DE10205849A1 - Proton-conducting ceramic membranes based on zirconium phosphates, processes for their production and their use in MEAs and fuel cells - Google Patents

Abstract

The present invention relates to proton-conducting ceramic membranes based on zirconium phosphates, processes for their production and the use thereof in MEAs and fuel cells. DOLLAR A The ceramic membranes described here represent a new class of proton-conducting membranes. For this, nanoscale zirconium phosphate is first produced using a special process in a microjet reactor. This material is then applied to a flexible carrier as a suspension and solidified. In the end, an impermeable, cation- / proton-conducting membrane is obtained, which is flexible and can be used in a fuel cell without any problems.

Description

The present invention relates to proton-conducting ceramic membranes based on Zirconium phosphates, process for their preparation and their use in MEAs and fuel cells.

Membranes are at the heart of a fuel cell. In the case of proton exchange Membranes (PEMs) are essentially called acidic with electrolyte membranes Group of modified polymers used. Usually the nation (DuPont, fluorinated backbone with a sulfonic acid functionality) or related systems used. Another example of a purely organic, proton-conducting polymer are u. a. sulfonated polyether ketones described by Hoechst (EP 0574 791 B1).

All these polymers have the disadvantage that the conductivity decreases with decreasing Humidity decreases sharply. Therefore, these membranes must be used in the Fuel cells are swollen in water. At an elevated temperature, as in the reformate or direct methanol fuel cell (RFC or DMFC) is inevitable, these are systems can no longer be used or can only be used to a limited extent, since it can easily dry out Membrane can come. Another problem of polymer membranes for use in a DMFC represents the high permeability for methanol. Due to the crossover of Methanol on the cathode side leads to a severe loss of performance Fuel cell.

For all these reasons, the use of organic polymer membranes for the RFC or DMFC are not optimal and need for a widespread use of fuel cells new solutions are found.

Inorganic proton conductors are also known from the literature (see, for example, in "Proton Conductors", P. Colomban, Cambridge University Press, 1992), but these mostly show conductivities which are too low or the conductivity only reaches at high temperatures, typically above 500 ° C technically usable values, such as B. in the defect perovskites. Another class of purely inorganic proton conductors, the MHSO ₄ family, are good proton conductors, but at the same time they are easily soluble in water, so that they are out of the question for fuel cell applications, since water is produced on the cathode side as a product and the membrane thereby that time would be destroyed. For a long time, the suitability of glass-like systems (Abe et. Al., J. Sol-Gel Sci. Techn. 14 (1999), 273 ff.; Minami et. Al., Chem. Lett. (2000), 1314 ff ) or by Xerogelen (Anderson et. al., Chem. Mater. 12 (2000), 1762 ff) as proton-conducting materials. However, due to insufficient conductivity, these materials are not suitable for use in fuel cells.

The zirconium phosphates (ZrP), in the form of the α- or γ-ZrP, have long been known as proton conductors (Alberti, Solid State Ionics 125 (1999), 91 ff). Since the conductivity of this material is essentially determined by the free OH groups, a large surface area is of great importance. For pure α-ZrP, the literature (Glipa et al. Solid State Ioncis 97 (1997), 227 ff) specifies a conductivity of 10 ^-5 to 10 ^-6 S / cm at medium atmospheric humidity. Linkov (EP 0 838 258) provides an indication of the possible use of zirconium phosphates in membranes of fuel cells, but without giving precise details of the quality of the membrane, in particular its proton conductivity. This membrane described in EP 0 838 258 is also based on a conventional, very thick and inflexible membrane. Due to the membrane thickness, only membranes with a high surface resistance can be manufactured. For fuel cell applications, however, conductivities must not fall below 10 ^-3 S / cm and membrane thicknesses of 100 µm must not be exceeded. The rigid membranes in the fuel cell described by Linkov are therefore unsuitable for practical applications.

Another problem when using the inorganic proton conductor mentioned here in The fuel cell lies in the fact that these ceramics are practically not thin at all Have membrane film made. Because the electrolyte is automatically made very thick the total resistance of the cell, even with high specific conductivity, is always Quite high. High power densities of fuel cells as used for technical applications z. B. in the automobile, are indispensable, can not be achieved.

However, flexible, largely inorganic proton-conducting membranes are also known (WO 99/62620). These combine the advantages of organic membrane foils (high flexibility, low membrane thickness) with those of inorganic, proton-conducting systems (less critical Water balance, usability up to 200 ° C, no methanol cross-over). This too However, materials are suitable due to insufficient conductivity and therefore too low Power densities not yet for use in fuel cells. In addition, is like in Composite material described in WO 99/62620 not for use in a fuel cell Also not suitable under real conditions, because for these applications the Electrolyte membrane must be absolutely impermeable, otherwise it will be a direct Reaction of the reactants (hydrogen or methanol on the anode side and oxygen or air on the cathode side). Furthermore, it is essential that the openwork supports both inside and on both surfaces the ion-conducting Has layers, since a contact between the electrolyte and electrodes in the so-called MEA (membrane electrode assembly) must exist around the circuit in the Close fuel cell. Furthermore, this is preferred in WO 99/62620 Steel mesh to be used absolutely described for fuel cell applications Unsuitable, since short circuits between the Electrodes are created.

The object of the present invention was therefore to provide flexible, inorganic proton-conducting membranes with a conductivity of at least 10 ^-3 S / cm and a process for their production.

Surprisingly, it was found that nanoscale zirconium phosphates are produced and can be made using these thin flexible membranes that have a sufficiently large proton conductivity. This represents a new class of Membranes for RFC and DMFC are available.

The present invention therefore relates to a proton-conducting membrane Claim 1, comprising a flat, provided with a plurality of openings, flexible Substrate with a coating located on and in this substrate, the material the substrate is selected from woven or non-woven, not electrically conductive Fibers of glass or ceramic or a combination of such materials, which thereby is characterized in that the coating proton-conducting nanoscale particles of Has zirconium phosphate with a primary particle size less than 5000 nm and impermeable for the reaction components in a fuel cell.

The present invention also relates to a method for producing a proton-conducting membrane according to at least one of claims 1 to 15, wherein a flat, flexible substrate with a large number of openings in and on it The substrate is provided with a coating, the material of the substrate being woven or non-woven, non-electrically conductive fibers of glass or ceramic or a Combination of such materials, which is characterized in that Application of a suspension or a sol, the or the at least nanoscale Has zirconium phosphate particles on the substrate and by at least one Heating, in which the suspension or the sol is solidified on and in the substrate, a proton conductive coating is applied.

The present invention also relates to the use of a membrane according to at least one of claims 1 to 12 as a proton exchange membrane in Fuel cells and fuel cells that have a membrane according to at least one of the Claims 1 to 12.

Compared to the membranes based on polymers, the membranes according to the invention have the advantage that they can be used at higher temperatures, the water balance is not critical and there is no methanol crossover. Compared to the known Ceramic proton-conducting membranes have the membranes of the invention The advantage that they can be made much thinner and more flexible.

The membranes according to the invention are gas-tight or impermeable to Reaction components in a fuel cell, such as. B. hydrogen, oxygen, air and / or methanol. Under gas-tight or impermeable to the reaction components in the Understand the present invention that through the membranes of the invention less than 50 liters of hydrogen and less than 25 liters of oxygen per day, bar and Square meter passes through and the permeability of the membrane for methanol significantly lower is as with commercial Nafion membranes, which are usually also considered impermeable be designated.

