WO2002080296A2

WO2002080296A2 - Electrolyte membrane, membrane electrode units comprising the same, method for the production thereof and specific uses therefor

Info

Publication number: WO2002080296A2
Application number: PCT/EP2002/001549
Authority: WO
Inventors: Volker Hennige; Gerhard HÖRPEL; Christian Hying
Original assignee: Creavis Gesellschaft Für Technologie Und Innovation Mbh
Priority date: 2001-03-30
Filing date: 2002-02-14
Publication date: 2002-10-10
Also published as: DE10115927A1; AU2002246091A1; WO2002080296A3

Abstract

The invention relates to a proton-conductive, flexible electrolyte membrane for a fuel cell, which is impermeable to the reaction components of the fuel-cell reaction. Said membrane comprises a composite material that is permeable to substances and that consists of a flexible, perforated support comprising a ceramic, in addition to a porous ceramic material. The composite material is interspersed with a proton-conductive material, which is suitable for selectively conducting protons through the membrane.

Description

Electrolyte membrane, this comprehensive membrane electrode assembly, manufacturing method and special uses

The present invention relates to special proton-conductive, flexible electrolyte membranes for a fuel cell, methods for producing these electrolyte membranes and a flexible membrane electrode unit for a fuel cell, which comprises an electrolyte membrane according to the invention. The present invention further relates to special intermediates in the manufacture of the membrane electrode assembly and special uses of the electrolyte membrane and membrane electrode assembly.

Fuel cells contain electrolyte membranes which, on the one hand, ensure the proton exchange between the half-cell reactions and, on the other hand, prevent a short circuit between the half-cell reactions.

So-called membrane electrode leads (MEAs) are conventionally used in fuel cells, which consist of an ion-conducting electrolyte membrane and the optionally catalytically active electrodes (anode and cathode) applied to it.

Electrolyte membranes made from organic polymers which are modified with acidic groups, such as Nafion® (DuPont, EP 0 956 604), sulfonated polyether ketones (Höchst, EP 0 574 791), are known from the prior art as proton-exchanging membranes (PEMs) for fuel cells. sulfonated hydrocarbons (Dais, EP 1 049 724) or the phosphoric acid-containing polybenzimidazole membranes (Celanese, WO 99/04445).

However, organic polymers have the disadvantage that the conductivity depends on the water content of the membranes. Therefore, these membranes must be swollen in water before use in the fuel cell and although water is constantly being formed on the cathode, additional water must be added from the outside during operation of the membrane to prevent drying out or a decrease in proton conductivity. Typically, organic polymer membrane must be in a fuel cell be operated both on the anode side and on the cathode side in an atmosphere saturated with water vapor.

At elevated operating temperatures, electrolyte membranes made of organic polymers cannot be used, because at temperatures of more than about 100 ° C the water content in the membrane at atmospheric pressure can no longer be guaranteed. The use of such membranes in a reformate or direct methanol fuel cell is therefore generally not possible. In addition, the polymer membranes show a too high permeability for methanol when used in a direct methanol fuel cell. The so-called cross-over of methanol on the cathode side means that only low power densities can be achieved in the direct methanol fuel cell.

Therefore, conventional organic polymer membranes for use in a reformate or direct methanol fuel cell are not practical in spite of the high proton conductivity.

Inorganic proton conductors are e.g. B. from "Proton Conductors", P. Colomban, Cambridge University Press, 1992 known. However, for the purposes of a fuel cell, proton-conductive zirconium phosphates known from EP 0 838 258 show conductivities which are too low. On the other hand, in the case of defect perovskites, a usable proton conductivity is only achieved at temperatures which are above the operating temperatures of a fuel cell that occur in practice. Known proton-conducting MHSO ₄ salts are readily soluble in water and are therefore only of limited use for fuel cell applications in which water is formed in the fuel cell reaction (WO 00/45447).

Known inorganic proton-conducting materials can also not be produced in the form of thin membrane foils, which are required to provide a low total resistance of the cell. Low sheet resistances and high power densities of a fuel cell for technical applications in automobile construction are therefore not possible with the known materials. WO99 / 62620 proposes an ion-conducting, permeable composite material and its use as an electrolyte membrane of an MEA in a fuel cell. The electrolyte membrane from the prior art consists of a metal network which is coated with a porous ceramic material to which a proton-conducting material has been applied. This electrolyte membrane has a proton conductivity superior to an organic Nafipn membrane at temperatures of more than 80 ° C. However, the prior art does not contain an embodiment of a fuel cell in which such an electrolyte membrane has been used.

It has now been found that the electrolyte membrane known from WO99 / 62620 has serious disadvantages with regard to the usability of an MEA containing this electrolyte membrane in practice and with regard to the production process which is required for the provision of such MEAs. Due to these disadvantages, the MEA known from WO99 / 62620 is unsuitable for use in a fuel cell in practice. It has in fact shown that the known electrolyte membranes have indeed at elevated temperatures, a good proton conductivity, that ^"the other hand, occur under practical conditions in a fuel cell shorts that render the electrolyte membranes useless. The use of glass substrates is not excluded, low due to the However, the long-term stability under the strongly acidic conditions in a fuel cell is problematic in terms of the acid stability of glasses, particularly with regard to the long-term stability in the case of the required service life of more than 5000 hours in a fuel cell on board a vehicle, and the electrolyte membranes known from WO99 / 62620 The adhesion of the ceramic material to the metal carrier is problematic, so that the ceramic layer must be separated from the metal net if it is to be left standing for a long time.

It is therefore an object of the present invention to provide a proton-conductive, flexible electrolyte membrane for a fuel cell which is suitable for use in practice and in particular

(i) A high proton conductivity with a significantly reduced air humidity in comparison to polymer membranes, (ii) enables a low total resistance of a membrane electrode assembly, (iii) has mechanical properties such as tensile strength and flexibility, which for a

Use under extreme conditions, such as those that occur when operating a vehicle,

(iv) tolerates increased operating temperatures of more than 80 ° C,

(v) independent of the proton conductive material can be made in membrane thicknesses less than those with conventional ones

Nafion membranes are reached, (vi) short circuits and especially in a direct methanol fuel cell cross-over

Avoids problems, and (vii) can be easily manufactured.

This object is achieved with a proton-conductive, flexible electrolyte membrane for a fuel cell which is impermeable to the reaction components of the fuel cell reaction. The present invention provides an electrolyte membrane comprising a combination of a special composite material and a proton conductive material.

It has been found that the practical uselessness of an electrolyte membrane known from the prior art is related to the fact that the ceramic coating of the metal net tears easily at the throw-over points of the metal threads and the conductive surface of the metal carrier is thereby exposed. A single, very small crack in the ceramic coating is sufficient to render the entire membrane unusable. For this reason, it is not possible to produce the electrolyte membrane known from the prior art in a size that is required for use in a fuel cell without the ceramic coating being subjected to severe stress under operating conditions, which destroys the membrane in a short time ,

The present invention therefore proposes a proton-conductive, flexible electrolyte membrane which is impermeable to the reaction components of the fuel cell reaction a fuel cell, comprising a permeable composite material made of a flexible, perforated support comprising a ceramic and a porous ceramic material, the composite material being permeated with a proton-conductive material which is suitable for selectively guiding protons through the membrane.

It has been found that, surprisingly, an electrolyte membrane which is useful in practice and in particular insensitive to short circuits and cross-over problems can be provided if a ceramic is selected as the material for the membrane support.

The electrolyte membrane of the present invention has the advantage that it does not have to be swollen in water to provide useful conductivity. It is therefore much easier to combine the electrodes and the electrolyte membrane to form a membrane electrode assembly. In particular, it is not necessary to provide a swollen membrane with an electrode layer, as is necessary in the case of a Nafion membrane, in order to prevent the electrode layer from tearing during swelling. The choice of the special all-ceramic carrier also allows the porous ceramic material to adhere firmly to the carrier. In a special embodiment, by using only a single ceramic material, phase boundaries between different materials in the composite material according to the invention can be avoided. It is thus possible to provide a composite material in which problems, for example due to different coefficients of thermal expansion of different materials, cannot occur. This enables a stable MEA to be manufactured that can withstand high mechanical loads. Due to the good stability and conductivity, the electrolyte membranes according to the invention can be used in a reformate or direct methanol fuel cell, which provide long service lives and high power densities even at low water partial pressures and high temperatures. It is also possible to control the water balance of the new membrane electrode units by adjusting the hydrophobicity / hydrophilicity of the membrane and electrodes. The effect of capillary condensation can also be exploited through the targeted creation of nanopores in the membrane. A flooding of the electrodes by product water or Drying out of the membrane at a higher operating temperature or current density can thus be avoided. Furthermore, it is possible to manufacture the electrolyte membranes of the present invention in a membrane thickness, regardless of the proton conductive material, which is less than that which can be achieved with conventional Nafion membranes. In this way, the conductivity and the sheet resistance can be controlled via the membrane thickness in an area that is not accessible to Nafion membranes, and a large number of proton-conductive materials can be selected at the same time. The decoupling according to the invention of the choice of the proton-conductive material from the achievable layer thickness for the creation of electrolyte membranes for fuel cells with desired conductivities and surface resistances is unprecedented in the prior art and enables access to tailored electrolyte membranes.

The ceramic of the carrier is preferably a ceramic fleece or a ceramic fabric made of refractory ceramic fibers with a predominantly polycrystalline microstructure. A ceramic fleece is preferred over a ceramic fabric because it has a higher porosity and no mesh.

The ceramic is preferably a material that consists to a large extent of aluminum oxide, silicon carbide, silicon nitride or a zirconium oxide. In the event that the fibers contain aluminum oxide, there is a ratio of 0 to 30% silicon oxide in relation to aluminum oxide. Fibers containing alumina are preferred.

The carrier must be stable under the operating conditions in a fuel cell. Therefore, the ceramic for the carrier is preferably stable against protons which are passed through the membrane, the proton-conducting material with which the composite material is penetrated and the ceramic material with which the carrier is contacted. Furthermore, the ceramic is preferably also stable with respect to the reaction medium with which the carrier can come into contact if the ceramic coating of the carrier has cracks.

