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WO2013167950A1 - Ensembles électrode-membrane améliorés et piles à combustible à grande longévité - Google Patents

Ensembles électrode-membrane améliorés et piles à combustible à grande longévité Download PDF

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Publication number
WO2013167950A1
WO2013167950A1 PCT/IB2013/000874 IB2013000874W WO2013167950A1 WO 2013167950 A1 WO2013167950 A1 WO 2013167950A1 IB 2013000874 W IB2013000874 W IB 2013000874W WO 2013167950 A1 WO2013167950 A1 WO 2013167950A1
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Prior art keywords
acid
aromatic
membrane
membrane according
mono
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PCT/IB2013/000874
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English (en)
Inventor
Oliver Gronwald
Original Assignee
Basf Se
Basf (China) Company Limited
Basf Schweiz Ag
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Application filed by Basf Se, Basf (China) Company Limited, Basf Schweiz Ag filed Critical Basf Se
Priority to EP13787033.3A priority Critical patent/EP2847253A4/fr
Publication of WO2013167950A1 publication Critical patent/WO2013167950A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/18—Polybenzimidazoles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/22—Polybenzoxazoles
    • 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
    • H01M8/1027—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having carbon, oxygen and other atoms, e.g. sulfonated polyethersulfones [S-PES]
    • 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
    • H01M8/103—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having nitrogen, e.g. sulfonated polybenzimidazoles [S-PBI], polybenzimidazoles with phosphoric acid, sulfonated polyamides [S-PA] or sulfonated polyphosphazenes [S-PPh]
    • 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
    • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1081—Polymeric electrolyte materials characterised by the manufacturing processes starting from solutions, dispersions or slurries exclusively of polymers
    • 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
    • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1086—After-treatment of the membrane other than by polymerisation
    • H01M8/1088—Chemical modification, e.g. sulfonation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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
    • 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
    • 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

Definitions

  • the present invention relates to improved membrane electrode assemblies and fuel cells with long lifetime, comprising two electrochemically active electrodes separated by a polymer electrolyte membrane.
  • Predominantly perfluorinated polymers are employed.
  • a prominent example thereof is NafionTM from DuPont de Nemours, Wilmington, USA.
  • a relatively high water content in the membrane is required, which is typically 4-20 molecules of water per sulfonic acid group.
  • WO 02/088219 discloses a second generation of high-temperature fuel cell based on polyazoles, which are produced by condensation polymerization in polyphosphoric acid (PPA) and partial hydrolysis of the same reaction mixture.
  • PPA polyphosphoric acid
  • These proton-conducting polymer membranes exhibit improved properties compared to the membranes known from WO 96/13872. Nevertheless, these membranes too can still be improved for long-term operation in a high-temperature fuel cell.
  • sustained use temperatures of 160-180°C and frequent startup and shutdown of the fuel cell degradation or aging of the membrane cannot be ruled out. Under some circumstances, this degradation can lead to an irreversible failure of the membrane electrode assembly.
  • the inventive membrane or MEA which comprises such a membrane has especially the following properties:
  • the fuel cells should have, after long operating time, a high zero-load voltage and low gas crossover.
  • the fuel cells should be usable especially at operating temperatures above 100°C and not need any additional fuel gas moistening. More particularly, the membrane electrode assemblies should be able to withstand permanent or changing pressure differences between anode and cathode.
  • the fuel cell even after a long time should have a high
  • the MEA should be robust to different operating conditions (T, p, geometry, etc.) in order to increase general reliability.
  • the present invention provides a proton-conducting polymer membrane based on copolymers comprising (I) polybenzoxazoles and (II) polybenzimidazoles, obtainable by a process comprising the steps of
  • step (ii) heating the mixture from step (i), preferably under inert gas, to temperatures in the range from 120°C up to 300°C and polymerizing until attainment of a polybenzoxazole polymer having an intrinsic viscosity of up to 1.5 dl/g,
  • step (iv) heating the mixture from step (iii), preferably under inert gas, to temperatures in the range from 120°C up to 300°C and polymerizing until attainment of a polybenzimidazole polymer having an intrinsic viscosity of up to 1.5 dl/g,
  • step (v) combining the polybenzoxazole polymer obtained in step (ii) and the
  • step (vi) applying a layer using the mixture according to step (v) to a support or to an electrode,
  • step (vii) at least partially hydrolyzing the polyphosphoric acid present in the layer from step (vi) by contacting with water and/or aqueous media,
  • the polymerization of the polybenzoxazole- polybenzimidazole block polymer according to step (v) can also be effected on the support or the electrode as what is called a thin-layer polymerization.
  • aromatic diamino dihydroxy compounds used in accordance with the invention are preferably 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'- diaminodiphenyl sulfone, 4,6-diamino-1 ,3-dihydroxybenzene (DABDO) and salts thereof, especially the mono and/or dihydrochloride derivatives thereof.
  • aromatic carboxylic acids used in accordance with the invention are dicarboxylic acids, or else dicarboxylic acids in combination with tricarboxylic acids and/or tetracarboxylic acids.
  • aromatic carboxylic acids it is also possible to use the esters, anhydrides or acid chlorides thereof.
  • aromatic dicarboxylic acids preference is given to those in which the acid groups are in the para position on the aromatic ring.
  • aromatic carboxylic acids likewise also comprises heteroaromatic carboxylic acids.
