Method for producing a composite layer, electrochemical cell and use of the composite layer

Abstract

The present invention relates to a method by which composite layers can be produced as simply and controlled as possible, and composite layers having different predetermined properties can be produced with minimal effort and thus economically. The method comprises: providing a nanofiber material; comminuting the nanofiber material to form nanorods; providing a liquid medium comprising an ionomer component and a dispersant; dispersing the nanorods in the liquid medium to form a nanorod ionomer dispersion; and applying the nanorod ionomer dispersion to a surface area of ​​a substrate to form the composite layer.

Description

Technical Field

[0001] The invention relates to a method for producing a composite layer for electrochemical applications.

[0002] The invention further relates to an electrochemical cell comprising the composite layer according to the invention.

[0003] The invention furthermore relates to the use of the composite layer according to the invention in fuel cells, in particular hydrogen fuel cells or direct alcohol fuel cells, in redox flow batteries, in electrolyte cells or in ion exchangers. Background Art

[0004] The scientific article "Cerium oxide decorated polymer nanofibers as effective membrane reinforcement for durable, high-performance fuel cells" by M. Breitwieser et al., Adv. Energy Mat. (2017) 1602100, discloses the preparation of composite membranes for fuel cells by direct membrane deposition. The article discloses poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers decorated with CeO2 nanoparticles and their direct production on gas diffusion electrodes by electrospinning. The resulting nanofiber fabric is then printed by inkjet printing. Ionomer dispersion for impregnation. Ionomers are perfluorinated copolymers containing sulfonic acid groups.

[0005] It is also known from the scientific publications “Electrospun sulfonated poly(ether ketone) nanofibers as proton conduction enhances for durable nafion composite membranes” by C. Klose et al., Journal of Power Sources, 361 (2017) 237-242 and “Simple fabrication of 12 μm thin nanocomposite fuel cell membranes by direct electrospinning and printing” by M. Breitwieser et al., Journal of Power Sources 337 (2017) 137-144, to apply a fiber fabric produced by electrospinning and subsequently utilize Saturation by printing and coating.

[0006] The mentioned article relates to the preparation of electrochemically active composite layers.

[0007] A polymer membrane comprising an ion exchanger resin and melt-spun fluororesin fibers is known from US 2005 / 0214611 A1.

[0008] US 2017 / 0279142 A1 discloses an electrolyte membrane comprising a porous nanofiber mat and an ion-conducting polymer.

[0009] From CN 201170183 B a membrane reinforced with carbon nanotubes is known.

[0010] CN 101237055 A discloses a perfluorinated proton exchange membrane reinforced with inorganic fibers.

[0011] The electrochemically active composite layer serves to conduct, in particular charged reactants or products of an electrochemical reaction, such as protons or anions. The electrochemically active composite layer typically comprises an ionomer and one or more components for mechanical reinforcement, such as nanofibers.

[0012] When producing electrochemically active composite layers according to the prior art, multiple work steps are typically required to integrate the nanofibers into the ionomer material. This increases the time and cost expenditure and, on the one hand, makes the composite layer inaccessible for so-called roll-to-roll processes.

[0013] In a roll-to-roll method, a flexible coating material is typically unwound from a roll for coating a surface and, after processing (here: coating), is rolled up again for intermediate storage. Summary of the Invention

[0014] The object of the present invention is to provide a method by means of which composite layers can be produced as simply and controlled as possible and by which composite layers having different predetermined properties can be produced with the lowest possible outlay and thus economically.

[0015] According to the invention, this object is achieved by a method for producing a composite layer, wherein the method comprises:

[0016] -Provide nanofiber materials;

[0017] - pulverizing the nanofibrous material to form nanorods;

[0018] - providing a liquid medium comprising an ionomer component and a dispersant;

[0019] - dispersing the nanorods in a liquid medium to form a nanorod ionomer dispersion; and

[0020] - Applying the nanorod ionomer dispersion to the surface area of ​​the substrate to form a composite layer.

[0021] The comminution of the nanofibrous material results in nanorods which are particularly easily dispersible compared to uncomminuted nanofibrous material.

[0022] Due to the dispersibility, an ionomer-containing dispersion can be prepared, and the nanorods can thus be applied to the substrate together with the ionomer component in one working step, thereby making an additional working step for applying the ionomer component superfluous.

[0023] Furthermore, the mixing of the nanofiber material comminuted into nanorods and the ionomer component can be optimized by forming a nanorod ionomer dispersion. Thus, the nanorods can be in contact with or embedded in the ionomer component. This enables the resulting composite layer to have uniform, good proton or anion conductivity throughout the entire longitudinal extent of the composite layer.

[0024] For the purposes of the present invention, "nanorods" include all structures whose extent along a first spatial direction is 100 times greater or more than their extent along other spatial directions oriented perpendicular to the first spatial direction. The extent along the other spatial directions of the nanorod is approximately 3000 nm or less, in particular approximately 1000 nm or less. For example, the term "nanorod" also includes so-called nanowires and so-called nanowhiskers.

[0025] The composite layer is preferably suitable as a component of a membrane in a low-temperature fuel cell, in particular a polymer electrolyte fuel cell.