The fact that a suspension of nanoscale zirconium phosphate particles with a certain size is solidified in and on the substrate as a coating, it is ensured that a more even distribution of the zirconium phosphate particles over the entire Membrane is reached as z. B. by the method described in EP 0 838 258 Infiltrating zirconium salts in a porous ceramic membrane and subsequent Treatment with a polyacid, especially a polyphosphoric acid can be achieved because both the distribution of the particles in the porous ceramic membrane and the size the particle more or less randomly depending on z. B. the porosity and Pore size of the porous ceramic membrane is determined. Probably by the big one Surface of the nanoscale primary particles, the more uniform distribution of the Zirconium phosphate particles and / or the more uniform size of the particles as well as the thin Execution of the membranes clearly show the membranes of the invention lower resistance to proton conduction than previously known ceramic ones Membranes containing zirconium phosphates.

The membrane according to the invention is described below by way of example, without the invention is to be limited to these embodiments.

The proton-conducting membranes according to the invention comprise a flat one A plurality of openings provided, flexible substrate with one on and in this substrate located coating, wherein the material of the substrate is selected from woven or non-woven, non-electrically conductive fibers of glass or ceramic or one Combination of such materials and are characterized in that the coating Proton-conducting nanoscale particles of zirconium phosphate with a primary particle size has less than 5 microns and gas-tight or impermeable to the reaction components in one Fuel cell, such as B. is hydrogen, oxygen, air and / or methanol.

The membranes according to the invention preferably have a thickness of less than 100 μm, preferably less than 50 µm and very particularly preferably less than 30 µm. As particularly suitable for the use of the membrane according to the invention in fuel cells have found membranes with a thickness of 10 to 50 microns, with thinner Membranes if you have adequate stability and gas tightness or tightness have the reaction components in a fuel cell, are also used can.

Due to the small thickness, a particularly low resistance of the invention proton-conducting membranes. The as the basis for infiltration with the Zirconium phosphate used fabrics, nonwovens, felts or flexible porous Ceramic membranes themselves of course have a very high electrical resistance, otherwise there would be a risk of a short circuit between the anode and cathode.

So that a membrane according to the invention with electrically insulating properties can be obtained, these preferably have non-electrically conductive fibers as the material for the substrate, selected from glass, aluminum oxide, SiO ₂ , SiC, Si ₃ N ₄ , BN, B ₄ N, AlN, sialones or ZrO ₂ .

The material of the substrate can e.g. B. a fabric, fleece or felt made of non-electrical conductive fibers exist, the substrate also having a porous ceramic Coated fabric, fleece or felt made of non-electrically conductive fibers, such as z. B. can be a microfiltration membrane. This means a particularly good proton conductivity can be achieved, the material of the substrate is very particularly preferably a nonwoven, Glass fiber fabric or felt, which does not have a porous ceramic coating exhibits, since materials without porous coating achieve a higher conductivity can be, since the porosity is significantly higher due to the lower death volume and thus more proton conductive material per area of the membrane is available for proton conduction stands. The use of nonwovens has the advantage over fabrics that nonwovens again have a higher porosity than tissue, but tissue shows a higher strength as fleeces. Depending on the desired membrane properties, the use of a Fabric or a nonwoven made of glass fibers can be preferred as the substrate in the membrane.

In principle, all glass materials available as fibers, such as. B. E, A, ECR, C, D, R, S and M glass can be used for support. E, ECR or S glass fibers are preferably used. The preferred types of glass have a low content of BaO, Na ₂ O or K ₂ O. The preferred types of glass preferably have a BaO content of less than 5% by weight, very particularly preferably less than 1% by weight, a Na ₂ O content of less than 5% by weight, very particularly preferably less than 1% by weight and a K ₂ O content of less than 5% by weight, very particularly preferably less than 1% by weight. It may be advantageous if the fibers consist of types of glass which have none of the compounds BaO, Na ₂ O or K ₂ O, such as, for. B. E-glass, because such types of glass are more resistant to chemical influences.

In a particularly preferred embodiment of the proton-conducting membrane according to the invention, the fibers, particularly preferably the glass fibers made of E or S glass, are the substrate with a thin film made of SiO ₂ , ZrO ₂ , TiO ₂ or Al ₂ O ₃ or with mixtures thereof Oxides are coated. The oxidic coatings are particularly preferred for types of glass that have low acid stability, such as. B. E-glass. The weight ratio of oxidic coating to glass in the carrier is preferably less than 15 to 85, more preferably less than 10 to 90 and very particularly preferably less than 5 to 95.

If the membrane according to the invention has a glass fiber textile, such as. B. a Glass fiber fabric, felt or fleece, these are preferably made of fibers with a thickness of maximum 20 tex (mg / m), preferably from fibers with a maximum strength of 10 tex and very particularly preferably made from fibers with a maximum thickness of 5.5 tex.

The substrate very particularly preferably has a glass fiber fabric which consists of fibers 5.5 or 11 tex thick. The individual filaments of such fibers have z. B. a diameter of 5 to 7 microns. That is preferably used as support Glass fiber fabric has from 5 to 30 weft threads / cm and from 5 to 30 warp threads / cm, preferably from 10 to 30 wefts / cm and from 10 to 30 warps / cm and whole particularly preferably from 15 to 25 weft threads / cm and from 15 to 25 warp threads / cm. By the use of such glass fabric can ensure that the membrane is a has sufficient strength and at the same time sufficient porosity of the substrate.

The coating of the membrane according to the invention preferably has a nanoscale Zirconium phosphate particles with a primary particle size of 1 to 1000 nm, preferred nanoscale zirconium phosphate particles with a primary particle size of 1 to 100 nm and whole particularly preferably nanoscale zirconium phosphate particles with a primary particle size of 10 up to 100 nm. In addition to the nanoscale zirconium phosphate primary particles, the coating according to the invention also agglomerates of zirconium phosphate primary particles with a size of 1 μm or more, preferably from 1 to 100 μm, particularly preferred have from 1 to 25 µm.

It can be advantageous if the coating of the proton-conducting membrane next to the nanoscale zirconium phosphate particles at least one oxide of the metals Al, Zr, Si, or Ti having. These oxides can be in the coating as z. B. by gluing, sintering particles or similar processes are present. This is particularly the case if a carrier provided with a ceramic coating for producing the proton-conducting membrane is used. However, the oxides can also be isolated ceramic particles are present. This is especially the case when the coating is generated by the fact that oxide particles together with the Zirconium phosphate primary particles are applied as sol or suspension to the support and solidified. In particular, isolated oxide particles are present when the weight ratio of oxide to Zirconium phosphate is significantly less than 1: 1. The oxide particles preferably have one Particle size of 5 µm or less, particularly preferably a particle size of 0.01 to 1 µm or 0.01 to 0.1 µm, where the particles can be primary particles or agglomerates.

The membranes according to the invention are distinguished by the fact that they have conductivity have greater than 1 mS / cm. The membrane according to the invention preferably has a Proton conductivity from 1 to 100 mS / cm and very particularly preferably from 1 to 10 mS / cm at room temperature and a relative humidity of 80 to 90%. The Membranes according to the invention can preferably be down to a radius without damage of 250 m, preferably of 10 cm and very particularly preferably of 5 mm. The high conductivity and the good flexibility of the membranes according to the invention has the Advantage that the membranes according to the invention in fuel cells of almost any geometry can be used.

In addition, the membranes are insoluble in water and methanol and show, e.g. B. in Compared to nation, only a very low permeability (practically no permeability) for Methanol. These membranes are therefore preferably suitable for DMFCs.

The membrane according to the invention is preferably obtainable by a process for Production of a proton-conducting membrane, being a flat, with a large number of Opened, flexible substrate in and on this substrate with a coating is provided, the material of the substrate woven or non-woven, not electrically has conductive fibers of glass or ceramic or a combination of such materials, which is characterized in that by applying a suspension to the substrate, which has at least nanoscale zirconium phosphate particles on the substrate and through heating at least once, during which the suspension solidifies on and in the substrate a coating is applied.

The suspension can e.g. B. by printing, pressing, pressing, rolling, doctoring, Spreading, dipping, spraying or pouring onto and into the substrate.

