EP1954760A2

EP1954760A2 - Catalytically active composition, membrane-electrode unit comprising the same, and catalyst comprising/made of the same

Info

Publication number: EP1954760A2
Application number: EP06792125A
Authority: EP
Inventors: Michaela Wilhelm; Michael Jeske; Thomas Hesse; Christian Soltmann; Georg Grathwohl; Dietmar Koch
Original assignee: Universitaet Bremen
Current assignee: Universitaet Bremen
Priority date: 2005-09-16
Filing date: 2006-09-18
Publication date: 2008-08-13
Also published as: WO2007031346A3; DE102005044433A1; WO2007031346A2

Abstract

The invention relates to a catalytically active composition comprising at least one polysiloxane, the catalytic effect being created by integrating metallic centers such as platinum, nickel, etc. Also disclosed are a membrane-electrode unit (MEA) comprising said composition as well as a catalyst containing/made of the same. Based on its properties, the inventive catalytically active composition can preferably be used as an electrocatalyst in electrochemical applications, especially in a polymer electrolyte membrane fuel cell (PEMFC), and for reacting inorganic and organic compounds, e.g. when synthesizing organic compounds with the aid of membrane reactors or purifying exhaust gases. The disclosed catalytically active composition contains at least one polysiloxane comprising metal ions and/or metal atoms. In its most simple embodiment, the catalytically active composition can be obtained using a method that comprises a step in which at least one initial organosilicon compound is polymerized in the presence of metal ions. Advantageously, the initial siloxane compound and the metal ions are provided at the most homogeneous possible distribution during the polymerization process.

Description

Rp "rhrpihnnσ

Catalytically active composition, membrane electrode assembly with the composition and catalyst with / from the composition

The present invention relates to a catalytically active composition having at least one polysiloxane, wherein the catalytic effect is produced by incorporation of metallic centers such as platinum, nickel, etc., a membrane-electrode assembly (MEA) with the composition and a catalyst with / from the composition.

Because of its properties, the catalytically active composition is preferred as an electrocatalyst in electrochemical applications, in particular the polymer electrolyte membrane fuel cell (PEMFC) and in the reaction of inorganic and organic compounds, for example in the synthesis of organic compounds using membrane reactors or in the exhaust gas cleaning, use.

The effect of catalysts is known to be due to the fact that they provide a way for chemical reactions to convert the starting materials into the final products by applying a lower activation energy. Such a reaction path is thereby passed through faster. But catalysts not only accelerate a chemical reaction, but can often affect the target of the reaction. Catalysts are therefore of immense importance in all fields in which an accelerated or targeted chemical conversion of

Educts is desirable or necessary.

Catalysts are therefore nowadays in addition to the classical fields of chemistry, such as agrochemicals, pharmaceuticals and plastics industry also fertilize applications in the field of energy sector. The best-known example in the field of environmental Protection should probably be the catalytic purification of car exhaust gases, but also of exhaust gases from power plants and other industrial plants. But also in alternative energies, such as in hydrogen and fuel cell technology, catalytic processes play a crucial role.

In fuel cells, for example, the chemical energy is converted directly into electrical energy by the electrochemical reaction of hydrogen and oxygen, in which case water is formed as the reaction product. Catalysts are involved in both the production of hydrogen (e.g., by methanol reforming) and in the actual fuel cell reaction.

Solid polymer electrolyte membrane fuel cells (e.g., Nafion or polybenzimidazole) contain an anode compartment and a cathode compartment separated by a solid polymer electrolyte membrane. In these two sections, gaseous fuels, such as, for example, hydrogen or methanol on the anode side or oxygen on the cathode side, are generally conducted to a catalytically active material which is located on the surface of the polymer electrolyte membrane. The catalytically active material splits the fuel molecules into cations, anions and electrons.

The catalytic activity of the material is of crucial importance for a sufficiently high rate of half-cell reactions. For a commercially successful use of fuel cells beyond other factors play an essential role, such as the lowest possible cost of producing the catalytically active material, technologically simple application of the catalyst system on the proton-conducting membrane for the preparation of the membrane electrode assembly (MEA) , low sensitivity to poisoning with carbon monoxide, high temperature resistance and chemical resistance as well as a high technical long-term stability of up to 40,000 hours for stationary devices. In addition, the catalyst layer should ideally guarantee a homogeneous transition phase into the electrolyte material. in order to transfer the ions formed in the electrocatalyst layer as quickly and efficiently as possible into the polymer electrolyte membrane.

For the conventional polymer electrolyte membrane fuel cell (PEMFC), various-to-the-area-optimized electrocatalyst systems for the production of fuel cell electrodes are currently commercially available. These systems are mainly graphite-supported platinum-containing materials, some of which have a high precious metal content, which makes their production costly.

Furthermore, the currently commercially available electrocatalyst systems do not satisfactorily meet the requirements for the most homogeneous transition phase between the catalyst layer and the electrolyte material. Such a homogeneous transition phase is necessary in order to transfer the ions formed in the electrocatalyst layer as quickly and efficiently as possible into the polymer electrolyte membrane.

It is therefore an object of the present invention to provide a catalytically active composition, which can be used in particular in a fuel cell electrocatalyst, and an MEA with the composition, in which the above-mentioned disadvantages of the prior art are overcome. Further objects of the present invention are the provision of an improved catalyst, a process for the preparation of a catalytically active composition, a process for the preparation of an MEA, and the use of the catalytically active composition.

These objects are achieved by the catalytically active composition according to claim 1, the membrane electrode assembly (MEA) according to claim 24, the catalysts according to claims 30 and 34, the process for the preparation of a catalytic composition according to claim 37, the process for the preparation an MEA according to claim 42 and the uses of the catalytically active composition according to claims 44 and 46. Preferred embodiments of the present invention are subject-matter of the subclaims. The catalytically active composition of the present invention contains at least one polysiloxane with metal ions and / or metal atoms. In its simplest embodiment, the catalytically active composition is obtainable by a process which comprises a step of polymerizing at least one organosilicon starting compound in the presence of metal ions, the siloxane starting compound and the metal ions advantageously being as homogeneously distributed as possible in the polymerization process available.

In a first preferred embodiment of the catalytically active composition according to the invention, some of the metal ions and / or metal atoms present are complex-bonded to the at least one polysiloxane. Depending on the selected conditions, this part can vary in size and can reach high values of up to 100%. In order to facilitate / facilitate / improve such a complex-like binding of the metal ions and / or metal atoms to the at least one polysiloxane, according to a further preferred embodiment, the polysiloxane of the catalytically active composition according to the invention is obtained from at least one organosilicon compound which contains at least one heteroatom-containing functional group, which is selected from the group consisting of amino, amido, carboxyl, sulfonic acid, thio or cyano group, or a mixture thereof.

Preferred examples of the organosilicon compound are selected from the group consisting of aminopropyltriethoxysilane, aminobutyltriethoxysilane, aminophenoxypropyltrimethoxysilane, aminophenyltrimethoxysilane, aminopropylmethyldiethoxysilane, aminoethylaminopropylmethyldimethoxysilane, trimethoxysilylpropylbenzimidazole-5-amide, trimethoxysilylpropylimidazole-2-amide, trimethoxysilylphenylsulfonic acid , and trimethoxysilylethylphenylsulfonic acid, or a mixture thereof.