[0026] The composite layer preferably forms a coating of a polymer electrolyte membrane of a polymer electrolyte fuel cell. In a polymer electrolyte fuel cell, the polymer electrolyte membrane is typically arranged between two catalyst layers of an electrode of the polymer electrolyte fuel cell.

[0027] Alternatively, the polymer electrolyte membrane may be formed completely from composite layers.

[0028] It can be provided that the nanorod ionomer dispersion is applied only to individual areas of the substrate surface. For this purpose, for example, a mask can be used so that, in addition to areas of the substrate without a composite layer, areas of the substrate with a composite layer can also be produced in a controlled and spatially separated manner.

[0029] Alternatively, it can be provided that the composite layer is applied over the entire surface of the substrate to be coated.

[0030] The composite layer can in particular be designed to be individually handleable. In the case where the interaction between the surface of the substrate and the composite layer is not so strong, the composite layer in the surface region of the substrate can be peeled off from the substrate after the composite layer has been formed.

[0031] The substrate can be a component of the electrode or a supporting membrane. This will be discussed in detail later. The liquid medium can essentially consist of an ionomer component and a dispersant.

[0032] In the sense of the present invention, a dispersant may be a solvent. The ionomer component may be completely dissolved, partially dissolved and partially dispersed, or substantially only dispersed in the dispersant.

[0033] Preferred dispersants are alcohols, alcohol mixtures, and alcohol-water mixtures. Particularly preferred are methanol, ethanol, 2-propanol, or 1-butanol, or mixtures of these alcohols, or mixtures of these alcohols with water. Many substances, particularly polar substances, are readily soluble in the aforementioned dispersants, and the aforementioned dispersants are not very toxic.

[0034] However, the dispersing additive or other additives can also be contained in the liquid medium. The dispersing additive or other additive particularly supports the dissolution or dispersion of the ionomer component and / or the nanorods. The dispersing additive or other additive is preferably substantially only dissolved in the dispersant, partially dissolved in the dispersant and partially dispersed in the dispersant, or substantially only dispersed in the dispersant.

[0035] The nanofibrous material is preferably provided by means of an electrospinning method.

[0036] Electrospinning methods for nanofibers made of polymeric materials are known, for example, from the scientific article "Beaded nanofibers formed during electrospinning" by H. Fong et al., Polymer, Vol. 40 (1999), pp. 4585-4592.

[0037] In the electrospinning method, typically, a precursor solution is injected into an electric field through a nozzle at a limited injection rate. The electric field is formed by an accelerating voltage provided between the nozzle and the counter electrode. The nozzle and the counter electrode are at a limited distance from each other. In particular, a nozzle with a diameter that is optimized for the respective material of the nanofiber to be produced is selected. After injection, the precursor solution is drawn out of the nozzle and accelerated toward the counter electrode due to the accelerating voltage provided. During this process, nanofibers are formed, which are deposited on the substrate or on the counter electrode.

[0038] The precursor solution includes a suitable solvent and / or dispersant and one or more raw materials, which are selected according to the type of nanofiber material to be prepared.

[0039] The injection rate in the electrospinning method according to the present invention is preferably in the range of about 0.1 μl / min to about 600 μl / min.

[0040] Preferred nanofiber materials include polymer-based, metal oxide-based nanofibers that are metal-coated or decorated with metal oxide nanoparticles. Each preferred nanofiber material will be described in more detail below.

[0041] For the production of nanofibrous materials based on polymeric materials, it can be advantageous if the infusion rate is in the range of approximately 2 μl / min to approximately 20 μl / min, in particular in the range of approximately 5 μl / min to approximately 18 μl / min.

[0042] In the case of nanofibers decorated with nanoparticles, the nanoparticles are arranged on the nanofibers and fixed thereto.

[0043] Metal oxide-based nanofibers, in particular titanium dioxide-based and ceria-based nanofibers, or metal-coated nanofibers, in particular platinum-coated nanofibers, are preferably injected into the electric field at an injection rate in the range of about 400 μl / min to about 600 μl / min, in particular in the range of about 450 μl / min to about 550 μl / min, for example about 500 μl / min.

[0044] Preferably, the accelerating voltage between the nozzle and the counter-electrode is in the range of approximately 5 kV to approximately 30 kV, in particular in the range of approximately 10 kV to approximately 20 kV, for example in the range of approximately 12 kV to approximately 19 kV.

[0045] The distance between the nozzle and the counter-electrode is, for example, approximately 10 cm to approximately 20 cm. The diameter of the nozzle is preferably in the range of approximately 0.1 mm to approximately 1 mm.

[0046] The precursor solution for the electrospinning method to be used according to the present invention, which is injected into the electric field through a nozzle, preferably comprises one or more polymers, a solvent and lithium chloride.

[0047] In embodiments providing nanofiber materials comprising nanoparticles, the precursor solution injected into the electric field includes nanoparticles in addition to the aforementioned components.

[0048] For the production of nanofibers based on metal oxides, the precursor solution preferably comprises, in addition to the aforementioned components, a metal salt or a covalent or complex metal compound which can be converted into the corresponding metal oxide. For example, the oxidation of metal nitrates to metal oxides is suitable for this.