The ceramic from which the carrier is produced preferably has a melting / softening point of> 1400 ° C., particularly preferably> 1550 ° C. The flexible, openwork ceramic support may further comprise a material selected from glass, minerals, plastics, amorphous non-conductive substances, natural products, composites, composite materials, or at least a combination of these materials, provided that these materials are useful Do not affect the electrolyte membrane of the invention under the operating conditions in a fuel cell. A carrier which has been made permeable to material by treatment with laser beams or ion beams can also be used as a flexible, openwork carrier comprising a ceramic.

The carrier preferably comprises fibers and / or filaments with a diameter of 1 to 150 μm, preferably 1 to 20 μm, and / or threads with a diameter of 5 to 150 μm, preferably 20 to 70 μm.

In the event that the carrier is a woven fabric, then this is preferably a woven fabric made of 11-Tex yarns with 5-50 warp or weft threads and in particular 20-28 warp and 28-36 weft threads. 5,5-Tex yarns with 10-50 warp or weft threads are particularly preferred, and 20-28 warp and 28-36 weft threads are preferred.

The porous ceramic material preferably has pores with an average diameter of at least 20 nm, preferably of at least 100 nm, very particularly preferably more than 500 nm. The ceramic material of the composite material preferably has a porosity of 10% to 60%, preferably 20% to 45%.

The proton-conductive material of an electrolyte membrane according to the invention preferably comprises a Bronsted acid, an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof, and / or an ionic liquid. These components impart proton conductivity to the electrolyte membrane. The proton-conductive material can optionally contain an oxide of aluminum, silicon, titanium, zirconium, and / or phosphorus. Such an oxide is essential when using Bronsted acid. In the event that an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof, and / or an ionic liquid are used, the additional oxide can be used to be dispensed with.

The Bronsted acid can be sulfuric acid, phosphoric acid, perchloric acid, nitric acid, hydrochloric acid, sulfurous acid, phosphorous acid and also esters thereof and / or a polymeric organic acid.

The electrolyte membrane according to the invention is preferably stable at at least 80 ° C., preferably at least 120 ° C., and very particularly preferably at at least 140 ° C.

The composite material of the electrolyte membrane preferably has a thickness in the range from 5 to 150 μm, preferably 5 to 50 μm, very particularly preferably 5 to 30 μm, when a ceramic fleece is used as the carrier. The composite material of the electrolyte membrane preferably has a thickness in the range from 10 to 150 μm, preferably 10 to 80 μm, very particularly preferably 10 to 50 μm, when a ceramic fabric is used as the carrier.

The electrolyte membrane according to the invention preferably tolerates a bending radius of at least 100 mm, in particular of at least 20 mm and very particularly preferably of at least 5 mm.

The electrolyte membrane according to the invention preferably has a conductivity of at least 2 mS / cm, preferably at least 20 mS / cm, very particularly preferably 23 mS / cm at room temperature and at a relative atmospheric humidity of 35%.

The production of the electrolyte membranes according to the invention is described below.

An electrolyte membrane of the present invention is available from

(a) Infiltration of a permeable composite of a flexible, perforated support comprising a ceramic and a porous ceramic material with an ionic liquid to create a material penetrating the composite that is capable of selectively protons through the To conduct membrane, or (b) infiltration of a permeable composite material from a flexible, openwork, a ceramic comprising a support and a porous ceramic material with (bl) a mixture containing an immobilizable hydroxysilylalkyl acid of

Sulfur or phosphorus or a salt thereof; or (b2) a mixture comprising a Bronsted acid and / or an immobilizable hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and a sol which comprises a precursor for oxides of aluminum, silicon, titanium, zirconium and / or phosphorus and

Solidification of the mixture infiltrating the composite, and optionally infiltration of the composite obtained after step (b) with an ionic liquid, in order to create a material penetrating the composite which is suitable for selectively passing protons through the membrane.

The electrolyte membranes of the present invention can contain a special composite material which is known in general terms and for another application from PCT / EP98105939. This composite can be infiltrated with a proton-conducting material or a precursor thereof, whereupon the membrane is dried, solidified and optionally modified in a suitable manner, so that a material-impermeable, ion / proton-conducting and flexible membrane is obtained. To produce the composite material, the carrier containing a ceramic is first transferred according to PCT / EP98 / 05939 into a mechanically and thermally stable, permeable ceramic basic membrane which is neither electrically nor ionically conductive. Then this porous, electrically insulating basic membrane is penetrated with the proton-conducting material.

In the production of the composite material, a flexible, perforated carrier comprising a ceramic is contacted or infiltrated with a suspension which contains a precursor for the porous ceramic material. Comes as a preliminary stage for the porous ceramic material at least one inorganic component from a compound of a metal, a semimetal or a mixed metal with one of the elements of the 3rd to 7th main group in question, which are applied as a suspension to the support and can preferably be solidified by heating. Contacting or infiltration can be carried out by printing, pressing, pressing, rolling, knife coating, spreading, dipping, spraying or pouring.

If a ceramic fleece is used as the carrier, the carrier can be treated with a sol before the porous ceramic material is applied. The sol preferably contains precursor compounds of the oxides of aluminum, titanium, zirconium or silicon. By solidifying the sol, the fibers of the ceramic nonwoven are glued together, thereby improving the mechanical stability of the nonwoven.

The suspension with which the carrier is contacted preferably contains an inorganic component and a metal oxide sol, a semimetal oxide sol or a mixed metal oxide sol or a mixture of these sols. Such a preferred suspension can be prepared by suspending an inorganic component in one of these brines.

Commercially available sols such as titanium nitrate sol, zirconium nitrate sol or silica sol can be used. The brine can also be obtained by hydrolysis of a metal compound,

Semimetal compound or mixed metal compound in a medium such as water, alcohol or an acid. A metal nitrate is preferably used as the compound to be hydrolyzed

Metal chloride, a metal carbonate, a metal alcoholate compound or one

Semi-metal alcoholate compound, particularly preferably at least one metal alcoholate compound, a metal nitrate, a metal chloride, a metal carbonate or at least one

Semi-metal alcoholate compound selected from the compounds of the elements Ti, Zr, Al,

Si, Sn, Ce and Y or the lanthanoids and actinoids, such as. B. titanium alcoholates such. B.

Titanium isopropylate, silicon alcoholates, zirconium alcoholates, or a metal nitrate, such as. B.

Zirconium nitrate, hydrolyzed. It may be advantageous to carry out the hydrolysis with at least half the molar ratio of water, based on the hydrolyzable group of the hydrolyzable

Connection to perform. The hydrolyzed compound may be with an acid, preferably with a 10 to 60% acid, preferably with a mineral acid selected from sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid and nitric acid or a mixture of these acids.

An inorganic component with a grain size of 1 to 10,000 nm can be suspended in the sol. An inorganic component which has a compound selected from metal compounds, semimetal compounds, mixed metal compounds and mixed metal compounds with at least one of the elements of the 3rd to 7th main group, or at least a mixture of these compounds, is preferably suspended. Particular preference is given to at least one inorganic component which comprises at least one compound from the oxides of the subgroup elements or from the elements of the 3rd to 5th main group, preferably oxides, selected from the oxides of the elements Sc, Y, Ti, Zr, Nb, Ce, V , Cr, Mo, W, Mn, Fe, Co, B, AI, In, TI, Si, Ge, Sn, Pb and Bi, such as. B. Y ₂ 0 ₃ , Zr0 ₂ , Fe ₂ 0 ₃ , Fe ₃ 0 ₄ , Si0 ₂ , Al ₂ O ₃ , has suspended. The inorganic component can also be aluminosilicates, aluminum phosphates, zeolites or partially exchanged zeolites, such as, for. B. ZSM-5, Na-ZSM-5 or Fe-ZSM-5 or amorphous microporous mixed oxides, which can contain up to 20% non-hydrolyzable organic compounds, such as. B. vanadium oxide, silicon oxide glass or aluminum oxide-silicon oxide-methyl silicon sesquioxide glasses.

The mass fraction of the suspended component is preferably 0.1 to 500 times the hydrolyzed compound used.

Cracks in the composite material can be avoided by a suitable choice of the grain size of the suspended compounds depending on the size of the pores, holes or interstices of the carrier, but also by a suitable choice of the layer thickness of the composite material and the proportionate ratio of sol: solvent: metal oxide.

When using a mesh fabric with a mesh size of z. B. 100 microns can preferably be used to increase the freedom from cracks, which has a suspended compound with a grain size of at least 0.7 microns. in the in general, the ratio of grain size to mesh or pore size should be from 1: 1000 to 50: 1000. The composite material can preferably have a thickness of 5 to 1000 μm, particularly preferably from 10 to 70 μm and very particularly preferably from 10 to 30 μm. The suspension of sol and compounds to be suspended preferably has a ratio of solids to the compounds to be suspended from 0.1: 100 to 100: 0.1, preferably from 0.1: 10 to 10: 0.1 parts by weight.

After contacting the carrier, the suspension can be solidified by heating the composite of suspension and carrier to 50 to 1000 ° C. In a particular embodiment, the composite is exposed to a temperature of 50 to 100 ° C. for 10 seconds to 1 hour, preferably 10 seconds to 10 minutes. In a further particular embodiment, the composite is exposed to a temperature of 100 to 800 ° C. for 5 seconds to 10 minutes, preferably 5 seconds to 5 minutes, particularly preferably for 5 seconds to 1 minute. The composite can be heated with heated air, hot air, infrared radiation, microwave radiation or electrically generated heat. In a further embodiment, the suspension can be solidified by contacting the suspension with a preheated carrier and thus solidifying immediately after contacting.

In a further special embodiment, the carrier is unrolled from a roll at a speed of 1 m / h to 1 m / s, onto an apparatus which contacts the suspension with the carrier and then to another apparatus which solidifies the suspension through Heating is made possible, and the composite material thus produced is rolled up on a second roll. In this way it is possible to manufacture the composite material continuously.