Preferred in / on the polysiloxane present and / or complex-like bound thereto

Metal ions and / or metal atoms are selected from the group consisting of platinum, palladium, nickel, ruthenium, iron, copper, zinc, rhenium, rhodium, iridium, Osmium, selenium, titanium, vanadium, chromium, manganese, cobalt, zirconium, molybdenum, cadmium, gold, silver, or a mixture thereof.

The catalytically active composition according to the invention may, in addition to the constituents described above, further comprise at least one component A which contains the

Composition confers electrical conductivity. This component A is preferably selected from the group consisting of electrically conductive carbon components such as e.g. Carbon black or graphite, metal or a conductive polymer, preferably polyaniline,

Polythiophene or polypyrazole, wherein the conductive polymers may optionally be sulfonated, phosphonated, carboxylated and / or doped with at least one of the metals according to claim 5, or a mixture thereof.

However, it is also possible to increase the inherent conductivity of the catalytically active composition, in particular in the case of carbon-rich organosilicon components, when the crosslinking is followed by a temperature treatment (polymer pyrolysis). For this purpose, in the synthesis of the starting mixtures, phenyl-containing organosilicon components or compounds containing longer aliphatic radicals and crosslinkable groups such as alkoxy and chloro groups can be incorporated into the crosslinking reaction and converted into electrically conductive carbon fractions by pyrolysis.

An electrical conductivity of the catalytically active composition according to the invention is advantageous, for example, when the composition is used as an electrocatalyst in an MEA. Electrons produced by catalytic decomposition of the fuel in an electrocatalyst layer can then be dissipated in the electrocatalyst layer itself. When the catalytically active composition according to the invention is used as a catalyst in carrying out reactions of inorganic or organic compounds, for example in the form of a membrane catalyst, electrical conductivity allows the catalyst to be electrically heated. According to a further preferred embodiment, the catalytically active composition of the present invention contains a flexible and / or polymer-modifying polymer. Such a polymer is preferably an organosilicon-derived block copolymer, preferably polydimethylsiloxane, diphenylsiloxane-dimethyl-siloxane-SiOH-terminated, diphenylsiloxane-dimethylsiloxane-vinyl-terminated, where the phenyl-bearing polymers may optionally be sulphonated.

The network and the porosity of the catalytically active matrix of the composition according to the invention can already be preset at the molecular level during the synthesis by selecting the precursors used for crosslinking. Here, by selecting specific molar proportions of di-, tri- or tetrafunctional organosilicon crosslinking components and certain functional side groups, the network can be further modified. The matrix can be modified with regard to mesh size and porosity by targeted process control of the crosslinking by means of variation of the temperature control, the gas throughput as well as the choice of the feed gas for post-crosslinking.

Through this targeted process management, the catalyst material can thus vary from very dense, for example, with hydrogen just penetrated structures up to meso and macroporous structures and optimize them to the respective technical application. This also allows the use as separation-selective and catalytically active membranes.

According to a further preferred embodiment of the catalytically active composition according to the invention, the latter contains at least one component B which confers proton conductivity to the composition. By such a proton conductivity, for example, an intensely acid-catalyzed reaction can be carried out when the catalytically active composition is used in / as a catalyst. If the catalytically active composition is used in an / as an electrocatalyst in an MEA, the most effective possible proton conductivity has the advantage that it improves the transport of the protons generated in this layer to the proton-conductive layer. However, it is understood that all of the above and explained below. Modifications and embodiments of the catalytically active composition can be combined as desired, as required by the particular application. For example, a catalyst in the form of a membrane may contain, in addition to the catalytically active composition, component A for generating electrical conductivity, as well as component B for generating proton conductivity. Such a catalyst, as can be used, for example, in membrane reactors for C-H activation for the synthesis of organic substances, such as the catalytic conversion of olefins to higher hydrocarbons, can then be heated electrically, for example, and at the same time enables an increased acid-catalyzed reaction.

Advantageously, component B is selected from the group consisting of at least one a) proton conductive crosslinked polysiloxane, b) perfluorinated hydrocarbon backbone with sulfonated alkyl ether side groups (e.g., Nafion), c) polybenzimidazole, or a mixture thereof.

In a preferred embodiment, when a crosslinked polysiloxane is included as the proton conductive component in the catalytically active composition, it is a crosslinked proton conductive polysiloxane having a polysiloxane backbone and having heteroatom-containing side chain functional groups, including acidic groups such as sulfonic acid, phosphonic acid. and / or carboxyl groups, which are each bonded to respective Si atoms of the polysiloxane skeleton via an organic spacer, and either (a) nitrogen-containing aromatic heterocycles in the ring, each via an organic spacer comprising an amide function respective Si atoms of the polysiloxane skeleton are bonded, or (b) in the ring nitrogen-containing aromatic heterocycles, which are each bound via an organic spacer to respective Si atoms of the polysiloxane backbone. This crosslinked proton-conducting polysiloxane advantageously comprises nitrogen-containing aromatic heterocycles in the ring, which are each bonded to respective Si atoms of the polysiloxane backbone via an organic spacer comprising an amide function.

Furthermore, in this crosslinked proton-conducting polysiloxane, individual or all of the ring-nitrogen-containing aromatic heterocycles may be selected from the group consisting of optionally substituted benzimidazole and optionally substituted imidazole.

Furthermore, in this crosslinked proton-conducting polysiloxane, individual or all of the ring-containing aromatic heterocycles may each be bonded to respective Si atoms of the polysiloxane backbone via an organic spacer containing 5-10 chain atoms, preferably 5-8, containing an amide function and the respective amide function directly be covalently bonded to the associated heterocycle.

Also, in this crosslinked proton conductive polysiloxane, single or all of the nitrogen-containing aromatic heterocycles in the ring may be bonded to respective Si atoms of the polysiloxane backbone according to the formula Het-C (O) -N (R ³ ) -R ⁴ -Si ^* wherein Het the nitrogen-containing aromatic heterocycle in the ring, R is hydrogen or an aliphatic or aromatic organic radical, R ⁴ is an aliphatic chain and a Si-Si atom of the polysiloxane backbone is.

Furthermore, in the case of this crosslinked proton-conducting polysiloxane, individual or all sulfonic acid, phosphonic acid and / or carboxyl groups may each be directly linked to an aromatic ring, each directly via a chain having 1, 2, 3, 4, 5 or 6 chain atoms is bonded to respective Si atoms of the polysiloxane backbone. It is likewise preferred if the chain between the aromatic ring and the respective Si atom comprises 5 or 6 chain atoms and at least once the chain atom sequence CNC, preferably in the form of the grouping C (O) -NH-C. In the case of the crosslinked proton-conducting polysiloxane described in the preceding paragraphs, the polysiloxane skeleton may have a network structure which can be prepared by hydrolysis and condensation of (i) silanes with four, (ii) silanes with three and optionally additionally of (iii) silanes with two hydrolyzable groups have. In addition to the polysiloxane skeleton can - as already indicated above - other network structures in the crosslinked proton conductive polysiloxane exist, for. B. (in option (a)) as network structures, which are obtained by the polymerization of styryl-functionalized silane (see DE 101 63 518 Al).