  • the aromatic dicarboxylic acids are preferably isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N,N-dimethylaminoisophthalic acid, 5-N,N-diethylaminoisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,6- dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 3-fluorophthalic acid, 5- fluoroisophthalic acid, 2-fluoroterephthalic acid, tetrafluorophthalic acid,
  • tetrafluoroisophthalic acid tetrafluoroterephthalic acid,1 ,4-naphthalenedicarboxylic acid, 1 ,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7- naphthalenedicarboxylic acid, diphenic acid, 1 ,8-dihydroxynaphthalene-3,6- dicarboxylic acid, diphenyl ether 4,4'-dicarboxylic acid, benzophenone-4,4'- dicarboxylic acid, diphenyl sulfone 4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, 2,2-bis(4-carboxyphenyl)hexafluoropropane, 4,4'- stilbenedicarboxylic acid and 4-carboxycinnamic acid, or the C1-C20-alkyl esters or C
  • aromatic tricarboxylic acids or the C1-C20-alkyl esters or C5-C12-aryl esters thereof or acid anhydrides thereof or acid chlorides thereof are preferably 1 ,3,5- benzenetricarboxylic acid (trimesic acid), 1 ,2,4-benzenetricarboxylic acid (trimellitic acid), (2-carboxyphenyl)iminodiacetic acid, 3,5,3'-biphenyltricarboxylic acid, 3,5,4'- biphenyltricarboxylic acid.
  • aromatic tetracarboxylic acids or the C1-C20-alkyl esters or C5-C12-aryl esters thereof or acid anhydrides thereof or acid chlorides thereof are preferably 3, 5, 3', 5'- biphenyltetracarboxylic acid, 1 ,2,4,5-benzenetetracarboxylic acid,
  • benzophenonetetracarboxylic acid S.S' ⁇ '-biphenyltetracarboxylic acid, 2, 2', 3,3'- biphenyltetracarboxylic acid, 1 ,2,5,6-naphthalenetetracarboxylic acid, 1 ,4,5,8- naphthalenetetracarboxylic acid.
  • heteroaromatic carboxylic acids used in accordance with the invention are heteroaromatic dicarboxylic acids, heteroaromatic tricarboxylic acids and
  • heteroaromatic tetracarboxylic acids or the esters thereof or anhydrides thereof.
  • Heteroaromatic carboxylic acids are understood to mean aromatic systems which comprise at least one nitrogen, oxygen, sulfur or phosphorus atom in the aromatic system. They are preferably pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5- pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzimidazole- 5,6-dicarboxylic acid, and the C1-C20-alkyl esters or C5-C12-aryl esters thereof, or acid anhydrides thereof or acid chlorides thereof.
  • the content of tricarboxylic acid or tetracarboxylic acids is between 0 and 30 mol%, preferably 0.1 and 20 mol%, especially 0.5 and 10 mol%.
  • aromatic and/or heteroaromatic amino hydroxy carboxylic acids used in accordance with the invention are preferably 3-amino-4-hydroxybenzoic acid and 4- amino-3-hydroxybenzoic acid.
  • the aromatic and heteroaromatic tetraamino compounds used in accordance with the invention are preferably 3,3',4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1 ,2,4,5-tetraaminobenzene, S.S' ⁇ '-tetraaminodiphenyl sulfone, 3, 3', 4,4'- tetraaminodiphenyl ether, 3,3',4,4'-tetraaminobenzophenone, 3,3',4,4'- tetraaminodiphenylmethane and 3,3',4,4'-tetraaminodiphenyldimethylmethane and salts thereof, especially the mono-, di-, tri- and tetrahydrochloride derivatives.
  • the aromatic and heteroaromatic diamino carboxylic acids used in accordance with the invention are preferably diaminobenzoic acid and the mono- and dihydroch
  • the mixing ratio of aromatic carboxylic acids to heteroaromatic carboxylic acids is between 1 :99 and 99: 1 , preferably 1 :50 to 50: 1 , especially 1 : 10 to 10: 1.
  • N-heteroaromatic dicarboxylic acids and aromatic dicarboxylic acids are especially mixtures of N-heteroaromatic dicarboxylic acids and aromatic dicarboxylic acids.
  • Nonlimiting examples thereof are isophthalic acid, terephthalic acid, phthalic acid, 2,5-dihydroxyterephthalic acid, 2,6- dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 1 ,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7- naphthalenedicarboxylic acid, diphenic acid, 1 ,8-dihydroxynaphthalene-3,6- dicarboxylic acid, diphenyl ether 4,4'-dicarboxylic acid, benzophenone-4,4'- di
  • the polyphosphoric acid used in steps (i) and (iii) comprises commercial
  • polyphosphoric acids as obtainable, for example, from Riedel-de Haen.
  • the polyphosphoric acids H n +2Pn0 3 n+i (n> 1 ) typically have a content, calculated as 2O5 (by acidimetric means) of at least 79.8%, which corresponds to a concentration of min. 110% H3PO4.
  • a content calculated as 2O5 (by acidimetric means) of at least 79.8%, which corresponds to a concentration of min. 110% H3PO4.
  • the mixtures obtained in steps (i) and (iii) each have a weight ratio of polyphosphoric acid to the sum of all monomers of 1 : 10 000 to 10 000: 1 , preferably 1 : 1000 to 1000:1 , especially 1 :100 to 100:1 , though the respective weight ratio may also be different. More preferably, the polyphosphoric acid in steps (i) and (iii) contains 1 to 10% by weight of monomers.
  • the heating of the mixture in steps (ii) and (iv) is effected typically within the temperature range from 120 to 300°C, preferably between 120°C and 250°C. It is advantageous here to increase the temperature stepwise, preferably in intervals each of 20 - 30°C.