The material of the substrate is preferably selected from glass, aluminum oxide, SiO ₂ , SiC, Si ₃ N ₄ , BN, B ₄ N, AlN, Sialone or ZrO ₂ , in particular from high-temperature and / or acid-proof glass, quartz glass or ceramic. The material the substrate can consist of non-electrically conductive fibers of the aforementioned materials as a fabric, fleece or felt. In order that uniform conductivity can be achieved in the membrane, a glass fiber fleece made of non-woven glass fibers is preferably used as the material of the substrate.

In principle, all glass materials available as fibers, such as. B. E, A, ECR, C, D, R, S and M glass can be used for the substrate. E or S glass fibers are preferably used. The preferred types of glass have a low content of BaO, Na ₂ O or K ₂ O. The preferred types of glass preferably have a BaO content of less than 5% by weight, particularly preferably less than 1% by weight, a Na ₂ O content of less than 5% by weight, particularly preferably less than 1% by weight and a K ₂ O content of less than 5% by weight, particularly preferably less than 1% by weight. It may be advantageous if the fibers consist of types of glass which have none of the compounds BaO, Na ₂ O or K ₂ O, such as, for. B. E-glass, since such glass types are more resistant to chemicals.

In a particularly preferred embodiment of the method for producing the proton-conducting membranes according to the invention, the fibers, particularly preferably glass fibers made of E or S glass, of the substrate are coated with a thin film made of SiO ₂ . Such a coating can e.g. B. be applied in that tetraethyl orthosilicate (TEOS) is applied to the fibers, individually or in the form of fabric, felt or fleece, the TEOS is dried and then at a temperature of 400 to 600 ° C, preferably at 420 to 500 ° C and very particularly preferably at 440 to 460 ° C the TEOS is burned off. When it burns, silicon dioxide remains as a residue on the fiber surface. It was found that fibers treated in this way are much better suited as substrate material than untreated fibers, since the subsequent coating adheres to the treated fibers much better and thus the long-term stability is significantly improved. In addition to coatings made of SiO ₂ , coatings made of ZrO ₂ , TiO ₂ or Al ₂ O ₃ or with mixtures of these oxides are also possible. B. alcoholates of the corresponding metals can be assumed. The coating can be produced analogously to the coating with TEOS.

If a glass fiber textile, such as. B. a glass fiber fabric, felt or fleece used, preferably those are used which consist of fibers with a thickness of maximum 20 tex (mg / m), preferably from fibers with a maximum strength of 10 tex and were particularly preferably made of fibers with a maximum thickness of 5.5 tex. A glass fiber fabric which consists of is very particularly preferably used as the substrate Fibers with a thickness of 5.5 or 11 tex was produced.

The individual filaments of such fibers have z. B. a diameter of 5 to 7 microns. The glass fiber fabric, which is preferably used as a substrate, has from 5 to 30 weft threads / cm and from 5 to 30 warps / cm, preferably from 10 to 30 wefts / cm and from 10 to 30 Warp threads / cm and very particularly preferably from 15 to 25 weft threads / cm and from 15 to 25 Warp threads / cm. The use of such glass fabrics can ensure that the membrane according to the invention is sufficiently strong and at the same time sufficient has great porosity of the substrate.

When using commercially available glass fiber textiles, in particular glass fiber fleeces, Glass fiber felts or glass fiber fabrics could also be found that the Removal of the sizing on the fibers during the manufacturing process of the glass fiber textile applied, has a great influence on the resilience of the glass fiber textile. The size is usually obtained by heating the glass fiber textile, in particular Glass fiber fabric, up to 500 ° C for 1 to 2 min. and subsequent thermal Treat the textile at up to 300 ° C for about 4 days away. Surprisingly found that a glass fiber textile treated in this way is much more brittle than glass fiber textile, which the sizing still has. On and in a glass fiber textile as a substrate, which has the size, however, the coating according to the invention can be difficult apply, as this adheres poorly to the textile due to the size. It was Surprisingly found that the size burn off at temperatures below 500 ° C, preferably below 450 ° C within 2 min., Preferably within 1 min. and subsequent treatment with TEOS as described above is sufficient to achieve a better durable coating of the glass fiber textile, especially the glass fiber fabric guarantee.

It can be advantageous if the material of the substrate is one with a porous one Ceramic-coated glass fiber textile is used. Those with ceramics coated glass fiber textiles are known from WO 99/15262. The ceramic coating is applied to the glass fiber textile preferably by applying a suspension that at least one, a compound of at least one metal, a semi-metal or a mixed metal At least one element of the 3rd to 7th main group, inorganic component and having a sol, on the glass fiber textile and by heating at least once which the suspension having at least one inorganic component on or in or else is applied to and solidified in the glass fiber textile. The procedure for Manufacture of such glass fiber textiles coated with ceramic is likewise from WO 99/15262 known. To the different types of ceramic coated glass fiber textiles as well their production is expressly referred to WO 99/15262.

The suspension used to produce the coating has at least a nanoscale Zirconium phosphate particles with a particle size smaller than 1 µm. The suspension for Production of the coating of the membrane according to the invention preferably has nanoscale zirconium phosphate particles with a primary particle size of 1 to 1000 nm, preferably nanoscale zirconium phosphate particles with a primary particle size of 1 to 100 nm and very particularly preferably nanoscale zirconium phosphate particles with a Primary particle size 10 to 100 nm. In addition to the nanoscale zirconium phosphate The coating according to the invention can also contain primary particles from agglomerates of Zirconium phosphate particles with a size of 1 μm or more, preferably from 1 to 100 μm, particularly preferably have from 1 to 25 μm. The nanoscale zirconium phosphate Particles are preferably produced in an upstream step. In principle stand for this all process paths are open which are suitable for the production of nanoscale powders, such as B. gas phase process (analogous to Aerosil production, wire explosion process, Microwave plasma processes, etc.) but also liquid phase processes.

Production according to the "microjet process" known from the literature (Penth, WO 00/61275) has proven to be particularly suitable. In this process, the nanoscale zirconium phosphate particles for producing the suspension are produced by shooting a solution of a soluble zirconium compound and a solution containing phosphorus-containing compounds at one another in a microjet reactor. The soluble zirconium compound used can be selected from zirconium nitrate, zirconium chloride, zirconium acetate, zirconium acetylacetonate or a zirconium alcoholate. The solution used, which has phosphorus-containing compounds, preferably has at least one compound selected from phosphoric acid and / or phosphate salts, in particular phosphate salts of the alkali metals, such as. B. Na ₃ PO ₄ , Na ₂ HPO ₄ or NaH ₂ PO ₄ .

In the simplest case, water can serve as the solvent. Become sensitive to hydrolysis Educts used, such as zirconium alcoholates, can also alcohols or others anhydrous solvents can be used.

The solutions are made in the microjet reactor using a special high-pressure process converted to zirconium phosphate, in which the two are in a microjet reactor Solutions as a thin jet under very high pressure of up to a few hundred bar via nozzles preferably 50 to 500 microns in diameter are shot at each other. The Reaction products can e.g. B. removed from the reactor by an air stream.

With this method there is no particle growth of the primary particles. The Primary particle and possibly also agglomerate size can be determined by the test conditions, with which the microjet reactor is operated. Using this procedure a colloidal suspension containing the zirconium phosphate is obtained directly. typical Zirconium phosphate concentrations in this suspension are 0.01-50% by weight, and preferably 0.1-5% by weight. If necessary, the suspensions can be evaporated by used solvent can also be further concentrated.

This suspension can be used directly on the above substrates be applied. The zirconium phosphate particles mentioned can also themselves be produced in which the zirconium phosphate obtained from the microjet reactor Suspension, by spray drying into a powder which contains nanoscale zirconium phosphate Has particles that can be transferred. Spray drying can be carried out in a known manner be carried out and is preferably carried out at a temperature of 100 to 200 ° C, preferably at a temperature of 100 to 150 ° C.