[0049] The electrospinning method offers the advantage of being able to flexibly adjust the method, so that different nanofiber materials can be obtained using the same device. If the nanofibers are to be made of other materials, only the accelerating voltage, the composition of the precursor solution, the injection rate, the distance between the nozzle and the counter electrode, and the nozzle diameter must be adjusted.

[0050] According to a preferred embodiment, a needle-free electrospinning method is used to prepare the nanofiber material.

[0051] Needle-free electrospinning methods are also referred to as so-called "needleless" electrospinning methods or "needle-free" electrospinning methods.

[0052] The needle-free electrospinning method is preferably a variant of the static electrospinning method.

[0053] A preferred apparatus for carrying out the needle-free electrospinning process is commercially available from ELMARCO SRO, Liberec XI, 46001, Czech Republic.

[0054] Devices are known, for example, from WO 2008 / 028428 A1, WO 2008 / 011840 A2 and WO 2009 / 049565 A2.

[0055] The needle-free electrospinning method has the advantage that the electrode needles (nozzles) do not become clogged, as can occur in conventional electrospinning methods. Consequently, the corresponding equipment does not require frequent maintenance.

[0056] In one embodiment of the needle-free electrospinning method, the apparatus may include a rotating electrode, for example, in the form of a metal cable. A counter electrode moves relative to the rotating electrode. Nanofibers are formed at a position on the rotating electrode where the counter electrode is sufficiently close to the rotating electrode. The nanofibers are formed from a thin film of a precursor solution, which forms on the surface of the rotating electrode and is typically continuously refilled from a reservoir.

[0057] The accelerating voltage provided between the rotating electrode and the counter electrode is preferably about 1 kV or greater, and / or about 20 kV or less.

[0058] As an alternative to providing the nanofibrous material by means of an electrospinning method, it can be provided that the nanofibrous material is provided by means of a centrifugal spinning method.

[0059] Centrifugal spinning methods are known from the review by Z. Zhiming et al., “Research on the development of the centrifugal spinning”, MATEC Web of Conferences 95 (2017) 07003.

[0060] In the centrifugal spinning method, a precursor solution is injected through a nozzle rotating at a preset rotation speed, and then nanofibers are generated based on centrifugal force, which are deposited on a substrate.

[0061] The rotation speed in the centrifugal spinning method according to the present invention is preferably in the range of about 10 rpm to about 6000 rpm.

[0062] The advantage that the centrifugal spinning method provides is that the structure of the apparatus for centrifugal spinning is very simple and comprises a small number of components.In addition, the method is robust to fluctuations in the relative humidity in the environment in which the method is carried out.

[0063] According to a further alternative method for producing the nanofibrous material, it can be provided that the nanofibrous material is provided by means of a solution blow spinning method.

[0064] The solution blow spinning process is known, for example, from US Pat. No. 8,641,960 B1.

[0065] In the solution blown spinning method, a precursor solution is introduced into a carrier gas stream through an inner nozzle. The carrier gas stream is then introduced into the space where the nanofibers are formed through an outer nozzle. The nanofibers are formed by selecting an appropriate carrier gas pressure.

[0066] In the solution blown spinning method according to the invention, the injection rate is preferably in the range of about 10 μl / min to 30 μl / min. The injection rate is particularly in the range of about 12 μl / min to about 22 μl / min, for example in the range of about 15 μl / min to about 18 μl / min.

[0067] In the solution blow spinning process, the gas pressure of the carrier gas flow is in particular in the range from about 100 kPa to about 500 kPa.

[0068] The nanofiber material to be provided according to the present invention is preferably provided as a fiber body. In particular, the nanofiber material is provided as a random non-crimp fabric and / or a non-woven fabric and / or a fiber mat.

[0069] The nanofiber material is particularly provided as an oriented non-crimped fabric.

[0070] Providing the nanofiber material as a fiber body simplifies handling in the further process, since the fiber body can be handled as a whole, preferably with the aid of a gripping tool (for example with tweezers in laboratory standards).

[0071] It may be advantageous if the nanofibrous material comprises nanofibers having an average diameter of about 20 nm to about 3000 nm, preferably about 50 nm to about 700 nm.

[0072] Particularly preferably, the nanofibrous material consists essentially of nanofibers having an average diameter of approximately 20 nm to approximately 3000 nm, preferably of approximately 50 nm to approximately 700 nm.

[0073] Preferably, the average diameter of the nanofibers of the nanofibrous material is about 50 nm or more, in particular about 100 nm or more.

[0074] In particular, the nanofibers of the nanofibrous material have an average diameter of approximately 3000 nm or less, such as approximately 700 nm or less.

[0075] An average diameter of about 20 nm for the nanofibers is often sufficient to provide sufficient strength to the resulting composite layer, while a diameter of about 3000 nm is still small enough that the resulting nanorods can be embedded in the ionomer component after comminution.

[0076] According to a preferred embodiment, the ratio of the average diameter of the nanorods of the nanomaterial to the thickness of the resulting composite layer is about 1 / 20 or less.

