KR20140015141A - Membrane electrode assembly and fuel cells with increased performance - Google Patents

Abstract

The present invention comprises (i) at least two electrochemically active electrodes, (ii) the electrode is separated into at least one polymer electrolyte membrane or electrolyte matrix, and (iii) the electrode is in contact with the aforementioned polymer electrolyte membrane or matrix. (Iv) the catalyst layer relates to a membrane electrode assembly comprising a polymer comprising a repeating unit of formula (I) as ionomer material at a cathode and a fuel cell having improved performance.

Description

Membrane electrode assembly and fuel cells with increased performance

The present invention relates to an improved performance membrane electrode assembly and fuel cell comprising at least two electrochemically active electrodes separated by a polymer electrolyte membrane.

Polymer electrolyte membrane (PEM) fuel cells are already known. Currently, sulfonic acid-modified polymers are already used exclusively as proton-conducting membranes in these fuel cells. Mostly, perfluorinated polymers are used here. DuPont de Nemours, Nation ^TM of Walvington, USA is a well-known example. For the conduction of protons, a relatively high water content in the membrane, typically 4-20 water molecules per sulfonic acid group, is required. The required water content, as well as the stability of the polymer in relation to acidic water and reactive gas hydrogen and oxygen, usually limit the operating temperature of the PEM fuel cell stack to 80-100 ° C. When pressure is applied, the operating temperature may rise above 120 ° C. Otherwise, higher operating temperatures cannot be realized without power loss of the fuel cell.

However, for system specific reasons, fuel cell operating temperatures of 100 ° C. or higher are preferred. The activity of catalysts contained in membrane electrode assemblies (MEA) and based on precious metals is significantly improved at high operating temperatures. When so-called reformers from hydrocarbons are used, in particular the reforming gas contains a significant amount of carbon monoxide which must usually be removed using a gas purification step or sophisticated gas conditioning. The resistance of the catalyst to CO impurities increases at high operating temperatures.

In addition, heat is generated during fuel cell operation. However, cooling these systems below 80 ° C. can be very complex. Depending on the power output, the cooling device can be configured significantly less complicated. This means that the waste heat of a fuel cell system operating at temperatures above 100 ° C. can obviously be used better and therefore the efficiency of the fuel cell system via combined power and heat generators can be increased.

In order to achieve these temperatures, a membrane of a new conduction mechanism is generally used. One approach to this is to use membranes that exhibit electrical conductivity without the use of water. The first promising development in this direction is described in WO 96/13872.

Since the tappable voltage of the individual fuel cells is relatively low, various membrane electrode assemblies (bipolar plates) are generally connected in series and connected to each other through planar separators.

In practice, however, currently available membrane electrode assemblies need to be further refined to become more competitive economic alternatives. One of the necessary improvements is to increase the performance of the membrane electrode assembly with respect to oxygen reduction at the cathode of the membrane electrode assembly.

Accordingly, the present invention provides a fuel cell and a membrane electrode assembly having as high a performance as possible at the cathode of the membrane electrode assembly in which oxygen reduction occurs.

In addition, the improved membrane electrode assembly should preferably have the following characteristics:

Fuel cells should have a long service life.

· The fuel cell should be available as high as possible, especially at operating temperatures above 100 ° C.

During operation, the individual cells should exhibit consistent or improved performance for as long a time as possible.

After a long operating time, the fuel cell should have as high an open circuit voltage as possible as well as a low gas crossover as possible. In addition, they should be able to operate them with as low stoichiometry as possible.

If possible, the fuel cell should be able to operate without additional humidification of the fuel gas.

The fuel cell should be able to withstand the permanent or alternating pressure difference between the anode and the cathode as best as possible.

In particular, fuel cells should be as robust as possible to other operating conditions (T, p, geometry, etc.) to increase general reliability.

In addition, fuel cells should have relatively low gas permeability and improved temperature and corrosion resistance, especially at high temperatures. Especially at high temperatures, reductions in mechanical stability and structural integrity should be avoided as best as possible.

These objects are achieved by the present invention.

The present invention

(i) at least two electrochemically active electrodes,

(ii) the electrode is separated into at least one polymer electrolyte membrane or electrolyte matrix,

(iii) the electrode has a catalyst layer in contact with the aforementioned polymer electrolyte membrane or matrix,

(iv) wherein the catalyst layer comprises at least one ionomer material,

A membrane electrode assembly, characterized in that the catalyst layer in contact with at least the cathode comprises a polymer comprising a repeating unit of formula (I) as an ionomer material.

Wherein (a)

Ar is the same or different and represents a tetravalent covalent aromatic group or a tetravalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic, and also

X is the same or different and represents N, O, S

R ¹ is the same or different and represents a divalent group of the formula:

Ar ¹ , Ar ² are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,

Z ¹ is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and

n is 0.1 to 99.9 mol%, or

Or (b)

Ar is the same or different and represents a tetravalent covalent group of the formula

Ar ³ , Ar ⁴ are the same or different and represent a trivalent covalent aromatic group or a trivalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,

Z ² is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and

X is the same or different and represents N, O, S, and also

R ¹ is the same or different and (i) a divalent group of the formula:

Wherein Ar ⁵ and Ar ⁶ are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,

Z ³ is the same or different and represents N, O, S,

Or (ii) a divalent alkyl group and / or a divalent aromatic group which may be further substituted,

Also

n is 0.1 to 99.9 mol%.

In two alternatives (a) or (b), n is preferably 40 to 60 mol%, most preferably 50 mol%, in which the proportions of the two subunits of the repeating unit are similar or equivalent.

In two alternatives (a) or (b), X preferably represents N or O. In alternative (b) it is preferred that X represents O.

Preferably, the alkyl of Z ¹ and / or Z ² independently of one another is a short-chain divalent alkyl group having 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl or i-propyl and n-, i-, or t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane.

Preferably, the alkyl of Z ¹ and / or Z ² independently of one another is a short-chain divalent alkyl group having 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl or i-propyl and n-, i-, or t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane, wherein at least one carbon atom is perfluorinated or at least one carbon atom is at least one A (CF ₃ )-group, most preferably two (CF ₃ ) -groups, to form a -C (CF ₃ ) ₂ -group.

Preferably, the aromatic groups of Z ¹ and / or Z ² independently represent a divalent aromatic group having 5 to 6 carbon atoms, wherein one or more carbon atoms may be substituted with a heteroatom selected from N, O or S, wherein at least one carbon atom is perfluorinated or at least one carbon atom, at least one of (CF ₃₎ - group, or at least one of (CF ₃₎ - group, and most preferably two (CF ₃₎ - group is substituted Substituted with an alkyl group having 2 to 6 carbon atoms to form a -C (CF ₃ ) ₂ -group or substituted with a terminal -C (CF ₃ ) ₃ group.

Preferably, in alternative (b) R ¹ is independently of each other a divalent alkyl group having 1 to 10 carbon atoms, for example methyl, ethyl, n-propyl or i-propyl and n-, i-, or t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane.

Preferably, in alternative (b) R ¹ represents a divalent aromatic group having 5 to 6 carbon atoms, independently of ^one another, wherein one or more carbon atoms may be substituted by a hetero atom selected from N, O or S .

Preferred divalent covalent aromatic or divalent covalent heteroaromatic groups Ar ¹ , Ar ² , Ar ⁵ , Ar ⁶ are independently monocyclic, bicyclic or polycyclic, condensed having 5 to 20 carbon atoms Or a non-condensed, aromatic or heteroaromatic ring system, wherein one or more carbon atoms may be substituted by N, O, S. The divalent aromatic or divalent heteroaromatic groups Ar ¹ , Ar ² , Ar ⁵ , Ar ⁶ may be substituted by additional radicals.

Most preferred divalent covalent aromatic or divalent covalent heteroaromatic groups Ar ¹ , Ar ² , Ar ⁵ , Ar ⁶ are independently of each other, optionally substituted benzene, naphthalene, biphenyl, diphenylether, di Phenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole , Benzooxadiadiazole, benzooxadiazole, benzopyridine, benzopyrazine, benzopyrazidine, benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolizine, pyridopyridine, imidazopyrimidine , Pyrazinopyrimidine, carbazole, aziridine, phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine, benzopteridine, phenanthroline and phenanthrene.

Preferred trivalent covalent aromatic or trivalent covalent heteroaromatic groups Ar ³ , Ar ⁴ are independently monocyclic, bicyclic, polycyclic, condensed, aromatic or heteroaromatic with 5 to 20 carbon atoms Ring system, wherein one or more carbon atoms may be substituted by N, O, S. The trivalent covalent aromatic or trivalent covalent heteroaromatic groups Ar ³ and Ar ⁴ may be substituted by additional radicals.

Most preferred trivalent covalent aromatic or trivalent covalent heteroaromatic groups Ar ³ , Ar ⁴ are independently of one another, optionally substituted, benzene, naphthalene, biphenyl, diphenylether, diphenylmethane, diphenyldimethyl Methane, bisphenone, diphenylsulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzoxathiadiazole , Benzooxadiazole, benzopyridine, benzopyrazine, benzopyrazine, benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolyzine, pyridopyridine, imidazopyrimidine, pyrazinopyrimidine, Derived from carbazole, aziridine, phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine, benzopteridine, phenanthroline and phenanthrene.

Preferred tetravalent covalent aromatic or tetravalent covalent heteroaromatic groups Ar are independently of each other monocyclic, bicyclic or polycyclic, condensed or uncondensed aromatic or heteroaromatic rings having 5 to 20 carbon atoms System, wherein one or more carbon atoms may be substituted by N, O, S. The tetravalent covalent aromatic or tetravalent covalent heteroaromatic group Ar may be substituted by an additional radical.

Most preferred tetravalent covalent aromatic or tetravalent covalent heteroaromatic groups Ar are independently of one another, optionally optionally substituted benzene, naphthalene, biphenyl, diphenylether, diphenylmethane, diphenyldimethylmethane, bispe Paddy, diphenylsulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzooxatiadiazole, benzooxadidia Sol, Benzopyridine, Benzopyrazine, Benzopyrazidine, Benzopyrimidine, Benzopyrazine, Benzotriazine, Indolizine, Quinolizine, Pyridopyridine, Imidazopyrimidine, Pyrazinopyrimidine, Carbazole, Aziri Derived from dine, phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine, benzulteridine, phenanthroline and phenanthrene.

In a preferred embodiment of the invention, the polymer comprising repeat units of formula (I) has at least 10 repeat units of formula (I), most preferably at least 50 repeat units of formula (I). .

Most preferably, the polymer comprising a repeating unit of general formula (I) has a weight average molecular weight Mw (measured by Gel Permeation Chromatography) of 10000 or more.

Most preferably, the polymer comprising a repeating unit of general formula (I) has a number average molecular weight Mn of 5000 or more.

Most preferably, the polymer comprising repeating units of formula (I) has a solubility of at least 0.5% wt in DMAc at 25 ° C. in a furnace.

The ionomer material according to the invention is preferably located in the catalyst layer of the cathode in a specific proportion to the content of the catalyst material. Typically, the content of the catalyst, most typically the noble metal, in the catalyst bed is 0.1 to 10.0 mg / cm ² , preferably 0.3 to 6.0 mg / cm ² and particularly preferably 1 to 4.0 mg / cm ² . Therefore, the weight ratio of ionomer material to catalyst is preferably from 100: 1 to 1; 100, most preferably from 10: 1 to 1:10. Particularly preferred ratio is 1: 8 to 1: 3. Such contents and ratios may also be applied to the catalyst layer of the anode as necessary.

