CA2444647A1 - High-durability polymer electrolyte, high-durability polymer electrolyte composite, electrode, and fuel cell - Google Patents
High-durability polymer electrolyte, high-durability polymer electrolyte composite, electrode, and fuel cell Download PDFInfo
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- CA2444647A1 CA2444647A1 CA002444647A CA2444647A CA2444647A1 CA 2444647 A1 CA2444647 A1 CA 2444647A1 CA 002444647 A CA002444647 A CA 002444647A CA 2444647 A CA2444647 A CA 2444647A CA 2444647 A1 CA2444647 A1 CA 2444647A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
- H01M8/1023—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1044—Mixtures of polymers, of which at least one is ionically conductive
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1046—Mixtures of at least one polymer and at least one additive
- H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1046—Mixtures of at least one polymer and at least one additive
- H01M8/1051—Non-ion-conducting additives, e.g. stabilisers, SiO2 or ZrO2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention provides a high-durability polymer electrolyte, i.e., a fluoropolymer electrolyte into which a functional group containing phosphorus has been introduced, a high-durability polymer electrolyte composite consisting of a fluoropolymer electrolyte and an antioxidant, and a fuel cell in which the high-durability polymer electrolyte or the high-durability polymer electrolyte composite are employed as electrodes.
Description
HIGH-DURABILITY POLYMER ELECTROLYTE, HIGH-DURABILITY
POLYMER ELECTROLYTE COMPOSITE, ELECTRODE, AND FUEL CELL
BACKGROUND OF THE INVENTION
1. Field of the Invention The invention relates to a high-durability polymer electrolyte and a high-durability polymer electrolyte composite. More particularly, the invention relates to a high-durability polymer electrolyte and a high-durability polymer electrolyte composite which exhibit excellent oxidation resistance or the like and which are suited for an electrolyte membrane, an electrode or the like that is employed for fuel cells, water electrolysis, halogen halide electrolysis, salt electrolysis, oxygen concentrators, humidity sensors, gas sensors or the like.
POLYMER ELECTROLYTE COMPOSITE, ELECTRODE, AND FUEL CELL
BACKGROUND OF THE INVENTION
1. Field of the Invention The invention relates to a high-durability polymer electrolyte and a high-durability polymer electrolyte composite. More particularly, the invention relates to a high-durability polymer electrolyte and a high-durability polymer electrolyte composite which exhibit excellent oxidation resistance or the like and which are suited for an electrolyte membrane, an electrode or the like that is employed for fuel cells, water electrolysis, halogen halide electrolysis, salt electrolysis, oxygen concentrators, humidity sensors, gas sensors or the like.
2. Description of the Related Art A polymer electrolyte is a solid polymer material having an electrolyte functional group such as a sulfonic acid group or the like in a polymer chain. The polymer electrolyte is strongly bonded to a certain ion or is selectively pervious to a positive ion or a negative ion.
Therefore, the polymer electrolyte is formed as particles, fiber, or membranes, and is applied to various uses including electrodialysis, diffusion dialysis, battery diaphragms and the like.
For instance, a fuel cell has a pair of electrodes that are respectively provided on surfaces of a proton-conductive polymer electrolyte membrane. Hydrogen gas, which is obtained by reforming a low-molecular hydrocarbon such as methane, methanol or the like, is supplied to one of the electrodes (fuel electrode) as a fuel gas, while oxygen gas or air is supplied to the other electrode (air electrode) as an oxidant. In this manner, an electromotive force is obtained from the fuel cell. Water electrolysis is a method of producing hydrogen and oxygen by electrolyzing water by means of a polymer electrolyte membrane.
In the case of fuel cells or water electrolysis, a peroxide is generated in a catalytic layer formed on an interface between a polymer electrolyte membrane and each of electrodes. The generated peroxide turns into a peroxide radical while being diffused, and causes a reaction that deteriorates the quality of the polymer electrolyte membrane. In the case of fuel cells or water electrolysis, therefore, it is difficult to use a hydrocarbon-type electrolyte membrane that is insufficient in oxidation resistance. For this reason, a perfluoro sulfonic acid membrane, which exhibits high proton conductivity and high oxidation resistance, is generally used in the field of fuel cells or water electrolysis.
Salt electrolysis is a method of producing sodium hydroxide, chlorine, and hydrogen by electrolyzing a sodium chloride solution by means of a polymer electrolyte membrane. In this case, since the polymer electrolyte membrane is exposed to chlorine and a solution which is at a high temperature and which contains a high concentration of sodium hydroxide, it is impossible to use a hydrocarbon-type electrolyte membrane that is insufficient in resistance to chlorine or high-temperature, high-concentration sodium hydroxide solutions. For this reason, a perfluoro sulfonic acid membrane, which is resistant to chlorine and high-temperature, high-concentration sodium hydroxide solutions and into whose surface a carboxylic acid group is partially introduced so as to prevent back-diffusion of generated ions, is generally used as a polymer electrolyte membrane for salt electrolysis.
Fluoro-electrolyte membranes typified by a perfluoro sulfonic acid membrane have C-F bonding and are therefore chemically highly stable. Thus, fluoro-electrolyte membranes are used not only as the aforementioned polymer electrolyte membrane for fuel cells, water electrolysis, or salt electrolysis but also as a polymer electrolyte membrane for halogen acid electrolysis. In addition, because of their proton conductivity, fluoro-electrolyte membranes are widely applied to the fields of humidity sensors, gas sensors, oxygen concentrators and the like as well.
In particular, fluoro-electrolyte membranes typified by a perfluoro sulfonic acid membrane known as a trade name of Nafion~ (manufactured by Du Pont Co., Ltd.) are chemically highly stable and thus are designed as electrolyte membranes to be used under severe conditions.
However, fluoro-electrolytes are disadvantageous in their difficulty in fabrication and their extreme expensiveness.
On the other hand, hydrocarbon-type electrolyte membranes are advantageous in their easiness in fabrication and their inexpensiveness in comparison with fluoro-electrolyte membranes typified by Nafion~.
Nevertheless, hydrocarbon-type electrolyte membranes face a problem of low oxidation resistance as described above.
This low oxidation resistance results from the facts that hydrocarbons generally exhibit low resistance to radicals and that electrolytes having hydrocarbon skeletons tend to cause a deteriorative reaction triggered by radicals (an oxidative reaction triggered by peroxide radicals).
Therefore, the polymer electrolyte is formed as particles, fiber, or membranes, and is applied to various uses including electrodialysis, diffusion dialysis, battery diaphragms and the like.
For instance, a fuel cell has a pair of electrodes that are respectively provided on surfaces of a proton-conductive polymer electrolyte membrane. Hydrogen gas, which is obtained by reforming a low-molecular hydrocarbon such as methane, methanol or the like, is supplied to one of the electrodes (fuel electrode) as a fuel gas, while oxygen gas or air is supplied to the other electrode (air electrode) as an oxidant. In this manner, an electromotive force is obtained from the fuel cell. Water electrolysis is a method of producing hydrogen and oxygen by electrolyzing water by means of a polymer electrolyte membrane.
In the case of fuel cells or water electrolysis, a peroxide is generated in a catalytic layer formed on an interface between a polymer electrolyte membrane and each of electrodes. The generated peroxide turns into a peroxide radical while being diffused, and causes a reaction that deteriorates the quality of the polymer electrolyte membrane. In the case of fuel cells or water electrolysis, therefore, it is difficult to use a hydrocarbon-type electrolyte membrane that is insufficient in oxidation resistance. For this reason, a perfluoro sulfonic acid membrane, which exhibits high proton conductivity and high oxidation resistance, is generally used in the field of fuel cells or water electrolysis.
Salt electrolysis is a method of producing sodium hydroxide, chlorine, and hydrogen by electrolyzing a sodium chloride solution by means of a polymer electrolyte membrane. In this case, since the polymer electrolyte membrane is exposed to chlorine and a solution which is at a high temperature and which contains a high concentration of sodium hydroxide, it is impossible to use a hydrocarbon-type electrolyte membrane that is insufficient in resistance to chlorine or high-temperature, high-concentration sodium hydroxide solutions. For this reason, a perfluoro sulfonic acid membrane, which is resistant to chlorine and high-temperature, high-concentration sodium hydroxide solutions and into whose surface a carboxylic acid group is partially introduced so as to prevent back-diffusion of generated ions, is generally used as a polymer electrolyte membrane for salt electrolysis.
Fluoro-electrolyte membranes typified by a perfluoro sulfonic acid membrane have C-F bonding and are therefore chemically highly stable. Thus, fluoro-electrolyte membranes are used not only as the aforementioned polymer electrolyte membrane for fuel cells, water electrolysis, or salt electrolysis but also as a polymer electrolyte membrane for halogen acid electrolysis. In addition, because of their proton conductivity, fluoro-electrolyte membranes are widely applied to the fields of humidity sensors, gas sensors, oxygen concentrators and the like as well.
In particular, fluoro-electrolyte membranes typified by a perfluoro sulfonic acid membrane known as a trade name of Nafion~ (manufactured by Du Pont Co., Ltd.) are chemically highly stable and thus are designed as electrolyte membranes to be used under severe conditions.
However, fluoro-electrolytes are disadvantageous in their difficulty in fabrication and their extreme expensiveness.
On the other hand, hydrocarbon-type electrolyte membranes are advantageous in their easiness in fabrication and their inexpensiveness in comparison with fluoro-electrolyte membranes typified by Nafion~.
Nevertheless, hydrocarbon-type electrolyte membranes face a problem of low oxidation resistance as described above.