[0077] The average diameter of the nanofibers or nanorods resulting from the comminution and / or the average length of the nanorods resulting from the comminution (this will be discussed in detail later) are determined using possible measures based on electron microscopy images, in particular scanning electron microscopy images. The scanning electron microscopy images are evaluated with respect to the average diameter and / or average length using an image processing program. The average diameter or average length is then determined from the data obtained using the image processing program using an algorithm.

[0078] The mean diameter and / or mean length are in particular stated as arithmetic mean values.

[0079] The average diameter and / or average length mentioned below are determined as described above using scanning electron microscope images.

[0080] The elemental composition of the nanofibrous material is determined by means of possible X-ray spectroscopy, in particular by means of energy dispersive X-ray spectroscopy (EDX) and / or X-ray fluorescence (XRF).

[0081] It can be provided that the nanofibrous material is thermally retreated before comminution or the nanorods resulting from comminution are thermally retreated before dispersion.

[0082] For this purpose, the nanofibrous material is preferably sintered before comminution or the nanorods are preferably sintered before dispersion.

[0083] For thermal post-treatment, in particular sintering, temperatures in the range of approximately 250° C. to approximately 1500° C., in particular 400° C. to approximately 600° C., have proven to be particularly advantageous.

[0084] With regard to different aspects of the resulting composite layer (for example the mechanical stability of the composite layer or the chemical resistance of the composite layer), different nanofiber materials are particularly suitable for the method according to the invention.

[0085] Preferably, the nanofiber material comprises one or more of the following materials: an oxide, preferably a metal oxide, especially ceria, and / or a transition metal oxide, such as titanium dioxide and / or manganese oxide, and a polymeric material.

[0086] Depending on the nanofiber material embedded in the composite layer in comminuted form as nanorods, the resulting composite layer has different properties. The nanofiber material is selected depending on the properties that the resulting composite layer should have.

[0087] In order to provide the nanofiber material with a higher chemical resistance of the resulting composite layer, nanofibers based on materials with free radical scavenging properties are particularly suitable. For example, the use of nanofibers comprising or essentially consisting of ceria can improve the chemical resistance of the resulting composite layer.

[0088] With regard to improving the mechanical properties of the resulting composite layer, hydrophobic polymers, in particular polytetrafluoroethylene (PTFE), polybenzimidazole (PBI), polyvinylidene fluoride (PVDF), polyetheretherketone (PEEK), polyolefins, in particular polyethylene (PE) and polypropylene (PP), have proven to be particularly advantageous materials for the nanofibers of the nanofibrous material.

[0089] In the preparation of ceramic nanofibrous materials for improving the chemical and mechanical properties of the resulting composite layer, hydrophilic polymers, in particular polyvinylpyrrolidone (PVP), have proven to be particularly suitable materials for the nanofibers of the nanofibrous materials. They serve, in particular, as carrier polymers and are oxidized to carbon dioxide, nitrogen oxides, and water during the thermal reprocessing step and are thus removed (due to the volatility or evaporation of the oxidation products).

[0090] A material or substance is considered "hydrophilic" when it is soluble in water at 25°C, miscible with water, absorbs water, or more generally interacts with polar substances. In particular, a material or substance is considered "hydrophilic" when it falls within the IUPAC nomenclature of "hydrophilicity." According to IUPAC nomenclature, hydrophilicity is the tendency of a molecule to solvate in water.

[0091] A material or substance is considered "hydrophobic" when it is insoluble in water at 25°C and cannot be mixed with water. Specifically, a material or substance is considered "hydrophobic" when it falls under the IUPAC nomenclature of "hydrophobicity." According to IUPAC nomenclature, hydrophobicity is the tendency of non-polar groups or molecules to aggregate in an aqueous environment because water tends to repel them.

[0092] In particular, the nanofiber material comprises one or more conjugated polymers and / or one or more non-conjugated polymers.

[0093] Preferred polymers for the ionomer component will be described in more detail below. However, in this case, the ionomer component should already be characterized as follows: it preferably includes at least one polymer having a polymer backbone. The polymer backbone is formed, for example, from carbon chains having fluorinated methylene groups or longer-chain fluorinated carbon residues. The fluorinated methylene groups or longer-chain carbon residues preferably interact with the components of the nanofiber material.

[0094] For the preparation of nanofibrous materials, preference is given to using polymers which can interact with the polymer backbone of the ionomer component, for example via van der Waals interactions or via hydrogen bonding interactions.

[0095] Preferably, the ionomer component comprises at least one polymer having one or more sulfonate functional groups. The sulfonate functional group is in particular arranged at one end of a carbon side chain branching from the polymer backbone. In this variant of the ionomer component, it can be advantageous if the nanofiber material comprises one or more polymers that can interact with the sulfonate functional group(s) of the ionomer component, for example via ionic interactions or via hydrogen bonding interactions. Typical examples of such ionomer components are Perfluorinated copolymers available under the brand name TRIFLORIN®.

[0096] Furthermore, polymers which themselves have a thermally and / or chemically stable polymer backbone are preferably used for producing the nanofibrous material. This can be advantageous for the proton conductivity or anion conductivity of the resulting composite layer.