The polymer including the unit structure of general formula (I) can be produced by the following steps A) and B).

A) At least one aromatic di-, tri- or tetraamino compound is mixed with at least one aromatic carboxylic acid or ester thereof and comprises at least two acid groups per carboxylic acid monomer, wherein at least one di-, tri- or tetraamino compound Or the aromatic carboxylic acid carries at least one fluorine atom / fluorinated, or

One or more aromatic diamino-dihydroxy compounds are mixed with one or more aromatic carboxylic acids or esters thereof, which comprise at least two acid groups per carboxylic acid monomer, wherein the at least one diamino-dihydroxy compound or aromatic carboxylic acid Involving at least one fluorine atom / fluorinated, or

Mixing at least one aromatic and / or heteroaromatic diaminocarboxylic acid, wherein at least one diaminocarboxylic acid is accompanied by at least one fluorine atom / fluorinated,

This is a step of forming a solution and / or dispersion in polyphosphoric acid.

B) preparing a polymer comprising repeating units of formula (I) by heating the mixture of step A) to a temperature of up to 350 ° C., preferably up to 280 ° C. under an inert gas.

The mixture obtained in step B) can be used directly to incorporate a polymer comprising repeating units of the general formula (I) as ionomer in the catalyst layer, in particular in the catalyst layer later contacted with the negative electrode.

As an alternative route, the mixture obtained in step B) can be separated for the first time by precipitating the polymer in a non-solvent such as water or a water-containing medium and drying if necessary. If this route is chosen, the polymer comprising the repeating unit of formula (I) must be dissolved in a solvent, for example DMAc, phosphoric acid or polyphosphoric acid, in order to be incorporated as an ionomer in the catalyst layer, in particular in the catalyst layer in contact with the cathode. .

Proton-conducting polyelectrolyte membranes and matrices

Polymer electrolyte membranes and electrolyte matrices suitable for the purposes of the present invention are each known per se.

In addition to known polymer electrolyte membranes, electrolyte matrices are also suitable. In the context of the present invention, the term "electrolyte matrix" is understood to mean other matrix materials-in addition to the polymer electrolyte matrix, in which the ion-conductive material or mixture is immobilized or treated in the matrix.

In general, a polymer electrolyte membrane including an acid may be used, wherein the acid may be covalently bonded to the polymer. In addition, the plate material may be doped with an acid to produce a suitable film.

Among other methods, these doped films can be expanded with a solution comprising an acidic compound to expand the plate material, for example a polymer film, or to prepare a mixture of the polymer and the acidic compound and then form the film by forming a plate structure and then solidify By forming a film.

Among them, suitable polymers for this purpose are polyolefins such as poly (chloroprene), polyacetylene, polyphenylene, poly (p-xylene). Polyarylmethylene, polystyrene, polymethylstyrene, polyvinyl alcohol, polyvinyl acetate, polyvinyl ether, polyvinyl amine, poly (N-vinyl acetamide), polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone Of polyfluoropyridine, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyhexafluoropropylene, PPTE and hexafluoropropylene, of perfluoropropylvinyl ether, of trifluoronitrosomethane, Copolymers of carvalkoxyperfluoroalkoxyvinyl ether, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyacrolein, polyacrylamide, polyacrylonitrile, polycyanoacrylate, polymetha Krylimide, cycloolefin copolymers, in particular norbornene;

Polymers having CO bonds in the backbone, for example polyacetals, polyoxymethylenes, polyethers, polypropylene oxides, polyepichlorohydrins, polytetrahydrofurans, polyphenylene oxides, polyether ketones, polyesters, in particular poly Hydroxy acetic acid, polyethylene terephthalate, polybutylene terephthalate, polyhydroxybenzoate, polyhydroxypropionic acid, polypivalolactone, polycaprolactone, polymalonic acid, polycarbonate;

Polymers having a C-S bond in the backbone such as polysulfide ether, polyphenylene sulfide, polysulfone, polyethersulfone;

Polymers having CN bonds in the backbone, such as polyimines, polyisocyanides, polyetherimines, polyetherimides, polyanilines, polyaramids, polyamides, polyhydrazides, polyurethanes, polyimides, polyazoles, polyazoles Ether ketones, polyazines;

Liquid crystalline polymers, especially Vectra, as well as

Inorganic polymers such as polysilane, polycarbosilane, polysiloxane, polysilic acid, polysilicate, silicone, polyphosphazene and polythiazyl

.

In this connection, alkali polymers are particularly preferred for application to membranes doped with acids. Almost all known polymer membranes to which protons can migrate are considered as acid-doped alkali polymer membranes. Here, the acid is preferably capable of carrying protons without additional water, for example by the so-called "Grotthus mechanism" method.

As the alkali polymer in the present invention, an alkali polymer having at least one nitrogen atom in the repeating unit is preferably used.

According to a preferred embodiment, the repeating unit of the alkaline polymer comprises an aromatic ring having at least one nitrogen atom. Aromatic rings are preferably 5- or 6-membered rings having one to three nitrogen atoms, which may be combined with other rings, in particular with other aromatic rings.

According to a particular aspect of the present invention, polymers are used that are stable at high temperatures containing at least one nitrogen, oxygen and / or sulfur atom in one repeating unit or in a different repeating unit.

In the context of the present invention, stable at high temperatures means that the polymer can be operated for a long time in a fuel cell at a temperature of 120 ° C. or higher as the polymer electrolyte. Long term means that the membrane according to the invention is described in WO 01/18894 A2 for at least 100 hours, preferably at least 500 hours, at a temperature of at least 80 ° C., preferably at least 120 ° C., particularly preferably at least 160 ° C. Based on the initial performance measured according to, it means that the performance can be operated without a reduction of more than 50%.

The above-mentioned polymers can be used individually or as a mixture (blend). Preference is given here to blends which in particular comprise polyazoles and / or polysulfones. In this context, preferred blend components are polymers modified with polyethersulfones, polyether ketones and sulfonic acid groups as described in WO 02/36249. By using blends, mechanical properties can be improved and material costs can be reduced.

Polyazoles consist of particularly preferred groups of alkali polymers. Polyazole-based alkali polymers are of general formula (I) and / or (II) and / or (III) and / or (IV) and / or (V) and / or (VI) and / or (iii) and / Or (iii) and / or (iii) and / or (iii) and / or (xiii) and / or (xii) and / or (xIII) and / or (xiv) and / or (xV) and / or ( XVI) and / or (iii) and / or (iii) and / or (iii) and / or (iii) and / or (xi) and / or (xII).

Where

Ar is the same or different and represents a tetravalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ¹ is the same or different and represents a divalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ² is the same or different and represents a divalent covalent or trivalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ³ is the same or different and represents a trivalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁴ is the same or different and represents a trivalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁵ is the same or different and represents a tetravalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁶ is the same or different and represents a divalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁷ is the same or different and represents a divalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁸ is the same or different and represents a trivalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ⁹ is the same or different and represents a divalent covalent or trivalent covalent or tetravalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ¹⁰ is the same or different and represents a divalent covalent or trivalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

Ar ¹¹ is the same or different and represents a divalent covalent aromatic or heteroaromatic group, which may be monocyclic or polycyclic,

X is an amino group which is the same or different and carries an oxygen, sulfur or hydrogen atom, a group having 1-20 carbon atoms, preferably branched or unbranched alkyl or alkoxy, or an aryl group as a further functional group.

R is the same or different and under the condition that R in formula (XX) is not hydrogen, hydrogen, an alkyl group and an aromatic group, and n and m are each an integer greater than or equal to 10, preferably an integer greater than or equal to 100, respectively. .

Preferred aromatic or heteroaromatic groups are optionally substituted benzene, naphthalene, biphenyl, diphenylether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulphone, quinoline, pyridine, bipyridine, pyridazine, Pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzooxadiadiazole, benzooxadiazole, benzopyridine, benzopyrazine, benzopyrazidine, benzopyrimidine , Benzopyrazine, benzotriazine, indolizine, quinolysine, pyridopyridine, imidazopyrimidine, pyrazinopyrimidine, carbazole, aziridine, phenazine, benzoquinoline, phenoxazine, phenothiazine, arc Derived from acridizine, benzopteridine, phenanthroline and phenanthrene.

In this case, Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ _, Ar ⁹ , Ar ¹⁰ _, Ar ¹¹ silver It may have any substitution pattern, for example, in the case of phenylene, Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ _, Ar ⁹ , Ar ¹⁰ _, Ar ¹¹ are ortho-phenylene, meta-phenylene And para-phenylene. Particularly preferred groups are also derived from benzene and biphenylene which may be substituted.

Preferred alkyl groups are short-chain alkyl groups having 1 to 4 carbon atoms, for example methyl, ethyl, n-propyl or i-propyl and t-butyl groups.

Preferred aromatic groups are phenyl or naphthyl groups. The alkyl group and the aromatic group 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.

Preferred are polyazoles in which the functional group X of the repeating unit has the same repeating unit of formula (I).

The polyazoles may in theory also have other repeating units, where, for example, functional group X is different. However, it is preferable that the functional group X of the repeating unit is the same.

Further preferred polyazole polymers include polyimidazole, polybenzothiazole, polybenzoxazole, polyoxadiazole, polyquinoxaline, polythiadiazole, poly (pyridine), poly (pyrimidine) and poly (tetraza). Pyrene).

In another embodiment of the invention, the polymer comprising repeating azole units is a blend or copolymer which comprises at least two different units of formulas (I) to (XII). The polymer may be in the form of block copolymers (deblocks, triblocks), random copolymers, periodic copolymers and / or alternating copolymers.

In a particularly preferred embodiment of the invention, the polymer comprising repeating azole units is only a polyazole comprising formulas (I) and / or (II).

The number of repeating azole units of the polymer is preferably an integer equal to or greater than 10. Particularly preferred polymers comprise at least 100 repeating azole units.

Within the scope of the present invention, polymers containing repeat benzimidazole units are preferred. Some examples of the most useful polymers containing repeat benzimidazole units are shown by the following formulae.

Wherein n and m are each an integer greater than or equal to 10, preferably an integer greater than or equal to 100, respectively.

However, the polyazoles used, in particular the polybenzimidazoles, are characterized by high molecular weights. In measuring the intrinsic viscosity, this is preferably at least 0.2 dl / g, more preferably 0.8 to 10 dl / g, in particular 1 to 10 dl / g.

The preparation of such polyazoles is known to react one or more aromatic tetraamino compounds in a melt with one or more aromatic carboxylic acids or esters thereof comprising at least two acid groups per carboxylic acid monomer to form a prepolymer. The prepolymer obtained is solidified in the reactor and then mechanically comminuted. The powdered prepolymer is usually fully polymerized by solid phase polymerization at temperatures up to 400 ° C.

Among them, preferred aromatic carboxylic acids are dicarboxylic and tricarboxylic acids and tetracarboxylic acids or esters thereof or anhydrides thereof or acid chlorides thereof. Likewise the term aromatic carboxylic acid also includes heteroaromatic carboxylic acids.

Preferably, the aromatic dicarboxylic acid is isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N, N-dimethylamino Isophthalic acid, 5-N, N-diethylaminoisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydro Oxyphthalic 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 ( diphenic acid), 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, ben Zophenone-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, 2, 2-bis- (4-carboxyphenyl) hexafluoropropane, 4,4'-stilbendicarboxylic acid, 4-carboxycinnamic acid or C1-C20 alkyl ester or C5-C12 aryl ester or acid anhydride thereof or It is an acid chloride.