When using bifunctionally crosslinkable silanes, such as. B. dimethyldimethoxysilane and diphenyldimethoxysilane whose chlorinated variants such as dimethyldichlorosilane and diphenyldichlorosilane and organosilicon (co) polymers is a widening of the network structure of this crosslinked proton conductive polysiloxane possible, for example, the proton-conducting groups of the polysiloxane, ie the sulfonic acid, phosphonic acid or Carboxyl group as well as the N-heteroaromatic group to give more room for rearrangement reactions. The crosslinked proton conductive polysiloxane then comprises atomic groupings of the type -O-Si (phenyl) ₂ -O- and / or -O-Si (CHa) ₂ -O-.

When using diphenyldimethoxysilane and / or dimethyldimethoxysilane, the crosslinked proton-conductive polysiloxane comprises atomic groups of the type -O-Si (phenyl) 2-O- and / or -O-Si (CH ₃ ) ₂ -O-, which have a flexibilizing effect on the membrane material and Overall, it has a positive influence on its mechanical properties. The phenyl groups may also be substituted by sulfonic acid groups.

In the cross-linked proton-conductive polysiloxane described herein, the ratio of (i) the ring-nitrogen-containing aromatic heterocycles to (ii) the sulfonic acid, phosphonic acid and / or carboxyl groups can range from 3: 1 to 1: 2, where preferably in the range of 3: 1 to 1: 1. If a particularly good proton conductivity is desired for the crosslinked proton-conductive polysiloxane, it is possible to incorporate into the crosslinked polysiloxane iridazole. Advantageously, synthesis routes are selected for the synthesis of the crosslinked proton-conductive polysiloxanes, in which imidazole is formed as a by-product, which can then be kept at least partially in the membrane network during crosslinking.

An exemplary process for preparing a crosslinked proton conductive polysiloxane comprises the steps of hydrolyzing and condensing a mixture dissolved in a liquid comprising (i) a silane bearing a sulfonic acid, phosphonic acid or carboxyl group, (ii) a nitrogen-containing aromatic hetero - Cyclus comprehensive silane and optionally (iii) further silanes, wherein (a) the nitrogen-containing heterocycle of a nitrogen-containing heterocycle silane is bound via an amide-functional organic spacer to the associated silane Si atom. Advantageously, the silane bearing a sulfonic acid, phosphonic acid or carboxyl group is selected from the group of silanes of the formula wherein P is HOSO ₂ -R ² - or HOCO-R ² -, wherein R ^{2 is} an aliphatic or aromatic organic radical or comprises such and P is bonded via this to the silicon, R ^{1 is} a carbon bonded to the silicon X represents a hydrolysis-sensitive group, a is 1, 2 or 3, b is 0, 1 or 2 and a + b together are 1, 2 or 3.

The radical R ² is preferably an aromatic-aliphatic radical which has, via its aromatic part, the sulfonic acid group HOSO ₂ -, phosphonic acid group (HO) ₂ PO- or the carboxyl group HOCO- and via its aliphatic part with the Silicon is connected.

Contains a nitrogenous in the ring aromatic heterocycle comprising silane is preferably selected from the group of silanes of the formula Het-C (O) -N (R ³⁾ -R ⁴ - SiX _3-a R ⁵ _a, wherein Het is the nitrogen-containing in the ring aromatic Heterocycle, R ³ and R ^{5 are} independently hydrogen or an aliphatic or aromatic organic R ⁴ and R ^{4 is} an aliphatic chain having 5-10 chain atoms, preferably 5-8 chain atoms.

The crosslinked proton-conducting polysiloxane is based - as well as products and processes from the prior art - on the use of organosilicon monomers which are predominantly of the general type R ₂ SiX ₂ , RSiX ₃ and SiX ₄ (X = -OR ', -Cl , with R '= organic radical) and in addition to hydrolysis-stable, organic radicals R have at least two hydrolyzable Si-X bonds. Such siloxanes are commercially available with a wide range of organic radicals and thus open up the possibility of developing materials that are specifically adapted to the respective requirements not only cheaper than previous, but also with high flexibility by means of combinatorial methods. The linking of the monomers mentioned takes place via an acid or base-catalyzed hydrolysis / condensation reaction, as illustrated in equation 1 by way of example for a compound of the type RSi (OR ') ₃ . In the course of the reaction, first reactive silanols are formed, which then undergo dehydration (condensation) to give off Si-O-Si-linked polysiloxanes (sol-gel process). It is also possible to use silanes that (additionally) carry vinyl radicals. In this case, a radical reaction or a platinum-catalyzed hydrosilylation for crosslinking, which leads to (additional) linkage sites, can additionally be used, cf. the example given in Equation 2 for radical crosslinking.

The degree of crosslinking of the polysiloxane skeletons and thus the material properties of the linked proton-conductive polysiloxanes such. B. the temperature resistance, Tightness and flexibility can be controlled in a wide range by suitable selection of the number of etching groups in the silane bodies. Thus, compounds such as SiX ₄ , which do not carry Si-bonded organic radicals, function as pure crosslinking components and produce close-meshed, often non-plastic microstructures. In contrast, R ₂ SiX ₂ components merely crosslink two-dimensionally into linear chains, which can thus make a polymer matrix more widely meshed and thus plastically deformable. Further above, according to the invention, particularly preferred components of the type R ₂ SiX _{2 have been} specified and discussed.

To increase the hydrophilicity of a crosslinked proton-conductive polysiloxane, it may be useful to incorporate into the network compounds whose hydrophilic character is particularly pronounced. In particular, N- (3-triethoxysilylpropyl) -gluconamide can be integrated via a hydrolysis-condensation reaction into the siloxane backbone of a crosslinked proton-conductive polysiloxane so as to increase the hydrophilicity.

For the preparation of the crosslinked proton-conductive polysiloxanes, as stated above, silanes bearing sulfonic acid, phosphonic acid and / or carboxyl groups are used, inter alia.

Silanes carrying sulfonic acid, phosphonic acid or carboxyl groups can be prepared by using the azolide method starting from carboxylic acid derivatives of the aromatic sulfonic acids (such as sulfobenzoic acid) or carboxylic acids. The azolide method, which is used as described above for the attachment of sulfonic acid or carboxyl groups to silanes, has been described for a variety of compounds in H. A. Staab, Angew. Chemie 1962, 74, 407 and H.A. Staab, H. Bauer, K. Schneider, Azolides in Organic Synthesis and Biochemistry, Wiley-VCH, Weinheim, 1998.

When the azolide method is used, silanes are first formed in which sulfonic acid, phosphonic acid and / or carboxyl groups are directly linked to an aromatic ring, which is attached via a chain with, for example, a total of five (eg when using Sulfobenzoic acid and attachment to aminopropyltrimethoxysilane) or a total of six (eg, when using Sulfobenzoesäurε and attachment to Arninobutyltrirnethox- silane) chain atoms is bonded to the silane-Si atom. If a cross-linked proton-conductive polysiloxane is prepared starting from such a silane, one results in which individual or all sulfonic acid-phosphonic acid and / or carboxyl groups are each directly bonded to an aromatic ring, each directly via a chain with, for example, five or more six chain atoms is bonded to the respective Si atoms of the polysiloxane skeleton, wherein the chain between the aromatic ring and the respective Si atom (at least once) comprises the chain atom sequence CNC, in the form of the grouping C (O) -NH- C.

Alternatively, for example, the classical process of chlorosulfonation can be carried out to prepare silanes bearing sulfonic acid groups. In this case, an aromatic silane to be sulfonated is reacted with chlorosulfonic acid. A preferred embodiment of a chlorosulfonation process will be described in detail below.