[0097] Furthermore, it can be advantageous if the nanofibrous material comprises one or more polymers which have strong intermolecular interactions, for example by van der Waals interactions or interactions via hydrogen bonds.

[0098] To prepare thermally and chemically reinforced ceramic nanofibers for the resulting composite layer, a carrier polymer having a molecular weight in the range of about 300,000 g / mol to about 3,000,000 g / mol is preferably used. Such a carrier polymer is suitable for forming a homogeneous dispersion or solution of a raw material that serves as a raw material for metal oxide-based nanofibers. Precursor solutions containing the carrier polymer and the raw material for metal oxide-based nanofibers are particularly easy to process into nanofibers.

[0099] The material of the nanofibers of the nanofibrous material is preferably selected depending on the properties that the resulting composite layer should have.

[0100] For example, a particularly high mechanical stability of the resulting composite layer is achieved using PBI-based nanofibers.

[0101] It was found that the resulting composite layer has a particularly high chemical stability using nanofibers based on ceria.

[0102] Optimized thermal stability of the resulting composite layer is preferably achieved with nanofibers based on titanium dioxide or with other nanofibers based on metal oxides.

[0103] It may be provided that the nanofibrous material comprises or essentially consists of coated nanofibers, preferably nanofibers coated with a noble metal, in particular with platinum and / or palladium.

[0104] In particular, the coating of the nanofibers can be prepared by adding corresponding raw materials to the precursor solution of the electrospinning method. The preparation of the nanofibers coated with precious metals will be described in more detail below.

[0105] In order to optimize the chemical and / or thermal and / or mechanical stability of the nanofibrous material and the resulting composite layer, it may be provided that the nanofibrous material, which may be in the form of a fibrous body, is functionalized before comminution (particularly with regard to the anion conductivity or proton conductivity of the resulting composite layer). This will be described below with reference to examples.

[0106] For this purpose, the nanofibrous material (possibly in the form of a fiber body) is preferably contacted with caustic soda or potash or sulphuric acid or phosphoric acid or a metal salt solution.

[0107] In particular, the nanofibrous material (possibly in the form of a fiber body) is heated in caustic soda or caustic potash or sulfuric acid or phosphoric acid or a metal salt solution.

[0108] Suitable metal salt solutions are, in particular, platinum salt solutions, rhodium salt solutions, palladium salt solutions, ruthenium salt solutions or mixed metal salt solutions, for example platinum-cobalt salt solutions or platinum-nickel salt solutions or mixtures thereof.

[0109] In particular, the anion conductivity can be increased by exposing the nanofiber material to caustic soda (sodium hydroxide solution) or caustic potash (potassium hydroxide solution) and / or heating it therein. This is particularly advantageous for use of the resulting composite layer in an anion exchanger.

[0110] When the nanofibrous material is exposed to sulfuric acid and / or heated therein, the nanofibrous material interacts with the sulfate groups of the sulfuric acid, wherein the sulfate groups are at least partially physically or chemically bound to the surface of the nanofibrous material.

[0111] If the nanofibrous material is brought into contact with phosphoric acid and / or heated in phosphoric acid, the phosphate groups of the phosphoric acid interact with the surface of the nanofibrous material, wherein the phosphate groups are in particular physically or chemically bound there.

[0112] By interaction with sulfate or phosphate groups, the proton conductivity of the nanofibrous material and thus also of the resulting composite layer can be increased.

[0113] When using mixed metal salt solutions, in particular alloys composed of different metals of a mixed metal salt, for example a platinum-nickel salt, can be formed in a subsequent sintering step.

[0114] In particular, the metal ions of the metal salt solution can be ionically bound to the surface of the nanofibrous material or form an island structure on the surface of the nanofibrous material.

[0115] As an alternative to the functionalization of the nanofibrous material, it can be provided that the nanorods produced by comminuting the nanofibrous material are functionalized. The above explanations regarding the functionalization of the nanofibrous material also apply to the nanorods.

[0116] Preferably, a nanofibrous material (possibly in the form of a fiber body) is provided, wherein the nanofibrous material and / or the fiber body comprises one or more additives. In particular, the one or more additives form an integral part of the nanofibers of the nanofibrous material. In particular, the one or more additives are applied to the nanofibers and / or the one or more additives are mixed with the nanofibers.

[0117] It may be advantageous if the additive or at least one of the additives comprises granular and / or fibrous functional nanoparticles.

[0118] Granular functional nanoparticles are also called nanoparticles.

[0119] The granular and / or fibrous functional nanoparticles preferably comprise platinum, palladium, platinum cobalt, zirconium phosphate, zeolite materials, silicon oxide and / or one or more metal oxides, in particular one or more metal oxides selected from cerium dioxide and transition metal oxides, such as titanium oxide and / or manganese oxide.