The aromatic tricarboxylic acid, tetracarboxylic acid or C1-C20 alkyl ester or C5-C12 aryl ester or acid anhydride thereof or acid chloride thereof is preferably 1,3,5-benzenetricarboxylic acid (trime Food acid), 1,2,4-benzenetricarboxylic acid (trimelitic acid), (2-carboxyphenyl) iminodiacetic acid, 3,5,3'-biphenyltricarboxylic acid or 3,5,4 ' -Biphenyltricarboxylic acid.

The aromatic tetracarboxylic acid or C1-C20 alkyl ester or C5-C12 aryl ester or acid anhydride or acid chloride thereof is preferably 3,5,3 ', 5'-biphenyltetracarboxylic acid, 1, 2,4,5-benzenetetracarboxylic acid, benzophenonetetracarboxylic acid, 3,3 ', 4,4'-biphenyltetracarboxylic acid, 2,2', 3,3'-biphenyltetracar Acid, 1,2,5,6-naphthalenetetracarboxylic acid or 1,4,5,8-naphthalenetetracarboxylic acid.

The heteroaromatic carboxylic acids used are preferably heteroaromatic dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids or esters thereof or anhydrides thereof. Heteroaromatic carboxylic acid is understood to mean an aromatic system comprising at least one nitrogen, oxygen, sulfur or phosphorus atom in an aromatic group. 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 or benzimidazole-5,6-dicarboxylic acid and its C1-C20 alkyl ester or C5-C12 aryl ester or acid anhydride or acid chloride thereof.

The content of tricarboxylic acid or tetracarboxylic acid (based on the dicarboxylic acid used) is 0 to 30 mol%, preferably 0,1 to 20 mol%, in particular 0,5 to 10 mol% .

The aromatic and heteroaromatic diaminocarboxylic acids used are preferably diaminobenzoic acids or their monohydrochloride and dihydrochloride derivatives.

Preferably, at least two different aromatic carboxylic acid mixtures are used. Particularly preferably, in addition to aromatic carboxylic acids, mixtures which also contain heteroaromatic carboxylic acids are used. The mixing ratio of the aromatic carboxylic acid and the heteroaromatic carboxylic acid is 1:99 to 99: 1, preferably 1:50 to 50: 1.

These mixtures are in particular mixtures of N-heteroaromatic dicarboxylic acids and aromatic carboxylic acids. Non-limiting examples of these are isophthalic acid, terephthalic acid, phthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydro Oxyphthalic 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'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, 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 to be.

Among them, preferred aromatic tetraamino compounds are 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1,2,4,5-tetraaminobenzene, 3, 3 ', 4,4'-tetraaminodiphenyl sulfone, 3,3', 4,4'-tetraaminodiphenyl ether, 3,3 ', 4,4'-tetraaminobenzophenone, 3,3', 4,4'-tetraaminodiphenylmethane and 3,3 ', 4,4'-tetraaminodiphenyldimethylmethane as well as salts thereof, in particular monohydrochloride, dihydrochloride, trihydrochloride and tetrahydrochloride derivatives thereof It includes.

Preferred polybenzimidazoles are commercially available under the tradename Celazole.

Preferred polymers include polysulfones, especially polysulfones having aromatic and / or heteroaromatic groups in the backbone. Depending on the particular embodiment of the present invention, the preferred polysulfone and a polyether sulfone is equal to equal to 40 cm ^3/10 min as measured according to ISO 1133 or lower, in particular 30 cm ^3/10 min or lower, and particularly preferably 20 cm ^3/10 min equal to or lower MVR 300 / 21.6 melt to volume ratio. Preferred here is polysulfone with a Vicat softening temperature VST / A / 50 of 180 ° C to 230 ° C. Another preferred embodiment of the invention is that the polysulphone has a number average molecular weight of at least 30,000 g / mol.

Polysulfone-based polymers include, in particular, polymers having repeating units linked with sulfone groups according to the general formulas A, B, C, D, E, F and / or G below.

Wherein the functional groups R, independently of one another, are identical or different and represent aromatic or heteroaromatic groups, these functional groups being described in detail above. These include especially 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 4,4'-biphenyl, pyridine, quinoline, naphthalene, phenanthrene.

Preferred polysulfones within the scope of the present invention include homopolymers or copolymers, for example random copolymers. Particularly preferred polysulfones comprise repeating units of the formulas H to N.

The polysulfones described above are trade names ^? Victrex 200 P ^,? Victrex 720 P ^,? Ultrason E ^,? Ultrason S ^,? Mindel ^,? Radel A ^,? Radel R ^,? Victrex HTA ^,? Astrel and ^? Commercially available under the trade name Udel.

Also particularly preferred are polyether ketones, polyether ketone ketones, polyether ether ketones, polyether ether ketone ketones and polyaryl ketones. These high-performance polymers are known per se and are trade name Victrex ^? PEEK ^{TM ,?} Hostatec ^,? Available commercially as Kadel.

The polysulfones mentioned above, and the polyether ketones, polyether ketone ketones, polyether ether ketones, polyether ether ketone ketones and polyaryl ketones mentioned, are present as alkali polymers and blend components, as already described. Can be. In addition, the aforementioned polysulfones and the aforementioned polyether ketones, polyether ketone ketones, polyether ether ketones, polyether ether ketone ketones and polyaryl ketones can be used in sulfonated form as the polymer electrolyte, wherein The material may also be characterized by alkali polymers, in particular polyazoles, as blend materials. Embodiments which are shown for alkali polymers or polyazoles and which are preferred also apply to these embodiments.

To produce the polymer film, the polymer, preferably the alkali polymer, in particular pyrazole, can be dissolved in an additional step in a polar, aprotic solvent, for example dimethylacetamide (DMAc) and the film can also be used using conventional methods. Can be produced.

In order to remove solvent residues, the film thus obtained can be treated with a washing solution as described in WO 02/07518. Due to the washing of the polyazole film to remove solvent residues described in the aforementioned patent applications, the mechanical properties of the film are surprisingly improved. These properties include in particular the elastic modulus, tear strength and fracture strength of the film.

In addition, the polymer film can be further modified, for example crosslinking as described in WO 02/070592 or WO 00/44816. In a preferred embodiment, the polymer film used comprising the alkali polymer and at least one blend constituent additionally contains a crosslinking agent as described in WO 03/016384.

The thickness of the polyazole film can be in a wide range. Preferably, the thickness of the polyazole film before doping with an acid is in the range of 5 μm to 2000 μm, particularly preferably in the range of 10 μm to 1000 μm; However, this should not be considered a limitation.

In order to obtain proton conductivity, this film is doped with acid. Here, the acid includes all known Lewis and Bronsted acids, preferably the mineral Lewis and Bronsted acids.

It is also possible to use polyacids, in particular isopolyacids and heteropolyacids, as well as mixtures of other acids. Here, in the present invention, heteropolyacids are defined as inorganic polyacids having at least two different central atoms, each of which is a partially mixed anhydride, preferably metals (preferably Cr, MO, V, W) and nonmetals (preferably Forms weak, polybasic oxygen acids of As, I, P, Se, Si, Te). Among them, it includes 12-phosphomolybdatic acid and 12-phospho tungstic acid.

The conductivity of the polyazole film can be influenced by the degree of doping. The conductivity increases with increasing concentration of the dopant until the maximum value is reached. According to the invention, the degree of doping is given in moles of acid per mole of polymer repeating unit. Within the scope of the present invention, a degree of doping between 3 and 50, in particular between 5 and 40, is preferred.

Particularly preferred doping materials are sulfuric acid and phosphoric acid or compounds which release such acids during hydrolysis, for example. Particularly preferred doping material is phosphoric acid (H ₃ PO ₄ ). Here, high concentrations of acid are generally used. According to a particular embodiment of the invention, the concentration of phosphoric acid is at least 50% by weight, preferably at least 80% by weight, based on the weight of the doping material.

Proton-conducting membranes can also be obtained by a method comprising the following steps.

I) dissolving a polymer, in particular polyazole, in phosphoric acid,

II) heating the mixture obtained according to step A) to 400 ° C. under inert gas,

III) forming a film on the support using the polymer solution obtained according to step II) and

IV) treating the film formed in step III) until self-supporting.

In addition, the doped polyazole film can be obtained by a method comprising the following steps.

A) at least one aromatic tetraamino compound is mixed with at least one aromatic carboxylic acid or ester thereof comprising at least two acid groups per carboxylic acid monomer, or a solution of aromatic and / or heteroaromatic diaminocarboxylic acid in polyphosphoric acid and Mixing in the form of a dispersion.

B) forming a layer on the support or electrode using the mixture according to step A)

C) heating the plate structure / layer obtained according to step B) to a temperature of up to 350 ° C., preferably up to 280 ° C., under an inert gas to form a polyazole polymer.

D) treating the resulting membrane of step C) (until becoming self-supporting).

The polyphosphoric acid used in step A) is customary polyphosphoric acid, for example obtained from Riedel-de Haen. The polyphosphoric acid H _{n +2} P _n 0 _{3n +1} (n> 1) usually has a concentration of at least 83% and is calculated by P ₂ 0 ₅ (by calculation method). Instead of the monomer solution, it is also possible to produce dispersions / suspensions.

The mixture produced in step A) has a weight ratio of polyphosphoric acid to the sum of all monomers in the range from 1: 10,000 to 10,000: 1, preferably from 1: 1000 to 1000: 1, in particular from 1: 100 to 100: 1.

The layer formation according to step B) is carried out using a method known per se as known in the prior art of polymer film production (injection, spraying, application with a doctor blade). All supports considered inert under these conditions are suitable as supports. To adjust the viscosity, phosphoric acid (concentrated. Phosphoric acid, 85%) may be added to the solution as needed. Thus, the viscosity can be adjusted to the desired value and the formation of the film can be promoted.

The film produced according to step B) has a thickness of 10 to 4000 μm, preferably 20 to 4000 μm, more preferably 30 to 3500 μm, in particular 50 to 3000 μm.

If the mixture according to step A) also comprises tricarboxylic acid or tetracarboxylic acid, branched / crosslinked-bonds of the resulting polymer are obtained therein. This contributes to the improvement of the mechanical properties. The treatment of the polymer layer produced according to step C) is carried out in the presence of moisture at a temperature for a sufficient time until the layer exhibits sufficient strength for use in the fuel cell. The treatment is carried out to such an extent that the layer is self-supporting and it is possible to separate it from the support without any damage.

According to step C), the plate structure obtained in step B) is heated to a temperature up to 350 ° C, preferably up to 280 ° C and particularly preferably in the range of 200 ° C to 250 ° C. Inert gases used in step C) are known to those skilled in the art. These include not only nitrogen but also inert gases, for example neon, argon, helium.

In another method, the production of oligomers and / or polymers can be obtained in advance by heating the mixture of step A) to a temperature up to 350 ° C., preferably up to 280 ° C. Depending on the temperature and the period selected, it is possible to omit the heating of step C) in whole or in part. This change is also an object of the present invention.

The treatment of the membrane of step D) is carried out at moisture or water and / or steam and / or at temperatures of 0 ° C. and up to 150 ° C., preferably between 10 ° C. and 120 ° C., in particular between room temperature (20 ° C.) and 90 ° C. Or up to 85% in the presence of water-containing phosphoric acid. The treatment is preferably carried out at normal pressure, but may also be carried out with the action of pressure. It is essential that the treatment is carried out by the presence of sufficient moisture, whereby the polyphosphoric acid solidifies the membrane by partial hydrolysis and forms low molecular weight polyphosphoric acid and / or phosphoric acid.

