DE102007000646B4 - Process for producing a membrane-electrode assembly - Google Patents

Abstract

Method for producing a membrane for a membrane-electrode assembly, comprising the following steps: - Providing a structured porous substrate (100), the substrate (100) being formed by an electrically insulating material, the substrate (100) having a first side (102) and a second side (104) opposite the first side, the substrate (100) having a plurality of through holes (110), each of the through holes (110) directly connecting the first and second sides (104) connects, - applying an electrically conductive layer to the first and second sides (104) of the substrate (100), the electronically conductive layer (106) mechanically stabilizing the membrane, - applying catalyst particles (112) to the first side ( 102) and the second side (104) of the substrate (100), - electrically burning off the conductive layer in the through holes (110).

Description

The invention relates to a method for producing a membrane-electrode assembly.

Fuel cells are considered to be the energy suppliers of the future as they enable decentralized power generation without local emissions of pollutants or greenhouse gases.

A fuel cell converts chemical energy contained in a fuel (eg, hydrogen, natural gas, methanol) directly into electricity and heat. Due to their high efficiency, the use of fuel cells in various application areas is being considered. In addition to use in vehicles, in portable devices to replace batteries and accumulators, as well as in space technology, it is even conceivable that fuel cells from renewable energy sources in anodic alumina (AAO) membrane.

In general, a fuel cell consists of two porous gas-permeable electrodes (anode, cathode), which are separated by an ion conductor. The anode is supplied with a high-energy fuel, such as. As hydrogen, methane, methanol or a glucose solution. The fuel is oxidized there to form protons (H ⁺ ) as positive charge carriers. The cathode, however, is bathed with an oxidizing agent, usually R. (air) oxygen, wherein the oxidizing agent is reduced there to O ^2- ions. Since, during the oxidation, a discharge of electrons takes place, whereas electrons are taken up during the reduction, a load connected between the anode and the cathode can be operated. To ensure efficient conversion of fuel and oxidant, typically the electrodes are coated with catalysts. The catalyst material used in this case are generally the platinum metals (platinum, palladium, ruthenium) and their alloys, since they lie with their average adsorption enthalpies in the maximum of the so-called volcano curve and thus the best possible compromise between strong adsorption of the gas molecules and weakest possible adsorption represent the intermediates.

Basically, the electrodes must combine different properties. This includes on the one hand the effective supply and discharge of the electric current, the use as a carrier and electrical contact for the catalyst and the formation of a porous gas distribution layer. These gas diffusion electrodes (GDE) must continue to have a low contact resistance to the proton-conducting medium.

As ion-conducting separators different materials are used. These include depending on the fuel cell type z. As concentrated acids, alkalis, acidic polymer membranes, carbonate melts or solid-state ionic conductors. Another essential property of these membranes is their (as low as possible) permeability of the fuel H ₂ , methanol, etc., in order to avoid losses due to mixed potential formation.

Although intensive progress has been made in recent years in the development of fuel cells - in particular Proton Exchange Fuel Cells (PEFC) - there is still considerable room for improvement in such fuel cells. However, new materials, designs and manufacturing techniques are needed to achieve this goal.

To improve fuel cells, there are now three important starting points. A first starting point is the improvement of the catalyst efficiency, another starting point is the reduction of ohmic losses, in particular by the proton-conducting membrane. The third starting point is the reduction of the diffusion-controlled mass transport restriction. With conventional techniques, it is very difficult to substantially reduce ohmic losses, since, for. For example, proton transport can not be accelerated beyond the Grotthuss limit of motion. Furthermore, conventional polymer membranes having a thickness of less than 20 μm are difficult to realize since such thin materials are not mechanically stable. For this reason, a reduction in ohmic losses to improve fuel cells is accompanied by the need for stabilization of extremely thin and mechanically unstable ionomer membranes. As far as the mass transport restriction is concerned, the (Nernst) diffusion and flooding of the pores of the gas diffusion layer with water must be kept as low as possible. These boundary conditions require on the one hand extremely thin membrane with a thickness substantially thinner than 10 microns. On the other hand, controlling the hydrophobicity of the interfaces / surfaces in contact with wetted fuel such as hydrogen and oxygen is required. This applies to both the pores of the gas diffusion layer and the gas distribution structure.

