KR100778502B1 - Polymer membrane and membrane-electrode assembly for fuel cell and fuel cell system - Google Patents

Abstract

The present invention relates to a polymer electrolyte membrane for a fuel cell, a membrane-electrode assembly for a fuel cell and a fuel cell system including the same, wherein the polymer electrolyte membrane includes a hydrogen ion conductive cation exchange resin, a hydrogen ion nonconductive polymer, and an inorganic additive.

The polymer electrolyte membrane of the present invention has a thin thickness, excellent ion conductivity and mechanical properties, and excellent barrier property against hydrocarbon fuel.

Inorganic silicate, cation exchange resin, polyvinylidene fluoride, fuel cell, methanol

Description

Polymer electrolyte membrane for fuel cell, membrane-electrode assembly and fuel cell system for fuel cell comprising same {POLYMER MEMBRANE AND MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL CELL AND FUEL CELL SYSTEM}

1 is a schematic diagram showing the structure of a direct oxidation fuel cell system of the present invention.

Figure 2 is a TEM photograph of the surface of the polymer electrolyte membrane prepared according to Example 1 of the present invention.

Figure 3 is a TEM photograph of the surface of the polymer electrolyte membrane prepared according to Example 2 of the present invention.

4 is an X-ray diffraction peak measurement graph of the polymer electrolyte membrane of Examples 1, 3 to 5 and Comparative Example 1 of the present invention.

5 is a graph showing the measurement of methanol permeability of the polymer electrolyte membranes of Examples 1, 3, 4, and 5 and Comparative Examples 1, 3 to 6 of the present invention.

Figure 6 is a graph showing the measurement of the hydrogen ion conductivity of the polymer electrolyte membrane of Example 1, Comparative Example 2 and Reference Example of the present invention.

[Industrial use]

The present invention relates to a polymer electrolyte membrane for a fuel cell, a membrane-electrode assembly for a fuel cell and a fuel cell system including the same. More specifically, a polymer electrolyte membrane for a fuel cell capable of preventing crossover of a hydrocarbon fuel, and a fuel comprising the same A membrane-electrode assembly for a battery and a fuel cell system.

[Prior art]

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

This fuel cell is a clean energy source that can replace fossil energy, and has the advantage of generating a wide range of outputs by stacking unit cells, and having an energy density of 4-10 times that of a small lithium battery. It is attracting attention as a compact and mobile portable power source.

Representative examples of the fuel cell system include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell (Direct Oxidation Fuel Cell). When methanol is used as the fuel in the direct oxidation fuel cell, it is called a direct methanol fuel cell (DMFC).

The polymer electrolyte fuel cell has an advantage of having a high energy density and a high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen as fuel gas. There is a problem that requires additional equipment such as a device.

On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but it is easy to handle fuel and has a low operating temperature, so that it can be operated at room temperature, in particular, it does not require a fuel reformer.

In such fuel cell systems, the stack that substantially generates electricity may comprise several to tens of unit cells consisting of a membrane-electrode assembly (MEA) and a separator (or bipolar plate). It has a laminated structure. The membrane-electrode assembly is called an anode electrode (also called "fuel electrode" or "oxide electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") with a polymer electrolyte membrane including a hydrogen ion conductive polymer therebetween. Has a structure in which

As the polymer electrolyte membrane, a membrane made of a perfluorosulfonic acid resin (trade name: Nafion) having excellent conductivity, mechanical properties, and chemical resistance is carbonized by polytetrafluoroethylene main chain, having high oxygen solubility, electrochemical stability, and durability. It is mainly used because it has an advantage that it is superior to the hydrogen-based polymer electrolyte membrane. The perfluorosulfonic acid resin film is generally marketed to a thickness of 50-175㎛, the thicker the thickness of the perfluorosulfonic acid resin film is improved dimensional stability and mechanical properties, but the conductivity (conductance) of the resin film is reduced On the contrary, as the thickness decreases, the resistance of the resin membrane is lowered, but not only the mechanical properties are lowered, but also fuel gases and liquids that do not react during the operation of the cell pass through the polymer membrane, resulting in fuel loss and deterioration of the battery performance. have.

It is an object of the present invention to provide a polymer electrolyte membrane for a fuel cell capable of preventing hydrogen ion conductivity and crossover of hydrocarbon fuels.

Another object of the present invention is to provide a membrane-electrode assembly for a fuel cell comprising the polymer electrolyte membrane.

Still another object of the present invention is to provide a fuel cell system including the polymer electrolyte membrane.

