support.

[0036] The porous support 5 preferably contains a polymer that is insoluble in common organic solvents and exhibits excellent chemical resistance, as well as facilitating the process of filling the pores of the porous support with an ionic conductor, and that has excellent heat resistance and is not susceptible to deformation due to moisture in a high-humidity environment. Examples of the polymer include nylon, polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polylactic acid (PLA), polyimide (PI), polybenzoxazole (PBO), polybenzimidazole (PBI), polyamideimide (PAI), polyethylene terephthalate (PET), polyethylene (PC), polytetrafluoroethylene (PTFE), polypropylene (PP), copolymers thereof, and mixtures thereof. Among these, polyimide or polytetrafluoroethylene is preferred because of its excellent heat resistance, chemical resistance, and dimensional stability.

[0037] In one embodiment, the thickness of the porous support 5 is 1 to 100 μm, for example, 1 to 75 μm, preferably 1 to 50 μm, and more preferably 3 to 40 μm. If the thickness of the porous support 5 is less than 1 μm, the physical and mechanical properties of the reinforced composite membrane may not be sufficiently ensured, which may result in reduced durability and dimensional stability. If the thickness exceeds 75 μm, the impregnation efficiency of the ion conductor may be reduced, resulting in a reduced membrane yield. If the thickness exceeds 100 μm, impregnation of the ion-conducting polymer may be difficult, which may result in a reduced hydrogen ion conductivity and reduced membrane performance.

[0038] The porosity of the porous support 5 is 40 to 95%, for example, 50 to 90%, and preferably 55 to 85%. If the porosity of the porous support 5 is less than 40%, the impregnation rate of the ion conductor may decrease, which may result in a decrease in membrane performance, and if it exceeds 95%, the durability of the reinforced composite membrane may not be sufficiently ensured.

[0039] The reinforced composite membrane 10 may be one in which the ionic conductor is impregnated into a porous support 5, or one in which an electrolyte layer 1 and / or 3 containing the ionic conductor is formed on at least one surface of a porous support 5.

[0040] When the ion conductor is impregnated in the porous support 5, the ion conductor is dispersed in a solvent to prepare a mixed solution, and then the porous support 5 is immersed in the mixed solution to form a reinforced composite membrane in which the ion conductor is impregnated in the porous support 5. The solvent may be water, a hydrophilic solvent, an organic solvent, or a mixed solvent of two or more of these.

[0041] In the case of a reinforced composite membrane 10 in which an electrolyte layer 1 and / or 3 containing the ion conductor is formed on at least one surface of a porous support 5, the membrane can be formed by applying a mixed solution of the ion conductor onto at least one surface of the porous support 5 and drying it, or by casting the mixed solution and drying it to form an electrolyte membrane containing the ion conductor, which is then laminated on at least one surface of the porous support 5.

[0042] Alternatively, the reinforced composite membrane 10 may include a form in which the electrolyte layers 1 and / or 3 are formed by laminating an electrolyte membrane containing an ion conductor on at least one surface of the porous support 5 impregnated with the ion conductor.

[0043] Drying can be carried out by applying heat at 60°C to 120°C for about 1 minute to 30 minutes, or preferably by applying heat at 70°C to 100°C for about 5 minutes to 15 minutes.

[0044] In one embodiment, the reinforced composite membrane 10 has a structure in which the ion conductor is continuously distributed from the surface of the porous support 5 in the thickness direction of the reinforced composite membrane 10, by impregnating the porous support 5 with an ion conductor or by providing an electrolyte layer 1 and / or 3 containing an ion conductor on at least one surface of the porous support 5, and thus has continuity of ionic conductivity of the reinforced composite membrane.

[0045] The ion conductor may be any ion conductor that is generally used as a hydrogen ion conductor in an electrolyte membrane of a fuel cell, without any particular limitation. Specifically, a fluorine-based polymer, a hydrocarbon-based polymer, or a mixture thereof that has excellent hydrogen ion conductivity, is advantageous in terms of cost, and is soluble in an organic solvent may be used.

[0046] Specifically, the ion conductor is preferably a polymer having an ion exchange capacity (IEC) of 0.8 meq / g or more. A reinforced composite membrane in which a porous support is impregnated with a polymer having such a high ion exchange capacity can have excellent ionic conductivity, strength, and dimensional stability.