The hydrolysis fluid may be a solution wherein the fluid may also include suspended and / or dispersed components. The viscosity of the hydrolysis fluid may be in a wide range, in which addition of a solvent or an increase in temperature may be done to control the viscosity. The kinematic viscosity is preferably in the range from 0.1 to 10,000 mPa * s, in particular from 0.2 to 2000 mPa * s, wherein these values can be measured according to DIN 53015, for example.

The process according to step D) can be done in any known manner. For example, the membrane obtained in step C) can be immersed in a fluid bath. In addition, the hydrolysis fluid may be sprayed onto the membrane. The hydrolysis fluid may also be injected over the membrane. The latter method has the advantage that the acid concentration of the hydrolysis fluid remains constant during hydrolysis. In practice, however, the first method is usually cheaper.

Oxo acids of phosphorus and / or sulfur include, in particular, phosphinic acid, phosphonic acid, phosphoric acid, hypodiphosphonic acid, hypophosphoric acid, oligophosphoric acid, sulfurous acid, bisulfite and / or sulfuric acid. These acids can be used alone or in mixtures.

In addition, oxo acids of phosphorus and / or sulfur include monomers that can be prepared by free-radical polymerization and include phosphonic acid and / or sulfonic acid groups.

Monomers comprising phosphonic acid groups are known in the art. These are compounds having at least one carbon-carbon double bond and at least one phosphonic acid group. Preferably, the two carbons forming the carbon-carbon double bond have at least two, preferably three bonds in the group causing small steric hindrance of the double bond. Among these, these groups include hydrogen atoms and halogen atoms, in particular fluoro atoms. Within the scope of the present invention, a polymer containing a phosphonic acid group is produced from a polymerization product obtained by polymerization of a monomer containing a phosphonic acid group alone or other monomers and / or crosslinking agents.

The monomer comprising a phosphonic acid group may comprise one, two, three or more carbon-carbon double bonds. In addition, the monomer including a phosphonic acid group may include one, two, three or more phosphonic acid groups.

In general, monomers comprising phosphonic acid groups comprise 2 to 20, preferably 2 to 10 carbon atoms.

Monomers comprising phosphonic acid groups are preferably compounds of the formula.

In this formula,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 aryleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group, wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also be

x represents an integer 1,2,3,4,5,6,7,8,9 or 10

y represents an integer 1,2,3,4,5,6,7,8,9 or 10,

And / or the following formula

In this formula,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 alkyleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group, wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also be

x represents an integer 1,2,3,4,5,6,7,8,9 or 10,

And / or the following formula

In this formula,

A represents the formula COOR ² , CN, CONR ² ₂ , OR ² , and / or R ² , wherein R ² is hydrogen, C 1 -C 15 alkyl group, C 1 -C 15 alkoxy group, ethyleneoxy group or C 5 -C 20 aryl or hetero Aryl group, wherein the above-mentioned functional groups themselves are halogen, -OH, COOZ, -CN, NZ ₂ Can be substituted,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 alkyleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents a hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also

x represents the integer 1,2,3,4,5,6,7,8,9 or 10.

Preferred monomers comprising phosphonic acid groups include, in particular, alkenes comprising phosphonic groups, for example ethenephosphonic acid, propenephosphonic acid, butenephosphonic acid; Acrylic acid compounds and / or methacrylic acid compounds containing phosphonic acid groups, for example 2-phosphonomethylacrylic acid, 2-phosphonomethylmethacrylic acid, 2-phosphonomethylacrylamide and 2-phosphonomethylmethacryl Amides.

Particular preference is given to vinylphosphonic acids (ethenephosphonic acids) which are commercially available, for example available from Aldrich or Clariant GmbH. Preferred vinylphosphonic acids have a purity of at least 70%, preferably at least 90% and particularly preferably at least 97%.

Monomers comprising phosphonic acid groups can also be used in the form of derivatives which can then be converted to acids, wherein the conversion to acids can also take place in the polymerized state. These derivatives include in particular salts, esters, amides and halides of monomers comprising phosphonic acid groups.

In addition, monomers comprising phosphonic acid groups can be introduced into and over the membrane after hydrolysis. This can be done by methods known per se (eg, spraying, dipping, etc.) known to those skilled in the art.

According to a particular aspect of the invention, the ratio of the sum of phosphoric acid, polyphosphoric acid and hydrolysates of polyphosphoric acid and the weight of monomers produced by free-radical polymerization is preferably equal to or greater than 1: 2, in particular 1: Greater than or equal to 1 and particularly preferably equal to or greater than 2: 1.

Preferably, the ratio of the sum of the hydrolysis products of phosphoric acid, polyphosphoric acid and polyphosphoric acid and the weight of the monomers produced by free-radical polymerization ranges from 1000: 1 to 3: 1, in particular 100: 1 to 5: 1 and particularly preferably 50: 1 to 10: 1.

This ratio can be readily determined by conventional methods, in which case in many cases phosphoric acid, polyphosphoric acid and its hydrolysis products can be washed out of the membrane. This gives the weight of the polyphosphoric acid and its hydrolyzate after the hydrolysis of the polyphosphoric acid is completed. In general, this also applies to monomers produced by free-radical polymerization.

Monomers containing sulfonic acid groups are known in the art. These are compounds having at least one carbon-carbon double bond and at least one sulfonic acid group. Preferably, the two carbons forming the carbon-carbon double bond have at least two, preferably three bonds in the group causing a small steric hindrance of the double bond. These groups include, among others, hydrogen atoms and halogen atoms, in particular fluoro atoms. Within the scope of the present invention, a polymer containing a sulfonic acid group is produced from a polymerization product obtained by polymerization of a monomer containing a sulfonic acid group alone or other monomers and / or crosslinking agents.

The monomer comprising a sulfonic acid group may comprise one, two, three or more carbon-carbon double bonds. In addition, the monomer including a sulfonic acid group may include one, two, three or more sulfonic acid groups.

In general, monomers comprising sulfonic acid groups comprise 2 to 20, preferably 2 to 10 carbon atoms.

The monomer comprising a sulfonic acid group is preferably a compound of the formula

In this formula,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 alkyleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group, wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also be

x represents an integer 1,2,3,4,5,6,7,8,9 or 10,

y represents an integer 1,2,3,4,5,6,7,8,9 or 10,

And / or the following formula

In this formula,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 alkyleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group, wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also be

x represents an integer 1,2,3,4,5,6,7,8,9 or 10,

And / or the following formula

In this formula,

A represents the formula COOR ² , CN, CONR ² ₂ , OR ² , and / or R ² , wherein R ² is hydrogen, C 1 -C 15 alkyl group, C 1 -C 15 alkoxy group, ethyleneoxy group or C 5 -C 20 aryl or hetero Aryl group, wherein the above-mentioned functional group itself may be substituted with halogen, -OH, COOZ, -CN, NZ ₂ ,

R represents a bond, a divalent covalent C1-C15 alkylene group, a divalent covalent C1-C15 alkyleneoxy group, for example an ethyleneoxy group, or a divalent covalent C5-C20 aryl or heteroaryl group, wherein The functional groups mentioned may be substituted by halogen, -OH, COOZ, -CN, NZ ₂ ,

Z independently of one another represents hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, an ethyleneoxy group or a C5-C20 aryl or heteroaryl group, wherein the above-mentioned functional groups themselves are substituted with halogen, -OH, -CN Can also be

x represents the integer 1,2,3,4,5,6,7,8,9 or 10.

Preferred monomers containing sulfonic acid groups include, among others, alkenes containing sulfonic groups such as ethenesulfonic acid, propenesulfonic acid, butenesulfonic acid; Acrylic acid compounds and / or methacrylic acid compounds containing sulfonic acid groups such as 2-sulfonomethylacrylic acid, 2-sulfonomethylmethacrylic acid, 2-sulfonomethylacrylamide and 2-sulfonomethylmethacrylamide Include.

Particular preference is given to vinylsulfonic acid (ethenesulfonic acid) which is commercially available, for example available from Aldrich or Clariant GmbH. Preferred vinylsulfonic acids have a purity of at least 70%, preferably at least 90% and particularly preferably at least 97%.

Monomers containing sulfonic acid groups can also be used in the form of derivatives which can then be converted to acids, wherein the conversion to acids can also take place in the polymerized state. These derivatives include especially salts, esters, amides and halides of monomers comprising sulfonic acid groups.

In addition, monomers comprising sulfonic acid groups can be introduced into and over the membrane after hydrolysis. This can be done by methods known per se (eg, spraying, dipping, etc.) known to those skilled in the art.

In other embodiments of the invention, crosslinkable monomers may be used. These monomers can be added to the hydrolysis fluid. In addition, crosslinkable monomers can also be applied to the membrane obtained after hydrolysis.

Crosslinkable monomers are especially compounds having at least two carbon-carbon covalent bonds. Preferred are dienes, trienes, tetraenes, dimethyl acrylates, trimethyl acrylates, tetramethyl acrylates, diacrylates, triacrylates, tetraacrylates.

Especially preferred are dienes, trienes and tetraenes of the formula

Dimethyl acrylate, trimethyl acrylate, tetramethyl acrylate of the formula

Diacrylate, triacrylate, tetraacrylate of the following formula,

Wherein,

R represents a C1-C15 alkyl group, a C5-C20 aryl or heteroaryl group, NR'-SO _{2 ,} PR ', Si (R') ₂ Wherein the above-mentioned functional groups may be substituted by themselves,

R 'independently of one another represent hydrogen, a C1-C15 alkyl group, a C1-C15 alkoxy group, a C5-C20 aryl or a heteroaryl group, and

n is at least 2.

Substituents of the above-mentioned functional groups R are preferably halogen, hydroxyl, carboxy, carboxyl, carboxyester, nitrile, amine, silyl, siloxane groups.

Particularly preferred crosslinking agents are allyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and polyethylene glycol dimethacrylate, 1,3 Butanediol dimethacrylate, glycerol dimethacrylate, diurethane dimethacrylate, trimethylpropane trimethacrylate, epoxy acrylates such as ebacryl, N'N-methylenebisacrylamide, carbi Knol, butadiene, isoprene, chloroprene, divinylbenzene and / or bisphenol A dimethylacrylate. This compound is commercially available from Sartomer Company Exton, Pennsylvania under the names CN120, CN104 and CN980, for example.

The use of a crosslinking agent is optional and the compound can then be used conventionally in the range of 0,05 to 30% by weight, preferably 0.1 to 20% by weight, particularly preferably 1 to 10% by weight, based on the weight of the membrane.

According to a particular aspect of the present invention, monomers comprising phosphonic acid and / or sulfonic acid groups or crosslinked monomers can be polymerized, wherein the polymerization is preferably free-radical polymerization. The formation of radicals may be thermally, photochemically, chemically and / or electrochemically.

For example, a starting solution comprising at least one component capable of forming radicals may be added to the hydrolysis fluid. In addition, the starting solution can be applied to the membrane after hydrolysis. This can be done by methods known per se (eg, spraying, dipping, etc.) known to those skilled in the art.