In order to achieve the above object, the present invention provides a polymer electrolyte membrane comprising a hydrogen ion conductive cation exchange resin, a hydrogen ion non-conductive polymer and an inorganic additive. The polymer electrolyte membrane of the present invention may further include a porous support including the hydrogen ion conductive cation exchange resin, the hydrogen ion nonconductive polymer and the inorganic additive, the hydrogen ion nonconductive support polymer, and the plurality of pores. have. In this case, since the hydrogen ion conductive cation exchange resin, the hydrogen ion non-conductive polymer and the inorganic additive play a role of transferring the hydrogen ions, the hydrogen ion transfer layer is called a hydrogen ion transfer layer, and the hydrogen ion transfer layer is formed on the pores or the surface of the porous support. Can be located.

The present invention also provides an anode electrode and a cathode electrode positioned opposite each other and a membrane-electrode assembly for a fuel cell comprising the polymer electrolyte membrane.

The invention also provides a fuel cell system comprising at least one electricity generator, a fuel supply and an oxidant supply. The electricity generating unit includes at least one membrane-electrode assembly including an anode electrode and a cathode electrode which are positioned to face each other, and a polymer electrolyte membrane having the above configuration and positioned between the anode electrode and the cathode electrode. It includes. The fuel supply unit serves to generate electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant, and the oxidant supply unit serves to supply an oxidant to the electricity generator.

Hereinafter, the present invention will be described in more detail.

As the thickness of the perfluorosulfonic acid resin membrane used as the polymer electrolyte membrane in the fuel cell increases, the dimensional stability and mechanical properties are improved, but the conductivity of the resin membrane decreases. The mechanical properties are lowered, and fuel gases and liquids that do not react during cell operation pass through the polymer membrane, causing loss of fuel and deteriorating cell performance.

In particular, when using hydrocarbon fuels such as methanol, ethanol or propanol, excess hydrocarbon fuel is permeated through the hydrophilic domain of perfluorosulfonic acid and oxidized at the cathode, resulting in fuel loss and reduction of oxygen. By reducing the spot, battery performance is greatly reduced.

In order to solve this problem, a hydrocarbon fuel polymer having good conductivity but not having good conductivity is mixed with a perfluorosulfonic acid resin to prepare a completely compatible polymer blend, thereby maintaining hydrocarbon fuel resolution while maintaining hydrogen ion conductivity. Attempts have been made to improve. Polyvinylidene fluoride-based polymers, which have partial compatibility with perfluorosulfonate resins and have excellent chemical resistance, have been attracting attention as such hydrocarbon-based polymers. There is a drawback of severe deviation in the thickness direction.

The present invention relates to a polymer electrolyte membrane of a novel fuel cell that can solve this problem. Particularly, in the case of the composite of perfluorosulfonic acid resin and polyvinylidene fluoride, which has been attempted to solve the problem that the thickness of the perfluorosulfonic acid resin that has been previously used as a polymer electrolyte membrane cannot be reduced, Phase separation occurs in the process to solve the problem of severe deviation in the thickness direction of the conductivity.

The polymer electrolyte membrane of the present invention comprises a hydrogen ion conductive cation exchange resin, a hydrogen ion nonconductive polymer and an inorganic additive.

The polymer electrolyte membrane of the present invention may further include a porous support including the hydrogen ion conductive cation exchange resin, the hydrogen ion nonconductive polymer and the inorganic additive, the hydrogen ion nonconductive support polymer, and the plurality of pores. have. In this case, since the hydrogen ion conductive cation exchange resin, the hydrogen ion non-conductive polymer and the inorganic additive play a role of transferring the hydrogen ions, the hydrogen ion transfer layer is called a hydrogen ion transfer layer, and the hydrogen ion transfer layer is formed on the pores or the surface of the porous support. Can be located.

The hydrogen ion non-conductive polymer improves mechanical properties and hydrocarbon fuel separation performance of an electrolyte membrane in a thin film state, and examples thereof include polyvinylidene fluoride homopolymer, copolymer of polyvinylidene fluoride and hexafluoropropylene, Preference is given to polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol or mixtures thereof.

In addition, the hydrogen ion non-conductive support polymer may be polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyimide, polybenzoxa At least one homopolymer selected from the group consisting of polybenzoxazole and polybenzimidazole, or at least one copolymer thereof may be used.

In this case, when the polymer electrolyte membrane of the present invention has a structure including a hydrogen ion transport layer, the hydrogen ion nonconductive supporting polymer constituting the porous support may be polytetrafluoroethylene, polyvinylidene fluoride, or polytetrafluoroethylene. 1 type of fluorine system selected from the group consisting of copolymers of polyvinylidene fluoride is preferred, and polytetrafluoroethylene is most preferred. This is preferable because the cation exchange resin generally used is a fluororesin, so that both the porous support and the cation exchange resin are equally fluoro-based, the bonding force is increased. In addition, the porous support preferably has a porosity of 60% or more, and more preferably 60-90% porosity. If the porosity of the porous support is less than 60%, since the content of the hydrogen ion transport layer positioned on the surface of the porous support is relatively small, the conductivity may be lowered, which is not preferable.