This low oxidation resistance results from the facts that hydrocarbons generally exhibit low resistance to radicals and that electrolytes having hydrocarbon skeletons tend to cause a deteriorative reaction triggered by radicals (an oxidative reaction triggered by peroxide radicals).
Hence, with a view to providing a high-durability polymer electrolyte which is at least equivalent in oxidation resistance with fluoro-electrolytes or practically sufficient in oxidation resistance and which can be manufactured at a low cost, patent applications regarding a high-durability polymer electrolyte which consists of a polymer compound having a hydrocarbon portion and into which a functional group containing phosphorus is introduced (Japanese Patent Application Laid-Open No. 2000-11755) and a high-durability polymer electrolyte composite obtained by mixing a polymer compound having an electrolyte functional group and a hydrocarbon portion with a compound containing phosphorus (Japanese Patent Application Laid-Open No. 2000-11756) have been filed.
However, if a hydrocarbon-type electrolyte is used in a fuel cell, use of the high-durability polymer electrolyte and the high-durability polymer electrolyte composite disclosed in the aforementioned patent publications, namely, Japanese Patent Application Laid-Open No. 2000-11755 and Japanese Patent Application Laid-Open No. 2000-11756 as a material for electrodes (anode and cathode) substantially prevents a fuel gas (hydrogen or the like) or an oxidative gas (oxygen, air or the like) from contacting a catalyst (platinum or the like), because the high-durability polymer electrolyte and the high-durability polymer electrolyte composite basically tend to shut gas off. As a result, the performance of the fuel cell deteriorates substantially. As described hitherto, the idea of combining a hydrocarbon-type electrolyte with a functional group containing phosphorus or a compound containing phosphorus brings about a problem.
SUI~1ARY OF THE INVENTION
It is an object of the invention to drastically enhance durability of a polymer electrolyte employed for 5 a fuel cell or the like.
As a result of exhaustive studies, the inventors have come up with a method of more drastically enhancing oxidation stability of a fluoropolymer electrolyte which is chemically highly stable in itself, and have attained the invention.
A first aspect of the invention relates to a high-durability polymer electrolyte composite including a polymer electrolyte and a compound containing alkyl phosphonic acid. As the polymer electrolyte, a polymer electrolyte having no C-F bonding or a fluoropolymer (especially a fluoropolymer having no C-H bonding) can be mentioned.
Fluoropolymers are chemically stable in itself, because bonding between carbon and fluorine are strongly bonded together. It was usually considered unrealistic to take measures to stabilize fluoropolymers. However, according to the knowledge acquired by the inventors, the following phenomenon occurs even in the case of fluoropolymers. That is, if a hydrogen peroxide radical or the like is generated in a fluoropolymer, the fluoropolymer is sequentially decomposed step by step into units of ether containing fluorine on a side chain.
Once a process of decomposition begins, a large amount of heat is generated because binding energy between atoms is at a high level. As a result, thermal decomposition progresses quickly.
In the invention, the compound containing alkyl phosphonic acid is blended with the fluoropolymer electrolyte, whereby the compound containing alkyl phosphonic acid quenches not only a hydrogen peroxide radical generated in the fluoropolymer electrolyte but also a decompositional radical produced during decomposition of the fluoropolymer electrolyte. Thus, oxidation stability of the fluoropolymer electrolyte is significantly enhanced. Even in the case where the compound containing alkyl phosphonic acid has been blended with a polymer electrolyte having no C-F bonding, a hydrogen peroxide radical generated in the polymer electrolyte and a decompositional radical produced during a process of decomposing the polymer electrolyte are quenched by the compound containing alkyl phosphonic acid. C-H bonding is chemically less stable than C-F
bonding and thus is apt to be attacked by radicals.
Therefore, blend of the compound containing alkyl phosphonic acid with the polymer electrolyte having no C-F bonding is effective in enhancing durability of the polymer electrolyte.
A low-molecular compound, oligomer, or a polymer is employed as the compound containing alkyl phosphonic acid to be blended with the fluoropolymer electrolyte.
A second aspect of the invention relates to a high-durability polymer electrolyte composite including a polymer electrolyte and at least one of a metal deactivator, a phenol compound, an amine compound and a sulfur compound.
A third aspect of the invention relates to a fuel cell electrode composed of a proton exchange material and an electric conductor carrying a catalyst. In this fuel cell electrode, a high-durability polymer electrolyte in which a functional group containing phosphorus has been introduced into a polymer electrolyte or a high-durability polymer electrolyte composite including a polymer electrolyte and an antioxidant is employed as the proton exchange material.
Thus, even in the case where a hydrogen peroxide radical is generated at a high temperature, the radical can be enhanced effectively. As a result, durability of the polymer electrolyte is enhanced. Especially, when the polymer electrolyte is a fluoropolymer having a high hydrophobic potion, by suitably combining a fluoropolymer with a functional group containing phosphorus or suitably combining a fluoropolymer with an antioxidant, separation of micro phases between materials (the fluoropolymer and the functional group containing phosphorus or the antioxidant) is promoted. Due to promotion of separation of the micro phases, the difference in density between a region exhibiting high molecular-density and a region exhibiting low molecular-density is increased. Then, the region exhibiting low molecular-density increases in porosity. Therefore, the proton exchange material is prevented from covering the catalyst in the electrode.
Accordingly, the performance of the fuel cell can be maintained.
A fourth aspect of the invention relates to a fuel cell comprising the fuel cell electrode in accordance with the aforementioned third aspect of the invention.
To be more specific, this fuel cell is obtained by bringing an electrode catalyst layer as a laminated layer of catalyst-carrying bodies into close contact with a polymer electrolyte membrane that is selectively pervious to protons (hydrogen ions), and by sandwiching two electrode catalyst layers, between which are sandwiched the polymer electrolyte membrane, between a pair of gas-diffusible electrodes.
g A polymer electrolyte of the invention is obtained by introducing an electrolyte functional group such as a sulfonic acid group, a carboxylic acid group or the like into a polymer compound. In general, a functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus. However, the "functional group containing phosphorus" as mentioned in the description of the invention includes both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus. The compound containing alkyl phosphonic acid of the invention includes an alkyl phosphonic acid and an alkyl phosphite.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
Fig. 1 is a graph illustrating the behavior of generation of S02 in a fuel cell electrode;
Fig. 2 is a graph illustrating the behavior of generation of fluorocarbon in the fuel cell electrode;
Fig. 3 is a graph illustrating initial I-V properties of a fuel cell; and Fig. 4 is a graph illustrating changes in gas leak amount observed during an acceleration durability test of the fuel cell.
DETAILED DESCRIPTION OF THE PREFERRED E1~ODIMENTS
Embodiments of the invention will be described hereinafter in detail.
A fluoropolymer electrolyte of the embodiments of the invention is a polymer into which an electrolyte functional group such as a sulfonic acid group or the like has been introduced as a substituent into a fluorocarbon skeleton or a hydrofluorocarbon skeleton. A
molecule of this fluoropolymer electrolyte may contain an ether group, chlorine, a carboxylic acid group, a phosphoric acid group, or an aromatic ring. In general, there is employed a polymer whose main chain skeleton consists of perfluoro carbon as a fluoropolymer electrolyte and which contains a sulfonic acid group via a spacer such as perfluoro ether, an aromatic ring or the like. As a concrete example thereof, a polymer having a structure expressed by a formula (1) or (2) can be mentioned.
(CFZi F)m (CF2CF2)n (1) (OCFZCF)x 0 (CFZ)y 503H
(It is to be noted in the above formula that "x"
represents an integer from 0 to 2, that "y" represents an integer 2 or 3, and that "n/m" ranges from 1 to 10.) (CF2CF)m (CF2CF)n (2) (It is to be noted in the above formula that "n/m" ranges from 0.1 to 2.) As polymers expressed by the formula (1), "Nafion~"
manufactured by Du Pont Co., Ltd., "Asiplex-S~"
manufactured by Asahi Kasei Corporation, and the like are known. Japanese Patent Publication No. 8-512358 discloses that a polymer expressed by the formula (2) is used for a fuel cell. Among these polymers, a perfluoro polymer as expressed by the formula (1) is well suited to be employed in the invention because of its excellent stability during use in a fuel cell.
A functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus.
However, the "functional group containing phosphorus" as mentioned in the description of the invention includes both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus.
These functional groups containing phosphorus can be expressed by general formulas shown below, namely, a formula (3) (a functional group containing trivalent phosphorus) and a formula (4) (a functional group containing pentavalent phosphorus).
0y Rz Rl OX P (3) \ OZ R3 Oy Rz Rl Ox P ~
" " " " " ,.
In the formulas (3) and (4), x , y and z assume either 0 or 1. In the formulas ( 3 ) and ( 4 ) , "R1", "R2"
and "R3" represent a hydrocarbon compound expressed by a general formula CmHn, a halogen atom, or a hydrogen atom.
The hydrocarbon compound may have a straight chain structure, a cyclic structure, or a branch structure.
The halogen may be fluorine, chlorine, bromine or the like. Furthermore, if "y" or "z" assumes 1 in the formulas (3) and (4), "R2" or "R3" may be a metal atom.
As concrete examples of the functional group containing phosphorus, a phosphoric acid group (OP03H2), a phosphoric acid ester group, a phosphite group (P03H2) and the like can be mentioned. Above all, a phosphoric acid group is inexpensive and capable of giving high oxidation resistance to a fluoropolymer electrolyte, and therefore is particularly preferred as a functional group containing phosphorus.