[0120] It can be provided that the nanofibers of the nanofiber material are provided doped with a metal oxide, for example, ceria. For ceria (CeO2) doping, for example, nanofibers doped with cerium nitrate are produced and / or provided, which are subsequently oxidized to ceria nanofibers, in particular by thermal post-treatment, in particular in air at approximately 400° C. to approximately 600° C. The carrier polymer, for example PVP, is also oxidized, allowing its volatile or vaporizable oxidation products (carbon dioxide, nitrogen oxides, and water) to escape.

[0121] It can be advantageous to subject the nanofibrous material to mechanical energy during and / or for the comminution, and the nanofibrous material is preferably comminuted by means of ultrasound treatment and / or mechanical comminution. For mechanical comminution, the nanofibrous material is preferably comminuted in a ball mill or mortar. It can also be provided that several of the aforementioned comminution variants are used in succession to achieve particularly uniform comminution.

[0122] For ultrasonic treatment, an ultrasonic blaster is preferably used, which is operated, for example, at a power of about 200 to about 300 W, particularly at a power of about 250 W. The ultrasonic blaster is used to place the container in an ultrasonic bath subjected to ultrasonic vibrations. A container is placed in the ultrasonic bath, the nanofiber material and the liquid medium are placed in the container, and the container is then treated with ultrasound. The liquid medium can be a dispersant for the nanorod dispersion generated during the ultrasonic treatment.

[0123] In particular, the ultrasonic spray gun is operated at a power of about 0.1 W per ml of nanorod dispersion generated to about 10 W per ml of nanorod dispersion generated.

[0124] The nanofiber material is preferably comminuted in an ultrasonic bath for about 1 hour to about 3 hours, for example, about 2 hours to form nanorods.

[0125] The ionomer component can be added to the remaining components of the liquid medium after or before comminution of the nanofiber material.

[0126] In addition to or as an alternative to comminution by application of mechanical energy, the nanofibrous material (depending on the material composition of the nanofibrous material) is applied with thermal energy for comminution.

[0127] For example, in a nanofibrous material comprising or consisting essentially of titanium dioxide nanofibers or cerium nitrate nanofibers, the thermal energy in the (previously described) thermal re-treatment may be sufficient to comminute the nanofibrous material into nanorods.

[0128] The thermal post-treatment is preferably carried out at approximately 400° C. to approximately 600° C. for approximately 3 hours to approximately 9 hours. Particularly preferably, the thermal post-treatment is carried out at approximately 500° C. for approximately 6 hours.

[0129] As already mentioned, thermal retreatment is preferably used to remove the carrier polymer, whose oxidation products (carbon dioxide, nitrogen oxides and water) are usually volatile or vaporizable, and, if necessary, to oxidize the metal nitrate to the corresponding metal oxide (e.g., oxidation of cerium nitrate to cerium dioxide) or (in the case of metal coating) to reduce the metal ion due to oxidation of the ligand bound thereto (e.g., oxidation of the acetylacetonate ligand from platinum acetylacetonate).

[0130] When the comminution is induced by applying thermal energy, the resulting nanorods are dispersed in a liquid medium (with or without an ionomer component). The ionomer component can be added before, during, or after the dispersion of the nanorods.

[0131] The liquid medium preferably comprises one or more of the following materials: a fluorinated copolymer having sulfonic acid groups, in particular PFSA (perfluorosulfonic acid), Also non-fluorinated polymers, in particular hexamethyl-p-terphenyl-poly(benzimidazole), polysulfones, such as polyarylethersulfone, ethylenetetrafluoroethylene copolymers and polyetheretherketone (PEEK).

[0132] The aforementioned materials or material combinations preferably form an ionomer component. The ionomer component is preferably used to provide or enhance proton conductivity or anion conductivity.

[0133] Nanorods of defined size can be obtained by pulverization.

[0134] The aspect ratio of the average length to the average diameter of the nanorods is preferably in the range of about 5 to about 25,000, especially in the range of about 10 to about 500.

[0135] The nanorods preferably have an average length of approximately 2 μm to approximately 500 μm, in particular approximately 5 μm to approximately 30 μm.

[0136] According to the aforementioned procedure, the aspect ratio and the average length are preferably determined by means of images taken with a scanning electron microscope.

[0137] After the nanorod ionomer dispersion has been prepared according to the aforementioned preferred variant, the nanorod ionomer dispersion (as already mentioned) is applied to the surface region of the substrate.

[0138] Application of the nanorod ionomer dispersion is preferably carried out by one or more of the following methods known per se: drop coating, print coating methods, in particular doctor blade coating, screen printing, slot printing, engraving printing, inkjet printing and spraying methods.

[0139] When it comes to imposition, different perspectives can play a role.

[0140] The resulting variation in the composition of the composite layer in a direction perpendicular to the longitudinal mid-plane of the composite layer can be advantageous. Different compositions of the composite layer on the anode and cathode sides of the fuel cell can be advantageous, for example, when the composite layer is used in a membrane of a fuel cell.

[0141] For the resulting variation of the composition of the composite layer in a direction perpendicular to the longitudinal midplane, it can be advantageous to apply the nanorod ionomer dispersion in multiple coatings and, in particular, to produce the multiple coatings using nanorod ionomer dispersions having different compositions in each case.