In a further embodiment of the method according to the invention, the suspension but also other, partly commercially available materials, such as metal oxides, nitrides Carbide or zirconium phosphate particles can be added in powder form. Preferably at least one oxide of the elements Al, Zr, Ti or Si added to the suspension. The addition of Metal oxides or other inorganic components has the advantage that the Proton conductivity set to the desired value and optimal infiltration of the Substrate can be achieved so that one for the reaction components in the end Fuel cell impermeable or gas-tight proton-conducting membrane is formed.

It can be advantageous if at least one inorganic component, which has a grain size of less than 5 μm, preferably from 10 to 1000 nm, and very particularly preferably from 100 to 1000 nm, is added to the suspension. However, other proton-conductive materials, such as iso- and heteropolyacids, or other nanoscale powders from the series Al ₂ O ₃ , ZrO ₂ TiO ₂ and SiO ₂ can also be added to the suspension. The suspension can also contain Bronsted acids or immobilizable silylic acids.

In a further embodiment of the method according to the invention, the method used Suspension which has nanoscale zirconium phosphate particles, at least one sol, at least one semi-metal oxide sol or at least one mixed metal oxide sol or a mixture these have brine.

The brines are hydrolyzed by at least one compound, preferably at least a metal compound, at least one semi-metal compound or at least one Mixed metal compound with at least one liquid, solid or gas receive, it may be advantageous if as a liquid such. B. water, alcohol or a Acid, ice as a solid or water vapor as a gas or at least a combination of these Liquids, solids or gases are used. It can also be advantageous to hydrolyzing compound before hydrolysis in alcohol or an acid or an Combination of these liquids. As a compound to be hydrolyzed preferably at least one metal nitrate, one metal chloride, one metal carbonate, one Metal alcoholate compound or at least one semi-metal alcoholate compound, especially preferably at least one metal alcoholate compound, a metal nitrate, a metal chloride Metal carbonate or at least one semi-metal alcoholate compound selected from the Compounds of the elements Zr, Al, Si, or Ti, such as. B. zirconium alcoholates such. B. Zirconium isopropylate, silicon alcoholates, or a metal nitrate, such as. B. zirconium nitrate, hydrolysed.

It may be advantageous to use at least the hydrolysis of the compounds to be hydrolyzed half the molar ratio of water, steam or ice, based on the hydrolyzable Group, the hydrolyzable compound.

The hydrolyzed compound can be peptized with at least one organic or inorganic acid, preferably with a 10 to 60% organic or inorganic Acid, particularly preferably with a mineral acid selected from sulfuric acid, hydrochloric acid, Perchloric acid, phosphoric acid and nitric acid or a mixture of these acids treated become.

It is not only possible to use brine which has been produced as described above, but also commercial brine, such as. B. zirconium nitrate sol or silica sol.

The coating according to the invention is made by solidifying the suspension in and on the Substrate applied. According to the invention, the suspension is Rolling, spraying or similar processes applied to the carrier material. This is preferably done in a continuous process. According to the invention and the suspension present in the substrate can be solidified by heating to 50 to 500 ° C. In a special embodiment of the method according to the invention, the on and Suspension present in the support by heating to 100 to 450 ° C, preferably by Heating to 150 to 400 ° C and most preferably by heating to 150 to 300 ° C solidified. It may be beneficial if heating for 1 second to 15 minutes, preferably for 10 seconds to 5 minutes. The application / infiltration can be done once or several times, preferably one between the application steps thermal treatment, preferably at a temperature of 50 to 500 and preferably 150 to 300 ° C for 1 minute to 1 hour. When using pure fabrics or fleeces repeated coating is preferred.

The membranes according to the invention represent a new class of proton-conducting Membranes. These membranes can be used as a proton exchange membrane Fuel cells or in membrane electrode assemblies (MEA) can be used. To this Fuel cells are available which are a membrane according to the invention have a proton-exchanging membrane.

A membrane electrode unit according to the invention is described below. The Flexible membrane electrode assembly for a fuel cell comprises an anode layer and a cathode layer, each on opposite sides of an inventive proton-conducting membrane (electrolyte membrane), comprising a flat, with a variety apertured, flexible substrate with one on and in that substrate Coating, wherein the material of the substrate is selected from woven or non-woven, non-electrically conductive fibers of glass or ceramic or a combination such materials and a coating the proton-conducting nanoscale particles of Zirconium phosphate with a primary particle size smaller than 5 µm and gas-tight or impermeable to the reaction components in a fuel cell, such as. B. hydrogen, Oxygen, air and / or methanol is provided, and the anode layer and the Are porous cathode layer and each have a catalyst for the anode and Cathode reaction, a proton conductive component and optionally a catalyst support include.

• a) eine immobilisierte Hydroxysilylalkylsäure von Schwefel oder Phosphor oder ein Salz davon sowie gegebenenfalls ein Oxid von Aluminium, Silizium, Titan, Zirkonium und/oder Phosphor, und/oder
• b) eine Brönstedsäure und ein Oxid von Aluminium, Silizium, Titan, Zirkonium, und/oder Phosphor.

The proton-conductive component of the anode and / or cathode layer preferably each comprises

• a) 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
• b) a Bronsted acid and an oxide of aluminum, silicon, titanium, zirconium, and / or phosphorus.

The Bronsted acid can e.g. B. sulfuric acid, phosphoric acid, perchloric acid, nitric acid, Hydrochloric acid, sulfurous acid, phosphorous acid and esters thereof and / or one be monomeric or polymeric organic 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 -O _b -P (O _c R ³ ) O ₂ ^- } _a ] _x M ^{x +} (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 formula n


stands,
in which
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, with the proviso that
y + z = 4 - a,
b, c = 0 or 1,
R, R ^{2 are the} same or different and stand for 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 preferred Trihydroxysilylpropylsulfonic acid, trihydroxysilylpropylmethylphosphonic acid or Dihydroxysilylpropylsulfondisäure. Preferably the hydroxysilylalkyl acid is sulfur or Phosphorus or a salt thereof with a hydrolyzed compound of the phosphorus or a hydrolyzed nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, Acetylacetonate of a metal or semi-metal immobilized. In another preferred The embodiment is the hydroxysilylalkyl acid of sulfur or phosphorus or Salt thereof with a hydrolyzed compound obtained from titanium propylate, titanium ethylate, Tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), zirconium nitrate, Zirconium oxynitrate, zirconium propylate, zirconium acetate, zirconium acetylacetonate, Phosphoric acid methyl ester, diethyl phosphite (DEP) or diethyl ethyl phosphonate (DEEP) immobilized.

The proton-conductive component of the anode and / or cathode layer may also include proton-conducting materials selected from titanium phosphates, Titanphosphonaten, zirconium phosphates, Zirkoniumphosphonaten, iso- and heteropoly acids, preferably tungstophosphoric acid or silicotungstic acid, or nano-crystalline metal oxides and Al ₂ O ₃ - ZrO ₂ -, TiO ₂ or SiO ₂ powder are preferred.

The membrane electrode assembly according to the invention can preferably be used in a fuel cell at a temperature of at least 80 ° C, preferably at least 100 ° C, and completely are particularly preferably operated at at least 120 ° C. The fuel can be pure Hydrogen or can be used via a hydrogen produced by means of a reformer. In In a preferred embodiment, however, methanol is used. For this purpose, the On the anode side, a liquid or gaseous mixture of water and methanol is preferred 0.5-5% methanol used. The membrane electrode assembly according to the invention is still preferably flexible and preferably tolerates a bending radius of down to 5000 mm, preferably 100 mm, in particular from down to 50 mm and particularly preferably down to to 20 mm. The inventive method very particularly preferably tolerates Membrane electrode unit has a bending radius of down to 5 mm.