In summary, the requirements for new types of electrode-membrane units for fuel cells are high electrical conductivity of the electrodes, a large contact surface with the electrolytes, good gas transport properties, good ion transport properties, good catalytic properties, and high chemical and mechanical stability with the lowest possible volume and material usage.

In order to meet these requirements, various types of fuel cell or fuel cell membranes have been developed. For example, the WO 2004/109837 A2 Electrodes for a polymer electrolyte membrane and direct methanol fuel cells, the electrodes comprising carbon nanotubes and a catalytically active metal.

The WO 2004/109837 A2 generally describes a proton electrolyte membrane fuel cell electrode comprising carbon nanotrains and a catalyst metal.

The DE 103 40 929 A1 discloses a proton-conducting polymer membrane containing polymers comprising at least one porous support material and polymers comprising phosphoric acid groups, obtainable by polymerization of monomers comprising phosphoric acid groups.

E. Peled, T. Duvdevani, A. Melman, Elektrochem. Solid State Lett. 1998, 1, 210 discloses a novel proton-conducting membrane. This novel proton-conducting membrane consists of an electrically non-conductive ceramic powder, which is formed by nanoparticles.

The EP 1 635 413 A1 discloses a proton conductive film wherein the proton conductive film comprises particles wherein gaps between the particles extend from the surface of the film to the opposite surface side of the film to thereby form a proton conductive channel.

The DE 20 2005 017 573 U1 discloses a membrane structure for the deposition of hydrogen or oxygen with a non-porous polymer membrane and with a cover layer of noble metal or noble metal alloy.

The EP 1 391 235 A2 discloses an AAO membrane with electrodes made of a carbon material. The WO 2004/109837 A2 discloses electrodes for fuel cells, wherein the electrodes may contain material in the form of carbon nanotubes.

The invention is based on the object to provide an improved method for producing a membrane for a membrane-electrode assembly.

The problem underlying the invention is achieved with the feature of the independent claim. Preferred embodiments of the invention are indicated in the dependent claims.

According to the invention, a membrane for a membrane-electrode assembly is produced, wherein the membrane has a structured porous substrate, wherein the substrate is formed by an electrically insulating material. Furthermore, the substrate has a first side and a second side opposite the first side, the first side and the second side having an electronically conductive layer, wherein these conductive layers comprise catalyst particles, wherein the electronically conductive layers mechanically stabilize the membrane. In addition, the substrate has a plurality of through holes, each of the through holes connecting the first and second sides directly to each other and having any desired z. B. proton-conducting medium can be filled.

By using the plurality of through-holes, each of the through-holes interconnecting the first and second sides directly, and preferably also in-line, an optimum system is provided to create the shortest path on the anode side Transport protons to the cathode side. This leads to a significant reduction of ohmic losses, especially at very low layer thicknesses in the nm to μm range. In addition, in the case of miniaturization, the through holes in the nanometer range can be achieved so that as far as possible any catalyst particles lying on the anode surface can interact with a catalyst particle located opposite to the cathode side. Thus, an optimal utilization of catalyst particles can be realized.

As is well known to those skilled in the art, therefore, the electrically insulating material from which the substrate is formed is necessary to provide only current flow when using the membrane in a fuel cell between the two conductive layers on the first side and the second side ,

According to one embodiment of the invention, the inner walls of the through-holes are covered only in the mouth region of the electronically conductive layer, and the conductive layer preferably extends into the through-holes from both sides of the substrate, but without touching in the through-holes. This locally reduces the layer thickness of the proton conductor and enables an improved formation of the three-phase boundary between fuel, electrolyte and electrode in cooperation with the catalyst particles located on the electrodes.