[0142] As an alternative to applying multiple layers of nanorod ionomer dispersion, the nanorod ionomer dispersion can be applied to the surface area in one layer. This has the advantage that only a single application step is required. Doctor blade coating (also known as Rakelbeschichtung) is particularly suitable for applying a single layer. Doctor blade coating of nanorod ionomer dispersions can reproducibly produce composite layers with a uniform total thickness.

[0143] By applying multiple layers of the nanorod ionomer dispersion, it is possible, for example, to form a composite layer having a variation in the nanorod concentration in a direction perpendicular to the longitudinal midplane of the composite layer, for example having a concentration gradient.

[0144] For this purpose, in particular, multiple coatings of different nanorod ionomer dispersions with different nanorod concentrations are applied successively to the surface area of ​​the substrate or to a previously applied coating, with a concentration gradient in the resulting composite layer, the nanorod concentration of the nanorod ionomer dispersion increasing or decreasing layer by layer.

[0145] Spraying is particularly suitable for the application of multiple layers of nanorod ionomer dispersions, since the liquid to be sprayed can be easily changed in corresponding apparatuses.

[0146] As an alternative to the nanorod concentration gradient in the resulting composite layer, an intermediate layer can also be formed in the resulting composite layer in a targeted manner by applying multiple layers of nanorod ionomer dispersions of different compositions. The intermediate layer preferably has a different composition than the remaining composite layers.

[0147] The nanorods are preferably contained in the nanorod ionomer dispersion in a proportion of about 1 to about 50 weight percent, in particular about 2 to about 40 weight percent, for example about 5 to 35 weight percent, relative to the total weight of the dispersion.

[0148] For the electrochemical properties of the composite layer, in particular with regard to proton conductivity or anion conductivity, it has proven particularly advantageous if the non-ionomer content of the composite layer is in the range of approximately 5% by weight to approximately 20% by weight. The non-ionomer content includes all components of the composite layer except the ionomer component.

[0149] The ionomer component is preferably contained in the composite layer in a proportion of approximately 80% to approximately 95% by weight relative to the total weight of the composite layer. This enables sufficiently high proton conductivity or anion conductivity through the composite layer to be achieved via the ionomer component.

[0150] Whether proton conductivity or anion conductivity is enhanced depends on the selection of the ionomer components, which will be described in more detail later.

[0151] Preferably, the composite layer has a total thickness in the range of approximately 1 μm to approximately 100 μm, in particular in the range of approximately 2 μm to approximately 80 μm.

[0152] For use in fuel cells in vehicles, composite layers having a total thickness in the range of approximately 5 μm to approximately 25 μm have proven to be particularly advantageous. For use in fuel cells in passenger vehicles, composite layers having a total thickness in the range of approximately 5 μm to approximately 10 μm are preferred. For use in fuel cells in trucks, composite layers having a total thickness in the range of approximately 20 μm to approximately 25 μm are preferred.

[0153] For use of the composite layer in an electrolyte cell, the total thickness of the composite layer is preferably selected in the range of approximately 20 μm to approximately 80 μm, in particular in the range of approximately 40 μm to approximately 80 μm.

[0154] For redox flow batteries, composite layers having a total thickness in the range of approximately 20 μm to approximately 50 μm have proven to be particularly advantageous.

[0155] To increase the mechanical stability and / or to increase the proton conductivity or anion conductivity, it can be provided that the composite layer and / or its components are cross-linked.

[0156] It can be provided that molecules from different nanorods bind to one another within the composite layer and thus crosslink the respective nanorods.

[0157] Crosslinking of PBI-based nanorods can take place, for example, thermally or chemically, such as by reaction with a base.

[0158] Preferably one or more crosslinking agents are used, which connect the contact sites of two nanorods to one another.

[0159] Cross-linking is carried out, for example, according to the following reaction:

[0160]

[0161] wherein the curved line represents an aromatic functional group or an alkyl chain, and wherein X is one of the following residues: -Br, -Cl, -CHO, -I.

[0162] The cross-linking of PVDF-based nanorods can be carried out, for example, according to the following reaction:

[0163]

[0164] wherein the curved line represents an aromatic functional group or an alkyl chain, and wherein X is one of the following residues: -Br, -Cl, -CHO, -I.

[0165] The two polymer segments shown in each example belong to two different nanorods. The activation of X can be carried out thermally and / or base-induced.

[0166] As previously illustrated by way of example, polymer molecules of one nanorod in the composite layer are preferably linked to polymer molecules of adjacent nanorods at contact locations. Linking is preferably accomplished via molecules having at least two functional groups that react with the functional groups of the respective nanorods. These molecules are particularly crosslinker molecules.

[0167] For example, electrophilic or nucleophilic substitution reactions occur to connect two or more nanorods.

[0168] Additionally or alternatively to the crosslinking of different nanorods, it can be provided that polymer molecules of the ionomer component form chemical bonds with polymer molecules of one or more nanorods within the composite layer, for example indirectly via a crosslinker, and thus generate crosslinking of the different nanorods.

[0169] The crosslinking is preferably carried out by treatment with electromagnetic radiation in the UV range and / or by chemical methods, in particular by ionic or covalent crosslinking, and / or by thermal methods.