  • the duration of the heating is typically between 2 and 100 hours, preferably between 5 and 80 hours, more preferably between 10 and 50 hours. Most preferably, the heating is at first kept within the temperature range from 130°C to 170°C in 3 intervals for the total duration of 10 to 20 hours and then kept within the temperature range from 170°C to 240°C in 3 intervals for the total duration of 10 to 20 hours.
  • the heating of the mixture in steps (ii) and (iv) leads to polymerization of the monomers present.
  • the polymerization in steps (ii) and (iv) is performed at a temperature and for a period of time until an intrinsic viscosity of up to 1.5 dl/g, preferably 0.3 to 1.0 dl/g, especially 0.5 to 0:8 dl/g, is present.
  • the respective duration and the exact reaction conditions depend on the reactivity of the respective monomers.
  • Polybenzoxazoles are understood to mean polymers which have at least one oxygen heteroatom and at least one nitrogen heteroatom in the aromatic system.
  • the aromatic system may be mono- or polycyclic and also comprises fused aromatic ring systems. Particular preference is given to aromatic systems in which one aromatic ring has at least one oxygen heteroatom and at least one nitrogen heteroatom.
  • the aromatic ring is preferably a five- or six-membered ring having one nitrogen atom and one oxygen atom, which may be fused to another ring, especially another aromatic ring.
  • a polymer having "high thermal stability" in the context of the present invention is one which can be operated for a prolonged period as a polymeric electrolyte in a fuel cell at temperatures above 120°C.
  • "For a prolonged period” means that an inventive membrane can be operated for at least 100 hours, preferably at least 500 hours, at at least 80°C, preferably at least 120°C, more preferably at least 160°C, without any decrease in the power, which can be measured by the method described in WO 01/18894 A2, by more than 50%, based on the starting power.
  • a particularly preferred group of polybenzoxazole polymers comprises those which comprise repeat oxazole units of the general formula (I) and/or (II) and/or (III) and/or (IV) and/or (V) and/or (VI) and/or (VI I)
  • Ar is the same or different and is a tetravalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 1 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 2 is the same or different and is a di- or trivalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 3 is the same or different and is a trivalent aromatic or heteroaromatic group
  • Ar 4 is the same or different and is a trivalent aromatic or heteroaromatic group
  • Ar 5 is the same or different and is a tetravalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 6 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 7 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 8 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 9 is the same or different and is a divalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • X is the same or different and is oxygen
  • n is an integer greater than or equal to 10, preferably greater than or equal to 100.
  • Preferred aromatic or heteroaromatic groups derive from benzene, naphthalene, biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenyl sulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzoxathiadiazole, benzoxadiazole, benzopyridine, benzopyrazine,
  • benzopyrazidine benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolizine, pyridopyridine, imidazopyrimidine, pyrazinopyrimidine, carbazole, acridine, phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine, benzopteridine, phenanthroline and phenanthrene, which may optionally also be substituted.
  • Ar 1 , Ar 4 , Ar 6 , Ar 7 , Ar 8 , Ar 9 is as desired; in the case of phenylene, for example, Ar 1 , Ar 4 , Ar 6 , Ar 7 , Ar 8 , Ar 9 may be ortho-, meta- and para- phenylene. Particularly preferred groups derive from benzene and biphenylene, which may optionally also be substituted.
  • Preferred alkyl groups are short-chain alkyl groups having 1 to 4 carbon atoms, for example methyl, ethyl, n- or i-propyl and t-butyl groups.
  • Preferred aromatic groups are phenyl or naphthyl groups.
  • the alkyl groups and the aromatic groups may be substituted.
  • Preferred substituents are halogen atoms, for example fluorine, amino groups, hydroxy groups or short-chain alkyl groups, for example methyl or ethyl groups.
  • the polybenzoxazoles may in principle also have different repeat units which differ, for example, in their X radical. However, it preferably has only identical X radicals in one repeat unit.
  • the polybenzoxazole polymer is a polymer which comprises only units of the formula (I) and/or (II).
  • the number of repeat oxazole units in the polymer is preferably an integer greater than or equal to 10.
  • Particularly preferred polymers comprise at least 1(30 repeat oxazole units.
  • polybenzoxazoles comprising repeat units of the following formulae:
  • n is an integer greater than or equal to 10, preferably greater than or equal to 100
  • X and Y are each independently an oxygen atom or an NH and/or NR group in which R is an organic radical, preferably a group having 1-20 carbon atoms, especially an alkyl radical having 1-20 carbon atoms, an aryl radical having 6- 20 carbon atoms, an alkylaryl radical having 7-20 carbon atoms or an arylalkyi radical having 7-20 carbon atoms.
  • Polybenzimidazoles are understood to mean polymers which have at least one nitrogen heteroatom and no oxygen heteroatom in the aromatic system.
  • the aromatic system may be mono- or polycyclic and also comprises fused aromatic ring systems. Particular preference is given to aromatic systems in which one aromatic ring has at least one nitrogen heteroatom.
  • the aromatic ring is preferably a five- or six-membered ring having one nitrogen atom, which may be fused to another ring, especially another aromatic ring.
  • a polymer having "high thermal stability" in the context of the present invention is one which can be operated for a prolonged period as a polymeric electrolyte in a fuel cell at temperatures above 120°C. "For a prolonged period” means that an inventive membrane can be operated for at least 100 hours, preferably at least 500 hours, at at least 80°C, preferably at least 120°C, more preferably at least 160°C, without any decrease in the power, which can be measured by the method described in WO 01/18894 A2, by more than 50%, based on the starting power.