According to one embodiment of the invention, the conductive layer contains carbon or titanium nitrite. Both the use of carbon and titanium nitrite has the advantage of high chemical and mechanical stability, which is an important prerequisite for fuel cell use. Both carbon and titanium nitrite are required to be electronically highly conductive materials. For the conductive layers, however, generally any inorganic and organic materials can be used which have high chemical stability and low electrical resistance to the membrane.

In one embodiment of the invention, the carbon is carbon nanosheets and other carbon nanostructures in the form of pyrolytic carbon and CVD deposited carbon.

Nanostructured carbon has the advantage that the size of the electrode surfaces is increased due to the nano-structure. This significantly increases the number of active triple contact points between fuel, electrode and electrolyte. Using catalysts in the form of nanoparticles with narrow particle diameter distribution, the efficiency of a fuel cell in which such a membrane or membrane-electrode assembly is used, can be further increased with respect to significantly reduced volume compared to conventional electrodes, d. H. This results in a significant increase in power density or a reduced use of materials at the same power density.

According to one embodiment of the invention, the conductive layer contains carbon nanotubes and / or metal oxide nanotubes. These carbon nanotubes can be both single-walled and multi-walled. Preferably, the nanotubes are predominantly metallic.

Nano-carbon in the form of nanotubes offers some significant advantages over conventional, graphitic electrode material. On the one hand, the chemical bonds differ with regard to the degree of hybridization or the bond angle. It is easy to incorporate sp3 defects into the curved / strained structure, which enables targeted chemical modification of the nanotube surfaces ("functionalization"). By functionalizing the nanotubes both the mechanical and the chemical properties of the material can be changed or improved, which z. B. allows a targeted change in the surface properties of hydrophobic to hydrophilic.

Carbon nanotubes also have the advantage that they have an extremely high aspect ratio or very large surfaces. Another critical requirement for an electrode is the efficient transport of electrons. The remarkably high electrical conductivity of the nanotubes leads to only minor ohmic losses that are negligible compared to the membrane losses. In addition, since carbon nanotubes have a very high thermal conductivity, heat generated in the fuel cell reactions can be efficiently dissipated to the environment.

The use of carbon nanotubes also lends itself to solving another fuel cell problem which arises in the form of condensing water in fuel cell operation. Drop formation in the pores of the substrate results in the power of a fuel cell continuously decreasing during operation as the supply of fuel is inhibited. In order to counteract this, the surface of the electrodes used, in particular the cathode, should be water-repellent (hydrophobic), which can be achieved by targeted functionalization over a long-term stable period.

It should be noted that with the aid of aligned, nanostructured carbon, an additional mechanical stabilization of the electrode structure according to the invention can be achieved, for. B. by appropriately crosslinking functionalized carbon nanotubes, so that extremely thin membranes can be realized, which is not possible in the prior art.

According to one embodiment of the invention, the conductive layer is chemically functionalized. The chemical modification of the conductive layer has several functions: One function is the enabling of a selective deposition of catalyst particles, which requires formation of defined reaction points for deposition on or at the conductive layer. Thus, a homogeneous and well-defined arrangement of catalyst particles, on the electrode surface or embedded in the electrode surface layer can be realized.

Another function of the chemical modification is the targeted variation of hydrophilic / hydrophobic electrode surfaces. For z. B. functional groups of hydrophobic character are attached to the electrode surface, in the simplest case aliphatic hydrocarbons with different chain length. Fluorination of the same is also possible, in particular when using carbon structures, since this increases the hydrophobic character of such carbon structures.

A third function of a chemical modification of the electrodes is to allow as direct a connection as possible to the ionomers used in a fuel cell, or generally to the electrolytes used. This is necessary to achieve the best possible interaction in the form of Three-phase fuel, electrode and electrolyte realization. An optimal connection to such ionomers can be z. B. by binding of phosphonates or sulfonates to serve as an electrode structure serving carbons.