It is appropriate that only functional group containing phosphorus be introduced into the fluoropolymer electrolyte as an electrolyte functional group. Alternatively, it is also appropriate that a functional group containing phosphorus as well as other electrolyte functional groups such as a sulfonic acid group, a carboxylic acid group and the like be introduced into the fluoropolymer electrolyte. The types of other electrolyte functional groups to be introduced and the introduction ratio between the functional group containing phosphorus and the other electrolyte functional groups may be adjusted in accordance with properties required of the polymer electrolyte, namely, electrical conductivity, oxidation resistance and the like.
That is, oxidation resistance improves as the amount of introduction of the functional group containing phosphorus increases. In general, however, a functional group containing phosphorus has a low acidity.
Therefore, the electrical conductivity of a material as a whole decreases as the amount of introduction of the functional group containing phosphorus increases.
Accordingly, for uses which attribute importance only to oxidation resistance and which do not require high electrical conductivity, it is appropriate that a large amount of a functional group containing phosphorus be introduced into a fluoropolymer electrolyte.
On the other hand, if high electrical conductivity as well as high oxidation resistance is required as in the case of fuel cells or water electrolysis, it is appropriate that both a functional group containing phosphorus and a strong acid group such as a sulfonic acid group or the like be introduced at a predetermined ratio. Furthermore, if high durability against chlorine, high temperatures, or high-concentration aqueous sodium hydroxide is required while back-diffusion of ions needs to be prevented as in the case of salt electrolysis, it is appropriate that a sulfonic acid group and a carboxylic acid group as well as a functional group containing phosphorus be introduced at a predetermined ratio.
However, if the amount of introduction of the functional group containing phosphorus becomes less than 0.1 mol% of the entire electrolyte functional group, the effect of enhancing oxidation resistance becomes insufficient. Thus, it is required that the amount of introduction of the functional group containing phosphorus be equal to or more than 0.1 mol% of the entire electrolyte functional group and be equal to or less than 100 mol% of the entire electrolyte functional group. Especially in the case of polymer electrolytes that are used under severe conditions, for example, for fuel cells, water electrolysis, salt electrolysis and the like, it is preferable that the amount of introduction of the functional group containing phosphorus range from 5 to 100 mol%.
In addition, a functional group containing phosphorus, namely, a phosphonic acid group or the like may be introduced into either a main chain or a side chain of a fluoropolymer electrolyte. It is also appropriate that a functional group containing phosphorus be homogeneously introduced into an entire fluoropolymer electrolyte by randomly introducing the functional group containing phosphorus into an introducible portion on a main chain or a side chain of the polymer electrolyte.
Alternatively, it is also appropriate that the functional group containing phosphorus be selectively introduced into only such a portion of the polymer electrolyte as requires oxidation resistance.
For instance, in an environment in which a radical is randomly produced in a polymer electrolyte membrane as in the case where the polymer electrolyte membrane is heated while being soaked in a peroxide solution, it is advantageous to adopt a structure in which a functional group containing phosphorus has been randomly introduced into a polymer chain.
If a functional group containing phosphorus is partially introduced, for example, within a sulfonic acid type electrolyte membrane for the purpose of enhancing oxidation resistance, it is advantageous from the standpoint of preventing a drop in electrical conductivity of the entire membrane that a phosphonic acid group, which has a low acidity and may lower electrical conductivity, be randomly introduced.
On the other hand, in an environment wherein a peroxide is produced in a catalytic layer on the surface of an electrolyte membrane and wherein the produced peroxide changes into a peroxide radical while diffusing and this peroxide radical causes a deteriorative reaction, as in the case of an electrolyte membrane for water electrolysis or a fuel cell, selective introduction of a phosphonic acid group into a surface portion of the membrane where a deteriorative reaction resulting from oxidation occurs most vigorously is considered to be advantageous in maintaining the quality of the electrolyte membrane.
As described hitherto in detail, the high-durability polymer electrolyte in accordance with the first embodiment contains a functional group containing phosphorus, namely, a phosphonic acid group or the like, as a functional group having a function of suppressing an oxidative reaction. A sheet in which the high-durability polymer electrolyte in accordance with the first embodiment and an electric conductor carrying a catalyst 5 are mixed may be used as an electrode of a fuel cell.
Next, as the antioxidant to be added to a fluoropolymer electrolyte composite in accordance with the second embodiment, wide varieties of known inhibitors for polymer compounding can be employed. For instance, a 10 metal deactivator, a phenol compound, an amine compound, a sulfur compound, a phosphorus compound and the like can be mentioned. As a concrete example of the metal deactivator, diphenyl oxamide can be mentioned.
As the phenol compound, a hindered phenol compound as 15 well as hydroquinone, p-cresol, BHT and the like can be mentioned. As concrete examples of the hindered phenol compound, 2, 6-di-tert-butyl-4-methyl phenol, 2, 2'-methylene-bis (4-methyl-6-tert-butyl phenol), 2, 2'-methylene-bis (4-ethyl-6-tert-butyl phenol), 4, 4'-thio-bis (3-methyl-6-tert-butyl phenol), 4, 4'-butylidene-bis (3-methyl-6-tent-butyl phenol), triethylene glycol-bis [3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1, 6-hexanediol-bis [3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2, 2-thio-diethylene-bis [3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3-[3, 5-di-tert-butyl-4-hydroxyphenyl]
propionate, 3, 5-di-ter-butyl-4-hydroxybenzyl phosphonate-diethyl ester, 1, 3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl benzene), iso-octyl-3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, and the like can be mentioned.
As concrete examples of the amine compound, phenyl-2-naphthylamine, phenothiazine, diphenyl phenylenediamine, naphthylamine, diphenyl amine containing octyl gruop (4, 4'-dioctyl-diphenylamine), 4, 4'-dicumyl-diphenyl amine, 6-ethoxy-2, 2, 4-trimethyl-l, 2-dihydroquinoline, 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymer, and the like can be mentioned.
As concrete examples of the sulfur compound, 2-mercaptobenzimidazole, 2, 4-bas [(octylthio) methyl]-o-cresol, 2, 4-bas-(n-octylthio)-6-(4-hydroxy-3, 5-di-tert-butyl anilino)-1, 3, 5-triazine adk stab~ AO-4125 (manufactured by Asahi Denka Co., Ltd.), and the like can be mentioned.
A concrete example of the phosphorus compound may be selected from a group consisting of triethyl phosphate, triethyl phosphate, triphenyl phosphine, triphenyl phosphine oxide, triphenyl phosphine sulfide, distearyl pentaerythrithyl diphosphite, organic phosphate, diphenyl isodecyl phosphate, diphenyl isooctyl phosphate, diisodecyl phenyl phosphate, triphenyl phosphate, and trisnonyl phenyl phosphate. Furthermore, it is preferable that a concrete example of the phosphorus compound be selected from a group consisting of conjugated organic phosphate, polyphosphate, and tetrapentaerythritol. Also, adk stab~ PER-4C
(manufactured by Asahi Denka Co., Ltd.), adk stab~ 260 (manufactured by Asahi Denka Co., Ltd.), adk stab~ 522A
(manufactured by Asahi Denka Co., Ltd.) and the like can also be mentioned.
Among phosphorus compounds, phosphorus compounds containing alkyl phosphonic acid are preferred in particular. As concrete examples thereof, it is preferable to mention polyvinyl phosphonic acid, xylidyl phosphonic acid, and benzyl phosphonic acid.
One or two or more of these antioxidants can be used.
A polymer electrolyte composite normally contains 0.005 to 10 wt.% of the antioxidant and preferably 0.01 to 5 wt.% of the antioxidant.
A compound containing phosphorus means a substance having a functional group containing phosphorus. Both a compound having a functional group containing phosphorus and a polymer compound whose main chain or side chain has a functional group containing phosphorus can be regarded as a compound containing phosphorus. A functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus. However, both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus are regarded as the "functional group containing phosphorus"
mentioned in the description of this embodiment. These functional groups containing phosphorus can be expressed by general formulas such as the aforementioned ones (3) (a functional group containing trivalent phosphorus) and (4) (a functional group containing pentavalent phosphorus).
As concrete examples of the functional group containing phosphorus, a phosphonic acid group, a phosphonic acid ester group, a phosphite group, phosphoric acid group, phosphoric ester group and the like can be mentioned. Above all, a nhosnhonic acid group is inexpensive and capable of giving high oxidation resistance to a polymer compound having a hydrocarbon portion, and therefore is particularly preferred as a functional group containing phosphorus.
As concrete examples of the polymer containing phosphorus, polyvinyl phosphonic acid, polyether sulfone ,1g resin into which at least phosphonic acid group has been introduced as a functional group, polyether ether ketone resin, straight-chain phenol-formaldehyde resin, cross-linked phenol-formaldehyde resin, straight-chain polystyrene resin, cross-linked polystyrene resin, straight-chain poly (trifluorostyrene) resin, cross-linked (trifluorostyrene) resin, poly (2, 3-diphenyl-l, 4-phenylene oxide) resin, poly (allyl ether ketone) resin, poly (allylene ether sulfone) resin, poly (phenyl quinoxaline) resin, poly (benzyl silane) resin, polystyrene-graft-ethylene-tetrafluoroethylene resin, polystyrene-graft-polyvinylidene fluoride resin, polystyrene-graft-tetrafluoroethylene resin, and the like can be mentioned. In addition, polyimidazole containing phosphonic acid (disclosed in Japanese Patent Application Laid-Open No. 2002-212291), polyacrylophosphonic acid (disclosed in Japanese Patent Application Laid-Open No.
2002-012598), phosphonic acid oligomer containing a fluoroalkyl group (disclosed in Japanese Patent Application Laid-Open No. 2001-253921), and the like can also be mentioned.
No restriction is imposed on a manner in which a fluoropolymer electrolyte and an oxidation stabilizer are mixed with each other. Namely, it is possible to employ various methods. For instance, they may be doped or blended with each other using a solution. In the case where both a fluoropolymer electrolyte and an oxidation stabilizer are thermally fusible, they may be blended with each other through hot melting.