By repeating one of the supports with a suspension or a sol, it is possible to use such supports for the production of composite materials with a specific pore size whose pore or mesh size is not suitable for producing a composite material with the required pore size. This can e.g. B. be the case when using a composite material with a pore size of 0.25 microns a carrier with a mesh size of over 300 μm is to be produced. To obtain such a composite material, it may be advantageous to first bring at least one suspension onto the carrier which is suitable for treating carriers with a mesh size of 300 μm, and to solidify this suspension after application. The composite material obtained in this way can now be used as a carrier with a smaller mesh or pore size. A further suspension can be applied to this carrier, which has a compound with a grain size of 0.5 μm.

The insensitivity to cracks in composite materials with large mesh or pore widths can also be improved by applying suspensions to the carrier which have at least two suspended compounds. Compounds to be suspended are preferably used which have a particle size ratio of 1: 1 to 1:20, particularly preferably 1: 1.5 to 1: 2.5. The weight fraction of the grain size fraction with the smaller grain size should not exceed a proportion of at most 50%, preferably 20% and very particularly preferably 10%, of the total weight of the grain size fraction used.

The composite material is penetrated by a proton-conducting material which is suitable for selectively guiding protons through the membrane and which gives the electrolyte membrane proton conductivity. The proton-conducting material can be introduced into the ceramic material after the production of the composite material or also during the production of the composite material.

The proton-conductive material can comprise a Bronsted acid, an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof, and / or an ionic liquid and optionally an oxide of aluminum, silicon, titanium, zirconium and / or phosphorus. In particular, all the proton-conducting materials described in WO99 / 62620 can be used as a suitable proton-conducting material for producing the electrolyte membrane.

The method according to the invention for producing an electrolyte membrane can start on the basis of the permeable composite material include in particular the following steps:

(a) Infiltration of a permeable composite of a flexible, perforated support comprising a ceramic and a porous ceramic material with an ionic liquid to create a material penetrating the composite which is capable of selectively protons through the

To direct membrane, or

(b) infiltration of a permeable composite material from a flexible, openwork support comprising a ceramic and a porous ceramic material with (b1) a mixture containing an immobilizable hydroxysilylalkyl acid of

Sulfur or phosphorus or a salt thereof; or (b2) a mixture containing a Bronsted acid and / or an immobilizable hydroxysilylalkyl acid of

Sulfur or phosphorus or a salt thereof and a sol which comprises a precursor for oxides of aluminum, silicon, titanium, zirconium and / or phosphorus and

The mixture containing a sol with which the composite material is infiltrated is obtainable by hydrolysis of a hydrolyzable compound, preferably in a mixture of water and alcohol, to give a hydrolyzate, the hydrolyzable compound being selected from hydrolyzable alcoholates, acetates, acetylacetonates, nitrates, oxynitrates , Chlorides, oxychlorides, carbonates, of aluminum, silicon, titanium, zirconium, and / or phosphorus or esters, preferably methyl esters, ethyl esters and / or propyl esters of phosphoric acid or phosphoric acid, and peptizing the hydrolyzate to the mixture containing a sol.

It may be advantageous if the hydrolyzable compound is non-hydrolyzable groups in addition to hydrolyzable groups. An alkyltrialkoxy or dialkyldialkoxy or trialkylalkoxy compound of the element silicon is preferably used as such a compound to be hydrolyzed.

An acid or base soluble in water and / or alcohol can be added to the mixture. An acid or base of the elements Na, Mg, K, Ca, V, Y, Ti, Cr, W, Mo, Zr, Mn, Al, Si, P or S is preferably added.

The mixture can also comprise non-stoichiometric metal, semimetal or non-metal oxides or hydroxides which have been produced by changing the oxidation state of the corresponding element. The oxidation level can be changed by reaction with organic compounds or inorganic compounds or by electrochemical reactions. The oxidation stage is preferably changed by reaction with an alcohol, aldehyde, sugar, ether, olefin, peroxide or metal salt. Compounds that change the oxidation state in this way are e.g. B. Cr, Mn, V, Ti, Sn, Fe, Mo, W or Pb.

Substances which lead to the formation of inorganic ion-conducting structures can also be added to the mixture. Such substances can e.g. B. zeolite and / or β-aluminosilicate particles.

The permeable composite material can also be given an ionic treatment by treatment with a silane. For this purpose, a 1 to 20% solution of this silane is made up in a water-containing solution and the composite material is immersed. Aromatic and aliphatic alcohols, aromatic and aliphatic hydrocarbons and other common solvents or mixtures can be used as solvents. The use of ethanol, octanol, toluene, hexane, cyclohexane and octane is advantageous. After the adhering liquid has dripped off, the impregnated composite material is dried at approximately 150 ° C. and can be used either directly or after repeated subsequent coating and drying at 150 ° C. as an ion-conductive, permeable composite material. Both cationic and anionic silane groups are suitable for this. In the case of proton-conducting materials, sulfonic or phosphonic acid groups are preferred.

It can furthermore be advantageous if the solution or suspension for treating the composite material also comprises acidic or basic compounds and water in addition to a trialkoxysilane. The acidic or basic compounds preferably comprise at least one Bronsted or Lewis acid or base known to the person skilled in the art.

The mixture with which the composite material is infiltrated can contain further proton-conducting substances, preferably titanium phosphates, titanium phosphonates, zirconium phosphates, zirconium phosphonates, iso- and heteropolyacids, nanocrystalline and / or crystalline metal oxides, where Al ₂ O ₃ -, ZrO ₂ -, TiO ₂ - or SiO ₂ powder are preferred. Examples of iso- and heteropolyacids are tungsten phosphoric acid and silicon tungstic acid.

The infiltration of the composite material can be carried out by printing, pressing, pressing, rolling, knife coating, spreading, dipping, spraying or pouring the mixture onto the permeable composite material. The infiltration with the mixture can be carried out repeatedly. If necessary, a drying step, preferably at an elevated temperature in a range from 50 to 200 ° C., can take place between the repeated infiltration. In a preferred embodiment, the infiltration of the permeable composite material takes place continuously. It may be advantageous to preheat the composite material for infiltration.

The mixture can be solidified in the composite material by heating to a temperature of 50 to 800 ° C., preferably 100 to 600 ° C., very particularly preferably 150 to 200 ° C., the heating being carried out by heated air, hot air, infrared radiation or microwave radiation can.

However, the electrolyte membrane can also be formed by using a sol containing an ion-conducting material or a material that is ion-conducting after a further treatment

Has properties are obtained in the manufacture of the composite material. Materials are preferably added to the sol, which lead to the formation of inorganic ion-conducting layers on the inner and / or outer surfaces of the particles contained in the composite material.

An acidic and / or basic group-containing trialkoxysilane solution or suspension can be used to produce the electrolyte membrane. At least one of the acidic or basic groups is preferably a quaternary ammonium, phosphonium, alkylsulfonic acid, carboxylic acid or phosphonic acid group.

A membrane electrode unit according to the invention is described below. The flexible membrane electrode unit for a fuel cell comprises an anode layer and a cathode layer, each of which is provided on opposite sides of a proton-conductive, flexible electrolyte membrane for a fuel cell that is impermeable to the reaction components of the fuel cell reaction, the electrolyte membrane being a permeable composite material made of a flexible, perforated, ceramic comprising carrier and a porous ceramic material, wherein the composite material is interspersed with a proton-conductive material which is capable of selectively guiding protons through the membrane, and wherein the anode layer and the cathode layer are porous and a catalyst for the anode and cathode reactions, respectively proton conductive component and optionally a catalyst support.

The proton-conductive component of the anode and / or cathode layer and / or the proton-conductive material of the composite material preferably each comprises (i) an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof, and optionally an oxide of aluminum, silicon, titanium, zirconium and / or phosphorus, and / or (ii) a Bronsted acid and an oxide of aluminum, silicon, titanium, zirconium, and / or phosphorus and optionally (üi) inorganic oxides, phosphates, phosphides, phosphonates, sulfates, sulfonates,

Vanadates, antimonates, stannates, plumbates, chromates, tungstates, Molybdates, manganates, titanates, silicates, aluminosilicates and aluminates of the elements lithium, sodium, potassium, magnesium, calcium, aluminum, silicon, titanium, zirconium, yttrium, phosphorus vanadium, tungsten, molybdenum, chromium, manganese, iron, cobalt, nickel, Copper, zinc, or cerium, or a combination of these elements, and the proton conductive material of the composite optionally includes an ionic liquid that may contain Bronsted acid. In a preferred embodiment, the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof is an organosilicon compound of the general formulas

[{(RO) _y (R ² ) _z } _a Si {R ¹ -SO ₃ -} _a ] _x M ^{x +} (I) or

[(RO) _y (R ² ) _z Si {R ¹ -Ob-P (OcR ³ ) θ2-} _a ] χM ^x1 - (II)

where R ^{1 is} a linear or branched alkyl or alkylene group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms or a unit of the general formulas

or

, where n, m each represents an integer from 0 to 6, M represents H, NH ₄ or a metal, x = 1 to 4, y = 1 to 3, z = 0 to 2 and a = 1 to 3 mean, provided that y + z = 4 - a, b, c = 0 or 1,

R, R ^{2 are the} same or different and represent methyl, ethyl, propyl, butyl or H and R ^{3 represents} M or a methyl, ethyl, propyl or butyl radical.

The hydroxysilylalkyl acid of sulfur or phosphorus is preferably trihydroxysilylpropylsulfonic acid, trihydroxysilylpropylmethylphosphonic acid or dihydroxysilylpropylsulfondioic acid. Preferably, the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof is immobilized with a hydrolyzed compound of phosphorus or a hydrolyzed nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate of a metal or semimetal. In a further preferred embodiment, the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof with a hydrolyzed compound obtained from titanium propylate, titanium ethylate, tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), zirconium nitrate, zirconium oxynitrate, zirconium propyl acetate, zirconium phosphate acetate, zirconium acetylacetate, zirconium acetylacetate, zirconium acetylacetate, zirconium acyl acetate Diethyl phosphite (DEP) or diethyl ethyl phosphonate (DEEP) immobilized.