According to one embodiment of the invention, the membrane has a thickness of 50 nm to 50 microns, preferably 1 micron. The through holes have a diameter of 5 nm to 1 .mu.m, preferably 50 nm. The through holes are arranged substantially parallel to one another and have a spacing of between 5 nm and 50 μm, preferably 100 nm with respect to one another. This can be z. B. be realized with a substrate in the form of anodic aluminum oxide (AAO). AAO is formed by anodic oxidation of aluminum films using various acids as known in the art. The through holes that can be realized with such anodic alumina form a dense and parallel geometry to each other. Due to the almost perfect hexagonal structure over the surface of the substrate, a material is offered which meets the requirements for a high number of channels for the ion conduction with extremely low weight.

In addition to AAO, it is also possible to use as the substrate other electrically insulating materials which, as a basic requirement, have a multiplicity of nearly rectilinear channels which directly connect opposite sides of the substrate. Further possible substrates are therefore nanoscale porous crystalline layers, irradiated and subsequently etched layers, layers with oriented, chemically dissolvable nanowires or block structures with a dissolvable component.

According to one embodiment of the invention, the membrane further comprises an electrolyte, wherein this electrolyte is located in the through-holes. Such an electrolyte may include sulfuric acid, phosphoric acid, ion-conductive polymers, ion-conductive gels, and other proton conductors densely filling the pores. However, it is important that the electrolyte is in contact with the electrically conductive layer at the boundary zone of the mouth region of the through-holes. As already mentioned, this is absolutely necessary in order to guarantee the three-phase limit (fuel, electrode, electrolyte) necessary for the full functionality of the fuel cell. It is also essential that the effective layer thickness of the electrolyte is lower than the substrate layer thickness due to the deposition of the carbon into the pore opening. By varying the substrate thickness and the deposition conditions for the carbon layer, the electrolyte contribution can thus be optimized: the lowest possible substrate layer thickness and carbon contacts extending far into the pores reduce the ohmic losses to a minimum.

The selected membrane structure allows both the storage of proton-conducting media and the incorporation of other fuel cell-typical ionic conductors (hydroxyl, carbonate and oxygen ions) and is therefore not limited in principle to the fuel cell type PEFC.

In a further aspect, the invention relates to a method for producing a membrane for a membrane-electrode assembly comprising the step of providing a patterned porous substrate, wherein the substrate is formed by an electrically insulating material, the substrate having a first side and one of the first side opposite the second side, wherein the substrate has a plurality of through holes, each of the through holes connecting the first and the second side directly to each other. The method further includes the step of depositing an electrically conductive layer on the first and second sides of the substrate, and the step of applying catalyst particles to the first side and the second side of the substrate, wherein the electronically conductive layers mechanically stabilize the membrane. The catalyst particles can be applied to the conductive layer.

It should be noted, however, that the application of the catalyst particles to the substrate or to the conductive layer comprises any arrangement of the catalyst with respect to the conductive layer or the substrate. This can include both an arrangement of the catalyst particles on the side of the electrically conductive layer facing away from the substrate surface, and also any covering of the material forming the conductive layer by the catalyst particles. The arrangement of the catalyst particles in the electrically conductive layer may have a density profile, z. B. with a high catalyst concentration at the side facing away from the substrate surface of the conductive layer and with a decreasing concentration gradient in the direction of the substrate surface.

Finally, the method for producing a membrane further comprises the step of electrically burning the conductive layer in the through-holes. This step is necessary if, during the application of the conductive layer, the inner walls of the through holes are covered by the conductive layer so far that an electrical short circuit results. In order to remove this conductive layer on the inner walls, a voltage can be applied on the first and the second side of the substrate to the respectively likewise present electrically conductive layer, which leads to a high voltage being caused during heating the conductive layer within the pores is partially burned away. This ensures that there is no short circuit between the conductive layers on the first and second sides of the substrate.

According to one embodiment of the invention, the method for producing a membrane further comprises the step of chemically functionalizing the conductive layer.

According to one embodiment of the invention, the method for producing a membrane further comprises the step of activating the catalyst. However, this step of activating the catalyst is normally not necessary and is only relevant when the catalyst is due to z. B. functionalization processes has impurities that would affect the optimal operation of the catalyst.