  • a particularly preferred group of polybenzimidazole polymers is those with repeat azole units of the general formula (I) and/or (II) and/or (III) and/or (IV) and/or (V) and/or (VI) and/or (VII) and/or (VIII) and/or (IX) and/or (X) and/or (XI) and/or (XII) and/or (XIII) and/or (XIV) and/or (XV) and/or (XVI) and/or (XVII) and/or (XVIII) and/or (XIX) and/or (XX) and/or (XXI) and/or (XXII) and/or (XXII))
  • Ar is the same or different and is a tetravalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 1 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 2 is the same or different and is a di- or trivalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 3 is the same or different and is a trivalent aromatic or heteroaromatic group
  • Ar 4 is the same or different and is a trivalent aromatic or heteroaromatic group
  • Ar 5 is the same or different and is a tetravalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 6 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 7 is the same or different and is a divalent aromatic or heteroaromatic group
  • Ar 8 is the same or different and is a trivalent aromatic or heteroaromatic group
  • Ar 9 is the same or different and is a di- or tri- or tetravalent aromatic or
  • heteroaromatic group which may be mono- or polycyclic
  • Ar 10 is the same or different and is a di- or trivalent aromatic or heteroaromatic group which may be mono- or polycyclic,
  • Ar 11 is the same or different and is a divalent aromatic or heteroaromatic group
  • X is the same or different and is nitrogen or an amino group which bears a
  • R is the same or different and is hydrogen, an alkyl group or an aromatic group, with the proviso that R in formula (XX) is not hydrogen, and
  • n, m are each an integer greater than or equal to 10, preferably greater than or equal to 100.
  • Preferred aromatic or heteroaromatic groups derive from benzene, naphthalene, biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenyl sulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzoxathiadiazole, benzoxadiazole, benzopyridine, benzopyrazine,
  • benzopyrazidine benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolizine, pyridopyridine, imidazopyrimidine, pyrazinopyrimidine, carbazole, acridine, phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine, benzopteridine, phenanthroline and phenanthrene, which may optionally also be substituted.
  • Ar 1 , Ar 4 , Ar 6 , Ar 7 , Ar 8 , Ar 9 , Ar 10 , Ar 11 is as desired; in the case of phenylene, for example, Ar 1 , Ar 4 , Ar 6 , Ar 7 , Ar 8 , Ar 9 , Ar 10 , Ar 11 may be ortho-, meta- and para-phenylene. Particularly preferred groups derive from benzene and biphenylene, which may optionally also be substituted.
  • Preferred alkyl groups are short-chain alkyl groups having 1 to 4 carbon atoms, for example methyl, ethyl, n- or i-propyl and t-butyl groups.
  • Preferred aromatic groups are phenyl or naphthyl groups.
  • the alkyl groups and the aromatic groups may be substituted.
  • Preferred substituents are halogen atoms, for example fluorine, amino groups, hydroxy groups or short-chain alkyl groups, for example methyl or ethyl groups.
  • the polybenzimidazoles may in principle also have different repeat units which differ, for example, in their X radical. However, it preferably has only identical X radicals in one repeat unit.
  • the number of repeat azole units in the polymer is preferably an integer greater than or equal to 10.
  • Particularly preferred polymers comprise at least 100 repeat azole units.
  • n and m are each an integer greater than or equal to 10, preferably greater than or equal to 100.
  • the polymerization to give the polybenzoxazole-polybenzimidazole block polymer is effected in step (v).
  • the polymerization is performed at a temperature and for a period of time until the intrinsic viscosity is more than 1.5 dl/g, preferably more than 1.8 dl/g, especially more than 1.9 dl/g.
  • the heating in step (v) is effected typically within the temperature range from 120 to 300°C, preferably between 120°C and 250°C. It is advantageous here to increase the temperature stepwise, preferably in intervals each of 20 - 30°C.
  • the duration of the heating is typically between 2 and 100 hours, preferably between 5 and 80 hours, more preferably between 10 and 50 hours.
  • the heating is at first kept within the temperature range from 130°C to 170°C in 3 intervals for the total duration of 10 to 20 hours and then kept within the temperature range from 170°C to 240°C in 3 intervals for the total duration of 10 to 20 hours.
  • step (v) The heating of the mixture in step (v) leads to polymerization of the polybenzoxazole and polybenzimidazole blocks present and to the formation of the inventive
  • polybenzoxazoles and polybenzimidazoles are known in principle, the parent monomers being converted to a prepolymer in the melt. The resulting prepolymer solidifies in the reactor and is then mechanically comminuted. The pulverulent prepolymer is typically finally polymerized in a solid phase polymerization at temperatures of up to 400°C.
  • the parent monomers can be condensed in polyphosphoric acid and then precipitated by introduction into water and washed to neutrality.
  • inventive copolymers comprising polybenzoxazole and polybenzimidazole units can be used individually or as a mixture (blend).
  • blends comprising polysulfones and/or polyether ketones.
  • the preferred blend components are polyether sulfone, polyether ketone, and polymers modified with sulfonic acid groups, as described in patent application EP-A-1337319 and
  • inventive copolymers comprising polybenzoxazole and polybenzimidazole units
  • they are admixed with the polymers described hereinafter, but especially with polysulfones and/or polyether sulfone, or added as early as in the course of production of the copolymer, for example in step (i), (ii), (iii), (iv) and/or (v) (reactor blend).
  • the preferred polysulfones include especially polysulfone with aromatic and/or heteroaromatic groups in the main chain.
  • preferred polysulfones and polyether sulfones have a melt volume flow rate MVR 300/21.6 less than or equal to 40 cm 3 /10 min, especially less than or equal to 30 cm 3 /10 min and more preferably less than or equal to 20 cm 3 /10 min, measured to ISO 1133.