Advantageously, the composite impregnated with a proton conductive material can additionally contain an ionic liquid which comprises a cation which is selected from the imidazolium ions, pyridinium ions, ammonium ions or phosphonium ions of the following formulas:

where R and R 'may be the same or different and for alkyl, olefin or aryl groups stand or mean hydrogen, and wherein the ionic liquid comprises an anion which is selected from the following ions: nitrate, sulfate, hydrogen sulfate, chloroaluminations, BF ₄ ^" , alkyl borate ions, preferably triethylhexyl borate, halogenophosphate ions, preferably PF ₆ ^" .

The membrane electrode assembly according to the invention can preferably be operated in a fuel cell at a temperature of at least 80 ° C, preferably at least 120 ° C, and very particularly preferably at at least 140 ° C. The membrane electrode unit according to the invention preferably tolerates a bending radius of at least 100 mm, in particular of at least 20 mm, very particularly preferably of at least 5 mm.

In a special embodiment of the membrane electrode assembly according to the invention, the proton-conductive component of the anode layer and cathode layer and the proton-conductive material of the electrolyte membrane have the same composition. On the other hand, it is also possible that only the anode layer and the cathode layer have the same composition or that the anode layer and the cathode layer have different catalysts. In a preferred embodiment, the catalyst support is electrically conductive in the anode layer and in the cathode layer.

To produce the membrane electrode assembly, an electrolyte membrane is coated with the optionally catalytically active electrode material by a suitable method.

The electrolyte membrane can be provided with the electrode in various ways. The manner and the sequence in which the electrically conductive material, catalyst, electrolyte and possibly further additives are applied to the membrane are at the discretion of the person skilled in the art. It is only necessary to ensure that the interface gas space / catalyst (electrode) / electrolyte is formed. In a special case, the electrically conductive material as a catalyst carrier is dispensed with, in which case the electrically conductive catalyst directly for the discharge of the electrons from the membrane electrode assembly.

In a special embodiment, the catalytically active (gas diffusion) electrodes are built up on the electrolyte membrane to produce the membrane electrode unit. For this purpose, an ink is produced from a soot catalyst powder and at least one proton-conducting material. The ink can also contain other additives that improve the properties of the membrane electrode assembly. The carbon black can also be replaced by other electrically conductive materials (such as metal powder, metal oxide powder, carbon, coal). In a special embodiment, a metal or semimetal oxide powder (such as Aerosil) is used as the catalyst support instead of carbon black. This ink is then applied to the membrane, for example by screen printing, scraping, spraying, rolling or by dipping.

The ink can contain any ion-conducting material that is also used to infiltrate the composite. Thus, the ink can contain an acid or its salt, which is immobilized by a chemical reaction in the course of a nerfixation process after the ink has been applied to the membrane. So this acid can e.g. B. simple Bronsted acid, such as sulfuric or phosphoric acid, or a silylsulfonic or silylphosphonic acid. As materials that support the solidification of the acid, for. B. Al ₂ O ₃ , SiO, ZrO ₂ , TiO ₂ are used, which are also added via molecular precursors of the ink.

In contrast to the proton-conductive material of the composite material, which must be impermeable to the reaction components of the fuel cell reaction, both the cathode and the anode must have a large porosity so that the reaction gases, such as hydrogen and oxygen, are brought to the interface of the catalyst and electrolyte without inhibiting mass transfer can. This porosity can be influenced, for example, by using metal oxide particles with a suitable particle size and by organic pore formers in the ink or by a suitable proportion of solvent in the ink. As a special ink, an agent can be used which comprises the following components: (TI) a condensable component which, after the condensation of an anode layer or a cathode layer of a membrane electrode assembly of a fuel cell

Proton conductivity gives, (T2) a catalyst that the anode reaction or the cathode reaction in one

Catalyzed fuel cell, or a precursor compound of the catalyst, (T3) optionally a catalyst support (T4) optionally a pore former, and

(T5) optionally additives to improve foam behavior, viscosity and adhesion.

The condensable component which imparts proton conductivity to the anode layer or the cathode layer after the condensation is preferably selected from

(I) hydrolyzable compound of phosphorus and / or hydrolyzable nitrates, oxynitrates, chlorides, oxychlorides, carbonates,

Alcoholates, acetates, acetylacetonates of a metal or semimetal, preferably aluminum alcoholates, vanadium alcoholates, titanium propylate, titanium ethylate, zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate, and / or metal acids of aluminum, titanium, lead, tin, vanadium

Tungsten, molybdenum, manganese, with tungsten phosphoric acid and silicon tungsten acid being preferred, and / or

(II) an immobilizable hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and, in a particularly preferred embodiment, additionally a

Hydroxysilylalkyl acid of sulfur or phosphorus or its salt immobilizing hydrolyzable compound of phosphorus or a hydrolyzable nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate of a metal or semimetal, preferably methylphosphate, diethyl phosphite (DEP), diethyl ethyl phosphonate ) Titanium propylate, titanium ethylate, tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), zirconium nitrate, Zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate.

However, the ink can also be used to increase the proton conductivity, nanoscale oxides such. B. of aluminum, titanium, zirconium or silicon, or zirconium or titanium phosphates or phosphonates.

The catalyst or the precursor compound of the catalyst preferably comprises platinum or a platinum alloy and optionally a cocatalyst, the cocatalyst being a transition metal complex of phthalocyanine or substituted phthalocyanines. The catalyst precursor preferably comprises platinum, palladium and / or ruthenium. The transition metal complex of the cocatalyst preferably comprises nickel and / or cobalt.

The pore former, which is optionally contained in the ink, can be an organic and / or inorganic substance which decomposes at a temperature between 50 and 600 ° C and preferably between 100 and 250 ° C. In particular, the inorganic pore former can be ammonium carbonate or ammonium bicarbonate.

The catalyst support, which is optionally contained in the ink, is preferably electrically conductive and preferably contains carbon black, metal powder, metal oxide powder, carbon or carbon.

In a further embodiment, a prefabricated gas distributor which contains the gas diffusion electrode, consisting of an electrically conductive material (for example a porous carbon fleece), catalyst and electrolyte, can be applied directly to the membrane. In the simplest case, the gas distributor and membrane are fixed using a pressing process. For this it is necessary that the membrane or gas distributor have thermoplastic properties at the pressing temperature. The gas distributor can also be fixed on the membrane by an adhesive. This adhesive must be ion-conductive Have properties and can in principle consist of the material classes already mentioned above. For example, a metal oxide sol that additionally contains a hydroxysilyl acid can be used as the adhesive. Finally, the gas distributor can also be applied "in situ" in the last stage of membrane or gas diffusion electrode production. At this stage, the proton-conducting material in the gas distributor or in the membrane has not yet hardened and can be used as an adhesive. The gluing process takes place in both cases by gelling the sol with subsequent drying / solidification.

However, it is also possible to deposit the catalyst directly on the membrane and to provide it with an open-pore gas diffusion electrode (such as an open-pore carbon paper). For this, e.g. B. a metal salt or an acid applied to the surface and reduced to metal in a second step. For example, platinum can be applied via hexachloroplatinic acid and reduced to metal. In the last step, the lead electrode is fixed using a pressing process or an electrically conductive adhesive. The solution containing the metal precursor can additionally contain a compound that is already proton-conductive or at least ion-conductive at the end of the manufacturing process. Suitable ionic materials are the ionic substances mentioned above.

In this way, a membrane electrode unit is obtained which can be used in a fuel cell, in particular in a direct methanol fuel cell or a reformate fuel cell.

The electrolyte membrane according to the invention and the membrane electrode assembly according to the invention can be used in particular for producing a fuel cell or a fuel cell stack, the fuel cell being in particular a direct methanol fuel cell or a reformate fuel cell which is used in a vehicle.

The invention is explained in more detail below with the aid of examples. EXAMPLES

Production Example 1 Production of suspensions

Production example 1.1

120 g of titanium tetraisopropylate are stirred with 140 g of deionized ice with vigorous stirring until the precipitate formed is finely divided. After adding 100 g of 25% hydrochloric acid, the mixture is stirred until the phase becomes clear. Then 280 g of aluminum oxide type CT300OSG from Alcoa, Ludwigshafen, are added and the mixture is stirred for several days until the aggregates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.2

80 g of titanium tetraisopropylate are hydrolyzed with 20 g of water and the resulting precipitate is peptized with 120 g of nitric acid (25%). This solution is stirred until it becomes clear and, after adding 40 g of titanium dioxide from Degussa (P25), the mixture is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.3

90 g of titanium isopropylate are mixed with 40 g of ethanol and hydrolyzed with 10 g of water. The gel that precipitates is peptized with 80 g of a 30% sulfuric acid and, after the gel has completely dissolved, 30 g of aluminum oxide from Degussa are added and the mixture is stirred until the agglomerates have dissolved. This suspension can then be used

Manufacture of a composite material or used as a precursor for a proton conductive material.