Among them, suitable radical formers are azo compounds, peroxy compounds, persulfate compounds or azoamidines. Non-limiting examples include dibenzol peroxide, dicumene peroxide, cumene hydroperoxide, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, Dipotassium persulfate, ammonium peroxydisulfate, 2,2'-azobis (2-methylpropionitrile) (AIBN), 2,2'-azobis (amibutyrate isobutyrate) hydrochloride, benzopinacol, di Benzyl derivatives, methyl ethylene ketone peroxide, 1,1-azobiscyclohexanecarbonitrile, methyl ethyl ketone peroxide, acetyl acetone peroxide, dilauryl peroxide, didecanoyl peroxide, tet-butylper 2-ethyl hexanoate, ketone peroxide, methyl isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tet-butylperoxybenzoate, tet-butylperoxyisopro Carbonate, 2,5-bis (2-ethylhexanoylperoxy) -2,5-dimethylhexane, tet-butylperoxy-2-ethylhexanoate, tet-butylperoxy-3,5,5 , -Trimethylhexanoate, tet-butylperoxyisobutyrate, tet-butylperoxyacetate, dicumene peroxide, 1,1-bis (tet-butylperoxy) cyclohexane, 1,1-bis (tet- Butylperoxy) -3,3,5-trimethylcyclohexane, cumyl hydroperoxide, tet-butylhydroperoxide, bis (4-tet-butylcyclohexyl) peroxydicarbonate, and DuPont From the trade names? Vazo, for example? Vazo V50 and? Vazo WS.

It is also possible to use radical formers which form free radicals when exposed to radiation. Preferred compounds include, among others, α, α-diethoxyacetophenone (DEAP, Upjon Corp), n-butyl benzoin ether (? Trigonal-14, AKZO) and 2,2-dimethoxy-2-phenylacetophenone (?). lgacure 651) and 1-benzoyl cyclohexanol (? lgacure 184), bis- (2,4,6-trimethylbenzoyl) phenylphosphine oxide (? lrgacure 819) and 1- [4- (2-hydroxyethoxy ) Phenyl] -2-hydroxy-2-phenylpropan-1-one (? Lrgacure 2959), each of which is commercially available from Ciga Geigy Corp.

Typically, 0.0001 to 5% by weight, in particular 0.01 to 3% by weight (based on the weight of monomers that can be prepared by free-radical polymerization: monomers comprising phosphonic acid groups and / or sulfonic acid groups or crosslinked monomers, respectively) Radical forming agent) is added. The amount of radical former may vary depending on the degree of polymerization desired.

The polymerization can also occur under the action of IR or NIR, respectively (IR = infrared, ie light having a wavelength above 700 nm; NIR = near infrared, ie a wavelength in the range of about 700 to 2000 nm and an energy in the range of about 0.6 to 1.75 eV. With light).

The polymerization may also occur under the action of ultraviolet light having a wavelength of less than 400 nm. This polymerization method is known per se and is described, for example, in Hans Joerg Elias, Makromolekulare Chemie, 5th edition, volume 1, pp. 492-511; DR Arnold, NC Baird, JR Bolton, JCD Brand, PW M Jacobs, P. de Mayo, WR Ware, Photochemistry-An Introduction, Academic Press, New York and MK Mishra, Radical Photopolymerization of Vinyl Monomers, J. Macromol. Sci.-Revs. Macromol. Chem. Phys. C22 (1982-1983) 409.

The polymerization can occur by exposure of β rays, γ rays and / or electron beams. According to a particular aspect of the invention, the membrane is irradiated with a radiation dose in the range of 1 to 300 kGy, preferably 3 to 200 kGy and very particularly preferably 20 to 100 kGy.

The polymerization of the monomers, each comprising a phosphonic acid group and / or a sulfonic acid group or a crosslinked monomer, is preferably at least at room temperature (20 ° C.) to less than 200 ° C., in particular at a temperature between 40 ° C. and 150 ° C., particularly preferably It occurs at 50 ℃ to 120 ℃. The polymerization is preferably carried out at normal pressure, but can also be carried out under the action of pressure. The polymerization causes the solidification of the plate structure, where the solidification can be observed through microhardness measurement. Preferably, the increase in hardness by polymerization is at least 20% relative to the corresponding hardness of the hydrolyzed membrane without polymerization of the monomers.

According to a particular aspect of the present invention, a phosphonic acid group and / or in a polymer obtained by polymerization of a molar sum of phosphoric acid, polyphosphoric acid and hydrolysis products of phosphoric acid and monomers comprising phosphonic acid groups and / or monomers comprising sulfonic acid groups The molar ratio of the number of moles of sulfonic acid groups is preferably equal to or greater than 1: 2, in particular equal to or greater than 1: 1 and particularly preferably equal to or greater than 2: 1.

Preferably, the moles of phosphonic acid groups and / or sulfonic acid groups in the polymer obtained by the polymerization of a molar sum of phosphoric acid, polyphosphoric acid and hydrolysis products of phosphoric acid and a monomer comprising a phosphonic acid group and / or a monomer comprising a sulfonic acid group. The molar ratio of the water is in the range of 1000: 1 to 3: 1, in particular 100: 1 to 5: 1 and particularly preferably 50: 1 to 10: 1.

The molar ratio can be measured by conventional methods. For this purpose in particular spectroscopic methods can be used, for example NMR spectroscopy. In this regard, it should be taken into account that the phosphonic acid group is present in the formal oxidation stage 3 and that the phosphorus in the phosphoric acid, polyphosphoric acid and its hydrolysis products are present in the oxidation step 5 respectively.

According to the preferred degree of polymerization, the plate structure obtained after polymerization is a self-supporting membrane. Preferably, the degree of polymerization is at least 2, in particular at least 5, particularly preferably at least 30 repeat units, in particular at least 50 repeat units, very particularly preferably at least 100 repeat units. The degree of polymerization is determined via the number average molecular weight M _n , measured by the GPC method. Because of the problem of separating the polymer containing phosphonic acid groups contained in the membrane without decomposition, this value is determined using a sample obtained by polymerization of a monomer containing phosphonic acid groups without addition of the polymer. For this reason, the weight ratio of the monomer comprising the starting radical and the phosphonic acid group as compared to the proportion of the membrane product is kept constant. The conversion obtained in the relative polymerization is preferably equal to or greater than 20%, in particular equal to or greater than 40% and particularly preferably equal to or greater than 75% with respect to the use of monomers comprising phosphonic acid groups.

Hydrolysis fluids include water, where the concentration of water is generally not particularly important. According to certain embodiments of the present invention, the hydrolysis fluid comprises 5 to 80% by weight, preferably 8 to 70% by weight and particularly preferably 10 to 50% by weight of water. The water content explicitly included in the oxo acid is not calculated including the water content of the hydrolysis fluid.

Of the above-mentioned acids, phosphoric acid and / or sulfuric acid are particularly preferred, in which these acids comprise in particular 5 to 70% by weight, preferably 10 to 60% by weight and particularly preferably 15 to 50% by weight of water.

Partial hydrolysis of the polyphosphoric acid of step D) leads to solidification of the membrane by sol-gel conversion. It is also related to the reduction of the layer thickness, which is between 15 and 3000 μm, preferably between 20 and 2000 μm, particularly preferably between 20 and 1500 μm; The membrane is self-supporting.

The intramolecular and intermolecular structure (interpenetrating network IPN) present in the polyphosphate layer according to step B) leads to the ordered formation of the membrane of step C), which is responsible for the specific properties of the formed membrane.

The upper temperature limit in the treatment according to step D) is generally 150 ° C. In superheated steam, for example, for extremely short actions of moisture, the steam can also be hotter than 150 ° C. Treatment duration is essential for the upper temperature limit.

Partial hydrolysis (step D) can also occur in environmental test chambers where hydrolysis can be clearly controlled by the action of established moisture. In this regard, the humidity can be set explicitly through the temperature or saturation of the surrounding area in contact with it, for example, a gas such as air, nitrogen, carbon dioxide or other suitable gas, or vapor. The processing period depends on the parameter selected as described above.

In addition, the treatment period depends on the film thickness.

Typically, the treatment period is for example between a few seconds to minutes under the action of superheated steam, or throughout the day, for example at outdoor and low relative humidity at room temperature. Preferably, the treatment period is from 10 seconds to 300 hours, in particular from 1 minute to 200 hours.

If the partial hydrolysis is performed at ambient temperature (20 ° C) with ambient air having a relative humidity of 40-80%, the treatment period is 1 to 200 hours.

The film obtained according to step D) can be formed in such a way as to be self-supporting. That is, it may be removed from the support without any damage and then further processed directly if applicable.

The concentration of phosphoric acid and thus the conductivity of the polymer membrane can be determined through the degree of hydrolysis, ie duration, temperature and ambient humidity. The concentration of phosphoric acid is given in moles of acid per mole of polymer repeating unit. In particular, a membrane of high concentration of phosphoric acid can be obtained by a process comprising steps A) to D). The concentration (mole of phosphoric acid based on the repeating unit of formula (I) such as polybenzimidazole) is preferably 10 to 50, particularly 12 to 40. It is only very difficult or not at all possible to obtain this high doping (concentration) by doping polyazoles with commercially available orthophosphoric acid.

According to a variant of the above described method of producing a polyazole film doped with the use of polyphosphoric acid, the production of these films can then be carried out by a method comprising the following steps;

1) one or more aromatic carboxylic acids or esters thereof, or one or more aromatic carboxylic acids comprising at least two acid groups per carboxylic acid monomer in a melt at a temperature of up to 350 ° C., preferably up to 300 ° C. And / or reacting with heteroaromatic diaminocarboxylic acid,

2) dissolving the solid prepolymer obtained according to step 1) in polyphosphoric acid,

3) heating the solution obtained according to step 2) to a temperature of up to 300 ° C., preferably up to 280 ° C., under an inert gas to form a dissolved polyazole polymer,

4) forming a film on the support using the polyazole polymer solution according to step 3), and

5) treating the film formed in step 4) until self-supporting.

The steps of the method described in items 1) to 5) have been described in detail above in steps A) to D), with reference to particularly preferred embodiments.

Membranes, in particular polyazole based membranes, can be further crosslinked on the surface due to the action of heat in the presence of oxygen in the atmosphere. This curing of the film surface further improves the properties of the film. For this purpose, the membrane can be heated to a temperature of at least 150 ° C, preferably at least 200 ° C and particularly preferably at least 250 ° C. In this step of the process, the oxygen concentration is usually in the range of 5 to 50% by volume, preferably 10 to 40% by volume. However, this should not be regarded as a limitation.

The crosslinking can also occur with the action of IR or NIR, respectively (IR = infrared, ie light having a wavelength of at least 700 nm; NIR = near infrared, ie having a wavelength in the range of about 700-2000 nm and an energy in the range of about 0.6-1.75 eV. light). Another method is β-ray irradiation. In this regard, the dosage is 5 to 200 kGy.

Depending on the degree of crosslinking desired, the crosslinking reaction duration can be within a short range. In general, the reaction time is in the range of 1 second to 10 hours, preferably 1 minute to 1 hour; However, this should not be regarded as a limitation.

Particularly preferred polymer membranes show high performance. The reason is especially improved proton conductivity. It is at least 1 mS / cm, preferably at least 2 mS / cm, particularly preferably at least 5 mS / cm at a temperature of 120 ° C. Here, these values are obtained without wetting. Thus, the membrane must be suitable for producing so-called high temperature, polymer electrolyte membrane fuel cells and high temperature membrane electrode assemblies. The aforementioned high temperature proton conductivity can be either (i) a basic polymeric material or matrix and a polymer with an acid to enable the so-called "Grotthus mechanism" or (ii) a covalent bond to enable the so-called "grotus mechanism". It is achieved by a proton-conducting polymer electrolyte membrane or matrix comprising a. In the latter case this is typically achieved by incorporating at least 10% by weight of the polymer derived from the aforementioned monomers comprising phosphonic acid groups.