The catalyst may be the same on the anode and cathode sides, in the preferred one The embodiment is different. In a preferred embodiment, the Catalyst carrier in the anode layer and in the cathode layer electrically conductive.

To manufacture the membrane electrode assembly, an electrolyte membrane is inserted through a suitable process coated with the catalytically active electrode material.

The electrolyte membrane can be provided with the electrode in various ways. The way and the order of how the electrically conductive material, catalyst, Electrolyte and any other additives that may be applied to the membrane are at will of the specialist. You just have to make sure that the interface Gas space / catalyst (electrode) / electrolyte is formed. In a special case, the electrically conductive material is omitted as a catalyst carrier, in this case the electrically conductive catalyst directly for the derivation of the electrons from the Membrane electrode assembly.

• A) Bereitstellung einer für die Reaktionskomponenten der Brennstoffzellenreaktion undurchlässigen, protonenleitfähigen, erfindungsgemäßen Elektrolytmembran für eine Brennstoffzelle,
• B) Bereitstellung jeweils eines Mittels zur Herstellung einer Anodenschicht und einer Kathodenschicht, wobei das Mittel jeweils umfasst:
  • 1. eine kondensierbare Komponente, die nach der Kondensation der Elektrodenschicht Protonenleitfähigkeit verleiht,
  • 2. einen Katalysator, der die Anodenreaktion bzw. die Kathodenreaktion katalysiert, oder eine Vorstufenverbindung des Katalysators,
  • 3. gegebenenfalls einen Katalysatorträger und
  • 4. gegebenenfalls einen Porenbildner,
• C) Aufbringen der Mittel aus Stufe (B) auf jeweils eine Seite der Elektrolytmembran aus Stufe (A) zur Bildung einer Beschichtung,
• D) Schaffung eines festen Verbundes zwischen den Beschichtungen und der Elektrolytmembran unter Ausbildung einer porösen, protonenleitfähigen Anodenschicht oder Kathodenschicht, wobei die Ausbildung der Anodenschicht und der Kathodenschicht gleichzeitig oder nacheinander erfolgen kann.

The method according to the invention for producing a membrane electrode unit according to the invention comprises the following steps:

• A) provision of a proton-conductive electrolyte membrane according to the invention for a fuel cell, which is impermeable to the reaction components of the fuel cell reaction,
• B) Provision in each case of an agent for producing an anode layer and a cathode layer, the agent in each case comprising:
  • 1. a condensable component which gives proton conductivity after the condensation of the electrode layer,
  • 2. a catalyst which catalyzes the anode reaction or the cathode reaction, or a precursor compound of the catalyst,
  • 3. optionally a catalyst support and
  • 4. if necessary, 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 with the formation of a porous, proton-conductive anode layer or cathode layer, it being possible for the anode layer and the cathode layer to be formed simultaneously or in succession.

The application of the agent in step (C) can, for. B. by printing, pressing, Pressing in, rolling up, knife application, spreading on, dipping, spraying or pouring on.

• 1. Herstellung eines Sols, umfassend
  eine Hydroxysilylalkylsäure des Schwefels oder Phosphors bzw. deren Salz und gegebenenfalls eine die Hydroxysilylalkylsäure des Schwefels oder Phosphors bzw. deren Salz immobilisierende hydrolysierbare Verbindung des Phosphors
  oder ein hydrolysierbares Nitrat, Oxynitrat, Chlorid, Oxychlorid, Carbonat, Alkoholat, Acetat, Acetylacetonat eines Metalls oder Halbmetalls, vorzugsweise Phosphorsäuremethylester, Diethylphosphit (DEP), Diethylethylphosphonat (DEEP), Titanpropylat, Titanethylat, Tetraethylorthosilikat (TEOS) oder Tetramethylorthosilikat (TMOS), Zirkoniumnitrat, Zirkoniumoxynitrat, Zirkoniumpropylat, Zirkoniumacetat oder Zirkoniumacetylacetonat,
• 2. Dispergieren des Katalysators und gegebenenfalls des Katalysatorträgers und Porenbildners in dem Sol aus (S1).

The agent according to step (B) for producing an anode layer or a cathode layer is preferably a suspension which is obtainable from

• 1. Preparation of a sol, comprising
  a hydroxysilylalkyl acid of sulfur or phosphorus or its salt and optionally a hydrolyzable compound of phosphorus immobilizing 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 methylphosphate, diethylphosphite (DEP), diethylethylphosphonate (DEEP), titanium propylate, titaniumethylate, tetraethylorthosilicate (TEOS) or tetraethyl orthosilicate (TEOS) or Zirconium nitrate, zirconium oxynitrate, zirconium propylate, zirconium acetate or zirconium acetylacetonate,
• 2. Dispersing the catalyst and optionally the catalyst support and pore former in the sol from (S1).

• 1. Hydrolyse einer hydrolysierbaren Verbindung zu einem Hydrolysat, wobei die hydrolysierbare Verbindung ausgewählt ist aus
  einer hydrolysierbaren Verbindung des Phosphors oder
  hydrolysierbaren Nitraten, Oxynitraten, Chloriden, Oxychloriden, Carbonaten, Alkoholaten, Acetaten, Acetylacetonaten eines Metalls oder Halbmetalls, vorzugsweise Aluminium-alkoholaten, Vanadium-alkoholaten, Titanpropylat, Titanethylat, Zirkoniumnitrat, Zirkonium-oxynitrat, Zirkoniumpropylat, Zirkoniumacetat oder Zirkoniumacetylacetonat, oder
  Metallsäuren des Aluminiums, Siliziums, Titans, Vanadiums, Antimons, Zinns, Bleis, Chroms, Wolframs, Molybdäns, Mangans, wobei Wolframphosphorsäure und Siliziumwolframsäure bevorzugt ist,
• 2. Peptisierung des Hydrolysats mit einer Säure zu einer Dispersion,
• 3. Vermischen der Dispersion mit einem nanokristallinen protonenleitenden Metalloxid, vorzugsweise Al₂O₃-, ZrO₂-, TiO₂- oder SiO₂-Pulver,
• 4. Dispergieren des Katalysators und gegebenenfalls des Trägers und Porenbildners.

The agent according to step (B) for producing an anode layer or a cathode layer is very particularly preferably a suspension which is obtainable by

• 1. 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 or zirconium acetate or zirconium acetate
  Metal acids of aluminum, silicon, titanium, vanadium, antimony, tin, lead, chromium, tungsten, molybdenum, manganese, with tungsten phosphoric acid and silicon tungsten acid being preferred,
• 2. peptizing the hydrolyzate with an acid to form a dispersion,
• 3. Mixing the dispersion with a nanocrystalline proton-conducting metal oxide, preferably Al ₂ O ₃ , ZrO ₂ , TiO ₂ or SiO ₂ powder,
• 4. Dispersing the catalyst and optionally the carrier and pore former.

It can be advantageous if the means for producing an anode layer and a Cathode layer can be printed in step (C) and to create a firm bond between the coatings and the electrolyte membrane to form a porous, proton conductive anode layer or cathode layer in step (D) to a temperature from 100 to 800 ° C, preferably 150 to 500 ° C, very particularly preferably 180 to 250 ° C is heated.