Production example 1.4 50 g of titanium tetraethoxylate were hydrolyzed with 270 g of water and peptized with 30 g of nitric acid (25%). 100 g of ethanol and 350 g of CT 2000 SG from Alcoa were then added and stirred. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.5

40 g of titanium isopropylate and 30 g of methyltriethoxysilane are mixed with 60 g of ethanol and hydrolyzed with 10 g of water. The gel which precipitates out is peptized with 60 g of 30% hydrochloric acid and, after the gel has completely dissolved, 90 g of amorphous microporous mixed oxides (cf. DE 19545042) are added and the mixture is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Preparation example 1.6 80 g of titanium tetraisopropoxide are hydrolyzed with 20 g of water and the resulting precipitate is peptized with 120 g of nitric acid (25%). This solution is stirred until it becomes clear and, after adding 20 g of titanium dioxide from Degussa (P25) and 40 g of titanium dioxide in the anatase form, the mixture is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.7

40 g of titanium tetraisopropylate are hydrolyzed with 20 g of water and the resulting precipitate is peptized with 60 g of nitric acid (25%). This solution is stirred until it becomes clear and, after adding 40 g of tin oxide from Aldrich, the mixture is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production Example 1.8 80 g of titanium tetraisopropylate are hydrolyzed with 40 g of water and the resulting precipitate is peptized with 120 g of 25% hydrochloric acid. This solution will last until Stirring is clear and after adding 200 g of titanium dioxide from Bayer, the mixture is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.9

120 g of titanium tetraisopropylate are stirred with 140 g of deionized ice with vigorous stirring until the precipitate formed is finely divided. After addition of 100 g of 25% nitric acid, the mixture is stirred until the phase becomes clear and 280 g of aluminum oxide of the type CT300OSG from Alcoa, Ludwigshafen, are added and the mixture is stirred for several days until the aggregates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production Example 1.10 20 g of titanium tetraisopropylate and 120 g of titanium hydroxide hydrate (S500-300, test product from Rhone-Poulenc were hydrolyzed or dissolved with 45 g of water and peptized with 50 g of 25% hydrochloric acid. After clearing and adding 300 g of aluminum oxide ( 7988 E330 (from Norton Materials) and 50 g of iron (III) chloride are stirred until the agglomerates dissolve, and this suspension can then be used to produce a composite or as a precursor for a proton-conducting material.

Production example 1.11

6 g of titanium tetrachloride were hydrolyzed with 10 g of 25% hydrochloric acid. After clearing and adding 13 g of aluminum oxide (7988 E330, from Norton Materials) and 2 g of ruthenium chloride, the mixture was stirred until the agglomerates had dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production Example 1.12 100 g of silica sol (Levasil 200, from Bayer AG) were stirred with 180 g of AA07 aluminum oxide from Sumitomo Chemical until the agglomerates dissolved. This suspension can then used to manufacture a composite or as a precursor for a proton conductive material.

Production Example 1.13 70 g of tetraethoxysilane are hydrolyzed with 20 g of water and the resulting precipitate is peptized with 120 g of nitric acid (25%). This solution is stirred until it becomes clear and, after adding 40 g of amorphous silica or amorphous silicon dioxide from Degussa, the solution is stirred until the agglomerates have dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Preparation example 1.14

20 g of aluminum triisopropylate are placed in 10 g of ethanol and hydrolyzed with 5 g of water. The resulting gel is peptized with 45 g of nitric acid (15%) and stirred until the gel has completely dissolved. After adding 60 g of vanadium pentoxide from Aldrich, the mixture is stirred until the agglomerates have completely dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1. 15

20 g of zirconium tetraisopropylate are hydrolyzed with 15 g of water and the resulting precipitate is peptized with 30 g of nitric acid (25%). After the precipitate has completely dissolved, 60 g of zeolite Y (type CBV 780 from Zeolyst) are stirred until the agglomerates have completely dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Preparation example 1.16

20 g of zirconium tetraisopropylate are hydrolyzed with 15 g of water and the resulting precipitate is peptized with 30 g of nitric acid (25%). After completely loosening the

Precipitation is after adding 10 g of zirconium dioxide from Degussa (particle size 50 run) until the agglomerates are completely dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1. 17

20 g of zirconium tetraisopropylate are hydrolyzed with 15 g of water and the resulting precipitate is peptized with 30 g of nitric acid (25%). After the precipitate has completely dissolved, 60 g of corundum powder with a particle size of 10 micrometers (Amperit, HC Stark) are stirred until the agglomerates are completely dissolved. This suspension can then be used to manufacture a composite or as a precursor for a proton conductive material.

Production example 1.18

20 g of zirconium nitrate sol (30% strength from MEL Chemicals were mixed with 150 g of water, 25 g of titanium dioxide (Finntianx 78173 from Kemira Pigments and 210 g of glass powder (HK, from Robert Reidt). This suspension can then be prepared a composite material or as a precursor for a proton-conducting material.

Production Example 1.19 10 g of zirconium nitrate sol (30% from MEL Chemicals and 50 g of titanium dioxide filter cake, test product from Sachtzleben were stirred with 150 g of water, 290 g of aluminum oxide 71340 RA from Nabaltec until the agglomerates dissolved. This suspension can then be used to make a composite or as a precursor for a proton conductive material.

Production example 1.20

120 g of zirconium tetraisopropylate are stirred with 140 g of deionized ice with vigorous stirring until the precipitate formed is finely divided. After addition of 100 g of 25% hydrochloric acid, the mixture is stirred until the phase becomes clear and 280 g of aluminum oxide of the CT300OSG type from Alcoa, Ludwigshafen, were added and the mixture was stirred for several days until the aggregates dissolved. This suspension can then be made a composite material or as a precursor for a proton-conducting material.

Production example 2 Production of the composite materials

Production example 2.1

A ceramic fleece with a thickness of about 10 microns made of Al ₂ O ₃ fibers is with a

Zikonnitratsol, containing 30 wt .-% ZrO ₂ , treated and annealed at 200 ° C to bond the ceramic fibers. A suspension according to Example 1.9 is knife-coated onto the treated ceramic fleece and dried within 10 seconds by blowing with hot air which had a temperature of 550 ° C. A flat composite material was obtained which can be used as a composite material with a pore size of 0.2 to 0.4 μm. The composite material can be bent to a radius of 5 mm without the composite material being destroyed. The composite material can be used to produce an electrolyte membrane according to the invention.

Production example 2.2

A suspension according to production example 1.2 was applied to a composite material as described in example 2.1 by rolling it up with a layer thickness of 5 μm. The suspension was solidified again by blowing the composite with hot air at 550 ° C. for about 5 seconds. A composite material was obtained which had a pore size of 30-60 nm and is suitable for producing an electrolyte membrane according to the invention.

Production examples 2.3 to 2.19

The suspensions of preparation examples 1.3 to 1.19 are each applied to the carrier described in preparation example 2.1 and dried by blowing with air at a temperature of 450-550 ° C. for a few seconds. The composite material obtained can be used to produce a composite membrane according to the invention. Production example 2.20

The suspension produced according to production example 1.20 is applied in a thin layer to a ceramic fleece and solidified at 550 ^° C. within 5 seconds. The composite material obtained can be used to produce a composite membrane according to the invention.

example 1

Production of an electrolyte membrane by treating a composite material with silanes.

An inorganic, permeable composite material, which was produced by applying a thin layer of the suspension from preparation example 1.1 on a ceramic carrier according to preparation example 2.1, was immersed in a solution which consisted of the following components: 5% Degussa silane 285 (a propylsulfonic acid triethoxysilane), 20% deionized (VE) water in 75% ethanol. The solution had to be stirred at room temperature for 1 h before use.

After the supernatant solution was drained, the composite was dried at 80 to 150 ° C to provide an electrolyte membrane of the present invention.

Example 2

Production of an electrolyte membrane

20 g of aluminum alcoholate and 17 g of vanadium alcoholate were hydrolyzed with 20 g of water and the resulting precipitate was peptized with 120 g of nitric acid (25%). This solution was stirred until it became clear and, after addition of 40 g of titanium dioxide from Degussa (P25), stirring was continued until all agglomerates had dissolved. After the pH had been adjusted to about 6, the suspension was knife-coated onto a composite material prepared according to production example 2.1 and dried in order to create a proton-conducting electrolyte membrane equipped with negative fixed charges. Examples 3 and 4

Production of an electrolyte membrane with zeolites

10 g of methyltriethoxisilane, 30 g of tetraethylorthosiloxane and 10 g of aluminum trichloride were hydrolyzed with 50 g of water in 100 g of ethanol. 190 g of zeolite USY (CBV 600 from Zeolyst) were then added. It was still rubbed until all agglomerates had dissolved and then the suspension was spread on a composite material produced according to production example 2.1 or 2.2 and solidified by heat treatment at 600 ° C. to create a proton-conducting electrolyte membrane.

Example 5

Production of an electrolyte membrane

10 ml of anhydrous trihydroxysilylpropylsulfonic acid, 30 ml of ethanol and 5 ml of water are mixed by stirring. 40 ml of TEOS (tetraethyl orthosilicate) are slowly added dropwise to this mixture with stirring. For condensation, this sol is stirred in a closed vessel for 24 h. The composite material from production example 2.20 is immersed in this sol for 15 minutes. The sol is then allowed to gel in the impregnated membrane for 60 minutes in air and dry. The membrane filled with the gel is dried at a temperature of 150 ° C. for 60 minutes, so that the gel solidifies and becomes water-insoluble. In this way a dense membrane is obtained which has a proton conductivity at room temperature and normal ambient air of approx. 2T0 ^"3 S / cm.

Example 6 Production of an Electrolyte Membrane

An additional 25 g of tungsten phosphoric acid are dissolved in 50 ml of the sol from Example 5. The composite material from production example 2.1 is immersed in this sol for 15 minutes. Then proceed as in Example 5.

Example 7 Production of an electrolyte membrane

100 ml of titanium isopropylate is added dropwise to 1200 ml of water with vigorous stirring. The resulting precipitate is aged for 1 h and then mixed with 8.5 ml of concentrated nitric acid and peptized at the boiling point for 24 h. 50 g of tungsten phosphoric acid are dissolved in 25 ml of this sol. A further 25 ml of trihydroxysilylpropylsulfonic acid are added to this solution and the mixture is stirred for one hour at room temperature. The composite material from production example 2.1 is then immersed in this sol for 15 minutes. The membrane is then dried and solidified by a temperature treatment at 150 ° C. and converted into the proton-conducting form.

Example 8

Production of an electrolyte membrane

Sodium trihydroxysilylmethylphosphonate dissolved in a little water is diluted with ethanol. The same amount of TEOS is added to this solution and stirring is continued briefly. The composite material from production example 2.1 is immersed in this sol for 15 minutes. The membrane is then dried and solidified by a temperature treatment at 250 ° C. and converted to the proton-conducting form by an acid treatment.