[0047] Specific examples thereof include fluoropolymers including poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfurized polyether ketone, and mixtures thereof, sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, and sulfonated polyketone. polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrileThe polymer may be selected from the group consisting of hydrocarbon polymers including polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, polyarylene ether sulfone ketone, and mixtures thereof, and mixtures thereof.

[0048] The method for producing a polymer electrolyte membrane of the present invention further includes a step of printing a printing composition containing a functional additive onto one or both sides of the polymer electrolyte membrane as described above using a digital printing device.

[0049] The introduction of a functional additive 7', such as an antioxidant, is important for the oxidative durability of a polymer electrolyte membrane. In conventional techniques, the functional additive 7' is mixed with an ionic conductor and uniformly distributed over the entire surface of the polymer electrolyte membrane, as shown in Figure 1(b), or, if necessary, distributed only on one side of the electrolyte membrane 1, as shown in Figure 1(c). However, the antioxidant reaction of the antioxidant 7' begins in the electrode catalyst layer, where radicals are generated, so the functional additive 7' must be distributed on the surface that comes into contact with the electrode catalyst layer. However, conventional coating methods have made it difficult to apply the functional additive 7' thinly and uniformly over the entire surface of the electrolyte membrane or to form a fine pattern.

[0050] In the present invention, the digital printing technology is used to uniformly coat the functional additive on the surface of the polymer electrolyte membrane, thereby enabling the hydrogen peroxide or radical scavenging reaction to occur on the surface of the polymer electrolyte membrane that is in contact with the electrode catalyst layer, and allowing the use of a smaller amount of functional additive than conventional methods.

[0051] Therefore, according to one embodiment of the present invention, there is provided a method for manufacturing a polymer electrolyte membrane, comprising the steps of: preparing a printing composition containing a functional additive; and printing the printing composition onto one or both sides of a polymer electrolyte membrane using a digital printing device to form a digitally printed membrane.

[0052] Here, the polymer electrolyte membrane may be a reinforced composite membrane including a porous support and an ion conductor, as described above, or a single membrane including an ion conductor.

[0053] The functional additive may be any additive added to improve the properties of the polymer electrolyte membrane, such as performance and durability, and may be a single functional additive or a mixture of two or more functional additives. Preferably, the functional additive may be an antioxidant.

[0054] The antioxidant is a particle capable of removing peroxides or radicals that induce deterioration of the electrolyte membrane and reduce its ionic conductivity, and may include at least one selected from the group consisting of transition metals, noble metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof.

[0055] The transition metal may be one or more selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd), but is not limited thereto.

[0056] The noble metal may be one or more selected from the group consisting of silver (Au), platinum (Pt), ruthenium (Ru), palladium (Pd), and rhodium (Rh), but is not limited thereto.

[0057] The transition metal or noble metal ion is a cerium (Ce) ion, a manganese (Mn) ion, a tungsten (W) ion, a cobalt (Co) ion, a vanadium (V) ion, a nickel (Ni) ion, a chromium (Cr) ion, a zirconium (Zr) ion, a yttrium (Y) ion, an iridium (Ir) ion, an iron (Fe) ion, a titanium (Ti) ion, a molybdenum (Mo) ion, a lanthanum (La) ion, or a neodymium (Nd) ion. Specifically, taking cerium as an example, the transition metal or noble metal ion is a cerium trivalent ion (Ce 3+ ) or cerium tetravalent ion (Ce 4+ ) can be.

[0058] The salt of the transition metal or noble metal is a carbonate, acetate, chloride, fluoride, sulfate, phosphate, nitrate, tungstate, hydroxide, ammonium acetate, ammonium sulfate, or acetylacetonate. Specific examples of cerium include cerium carbonate, cerium acetate, cerium chloride, cerium acetate, cerium sulfate, diammonium cerium acetate, and tetraammonium cerium sulfate, and examples of organometallic complex salts include cerium acetylacetonate.

[0059] The printing composition may contain the functional additive at a concentration of 0.1 to 20 wt %, specifically 0.5 to 10 wt %, based on the total weight of the composition. By setting the additive concentration within this range, the functionality of the functional additive can be fully exhibited while preventing problems such as the film taking a long time to dry and the composition being difficult to handle.