As an alternative, an aromatic silane to be sulfonated can be reacted with chlorosulfonyl trimethylsilyl ester to prepare silanes carrying sulfonic acid groups (compare M. Schmidt, H. Schmidbaur, Concerning Chlorosulfuric Acid Silyl Esters, Chemische Berichte, 95, 1962, 47).

Both in the reaction with chlorosulfonic acid and in the reaction with trimethylsilyl chlorosulfonate, the formation of undesired by-products is observed starting from a silane with alkoxy- or Si-bonded phenyl groups. However, this problem can be avoided if chlorosilanes are used instead. These can be converted into the desired products with good yields. The following equation 3 shows this by the example of the reaction of phenylethyltrichlorosilane with trimethylsilyl chlorosulfonate. In this case, the trimethylsilyl ester-protected sulfonic acid group is first bound to the aromatic via an electrophilic substitution reaction. Subsequent reaction with sodium methoxide "deprotects" and converts the sulfonic acid group into its sodium salt Si-bonded chlorine atoms completely substituted by the likewise crosslinking active Methoxy- grαppen. Finally, the resulting reaction product can be used directly for production of melamine by means of condensation crosslinking, because under the (HCl) acidic conditions of crosslinking, the sulfonic acid is also liberated.

For the preparation of a nitrogen-containing aromatic heterocycle comprehensive silane in which the nitrogen-containing heterocycle is bound via an amide-functional organic spacer to the associated silane-Si atom, can - as studies have shown - also use the azolide method. In this case, an aminoalkyltrimethoxysilane is usually covalently linked to a carboxylic acid derivative of imidazole or benzimidazole. The following reaction equations 4 and 5 illustrate this type of reaction using the example of the amide formation of benzimidazole-5-carboxylic acid with aminopropyltrimethoxysilane. Here, in a first reaction step, the reactant benzimidazole-5-carboxylic acid with N, N'-carbonyldiimidazole to the reactive intermediate benzimidazole-5-carboxylic acid imidazolide reacted (equation 4). Subsequently, a nucleophilic substitution of the imidazolide group by the primary aminoalkyltrimethoxysilane leads to the silane-bound N-propyl-benzimidazole-5-carboxylic acid amide (Equation 5), which is obtainable in good yields.

Ben a mι dazol- 5-carbo ns e re Benzimldazole-5-cart »nsäJjre-lmιdazolιd

N- (3-trimethoxysilylpropyl) benzimidazole-5-carton) onsäureamιd

This variant of the azolide method leads to the synthesis of a silane with a nitrogen-containing heterocycle, which is bound to the associated silane-Si atom via an organic spacer comprising an amide function.

The synthesis routes explained above lead to precursors (organosilicon compounds which (a) carry sulfonic acid, phosphonic acid or carboxyl groups or (b) N-heteroaromatic groups) which, if appropriate, are processed in combination with further organosilicon compounds to produce polysiloxanes and membranes according to the invention be there and take over the proton-transmitting function completely or at least substantially.

It has already been stated above that a process for the preparation of a crosslinked proton-conducting polysiloxane comprises the hydrolysis and condensation of a mixture dissolved in a liquid comprising (i) a silane bearing a sulfonic acid, phosphonic acid or carboxyl group and (ii) a nitrogen-containing aromatic compound Heterocycle contains comprehensive silane. For the preparation of a membrane is usually a z. B. ethanolic solution of a combination of said silanes (i) and (ii), cross-linking (SiX ₄ ) and flexibilizing silane components (R ₂ SiX ₂ ) with water and a few drops of HCl and the resulting solution for several hours at room temperature touched. The onset of hydrolysis / condensation of the silanes leads to a pre-crosslinking of the components, which slowly increase the viscosity of the solution. Depending on the particular mixture composition, the precrosslinked solution is poured at a certain point in time into a thin layer of defined thickness, thus obtaining a virtually completely crosslinked membrane film within a short time.

Particularly temperature stable membranes of cross-linked protonenleitfähigem polysiloxane can be obtained by the membrane following an at 20 - 3O ⁰ C extending crosslinking a supplementary heat treatment (preferably under inert gas conditions) subjected at temperatures in the range of 140 - set 200 ° C become. The degree of crosslinking is optimized by the temperature post-treatment, and particularly important membrane properties such as tear resistance and chemical resistance can be further improved in individual cases. On a case-by-case basis, the person skilled in the art will determine, on the basis of a few preliminary experiments, how to set the individual process parameters in order to obtain a membrane which optimally corresponds to the requirements of the individual case.

The following formula I illustrates the structural motif of these membranes by way of example. Shown is a polysiloxane skeleton comprising sulfonic acid groups which are bonded via an organic spacer to respective Si atoms of the polysiloxane skeleton and in the ring nitrogen-containing aromatic heterocycles, which via an amide function comprehensive organic spacer to respective Si atoms of the Polysiloxane backbone are bound. Of course, the sequence of functional groups and the particular choice of functional groups is merely exemplary.

Formula I

On an industrial scale, the production of these membranes is preferably carried out by means of extrusion or tape casting in an automatic plant.

In some cases, it may be useful to provide a free radical crosslinking reaction in a process for preparing a crosslinked proton conductive polysiloxane or a proton conductive membrane in addition to the described hydrolysis / condensation. In particular, it is possible to use vinyl- and methyl-substituted silane compounds which crosslink radically in the presence of 2,4-dibenzoyl peroxide. The vinyl- or methyl-substituted silane compounds may of course also carry sulfonic acid-phosphonic acid and / or carboxyl groups or N-heteroaromatic groups. In particular, it is possible to use as vinyl- or methyl-substituted components: methyl-substituted phenylsilanes such as diphenylmethylsilane or phenyltrimethylsilane (for the sulfonation reaction) and vinyltrialkoxysilanes or vinyl-terminated copolymers as additional crosslinking components. After addition of 2,4-dibenzoyl peroxide and heating the reaction mixture to 140 ° C, the radical crosslinking reaction proceeds, preferably in parallel to the condensation reaction. Further information, techniques and processes relating to the above-described crosslinked proton-conducting polysiloxanes are disclosed in German patent application 102004023586.4 and in the international application PCT / EP2005 / 052165, which claims priority to this application. The content of these applications is incorporated by reference into the present application.

According to another preferred embodiment of the present invention, the at least one polysiloxane in the catalytically active composition may be the above-disclosed crosslinked proton-conductive polysiloxane.

The present invention further relates to an MEA which contains at least one layer with / from a proton-conductive material and at least one layer with / from the catalytically active composition according to the invention. The layer with / from the catalytically active composition according to the invention can be present on the cathode side, on the anode side or on both sides of the layer with / of a proton-conductive material.

The MEAs produced from the above-described catalytic compositions according to the invention in combination with electrically and proton-conductive components can have any suitable structure.

For example, the MEA may comprise a layer with / of a proton-conductive material adjacent to at least one layer with / of a catalytically active composition according to the invention that is not electrically conductive and not proton-conductive or non-electrically conductive but proton-conductive, and adjacent thereto at least one layer with / from a catalytically active composition according to the invention, which is both electrically conductive and proton conductive.