Example 9

Production of an electrolyte membrane

10 g of methyltriethoxisilane, 30 g of tetraethylorthosilicate and 10 g of aluminum trichloride are hydrolyzed with 50 g of water in 100 g of ethanol. 190 g of zeolite USY (CBV 600 from Zeolvst) are then added to this mixture. Stirring is continued until all agglomerates have dissolved and then the suspension is spread onto a composite material produced according to Example 2.20 and solidified by a heat treatment at 500 ^° C. and transferred into the ion-conducting membrane.

Examples 10 to 14 Production of an electrolyte membrane by infiltrating a proton-conducting membrane with an ionic liquid

A porous electrolyte membrane according to Examples 5 to 9 is sprayed with [EMIM] CF ₃ SO ₃ (EMIM: 1-ethyl-3-methylimidazolium) as the ionic liquid.

Spraying is carried out from one side of the composite material until the opposite side of the composite material is also wetted by the ionic liquid which has passed through the composite material. In this way it is achieved that the air contained in the porous ion-conducting composite material is displaced by the ionically conductive liquid. This membrane can be allowed to air dry after wiping off excess ionic liquid. The ionic liquid is retained in the membrane according to the invention by capillary forces. Because ionic

Liquids do not have a measurable vapor pressure, even after prolonged storage of the membrane produced according to the invention, a reduction in the ionic liquid in the membrane is not to be expected.

Examples 15 to 74

Production of an electrolyte membrane by infiltrating a proton-conducting membrane with an ionic liquid

Instead of the [EMIM] CF ₃ SO ₃ from Examples 10 to 14, the twelve ionic liquids according to [EMIM] CF ₃ SO _{3 are used} according to the following table:

The abbreviations have the following meaning:

EMIM = 1-ethyl-3-methylimidazolium ion, BMIM = 1-butyl-3-methylimidazolium ion, MMIM = 1-methyl-3-methylimidazolium ion, Ts = H ₃ CC ₆ H ₄ SO ₂ (tosyl), Oc = octyl, Et = ethyl, Me = methyl, Bu = n-butyl, CF ₃ SO ₃ = triflate anion and Ph = phenyl can be used.

Example 75

Production of an electrolyte membrane by immobilizing a Bronsted acid

A TEOS solution consisting of TEOS: ethanol: H ₂ O: HCl = 1: 8: 4: 0.05 mol is precondensed for 24 h. Then give 20 vol% conc. HClO (70%) to the sol and after briefly stirring by knife coating it with a base membrane, which was produced according to production example 2.20. After infiltration, the membrane is solidified at RT and dried. The conductivity of the membrane at room temperature and approx. 35% r. F. is approx. 20 mS / cm.

Example 76

Production of an electrolyte membrane by immobilizing a Bronsted acid

An electrolyte membrane was produced as in Example 75, H ₂ SO ₄ (98% strength) being added to the sol instead of HClO ₄ as acid. Under the same measurement conditions (room temperature and approx. 35% RH), the conductivity is about 23 mS / cm after a thermal treatment of 100 ° C (1 h). Example 77

Production of an electrolyte membrane by immobilizing a Bronsted acid

A TEOS sol consisting of TEOS (11 ml), diethyl phosphite (19 ml), ethanol (11 ml) and H ₃ PO ₄ (10 ml) is precondensed for one hour and then a basic membrane, which was produced according to Preparation Example 2.20 , infiltrated by doctor blade. The membrane is dried at 150 ° C for 1 h. The conductivity of the membrane at room temperature and approx. 35% rh is around. 2.9 mS / cm.

Example 78

Production of an electrolyte membrane by immobilizing a Bronsted acid

100 ml of titanium isopropoxide are dropped into 1200 ml of water with vigorous stirring. The resulting precipitate is aged for 1 h and then concentrated with 8.5 ml. HNO _{3 was} added and peptized at the boil for 24 h. 10 ml of H ₂ SO (98%) are added to 100 ml of this sol. After coating the base membrane 2.20 with such a sol and solidifying at temperatures of up to approximately 150 ° C., the proton-conducting membrane is obtained.

Example 79 Preparation of an anode ink

10 ml of anhydrous trihydroxysilylpropylsulfonic acid, 60 ml of ethanol and 5 ml of water are mixed by stirring. 40 ml of TEOS (tetraethyl orthosilicate) are slowly added dropwise to this mixture with stirring. The catalyst known from DE 197 21 437 and DE 198 16 622 is dispersed in this sol so that a degree of catalyst coverage of approximately 0.2 mg / cm ² or 0.5 mg / cm ² can be achieved in the electrode.

Example 80

Production of an anode ink

100 ml of titanium isopropoxide are dropped into 1200 ml of water with vigorous stirring. The The resulting precipitate is aged for 1 h and then concentrated with 8.5 ml. HNO _{3 was} added and peptized at the boil for 24 h. 50 g of tungsten phosphoric acid are dissolved in 50 ml of this sol and the catalyst is then dispersed therein as described in Example 79.

Example 81

Production of an anode ink

20 g of aluminum alcoholate and 17 g of vanadium alcoholate are hydrolyzed with 20 g of water and the resulting precipitate is peptized with 120 g of nitric acid (25%). This solution is stirred until it becomes clear and, after addition of 40 g of titanium dioxide from Degussa (P25), stirring is continued until all agglomerates have dissolved. After the pH has been adjusted to about 6, the catalyst is dispersed therein as described in Example 79.

Example 82 Preparation of Cathode Ink

10 ml of anhydrous trihydroxysilylpropylsulfonic acid, 60 ml of ethanol and 5 ml of water are mixed by stirring. 20 ml of TEOS (tetraethyl orthosilicate) and 20 ml of methyltriethoxysilane are slowly added dropwise to this mixture with stirring. The catalyst used in DE 196 11 510 or the one used in DE 198 12 592 is dispersed in this sol, so that a Pt coverage of about 0.15 mg / cm ² or 0.25 mg / cm ² can be achieved in the electrode , Example 83 Preparation of a cathode ink

20 g of methyltriethoxysilane, 20 g of tetraethyl orthosilicate and 10 g of aluminum trichloride are hydrolyzed with 50 g of water in 200 g of ethanol. 190 g of zeolite USY (CBV 600 from Zeolyst) are then added. The mixture is stirred until all agglomerates have dissolved and then the catalyst is dispersed therein as described in Example 82.

Example 84 Manufacture of a membrane electrode assembly

A membrane according to Example 1 is first screen-printed with the ink according to Example 79 by screen printing. This side serves as an anode in the later membrane electrode assembly. The printed membrane is dried at a temperature of 150 ° C. In addition to the escape of the solvent, the silylpropylsulfonic acid is also immobilized.

In the second step, the membrane on the back, which will later serve as the cathode, is printed with the ink from Example 82. Even now the printed membrane is again dried at a temperature of 150 ° C., whereby the solvent escapes and at the same time the silylpropylsulfonic acid is immobilized. Since the cathode is hydrophobic, the product water can easily escape when the membrane electrode unit is operated in the fuel cell. This membrane electrode assembly can be installed in a direct methanol fuel cell or a reformate fuel cell.

Example 85

Manufacture of a membrane electrode assembly

To produce the electrodes, both the anode ink according to Example 80 and the cathode ink according to Example 83 are each applied to an electrically conductive carbon paper. A heat treatment at a temperature of 150 ° C removes the solvent and immobilizes the proton-conductive component. These two gas diffusion electrodes are pressed with a proton-conductive membrane to form a membrane electrode unit, which can then be installed in the fuel cell.

Example 86

Manufacture of a fuel cell

To manufacture the MEA, the electrodes are first manufactured. For this, a ceramic fleece is coated with a carbon black / platinum mixture (40%). These electrodes are pressed onto the electrolyte membrane according to Example 77. The pressure is applied via a graphitic gas distribution plate, which also serves for electrical contacting. Pure hydrogen is used on the anode side and pure oxygen is used on the cathode side. Both gases are moistened via water vapor saturators (so-called "bubblers").

Comparative example

A fuel cell was made as described in Example 86, except that a conventional Nafion®117 membrane was used as the MEA. It was found that the proton conductivity dropped drastically when using a Nafion membrane at a relative air humidity of less than 100% and the surface resistance increased sharply, so that the fuel cell could no longer be operated. On the other hand, a membrane according to the invention can also be operated at a relative atmospheric humidity which was approximately 10% on the anode side and approximately 5% on the cathode side without the function of the fuel cell being significantly impaired.

Claims

claims:

1. Proton-conductive, flexible electrolyte membrane for a fuel cell, which is impermeable to the reaction components of the fuel cell reaction, comprising a permeable composite material made of a flexible, perforated support comprising a ceramic and a porous ceramic material, the composite material being permeated with a proton-conductive material which is suitable is to selectively conduct protons through the membrane.

2. Electrolyte membrane according to claim 1, characterized in that the proton-conductive material (i) an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and optionally an oxide of aluminum, silicon, titanium, zirconium and / or phosphorus, and / or

(ii) an ionic liquid, which may optionally contain a Bronsted acid, and / or (iii) comprises a Bronsted acid and an oxide of aluminum, silicon, titanium, zirconium, and / or phosphorus.

3. Proton-conductive, flexible electrolyte membrane for a fuel cell, impermeable to the reaction components of the fuel cell reaction, obtainable from

(a) infiltrating a permeable composite of a flexible, perforated support comprising a ceramic and a porous ceramic material with an ionic liquid to create a material penetrating the composite that is capable of selectively guiding protons through the membrane, or

(b) Infiltration of a permeable composite material comprising a flexible, open-ended carrier comprising a ceramic and a porous ceramic material (bl) a mixture containing an immobilizable hydroxysilylalkyl acid of

Sulfur or phosphorus or a salt thereof; or (b2) a mixture comprising a Bronsted acid and / or an immobilizable hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and a sol containing one

Precursor for oxides of aluminum, silicon, titanium, zirconium, and / or phosphorus comprises and (c) solidification of the mixture infiltrating the composite, and optionally infiltration of the composite obtained in step (b) with an ionic liquid around a material penetrating the composite to create that is capable of selectively guiding protons through the membrane.