The inorganic additives are dispersed in the polymer electrolyte membrane in the nano phase, and inhibit the phase separation of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer, and at the same time improve the hydrocarbon fuel barrier property and thermal stability. To improve.

As the inorganic additive, an inorganic silicate is preferable. These inorganic silicates are pyrophylite-talc, montmorillonite (MMT), saponite, fluorohectorite, kaolinite, vermiculum, depending on the degree of internal negative charge. It may be classified as vermiculite, laponite, illite, mica, brittle mica, tetrasilicic mica, which may be classified as one or more of the present invention. It can mix and use 1 or more types.

The montmorillonite has a structure in which Mg ²⁺ , Fe ²⁺ , Fe ³⁺ ions are substituted for Al ³⁺ ions in the alumina octahedron sheet, and Al ³⁺ ions are substituted for Si ⁴⁺ ions in the silicate tetrahedron sheet, and the total amount of negative charge It becomes It also contains cations and water molecules that can be exchanged between the silicate layers to balance the charge as a whole.

The silicate preferably has a ratio (aspect ratio, aspect ratio) between short axis and long axis of 1/50 to 1/1000, more preferably 1/100 to 1/800, and most preferably 1/500 to 1/800. When the ratio between the short axis and the long axis of the silicate is greater than 1/50, the separated silicate does not act as a diffusion barrier of gas and liquid, so that the resolution is remarkably lowered, which is not preferable. In addition, when the ratio of the short axis and the long axis of the silicate is less than 1/1000, it is difficult to be peeled off due to the penetration of the cation exchange resin chain, which is difficult to disperse in the resulting polymer electrolyte membrane, which is not preferable.

The silicate is preferably used after being treated with an organic agent, and when treated with such an organic agent, the silicate layer is difficult to be separated and dispersed in a polymer resin due to strong van der Waals attraction. It is preferable because an amount of the organizing agent is inserted to facilitate the penetration of the polymer resin and the peeling and dispersion are facilitated.

As the organic agent, an alkylamine having 1 to 20 carbon atoms, an alkylene diamine having 1 to 20 carbon atoms, a quaternary ammonium salt having 1 to 20 carbon atoms or aminohexane may be used. Specific examples of the alkylamine include methylamine hydrochloride and propyl amine. , Butyl amine, octyl amine, decyl amine, dodecyl amine, hexadecyl amine, octadecyl amine, N-methyl octadecyl amine, and the like.

Examples of the alkylene diamine include 1,6-hexamethylene diamine and 1,12-dodecane diamine, and as quaternary alkyl ammonium, dimethyl quaternary ammonium, benzyl quaternary ammonium, 2-ethylhexyl quaternary ammonium, bis 2-hydroxyethyl quaternary ammonium, methyl quaternary ammonium; alkyl ammonium salts include tetramethylammonium chloride, octadecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide, bis (2) -Hydroxyethyl) methyl octadecyl ammonium chloride, 1-hexadecylpyridium chloride, etc. can be used, and 6-aminohexane, 12-aminohexane, etc. can be used as an aminohexane.

In addition, although the inorganic silicate may be used by treating with the above-mentioned organic agent, an organically treated inorganic silicate which has already been commercialized may be used directly. Examples of such organically treated inorganic silicates include Cloisite6A, Cloisite10A, Cloisite15A, Cloisite20A, Cloisite25A, Cloisite30B and the like under the trade names of Southern Clay Products, Inc., and it is preferable to use Cloisite10A.

In addition, the hydrogen ion conductive cation exchange resin imparts ion conductivity to the prepared composite membrane. The hydrogen ion conductive cation exchange resin may be a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups, and derivatives thereof in the side chain. In addition, the conductive cation exchange resin preferably has an ion exchange ratio of 3 to 33 and an equivalent weight (EW) of 700 to 2,000. The ion exchange ratio of the ion exchange resin is defined by the number of carbon and cation exchange groups in the polymer backbone.

Representative examples of the ion exchange resin having a cation exchange group include fluoro-based polymers, benzimidazole-based polymers, polyimide-based polymers, polyetherimide-based polymers, polyphenylene sulfide-based polymers, polysulfone-based polymers, and polyether sulfone-based polymers. It may include at least one hydrogen ion conductive polymer selected from a polymer, a polyether ketone-based polymer, a polyether-ether ketone-based polymer or a polyphenylquinoxaline-based polymer.