Another example of an MEA falling within the scope of the present invention includes a layer of proton conductive material adjacent at least one thereof Layer with / from a catalytically active composition according to the invention, which he * where HI plf »lrtricr * H 1. = _* itfciHi rr QI C nrntπnpnl Ait" fciHi fτ ϊ ct

The numerous other possible embodiments of the MEA according to the invention also include such an example in which, adjacent to a layer with / of a proton conductive material, a layer with / from a catalytically active, non-electrically conductive composition according to the invention follows, on which an electrically conductive Layer of a suitable material is present.

Of course, the MEA according to the invention may also contain a catalytically active layer, in addition to the catalytically active composition according to the invention also conventional electro-catalytically active materials are included, such as the above-mentioned graphite-supported platinum-containing materials. The same applies to the proton-conductive components optionally contained in the catalytically active layer of an MEA.

In the case of the MEAs according to the invention, the layers with / of the catalytically active composition according to the invention and / or the electrically conductive layer can be used in a thickness in the range from nanometers to micrometers.

In the MEA, the proton conductive material is preferably selected from the group consisting of at least one crosslinked proton conductive polysiloxane as defined in claims 12 to 22, a perfluorinated hydrocarbon backbone with sulfonated alkyl ether side groups (e.g., Nafion), polybenzimidazole, or a mixture thereof.

The catalytically active composition according to the invention has the advantage in such an MEA that penetration of the catalytically active composition and the layer with / out of the proton-conductive material into the area of facing surfaces of the layer (s) with / from the catalytically active composition and / or penetration of the catalytically active composition and / or or the catalytically active composition and the proton conductive material is given. The catalytically active composition according to the invention thus makes it possible to produce a homogeneous transfer phase between the catalyst layer and the electrolyte material. As already mentioned above, such a homogeneous transition phase is necessary in order to transfer the ions (protons or anions) formed in the electrocatalyst layer as quickly and efficiently as possible into the polymer electrolyte membrane.

In addition, the inventors have found that when the MEA of the present invention is formed such that the proton-conductive layer contains at least one siloxane component, not only the above-described penetration of the catalytically active composition and the proton conductive layer when applying the layer of a catalytically active composition of the present invention Material forms, but also in the region facing each other surfaces of the layer (s) with / from the catalytically active composition and the layer with / from the proton conductive material, a covalent linkage of siloxane components of the catalytically active composition and / or siloxane components of the catalytically active composition is given with siloxane components of the proton conductive material.

This covalent linkage is the result of condensation, hydrosilylation (addition reaction), or radical bond formation. These crosslinking reactions can be used singly or in combination.

Due to the similarity in substance, which is given in particular when a catalytically active composition according to the invention is used or contained in an electrocatalyst, and used as proton-conductive layer, a crosslinked proton-conductive polysiloxane according to any one of claims 12 to 22 or in the proton conductive layer is contained in the membrane-electrolyte membrane by the covalent linkage a more intimate and homogeneous penetration of the electro-catalyst with the proton-conducting membrane than previously possible. This results in a significantly improved transition phase between electrocatalyst and proton-conductive layer, which leads to an optimized proton transfer from the electrocatalyst to the proton-conducting membrane.

Substantially similar in this context means that the materials are based on functionalized organosilicon compounds and crosslinked polysiloxanes.

This transition phase between the two components is still regarded as problematical in the previous membrane electrode assemblies (MEAs), since high contact resistances and inhibited proton transfer still occur in the electrocatalyst systems hitherto used. These disadvantages are overcome by the MEA according to the invention.

The catalytically active composition according to the invention makes it possible to produce MEAs which, in addition to those of the prior art, have a whole series of further advantages in addition to the advantages already described above:

- Due to the high catalytic activity, the content of expensive precious metals can be reduced compared to conventional electrocatalyst layers according to current knowledge in any case by 50% and more, which allows a significant cost savings;

- The catalytically active composition according to the invention has an excellent temperature stability, so that the operating temperature can be increased in the fuel cell, which increases the speed of the reactions occurring in the fuel cell reactions. At the same time, at elevated operating temperatures above about 125 ° C, the CO / CO ₂ equilibrium shifts more in favor of CO ₂ , reducing the risk of CO poisoning of the electrocatalyst.

the composition according to the invention can be applied and used in nanometer-thick layers. This not only leads to a higher dispersion speed but, due to the material savings, to a further reduction of the costs in the production of the MEAs. Furthermore, the inventors have found that the catalytically active composition according to the invention can be applied very well to very thin layers even on conventional proton-capable materials, such as Nafion or polybenzimidazole. This suggests that even with these proton-conductive materials an improved transition phase between the catalytically active composition as / in the electrocatalyst and the proton-conductive layer is formed.

However, the catalytically active composition according to the invention is not only suitable as an electrocatalyst for an MEA or as a constituent of such an electrocatalyst. As the inventors have found and have already been mentioned above, the composition is also particularly suitable for catalysis in carrying out reactions of organic and / or inorganic compounds. In this case, the catalytically active composition itself can be used as a catalyst or form part of the catalyst used.

In such a catalyst, the catalytically active layer may advantageously be formed as a thin layer, preferably as a nanolayer, on a carrier material. As a carrier material both polymeric materials and inorganic materials, such as (porous) ceramic materials may be used. The carrier may, for example, have the form of flat modules, tube modules, bulk material and / or foam material. Thus, highly porous, catalytically active and optionally electrically conductive supports can be produced, which can be used, for example, in depth filtration technology.

The catalyst according to the invention can also be in any suitable form, for example in the form of a conventional catalyst bed, as a self-supporting film, as a membrane membrane supporting structures or with a sheet-like, particulate and / or (micro) tubular substrate. Such catalysts can be used, for example, in the form of tube reactors or flat-structured membrane reactors for chemical reaction technology. In the case of catalyst beds, the catalysts produced can be brought to the grain size required for the application, for example by mechanical treatment and subsequent sieving.

As stated above, the catalytically active composition according to the invention consists of at least one polysiloxane with metal ions and / or metal atoms. As such, this composition is already useful as a catalyst. According to a first preferred embodiment of the catalytic composition according to the invention, the metal ions and / or metal atoms are complexed to the polysiloxane.

As the inventors have further discovered, the catalytic composition of the present invention retains catalytic properties even when this composition or a catalyst formed therewith is heated to a temperature at which the complex-like bonds begin to decompose, typically starting at about 250 ° C the case is. This catalytic property makes this material ideally suited for use as membrane reactors in different modular form (e.g., tube bundle reactors) for chemical reaction engineering processes. If, for example, one coating ceramic modules with a sol-gel layer and these with the catalytically active composition according to the invention, a porosity which is graduated over a wide range and the resulting separation selectivity can be achieved by the resulting layers.

When the inventive catalytically active composition or a catalyst formed using this composition, for example in the form of a nano-layer of the catalytically active composition on a ceramic support material, heated to a temperature between about 100 ° C and 650 ⁰ C, which is preferably under an atmosphere of a shielding gas or hydrogen gas, and then examining the state of the surface, it is found that the metal ions or metal atoms originally present are still either as metal complexes, single atoms / ions or as the tiniest metal clusters with a diameter of <3 nm present in highly dispersed form. As a rule, the metal clusters form when the catalytically active composition is treated at a temperature above about 400.degree.