• 1. Aufbringen des Mittels zur Herstellung einer Anodenschicht oder Kathodenschicht auf eine Stützmembran, vorzugsweise aus Polytetrafluorethylen,
• 2. Antrocknen der unter (M1) erhaltenen Beschichtung,
• 3. Aufpressen der angetrockneten Beschichtung auf die Elektrolytmembran bei einer Temperatur von 20 bis 500°C, vorzugsweise 50 bis 300°C, ganz besonders bevorzugt 100 bis 200°C,
• 4. Entfernen der Stützmembran insbesondere durch mechanisches Ablösen, chemisches Auflösen, oder Pyrolisieren oder
• 5. Aufbringen des Mittels zur Herstellung einer Anodenschicht oder Kathodenschicht auf eine Stützmembran, vorzugsweise aus Kohlepapier oder einem elektrisch leitfähigen Vlies oder Gewebe,
• 6. Antrocknen der unter (N1) erhaltenen Beschichtung zur Herstellung einer beschichteten Stützmembran,
• 7. Aufpressen der beschichteten Stützmembran auf die Elektrolytmembran bei einer Temperatur von Raumtemperatur bis 500°C, vorzugsweise 50 bis 300°C, ganz besonders bevorzugt 100 bis 200°C umfassen.

The method according to the invention can also include the steps:

• 1. Applying the agent for producing an anode layer or cathode layer to a support membrane, preferably made of polytetrafluoroethylene,
• 2. drying of the coating obtained under (M1),
• 3. pressing the dried coating onto the electrolyte membrane at a temperature of 20 to 500 ° C., preferably 50 to 300 ° C., very particularly preferably 100 to 200 ° C.,
• 4. Removing the support membrane, in particular by mechanical detachment, chemical dissolving, or pyrolizing or
• 5. 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 or fabric,
• 6. drying of the coating obtained under (N1) to produce a coated support membrane,
• 7. Press the coated support membrane onto the electrolyte membrane at a temperature from room temperature to 500 ° C., preferably 50 to 300 ° C., very particularly preferably 100 to 200 ° C.

• a) ein Katalysatormetallsalz, vorzugsweise Hexachloroplatinsäure umfasst
• b) nach dem Aufbringen der Mittel durch Schritt (C) das Katalysatormetallsalz zu einem Katalysator, der die Anodenreaktion oder die Kathodenreaktion katalysiert, reduziert wird,
• c) in Schritt (D) eine offenporige Gasdiffusionselektrode, vorzugsweise ein offenporiges Kohlepapier, auf den Katalysator aufgepresst oder mit einem elektrisch leitfähigen Klebstoff auf den Katalysator geklebt wird.

It can be advantageous if in step (B) the agent is provided in each case when providing an agent for producing an anode layer and a cathode layer

• a) comprises a catalyst metal salt, preferably hexachloroplatinic acid
• b) after the 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,
• c) in step (D), an open-pore gas diffusion electrode, preferably an open-pore carbon paper, is pressed onto the catalyst or glued to the catalyst with an electrically conductive adhesive.

The inventive method can be carried out so that the application of the Repeatedly carried out by means of producing an anode layer or cathode layer and optionally a drying step, preferably at an elevated temperature in a range from 20 to 500 ° C, preferably from 50 to 300 ° C and very particularly preferably at an elevated temperature of 100 to 200 ° C between the repeated The application is carried out.

It can be advantageous if the agent is used to produce an anode layer or cathode layer on a flexible electrolyte membrane unrolled from a first roll or flexible support membrane. In particular, it can be advantageous if the Application of the agent for producing an anode layer or cathode layer done continuously. It can be particularly advantageous if the application of the agent for Production of an anode layer or cathode layer on a heated electrolyte or Support membrane is made.

To create a firm bond between the coatings and the The composite electrolyte membrane is preferably, at a temperature of 20 to 500 ° C, preferably 50 to 300 ° C, most preferably 100 to 200 ° C heated. The heating can by means of heated air, hot air, infrared radiation or microwave radiation.

In a special embodiment, the membrane electrode assembly is manufactured on the electrolyte membrane according to the invention the catalytically active (Gas diffusion) electrodes built. For this purpose, an ink made of a soot catalyst powder and produced at least one proton-conducting material. The ink can also do more Contain additives that improve the properties of the membrane electrode assembly. The soot can also be caused by other electrically conductive materials (such as metal powder, Metal oxide powder, carbon, coal) can be replaced. In a special embodiment, as A metal or semimetal oxide powder (such as Aerosil) instead of carbon black used. This ink is then, for example, screen printed, knife-coated, sprayed on, Rolled on or applied to the membrane by dipping.

The ink can contain all proton-conducting materials that are also used to infiltrate the carrier. The ink can thus contain an acid or its salt, which is immobilized by a chemical reaction in the course of a solidification 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 ₂ , ZrO ₂ , TiO ₂ are used, which are also added via molecular precursors of the ink.

In contrast to the proton conductive coating of the electrolyte membrane, which for the Reaction components of the fuel cell reaction must be impermeable, both Both cathode and anode have a large porosity so that the reaction gases, such as Hydrogen and oxygen, without inhibiting mass transfer to the catalyst interface and electrolyte can be introduced. This porosity can be measured, for example Use of metal oxide particles with a suitable particle size and of organic pore formers in the ink or by a suitable solvent content in the Affect ink.

• 1. eine kondensierbare Komponente, die nach der Kondensation einer Anodenschicht oder einer Kathodenschicht einer Membranelektrodeneinheit einer Brennstoffzelle Protonenleitfähigkeit verleiht,
• 2. einen Katalysator, der die Anodenreaktion oder die Kathodenreaktion in einer Brennstoffzelle katalysiert, oder eine Vorläuferverbindung des Katalysators,
• 3. gegebenenfalls einen Katalysatorträger
• 4. gegebenenfalls einen Porenbildner, und
• 5. gegebenenfalls Additive zur Verbesserung von Schaumverhalten, Viskosität und Haftung.

A medium comprising the following components can be used as the special ink:

• 1. a condensable component which, after the condensation of an anode layer or a cathode layer of a membrane electrode assembly, imparts proton conductivity to a fuel cell,
• 2. a catalyst which catalyzes the anode reaction or the cathode reaction in a fuel cell, or a precursor compound of the catalyst,
• 3. optionally a catalyst support
• 4. optionally a pore former, and
• 5. optionally additives to improve foam behavior, viscosity and adhesion.

• A) hydrolysierbaren Verbindung des Phosphors und/oder
  hydrolysierbaren Nitraten, Oxynitraten, Chloriden, Oxychloriden, Carbonaten, Alkoholaten, Acetaten, Acetylacetonaten eines Metalls oder Halbmetalls, vorzugsweise Aluminium-alkoholaten, Vanadium-alkoholaten, Titanpropylat, Titanethylat, Zirkoniumnitrat, Zirkonium-oxynitrat, Zirkoniumpropylat, Zirkoniumacetat oder Zirkoniumacetylacetonat, und/oder
  Metallsäuren des Aluminiums, Titans, Vanadiums, Antimons, Zinns, Bleis, Chroms, Wolframs, Molybdäns, Mangans, wobei Wolframphosphorsäure und Siliziumwolframsäure bevorzugt sind, und/oder
• B) einer immobilisierbaren Hydroxysilylalkylsäure von Schwefel oder Phosphor oder ein Salz davon und in einer besonders bevorzugten Ausführungsform zusätzlich eine die Hydroxysilylalkylsäure des Schwefels oder Phosphors bzw. deren Salz immobilisierende hydrolysierbare Verbindung des Phosphors oder ein hydrolisierbares Nitrat, Oxynitrat, Chlorid, Oxychlorid, Carbonat, Alkoholat, Acetat, Acetylacetonat eines Metalls oder Halbmetalls, vorzugsweise Phosphorsäuremethylester, Diethylphosphit (DEP), Diethylethylphosphonat (DEEP) Titanpropylat, Titanethylat, Tetraethylorthosilikat (TEOS) oder Tetramethylorthosilikat (TMOS), Zirkoniumnitrat, Zirkoniumoxynitrat, Zirkoniumpropylat, Zirkoniumacetat oder Zirkoniumacetylacetonat.