[0060] The printing composition may further contain a solvent. Therefore, a drying step may be further included after the subsequent formation of the digitally printed film. The solvent may be an aqueous solvent, such as an alcohol-based solvent such as ethanol, propyl alcohol, or butyl alcohol. The solvent may be a single solvent or a mixed solvent consisting of two or more solvents. According to one embodiment of the present invention, the solvent may be a mixed solvent containing two or more alcohols. The solvent preferably has a low boiling point, such as ethanol, to facilitate evaporation after printing. When using a mixed solvent, it is preferable to use a solvent with a low boiling point in an amount sufficient to facilitate evaporation after printing. For example, a mixed solvent containing propyl alcohol and ethanol in a weight ratio of 6:4 to 2:8 may be used. When a solvent with a high boiling point is used, evaporation and drying are difficult, which may result in unevenness or missing patterns after drying. The drying method is not particularly limited and may be performed by leaving the composition at room temperature or by heating.

[0061] The printing composition can be printed on one or both sides of a polymer electrolyte membrane using a digital printing device to form a digitally printed membrane.

[0062] The printing composition can be printed in any desired pattern to form a patterned digitally printed film. Therefore, according to one embodiment of the present invention, the manufacturing method of the present invention can further include the steps of designing a pattern image of the digitally printed film using computer software and transmitting the pattern image to a printer. Thus, the printing composition can be printed on the polymer electrolyte membrane in a pattern corresponding to the designed pattern image. The pattern is not particularly limited and can be various patterns, such as a channel pattern or a dot pattern, as shown in FIG. 4. In the present invention, by using digital printing, even very fine patterns can be accurately and easily produced.

[0063] Additionally, the step of designing the pattern image of the digitally printed film may further include a step of setting the resolution of the pattern image, and the amount of printing composition to be applied may be determined based on the resolution. For example, the bottom of Figure 4 shows the results of printing digitally printed films of the same area and pattern at different image resolutions of 35 dpi, 70 dpi, and 140 dpi. To observe the film with the naked eye, the same amount of black pigment was added, and it was confirmed that the color gradually became darker with increasing resolution. Therefore, the amount of functional additives can be easily adjusted, for example, by doubling or quadrupling the amount for the same area or pattern, depending on the resolution.

[0064] The digital printing device may be selected from the group consisting of an inkjet printer, a laser printer, an aerosol printer, and a thermal transfer or dye-sublimation printer, and the printing composition may be printed by the printer. For example, an inkjet printer may be used, and the inkjet printer may include a piezoelectric type drop-on-demand inkjet printer using a piezoelectric element, a thermal type drop-on-demand inkjet printer using a microheater, a drop-on-demand inkjet printer that drives an actuator using electrostatic force, and an electrostatic deposition inkjet printer that transfers charged particles dispersed in ink to a substrate or transfers the ink itself to a substrate using electrostatic force.

[0065] According to another aspect of the present invention, there is provided a method for manufacturing a membrane-electrode assembly, comprising the step of contacting a polymer electrolyte membrane manufactured by the manufacturing method according to the present invention with an electrode so that a digitally printed film of the polymer electrolyte membrane faces the electrode. The method for manufacturing the membrane-electrode assembly is not particularly limited and may be performed by a conventional method, except that the digitally printed film of the polymer electrolyte membrane faces the electrode.

[0066] 2 is a cross-sectional view schematically illustrating a membrane-electrode assembly. Referring to FIG. 2, the membrane-electrode assembly 100 includes the reinforced composite membrane 50 and the fuel cell electrodes 20, 20' disposed on both sides of the reinforced composite membrane 50. The electrodes 20, 20' include electrode substrates 40, 40' and catalyst layers 30, 30' formed on the surfaces of the electrode substrates 40, 40'. A microporous layer (not shown) containing conductive fine particles such as carbon powder or carbon black may be further included between the electrode substrates 40, 40' and the catalyst layers 30, 30' to facilitate material diffusion within the electrode substrates 40, 40'.

[0067] FIG. 3 is a schematic diagram showing the overall configuration of a fuel cell.