4. Electrolyte membrane according to one of claims 1 to 3, wherein the carrier comprises refractory ceramic fibers with polycrystalline microstructure.

5. Electrolyte membrane according to one of claims 1 to 4, characterized in that the ceramic of the carrier is a material which consists to a large extent of aluminum oxide, silicon carbide, silicon nitride or a zirconium oxide.

6. Electrolyte membrane according to one of claims 1 to 5, wherein the carrier contains fibers or filaments made of aluminum oxide, which have a ratio of 0 to 30% silicon oxide / aluminum oxide.

7. Electrolyte membrane according to one of claims 2 to 6, characterized in that the Bronsted acid comprises sulfuric acid, phosphoric acid, perchloric acid, nitric acid, hydrochloric acid, sulfurous acid, phosphorous acid and esters thereof and / or a monomeric or polymeric organic acid.

8. electrolyte membrane according to one of claims 1 to 7, characterized in that the carrier comprises a fabric and particularly preferably a fleece.

9. electrolyte membrane according to claim 8, 5 characterized in that the carrier fibers and / or filaments with a diameter of 0.5 to 150 microns, preferably 0.5 to 20 microns, and / or threads with a diameter of 5 to 150 microns , preferably 20 to 70 microns.

10 10. Electrolyte membrane according to claim 8 or 9, characterized in that the carrier is a fabric with a mesh size of 5 to 500 microns, preferably 10 to 200 microns, or that the carrier is a fleece with a thickness of 5 - 100 microns and is preferably from 10 to 30 μm. 15

11. Electrolyte membrane according to one of claims 1 to 10, characterized in that the porous ceramic material has a porosity of 10% to 60%, preferably from 20% to 45%. 20

12. Electrolyte membrane according to one of claims 1 to 11, characterized in that the porous ceramic material has pores with an average diameter of at least 20 nm, preferably at least 100 nm, very particularly preferably more than 25 250 nm.

13. Electrolyte membrane according to one of claims 1 to 12, which is stable at at least 80 ° C, preferably at least 120 ° C, and very particularly preferably at least 140 ° C.

^'30

14. Electrolyte membrane according to one of claims 1 to 13, characterized in that the composite material has a thickness in the range from 5 to 150 μm, when using a fabric preferably 10 to 80 μm, very particularly preferably 10 to 50 μm, and when using a fleece preferably 5 to 50 μm, very particularly preferably 10 to 30 μm.

15. Electrolyte membrane according to one of claims 1 to 14, which tolerates a bending radius of at least 100 mm, preferably of at least 20 mm, very particularly preferably of at least 5 mm.

16. Electrolyte membrane according to one of claims 1 to 15, which has a conductivity of at least 2 mS / cm, preferably at least 20 mS / cm, very particularly preferably 23 mS / cm at room temperature and at a relative atmospheric humidity of 35%.

17. A method for producing an electrolyte membrane according to one of claims 1 to 16, characterized in that the method comprises the following steps:

(a) infiltration of a permeable composite material from a flexible, perforated support comprising a ceramic and a porous ceramic material with an ionic liquid in order to create a material penetrating the composite material which is suitable for selectively guiding protons through the membrane, or

(b) Infiltration of a permeable composite material comprising a flexible, perforated support comprising a ceramic and a porous ceramic material

(bl) a mixture containing an immobilizable hydroxysilylalkyl acid of

Precursor for oxides of aluminum, silicon, titanium, zirconium, and / or Includes phosphorus and

Solidification of the mixture infiltrating the composite, and optionally infiltration of the composite obtained in step (b) with an ionic liquid, in order to create a material penetrating the composite which is suitable for selectively guiding protons through the membrane.

18. The method of claim 17, wherein the sol is obtainable by

(al-1) hydrolysis of a hydrolyzable compound, preferably in a mixture of water and alcohol, to give a hydrolyzate, the hydrolyzable

Compound is selected from hydrolyzable alcoholates, acetates,

Acetylacetonates, nitrates, oxynitrates, chlorides, oxychlorides, carbonates, of aluminum, silicon, titanium, zirconium, and / or phosphorus or esters, preferably methyl esters, ethyl esters and / or propyl esters of phosphoric acid or phosphoric acid,

(al-2) Peptizing the hydrolyzate to a sol.

19. The method according spoke 17 or 18, characterized in that the mixture further proton-conducting substances, preferably titanium phosphates,

Titanium phosphonates, zirconium phosphates, zirconium phosphonates, iso- and heteropoly acids, preferably tungsten phosphoric acid or silicon tungstic acid, nanocrystalline and / or crystalline metal oxides, with Al ₂ O ₃ , ZrO ₂ , TiO ₂ or SiO ₂ powder being preferred.

20. The method according to any one of claims 17 to 19, wherein the infiltration takes place by pressing, pressing, pressing, rolling, knife coating, spreading, dipping, spraying or pouring the mixture onto the permeable composite material.

21. The method according to any one of claims 17 to 20, wherein the infiltration with the mixture is carried out repeatedly and optionally a drying step, preferably at an elevated temperature in a range of 50 to 200 ° C, between repeated infiltration.

22. The method according to any one of claims 17 to 21, wherein the infiltration of the permeable composite material is carried out continuously.

23. The method according to any one of claims 17 to 22, wherein a heated composite material is infiltrated.

24. The method according to any one of claims 17 to 23, wherein the solidification is carried out by heating to a temperature of 50 to 800 ° C, preferably 100 to 600 ° C, very particularly preferably 150 to 200 ° C.

25. The method according to Anspmch 20 or 21, wherein the heating is carried out by heated air, hot air, infrared radiation or microwave radiation.

26. Flexible membrane electrode unit for a fuel cell, with an electrically conductive anode and cathode layer, which are provided on opposite sides in each case of a proton-conductive, flexible electrolyte membrane for a fuel cell, which is impermeable to the reaction components of the fuel cell reaction, in particular according to one of claims 1 to 16, the electrolyte membrane comprising a permeable composite material made of a flexible, perforated support comprising a ceramic and a porous ceramic material, the composite material being permeated with a proton-conductive material which is capable of selectively guiding protons through the membrane, and wherein the anode layer and the

Are cathode layer porous and each include a catalyst for the anode and cathode reaction, a proton conductive component and optionally a catalyst support.

27. Membrane electrode unit according to Anspmch 26, the proton-conductive component of the anode and / or cathode layer and / or the proton-conductive material of the Composite material in each case comprises (i) an immobilized hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and optionally an oxide of aluminum, silicon, titanium, zirconium and / or phosphorus, and / or (ii) a Bronsted acid and an oxide of aluminum, silicon, Titanium, zirconium, and / or phosphorus and optionally (iii) inorganic oxides, phosphates, phosphides, phosphonates, sulfates, sulfonates, vanadates, antimonates, stannates, plumbates, chromates, tungstates, molybdates, manganates, titanates, silicates, aluminosilicates and aluminates Elements lithium, sodium, potassium, magnesium, calcium, aluminum, silicon, titanium, zirconium,

Yttrium, phosphorus vanadium, tungsten, molybdenum, chromium, manganese, iron, cobalt, nickel, copper, zinc or cerium or a combination of these elements, and the proton-conductive material of the composite material optionally comprises an ionic liquid which may contain a Bronsted acid.

28. Membrane electrode unit according to Anspmch 27, wherein the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof is an organosilicon compound of the general formulas

[{(RO) _y (R ² ) _z } _a Si {R ¹ -SO ₃ -} _a ] _x M ^{x +} (I)

[(RO) _y (R ² ) _z Si {R ¹ -O _b -P (O _c R ³ ) O ₂ ^" } _a ] _x M ^{x +} (II)

is where R ^{1 is} a linear or branched alkyl or alkylene group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms or a unit of the general

formulas

or

, where n, m each represents an integer from 0 to 6, M represents H, NEW or a metal, x = 1 to 4, y = 1 to 3, z = 0 to 2 and a = 1 to 3 mean, with the proviso that y + z = 4 - a, b, c = 0 or 1, R, R ^{2 are the} same or different and are methyl, ethyl, propyl, butyl or H and

R ^{3 represents} M or a methyl, ethyl, propyl or butyl radical.

29. Membrane electrode unit according spoke 28, wherein the hydroxysilylalkyl acid of sulfur or phosphorus is trihydroxysilylpropylsulfonic acid, trihydroxysilylpropylmethylphosphonic acid or dihydroxysilylpropylsulfonedioic acid.

30. Membrane electrode unit according to one of claims 27 to 29, characterized in that the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof with a hydrolyzed compound of phosphorus or a hydrolyzed nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate one Metal or semi-metal is immobilized.

31. Membrane electrode unit according spoke 30, characterized in that the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof with a hydrolyzed compound obtained from diethyl phosphite (DEP), Diethyl ethyl phosphonate (DEEP), titanium propylate, titanium ethylate, tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate or phosphoric acid methyl ester is immobilized.

32. Membrane electrode unit according to one of claims 26 to 31, characterized in that the composite permeated with a proton-conductive material additionally contains an ionic liquid which comprises a cation which is selected from the imidazolium ions, pyridinium ions, ammonium ions or phosphonium ions of the following formulas:

where R and R 'may be the same or different and represent alkyl, olefin or aryl

Stand for groups or stand for hydrogen, and wherein the ionic liquid comprises an anion which is selected from the following ions: nitrate, sulfate, hydrogen sulfate, chloroaluminations, BF ₄ ^" , alkyl borate ions, preferably triethylhexyl borate, halogenophosphate ions, preferably PF ₆ ^" .

33. Membrane electrode unit according to one of claims 26 to 32, which can be operated at a temperature of at least 80 ° C, preferably at least 120 ° C, and very particularly preferably at least 140 ° C.

34. Membrane electrode unit according to one of claims 26 to 33, wherein the flexible, openwork carrier comprises an acid-resistant ceramic.

35. Membrane electrode unit according to one of claims 26 to 34, which has a bending radius of at least 100 mm, preferably of at least 20 mm, very particularly preferably of at least 5 mm.

36. Membrane electrode unit according to one of claims 26 to 35, wherein the proton-conductive component of the anode layer and cathode layer and the proton-conductive material of the electrolyte membrane have the same composition.