Examples of the fluoro-based polymer include poly (perfluorosulfonate) of Formula 1 (trade name: Nafion (EI Dupont de Nemours), Aciplex (Asahi Kasei Chemical), Flemion (Asahi Glass) and Fumion (fumatech)). Sold), fluorocarbon vinyl ether of formula 2 or fluorinated vinyl ether of formula 3 can be used. Or the polymers described in US Pat. Nos. 4,330,654, 4,358,545, 4,417,969, 4,610,762, 4,433,082 and 5,094,995, 5,596,676 and 4,940,525.

[Formula 1]

(In Formula 1, X is H, Li, Na, K, Cs, tetrabutylammonium or NR1R2R3R4, R1, R2, R3 and R4 are independently H, CH ₃ or C ₂ H ₅ , and m is 1 or more. , n is at least 2, x is about 5 to 3.5, and y is at least 1,000.)

[Formula 2]

MSO ₂ CFRfCF ₂ O [CFYCF ₂ O] nCF = CF ₂

(In Formula 2, Rf is fluorine or a C1 to C10 perfluoroalkyl radical, Y is a fluorine or trifluoromethyl radical, n is an integer from 1 to 3, M is a fluorine, hydroxyl radical, amino Radicals and -OMe (Me is selected from the group consisting of alkali metal radicals and quaternary ammonium radicals)

[Formula 3]

(In Formula 3, k is 0 or 1, l is an integer of 3 to 5)

Poly (perfluorosulfonic acid) having the above structure (trade name: Nafion) has a micellar structure when the sulfonic acid group at the chain end is hydrated, which provides a passage for hydrogen ion migration and behaves like a typical aqueous solution acid. see. When the perfluorosulfonic acid (trade name: Nafion) is used as the cation exchange resin in the present invention, in the side chain terminal ion exchange group (-SO ₃ X), X is a monovalent ion such as hydrogen, sodium, potassium, cesium, and tetrabutyl. It can be substituted with Ammonium (TBA).

Or a benzimidazole-based polymer, a polyimide-based polymer, a polyetherimide-based polymer, a polyphenylene sulfide-based polymer, a polysulfone-based polymer, a polyether sulfone-based polymer, a polyether ketone-based polymer, a polyether-etherketone-based polymer, or Specific examples of the polyphenylquinoxaline-based polymer include polybenzimidazole, polyimide, polysulfone, polysulfone derivative, sulfonated poly (ether ether ketone: s-PEEK), poly Phenylene oxide, polyphenylene sulfide, polyphosphazene, etc. can be used.

In addition, ethylene, propylene, fluoroethylene polymer, ethylene / tetrafluoroethylene (ethylene / tetrafluoroethylene) or the like in the form of a polystyrene sulfonic acid polymer graft (grafted) may be used.

In the polymer electrolyte membrane of the present invention, the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer are preferably present in a weight ratio of 50 to 90:50 to 10, more preferably in a weight ratio of 70 to 80:30 to 20. desirable. In addition, the inorganic additive is preferably present in 1 to 10 parts by weight, more preferably in 1 to 5 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer. When the content of the hydrogen ion nonconductive polymer and the inorganic additive is larger than the above range and the hydrogen ion conductive cation exchange resin is smaller than the above range, the conductivity is lowered, which is undesirable, and vice versa, the hydrocarbon fuel barrier properties It is lowered and is not preferable.

The polymer electrolyte membrane of the present invention has a thin film of 10 to 50 μm, and even with such a thin thickness, the hydrocarbon fuel separation ability is very excellent, and when the electrolyte membrane is applied to a fuel cell, the output density can be improved.

In order to prepare the polymer electrolyte membrane of the present invention, first, an ion exchange resin having a cation exchange group is dissolved in an organic solvent to prepare a cation exchange resin solution. At this time, the amount of the cation exchange resin added is preferably 0.5 to 30% by weight.

It is preferable to use a hydrophobic organic solvent such as dimethyl acetate as the organic solvent, hydrophilic organic solvent such as alcohol is not suitable. This is because the cation exchange resin is hydrophilic, but since the inorganic additives added are hydrophobic, when an hydrophilic solvent such as alcohol is used as the organic solvent, the inorganic additives are precipitated, which is not preferable. As the hydrophobic organic solvent, dimethyl acetate, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidinone and mixtures of one or more thereof may be used.

In addition, when poly (perfluorosulfonic acid) is used as a commercial cation exchange resin, since it is generally dissolved in a mixed solvent such as water and 2-propanol, when it is used, it is forcibly evaporated at room temperature, and then dimethyl acetate or the like. The cation exchange resin solution may also be prepared by dissolving again in a hydrophobic solvent at a concentration of about 0.5 to 30% by weight.