The inventors explain this observation with the fact that the metal ions and / or metal atoms originally present in the polysiloxane are virtually fixed by the framework of polysiloxane surrounding them. When heated above a temperature at which the complex-like bonds begin to decompose, however, the metal ions and / or metal atoms are prevented by the surrounding framework from joining together to form larger groups. In this way it is achieved in a highly advantageous manner that a highly dispersed distribution and also a high catalytic activity are maintained even at higher temperatures.

The process according to the invention for the preparation of a catalytically active composition according to any one of claims 1 to 23 comprises the steps: a) dissolving at least one organosilicon compound in an organic solvent; b) dissolving at least one metal compound, preferably a halogenated metal compound, in an organic solvent which is miscible with the organic solvent used in step a); c) mixing the solution obtained in step a) with the solution obtained in step b); d) reacting the at least one organosilicon compound and the at least one metal compound; e) removing the solvent (s) after completion of the reaction;

This process can be modified by adding, after step d) of the solution, a component A and / or a component B and / or a flexibilizing and / or network-modifying polymer. The component A can be added, for example, in the form of a disperse suspension of an electrically conductive solid, such as polyaniline or nano-graphite powder or metals, by mixing with the above solutions. A further variation of the process according to the invention provides that in step e) the solution is applied as a thin liquid film and the solvent (s) can be evaporated off at room temperature. This variation can be used simultaneously to apply the catalytically active composition according to the invention to a carrier material. Since, as described above, the catalytically active composition is dissolved in a solvent, only very small amounts of catalytically active composition per unit area can be applied by appropriate adjustment of the degree of dilution during application of the liquid film. Consequently, after evaporation of the solvent, only a very thin layer of the catalytically active composition remains on the carrier material. The thickness of this layer is practically arbitrarily adjustable and it is in any case possible to produce layers with a thickness from the nanometer range to the lower micron range. In any case, however, a high dispersion of the active metal and the formation of highly active layers are achieved.

In the method according to the invention preferably organic solvents are used which is / are selected from the group consisting of aliphatic alcohols, aromatic alcohols, which may be monovalent or polyvalent, and chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, acetonitrile or toluene , as well as mixtures thereof.

Preferred examples of the alcohols are methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, decanol, glycerol, cyclohexanol, and all isomers of the latter eight and phenol.

Further, after evaporation of the solvent (s), the composition may be subjected to reactive post-crosslinking / polymer pyrolysis or thermal treatment under inert gas or hydrogen gas. The method according to the invention for producing an MEA comprises the steps of applying at least one layer with / of a catalytically active composition according to one of claims 1 to 23 to at least one layer with / of a proton-conductive material. As mentioned above, since the layer with / of a catalytically active composition can be used on both the cathode and anode sides of an MEA, application of the layer to either or both sides of a layer may occur proton-conductive material.

The application of the at least one layer with / from the catalytically active composition on the at least one layer with / from a proton-conductive material can preferably be effected by means of spin coating, pressing, hot pressing or reactive coating.

The catalytically active composition according to any one of claims 1 to 23 and the MEA according to any one of claims 24 to 29 is preferably used in a polymer electrolyte membrane fuel cell or a high-temperature polymer electrolyte membrane fuel cell, wherein the respective fuel cell operating temperatures may be between about -20 ⁰ C and about 250 ° C.

The catalytically active composition according to any one of claims 1 to 23 and the catalyst according to any one of claims 30 to 36 can be used preferably for the synthesis of organic compounds, for example in membrane reactors via hydrogenation reactions of unsaturated hydrocarbons, and for the catalytic purification of exhaust gases. When used for the catalytic purification of exhaust gases, the catalytically active compositions can be applied, for example, as thin functional layers on ceramic monoliths.

In the following, the present invention will be further explained by some examples, the content of which, however, should not be interpreted as limiting the scope of the present invention. Example 1: Production of a Membrane-Electrode Unit

0.14 g (0.00027 mol) of hexachloroplatinic acid are dissolved in 6 g (0.13 mol) of ethanol. 0.77 g (0.0034 mol) of aminopropyltriethoxysilane are also dissolved in 6 g of ethanol. Subsequently, the mixtures are stirred for 24 h. After the end of the 24 h, the solution containing hexachloroplatinic acid is successively added to the aminosilane solution with stirring at room temperature, care being taken to dissolve the added fraction in each case. The successive addition ensures the homogeneous distribution of the substances and the optimal incorporation of the metal.

It is also possible initially to introduce the aminosilane in solution and to add the hexachloroplatinic acid which is likewise in solution.

After addition, the solution is allowed to react for 12 to 24 hours with stirring at room temperature.

The solution undergoes a color change from initially orange to milky yellow, cloudy and pale yellow, clearly after complete implementation.

There is now the admixture of the electrically conductive component such as polyaniline, wherein its homogeneous incorporation is improved by a previously performed sulfonation reaction.

Subsequently, the polysiloxane provided with proton-conducting functions is admixed and the solution thus prepared is applied as a liquid film to a proton-conducting membrane on both sides.

The MEA prepared in this way is subjected to a temperature treatment in a hydrogen atmosphere and then boiled for 1 hour in 5% sulfuric acid and then aged for a further hour in distilled water. Example 2: Preparation of a catalytically active film

0.14 g (0.00027 mol) of hexachloroplatinic acid are dissolved in 3 g (0.065 mol) of ethanol. Subsequently, while stirring at room temperature, the primary aminosilane (0.77 g, 0.0034 mol), e.g. Aminopropyltriethoxysilane added, care being taken to dissolve each of the added portion.

To this approach are added, with stirring at room temperature, 0.25 g of a phenyl-containing and crosslinkable organosilicon compound, e.g. Diphenyldimethoxysilane (0.0010 mol), 0.10 g of a crosslinkable organosilicon copolymer such as diphenyldimethylsiloxane-SiOH terminated, and 0.10 g, 0.00048 mol of a tetrafunctional crosslinker such as tetraethoxysilane were added.

The mixture is stirred for at least 12 h at room temperature and then poured out on a Teflon pad. The sample thus remains at room temperature to ensure the successive evaporation of the solvent and the pre-crosslinking to the film. This pre-crosslinking can be accelerated by a moderate temperature treatment at low temperatures in the furnace, if necessary.

Post-crosslinking of the film is then carried out under inert gas (N ₂ , Ar) and / or a reduction in hydrogen flow up to 200 ° C. If necessary, the post-crosslinking can also be carried out under an oxidative atmosphere.

As already mentioned above, the network structure can be further modified by combination with bifunctional, trifunctional and / or tetrafunctional silanes, as well as co-polymers. Example 3: Coating of carrier systems with the catalytically active composition

0.14 g (0.00027 mol) of hexachloroplatinic acid are dissolved in 6 g (0.13 mol) of ethanol. 0.77 g (0.0034 mol) of aminopropyltriethoxysilane are also dissolved in 6 g of ethanol. Subsequently, the mixtures are stirred for 24 h. After the end of the 24 h, the solution containing hexachloroplatinic acid is successively added to the aminosilane solution with stirring at room temperature, care being taken to dissolve the added fraction in each case.

This mixture is applied for example by means of dip coating on a ceramic support, preferably of Al ₂ O ₃ or SiO ₂ . Subsequently, the carriers coated in this way are aged for 24 h at 60% air humidity.

The reduction of the material is carried out under hydrogen flow in a tube furnace at temperatures between 250 to 65O ⁰ C.