37. Membrane electrode unit according to one of claims 26 to 36, wherein the anode layer and the cathode layer have the same composition.

38. Membrane electrode unit according to one of claims 26 to 36, wherein the anode layer and the cathode layer have different catalysts.

39. Membrane electrode unit according to one of claims 26 to 38, wherein the catalyst support in the anode layer and in the cathode layer is electrically conductive.

40. A method for producing a membrane electrode unit according to one of claims 26 to 39, the method comprising the following steps,

(A) Provision of a proton-conductive, flexible electrolyte membrane for a fuel cell, which is impermeable to the reaction components of the fuel cell reaction, in particular according to one of claims 1 to 16, wherein the electrolyte membrane is a permeable composite material made of a flexible, perforated carrier comprising a ceramic and a porous

Ceramic material, the composite material being interspersed with a proton-conductive material which is suitable for selectively guiding protons through the membrane,

(B) Provision of an agent for producing an anode layer and a cathode layer, the agent each comprising:

(B1) a condensable component which, after the condensation of the Electrode layer gives proton conductivity, (B2) a catalyst which catalyzes the anode reaction or the cathode reaction, or a precursor compound of the catalyst, (B3) optionally a carrier and (B4) optionally a pore former,

(C) applying the agents from stage (B) to one side of the electrolyte membrane from stage (A) to form a coating,

(D) Creation of a firm bond between the coatings and the electrolyte membrane to form a porous, proton-conductive anode layer or cathode layer, the formation of the anode layer and the

Cathode layer can take place simultaneously or in succession.

41. The method according to approach 40, wherein the application of the agent in step (C) is carried out by squeezing, pressing, pressing, rolling, knife coating, spreading, dipping, spraying or pouring.

42. The method according to any one of claims 40 or 41, wherein the agent according to step (B) for producing an anode layer or a cathode layer is a suspension which can be obtained by (S1) producing a hydrosol comprising a hydroxysilylalkyl acid of sulfur or phosphorus or the salt thereof and, if appropriate, a hydrolyzable compound of phosphorus which immobilizes the hydroxysilylalkyl acid of sulfur or phosphorus or its salt, or a hydrolyzable nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate of a metal or semimetal, preferably

Phosphoric acid methyl ester, diethylphosphite (DEP), diethylethylphosphonate (DEEP), titanium propylate, titanium ethylate, tetraethylorthosilicate (TEOS) or tetramethylorthosilicate (TMOS), zirconium nitrate, zirconium oxynitrate, zirconium propylate, catalyst disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (zirconium) acetate and disodium (C3)

Pore former.

43. The method according to any one of claims 40 to 42, wherein the agent according to step (B) for producing an anode layer or a cathode layer is a suspension which is obtainable by

(Hl) hydrolysis of a hydrolyzable compound to a hydrolyzate, the hydrolyzable compound being selected from a hydrolyzable compound of phosphorus or hydrolyzable nitrates, oxynitrates, chlorides, oxychlorides, carbonates, alcoholates, acetates, acetylacetonates of a metal or semimetal, preferably aluminum alcoholates, Vanadium alcoholates, titanium propylate, titanium ethylate, zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate, or metal acids of

Aluminum, silicon, titanium, vanadium, antimony, tin, lead, chromium, tungsten, molybdenum, manganese, preference being given to tungsten phosphoric acid and silicon tungstic acid, (H2) peptizing the hydrolyzate with an acid to give a dispersion, (H3) mixing the dispersion with a nanocrystalline and / or crystalline

Metal oxide, preferably Al ₂ O ₃ , ZrO ₂ , TiO or SiO ₂ powder, (H4) dispersing the catalyst and, if appropriate, the support and pore former.

44. The method of spoke 42 or 43, wherein the means for producing an anode layer and a cathode layer in step (C) are exposed and for

Creation of a firm bond between the coatings and the electrolyte membrane to form a porous, proton-conductive anode layer or cathode layer in step (D) heated to a temperature of 100 to 800 ° C, preferably 150 to 500 ° C, most preferably 180 to 250 ° C becomes.

45. Method according to approach 40 or 41, characterized by

(Ml) applying the agent for producing an anode layer or cathode layer to a support membrane, preferably made of polytretrafluoroethylene, as a coating (M2) drying the coating obtained under (Ml),

(M3) pressing the dried coating onto the electrolyte membrane at a Temperature of 100 to 800 ° C, preferably 150 to 500 ° C, very particularly preferably 180 to 250 ° C, (M4) removing the support membrane, in particular by mechanical detachment, chemical dissolution, or pyrolysis or characterized by

(Nl) applying the agent for producing an anode layer or cathode layer to a support membrane, preferably made of carbon paper or an electrically conductive fleece, as a coating, (N2) drying the coating obtained under (Nl) to produce a coated support membrane,

(N3) pressing the coated support membrane onto the electrolyte membrane at one

Temperature from room temperature to 800 ° C, preferably 150 to 500 ° C, most preferably 180 to 250 ° C.

46. The method according to any one of claims 40 or 41, wherein in step (B) in each case providing an agent for producing an anode layer and a cathode layer, the agent each comprises: (vl) a condensable component which gives proton conductivity after the electrode layer has been condensed and (v2) a catalyst metal salt, preferably hexachloroplatinic acid, after application of the agents by step (C) the catalyst metal salt is reduced to a catalyst which catalyzes the anode reaction or the cathode reaction, in step (D) an open-pore gas diffusion electrode, preferably an open-pore carbon paper , pressed onto the catalyst or glued to the catalyst with an electrically conductive adhesive.

47. The method according to any one of claims 40 to 46, wherein the application of the agent for

Production of an anode layer or cathode layer is carried out repeatedly and optionally a drying step, preferably at an elevated temperature in a range from 100 to 200 ° C., between the repeated implementation of the

Applying.

48. The method according to any one of claims 40 to 47, wherein the application of the means for producing an anode layer or cathode layer is carried out on a flexible electrolyte membrane or flexible support membrane rolled off a first roll.

49. The method according to any one of claims 40 to 48, wherein the application of the agent for producing an anode layer or cathode layer takes place continuously.

50. The method according to any one of claims 40 to 49, wherein the application of the means for producing an anode layer or cathode layer is carried out on a heated electrolyte or support membrane.

51. The method according to any one of claims 40 to 50, wherein in step (D) to create a firm bond between the coatings and the electrolyte membrane to a temperature of 100 to 800 ° C, preferably 150 to 500 ° C, very particularly preferably 180 to 250 ° C is heated.

52. The method according to spoke 51, wherein heating is carried out by means of heated air, hot air, infrared radiation or microwave radiation.

53. Medium comprising:

(TI) a condensable component, which after the condensation of an anode layer or a cathode layer of a membrane electrode assembly of a fuel cell

Gives proton conductivity, (T2) a catalyst which catalyzes the anode reaction or the cathode reaction in a fuel cell, or a precursor compound of the catalyst,

(T3) optionally a catalyst support and (T4) optionally a pore former, and (T5) optionally additives to improve foam behavior, viscosity and

Liability.

54. Agent according spoke 53, wherein the condensable component according to the Condensation of the anode layer or the cathode layer gives proton conductivity, is selected from

(I) hydrolyzable compound of phosphorus or hydrolyzable nitrates, oxynitrates, chlorides, oxychlorides, carbonates, alcoholates, acetates,

Acetylacetonates of a metal or semimetal, preferably aluminum alcoholates, vanadium alcoholates, titanium propylate, titanium ethylate, zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetyl acetonate, or metal acids of aluminum, titanium, vanadium, antimony, zinc oxide

Chromium, tungsten, molybdenum, manganese, with tungsten phosphoric acid being preferred, and / or

(II) an immobilizable hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and optionally a hydrolysable compound of the phosphorus or a hydrolysable nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate a metal or semimetal, preferably diethylphosphonate (DEP), diethylethylphosphonate (DEEP), phosphoric acid methyl ester, titanium propylate, titanium ethylate, tetraethyl orthosilicate

(TEOS) or tetramethyl orthosilicate (TMOS), zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate.

55. Agent according to spoke 53 or 54, wherein the catalyst or the precursor compound of the catalyst comprises a platinum metal or an alloy of platinum metals and optionally a cocatalyst, the cocatalyst being a transition metal complex of phthalocyanine or substituted phthalocyanines.

56. Agent according to claim 55, in which the catalyst or the precursor compound of the catalyst comprises platinum, palladium and / or ruthenium and optionally the

Transition metal complex includes nickel and / or cobalt.

57. Agent according to one of claims 53 to 56, in which the pore former is an organic and / or inorganic substance which decomposes at a temperature between 50 and 600 ° C and preferably between 100 and 250 ° C.

58. Agent according spoke 57, in which the inorganic pore former is ammonium carbonate or ammonium bicarbonate.

59. Agent according to one of claims 53 to 54, wherein the catalyst support is electrically conductive and preferably consists of carbon black, graphite, carbon, carbon, activated carbon or metal oxides.

60. Use of an electrolyte membrane according to one of claims 1 to 16 in a fuel cell.

61. Use according spoke 61, wherein the fuel cell is a direct methanol fuel cell or a reformate fuel cell.

62. Use of an electrolyte membrane according to one of claims 1 to 16 for producing a membrane electrode assembly, a fuel cell, or a fuel cell stack.

63. Use of a membrane electrode assembly according to one of claims 26 to 39 in a fuel cell.

64. Use according to spoke 63, wherein the fuel cell is a direct methanol fuel cell or a reformate fuel cell.

65. Fuel cell with an electrolyte membrane according to one of claims 1 to 16.

66. Fuel cell with a membrane electrode unit according to one of claims 26 to 39.

67. Mobile or stationary system with a membrane electrode unit, a fuel cell or a fuel cell stack, containing an electrolyte membrane according to one of claims 1 to 16 or a membrane electrode unit according to one of claims 26 to 39.

68. Mobile or stationary system according to spoke 67, which is a vehicle or a house energy system.