A hydrogen ion nonconductive polymer solution is added to the prepared cation exchange resin solution to prepare a cation exchange resin-polymer solution. The hydrogen ion nonconductive polymer solution is prepared by adding a hydrogen ion nonconductive polymer to a concentration of 5 to 30% by weight in a solvent. At this time, dimethylacetamide, dimethylformamide, etc. may be used as a solvent, and the above-mentioned thing is used as said hydrogen ion nonconductive polymer. The mixing ratio of the cation exchange resin solution and the hydrogen ion nonconductive polymer solution is preferably such that the cation exchange resin and the hydrogen ion nonconductive polymer are 50 to 90:50 to 10 weight ratio, and the 70 to 80:30 to 20 weight ratio is More preferably.

Subsequently, an inorganic additive is added to the cation exchange resin-polymer solution and mixed. This mixing process is preferably carried out under mechanical or ultrasonic stirring conditions at temperatures in the range of about 50 to 120 ° C. If the temperature of the mixing step is lower than 50 ° C, the mixing step is delayed and not preferable. If the temperature of the mixing step is higher than 120 ° C, the solvent is evaporated and the concentration is difficult to control.

The addition amount of the inorganic additive is preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer. If the content of the inorganic additive is less than 1 part by weight, the effect of blocking the crossover of hydrocarbon fuel is reduced. If the content of the inorganic additive is more than 10 parts by weight, the polymer electrolyte membrane produced is brittle and is not preferable.

Subsequently, the obtained solution is used to film in a conventional manner to prepare a polymer electrolyte membrane.

In this case, the obtained solution is coated on a porous support formed of a hydrogen ion nonconductive support polymer, and then dried at 100 to 120 ° C. to prepare a polymer electrolyte membrane. The coating process may be carried out by a general coating process such as roll coating, dip coating, spray coating or slot-die coating.

The manufacturing method is relatively simple in its process and is advantageous for mass production.

The membrane-electrode assembly for a fuel cell of the present invention comprising the polymer electrolyte membrane of the present invention includes an anode electrode and a cathode electrode positioned opposite to each other, and the polymer electrolyte membrane of the present invention positioned between the anode electrode and the cathode electrode.

The cathode and anode electrodes comprise an electrode substrate and a catalyst layer.

The catalyst layer is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn , At least one catalyst selected from the group consisting of Sn, Mo, W, Rh, and Ru). As described above, the anode electrode and the cathode electrode may use the same material, but in order to prevent the catalyst poisoning caused by CO generated during the anode electrode reaction in the direct oxidation fuel cell, a platinum-ruthenium alloy catalyst is used as the anode. It is more preferable as an electrode catalyst. Representative examples include Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W, Pt / One or more selected from the group consisting of Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a metal catalyst may be used as the metal catalyst (black) itself, or may be supported on a carrier. As the carrier, carbonaceous materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs or activated carbon may be used, or alumina, silica, zirconia, Inorganic fine particles such as titania may be used, but carbon-based materials are generally used.

The catalyst layer may further include a binder resin for improving the adhesion of the catalyst layer and the transfer of hydrogen ions.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder resin, more preferably a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. Any polymer resin which has can be used. Preferably, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether One or more hydrogen ion conductive polymers selected from ether ketone polymers or polyphenylquinoxaline polymers, more preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), Copolymers of tetrafluoroethylene with fluorovinyl ether containing sulfonic acid groups, defluorinated polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole One containing at least one hydrogen ion conductive polymer selected from (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) or poly (2,5-benzimidazole) may be used.

The hydrogen ion conductive polymer may replace H with Na, K, Li, Cs or tetrabutylammonium in an ion exchange group at the side chain end. In case of replacing H with Na in the side chain terminal ion exchanger, NaOH is substituted for the preparation of the catalyst composition, and tetrabutylammonium hydroxide is substituted for tetrabutylammonium, and K, Li or Cs may be substituted with appropriate compounds. It can be substituted using. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The binder resin may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive polymer for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to adjust the usage-amount so that it may be suitable for a purpose of use.

Examples of the nonconductive polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), and ethylene / tetrafluoro Ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), dode At least one selected from the group consisting of silbenzenesulfonic acid and sorbitol is more preferred.

The electrode substrate plays a role of supporting the electrode and diffuses the fuel and the oxidant to the catalyst layer, thereby serving to easily access the fuel and the oxidant to the catalyst layer. The electrode substrate is a conductive substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer fiber composed of metal cloth in a fibrous state). The metal film is formed on the surface of the cloth formed with)) may be used, but is not limited thereto.