A structure in which an oxidation stabilizer is homogeneously dispersed in an entire polymer electrolyte may be realized by homogeneously mixing an oxidation stabilizer with a fluoropolymer electrolyte.
Alternatively, it is also appropriate that a main portion of a polymer electrolyte be constituted exclusively by a fluoropolymer electrolyte, and that only such a portion of the polymer electrolyte as requires oxidation resistance be constituted by the mixture of the fluoropolymer electrolyte and an oxidation stabilizer.
For instance, in an environment in which a radical is randomly produced in a membrane as in the case where a polymer electrolyte membrane is heated while being soaked in a peroxide solution, it is advantageous to adopt a structure in which an oxidation stabilizer is homogeneously mixed with a fluoropolymer electrolyte and is thereby homogeneously dispersed in an entire polymer electrolyte membrane.
On the other hand, in an environment wherein a peroxide is produced in a catalytic layer on the surface of a membrane and wherein the produced peroxide changes into a peroxide radical while diffusing and this peroxide radical causes a deteriorative reaction, as in the case of an electrolyte membrane for water electrolysis or fuel cells, it is not required that an oxidation stabilizer be homogeneously dispersed in the membrane. In this case, it is appropriate that only a surface portion of the membrane where a deteriorative reaction resulting from oxidation occurs most vigorously be constituted by the mixture of the oxidation stabilizer and a fluoropolymer electrolyte by doping the latter with the former.
Alternatively, a method of inserting a membranous molded material consisting of the mixture of a fluoropolymer electrolyte and an oxidation stabilizer into a space between an electrode and an electrolyte consisting only of the fluoropolymer electrolyte is also considered effective in maintaining the quality of an electrolyte membrane.
The type and amount of an electrolyte functional group to be introduced into a fluoropolymer electrolyte or the 5 mixing ratio between a compound containing phosphorus and a fluoropolymer electrolyte membrane may be adjusted in accordance with properties required of the polymer electrolyte, namely, electrical conductivity, oxidation resistance, and the like.
10 That is, oxidation resistance is enhanced as the amount of an oxidation stabilizer to be blended increases. However, since many oxidation stabilizers are low-acidity groups, electrical conductivity of the entire material decreases as the amount to be blended increases.
15 Accordingly, for uses which attribute importance only to oxidation resistance and which do not require high electrical conductivity, it is appropriate that the mixing ratio of an oxidation stabilizer to a polymer compound having a fluoropolymer electrolyte be increased.
20 On the other hand, if high electrical conductivity as well as high oxidation resistance is required as in the case of fuel cells or water electrolysis, it is appropriate that an oxidation stabilizer and a fluoropolymer electrolyte into which a strong acid group such as a sulfonic acid group or the like has been introduced be mixed with each other at a predetermined ratio. Further, if durability against chlorine, high temperatures, and high-concentration aqueous sodium hydroxide is required while back-diffusion of ions needs to be prevented as in the case of salt electrolysis, it is appropriate that an oxidation stabilizer and a fluoropolymer electrolyte within which a sulfonic acid group, a carboxylic acid group and the like are e21 introduced be mixed with each other at a predetermined ratio.
However, if the amount of the oxidation stabilizer to be blended becomes less than 0.1 mol% of the entire electrolyte functional group, the effect of enhancing oxidation resistance becomes insufficient. Thus, it is required that the amount of the oxidation stabilizer to be blended be equal to or more than 0.1 mol% of the entire electrolyte functional group. Especially in the case of polymer electrolytes that are used under severe conditions, for example, for fuel cells, water electrolysis, salt electrolysis and the like, it is preferable that the amount of a compound containing phosphorus range from 5 to 100 mol%.
As described hitherto in detail, the high-durability polymer electrolyte composite in accordance with the second embodiment is obtained by mixing a fluoropolymer electrolyte with an oxidation stabilizer such as a phosphonic acid group having a function of suppressing an oxidative reaction.
Hereinafter, the embodiments of the invention will be described in fuller detail with reference to examples and comparative examples.
(1) Preparation of Fuel Cell Electrode to which Polyvinyl Phosphonic Acid Is Added [Comparative Example) A homogeneous dispersive solution was prepared by adding 3.3m1 of an electrolytic solution (a commercial solution containing 5% of Nafion~) and a predetermined amount of water to 1100mg of carbon carrying 60% of platinum and stirring them. The dispersive solution was cast on a fluororesin sheet using a doctor blade. This sheet was dried under a reduced pressure for 8 hours at a temperature of 80°C, whereby a fuel cell electrode sheet was obtained.
This is a normally employed fuel cell electrode (obtained by drying and solidifying a Nafion~ dispersive solution of carbon carrying platinum). It is to be noted herein that Pt . C . Nafion~ - 60 . 40 . 28.
[Example]
When preparing the dispersive solution of the aforementioned comparative example, 160mg of polyvinyl phosphonic acid (manufactured by General Science Co., Ltd.) was added, whereby an antioxidant-added electrode sheet was obtained.
This is obtained by adding polyvinyl phosphonic acid (PVPA) to the electrode of the aforementioned comparative example. It is to be noted herein that Pt . C .
Nafion~ . PVPA = 60 . 40 . 28 . 14.
(2) Analysis of Dispersion Behavior by TG-MS
Amounts of gas generated form the antioxidant-added electrode sheets at respective temperatures were measured by means of TG-MS so as to investigate an effect exerted upon pyrolysis by addition of polyvinyl phosphonic acid (PVPA) while temperature of atmosphere rose at a rate of 10°C/min was observed in the atmosphere of He. Among substances generated in this analysis, the behavior of generation of S02 (Fig. 1) and fluorocarbon (Fig. 2) as a component obtained by decomposing Nafion~ are illustrated.
S02 generated in a temperature range indicated by "X"
in Fig. 1 is obtained through oxidation of sulfur adsorbed on carbon by oxygen adsorbed on carbon. The S02 thus generated has nothing to do with decomposition of Nafion~. The amount of S02 generated through decomposition of Nafion~ increases at or above a temperature of 200°C. However, the amount of S02 produced in this example is much smaller than the amount of S02 produced in the comparative example.
Referring to Fig. 2, generation of CF3+ and C2F5+ was observed in a temperature range at or above 250°C in the comparative example. This generation of CF3+ and C2F5+
results from decomposition of Nafion~. On the other hand, in the example, generation of C2F5+ was not observed, and only generation of CF3+ was observed. Also, the amount of CF3+ in the example is smaller than the amount of CF3+ in the comparative example.
The aforementioned result of analysis has revealed that addition of polyvinyl phosphoric acid (PVPA) substantially improves stability in thermal decomposition of Nafion~ in the electrode. Although this mechanism of suppressing decomposition is not quite obvious, it is inferable that a chain reaction of decomposition may have been stopped by stabilizing a carbon radical after detachment of a sulfonic acid group.
(3) Evaluation of Variation in Stability with Time Based on Evaluation of Battery [Initial Properties) Fig. 3 illustrates a result of an I-V evaluation (current-voltage evaluation) which was performed under the conditions of cell: 80°C, A bubbler (anode): H2, 275cc/min, C bubbler (cathode): Air, 912cc/min, and both electrodes: 2ata.
Referring to Fig. 3, although polyvinyl phosphoric acid (PVPA) was added in the example, the gradient of the example is substantially equal to the gradient of the comparative example. Also, the example and the comparative example are substantially identical in contact resistance between the membrane and the electrode. Further, the example and the comparative example are also substantially identical in limiting current value and drainage properties of the electrode.
In general, the fact that the limiting current remains substantially unchanged despite an increase in weight corresponding to a multiplier of 1.5 and an increase in volume corresponding to a multiplier of about 2 because of addition of polyvinyl phosphoric acid (PVPA) demonstrates that addition of polyvinyl phosphoric acid (PVPA) does not deteriorate drainage properties. In addition, referring to Fig. 3, the voltage is lower in the example than in the comparative example on the whole.
This is considered to result from catalytic activity.
However, the voltage can be adjusted by reducing an amount of polyvinyl phosphoric acid (PVPA) to be added.
The aforementioned result of the evaluation has revealed that addition of polyvinyl phosphoric acid (PVPA) causes no change in fuel cell properties, especially, no change in resistance or limiting current value.
[Gas Leakage Amount in Acceleration Durability Test]
Continuous operation was performed under conditions of cell: 80°C, A: humidified H2 gas, and C: humidified air, and under load conditions including a condition of an open circuit. The result is illustrated in Fig. 4.
Referring to Fig. 4, while the gas leakage amount starts increasing at an early stage in the comparative example, the gas leakage amount remains small in the example even after the lapse of 250 hours. Although it is intrinsically in the electrolyte of the electrode that an antioxidant effect based on addition of polyvinyl phosphoric acid (PVPA) is expected, the result illustrated in Fig. 4 reveals that the electrolyte membrane is also inhibited from deteriorating. Although the cause for this phenomenon has not been elucidated in detail, it is inferable that a peroxide radical generated 5 in the electrode or a decompositional radical may have been deactivated by the antioxidant and that diffusion of the radical into the electrolyte membrane may have been suppressed as a result.
By introducing a functional group containing 10 phosphorus into a fluoropolymer electrolyte or combining a fluoropolymer electrolyte with an antioxidant, it becomes possible to suppress generation of a hydrogen peroxide radical even in the case where the radical is generated at a high temperature. As a result, durability 15 of the fluoropolymer electrolyte is enhanced. Also, since separation of micro phases between hydrophilic portions of the fluoropolymer and the antioxidant and hydrophobic portions of the fluoropolymer and the antioxidant leads to an increase in porosity, a proton 20 exchange material is prevented from covering the catalyst in the electrode. Accordingly, the performance of the fuel cell can be maintained.