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

• A) 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 or zirconium acetate or zirconium acetate or zirconium acetate or zirconium acetate or zirconium acetate or zirconium acetate
  Metal acids of aluminum, titanium, vanadium, antimony, tin, lead, chromium, tungsten, molybdenum, manganese, with tungsten phosphoric acid and silicon tungsten acid being preferred, and / or
• B) an immobilizable hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof and, in a particularly preferred embodiment, additionally a hydrolyzable compound of phosphorus immobilizing 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 methyl phosphate, diethylphosphite (DEP), diethylethylphosphonate (DEEP) titanium propylate, titanium ethylate, tetraethylorthosilicate (TEOS) or tetramethylorthosilicate (TMOS), zirconium nitrate, zirconium oxynium acetate, zirconium oxonium acetate.

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 contain or -phosphonates.

The catalyst or the precursor compound of the catalyst preferably comprises platinum, Palladium and / or ruthenium or an alloy containing one or more of these metals contains.

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

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

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

However, it is also possible to deposit the catalyst directly on the membrane and with a open-pore gas diffusion electrode (such as an open-pore carbon paper). For this purpose, e.g. B. applied a metal salt or an acid to the surface and in one second step to be reduced to metal. For example, platinum can be Apply hexachloroplatinic acid and reduce to metal. In the last step the Lead electrode by a pressing process or by an electrically conductive adhesive fixed. The solution containing the metal precursor can also be a compound contain, which is already proton conductive or at least at the end of the manufacturing process is ionic. Suitable materials come again from those already mentioned above proton-conducting substances in question.

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

The electrolyte membranes according to the invention can, for. B. in a fuel cell, especially in a direct methanol fuel cell or a reformate fuel cell be used. In particular, the electrolyte membrane according to the invention can Manufacture of a membrane electrode assembly, a fuel cell, or one Fuel cell stacks are used.

The electrolyte membrane according to the invention and the one according to the invention Membrane electrode unit can be used in particular for producing a fuel cell or a Fuel cell stacks are used, the fuel cell in particular a direct methanol Fuel cell or a reformate fuel cell that is used in a vehicle.

Accordingly, there are also fuel cells with an electrolyte membrane according to the invention and / or a membrane electrode unit according to the invention the subject of the present Invention and thus also mobile or stationary system with a membrane electrode unit, a fuel cell or a fuel cell stack containing an inventive Electrolyte membrane or a membrane electrode assembly according to the invention. Preferably are the mobile or stationary systems vehicles or home energy systems.

example 1

3 wt .-% aqueous solutions of phosphoric acid and zirconium nitrate were by 300 µm nozzles at a pressure of 60 bar in a microjet reactor according to WO 00/61275 shot at each other. The product obtained was opaque / milky-cloudy. The Particle size distribution showed a bimodal distribution of particles with a size of around 0.7 µm as well as a smaller proportion of particles with a size of just under 3 µm. This Suspension was removed by spinning off water to a concentration of about 10% by weight concentrated, whereby the suspension becomes sol-like / viscous, but remains milky / opaque. This Sol or this suspension is long-term stable and was used later.

Example 2

Aqueous solutions of phosphoric acid (0.2 M) and zirconium nitrate (0.05 M) were made by 100 µm nozzles at a pressure of 60 bar in a microjet reactor according to WO 00/61275 shot at each other. The product obtained is opaque / milky-cloudy. The Particle size distribution shows a distribution comparable to that of Example 1. The suspension can be passed through Concentrate the spinning off of water and becomes sol-like / viscous, but remains milky / opaque. This sol or suspension is long-term stable.

Example 3

After concentration, 5% by weight of Aerosil 200 are added to the suspension from Example 1 (Degussa AG) added. This suspension is then again for 24 h with a Homogenized magnetic stirrer.

Example 4

50 g of the suspension from Example 1 are mixed with 5 g of Al ₂ O ₃ and 0.23 g of TODS (2- [2- (2-methoxyethoxy) ethoxy] acetic acid). A S2 glass fabric is coated with this slip in a continuous process and dried at 150 to 200 ° C. within 5 minutes. The membrane has an unexpectedly high conductivity of 0.2 mS / cm and is flexible.

Example 5

With the suspension from Example 1, a glass fabric was directly in a continuous Process coated. For this, the suspension was placed on a S2 glass fabric (CS interglass) doctored and solidified at a temperature of 160 ° C within 10 minutes. The membrane obtained shows a good conductivity of about 1 mS / cm. The membrane shows one similarly good flexibility as the original fabric.

Example 6

A glass fabric is coated directly with a doctor knife using the suspension from Example 2. The membrane is then solidified at 300 ° C for 15 minutes in a chamber furnace. The afterwards water-insoluble membrane has a conductivity of approx. 2 mS / cm at 92% relative Humidity (RH) and 23 ° C. Due to the resistance in water and methanol this is Membrane very suitable for the DMFC.

Example 7

An S-glass fabric with a thickness of 70 μm is passed through with the suspension from Example 1 infiltrated a five-time squeegee process. Between the infiltration steps, that is Pre-consolidated tissue with a hot air blower at approx. 150 ° C. After the last one Coating, in which the last small pores are filled, becomes the membrane finally 300 ° C for 15 minutes solidified by hot air. This membrane is stable in water and methanol has a conductivity of approx. 4 mS / cm at 80% relative humidity and can be used in one DMFC can be used.

Example 8

An S-glass fabric with a thickness of 70 μm is passed through with the suspension from Example 3 infiltrated a three-time squeegee process. Between the infiltration steps, that is Pre-consolidated tissue with a hot air blower at approx. 150 ° C. After the last one Coating, in which the last small pores are filled, becomes the membrane finally 300 ° C for 15 minutes solidified by hot air. This membrane is stable in water and methanol has a conductivity of approx. 1 mS / cm at 80% relative humidity and can be used in one DMFC can be used.

Claims (47)