In addition, it is preferable to use a water-repellent treatment with a fluorine-based resin as the electrode base material because it can prevent the reactant diffusion efficiency from being lowered by water generated when the fuel cell is driven. Examples of the fluorine resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene Fluorinated ethylene propylene, polychlorotrifluoroethylene, fluoroethylene polymers or copolymers thereof can be used.

In addition, a microporous layer may be further included to enhance the reactant diffusion effect in the electrode substrate. These microporous layers are generally conductive powders having a small particle diameter, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, and carbon nanohorns. -horn or carbon nano ring.

The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. The binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate Or copolymers thereof and the like can be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, etc. may be preferably used. The coating process may be screen printing, spray coating, or coating using a doctor blade according to the viscosity of the composition, but is not limited thereto.

In addition, the fuel cell system of the present invention includes at least one electricity generating portion, a fuel supply portion and an oxidant supply portion.

The electricity generating unit includes a polymer electrolyte membrane of the present invention, cathode and anode electrodes and separators (also referred to as "bipolar plates") existing on both sides of the polymer electrolyte membrane, and generates electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant. It plays a role.

The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant to the electricity generation unit. In the present invention, the fuel may include a hydrocarbon fuel in gas or liquid state. Representative examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol or natural gas. Examples of the oxidant include oxygen or air. As such, the fuel cell system of the present invention is preferably a direct oxidation fuel cell system using a hydrocarbon fuel.

A schematic structure of the fuel cell system of the present invention is shown in FIG. 1, which will be described in more detail with reference to the following. Although the structure shown in FIG. 1 shows a system for supplying fuel and oxidant to an electric generator using a pump, the fuel cell system of the present invention is not limited to such a structure, and a fuel cell using a diffusion method without using a pump is shown. Of course, it can also be used for system architecture.

The fuel cell system 1 of the present invention includes at least one electricity generation unit 3 for generating electrical energy through an oxidation reaction of a fuel and a reduction reaction of an oxidant, a fuel supply unit 5 for supplying the fuel, And an oxidant supply unit 7 for supplying an oxidant to the electricity generation unit 3.

In addition, the fuel supply unit 5 for supplying the fuel may include a fuel tank 9 storing fuel and a fuel pump 11 connected to the fuel tank 9. The fuel pump 11 serves to discharge the fuel stored in the fuel tank 9 by a predetermined pumping force.

The oxidant supply unit 7 for supplying the oxidant to the electricity generating unit 3 includes at least one oxidant pump 13 for sucking the oxidant with a predetermined pumping force.

The electricity generator 3 is composed of a membrane-electrode assembly 17 for oxidizing and reducing a fuel and an oxidant, and a separator 19 and 19 'for supplying fuel and an oxidant to both sides of the membrane-electrode assembly. At least one of these electricity generating units 3 constitutes a stack 15.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

(Example 1)

Perfluorosulfonate resin solution (Solution Technology, 5 wt% Nafion / H ₂ O / 2-Propanol, EW1100) dissolved in commercially available water and 2-propanol was forcibly evaporated at room temperature, followed by dimethyl acetate. A cation exchange resin solution was prepared by adding amide (DMA) at a concentration of 5% by weight and stirring at 100 ° C. for 24 hours to dissolve the cation exchange resin.

Polyvinylidene fluoride (PVdF, Elf Atochem, Kynar761) hydrogen ion non-conductive polymer was added to DMA at a concentration of 5% by weight, dissolved after stirring at 100 ° C. for 24 hours, 70 g of the Nafion / DMA solution and the PVdF / DMA 30 g of the solution was mixed and stirred at 100 ° C. for at least 24 hours to prepare a compatible cation exchange resin-polymer solution. To the obtained cation exchange resin-polymer solution, montmorillonite inorganic additive particles (aspect ratio: 1 / 200-1 / 800, Cloisite 10A (manufactured by Southern Clay Products, Inc.)) were added at a temperature of 100 ° C., mechanically stirred, and ultrasonically applied to inorganic substances. The components were uniformly dispersed to prepare a hydrogen ion transport layer composition, wherein the amount of the montmorillonite inorganic additive was 1 part by weight based on 100 parts by weight of the total amount of the hydrogen ion nonconductive cation exchange resin and the hydrogen ion nonconductive polymer.

The hydrogen ion transport layer composition was coated on a polyvinylidene fluoride polymer support having a porosity of 60% or more, and then dried at 100 ° C. to prepare a polymer electrolyte membrane for a fuel cell. The prepared polymer electrolyte membrane had a total thickness of 30 μm, and the inorganic additive was dispersed in a nano state in the polymer electrolyte membrane. In the prepared polymer electrolyte membrane, the ratio of the cation exchange resin, the hydrogen ion nonconductive polymer, and the inorganic additive was 70: 30: 1 by weight.