According to another embodiment of the invention, the method for producing a membrane further comprises the step of introducing an electrolyte into the through-holes. Depending on the electrolyte used, this presupposes that the electrolyte is first liquefied, in order then to be sucked into the membrane independently due to the prevailing capillary forces of the through-holes.

According to a further embodiment of the invention, the application of the conductive layer takes place by chemical vapor deposition (CVD) or by selective coating or by polymer spin coating.

CVD uses a carbonaceous precursor gas, in the simplest case methane. CVD also allows - z. For example, in the goal of using carbon nanotubes as the electrode material, controlled growth of the carbon nanotubes directly on the substrate or on the substrate-stabilizing carbon layer at sites predefined by growth catalyst particles. Such catalyst may be catalyst particles deposited on the substrate surface, or may be thin metal or metal salt layers previously deposited on the substrate. By suitable choice of the production conditions, as well as the diameter of the catalyst particles, the length and the diameter of the resulting carbon nanotubes can be controlled in a targeted manner. It is also possible, for. B. to use such catalyst particles for the production of carbon nanotubes, which can also serve later as a fuel cell catalyst on. This eliminates an additional application of fuel cell catalyst particles, which simplifies the production of the membrane according to the invention.

The use of CVD z. For example, for the direct deposition of pyrolytic carbon has the advantage that films of pyrolitic carbon with a low surface roughness and thereby an extremely high aspect ratio of the structures produced can be obtained, which is particularly important for subsequent steps of functionalization or catalyst deposition. In addition, an extremely high mechanical stability of the membrane produced can be achieved by a controlled deposition of the pyrolytic carbon.

Another possibility of applying the conductive layer is, as already mentioned, by selective coating in the form of selective coating or spin coating. In this case, a carbon-containing polymer or generally any carbon-containing materials in liquid form is applied to the substrate surface. Due to surface tension effects, these liquid materials penetrate only slightly into the through holes of the substrate. This is important because the inner walls of the through holes should be covered only in the mouth region of the conductive layer. After coating the substrate surface with the carbonaceous material, the membrane is annealed (if necessary) at high temperatures, thereby converting the carbonaceous material into conductive carbon.

In further embodiments of the invention will be explained in more detail with reference to the drawings.

Show it:

1 : a perspective view of a membrane,

2 : another view of a membrane,

3 : a sectional view of a membrane,

4 FIG. 1 shows a flow chart of a method according to the invention for producing a membrane, FIG.

5 : further sectional views of membranes at different production times.

Hereinafter, similar elements are denoted by the same reference numerals.

The 1 shows a perspective view of a membrane. The membrane is through a substrate 100 formed, wherein the substrate 100 is formed by an electrically insulating material. The substrate 100 has a first page 102 and a second page 104 on, being the first page 102 the second page 104 opposite. On the first page 102 and the second page 104 each is an electrically conductive layer 106 ,

The substrate 100 also has a plurality of through holes 110 on, with each of the through holes 110 the first page 102 and the second page 104 connects directly and preferably straight to each other. Due to the presence of the through holes 110 are on the first page 102 and the second page 104 of the substrate openings 108 , The through holes 110 are only in the mouth area 302 , that is in the area of the visible opening 108 from the conductive layer 106 covered.

The conductive layers 106 , which on the first page 102 and the second page 104 are arranged, further comprise catalyst particles 112 on. In the present case, the catalyst particles 112 at random on the respective surface of the electrically conductive layers 106 distributed.

The one on the first page 102 and the second page 104 arranged electrically conductive layers 106 are also each with contacts 114 connected, via which an electrical voltage can be tapped. In the present example the 1 this is done via a measuring device 116 ,

For use as a fuel cell, the membrane is now in the 1 on the first page 102 with hydrogen H ₂ from the direction 118 lapped while the second page 104 of oxygen O ₂ from direction 120 is washed around. Due to the presence of the catalyst particles 112 on the first page 102 , hereinafter also referred to as anode, hydrogen is decomposed into protons (H ⁺ ) and electrons (e ^- ). The protons pass through the membrane to the side 104 , the cathode, passing through the through holes 110 diffuse from the anode to the cathode. This requires the presence of an electrolyte in the through holes. As the protons pass through the membrane to the cathode, the electrons flow through the external circuit through the contacts 114 to the second page 104 , At the cathode (the second page 104 ), atmospheric oxygen reacts with protons and electrons to form water. This reaction is also here of a noble metal, that is by catalyst particles 112 on the website 104 catalyzed. The reaction product is water 122 (H ₂ O).