Specific conductivity is measured by impedance spectroscopy using a 4-pole arrangement and a platinum electrode (line, 0.25 mm diameter) in the potential potential mode. The spacing between the collecting electrodes is 2 cm. The obtained spectrum is evaluated using a simple model that includes a parallel arrangement of ohmic resistors and a capacitor. The cross section of the membrane sample doped with phosphoric acid is measured immediately before installation of the sample. In order to measure the temperature dependence, the measuring cell is brought to the desired temperature in an oven and controlled using a Pt-100 thermocouple arranged directly near the sample. Once the temperature is reached, the sample is held at that temperature for 10 minutes prior to the start of the measurement.

Gas diffusion layer

The membrane electrode assembly according to the present invention has two gas diffusion layers separated by a polymer electrolyte membrane. Very light, mechanically stable, but not necessarily electrically conductive, mechanically stable materials, including fibers in the form of nonwovens, paper or woven fabrics, for example, are used as starting materials for gas diffusion layers according to the invention. These include, for example, graphite fiber fabric paper which has become conductive by the addition of graphite fiber paper, carbon fiber paper, and carbon black. Through this layer, a well distributed flow of gas and / or liquid is achieved.

The mechanical stabilizing material preferably comprises carbon fiber, glass fiber or fiber comprising an organic polymer, for example polypropylene, polyester (polyethylene terephthalate), polyphenylenesulfide or polyether ketone, to name a few. In this connection, materials having a weight per unit area of less than 150 g / m ² , preferably having a weight per unit area in the range of 10 to 100 g / m ² are particularly suitable.

When using a carbon material as the stabilizing material, nonwovens made of carbonized or graphitized fibers which are weight per unit area in the preferred range are particularly suitable. The use of these materials has two advantages; Firstly they are very light and secondly they have a high open porosity. The porosity of the stabilizing materials preferably used is in the range of 20 to 99.9%, preferably 40 to 99%, and they can be easily filled with other materials so that the hydrophobicity, conductivity and porosity of the processed gas diffusion layer is a direct method. That is, through the entire thickness of the gas diffusion layer.

In general, this layer has a thickness in the range from 80 μm to 2000 μm, in particular from 100 μm to 1000 μm and particularly preferably from 150 μm to 500 μm.

The production of gas diffusion layers or gas diffusion electrodes is described in detail in WO 97/20358, for example. The production method described herein is also part of the present disclosure.

In order to reduce the surface tension, a substance (additive or cleaner) may be added, as described in detail in WO 97/20358. In addition, the hydrophobicity of the gas diffusion layer can be set using perfluorinated polymer with an unfluorinated binder. The mounted gas diffusion layer is then dried and thermally treated, for example, sintered at a temperature of 200 ° C. or higher.

Moreover, it is possible to configure the gas diffusion layer in several layers. In a preferred embodiment of the gas diffusion layer, it has at least two distinct layers. Four layers are considered the upper limit of the multi-layer gas diffusion layer. If more than one layer is used, it is convenient to form an intimate connection between these layers, preferably at high temperatures, by a compression or lamination step. It is possible to create a pre-trimmed layer, and an effective gradient of its hydrophobicity and / or porosity can be set. This gradient can also be caused by several successive coatings or impregnation steps, but in general, impregnation is more sophisticated.

According to certain embodiments, at least one gas diffusion layer may be comprised of a compressible material. Within the scope of the present invention, the compressible material exhibits the property that the gas diffusion layer can be compressed to half, preferably one third of its original thickness, without losing its integrity.

The gas diffusion layer according to the invention is cm ² It has a low electrical surface resistivity in the range of less than 100 mOhm per sugar, preferably less than 60 mOhm per cn ² .

This property is generally manifested by a gas diffusion layer made of graphite fibers and / or graphite paper which has become conductive by the addition of carbon black. The gas diffusion layer also optimizes mass transfer properties and their hydrophobicity by the addition of additional materials. In this regard, the gas diffusion layer is mounted with a fluorinated or partially fluorinated material, for example PTFE.

Catalyst bed

The catalyst layer or catalyst layers comprise a material of catalytic activity. These include in particular precious metals of the platinum group, ie Pt, Pd, Ir, Rh, Os, Ru, or also precious metals silver and gold. In addition, alloys of all the above-mentioned metals may also be used. In addition, the at least one catalyst layer may comprise alloys of platinum group elements and non-noble metals such as Fe, Co, Ni, Cr, Mn, Zr, Ti, Ga, V, and the like. In addition, oxides of the above-mentioned noble metals and / or non-noble metals may also be used.

Catalytically active particles comprising the abovementioned materials can be used as metal powders, in particular platinum and / or platinum alloy powders, so-called black noble metals. Such particles generally have a size in the range of 5 nm to 200 nm, preferably 7 nm to 100 nm. So-called nanoparticles are also used.

In addition, the metal can also be used as a support material. Preferably, this support comprises carbon, graphite or graphitized carbon black which can be used in particular in the form of carbon black. In addition, electrically conductive metal oxides such as SnO _{x ,} TiO _X , Or phosphates such as FePO _x , NbPO _x , Zr _y (PO _x ) _z can be used as support material. In this regard, the indices x, y and z refer to the oxygen or metal content of the individual compounds, which may be located within a range known to be able to present transition metals in other oxidation steps.

The content of such metal particles in the support is generally in the range of 1 to 80% by weight, preferably 5 to 60% by weight and particularly preferably 10 to 50% by weight, based on the total weight of the support and the metal. . However, this does not constitute a limitation. The particle size of the support, in particular the size of the carbon particles, is preferably in the range from 20 to 1000 nm, in particular 30 to 100 nm. The size of the metal particles present therein is preferably in the range from 1 to 20 nm, in particular from 1 to 10 nm and particularly preferably from 2 to 6 nm.

The size of the other particles is averaged and can be measured by transmission electron microscopy or X-ray powder diffractometry.

The catalytically active particles described above can generally be obtained commercially.

In addition to catalysts or catalyst particles already commercially available, it is also possible to use platinum-containing alloys, in particular catalyst nanoparticles made on the basis of Pt, Co and Cu or pt, Ni and Cu, respectively, wherein the particles of the outer shell are High Pt content These particles are described in P. Strasser et al. in Angewandte Chemie 2007.

In addition, the catalytically active layer may comprise conventional additives. Among them, this includes, for example, fluoropolymers such as polytetrafluoroethylene (PTFE), proton-conducting ionomers and surface-active materials.

According to certain embodiments of the invention, the weight ratio of fluoropolymers to catalyst material comprising at least one precious metal and optionally one or more support materials is at least 0.1, and this ratio is preferably in the range of 0.2 to 0.6. have.

According to a particular embodiment of the invention, the catalyst layer has a thickness in the range from 1 to 1000 μm, in particular from 5 to 500, preferably from 10 to 300 μm. This value represents the mean value and can be measured using a cross-sectional image of the layer obtained with a scanning electron microscope (SEM).

According to certain embodiments of the present invention, the precious 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 particularly preferably 1 to 4.0 mg / cm ² . This value is determined by component analysis of the plate sample.

The ionomer material according to the invention is preferably present in the catalyst layer of the cathode in a specific proportion relative to the content of the catalyst material. Therefore, the weight ratio of ionomer material to catalyst is preferably 100: 1 to 1: 100, most preferably 10: 1 to 1:10. Specific ratios are preferably 1: 8 to 1: 3. If desired, such amounts and ratios may also be applied to the catalyst layer of the anode.

The catalyst layer is generally not self-supporting but is usually applied to gas diffusion layers and / or membranes. In this regard, part of the catalyst layer may for example diffuse into the gas diffusion layer and / or the membrane, resulting in the formation of a conversion layer. This may also cause the catalyst layer to be understood as part of the gas diffusion layer. The thickness of the catalyst layer is obtained by measuring the thickness of the layer to which the catalyst layer is applied, for example the gas diffusion layer or the membrane, the measurement being the sum of the catalyst layer and the corresponding layer, for example the sum of the gas diffusion layer and the catalyst layer. to provide. The catalyst layer is preferably characterized by a gradient, ie the content of the noble metal increases in the direction of the membrane while the content of hydrophobic material acts in reverse.

Further information of membrane electrode assemblies is mentioned in the technical literature, in particular in patent applications WO 01/18894 A2, DE 195 09 748, DE 195 09 749, WO 00/26982, WO 92/15121 and DE 197 57 492. The description including the above-mentioned documents regarding the structure and formation of the electrode, gas diffusion layer and catalyst as well as the membrane electrode assembly selected is part of this specification.

Gasket

The gaskets generated or used within the scope of the process according to the invention are each produced and applied in separate steps or are generated directly at the circumferential edge of the gas diffusion layer and the circumferential, optionally raised edge of the bipolar plate.

In this connection, the gasket structurally formed in the inner edge region overlaps with the inside, and therefore it is essential to overlap with the outer edge region of the gas diffusion layer providing the gas diffusion layer or catalyst layer. This overlap allows the gas diffusion layer to be anchored to the bipolar plate, thereby eliminating additional positioning or anchoring frames. In addition, it is no longer necessary for the edge region of the gas diffusion layer to be interspersed with the sealant or for the sealant to penetrate into the edge region of the gas diffusion layer in order to obtain a sealing function.

It is also advantageous that the gasket retains sufficient mechanical properties and / or integrity so that in subsequent compression steps, for example, the gas diffusion layer and / or the membrane / electrolyte matrix are not damaged. For this purpose, a so-called hard stop function can be integrated in the gasket in an advantageous way. This embodiment is particularly preferred when the gasket can be produced in a bipolar plate without raised edges.

The production of the gasket can be carried out in separate steps or the gasket can be made directly at the circular edge of the gas diffusion layer on the side of the bipolar plate. The production of the gaskets can be carried out by all known methods, preferably by crosslinking them by spray application or application and / or printing methods of thermoplastic elastomers or crosslinkable polymers.

Preferably, the gaskets according to the invention are produced in the form of polymers which are soluble or can be thermally produced.

Among the rubbers, silicone rubber (Q), ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), isobutylene-isoprene rubber (IIR), butadiene rubber (BR), styrene-butadiene rubber ( SBR), styrene-isoprene rubber (SIR), isoprene-butadiene rubber (IBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), acrylate rubber (ACM) and / or Partially hydrogenated rubber from butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene-butadiene rubber (IBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), polyisobutylene rubber ( PIB), fluoro rubbers (FPM), fluorosilicone rubbers (MFQ, FVMQ) are preferred.

Fluoropolymers are also used as sealing materials, preferably poly (tetrafluoroethylene-co-hexafluoropropylene) FEP, polyvinylidene fluoride PVDF, perfluoroalkoxy polymer PFA and poly (tetrafluoroethylene- co-perfluoro (methylvinyl ether) MFA Such polymers are commercially available in many ways, for example under the trade names Hostafon®, Hyflon®, Teflon®, Dyneon® and Nowoflon®.

In addition to the materials mentioned above, sealants based on polyimides can also be used. Polymers based on polyimides include not only imide groups as constituents of the skeleton, but also polymers containing amide (polyamideimide), ester (polyesterimide) and ether group (polyetherimide).

Preferred polyimides have repeating units of formula (VI).

(Ⅵ)

(Ⅵ)

Wherein the functional group Ar has the above meaning and the functional group R represents an alkyl group or a divalent covalently aromatic or heteroaromatic group of 1 to 40 carbon atoms. Preferably, functional group R is benzene, naphthalene, biphenyl, diphenyl ether, diphenyl ketone, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulfone, quinoline, pyridine, Divalent covalently aromatic or heteroaromatic groups derived from bipyridine, anthracene, thiadiazole and phenanthrene. The index n suggests that the repeat unit represents part of the polymer.