Example 4: Preparation of catalytically active beds

0.14 g (0.00027 mol) of hexachloroplatinic acid are dissolved in 3 g (0.013 mol) of ethanol. Subsequently, while stirring at room temperature, the primary aminosilane (0.77 g, 0.0034 mol), e.g. Aminopropyltriethoxysilane added, care being taken to dissolve each of the added portion.

This mixture is poured out on a Teflon pad and crosslinked at room temperature. Subsequently, this material is crushed and subjected in the hydrogen stream to a temperature of 250 to 650 ° C.

Desired particle sizes can be adjusted by pressing and sieving the material. Again, the mixture can be supplemented as needed with other silane components and the metal can be substituted accordingly. The catalytically active composition of the present invention fulfills the technical requirement profile of a polymer electrolyte electrolyte fuel cell (PEMFC) as electrocatalyst material and is also suitable for applications in a high-temperature polymer electrolyte membrane fuel cell (US Pat. High Temperature Polymer Electrolyte Membrane Fuel Cell, HT-PEMFC) with operating temperatures up to at least 200 ° C and beyond. Furthermore, the catalytically active composition shows high long-term stability. The composition is catalytically active, optionally electrically conductive and proton conductive, in order to decompose the hydrogen entering there into protons and electrons and to transfer these species when used in an / as an electrocatalyst on the anode side of the membrane-electrode assembly. Moreover, the catalytically active composition of the present invention is equally suited to be used in an electrocatalyst on the cathode side of a membrane-electrode assembly to decompose, for example, incoming oxygen and transfer the resulting species.

The catalytically active composition according to the invention improves the still problematic transition phase between the electrocatalyst and the proton-conducting membrane and thereby ensures, in particular, optimized proton transfer from the electrocatalyst into the membrane. The novel E-Kat mixtures can be prepared, for example, as thin functional layers, e.g. be applied by spin coating on the crosslinked proton-conducting polysiloxanes according to claims 12 to 22, but also be applied to already commercially available polymer electrolyte membranes such as Nafion or polybenzimidazole. The former leads due to the chemically related material systems - both systems are organosilicon derived and lead to a polysiloxane matrix - to a particularly intimate penetration of the electrocatalyst with the proton-conducting membrane.

The catalytically active composition can be used in membrane reactors for the synthesis of organic compounds e.g. be used via hydrogenation reactions of unsaturated hydrocarbons. In this case, the polysiloxanes with metal ions and / or metal atoms can be used mainly.

Claims

claims

1. Catalytically active composition containing at least one polysiloxane with metal ions and / or metal atoms.

2. A catalytically active composition according to claim 1, wherein at least a portion of the metal ions and / or metal atoms is complexed to the polysiloxane.

3. Catalytically active composition according to claim 1 or 2, wherein the at least one polysiloxane is obtained from at least one organosilicon

A compound containing at least one heteroatom-containing functional group selected from the group consisting of amino, amido, carboxyl, sulfonic acid, thio or cyano, or a mixture thereof.

4. The catalytically active composition of claim 3, wherein the organosilicon compound is selected from the group consisting of aminopropyltriethoxysilane, aminobutyltriethoxysilane, aminophenoxypropyltrimethoxysilane, aminophenyltrimethoxysilane, aminopropylmethyldiethoxysilane, aminoethylaminopropylmethyldimethoxysilane, trimethoxysilylpropylbenzimidazole-5-amide, trimethoxysilylpropylimidazole 2-amide, trimethoxysilylphenylsulfonic acid, and trimethoxysilylethylphenylsulfonic acid, or a mixture thereof.

5. A catalytically active composition according to any one of claims 1 to 4, wherein the present in / on the polysiloxane and / or complex-like bound metal ions and / or metal atoms are selected from the group consisting of

Platinum, palladium, nickel, ruthenium, iron, copper, zinc, rhenium, rhodium, iridium, osmium, selenium, titanium, vanadium, chromium, manganese, cobalt, zirconium, molybdenum, cadmium, gold, silver, or a mixture thereof.

6. Catalytically active composition according to one of claims 1 to 5, comprising at least one component A, which confers electrical conductivity to the composition.

7. The catalytically active composition of claim 6, wherein component A is selected from the group consisting of electrically conductive carbon components, preferably conductive carbon black or graphite, metal or a conductive polymer, preferably polyaniline, polythiophene or polypyrazole, wherein the conductive polymers optionally sulfonated, phosphonated, carboxylated and / or doped with at least one of the metals according to claim 5, or a mixture thereof.

8. Catalytically active composition according to one of the preceding claims, comprising at least one flexibilizing and / or network-modifying polymer.

9. The catalytically active composition according to claim 8, wherein the at least one flexibilizing and / or modifying agent modifying a organosilicon derived block copolymer, preferably polydimethylsiloxane, diphenylsiloxane dimethylsiloxane SiOH-terminated, diphenylsiloxane dimethylsiloxan-vinyl-terminated, is the phenyl-bearing polymers may optionally be sulfonated.

10. A catalytically active composition according to any one of claims 1 to 9, comprising at least one component B which imparts proton conductivity to the composition.

1 1. A catalytically active composition according to claim 10, wherein the component B is selected from the group consisting of at least one proton conductive crosslinked polysiloxane, a perfluorinated hydrocarbon backbone with sulfonated Alkyletherseitengruppen, polybenzimidazole, or a mixture thereof.

12. A catalytically active composition according to claim 11, wherein the proton-conductive, crosslinked polysiloxane is a preferably polysiloxane having a polysiloxane backbone and having heteroatom-containing functional groups in the side chain, comprising - aeide groups, preferably sulfonic acid, phosphonic acid and / or carboxyl -

Groups which are each bound via an organic spacer to jeweiligε Si atoms of the polysiloxane backbone, and either (a) in the ring nitrogen-containing aromatic heterocycles, each having an amide containing an organic spacer to respective Si atoms of the

Polysiloxane skeleton are bound or (b) in the ring nitrogen-containing aromatic heterocycles, which are each bound via an organic spacer to respective Si atoms of the polysiloxane backbone.

13. The catalytically active composition according to claim 12, wherein the proton-conductive, crosslinked polysiloxane comprises nitrogen-containing aromatic heterocycles in the ring, which are each bonded to respective Si atoms of the polysiloxane backbone via an organic spacer comprising an amide function.

14. A catalytically active composition according to any one of claims 12 or 13, wherein in the proton conductive crosslinked polysiloxane individual or all in the ring nitrogen-containing aromatic heterocycles are selected from the

Group consisting of optionally substituted benzimidazole and optionally substituted imidazole.

15. A catalytically active composition according to any one of claims 12 to 14, wherein in the proton-conductive crosslinked polysiloxane einεlne or all in

Ring of nitrogen-containing aromatic heterocycles in each case via an amide functional organic spacer having 5-10 chain atoms, preferably 5-8 bonded to respective Si atoms of the polysiloxane backbone and the respective amide function is directly covalently bonded to the associated heterocycle.

16. A catalytically active composition according to any one of claims 12 to 15, wherein in the proton conductive crosslinked polysiloxane individual or all in the ring nitrogen-containing aromatic heterocycles to respective Si atoms of the polysiloxane backbone according to the formula Het-C (O) -N (R ³ ) -R ⁴ -Si ^* are attached, wherein Het, R ³ is hydrogen or an aliphatic or aromatic organic radical, R ⁴ is an aliphatic chain and a Si-Si atom of the polysiloxane backbone, the nitrogen-containing aromatic ring in the heterocycle.