[0068] 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 reforming unit 220 that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 that generates electrical energy by electrochemically reacting the reformed gas containing hydrogen gas supplied from the reforming unit 220 with an oxidant, and an oxidant supply unit 240 that supplies an oxidant to the reforming unit 220 and the stack 230.

[0069] The stack 230 includes a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between the reformed gas containing hydrogen gas supplied from the reforming unit 220 and the oxidant supplied from the oxidant supplying unit 240.

[0070] Each unit cell refers to a unit cell that generates electricity, and includes the membrane-electrode assembly that oxidizes / reduces oxygen in the reformed gas containing hydrogen gas and the oxidant, and a separator (also called a bipolar plate; hereinafter, referred to as "separator") that supplies the reformed gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separators are placed on both sides of the membrane-electrode assembly, with the membrane-electrode assembly at the center. In this case, the separators located at the outermost sides of the stack are sometimes referred to as end plates.

[0071] The end plate of the separator is provided with a first pipe-shaped supply pipe 231 for injecting the 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 the reformed gas containing hydrogen gas that is ultimately left unreacted in the plurality of unit cells to the outside, and a second exhaust pipe 234 for discharging the oxidant that is ultimately left unreacted in the unit cells to the outside.

[0072] [Mode for carrying out the invention] Specific examples of the present invention will be presented below. However, the examples described below are merely for the purpose of specifically illustrating or explaining the present invention and are not intended to limit the present invention. Furthermore, details not described herein can be fully inferred by those skilled in the art, and therefore, a detailed description thereof will be omitted.

[0073] Preparation Example 1: Preparation of printing composition

[0074] Cerium nitrate, an antioxidant, was added to a mixed solvent of n-propyl alcohol (nPA) and ethanol to a concentration of 5 wt %. A small amount of black ink was added to facilitate visual observation after film formation. The mixture was ultrasonically treated to disperse the antioxidant, producing a printing composition. The mixed solvent was prepared in a weight ratio of 3:7 or 7:3. Two types of printing compositions were thus prepared.

[0075] Manufacturing example 2: Formation of digitally printed film

[0076] The printing composition prepared in the above Preparation Example was printed on the surface of a fluorine-based reinforced composite film using an inkjet printer with a 256-head nozzle, setting a digital image (140 dpi resolution) of 5 cm x 5 cm, and then dried to form a digitally printed film. Figure 5 shows the digitally printed film. When the nPA:EtOH ratio was 7:3 and the amount of nPA, which has a relatively high boiling point, was high, it was difficult to evaporate after coating, resulting in unevenness and uncoated areas on the film surface after printing. In contrast, when the nPA:EtOH ratio was 3:7 and the amount of EtOH, which has a relatively low boiling point, was high, it was possible to achieve a uniform coating without unevenness or spreading due to the rapid drying characteristics after printing.

[0077] Example 1: MEA containing the polymer electrolyte membrane according to the present invention (structure (d) in FIG. 1)

[0078] Using the printing composition of Preparation Example 1, in which the ratio of nPA to EtOH was 3:7, a 5 cm x 5 cm square image was digitally printed on one side of a 20 μm thick reinforced composite membrane to produce a reinforced composite polymer electrolyte membrane having the structure shown in Figure 1(d). The resolution of the digital image was 140 dpi. According to this resolution, the content of the antioxidant in the polymer electrolyte membrane was 7 μg / cm. 2One side of the digitally printed antioxidant was designated as the reducing electrode surface, and a membrane-electrode assembly (MEA) with an area of ​​5 cm x 5 cm was fabricated.

[0079] Comparative Example 1: MEA containing a polymer electrolyte membrane (structure (a) in FIG. 1) to which no antioxidant has been added

[0080] An MEA was produced in the same manner as in Example 1, except that a reinforced composite polymer electrolyte membrane having the structure shown in FIG. 1(a) in which no antioxidant was used was used.

[0081] Comparative Example 2: MEA containing a polymer electrolyte membrane with an antioxidant uniformly distributed therein (structure (b) in FIG. 1)

[0082] Cerium nitrate was used as an antioxidant, and the content of the antioxidant in the polymer electrolyte membrane was 12 μg / cm 2 An MEA was produced in the same manner as in Example 1, except that a reinforced composite polymer electrolyte membrane having the structure shown in FIG. 1(b) was produced and used so that the MEA satisfies the above formula.