The 2 shows a further view of a membrane. Only essential elements that contribute to the understanding of the invention are shown here. Decisive here is that the electrically conductive layer completely the surface of the electrically non-conductive substrate 100 covered on those opposite sides which are later to be lapped by fuel (eg hydrogen and oxygen). By the complete coverage of the substrate 100 through the electrically conductive layers 106 Ensures that by decomposing hydrogen into protons and electrons on the catalyst particles 112 the resulting electrodes efficiently directly over the upper contact 114 can be derived. The same applies to the reaction of atmospheric oxygen with protons and electrons to water at the bottom of the substrate 100 ,

The 3 shows a sectional view of a membrane. In particular, here are three through holes 110 with their respective openings 108 at the top and bottom of the substrate 100 shown. Just as clearly visible are the electrically conductive layers 106 , which respectively the top and bottom of the substrate 100 completely cover. On the electrically conductive layers 106 are now the catalyst particles 112 , which are necessary for the catalysis of hydrogen and oxygen to water.

Order now at the anode due to the presence of the catalyst 112 To transport resulting protons (H ⁺ ) from the upper conductive layer to the lower conductive layer, now serves the electrolyte 300 , which is for proton transport from the first (top) side 102 to the (sub) page 104 (second side) is formed. It is crucial that between the electrically conductive layer 106 , the catalyst particles 112 and the electrolyte 300 such a contact exists, that on the one hand, the fuel used for the operation of the fuel cell (eg, hydrogen or oxygen) optimally the catalyst particles 112 can flush around, but also simultaneously resulting protons efficiently from the top 102 to the bottom 104 over the electrolyte 300 can be transported. This requires optimal formation of the so-called three-phase boundary between fuel, electrode and electrolyte.

In the embodiment of the 3 is taken into account by the conductive layer in the area 302 slightly overhanging and thus into the through holes 110 protrudes. Through the overhang 302 it is now possible to realize the first condition for the three-phase boundary in that an optimal contact between conductive layer 106 and the electrolyte 300 in the area of the overhang 302 is guaranteed. In this case, preferably also catalyst particles 112 in the area of the overhang 302 Thus, an optimal dissipation of the resulting protons to the electrolyte 300 to ensure.

The electrically conductive layer 106 is preferably formed of a material or combination of materials which also imparts hydrophobic properties to the layer. This ensures that when water is generated, especially at the cathode on the side 104 , neither this water on the conductive layer 106 can attach, nor the water is able to the openings 108 adjacent diffusion channels of the gas diffusion layer to clog. As already mentioned, such a hydrophobic property of the conductive layer 106 on the one hand a natural property of the conductive layer 106 or this hydrophobic property can be generated by the conductive layer 106 accordingly chemically treated (functionalized) becomes. Preferably, the latter method, since it allows a much higher long-term stability.

Necessarily all insides must 304 the passage openings 110 free of material of the conductive layer 106 be to guarantee the functionality of the fuel cell. In particular, a continuous contact from the side 102 to the side 104 the conductive layer 106 would cause a short circuit between the page 102 and the page 104 lead, which would significantly affect the functioning of the fuel cell. In order to carry out a short-circuit test, or to eliminate any short circuit present, it is now advisable to switch between the page 102 the electrically conductive layer 106 and the page 104 the electrically conductive layer 106 once a correspondingly high voltage from the outside to apply, so that on the insides 304 the passage openings 110 located electrically conductive material, causing a short circuit between the side 102 and the page 104 causes, strongly heated and thus burned away. This eliminates any existing short circuit.