  • Preference is given here to polysulfones having a Vicat softening temperature VST/A/50 of 180°C to 230°C.
  • the number-average molecular weight of the polysulfones is greater than 30 000 g/mol.
  • the polymers based on polysulfone include especially polymers which have repeat units with linking sulfone groups according to the general formulae A, B, C, D, E, F and/or G:
  • R radicals are the same or different and are each independently an aromatic or heteroaromatic group, these radicals having been elucidated in detail above.
  • R radicals include especially 1 ,2-phenylene, 1 ,3-phenylene, 1 ,4-phenylene, 4,4'- biphenyl, pyridine, quinoline, naphthalene, phenanthrene.
  • polysulfones preferred in the context of the present invention include homo- and copolymers, for example random copolymers.
  • Particularly preferred polysulfones comprise repeat units of the formulae H to N:
  • polysulfones can be obtained commercially under the trade names ® Victrex 200 P, ® Victrex 720 P, ® Ultrason E, ® Ultrason S, ® Mindel, ® Radel A, ® Radel R, ® Victrex HTA, ® Astrel and ® Udel.
  • polyether ketones polyether ketones, polyether ketone ketones, polyether ether ketones, polyether ether ketone ketones and polyaryl ketones.
  • These high-performance polymers are known per se and can be obtained commercially under the trade names Victrex® PEEKTM, ® Hostatec, ® Kadel.
  • step (vi) the polybenzoxazole-polybenzimidazole block polymer formed in step (v), which is still present together with the polyphosphoric acid used in step (i) and (iii), is applied to a support or to an electrode.
  • This layer formation is effected by means of measures known per se (casting, spraying, knife-coating), which are known from the prior art for polymer film production.
  • Suitable supports are all supports which can be described as inert under the conditions.
  • phosphoric acid cone, phosphoric acid, 85%
  • the viscosity can thus be adjusted to the desired value and the formation of the membrane can be facilitated.
  • the layer obtained in step (vi) has a thickness between 20 and 4000 pm, preferably between 30 and 3500 pm, especially between 50 and 3000 pm.
  • the formation of the layer in step (vi) can also be effected directly on an electrode.
  • the at least partial hydrolysis in step (vii) can correspondingly be shortened as a result, since there is no longer any need for the layer or membrane formed to be self-supporting.
  • Such a membrane also forms part of the subject matter of the present invention.
  • the at least partial hydrolysis of the polyphosphoric acid still present in step (vii) is effected by contacting the membrane present on the support with water and/or an aqueous medium.
  • the partial hydrolysis is effected preferably at temperatures above 0°C and below 200°C, preferably at temperatures between 10°C and 120°C, especially between room temperature (20°C) and 90°C.
  • a suitable aqueous medium is water and/or water vapor and/or water-containing phosphoric acid of up to 85%.
  • the hydrolysis is effected preferably under standard pressure, but can also be effected under the action of pressure. It is essential that the treatment proceeds in the presence of sufficient humidity, as a result of which the polyphosphoric acid present is at least partially hydrolyzed. This forms substances including low molecular weight polyphosphoric acid and/or phosphoric acid, which contribute to the consolidation of the membrane.
  • the ambient air has sufficient air humidity, for example relative humidity min. 30%, the hydrolysis can also be effected by the ambient air.
  • the partial hydrolysis of the polyphosphoric acid in step (vii) leads to consolidation of the membrane and to a decrease in the layer thickness, and formation of a membrane which has a thickness between 15 and 3000 pm, preferably between 20 and 2000 pm, especially between 20 and 1500 pm, and which is self-supporting.
  • the intra- and intermolecular structures present in the polyphosphoric acid/block polymer layer in step (vi) or step (vii) (interpenetrating networks, IPNs) lead, in step (vii), to ordered membrane formation which is found to be responsible for the exceptional properties of the membrane formed.
  • step (vii) causes a sol-gel transition and leads to a rubber-like membrane in which the polybenzoxazole/polybenzimidazole block polymer acts like a superabsorbent for the polyphosphoric acid/phosphoric acid.
  • the inventive membranes have a high content of phosphoric acid and are not comparable with subsequently doped membranes.
  • the at least partial hydrolysis can also be effected in climate-controlled chambers in which the hydrolysis can be controlled in a targeted manner under defined action of moisture.
  • the humidity can be adjusted in a controlled manner via the temperature or saturation of the contacting environment, for example gases such as air, nitrogen, carbon dioxide or other suitable gases, or water vapor.
  • gases such as air, nitrogen, carbon dioxide or other suitable gases, or water vapor.
  • the treatment time depends on the parameters selected above.
  • the treatment time depends on the membrane thicknesses.
  • the treatment time is between a few seconds and minutes, for example under the action of superheated steam, or up to whole days, for example under air at room temperature and low relative air humidity.
  • the treatment time is preferably between 10 seconds and 300 hours, especially 1 minute to 200 hours.
  • the treatment time is between 1 and 200 hours.
  • the membrane obtained in step (vii) can be configured so as to be self-supporting, i.e. it can be detached without damage from the support and then optionally processed further directly.
  • the at least partial hydrolysis can also be effected in an aqueous liquid, in which case this liquid may also comprise suspended and/or dispersed constituents.
  • the viscosity of the hydrolysis liquid may be within wide ranges, and the viscosity can be adjusted by adding solvents or increasing the temperature.
  • the dynamic viscosity is preferably in the range from 0.1 to 10 000 mPa*s, especially 0.2 to 2000 mPa * s, these values being measurable, for example, to DIN 53015.
  • the at least partial hydrolysis in step (vii) can be effected by any known method.
  • the membrane can be dipped into a liquid bath.