[0083] Experimental example: Evaluation of battery performance and durability

[0084] The unit cell performance and accelerated durability were evaluated using the MEAs prepared in Example 1, Comparative Example 1, and Comparative Example 2. To evaluate the cell performance, the current density (A / cm) was measured at a voltage of 0.65 V under humidified conditions of 65°C and 50% RH. 2 ) were compared. In addition, to evaluate the chemical durability of the additives, the OCV (Open Circuit Voltage) degradation time was evaluated under cell operating conditions of 90°C and RH 30%. The OCV degradation time was compared based on the time it takes for the OCV value to deteriorate to 20% of the initial OCV value. The results are shown in Table 1 below.

[0085] [Table 1]

[0086] From Table 1, it can be seen that in the case of Comparative Example 1 without any additive, the OCV accelerated durability time is 310 hours, while in the case of the reinforced membrane in Comparative Example 2, in which a certain additive is uniformly distributed, the battery performance is partially reduced, but the OCV chemical durability time is improved to 585 hours. In contrast, in Example 1, the reinforced membrane in which 7 μg / cm2 of additive is distributed on the reduction electrode contact surface is 2 In the case of the MEA with the digitally printed additive, the battery performance was comparable to that of Comparative Example 1, and the OCV chemical durability time was improved to 510 hours. Furthermore, even though an even smaller amount of additive (almost half the amount) was used compared to Comparative Example 2, the battery performance and durability were comparable to those of Comparative Example 2.

Claims

1. providing a printing composition containing a functional additive; and printing the printing composition onto one or both sides of a polymer electrolyte membrane using a digital printing device to form a digitally printed membrane.

2. The method for producing a polymer electrolyte membrane according to claim 1 , wherein the functional additive is an antioxidant that removes peroxides or radicals.

3. 3. The method for producing a polymer electrolyte membrane according to claim 2, wherein the antioxidant is at least one selected from the group consisting of transition metals, noble metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof.

4. 3. The method for producing a polymer electrolyte membrane according to claim 2, wherein the antioxidant comprises one or more transition metals selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd).

5. 2. The method for producing a polymer electrolyte membrane according to claim 1, wherein the functional additive is contained in the printing composition at a concentration of 0.1 to 20 wt % based on the total weight of the composition.

6. The method for producing a polymer electrolyte membrane according to claim 1 , wherein the printing composition further comprises a solvent, and further comprises a step of drying after the formation of the digitally printed membrane.

7. The method for producing a polymer electrolyte membrane according to claim 6 , wherein the solvent is a mixed solvent containing two or more types of alcohol.

8. 8. The method for producing a polymer electrolyte membrane according to claim 7, wherein the solvent is a mixed solvent in which propyl alcohol and ethanol are mixed in a weight ratio of 6:4 to 2:

8.

9. 2. The method for producing a polymer electrolyte membrane according to claim 1, wherein the digital printing device includes a printer selected from the group consisting of an inkjet printer, a laser printer, an aerosol printer, and a thermal transfer or dye-sublimation printer, and the printing composition is printed by the printer.

10. 2. The method for producing a polymer electrolyte membrane according to claim 1, further comprising the steps of: designing a pattern image of the digitally printed membrane using computer software; and transmitting the pattern image to a printer, wherein the printing composition is printed on the polymer electrolyte membrane in a pattern corresponding to the pattern image.

11. 11. The method for manufacturing a polymer electrolyte membrane according to claim 10, wherein the step of designing a pattern image of the digitally printed membrane further comprises a step of setting a resolution of the pattern image, and a printing amount of the printing composition is determined according to the resolution.

12. The method for producing a polymer electrolyte membrane according to claim 1 , wherein the polymer electrolyte membrane is a reinforced composite membrane comprising a porous support and an ion conductor.

13. A method for producing a membrane-electrode assembly, comprising the step of contacting a polymer electrolyte membrane and an electrode so that a digitally printed version of the polymer electrolyte membrane produced by the method of claim 1 faces the electrode.

Images