1. Proton-conducting membrane, comprising a flat, provided with a plurality of openings, flexible substrate with a coating on and in this substrate, the material of the substrate being selected from woven or non-woven, non-electrically conductive fibers of glass or ceramic or one Combination of such materials, characterized in that the coating has proton-conducting nanoscale particles of zirconium phosphate with a primary particle size of less than 5000 nm and is impermeable to the reaction components in a fuel cell. 2. Proton-conducting membrane according to claim 1, characterized, that the membrane has a thickness of less than 100 microns. 3. Proton-conducting membrane according to claim 2, characterized, that the membrane has a thickness of less than 50 microns. 4. Proton-conducting membrane according to one of claims 1 to 3, characterized in that the fibers are selected from glass, aluminum oxide, SiO ₂ , SiC, Si ₃ N ₄ , BN, B ₄ N, AlN, Sialone or ZrO ₂ . 5. Proton-conducting membrane according to at least one of claims 1 to 4, characterized, that the material of the substrate is a glass fiber woven or nonwoven made of woven or is non-woven glass fiber. 6. Proton-conducting membrane according to claim 5, characterized, that the fibers are selected from E, R, ECR or S glass. 7. Proton-conducting membrane according to claim 6, characterized in that the filaments are coated with SiO ₂ , ZrO ₂ , TiO ₂ or Al ₂ O ₃ or with mixtures of these oxides. 8. Proton-conducting membrane according to claim 6 or 7, characterized, that the glass fiber fabric was made from 2 to 20 tex yarns. 9. proton-conducting membrane according to claim 8, characterized, that the glass fiber fabric was made from 5.5 or 11 tex yarns. 10. proton-conducting membrane according to at least one of claims 1 to 9, characterized, that the coating on and in the substrate is an oxide, nitride, carbide Metals Al, Zr, Si, or Ti. 11. Proton-conducting membrane according to at least one of claims 1 to 10, characterized, that the membrane has a tensile strength of at least 5 N / cm up to 500 N / cm. 12. Proton-conducting membrane according to at least one of claims 1 to 11, characterized, that the membrane can be bent down to 5 mm on any radius without damage. 13. Proton-conducting membrane according to at least one of claims 1 to 12, characterized, that coating nanoscale zirconium phosphate particles with a particle size from 1 to 1000 nm. 14. Proton-conducting membrane according to claim 13, characterized, that the membrane has a proton conductivity of greater than 1 mS / cm. 15. Proton-conducting membrane according to at least one of claims 1 to 14, characterized, that the coating, in addition to the nanoscale zirconium phosphate particles, at least has an oxide of the elements Al, Zr, Si, and / or Ti. 16. A method for producing a proton-conducting membrane according to at least one of the Claims 1 to 15, wherein a flat, provided with a plurality of openings, flexible substrate is provided in and on this substrate with a coating, wherein the material of the substrate is woven or non-woven, non-electrically conductive fibers Glass or ceramic or a combination of such materials, characterized, that by applying a suspension or sol, at least has nanoscale zirconium phosphate particles on the substrate and by at least single heating, in which the suspension or the sol on and in the substrate is solidified, a coating is applied. 17. The method according to claim 16, characterized, that the suspension or sol is rolled up by printing, pressing, pressing, Knife, spread, dip, spray or pour onto the substrate becomes. 18. The method according to at least one of claims 16 or 17, characterized in that the fibers of the substrate are selected from glass, aluminum oxide, SiO ₂ , SiC, Si3N4, BN, B ₄ N, AlN, Sialone or ZrO ₂ . 19. The method according to at least one of claims 16 to 18, characterized, that as the material of the substrate a glass fiber fabric or nonwoven made of woven or non-woven glass fibers are used. 20. The method according to claim 19, characterized, that as a material of the substrate provided with a porous ceramic coating Glass fiber textile is used. 21. The method according to at least one of claims 16 to 20, characterized, that the nanoscale zirconium phosphate particles are used to make the suspension Shoot one another in a suitable solvent Zirconium compound and a solution containing phosphorus-containing compounds in one Microjet reactor are generated. 22. The method according to claim 21, characterized, that the soluble zirconium compound used is selected from zirconium nitrate, Zirconium chloride, zirconium acetate, zirconium acetylacetonate or one Zirconium alcoholate. 23. The method according to claim 22, characterized, that the solution containing phosphorus compounds used has at least one Compound selected from phosphoric acid or phosphate salt. 24. The method according to at least one of claims 16 to 23, characterized, that the suspension or sol used, the or the nanoscale Has zirconium phosphate particles, a sol of at least one metal, semimetal or Mixed metal or a mixture of these brine. 25. The method according to claim 24, characterized, that the brine by hydrolyzing at least one metal compound, at least one Semimetal compound or at least one mixed metal compound with water, Water vapor, ice or an acid or a combination of these compounds can be obtained. 26. The method according to claim 25, characterized, that at least one metal alcoholate compound or at least one Semi-metal alcoholate compound selected from the alcoholate compounds of the elements Zr, Al, Si, and Ti or at least one, acetate, acetylacetonate, nitrate, carbonate or halide is hydrolyzed from the metal or semimetal salts of the elements Zr, Al, Si, and Ti. 27. The method according to at least one of claims 16 to 26, characterized, that the suspension has at least one oxide selected from the oxides of the elements Zr, Al, Ti, or Si, has suspended. 28. The method according to claim 27, characterized, that the mass fraction of the suspended oxides 0.1 to 10 times that used Mass fraction of zirconium phosphate corresponds. 29. The method according to at least one of claims 16 to 28, characterized, that the suspension or the sol present on and in the support by heating up a temperature of 50 to 500 ° C, preferably from 150 to 300 ° C is solidified. 30. The method according to claim 29, characterized, that the heating takes place for 1 second to 10 minutes. 31. Membrane electrode unit for a fuel cell, with an electrically conductive Anode and cathode layers, each on opposite sides of one proton-conducting membrane are arranged and wherein the membrane is a flat, with a plurality of openings provided, flexible substrate with one on and in this Coating located substrate, wherein the material of the substrate selected is made of woven or non-woven, non-electrically conductive fibers of glass or Ceramic or a combination of such materials and the coating proton-conducting nanoscale particles of zirconium phosphate with a Primary particle size less than 5000 nm and the membrane impermeable to Reaction components in a fuel cell, in particular according to one of claims 1 to 15, wherein the anode layer and the cathode layer are porous and one each Catalyst for the anode and cathode reaction, a proton conductive component and optionally include a catalyst support. 32. Membrane electrode unit according to claim 31, wherein the proton-conductive component of the anode and / or cathode layer and / or the electrolyte membrane each comprises a) 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 b) a Bronsted acid and an oxide of aluminum, silicon, titanium, zirconium, and / or phosphorus. 33. membrane electrode assembly according to claim 32, characterized, that the Bronsted acid sulfuric acid, phosphoric acid, perchloric acid, nitric acid, Hydrochloric acid, sulfurous acid, phosphorous acid and esters thereof and / or comprises a monomeric or polymeric organic acid. 34. Membrane electrode unit according to claim 33, 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)

or

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


stands,
in which
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, with the proviso that
y + z = 4 - a,
b, c = 0 or 1,
R, R ^{2 are the} same or different and stand for methyl, ethyl, propyl, butyl or H and
R ^{3 represents} M or a methyl, ethyl, propyl or butyl radical. 35. Membrane electrode unit according to claim 34, wherein the hydroxysilylalkyl acid Sulfur or phosphorus trihydroxysilylpropylsulfonic acid, Trihydroxysilylpropylmethylphosphonic acid or dihydroxysilylpropylsulfonedioic acid. 36. membrane electrode assembly according to one of claims 32, 34 or 35, characterized, that having the hydroxysilylalkyl acid of sulfur or phosphorus or a salt thereof a hydrolyzed compound of phosphorus or a hydrolyzed nitrate, Oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate, acetylacetonate of a metal or semimetal or with a hydrolyzed compound obtained by hydrolysis of 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, zirconium acetylacetonate, Phosphoric acid methyl ester or immobilized with precipitated silica. 37. Membrane electrode unit according to one of claims 32 to 36, characterized in that the proton-conducting component has proton-conducting substances selected from the titanium phosphates, titanium phosphonates, zirconium phosphates, zirconium phosphonates, iso- and heteropolyacids, preferably tungsten phosphoric acid or silicon tungstic acid, or nanocrystalline metal oxides, where Al ₂ O ₃ , ZrO ₂ , TiO ₂ or SiO ₂ powder are preferred. 38. membrane electrode assembly according to one of claims 32 to 37, characterized, that they are at a temperature of at least 80 ° C, preferably at least 100 ° C, and very particularly preferably can be operated at at least 120 ° C. 39. Membrane electrode unit according to one of claims 32 to 38, which has a bending radius from down to 5000 mm, preferably from down to 100 mm, very particularly preferably tolerated from down to 50 mm. 40. Membrane electrode unit according to one of claims 32 to 39, wherein the proton conductive component of the anode layer and the cathode layer the same Have composition. 41. Membrane electrode unit according to one of claims 32 to 40, wherein the anode layer and the cathode layer have different catalysts. 42. Membrane electrode unit according to one of claims 32 to 41, wherein the Catalyst carrier in the anode layer and in the cathode layer is electrically conductive. 43. Use of a membrane according to one of claims 1 to 15 as an electrolyte membrane in a fuel cell. 44. Fuel cell with an electrolyte membrane according to one of claims 1 to 15. 45. Fuel cell with a membrane electrode assembly according to one of claims 32 to 42nd 46. Mobile or stationary system with a membrane electrode assembly, one Fuel cell or a fuel cell stack containing an electrolyte membrane after one of claims 1 to 15 or a membrane electrode assembly according to one of the Claims 32 to 42. 47. Mobile or stationary system according to claim 47, characterized, that the mobile system is a vehicle and the stationary system is a house energy system.