  • the hydrolysis liquid can be sprayed onto the membrane.
  • the hydrolysis liquid can also be poured over the membrane. The latter methods have the advantage that the concentration of acid in the hydrolysis liquid remains constant during the hydrolysis. However, the first process is frequently less expensive to execute.
  • the hydrolysis liquid comprises aqueous mixtures of oxygen acids of phosphorus and/or sulfur, especially phosphinic acid, phosphonic acid, phosphoric acid, hypodiphosphonic acid, hypodiphosphoric acid, oligophosphoric acids, sulfurous acid, disulfurous acid and/or sulfuric acid. These acids can be used individually or as a mixture.
  • the hydrolysis liquid comprises water, though the concentration of the water is generally not particularly critical.
  • the hydrolysis liquid comprises 5 to 80% by weight, preferably 8 to 70% by weight and more preferably 10 to 50% by weight of water.
  • the amount of water present formally in the oxygen acids is not included in the water content of the hydrolysis liquid.
  • phosphoric acid and/or sulfuric acid are particularly preferred, these acids comprising especially 5 to 70% by weight, preferably 10 to 60% by weight and more preferably 15 to 50% by weight of water.
  • the concentration of the phosphoric acid is reported as moles of acid per mole of repeat unit of the polymer.
  • a concentration (moles of phosphoric acid based on one repeat unit of the formula Ci8HioN 2 0 2 , i.e. polybenzoxazole) is between 10 and 50, preferably between 13 and 40 and especially between 15 and 35 mol.
  • the inventive membranes comprise preferably between 2 and 15% by weight of polybenzoxazole-polybenzimidazole block polymers and between 40 and 70% by weight of phosphoric acid, the remaining amount being water. Particular preference is given to polybenzoxazole-polybenzimidazole block polymer contents of 5 to 10% by weight and proportions of phosphoric acid of 50 to 60% by weight, the remaining amount being water.
  • the membrane can also be surface-treated by the action of heat in the presence of atmospheric oxygen. This curing of the membrane surface additionally improves the properties of the membrane. This treatment can also be effected by action of IR or NIR
  • IR infrared, i.e. light with a wavelength of more than 700 nm
  • NIR near IR, i.e. light with a wavelength in the range from approx. 700 to 2000 nm or an energy in the. range from approx. 0.6 to 1.75 eV).
  • a further method is irradiation with ⁇ rays.
  • the radiation dose here is between 5 and 200 kGy.
  • the inventive polymer membrane has improved material properties over the polymer membranes known to date.
  • the inventive membranes have a good proton conductivity. At temperatures of 160°C, the latter is at least 0.1 S/cm, preferably at least 0.105 S/cm.
  • the proton conductivity is determined without additional moistening of the gases required.
  • fillers especially proton- conducting fillers, and additional acids can additionally be added to the membrane.
  • the addition can either be effected in step i) or may follow the polymerization.
  • Nonlimiting examples of proton-conducting fillers are:
  • sulfates such as: CsHS0 4 , Fe(SO 4 ) 2 , (NH 4 ) 3 H(SO 4 ) 2 , LiHSO 4 , NaHS0 4 , KHS0 4 ,
  • phosphates such as Zr 3 (P0 ) 4 , Zr(HP0 4 ) 2 , HZr 2 (PO 4 ) 3 , UO 2 P0 4 .3H 2 0, H 8 U0 2 P0 4 ,
  • silicates such as zeolites, zeolites (NH 4 +), sheet silicates, framework silicates, H- natrolites, H-mordenites, NH 4 -analcines, NH 4 -sodalites, NH 4 - gallates, H-montmorillonites,
  • This membrane may also further comprise perfluorinated sulfonic acid additives (0.1- 20% by weight, preferably 0.2-15% by weight, very preferably 0.2-10% by weight). These additives lead to improved performance, in the vicinity of the cathode to an increase in the oxygen solubility and oxygen diffusion, and to a reduction in the adsorption of phosphoric acid and phosphate to platinum.
  • perfluorinated sulfonic acid additives 0.1- 20% by weight, preferably 0.2-15% by weight, very preferably 0.2-10% by weight.
  • Nonlimiting examples of perfluorinated sulfonic acid additives are:
  • the membrane may also further comprise as additives which scavenge (primary antioxidants) or destroy (secondary antioxidants) the peroxide radicals generated in oxygen reduction in the course of operation and thus, as described in JP2001118591 A2, improve lifetime and stability of the membrane and membrane electrode assembly.
  • additives which scavenge (primary antioxidants) or destroy (secondary antioxidants) the peroxide radicals generated in oxygen reduction in the course of operation and thus, as described in JP2001118591 A2, improve lifetime and stability of the membrane and membrane electrode assembly.
  • additives are:
  • inventive polymer membrane has additional improved material properties compared to the polymer membranes which are based on polyazoles and are known to date. For instance, the inventive membranes based on polyoxazoles exhibit improved compression resistance. This improved compression resistance results in an improved long-term stability with equal or virtually equal electrochemical performance.
  • the inventive polyazole membranes have, at operating temperatures of the membrane electrode assemblies of more than 00°C, preferably of 180-200°C, a compression resistance improved by a factor of 2 compared to polybenzimidazole membranes. This is found in an external test cell known to those skilled in the art, by the measurement of the decrease in thickness of a membrane sample within a given time window under the action of a profiled test body at the relevant operating temperatures.
  • the possible fields of use of the inventive doped polymer membranes include use in fuel cells, in electrolysis, in capacitors and in battery systems. Due to their profile of properties, the doped polymer membranes are preferably used in fuel cells.