Such polymers are commercially available under the trade names Dupont's Kapton, Vespel, Toray and Pyralin as well as GE Plastics 'Ultem and Ube Industries' Upilex.

Combinations of the above mentioned materials having the properties of a strong / weak combination are also preferred as seals, especially when the above mentioned hard stop fuction is integrated.

Particularly preferred seals have a Shore A hardness of 5 to 85, in particular 25 to 80. The shore hardness is determined according to DIN 53505. It is also useful when the permanent set of sealant is 50% or less. The permanent set is determined according to DIN ISO 815.

The thickness of the gasket is influenced by several factors. The main factor is how high the height of the boundary area of the bipolar plate is chosen. Usually, the thickness of the gasket produced or applied is from 5 μm to 5000 μm, preferably from 10 μm to 1000 μm and in particular from 25 μm to 150 μm. Especially for bipolar plates without raised border areas, the thickness can also be higher.

The gasket may also consist of various layers. In this embodiment, the different layers are connected to each other using suitable polymers, in particular fluoropolymers being very suitable for forming aqueous bonds. Suitable fluoropolymers are known to those skilled in the art. Among them, it includes polytetrafluoroethylene (PTFE) and poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP). The layer made of fluoropolymers present above the sealing layer generally has a thickness of at least 0.5 μm, preferably at least 2.5 μm. If expandable fluoropolymers are applied, the thickness of the layer may be between 5 and 250 μm, preferably between 10 and 150 μm.

Thus, the gasket or seal described above fixes the gas diffusion layer of the recess formed with the bipolar plate. For this purpose, it is useful when the gasket overlaps the circular outer boundary region of the gas diffusion layer. The overlap of the boundary region of the gas diffusion layer and the gasket is preferably 0,1 to 5 mm, preferably 0.1 to 3 mm, based on the outermost edge of the gas diffusion layer. More overlap is possible, but causes a strong loss of catalytically active surface. For this reason, the degree of overlap must be adjusted in a critical way so that an unnecessary excess of the catalytically active surface is covered.

Although it is useful when the gasket overlaps the circular outer boundary region of the gas diffusion layer, nevertheless there is a discontinuous overlap of the circular sealed edges of the gas diffusion layer boundary region, in particular with respect to the active catalyst surface. For this reason, it is essential that the fixing function of the gas diffusion layer is reliably maintained through the gasket.

Bipolar plate

Bipolar plates or also separate plates used within the scope of the present invention are typically produced in a channel (flow field channel) process to enable the distribution of reactants and other fluids common in fuel cells, for example cooling fluids.

The bipolar plate is usually produced from an electrically conductive material; These may be metallic or non-metallic materials.

If the bipolar plate consists of a non-metallic material, so-called composites are preferred. The composite material is a joint made of a matrix material provided with an electrically conductive filler. Polymeric materials, particularly preferably organic polymers, are suitable as matrix materials. Depending on the operating temperature of the fuel cell, high performance polymers, in particular thermally stable polymers, are also required. Depending on the area of use, polymers are used having a long term use temperature of at least 80 ° C, preferably at least 120 ° C, particularly preferably at least 180 ° C.

Thermoplastics, in particular polypropelin (PP), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS) and liquid polymers (LCP) are particularly preferably used, and these It is also possible to use a mixture of ie, a mixture of different polymers and ordinary additives. In addition to thermoplastic resins, thermosetting polymers and resins are also preferred. In particular, phenol resins (PF), melamine resins (MF), polyesters (UP) and epoxy resins (EP) are used.

Particulate materials are used as electrically conductive fillers which allow as uniform distribution as possible in the matrix. Preferably, such fillers have a bulk conductivity of at least 10 6 mS / cm. Carbon, graphite and carbon black are particularly preferably used. They can also be treated to obtain better weettabilbity in the matrix material. The particle size is not subject to any particular limitation, but it must be possible to produce such a bipolar plate. Except for the above-mentioned electrically conductive fillers, additives for further improving the application properties may be added in the matrix material. Fiber reinforcement is also possible, especially if mechanical loads cannot be guaranteed in other ways.

Such bipolar plate production is preferably carried out by suitable production methods, in particular by injection embossing and embossing techniques as well as injection molding techniques.

Except for the production of intermediate ducts, the bipolar plate also has further ducts or openings or bores, for example, through which coolant or reactant gas can be supplied or discharged. Can be.

The thickness of the non-metallic bipolar plate is preferably in the range of 0.3 to 10 nm, in particular in the range of 0.5 to 5 nm and particularly preferably in the range of 0.5 to 2 nm. The conductivity of the nonmetallic bipolar plate is greater than or equal to 25 S / cm.

If the bipolar plate is made of metallic material, a more cost effective integrated design is possible. The structure of this metallic bipolar plate is not subject to any substantial limitations. It is preferred that the metallic material consist of nickel based alloys as well as those based on corrosion and acid resistant irons, in particular V2A and V4A iron. Further plate or coated metals are preferred, in particular they have a corrosion resistant surface consisting of precious metals, nickel, ruthenium, niobium, tantalum, chromium, carbon, as well as metals coated with ceramic materials, in particular CrN, TiN, TiAN, Complex nitrides, carbonides, silicon nitride coated and metal oxides and transition metals.

Apart from these, the metallic bipolar plate may additionally have such a coating, which on the one hand reduces the electrical surface resistance in the bonding of the gas diffusion layer / bipolar plate or the chemical and / or of the bipolar plate towards the media present. Or increases physical resistance or is formed in a fuel cell.

The construction of the metallic bipolar plate can be done from the individual plates, ie it is possible to form in a simple way voids for the coolant and reaction medium to be fed or discharged. The connection of the individual plates can be carried out by a material joining method, for example welding or soldering. If desired, the voids are additionally sealed against each other, ie leaks can be avoided due to the additional internal coating.

If a fuel cell system without a cooling layer is constructed, or if each of the multiple cell systems in such a fuel cell stack does not require any cooling, the bipolar plate or individual bipolar plates of the stack may also be from only one metallic or nonmetallic individual plate. Can be prepared.

The production and construction of suitable metallic bipolar plates is described in detail in DE-A-10250991, WO 2004/036677, WO 2004/105164, WO 2005/081614, WO 2005/096421 and WO 2006/037661. The conjugates and production methods described herein are also part of the present invention and specification.

The thickness of the metallic bipolar plate is preferably in the range of 0.03 to 1 mm, in particular in the range of 0.05 to 0.5 mm and particularly preferably in the range of 0.05 to 0.15 mm.

The bipolar plate used within the scope of the present invention has a region of raised boundaries so that the region of the bipolar plate comprising flow field channels forms a recess. The exact altitude of the boundary region relative to the highest height of the region of the bipolar plate with the intermediate channel produced is adjusted according to the thickness of the gas diffusion layer, including the gas diffusion layer or catalyst layer. If the gas diffusion layer of the gas diffusion layer or catalyst layer is not subjected to any further compression during the subsequent compression step, the height of the boundary region of the bipolar plate corresponds to the thickness of the gas diffusion layer including the gas diffusion layer or catalyst layer.

If the thickness of the gas diffusion layer, including the gas diffusion layer or catalyst layer, is greater than the height of the boundary region for the highest height region of the bipolar plate with the intermediate duct manufactured, compression of the gas diffusion layer occurs during the subsequent compression step. do. The degree of compression is determined by the thickness and formability of the seal and the seal acts as a hard stop. This embodiment is particularly useful when a soft or easily shaped polymer electrolyte membrane is used to avoid damaging the membrane.

It is known that it is useful to design the height of the frame-shaped component or the height of the boundary region in such a way that the gas diffusion layer, including the gas diffusion layer or catalyst layer, experienced at least 3% compression compared to the original thickness. . Particularly preferably, the height of the boundary region described above is chosen and the compression is at least 5%. It is also possible that at least 50% compression, in particular at least 30% compression, is selected as the upper limit and exceeding it through the selection of other parameters.

Compression of the components is carried out under the action of pressure or temperature and a close connection between the components is formed. In general, this is carried out at temperatures in the range from 10 to 300 ° C., preferably at temperatures in the range from 20 ° C. to 200 ° C. and at 1 to 1000 bar, in particular from 3 to 300 bar. The above-mentioned compression may also occur during the production of the stack and / or the fuel cell stack initiation.

Thereafter, the electrochemical cell, in particular the fuel cell individual cell, can be operated and used. To produce a fuel cell stack, the individual cells on which the fuel cell is based are arranged in a stack. In addition, the production of the fuel cell stack can be carried out using semi-finished parts according to the invention, and it is possible to provide them in advance of the required membrane. In this regard, the membranes are first available as rolled products and can be cut, for example, with a minimum of material to suit individual bipolar plate designs. You do not need to add any handling frame. The production of fuel cell stacks from individual cells for fuel cells is generally known.

The electrode and membrane electrode assembly according to the present invention, as described in the following examples, provide a polymer containing both an imino group and fluorine, which enable phosphoric acid adsorption. When it is used as ionomer coated on the electrode, the provision of a significantly high oxygen reduction current is obtained. Thus, the decrease in the overvoltage of the electrode is seen, and the voltage of the fuel cell decreases. Without the incorporation of certain scientific models, this effect can be explained by the fact that the inclusion of fluorine in the polymer structure increased its oxygen solubility. In the present invention, it is clear that the method of coating or adding such a fluorine-containing polymer to the cathode is an effective measure for improving the performance of the fuel cell.

Polymer Manufacturing Process

Polymer 1: Polybenzimidazole (PBI)

Poly (2,2'-m-phenylene-5,5'-bibenzimidazole) from BASF Fuel Cell GmbH was used as the basic polymer for comparison.

Polymer 2: Fluorine-Containing Polymer 1

4,4 '-(hexafluoroisopropylidene) dibenzoic acid represented by Formula 1 was used as the dicarboxylic acid, and 3.3'-diaminobenzidine tetrahydrochloride represented by Formula 2 was used as a monomer containing an amino group. It was.

Under nitrogen atmosphere, using polyphosphoric acid (117% phosphoric acid) as the reaction solvent, the reaction took place at 170 ° C. for 12 hours and further at 220 ° C. for 90 hours. The reaction mixture became high viscosity.

The mixture was poured into a large amount of water and the precipitate was recovered by filtration. The precipitate was placed in boiling water and refluxed for 24 hours to remove the polyphosphate solvent. IR spectroscopy shows the imino (C = N), and the absorption of the imidazole ring at 3400-2600cm ^-1 at 1633cm ^-1, which was confirmed by the molecular structure 1.

Molecular mass was measured by GPC (gel permeation chromatography) using PEO as internal reference. Based on the said measurement result, the number average molecular weight Mn was 6.0x10 <^4> and the weight average molecular weight Mw was 31x10 <^4> .

This polymer was dissolved in organic solvents such as dimethyl acetamide and NMP (N-methylpyrrolidone).

5% by weight of the polymer solution was sprinkled onto the glass plate, the solvent was removed by heating, and finally a strong brown film was obtained. Immersion in 85% phosphoric acid at 40 ° C. for one hour confirmed that the film was converted to a gel film containing 75-80% by weight phosphoric acid.

Polymer 3: Fluorine-Containing Polymer 2

4,4'-oxybis [benzoic acid] represented by Formula 3 was used as the dicarboxylic acid, and 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane dihydro represented by Formula 4 Chloride was used as a monomer containing an amino group.