However, if a hydrocarbon-type electrolyte is used in a fuel cell, use of the high-durability polymer electrolyte and the high-durability polymer electrolyte composite disclosed in the aforementioned patent publications, namely, Japanese Patent Application Laid-Open No. 2000-11755 and Japanese Patent Application Laid-Open No. 2000-11756 as a material for electrodes (anode and cathode) substantially prevents a fuel gas (hydrogen or the like) or an oxidative gas (oxygen, air or the like) from contacting a catalyst (platinum or the like), because the high-durability polymer electrolyte and the high-durability polymer electrolyte composite basically tend to shut gas off. As a result, the performance of the fuel cell deteriorates substantially. As described hitherto, the idea of combining a hydrocarbon-type electrolyte with a functional group containing phosphorus or a compound containing phosphorus brings about a problem.
SUI~1ARY OF THE INVENTION
It is an object of the invention to drastically enhance durability of a polymer electrolyte employed for 5 a fuel cell or the like.
As a result of exhaustive studies, the inventors have come up with a method of more drastically enhancing oxidation stability of a fluoropolymer electrolyte which is chemically highly stable in itself, and have attained the invention.
A first aspect of the invention relates to a high-durability polymer electrolyte composite including a polymer electrolyte and a compound containing alkyl phosphonic acid. As the polymer electrolyte, a polymer electrolyte having no C-F bonding or a fluoropolymer (especially a fluoropolymer having no C-H bonding) can be mentioned.
Fluoropolymers are chemically stable in itself, because bonding between carbon and fluorine are strongly bonded together. It was usually considered unrealistic to take measures to stabilize fluoropolymers. However, according to the knowledge acquired by the inventors, the following phenomenon occurs even in the case of fluoropolymers. That is, if a hydrogen peroxide radical or the like is generated in a fluoropolymer, the fluoropolymer is sequentially decomposed step by step into units of ether containing fluorine on a side chain.
Once a process of decomposition begins, a large amount of heat is generated because binding energy between atoms is at a high level. As a result, thermal decomposition progresses quickly.
In the invention, the compound containing alkyl phosphonic acid is blended with the fluoropolymer electrolyte, whereby the compound containing alkyl phosphonic acid quenches not only a hydrogen peroxide radical generated in the fluoropolymer electrolyte but also a decompositional radical produced during decomposition of the fluoropolymer electrolyte. Thus, oxidation stability of the fluoropolymer electrolyte is significantly enhanced. Even in the case where the compound containing alkyl phosphonic acid has been blended with a polymer electrolyte having no C-F bonding, a hydrogen peroxide radical generated in the polymer electrolyte and a decompositional radical produced during a process of decomposing the polymer electrolyte are quenched by the compound containing alkyl phosphonic acid. C-H bonding is chemically less stable than C-F
bonding and thus is apt to be attacked by radicals.
Therefore, blend of the compound containing alkyl phosphonic acid with the polymer electrolyte having no C-F bonding is effective in enhancing durability of the polymer electrolyte.
A low-molecular compound, oligomer, or a polymer is employed as the compound containing alkyl phosphonic acid to be blended with the fluoropolymer electrolyte.
A second aspect of the invention relates to a high-durability polymer electrolyte composite including a polymer electrolyte and at least one of a metal deactivator, a phenol compound, an amine compound and a sulfur compound.
A third aspect of the invention relates to a fuel cell electrode composed of a proton exchange material and an electric conductor carrying a catalyst. In this fuel cell electrode, a high-durability polymer electrolyte in which a functional group containing phosphorus has been introduced into a polymer electrolyte or a high-durability polymer electrolyte composite including a polymer electrolyte and an antioxidant is employed as the proton exchange material.
Thus, even in the case where a hydrogen peroxide radical is generated at a high temperature, the radical can be enhanced effectively. As a result, durability of the polymer electrolyte is enhanced. Especially, when the polymer electrolyte is a fluoropolymer having a high hydrophobic potion, by suitably combining a fluoropolymer with a functional group containing phosphorus or suitably combining a fluoropolymer with an antioxidant, separation of micro phases between materials (the fluoropolymer and the functional group containing phosphorus or the antioxidant) is promoted. Due to promotion of separation of the micro phases, the difference in density between a region exhibiting high molecular-density and a region exhibiting low molecular-density is increased. Then, the region exhibiting low molecular-density increases in porosity. Therefore, the proton exchange material is prevented from covering the catalyst in the electrode.
Accordingly, the performance of the fuel cell can be maintained.
A fourth aspect of the invention relates to a fuel cell comprising the fuel cell electrode in accordance with the aforementioned third aspect of the invention.
To be more specific, this fuel cell is obtained by bringing an electrode catalyst layer as a laminated layer of catalyst-carrying bodies into close contact with a polymer electrolyte membrane that is selectively pervious to protons (hydrogen ions), and by sandwiching two electrode catalyst layers, between which are sandwiched the polymer electrolyte membrane, between a pair of gas-diffusible electrodes.
g A polymer electrolyte of the invention is obtained by introducing an electrolyte functional group such as a sulfonic acid group, a carboxylic acid group or the like into a polymer compound. In general, a functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus. However, the "functional group containing phosphorus" as mentioned in the description of the invention includes both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus. The compound containing alkyl phosphonic acid of the invention includes an alkyl phosphonic acid and an alkyl phosphite.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
Fig. 1 is a graph illustrating the behavior of generation of S02 in a fuel cell electrode;
Fig. 2 is a graph illustrating the behavior of generation of fluorocarbon in the fuel cell electrode;
Fig. 3 is a graph illustrating initial I-V properties of a fuel cell; and Fig. 4 is a graph illustrating changes in gas leak amount observed during an acceleration durability test of the fuel cell.
DETAILED DESCRIPTION OF THE PREFERRED E1~ODIMENTS
Embodiments of the invention will be described hereinafter in detail.
A fluoropolymer electrolyte of the embodiments of the invention is a polymer into which an electrolyte functional group such as a sulfonic acid group or the like has been introduced as a substituent into a fluorocarbon skeleton or a hydrofluorocarbon skeleton. A
molecule of this fluoropolymer electrolyte may contain an ether group, chlorine, a carboxylic acid group, a phosphoric acid group, or an aromatic ring. In general, there is employed a polymer whose main chain skeleton consists of perfluoro carbon as a fluoropolymer electrolyte and which contains a sulfonic acid group via a spacer such as perfluoro ether, an aromatic ring or the like. As a concrete example thereof, a polymer having a structure expressed by a formula (1) or (2) can be mentioned.
(CFZi F)m (CF2CF2)n (1) (OCFZCF)x 0 (CFZ)y 503H
(It is to be noted in the above formula that "x"
represents an integer from 0 to 2, that "y" represents an integer 2 or 3, and that "n/m" ranges from 1 to 10.) (CF2CF)m (CF2CF)n (2) (It is to be noted in the above formula that "n/m" ranges from 0.1 to 2.) As polymers expressed by the formula (1), "Nafion~"
manufactured by Du Pont Co., Ltd., "Asiplex-S~"
manufactured by Asahi Kasei Corporation, and the like are known. Japanese Patent Publication No. 8-512358 discloses that a polymer expressed by the formula (2) is used for a fuel cell. Among these polymers, a perfluoro polymer as expressed by the formula (1) is well suited to be employed in the invention because of its excellent stability during use in a fuel cell.
A functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus.
However, the "functional group containing phosphorus" as mentioned in the description of the invention includes both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus.
These functional groups containing phosphorus can be expressed by general formulas shown below, namely, a formula (3) (a functional group containing trivalent phosphorus) and a formula (4) (a functional group containing pentavalent phosphorus).
0y Rz Rl OX P (3) \ OZ R3 Oy Rz Rl Ox P ~
" " " " " ,.
In the formulas (3) and (4), x , y and z assume either 0 or 1. In the formulas ( 3 ) and ( 4 ) , "R1", "R2"
and "R3" represent a hydrocarbon compound expressed by a general formula CmHn, a halogen atom, or a hydrogen atom.
The hydrocarbon compound may have a straight chain structure, a cyclic structure, or a branch structure.
The halogen may be fluorine, chlorine, bromine or the like. Furthermore, if "y" or "z" assumes 1 in the formulas (3) and (4), "R2" or "R3" may be a metal atom.
As concrete examples of the functional group containing phosphorus, a phosphoric acid group (OP03H2), a phosphoric acid ester group, a phosphite group (P03H2) and the like can be mentioned. Above all, a phosphoric acid group is inexpensive and capable of giving high oxidation resistance to a fluoropolymer electrolyte, and therefore is particularly preferred as a functional group containing phosphorus.
It is appropriate that only functional group containing phosphorus be introduced into the fluoropolymer electrolyte as an electrolyte functional group. Alternatively, it is also appropriate that a functional group containing phosphorus as well as other electrolyte functional groups such as a sulfonic acid group, a carboxylic acid group and the like be introduced into the fluoropolymer electrolyte. The types of other electrolyte functional groups to be introduced and the introduction ratio between the functional group containing phosphorus and the other electrolyte functional groups may be adjusted in accordance with properties required of the polymer electrolyte, namely, electrical conductivity, oxidation resistance and the like.
That is, oxidation resistance improves as the amount of introduction of the functional group containing phosphorus increases. In general, however, a functional group containing phosphorus has a low acidity.
Therefore, the electrical conductivity of a material as a whole decreases as the amount of introduction of the functional group containing phosphorus increases.