  • the present invention also relates to a membrane electrode assembly comprising at least one inventive polymer membrane.
  • a membrane electrode assembly comprising at least one inventive polymer membrane.
  • the inventive membrane electrode assembly has two gas diffusion layers separated by the polymer electrolyte membrane.
  • Typically used for this purpose are flat, electrically conductive and acid-resistant structures. These include, for example, graphite fiber papers, carbon fiber papers, graphite mesh and/or papers which have been rendered conductive by addition of carbon black. These layers achieve fine distribution of the gas and/or liquid streams.
  • This gas distribution layer generally has a thickness in the range from 80 pm to 2000 ⁇ , especially 100 ⁇ to 1000 ⁇ and more preferably 150 ⁇ to 500 ⁇ .
  • at least one of the gas diffusion layers may consist of a compressible material.
  • a compressible material is characterized by the property that the gas diffusion layer can be compressed by pressure to half, especially to one third, of its original thickness without losing its integrity.
  • This property is generally possessed by gas diffusion layers composed of graphite mesh and/or paper which has been rendered conductive by addition of carbon black.
  • the inventive membrane electrode assembly also has a catalyst layer on each side of the membrane.
  • the catalyst layer may be present on both sides of the membrane or at the interface of the gas diffusion layer to the membrane.
  • the catalyst layer(s) comprise(s) catalytically active substances. These include noble metals of the platinum group, i.e. Pt, Pd, Ir, Rh, Os, Ru, or else the noble metals Au and Ag. In addition, it is also possible to use alloys of all aforementioned metals. Moreover, at least one catalyst layer may comprise alloys of the platinum group elements with base metals, for example Fe, Co, Ni, Cr, Mn, Zr, Ti, Ga, V etc.
  • the catalytically active particles which comprise the aforementioned substances can be used in the form of metal powders, known as noble metal blacks, especially platinum and/or platinum alloys.
  • metal powders known as noble metal blacks, especially platinum and/or platinum alloys.
  • Such particles generally have a size in the range from 5 nm to 200 nm, preferably in the range from 7 nm to 100 nm.
  • the metals can also be used on a support material.
  • This support preferably comprises carbon, which can be used especially in the form of carbon black, graphite or graphitized carbon black.
  • electrically conductive metal oxides for example SnO x , TiO x , or phosphates, for example FePO x , NbPO x , Zr y (PO x ) z as support material.
  • the indices x, y and z denote the oxygen or metal content of the individual compounds, which may be within a known range, since the transition metals can assume different oxidation states.
  • the content of these supported metal particles is generally in the range from 1 to 80% by weight, preferably 5 to 60% by weight and more preferably 10 to 50% by weight, without any intention that this should impose a restriction.
  • the particle size of the support especially the size of the carbon particles, is preferably in the range from 20 to 1000 nm, especially 30 to 100 nm.
  • the size of the metal particles present thereon is preferably in the range from 1 to 20 nm, especially 1 to 10 nm and more preferably 2 to 6 nm.
  • the sizes of the different particles are averages and can be determined by means of transmission electron microscopy or x-ray powder diffractometry.
  • the catalytically active layer may comprise customary additives. These include fluoropolymers, for example polytetrafluoroethylene (PTFE), proton- conducting ionomers and surface-active substances.
  • PTFE polytetrafluoroethylene
  • the weight ratio of fluoropolymer to catalyst material comprising at least one noble metal and optionally one or more support materials is greater than 0.1 , this ratio preferably being in the range from 0.2 to 0.6.
  • the catalyst layer has a thickness in the range from 1 to 1000 ⁇ , especially from 5 to 500 pm, preferably from 10 to 300 pm. This value is an average which can be determined by measuring the layer thickness in the cross section of images obtainable with a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the noble metal content of the catalyst layer is 0.1 to 10.0 mg/cm 2 , preferably 0.3 to 6.0 mg/cm 2 and more preferably 0.3 to 3.0 mg/cm 2 . These values can be determined by elemental analysis of a flat sample.
  • inventive membrane electrode assemblies are obvious to those skilled in the art.
  • the different constituents of the membrane electrode assembly are placed one on top of another and bonded to one another by pressure and temperature.
  • lamination is effected at a temperature in the range from 10 to 300°C, especially 20 to 200°C, and with a pressure in the range from 1 to 1000 bar, especially from 3 to 300 bar.
  • the finished membrane electrode assembly (MEA) is ready for operation after cooling and can be used in a fuel cell.
  • the inventive membrane electrode assembly (MEA) is suitable for operation at temperatures above 160°C and enables gaseous and/or liquid fuels, for example hydrogen-comprising gases, which are prepared, for example, in an upstream reforming step from hydrocarbons.
  • the oxidant used may, for example, be oxygen or air.
  • a further advantage of the inventive membrane electrode assembly is that they have a high tolerance to carbon monoxide in operation above 120°C even with pure platinum catalysts, i.e. without a further alloy constituent. At temperatures of 160°C for example, more than 1 % CO may be present in the fuel gas without this leading to any noticeable reduction in the performance of the fuel cell.
  • the inventive membrane electrode assembly can be operated in fuel cells without any need to moisten the fuel gases and the oxidants in spite of the high operating temperatures possible.
  • the fuel cell nevertheless works stably and the membrane does not lose its conductivity. This simplifies the overall fuel cell system and brings additional cost savings since the control of the water circuit (cooling) is simplified.
  • the inventive membrane electrode assembly can be cooled without any difficulty to room temperature and below and then put back into operation, without losing performance.
  • inventive MEAs can be produced in an inexpensive and simple manner.