(Example 2)

Except that the amount of the montmorillonite inorganic additive was added to 10 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion nonconductive cation exchange resin and the hydrogen ion nonconductive polymer was carried out in the same manner as in Example 1.

TEM images of the surface of the polymer electrolyte membrane prepared according to Examples 1 and 2 are shown in FIGS. 2 and 3, respectively. The darker portions in FIGS. 2 and 3 are the portions where montmorillonite and polyvinylidene fluoride are mixed, and the long lines (particularly inside the circles in FIG. 2) represent MMT.

(Example 3)

The amount of the montmorillonite inorganic additive was added in the same manner as in Example 1 except that the amount of the montmorillonite inorganic additive was changed to 3 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer.

(Example 4)

The amount of the montmorillonite inorganic additive was added in the same manner as in Example 1 except that the amount of the montmorillonite inorganic additive was changed to 5 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer.

(Example 5)

The addition amount of the montmorillonite inorganic additive was carried out in the same manner as in Example 1 except that the amount of the montmorillonite inorganic additive was changed to 7 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer.

(Comparative Example 1)

A commercially available Nafion 117 polymer electrolyte membrane was used.

(Comparative Example 2)

A commercially available Nafion 115 polymer electrolyte membrane was used.

(Comparative Example 3)

To 100 parts by weight of the cation exchange resin solution prepared in Example 1, using a mixed solution prepared by adding 1 part by weight of montmorillonite inorganic additive particles (aspect ratio: 1 / 200-1 / 800, Cloisite 10A (manufactured by Southern Clay Products, Inc.)) To prepare a polymer electrolyte membrane by a conventional filming process.

(Comparative Example 4)

The same procedure as in Comparative Example 3 was carried out except that the amount of the montmorillonite inorganic additive was changed to 3 parts by weight.

(Comparative Example 5)

The same procedure as in Comparative Example 3 was conducted except that the amount of the montmorillonite inorganic additive was changed to 5 parts by weight.

(Comparative Example 6)

The same procedure as in Comparative Example 3 was conducted except that the amount of the montmorillonite inorganic additive was changed to 7 parts by weight.

* X-ray diffraction peak measurement of polymer electrolyte membrane

In order to find out whether the cation exchange resin and the silicate compound are uniformly dispersed in the polymer electrolyte membranes of Examples 1, 3 to 5 and Comparative Example 1, the polymer electrolytes of Examples 1, 3 to 5 and Comparative Example 1 The X-ray diffraction peaks of the films were measured and the results are shown in FIG. 4.

X-ray diffraction peaks were measured using a CuKα line (λ = 1.5406 Hz) using an X-ray diffractometer (X-ray diffractometer, Phillips, X'pert Pro X-ray). The portion indicated by the arrow in FIG. 4 is a portion in which a specific peak of MMT generally appears. As Nafion, MMT, and PVdF are well mixed with each other, it can be seen that a specific peak of MMT does not appear. In addition, since it shows a similar X-ray diffraction peak regardless of the presence or absence of MMT addition amount, it can be seen that the crystallinity of the polymer electrolyte membrane does not change with MMT addition.

* Methanol permeability measurement

In addition, the methanol permeability of the polymer electrolyte membranes of Examples 1, 3, 4, and 5 and Comparative Examples 1, 3 to 6 were measured, and the results are shown in FIG. 5.

As shown in FIG. 5, it can be seen that the methanol permeability of Examples 1, 3, 4 and 5 is significantly lower than that of Comparative Example 1. In addition, although the montmorillonite inorganic additive was used, it can be seen that the methanol permeability of Examples 1, 3, 4, and 5 was lower than that of Comparative Examples 3 to 6, in which the hydrogen ion nonconductive polymer was not further used. From this result, it can be seen that the inorganic additive has an effect of preventing the path of methanol in the polymer electrolyte membrane, and the effect of preventing the path of methanol is further maximized when used with a hydrogen ion nonconductive polymer.

* Hydrogen ion conductivity measurement

The hydrogen ion conductivity of Example 1 and Comparative Example 2 was measured and the results are shown in FIG. 6. In addition, the hydrogen ion conductivity measured using a polymer electrolyte membrane prepared by mixing Nafion and polyvinylidene fluoride in a 6: 4 weight ratio is shown in FIG. 6 together. As shown in FIG. 6, it can be seen that in the temperature range of the methanol direct oxidation fuel cell, appropriate hydrogen ion conductivity is exhibited regardless of the use of MMT and polyvinylidene fluoride.