The 4 shows a flow diagram of a method according to the invention for producing a membrane. In step 400 the provision of the substrate, wherein, as already mentioned, the substrate is formed by an electrically insulating material having a first and a first side opposite second side, and also the substrate has a plurality of through holes, each of the through holes, the first and the second side connects directly to each other. After providing the substrate in step 400 the conductive layer is applied to the first side and the second side of the substrate. Subsequently, the application of the catalyst takes place 112 in step 408 and in a final step, introducing the electrolyte into the through holes of the provided substrate.

Optional and not mandatory are now the steps 404 . 406 and 410 , In step 404 offers the opportunity to step after 402 , the application of the conductive layer to functionalize the conductive layer in a suitable manner. However, step can 404 also before step 402 be performed by applying already functionalized electrically conductive material by suitable methods on the first and second sides of the provided substrate. Also optional is after step 404 the step 406 which is a heating or burning in step 402 envisages applied layers. The heating in step 406 is under some circumstances necessary to a conversion of z. For example, to obtain carbonaceous materials in pure carbon or other carbon forms, thereby improving the conductivity of the layer. The burning in step 406 is necessary when shorts between the first and second sides are present through the electrically conductive layer.

The step 410 can optional after step 408 , the application of the catalyst 112 , respectively. step 410 includes activating the catalyst 112 what z. B. is necessary if the catalyst 112 due z. B. a functionalization process in step 404 was contaminated.

5 shows membranes at different production times. The aim is to produce a carbon nanotube-stabilized membrane. These are starting from the membrane 502 containing the structured porous substrate 100 including the electronically conductive layer 106 has, carbon nanotubes 500 on the conductive layer 106 grew up. This results in the membrane 504 , Sense of the additional growth of the nanotubes 500 is a mechanical stabilization of the membrane, as well as providing a large surface area to which catalyst particles 112 can be applied. This results in the membrane 506 , For increased mechanical stabilization are the nanotubes 500 crosslinked, which also increases the overall conductivity of the conductive layer.

Finally, the through holes 110 the membrane with an electrolyte 300 such as As a gel, polymer or a liquid filled, resulting in the finished membrane 508 results.

LIST OF REFERENCE NUMBERS

100

substratum

102

first page

104

second page

106

conductive layer

108

opening

110

Through Hole

112

Catalyst particles

114

Contact

116

gauge

118

Hydrogen supply

120

oxygen supply

122

water

300

electrolyte

302

overhang

304

Inner wall surface

500

nanotubes

Claims (7)

A process for producing a membrane for a membrane-electrode assembly comprising the following steps: - providing a structured porous substrate ( 100 ), the substrate ( 100 ) is formed by an electrically insulating material, wherein the substrate ( 100 ) a first page ( 102 ) and a second side opposite the first side ( 104 ), wherein the substrate ( 100 ) a plurality of through holes ( 110 ), wherein each of the through holes ( 110 ) the first and second pages ( 104 ) directly to each other, - applying an electrically conductive layer on the first and the second side ( 104 ) of the substrate ( 100 ), wherein the electronically conductive layer ( 106 ) mechanically stabilizing the membrane, - applying catalyst particles ( 112 ) on the first page ( 102 ) and the second page ( 104 ) of the substrate ( 100 ), - electrically burning the conductive layer in the through holes ( 110 ). Process for producing a membrane according to claim 1, wherein the catalyst comprises particles ( 112 ) on the conductive layer ( 106 ) are applied. A process for producing a membrane according to any one of the preceding claims 1 or 2, further comprising the step of chemically functionalizing the conductive layer. Process for producing a membrane according to one of the preceding claims 1 to 3, further comprising the step of activating the catalyst ( 112 ). A process for producing a membrane according to any one of the preceding claims 1 to 4, further comprising the step of introducing an electrolyte ( 300 ) into the through holes ( 110 ). Process for producing a membrane according to one of the preceding claims 1 to 5, wherein the application of the conductive layer by chemical vapor deposition (CVD) or by selective coating or by polymer spin coating takes place. A process for producing a membrane according to any one of the preceding claims 1 to 6, further comprising the step of annealing the membrane.

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