Accordingly, for uses which attribute importance only to oxidation resistance and which do not require high electrical conductivity, it is appropriate that a large amount of a functional group containing phosphorus be introduced into a fluoropolymer electrolyte.
On the other hand, if high electrical conductivity as well as high oxidation resistance is required as in the case of fuel cells or water electrolysis, it is appropriate that both a functional group containing phosphorus and a strong acid group such as a sulfonic acid group or the like be introduced at a predetermined ratio. Furthermore, if high durability against chlorine, high temperatures, or high-concentration aqueous sodium hydroxide is required while back-diffusion of ions needs to be prevented as in the case of salt electrolysis, it is appropriate that a sulfonic acid group and a carboxylic acid group as well as a functional group containing phosphorus be introduced at a predetermined ratio.
However, if the amount of introduction of the functional group containing phosphorus becomes less than 0.1 mol% of the entire electrolyte functional group, the effect of enhancing oxidation resistance becomes insufficient. Thus, it is required that the amount of introduction of the functional group containing phosphorus be equal to or more than 0.1 mol% of the entire electrolyte functional group and be equal to or less than 100 mol% of the entire electrolyte functional group. Especially in the case of polymer electrolytes that are used under severe conditions, for example, for fuel cells, water electrolysis, salt electrolysis and the like, it is preferable that the amount of introduction of the functional group containing phosphorus range from 5 to 100 mol%.
In addition, a functional group containing phosphorus, namely, a phosphonic acid group or the like may be introduced into either a main chain or a side chain of a fluoropolymer electrolyte. It is also appropriate that a functional group containing phosphorus be homogeneously introduced into an entire fluoropolymer electrolyte by randomly introducing the functional group containing phosphorus into an introducible portion on a main chain or a side chain of the polymer electrolyte.
Alternatively, it is also appropriate that the functional group containing phosphorus be selectively introduced into only such a portion of the polymer electrolyte as requires oxidation resistance.
For instance, in an environment in which a radical is randomly produced in a polymer electrolyte membrane as in the case where the polymer electrolyte membrane is heated while being soaked in a peroxide solution, it is advantageous to adopt a structure in which a functional group containing phosphorus has been randomly introduced into a polymer chain.
If a functional group containing phosphorus is partially introduced, for example, within a sulfonic acid type electrolyte membrane for the purpose of enhancing oxidation resistance, it is advantageous from the standpoint of preventing a drop in electrical conductivity of the entire membrane that a phosphonic acid group, which has a low acidity and may lower electrical conductivity, be randomly introduced.
On the other hand, in an environment wherein a peroxide is produced in a catalytic layer on the surface of an electrolyte membrane and wherein the produced peroxide changes into a peroxide radical while diffusing and this peroxide radical causes a deteriorative reaction, as in the case of an electrolyte membrane for water electrolysis or a fuel cell, selective introduction of a phosphonic acid group into a surface portion of the membrane where a deteriorative reaction resulting from oxidation occurs most vigorously is considered to be advantageous in maintaining the quality of the electrolyte membrane.
As described hitherto in detail, the high-durability polymer electrolyte in accordance with the first embodiment contains a functional group containing phosphorus, namely, a phosphonic acid group or the like, as a functional group having a function of suppressing an oxidative reaction. A sheet in which the high-durability polymer electrolyte in accordance with the first embodiment and an electric conductor carrying a catalyst 5 are mixed may be used as an electrode of a fuel cell.
Next, as the antioxidant to be added to a fluoropolymer electrolyte composite in accordance with the second embodiment, wide varieties of known inhibitors for polymer compounding can be employed. For instance, a 10 metal deactivator, a phenol compound, an amine compound, a sulfur compound, a phosphorus compound and the like can be mentioned. As a concrete example of the metal deactivator, diphenyl oxamide can be mentioned.
As the phenol compound, a hindered phenol compound as 15 well as hydroquinone, p-cresol, BHT and the like can be mentioned. As concrete examples of the hindered phenol compound, 2, 6-di-tert-butyl-4-methyl phenol, 2, 2'-methylene-bis (4-methyl-6-tert-butyl phenol), 2, 2'-methylene-bis (4-ethyl-6-tert-butyl phenol), 4, 4'-thio-bis (3-methyl-6-tert-butyl phenol), 4, 4'-butylidene-bis (3-methyl-6-tent-butyl phenol), triethylene glycol-bis [3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1, 6-hexanediol-bis [3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2, 2-thio-diethylene-bis [3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3-[3, 5-di-tert-butyl-4-hydroxyphenyl]
propionate, 3, 5-di-ter-butyl-4-hydroxybenzyl phosphonate-diethyl ester, 1, 3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl benzene), iso-octyl-3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, and the like can be mentioned.
As concrete examples of the amine compound, phenyl-2-naphthylamine, phenothiazine, diphenyl phenylenediamine, naphthylamine, diphenyl amine containing octyl gruop (4, 4'-dioctyl-diphenylamine), 4, 4'-dicumyl-diphenyl amine, 6-ethoxy-2, 2, 4-trimethyl-l, 2-dihydroquinoline, 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymer, and the like can be mentioned.
As concrete examples of the sulfur compound, 2-mercaptobenzimidazole, 2, 4-bas [(octylthio) methyl]-o-cresol, 2, 4-bas-(n-octylthio)-6-(4-hydroxy-3, 5-di-tert-butyl anilino)-1, 3, 5-triazine adk stab~ AO-4125 (manufactured by Asahi Denka Co., Ltd.), and the like can be mentioned.
A concrete example of the phosphorus compound may be selected from a group consisting of triethyl phosphate, triethyl phosphate, triphenyl phosphine, triphenyl phosphine oxide, triphenyl phosphine sulfide, distearyl pentaerythrithyl diphosphite, organic phosphate, diphenyl isodecyl phosphate, diphenyl isooctyl phosphate, diisodecyl phenyl phosphate, triphenyl phosphate, and trisnonyl phenyl phosphate. Furthermore, it is preferable that a concrete example of the phosphorus compound be selected from a group consisting of conjugated organic phosphate, polyphosphate, and tetrapentaerythritol. Also, adk stab~ PER-4C
(manufactured by Asahi Denka Co., Ltd.), adk stab~ 260 (manufactured by Asahi Denka Co., Ltd.), adk stab~ 522A
(manufactured by Asahi Denka Co., Ltd.) and the like can also be mentioned.
Among phosphorus compounds, phosphorus compounds containing alkyl phosphonic acid are preferred in particular. As concrete examples thereof, it is preferable to mention polyvinyl phosphonic acid, xylidyl phosphonic acid, and benzyl phosphonic acid.
One or two or more of these antioxidants can be used.
A polymer electrolyte composite normally contains 0.005 to 10 wt.% of the antioxidant and preferably 0.01 to 5 wt.% of the antioxidant.
A compound containing phosphorus means a substance having a functional group containing phosphorus. Both a compound having a functional group containing phosphorus and a polymer compound whose main chain or side chain has a functional group containing phosphorus can be regarded as a compound containing phosphorus. A functional group containing phosphorus may be either a functional group containing trivalent phosphorus or a functional group containing pentavalent phosphorus. However, both a functional group containing trivalent phosphorus and a functional group containing pentavalent phosphorus are regarded as the "functional group containing phosphorus"
mentioned in the description of this embodiment. These functional groups containing phosphorus can be expressed by general formulas such as the aforementioned ones (3) (a functional group containing trivalent phosphorus) and (4) (a functional group containing pentavalent phosphorus).
As concrete examples of the functional group containing phosphorus, a phosphonic acid group, a phosphonic acid ester group, a phosphite group, phosphoric acid group, phosphoric ester group and the like can be mentioned. Above all, a nhosnhonic acid group is inexpensive and capable of giving high oxidation resistance to a polymer compound having a hydrocarbon portion, and therefore is particularly preferred as a functional group containing phosphorus.
As concrete examples of the polymer containing phosphorus, polyvinyl phosphonic acid, polyether sulfone ,1g resin into which at least phosphonic acid group has been introduced as a functional group, polyether ether ketone resin, straight-chain phenol-formaldehyde resin, cross-linked phenol-formaldehyde resin, straight-chain polystyrene resin, cross-linked polystyrene resin, straight-chain poly (trifluorostyrene) resin, cross-linked (trifluorostyrene) resin, poly (2, 3-diphenyl-l, 4-phenylene oxide) resin, poly (allyl ether ketone) resin, poly (allylene ether sulfone) resin, poly (phenyl quinoxaline) resin, poly (benzyl silane) resin, polystyrene-graft-ethylene-tetrafluoroethylene resin, polystyrene-graft-polyvinylidene fluoride resin, polystyrene-graft-tetrafluoroethylene resin, and the like can be mentioned. In addition, polyimidazole containing phosphonic acid (disclosed in Japanese Patent Application Laid-Open No. 2002-212291), polyacrylophosphonic acid (disclosed in Japanese Patent Application Laid-Open No.
2002-012598), phosphonic acid oligomer containing a fluoroalkyl group (disclosed in Japanese Patent Application Laid-Open No. 2001-253921), and the like can also be mentioned.
No restriction is imposed on a manner in which a fluoropolymer electrolyte and an oxidation stabilizer are mixed with each other. Namely, it is possible to employ various methods. For instance, they may be doped or blended with each other using a solution. In the case where both a fluoropolymer electrolyte and an oxidation stabilizer are thermally fusible, they may be blended with each other through hot melting.
A structure in which an oxidation stabilizer is homogeneously dispersed in an entire polymer electrolyte may be realized by homogeneously mixing an oxidation stabilizer with a fluoropolymer electrolyte.