The polymer electrolyte membrane of the present invention is thin in thickness, excellent in ion conductivity and mechanical properties, and excellent in barrier properties to hydrocarbon fuels, and thus can be preferably used in a direct oxidation fuel cell.

Claims (21)

Hydrogen ion conductive cation exchange resins; Hydrogen ion nonconductive polymer; And Inorganic additives including inorganic silicates having a ratio of short axis and long axis from 1/50 to 1/1000 Wherein the inorganic additive is present in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer. The method of claim 1, The hydrogen ion conductive cation exchange resin is a polymer electrolyte membrane for a fuel cell which is a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. The method of claim 1, The hydrogen ion conductive cation exchange resin is a polymer electrolyte membrane for a fuel cell is an at least one polymer resin having an ion exchange ratio of 3 to 33, the equivalent weight of 700 to 2,000. The method of claim 2, The polymer resin may be a fluoropolymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, A polymer electrolyte membrane for a fuel cell selected from the group consisting of a polyether-etherketone-based polymer and a polyphenylquinoxaline-based polymer. The method of claim 4, wherein The polymer resin is a polymer electrolyte membrane for a fuel cell is a fluoro-based polymer. The method of claim 1, Supporting the hydrogen ion conductive cation exchange resin, hydrogen ion non-conductive polymer and inorganic additives, A polymer electrolyte membrane for a fuel cell comprising a hydrogen ion non-conductive support polymer, and further comprising a porous support having a plurality of pores. The method of claim 6, The hydrogen ion non-conductive support polymer is polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyimide, polybenzoxazole A polymer electrolyte membrane for a fuel cell, which is at least one homopolymer selected from the group consisting of polybenzimidazole) and at least one copolymer thereof. The method of claim 6, The hydrogen ion nonconductive supporting polymer is at least one polymer electrolyte membrane for a fuel cell selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride and polytetrafluoroethylene-polyvinylidene fluoride copolymer. The method of claim 8, The hydrogen ion non-conductive support polymer is a polytetrafluoroethylene polymer electrolyte membrane for a fuel cell. The method of claim 1, The hydrogen ion non-conductive polymer is selected from the group consisting of polyvinylidene fluoride homopolymer, copolymer of polyvinylidene fluoride and hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate and polyvinyl alcohol Polymer electrolyte membrane for phosphorus fuel cell. The method of claim 1, The hydrogen ion conductive cation exchange resin and the hydrogen ion nonconductive polymer are present in a 50 to 90:50 to 10 weight ratio polymer electrolyte membrane for a fuel cell. The method of claim 11, The hydrogen ion conductive cation exchange resin and the hydrogen ion non-conductive polymer are present in a 70 to 80: 30 to 20 weight ratio polymer electrolyte membrane for a fuel cell. delete The method of claim 1, The inorganic additive is present in the polymer electrolyte membrane for a fuel cell is present in 1 to 5 parts by weight based on 100 parts by weight of the total amount of the hydrogen ion conductive cation exchange resin and hydrogen ion non-conductive polymer. The method of claim 1, The inorganic additive may be pyrophylite-talc, montmorillonite (MMT), saponite, fluorohectorite, kaolinite, vermiculite, laponite (laponite) A polymer electrolyte membrane for a fuel cell, which is selected from the group consisting of laponite, illite, mica, brittle mica, tetrasilicic mica and mixtures thereof. The method of claim 1, The inorganic additive is a polymer electrolyte membrane for a fuel cell that is dispersed in a nano state. The method of claim 6, The porous support is a polymer electrolyte membrane for a fuel cell having a porosity of 60% or more. An anode electrode and a cathode electrode located opposite each other; And The polymer electrolyte membrane of any one of claims 1 to 12 and 14 to 17 positioned between the anode electrode and the cathode electrode. Membrane-electrode assembly for fuel cell comprising a. The method of claim 18, The membrane electrode assembly is a fuel cell membrane electrode assembly for direct oxidation fuel cells. At least one membrane-electrode assembly and a separator including an anode electrode and a cathode electrode positioned opposite to each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, and including an oxidation reaction of a fuel and a reduction reaction of an oxidant. At least one electricity generating unit generating electricity; A fuel supply unit supplying fuel to the electricity generation unit; And An oxidant supply unit for supplying an oxidant to the electricity generation unit, 18. The fuel cell system of claim 1, wherein the polymer electrolyte membrane is the polymer electrolyte membrane of any one of claims 1 to 12 and 14 to 17. The method of claim 20, The fuel cell system is a direct oxidation fuel cell system.

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