17. A catalytically active composition according to any one of claims 12 to 16, wherein in the proton conductive, crosslinked polysiloxane individual or all sulfonic acid, phosphonic acid and / or carboxyl groups are each directly connected to an aromatic ring, each directly via a Chain with 1, 2, 3, 4, 5 or 6 chain atoms bonded to respective Si atoms of the polysiloxane backbone.

18. A catalytically active composition according to claim 17, wherein in the proton-conductive, crosslinked polysiloxane the chain between the aromatic ring and the respective Si atom comprises 5 or 6 chain atoms and at least once the chain atom sequence C-N-C, preferably in the form of the group C (O) -

NH-C.

19. A catalytically active composition according to any one of claims 12 to 18, wherein in the proton conductive, crosslinked polysiloxane, the polysiloxane backbone by hydrolysis and condensation of (i) silanes with four, (ii) silanes with three and optionally additionally of (iii) silanes with two hydrolyzable

Grunnen has manufacturable network structure.

20. The catalytically active composition of claim 19, wherein the proton-conductive, crosslinked polysiloxane is the crosslinked polysiloxane

Atomic groupings of the type -O-Si (phenyl) ₂ -O- and / or -O-Si (CH ₃ ) ₂ -O-.

21. A catalytically active composition according to any one of claims 12 to 20, wherein in the proton conductive, crosslinked polysiloxane, the ratio of (i) in the ring nitrogen-containing aromatic heterocycles to (ii) the sulfonic acid, phosphonic acid and / or carboxyl groups in the range from 3: 1 to 1: 2, preferably in the range of 3: 1 to 1: 1.

22. A catalytically active composition according to any one of claims 12 to 21, wherein in the proton-conductive, crosslinked polysiloxane in the crosslinked polysiloxane imidazole is incorporated.

23. A catalytically active composition according to any one of claims 1 to 9, wherein the at least one polysiloxane is a proton-conductive, crosslinked polysiloxane according to any one of claims 12 to 22.

24. Membrane electrode unit comprising at least one layer with / from a proton-conductive material and at least one layer with / from a catalytically active composition according to one of claims 1 to 23.

25 membrane electrode assembly according to claim 24 with a layer with / from a proton-conductive material adjacent to at least one layer with / from a catalytically active composition according to any one of claims 1 to 5 or at least one layer with / from a non-electrically conductive catalytic

Composition according to one of claims 8 to 23, and adjoining thereto at least at least one layer with / from a catalytically active composition according to one of claims 10 to 23.

26. Membrane-electrode assembly according to claim 24 having a layer with / from a proton-conductive material and adjacent thereto at least one layer with / from a catalytically active composition according to any one of claims 10 to 23.

27. The membrane electrode assembly of claim 24, wherein the proton conductive material is selected from the group consisting of at least one proton conductive, crosslinked polysiloxane as defined in claims 12 to 22, a perfluorinated hydrocarbon backbone with sulfonated ones Alkyl ether side groups, polybenzimidazole, or a mixture thereof.

28. membrane electrode assembly according to any one of claims 24 to 27, wherein in the region of mutually facing surfaces of the layer (s) with / from the catalytically active composition and the layer with / from the proton conductive material, a penetration of the catalytically active composition and / or the catalytically active composition and the proton conductive material.

29. membrane electrode assembly according to any one of claims 24 to 28, wherein in the region facing each other surfaces of the layer (s) with / from the catalytically active composition and the layer with / from the proton conductive material, a covalent linkage of siloxane components of the catalytically active Composition and / or siloxane components of the catalytically active composition is given with siloxane components of the proton conductive material.

30. Catalyst for carrying out reactions of organic and / or inorganic compounds comprising a catalytically active composition according to one of claims 1 to 23 or consisting thereof.

31. Catalyst according to claim 30, containing a catalytically active composition according to one of claims 1 to 23, wherein the composition is formed as a thin layer, preferably as a nano-layer, on a carrier material, wherein optionally between the carrier material and the layer one or more layers other materials, preferably one or more sol-gel layers, may be present.

32. A catalyst according to claim 31, wherein the carrier material is a polymeric material, an inorganic material, preferably (porous) ceramic materials, in the form of flat modules, tube modules, bulk material and / or foam material.

33. A catalyst according to any one of claims 30 to 32 in the form of a conventional catalyst bed, self-supporting film, support membrane membrane, having a flat, particulate and / or tubular support material.

34. A catalyst obtainable by heating a catalytically active composition according to any one of claims 1 to 23 or a catalyst according to any one of claims 30 to 33 to a temperature between about 100 ° C and 650 ° C.

35. A catalyst according to claim 34, wherein the heating takes place under an atmosphere of an inert gas or hydrogen gas.

36. A catalyst according to claim 34 or 35, characterized in that the catalyst contains metal atoms, metal ions and / or metal clusters with a diameter of <3 nm in highly dispersed form.

37. A process for preparing a catalytically active composition according to any one of claims 1 to 23, comprising the steps: a) dissolving at least one organosilicon compound in an organic

Solvent; b) dissolving at least one metal compound, preferably a halogenated one

Metal compound, in an organic solvent which is miscible with the organic solvent used in step a); c) mixing the solution obtained in step a) with that obtained in step b)

Solution; d) reacting the at least one organosilicon compound and the at least one metal compound; e) removing the solvent (s) after completion of the reaction;

38. The method of claim 37, wherein after step d) of the solution, a component A and / or a component B and / or a flexibilizing and / or network-modifying polymer is / are added.

39. The method according to any one of claims 37 or 38, wherein in step e), the solution is applied as a thin liquid film and allowed to evaporate the solvent (s) at room temperature.

40. The method according to any one of claims 37 to 39, wherein the / the organic solvent (s) is / are selected from the group consisting of aliphatic alcohols, aromatic alcohols, which may be monovalent or polyvalent nen, and chloroform, tetrahydrofuran , Dimethylformamide, dimethyl sulphoxide,

Acetonitrile or toluene, as well as mixtures thereof.

41. The method according to any one of claims 37 to 40, wherein after evaporation of the / the solvent (s), the composition of a reactive post-crosslinking / polymer pyrolysis or a temperature treatment under inert gas or

Hydrogen gas is subjected.

42. A method of making a membrane-electrode assembly comprising the steps of:

Application of at least one layer with / of a catalytically active composition according to one of claims 1 to 23 to at least one layer with / of a proton-conductive material.

43. The method of claim 42, wherein applying the at least one layer with / from the catalytically active composition on the at least one layer with / from a proton-conductive material by means of spin-coating, pressing,

Hot pressing or reactive coating takes place.

44. Use of the catalytically active composition according to any one of claims 1 to 23 and the membrane-electrode assembly according to any one of claims 24 to 29 in a polymer electrolyte membrane fuel cell or a high-temperature polymer electrolyte membrane fuel cell.

45. Use according to claim 44, wherein the respective fuel cell operating temperatures between about -20 ⁰ C and about 25O ⁰ C.

46. Use of the catalytically active composition according to one of the claims

1 to 23 and the catalyst according to any one of claims 30 to 36 for the synthesis of organic compounds and for the catalytic purification of exhaust gases.