Under nitrogen atmosphere, using poly phosphoric acid (117% phosphoric acid) as the reaction solvent, the reaction took place at 170 ° C. for 4 hours and further at 203 ° C. for 34 hours. The reaction mixture became high viscosity.

The mixture was poured into a large amount of water and the precipitate was recovered by filtration. The precipitate was placed in boiling water and refluxed for 24 hours to remove the polyphosphate solvent. IR spectroscopy is an imino group (C = N), and 3400-2600cm at 1599cm ^{-1 -} shows ^one imidazole ring and COC absorption at 1246cm ^-1 in, which was confirmed by the molecular structure 2.

Molecular mass was measured by GPC (gel permeation chromatography) using PEO as internal reference. Based on the said measurement result, number average molecular weight Mn was 0.57x10 <^4> and the weight average molecular weight Mw was 1.7x10 <^4> .

This polymer was dissolved in organic solvents such as acetoamide and NMP (N-methylpyrrolidone).

5% by weight of the polymer solution was sprinkled onto the glass plate and the solvent was removed by heating, and finally a brown hard film was obtained. Immersion in 85% phosphoric acid at 40 ° C. for one hour confirmed that the film was converted to a gel film containing 50-60 wt% phosphoric acid.

Polymer 4: Fluorine-Containing Polymer 3

Sebacic acid represented by the formula (5) was used as the dicarboxylic acid, and 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane dihydrochloride represented by the formula (6) was used as the amino group. Used as monomer included

Under nitrogen atmosphere, using polyphosphoric acid (117% phosphoric acid) as the reaction solvent, the reaction took place at 130 ° C. for 1 hour, and further at 180 ° C. for 24 hours. The reaction mixture became high viscosity.

The mixture was poured into a large amount of water and the precipitate was recovered by filtration. The precipitate was placed in boiling water and refluxed for 24 hours to remove the polyphosphate solvent. IR spectroscopy is an imino group (C = N), and 3400-2600cm at 1629cm ^{-1 -} giving already show the absorption of the imidazole ring in the ^first, which was confirmed by the molecular structure 3.

This polymer was dissolved in organic solvents such as dimethyl acetamide and NMP (N-methylpyrrolidone).

5% by weight of the polymer solution was sprinkled onto the glass plate, the solvent was removed by heating, and finally a brown hard film was obtained. Immersion in 85% phosphoric acid at 40 ° C. for one hour confirmed that the film was converted to a gel film containing 70-75 wt% phosphoric acid.

(2)

Formula 1

Molecular Structure 1

(3)

Formula 4

Molecular Structure 2

Formula 5

Molecular Structure 3

Electrochemical measurement

a) electrode manufacturing

In order to measure the electrochemical oxygen reduction activity of the electrode comprising the polymer described above, half cell measurement was performed.

Porous Pt-carbon electrodes containing 0.5 mg / cm ² of Pt were used as reference and counter electrodes. Phosphoric acid doped polybenzimidazole membrane (80% wt using 85% phosphoric acid) was used as electrolyte. The working electrode is a Pt mesh electrode (1 cm ²⁾ Geometric regions) were prepared by dipping into dimethyl acetamide solvents, each having 3 to 5 wt% of polymer and then evaporating the solvent. The resulting polymer coating was quantified in Table 1.

Platinum Coating Volume
[mg / cm ² ] Polymer coating amount
[mg / cm ² ] Pt-mesh 3.5 ---- Pt-Mesh / Polymer 1
(PBI) 3.7 0.8 Pt-Mesh / Polymer 2 3.0 0.7 Pt-Mesh / Polymer 3 3.6 0.6 Pt-Mesh / Polymer 4 3.9 0.8

Table 1: Polymer weight coated on working electrode

b) electrochemical measurements

Electrochemical measurements were performed by pressurizing the working electrode between the two graphite plates, including the counter / reference electrode, the PBI membrane with acid and the gas inlet / exhaust. The measurement was carried out at 140 ° C. The counter / reference electrode was subsequently purged with hydrogen.

The working electrode was continuously purged with 0.4 L / min of pure oxygen or air (high flow rate to ensure gas utilization is close to zero). The activity of the electrode at 0.7 V and 140 ° C. (ambient pressure) is summarized in Table 2.

Pure O ₂
I at 0.7 V [mA / cm ² ] air
I at 0.7 V [mA / cm ² ] Pt-mesh 0.80 0.20 Pt-Mesh / Polymer 1
(PBI) 0.67 0.13 Pt-Mesh / Polymer 2 2.03 0.32 Pt-Mesh / Polymer 3 1.59 0.36 Pt-Mesh / Polymer 41 6.14 1.35

Table 2: Oxygen Reduction Activity of Electrodes According to the Invention (Note that the reduction current is indicated by the anodic current in this table)

Claims (18)

(i) at least two electrochemically active electrodes
(ii) the electrode is separated into at least one polymer electrolyte membrane or electrolyte matrix,
(iii) the electrode has a catalyst layer in contact with the aforementioned polymer electrolyte membrane or matrix,
(iv) wherein the catalyst layer comprises at least one ionomer material,
A membrane electrode assembly, characterized in that the catalyst layer in contact with at least the cathode comprises a polymer comprising repeating units of the general formula (I) as ionomer material;

Wherein (a)
Ar is the same or different and represents a tetravalent covalent aromatic group or a tetravalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic, and also
X is the same or different and represents N, O, S
R ¹ is the same or different and represents a divalent covalent group of the formula:

Ar ¹ , Ar ² are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ¹ is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and
n is 0.1 to 99.9 mol%, or
Or (b)
Ar is the same or different and represents a tetravalent covalent bond of the formula

Ar ³ , Ar ⁴ are the same or different and represent a trivalent covalent aromatic group or a trivalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ² is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and
X is the same or different and represents N, O, S, and also
R ¹ is the same or different and (i) a divalent covalent group of the formula:

Wherein Ar ⁵ and Ar ⁶ are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ³ is the same or different and represents N, O, S,
Or (ii) a divalent alkyl group and / or a divalent aromatic group which may be further substituted,
Also
n is 0.1 to 99.9 mol%.
2. The membrane electrode assembly of claim 1, wherein in two alternatives (a) or (b) n is 40 to 60 mol%, preferably 50 mol%, in which the proportions of the two subunits of the repeating unit are similar or equivalent. .
2. The membrane electrode assembly of claim 1, wherein in two alternatives (a) or (b) X represents N or O.
2. The membrane electrode assembly of claim 1, wherein in alternative (b) X represents O.
The alkyl of Z ¹ and / or Z ² is independently a short-chain divalent alkyl group having 1 to 6 carbon atoms, preferably methyl, ethyl, n-propyl or i-propyl and n-. Membrane electrode assembly which represents i-, or t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane.
The compound of claim 1, wherein the alkyl of Z ¹ and / or Z ² independently of one another is a short-chain divalent alkyl group having 1 to 6 carbon atoms, most preferably methyl, ethyl, n-propyl or i-propyl and n-, i-, or t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane, wherein at least one carbon atom is perfluorinated or at least one carbon atom Membrane electrode assembly substituted with at least one (CF ₃ ) -group, preferably two (CF ₃ ) -groups, to form a -C (CF ₃ ) ₂ -group.
^2. The aromatic group of claim 1, wherein the aromatic groups of Z ¹ and / or Z ² independently represent a divalent aromatic group having 5 to 6 carbon atoms, wherein one or more carbon atoms may be substituted with a heteroatom selected from N, O or S Wherein at least one carbon atom is perfluorinated or at least one carbon atom is at least one (CF ₃ ) -group, or at least one (CF ₃ ) -group, most preferably two (CF ₃ ) -groups A membrane electrode assembly substituted with an alkyl group having 2 to 6 carbon atoms substituted to form a -C (CF ₃ ) ₂ -group or substituted with a terminal -C (CF ₃ ) ₃ group.
The process according to claim 1, wherein in alternative (b) R ¹ is independently of each other a divalent alkyl group having 1 to 10 carbon atoms, preferably methyl, ethyl, n-propyl or i-propyl and n-, i- Or a membrane electrode assembly representing t-butyl, n-, i-, or t-pentane, n-, i-, or t-hexane.
The compound of claim 1, wherein in alternative (b) R ¹ independently represent a divalent aromatic group having 5 to 6 carbon atoms, wherein at least one carbon atom is to be substituted by a hetero atom selected from N, O or S Membrane electrode assembly.
The divalent covalent aromatic or divalent covalent heteroaromatic group Ar ¹ , Ar ² , Ar ⁵ , Ar ⁶ is independently monocyclic, bicyclic or polycyclic, condensed or non-condensed. , Aromatic or heteroaromatic ring systems having from 5 to 20 carbon atoms, wherein at least one carbon atom may be substituted by N, O, S, and also said divalent covalent aromatic or divalent covalent heteroaromatic group Ar ¹ , Ar ² , Ar ⁵ , Ar ⁶ may be substituted by additional radicals.
The membrane of claim 1 wherein said polymer comprising repeating units of formula (I) has a membrane having at least 10 repeating units of formula (I), more preferably at least 50 repeating units of formula (I). Electrode assembly.
The membrane electrode assembly according to claim 1, wherein the polymer containing a repeating unit of formula (I) has a weight average molecular weight Mw (measured by gel permeation chromatography) of 10000 or more.
The membrane electrode assembly according to claim 1, wherein the polymer containing a repeating unit of formula (I) has a number average molecular weight Mn of 5000 or more.
The membrane electrode assembly according to claim 1, wherein the polymer comprising the unit structure of general formula (I) has a solubility of at least 0.5% wt in DMAc at a temperature of 25 ° C.
The membrane electrode according to claim 1, wherein the weight ratio of ionomer material to catalyst material in the catalyst layer is 100: 1 to 1; 100, preferably 10: 1 to 1:10, most preferably 1: 8 to 1: 3. Conjugate.
2. The membrane electrode assembly of claim 1, wherein the polymer electrolyte membrane or electrolyte matrix has a proton conductivity of at least 1 mS / cm, preferably at least 2 mS / cm, in particular at least 5 mS / cm, at a temperature of 120 ° C. 3.
Use of a polymer comprising repeating units of general formula (I) as ionomer material, preferably ionomer material in the cathode

Wherein (a)
Ar is the same or different and represents a tetravalent covalent aromatic group or a tetravalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic, and also
X is the same or different and represents N, O, S
R ¹ is the same or different and represents a divalent covalent group of the formula:

Ar ¹ , Ar ² are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ¹ is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and
n is 0.1 to 99.9 mol%, or
Or (b)
Ar is the same or different and represents a tetravalent covalent bond of the formula

Ar ³ , Ar ⁴ are the same or different and represent a trivalent covalent aromatic group or a trivalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ² is the same or different and represents a divalent alkyl group and / or a divalent aromatic group, wherein at least one hydrogen atom is substituted with a fluorine atom, and
X is the same or different and represents N, O, S, and also
R ¹ is the same or different and (i) a divalent covalent group of the formula:

Wherein Ar ⁵ and Ar ⁶ are the same or different and represent a divalent covalent aromatic group or a divalent covalent heteroaromatic group, each of which may be monocyclic, bicyclic or polycyclic,
Z ³ is the same or different and represents N, O, S,
Or (ii) a divalent alkyl group and / or a divalent aromatic group which may be further substituted,
Also
n is 0.1 to 99.9 mol%.

A fuel cell comprising at least one membrane electrode assembly as defined in any of claims 1 to 16.