Alternatively, it is also appropriate that a main portion of a polymer electrolyte be constituted exclusively by a fluoropolymer electrolyte, and that only such a portion of the polymer electrolyte as requires oxidation resistance be constituted by the mixture of the fluoropolymer electrolyte and an oxidation stabilizer.
For instance, in an environment in which a radical is randomly produced in a membrane as in the case where a polymer electrolyte membrane is heated while being soaked in a peroxide solution, it is advantageous to adopt a structure in which an oxidation stabilizer is homogeneously mixed with a fluoropolymer electrolyte and is thereby homogeneously dispersed in an entire polymer electrolyte membrane.
On the other hand, in an environment wherein a peroxide is produced in a catalytic layer on the surface of a membrane and wherein the produced peroxide changes into a peroxide radical while diffusing and this peroxide radical causes a deteriorative reaction, as in the case of an electrolyte membrane for water electrolysis or fuel cells, it is not required that an oxidation stabilizer be homogeneously dispersed in the membrane. In this case, it is appropriate that only a surface portion of the membrane where a deteriorative reaction resulting from oxidation occurs most vigorously be constituted by the mixture of the oxidation stabilizer and a fluoropolymer electrolyte by doping the latter with the former.
Alternatively, a method of inserting a membranous molded material consisting of the mixture of a fluoropolymer electrolyte and an oxidation stabilizer into a space between an electrode and an electrolyte consisting only of the fluoropolymer electrolyte is also considered effective in maintaining the quality of an electrolyte membrane.
The type and amount of an electrolyte functional group to be introduced into a fluoropolymer electrolyte or the 5 mixing ratio between a compound containing phosphorus and a fluoropolymer electrolyte membrane may be adjusted in accordance with properties required of the polymer electrolyte, namely, electrical conductivity, oxidation resistance, and the like.
10 That is, oxidation resistance is enhanced as the amount of an oxidation stabilizer to be blended increases. However, since many oxidation stabilizers are low-acidity groups, electrical conductivity of the entire material decreases as the amount to be blended increases.
15 Accordingly, for uses which attribute importance only to oxidation resistance and which do not require high electrical conductivity, it is appropriate that the mixing ratio of an oxidation stabilizer to a polymer compound having a fluoropolymer electrolyte be increased.
20 On the other hand, if high electrical conductivity as well as high oxidation resistance is required as in the case of fuel cells or water electrolysis, it is appropriate that an oxidation stabilizer and a fluoropolymer electrolyte into which a strong acid group such as a sulfonic acid group or the like has been introduced be mixed with each other at a predetermined ratio. Further, if durability against chlorine, high temperatures, and high-concentration aqueous sodium hydroxide is required while back-diffusion of ions needs to be prevented as in the case of salt electrolysis, it is appropriate that an oxidation stabilizer and a fluoropolymer electrolyte within which a sulfonic acid group, a carboxylic acid group and the like are e21 introduced be mixed with each other at a predetermined ratio.
However, if the amount of the oxidation stabilizer to be blended becomes less than 0.1 mol% of the entire electrolyte functional group, the effect of enhancing oxidation resistance becomes insufficient. Thus, it is required that the amount of the oxidation stabilizer to be blended be equal to or more than 0.1 mol% of the entire electrolyte functional group. Especially in the case of polymer electrolytes that are used under severe conditions, for example, for fuel cells, water electrolysis, salt electrolysis and the like, it is preferable that the amount of a compound containing phosphorus range from 5 to 100 mol%.
As described hitherto in detail, the high-durability polymer electrolyte composite in accordance with the second embodiment is obtained by mixing a fluoropolymer electrolyte with an oxidation stabilizer such as a phosphonic acid group having a function of suppressing an oxidative reaction.
Hereinafter, the embodiments of the invention will be described in fuller detail with reference to examples and comparative examples.
(1) Preparation of Fuel Cell Electrode to which Polyvinyl Phosphonic Acid Is Added [Comparative Example) A homogeneous dispersive solution was prepared by adding 3.3m1 of an electrolytic solution (a commercial solution containing 5% of Nafion~) and a predetermined amount of water to 1100mg of carbon carrying 60% of platinum and stirring them. The dispersive solution was cast on a fluororesin sheet using a doctor blade. This sheet was dried under a reduced pressure for 8 hours at a temperature of 80°C, whereby a fuel cell electrode sheet was obtained.
This is a normally employed fuel cell electrode (obtained by drying and solidifying a Nafion~ dispersive solution of carbon carrying platinum). It is to be noted herein that Pt . C . Nafion~ - 60 . 40 . 28.
[Example]
When preparing the dispersive solution of the aforementioned comparative example, 160mg of polyvinyl phosphonic acid (manufactured by General Science Co., Ltd.) was added, whereby an antioxidant-added electrode sheet was obtained.
This is obtained by adding polyvinyl phosphonic acid (PVPA) to the electrode of the aforementioned comparative example. It is to be noted herein that Pt . C .
Nafion~ . PVPA = 60 . 40 . 28 . 14.
(2) Analysis of Dispersion Behavior by TG-MS
Amounts of gas generated form the antioxidant-added electrode sheets at respective temperatures were measured by means of TG-MS so as to investigate an effect exerted upon pyrolysis by addition of polyvinyl phosphonic acid (PVPA) while temperature of atmosphere rose at a rate of 10°C/min was observed in the atmosphere of He. Among substances generated in this analysis, the behavior of generation of S02 (Fig. 1) and fluorocarbon (Fig. 2) as a component obtained by decomposing Nafion~ are illustrated.
S02 generated in a temperature range indicated by "X"
in Fig. 1 is obtained through oxidation of sulfur adsorbed on carbon by oxygen adsorbed on carbon. The S02 thus generated has nothing to do with decomposition of Nafion~. The amount of S02 generated through decomposition of Nafion~ increases at or above a temperature of 200°C. However, the amount of S02 produced in this example is much smaller than the amount of S02 produced in the comparative example.
Referring to Fig. 2, generation of CF3+ and C2F5+ was observed in a temperature range at or above 250°C in the comparative example. This generation of CF3+ and C2F5+
results from decomposition of Nafion~. On the other hand, in the example, generation of C2F5+ was not observed, and only generation of CF3+ was observed. Also, the amount of CF3+ in the example is smaller than the amount of CF3+ in the comparative example.
The aforementioned result of analysis has revealed that addition of polyvinyl phosphoric acid (PVPA) substantially improves stability in thermal decomposition of Nafion~ in the electrode. Although this mechanism of suppressing decomposition is not quite obvious, it is inferable that a chain reaction of decomposition may have been stopped by stabilizing a carbon radical after detachment of a sulfonic acid group.
(3) Evaluation of Variation in Stability with Time Based on Evaluation of Battery [Initial Properties) Fig. 3 illustrates a result of an I-V evaluation (current-voltage evaluation) which was performed under the conditions of cell: 80°C, A bubbler (anode): H2, 275cc/min, C bubbler (cathode): Air, 912cc/min, and both electrodes: 2ata.
Referring to Fig. 3, although polyvinyl phosphoric acid (PVPA) was added in the example, the gradient of the example is substantially equal to the gradient of the comparative example. Also, the example and the comparative example are substantially identical in contact resistance between the membrane and the electrode. Further, the example and the comparative example are also substantially identical in limiting current value and drainage properties of the electrode.
In general, the fact that the limiting current remains substantially unchanged despite an increase in weight corresponding to a multiplier of 1.5 and an increase in volume corresponding to a multiplier of about 2 because of addition of polyvinyl phosphoric acid (PVPA) demonstrates that addition of polyvinyl phosphoric acid (PVPA) does not deteriorate drainage properties. In addition, referring to Fig. 3, the voltage is lower in the example than in the comparative example on the whole.
This is considered to result from catalytic activity.
However, the voltage can be adjusted by reducing an amount of polyvinyl phosphoric acid (PVPA) to be added.
The aforementioned result of the evaluation has revealed that addition of polyvinyl phosphoric acid (PVPA) causes no change in fuel cell properties, especially, no change in resistance or limiting current value.
[Gas Leakage Amount in Acceleration Durability Test]
Continuous operation was performed under conditions of cell: 80°C, A: humidified H2 gas, and C: humidified air, and under load conditions including a condition of an open circuit. The result is illustrated in Fig. 4.
Referring to Fig. 4, while the gas leakage amount starts increasing at an early stage in the comparative example, the gas leakage amount remains small in the example even after the lapse of 250 hours. Although it is intrinsically in the electrolyte of the electrode that an antioxidant effect based on addition of polyvinyl phosphoric acid (PVPA) is expected, the result illustrated in Fig. 4 reveals that the electrolyte membrane is also inhibited from deteriorating. Although the cause for this phenomenon has not been elucidated in detail, it is inferable that a peroxide radical generated 5 in the electrode or a decompositional radical may have been deactivated by the antioxidant and that diffusion of the radical into the electrolyte membrane may have been suppressed as a result.
By introducing a functional group containing 10 phosphorus into a fluoropolymer electrolyte or combining a fluoropolymer electrolyte with an antioxidant, it becomes possible to suppress generation of a hydrogen peroxide radical even in the case where the radical is generated at a high temperature. As a result, durability 15 of the fluoropolymer electrolyte is enhanced. Also, since separation of micro phases between hydrophilic portions of the fluoropolymer and the antioxidant and hydrophobic portions of the fluoropolymer and the antioxidant leads to an increase in porosity, a proton 20 exchange material is prevented from covering the catalyst in the electrode. Accordingly, the performance of the fuel cell can be maintained.
Claims (16)
1. A high-durability polymer electrolyte composite comprising a polymer electrolyte and a compound containing alkyl phosphonic acid.