  • the inventive proton-conducting polymer membrane based on polybenzoxazole- polybenzimidazole block polymers is notable for a considerable improvement in compression resistance.
  • the inventive membranes exhibit a much smaller decrease in thickness at 200°C. For instance, a membrane in the test method described still has a residual thickness of min. 50% after 10 minutes at 200°C, while a comparable membrane based on polyazoles (polybenzimidazole) has only a residual thickness of about 40%.
  • an inventive membrane based on polybenzoxazole-polybenzimidazole block polymers in the test method described, has a residual thickness of min. 40% after 20 minutes at 200°C, while a comparable membrane based on polyazoles (polybenzimidazole) alone has only a residual thickness of less than 30%. More preferably, an inventive membrane based on polybenzoxazole- polybenzimidazole block polymers, in the test method described, has a residual thickness of min. 35% after 60 minutes at 200°C, while a comparable membrane based on polyazoles (polybenzimidazole) alone has only a residual thickness of less than 25%.
  • the conductivity of the membrane depends significantly on the content of acid groups expressed by what is called the ion exchange capacity (IEC).
  • IEC ion exchange capacity
  • a sample with a diameter of 3 cm is punched out and introduced into a beaker filled with 100 ml of water.
  • the acid released is titrated with 0.1 M NaOH.
  • the sample is withdrawn, excess water is dabbed off and the sample is dried at 160°C over 4 h.
  • the dry weight, m 0 is determined gravimetrically with an accuracy of 0.1 mg.
  • the ion exchange capacity is then calculated from the consumption of the 0.1 M NaOH up to the first titration end point, V 1 in ml, and the dry weight, m 0 in mg, by the following formula:
  • the specific conductivity is measured by means of impedance spectroscopy in a 4- pole arrangement in potentiostatic mode using platinum electrodes (wire, diameter 0.25 mm). The distance between the current-collecting electrodes is 2 cm.
  • the resulting spectrum is evaluated with a simple model consisting of a parallel arrangement of an ohmic resistance and a capacitor.
  • the sample cross section of the phosphoric acid-doped membrane is measured immediately before the sample mounting.
  • the test cell is brought to the desired temperature in an oven and regulated by means of a Pt-100 thermocouple positioned in the immediate vicinity of the sample. On attainment of the temperature, the sample is kept at this temperature for 10 minutes before the start of the measurement.
  • the compression resistance is assessed by measuring the decrease in thickness at 200°C ( ⁇ 10°C) by means of a Mitutoyo DC III for a period of 120 minutes.
  • the decrease in thickness in [%] is calculated by [thickness a fter/thickness s tart] x 100.
  • the polymer is first dried at 160°C over 2 h. 100 mg of the polymer thus dried are then dissolved at 80°C in 100 ml of concentrated sulfuric acid (97%) over 4 h. The inherent viscosity is determined from this solution to ISO 3105 (DIN 51562, ASTM D2515) with an Ubbelohde viscometer at a temperature of 25°C.
  • the present invention is illustrated in detail hereinafter by an example and a comparative example, without any intention that this should impose a restriction.
  • a solution comprising 4% by weight of equimolar amounts of 3,3'-dihydroxy-4,4'- diaminobiphenyl and 3,3 ' ,4,4 " -tetraaminobiphenyl (19.76 g) and 15.25 g of terephthalic acid in polyphosphoric acid (116 %) is heated to 240°C within 40 h.
  • the resulting polybenzoxazole-polybenzimidazole-polyphosphoric acid solution is cooled to a temperature of 100°C and applied by means of a manual coating bar to a support in a 450 pm-thick layer and, after cooling, hydrolyzed in 50% by weight phosphoric acid overnight to obtain a self-supporting polybenzoxazole- polybenzimidazole-phosphoric acid membrane.
  • a solution of 2% by weight containing equimolar amounts of 3, 3', 4,4'- tetraaminobiphenyl and terephthalic acid in polyphosphoric acid (112%) is heated to 280°C within 100 h.
  • the resulting polybenzimidazole-polyphosphoric acid solution is cooled to a temperature of 100°C and applied by means of a manual coating bar to a support in a 450 pm-thick layer and, after cooling, hydrolyzed in 50% by weight phosphoric acid overnight to obtain a self-supporting polybenzimidazole-phosphoric acid membrane.

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Abstract

La présente invention concerne des ensembles électrode-membrane améliorés et des piles à combustible à grande longévité, comprenant deux électrodes électrochimiquement actives séparées par une membrane d'électrolyte polymère basée sur des polymères blocs polybenzoxazole-polybenzimidazole.
PCT/IB2013/000874 2012-05-08 2013-05-07 Ensembles électrode-membrane améliorés et piles à combustible à grande longévité WO2013167950A1 (fr)

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WO2022270335A1 (fr) * 2021-06-22 2022-12-29 株式会社デンソー Procédé de production d'une membrane conductrice de protons

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WO2005011039A2 (fr) * 2003-07-27 2005-02-03 Pemeas Gmbh Membrane a conduction de protons et utilisation correspondante
EP2247651A1 (fr) * 2008-02-27 2010-11-10 SOLVAY (Société Anonyme) Composition de polymère, membrane de polymère comprenant la composition de polymère, son procédé de préparation et pile à combustible comprenant la membrane

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US20110318671A1 (en) * 2003-12-30 2011-12-29 Pemeas Gmbh Proton-conducting membrane and use thereof
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022270335A1 (fr) * 2021-06-22 2022-12-29 株式会社デンソー Procédé de production d'une membrane conductrice de protons
JP7552515B2 (ja) 2021-06-22 2024-09-18 株式会社デンソー プロトン伝導膜の製造方法

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