2. The polymer electrolyte composite according to claim 1, wherein the compound containing alkyl phosphonic acid comprises at least one of polyvinyl phosphonic acid, xylidyl phosphonic acid, and benzyl phosphonic acid.
3. The polymer electrolyte composite according to claim 1, wherein the compound containing alkyl phosphonic acid includes a polymer containing phosphorus.
4. The polymer electrolyte composite according to claim 3, wherein the polymer containing phosphorus includes polyvinyl phosphonic acid.
5. The polymer electrolyte composite according to claim 1, wherein the compound containing alkyl phosphonic acid comprises at least one of conjugated organic phosphate, polyphosphate, and tetrapentaerythritol.
6. The polymer electrolyte composite according to claim 1, wherein the polymer electrolyte composite contains 0.005 to 10 wt.% of the compound containing alkyl phosphonic acid.
7. The polymer electrolyte composite according to claim 6, wherein the polymer electrolyte composite contains 0.01 to 5 wt.% of the compound containing alkyl phosphonic acid.
8. The polymer electrolyte composite according to claim 1, wherein an amount of introduction of the compound containing alkyl phosphonic acid is 0.1 to 100 mol% of an amount of an entire electrolyte functional group in the polymer electrolyte.
9. The polymer electrolyte composite according to claim 8, wherein an amount of introduction of the compound containing alkyl phosphonic acid is 5 to 100 mol% of an amount of an entire electrolyte functional group in the polymer electrolyte.
10. A polymer electrolyte composite comprising a polymer electrolyte and at least one of a metal deactivator, a phenol compound, an amine compound and a sulfur compound.
11. A fuel cell electrode comprising an electric conductor carrying a catalyst, and at least one of a high-durability polymer electrolyte in which a functional group containing phosphorus has been introduced into a polymer electrolyte and a high-durability polymer electrolyte composite including a polymer electrolyte and an antioxidant.
12. The fuel cell electrode according to claim 11, wherein the antioxidant includes at least one of at least one of a compound containing phosphorus, a metal deactivator, a phenol compound, an amine compound and a sulfur compound.
13. The fuel cell electrode according to claim 12, wherein the antioxidant includes the compound containing phosphorus.
14. The fuel cell electrode according to claim 13, wherein the compound containing phosphorus includes a compound containing alkyl phosphonic acid.
15. The fuel cell electrode according to claim 14, wherein the compound containing alkyl phosphonic acid includes polyvinyl phosphonic acid.
16. A fuel cell comprising the fuel cell electrode according to claim 11.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002-298438 | 2002-10-11 | ||
| JP2002298438A JP3925382B2 (en) | 2002-10-11 | 2002-10-11 | High durability polymer electrolyte, composition, and fuel cell |
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| CA2444647A1 true CA2444647A1 (en) | 2004-04-11 |
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| CA002444647A Abandoned CA2444647A1 (en) | 2002-10-11 | 2003-10-10 | High-durability polymer electrolyte, high-durability polymer electrolyte composite, electrode, and fuel cell |
Country Status (3)
| Country | Link |
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| JP (1) | JP3925382B2 (en) |
| CA (1) | CA2444647A1 (en) |
| DE (2) | DE10362101B4 (en) |
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| GB2434370A (en) * | 2006-01-19 | 2007-07-25 | Sumitomo Chemical Co | A polymer electrolyte composition |
| US7833676B2 (en) | 2004-07-09 | 2010-11-16 | Nissan Motor Co., Ltd. | Fuel cell system and solid polymer electrolyte film |
| CN102017255A (en) * | 2008-02-29 | 2011-04-13 | 住友化学株式会社 | Polymer electrolyte composition |
| US8323809B2 (en) | 2005-09-19 | 2012-12-04 | 3M Innovative Properties Company | Fuel cell electrolyte membrane with basic polymer |
| CN103998527A (en) * | 2011-12-20 | 2014-08-20 | 东丽株式会社 | Polymer electrolyte composition, and polymer electrolyte membrane, membrane-electrode assembly, and polymer electrolyte fuel cell each using same |
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| JP4979179B2 (en) * | 2003-08-22 | 2012-07-18 | 株式会社豊田中央研究所 | Solid polymer fuel cell and manufacturing method thereof |
| US7799485B2 (en) | 2004-07-09 | 2010-09-21 | Nissan Motor Co., Ltd. | Fuel cell system and composition for electrode |
| WO2006067872A1 (en) * | 2004-12-24 | 2006-06-29 | Asahi Kasei Kabushiki Kaisha | Highly durable electrode catalyst layer |
| US7579116B2 (en) * | 2005-04-01 | 2009-08-25 | Gm Global Technology Operations, Inc. | Fluoride ion scavenger for fuel cell components |
| US20060222920A1 (en) * | 2005-04-01 | 2006-10-05 | Belabbes Merzougui | Metal cations chelators for fuel cells |
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| JP5233069B2 (en) | 2005-12-15 | 2013-07-10 | 日産自動車株式会社 | Fuel cell system and fuel cell vehicle |
| CN101689637A (en) | 2007-06-15 | 2010-03-31 | 住友化学株式会社 | Catalyst ink, method for producing catalyst ink, method for producing membrane-electrode assembly, membrane-electrode assembly produced by the method, and fuel cell |
| US20100159351A1 (en) * | 2007-06-15 | 2010-06-24 | Sumitomo Chemical Company Limited | Membrane-electrode assembly, and membrane-electrode-(gas diffusion layer) assembly and solid polymer fuel cell each comprising the same |
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| US20120107725A1 (en) | 2009-06-24 | 2012-05-03 | Toyo Boseki Kabushiki Kaisha | Solid Polymer Electrolyte Composition, and Ion-Exchange Membrane, Membrane Electrode Assembly and Fuel Cell |
| WO2013161405A1 (en) * | 2012-04-26 | 2013-10-31 | Jsr株式会社 | Composition for electrolyte membranes, solid polymer electrolyte membrane, method for producing solid polymer electrolyte membrane, membrane-electrode assembly, solid polymer fuel cell, water electrolysis cell, and water electrolysis system |
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|---|---|---|---|---|
| US5422411A (en) * | 1993-09-21 | 1995-06-06 | Ballard Power Systems Inc. | Trifluorostyrene and substituted trifluorostyrene copolymeric compositions and ion-exchange membranes formed therefrom |
| DE19653484A1 (en) * | 1996-12-20 | 1998-06-25 | Fraunhofer Ges Forschung | Method for producing membrane electrode assemblies and a membrane electrode assembly thus produced |
| JPH11354140A (en) * | 1998-06-10 | 1999-12-24 | Toyota Central Res & Dev Lab Inc | Thin film electrolyte having high strength |
| JP3506213B2 (en) * | 1998-06-22 | 2004-03-15 | 株式会社豊田中央研究所 | Highly durable solid polymer electrolyte |
| JP2000011756A (en) * | 1998-06-22 | 2000-01-14 | Toyota Central Res & Dev Lab Inc | High-durability solid high molecular electrolyte |
| US6902801B2 (en) * | 2000-03-22 | 2005-06-07 | Victrex Manufacturing Limited | Composite ion exchange material |
| AU2001244303B2 (en) * | 2000-03-22 | 2005-08-18 | Victrex Manufacturing Limited | Ion exchange materials |
| US7288603B2 (en) * | 2000-11-13 | 2007-10-30 | Toyo Boseki Kabushiki Kaisha | Polybenzazole compound having sulfonic acid group and/or phosphonic acid group, resin composition containing the same, resin molding, solid polymer electrolyte membrane, solid polymer electrolyte membrane/electrode assembly and method of preparing assembly |
| DE10220818A1 (en) * | 2002-05-10 | 2003-11-20 | Celanese Ventures Gmbh | Process for producing a grafted polymer electrolyte membrane and its use in fuel cells |
-
2002
- 2002-10-11 JP JP2002298438A patent/JP3925382B2/en not_active Expired - Lifetime
-
2003
- 2003-10-10 CA CA002444647A patent/CA2444647A1/en not_active Abandoned
- 2003-10-13 DE DE10362101A patent/DE10362101B4/en not_active Expired - Fee Related
- 2003-10-13 DE DE10347457A patent/DE10347457B4/en not_active Expired - Fee Related
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| US7833676B2 (en) | 2004-07-09 | 2010-11-16 | Nissan Motor Co., Ltd. | Fuel cell system and solid polymer electrolyte film |
| US8252481B2 (en) | 2004-07-09 | 2012-08-28 | Nissan Motor Co., Ltd. | Fuel cell system and solid polymer electrolyte film |
| US8323809B2 (en) | 2005-09-19 | 2012-12-04 | 3M Innovative Properties Company | Fuel cell electrolyte membrane with basic polymer |
| GB2434370A (en) * | 2006-01-19 | 2007-07-25 | Sumitomo Chemical Co | A polymer electrolyte composition |
| GB2434370B (en) * | 2006-01-19 | 2008-07-30 | Sumitomo Chemical Co | Polymer electrolyte composition and application thereof |
| CN102017255A (en) * | 2008-02-29 | 2011-04-13 | 住友化学株式会社 | Polymer electrolyte composition |
| CN103998527A (en) * | 2011-12-20 | 2014-08-20 | 东丽株式会社 | Polymer electrolyte composition, and polymer electrolyte membrane, membrane-electrode assembly, and polymer electrolyte fuel cell each using same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3925382B2 (en) | 2007-06-06 |
| DE10347457A1 (en) | 2004-04-29 |
| DE10362101B4 (en) | 2010-04-08 |
| DE10347457B4 (en) | 2009-10-15 |
| JP2004134269A (en) | 2004-04-30 |
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