[0170] In order to crosslink two or more nanorods at their contact points by (photo)chemical and / or thermal methods, as has already been described by way of example, one or more crosslinking agents that react with the polymer material of the respective nanorods produced after comminution are preferably added as a component of a precursor solution, for example, before the electrospinning method. These one or more crosslinking agents are a component of the nanofibers produced by the electrospinning method from the nanofiber material.

[0171] After comminuting the nanofiber material containing one or more crosslinking agents, the one or more crosslinking agents are, in particular, components of the resulting nanorods in the absence of further treatment. The one or more crosslinking agents can be activated photochemically and / or thermally after forming the composite layer. For example, a reaction according to the aforementioned examples (in the case of PBI-based nanorods or PVDF-based nanorods) occurs.

[0172] Alternatively, one or more crosslinking agents can react with the nanorods after the composite layer has been formed by immersing the composite layer in a crosslinking agent solution.

[0173] According to a further alternative, the crosslinking agent is incorporated during the application of the nanorod ionomer dispersion and thus produces crosslinking of the nanorods with one another and / or with the polymer molecules of the ionomer component during the formation of the composite layer.

[0174] Suitable crosslinkers for crosslinking PVDF-based nanorods are diamines, triamines or polyamines, in particular primary diamines.

[0175] Suitable crosslinking agents for crosslinking PBI-based nanorods are, for example, dialdehydes, in particular glutaraldehyde, dichloro compounds or dibromo compounds, in particular (α,α′)-dibromo-p-xylene, or diiodo compounds, in particular diiodooctane.

[0176] Diamino compounds can also be used as crosslinking agents.

[0177] The surface region of the substrate on which the composite layer is applied, the surface region of the electrode or the carrier, in particular the surface region carrying the coating, is preferred. In particular, this surface region comprises carbon and / or metal or is essentially formed thereof.

[0178] It can be provided that the composite layer is peeled off from the surface region and / or processed as a separate element. This facilitates roll-to-roll production of at least some of the electrochemical cells. Catalyst layers (such as those used, for example, in fuel cells) are preferably also applied in roll-to-roll production.

[0179] Alternatively, the composite layer according to the invention can also be applied in an electrolyte cell in a so-called roll-to-roll process.

[0180] Different preferred variants for assembling electrochemical cells are described below by way of example in conjunction with fuel cells.

[0181] The term "assembly" is understood to mean the combination or stacking of the individual components of the electrochemical cell.

[0182] Assembly can be performed on one side of the composite layer, i.e. from one side of the composite layer from bottom to top, or on both sides, wherein in the case of two-sided assembly, the composite layer consisting of the material / layer is applied from both sides. Assembly is also part of the present invention.

[0183] Similarly, assembly of one or both sides of electrolyte cells, redox flow batteries, and ion exchangers can also be performed.

[0184] According to a preferred variant of assembling a fuel cell, the composite layer is applied directly to the fuel cell's electrodes. In the case of a fuel cell, the fuel cell's catalyst layers form the electrodes. The catalyst layers are preferably arranged, in particular fixed in a force-locking manner, between the gas diffusion layers. The composite layer is present between the catalyst layers and / or is arranged, in particular in a force-locking manner, between the catalyst layers.

[0185] Carbon substrates comprising a gas diffusion layer have proven to be particularly suitable for use in fuel cells for use in vehicles. The gas diffusion layer is preferably of the "non-woven" type (non-woven).

[0186] The gas diffusion layer is preferably rendered hydrophobic by means of a hydrophobic polymer, such as PTFE. The carbon fibers contained in the gas diffusion layer are preferably covered by a microporous layer. The thickness of the microporous layer, perpendicular to the longitudinal midplane of the composite layer, is preferably in the range of approximately 5 μm to approximately 80 μm. In particular, the microporous layer comprises approximately 5% to approximately 40% by weight of a polymer, such as PTFE, as a binder.

[0187] Depending on the assembly of both sides of the electrochemical cell, the composite layer is applied to the first electrode and the further composite layer is applied to the second electrode. The first and second electrodes are then connected to each other, in particular, by bringing the composite layer and the further composite layer into direct contact with each other.

[0188] Alternatively, it is also possible to assemble the electrochemical cell from one side, in particular from the anode side of the electrochemical cell. One-sided assembly is easier to produce and can be used in a so-called roll-to-roll process. It is also possible to apply multiple components of the electrochemical cell individually in a so-called roll-to-roll process.

[0189] In an embodiment in which the electrochemical cell is a fuel cell, for example, the first catalyst layer can be applied to the first diffusion layer in a first roll-to-roll process. The composite layer can be applied in a so-called second roll-to-roll process. Particularly preferably, the second catalyst layer and the second gas diffusion layer can be applied in a further so-called roll-to-roll process.

[0190] During the aforementioned assembly, the resulting arrangement is preferably held in a force-fitting manner between the first bipolar plate and the second bipolar plate of the fuel cell.

[0191] For this purpose, it can be provided that a membrane, in particular a so-called sacrificial membrane, is used, wherein in particular the catalyst layer is deposited on a carrier membrane.

[0192] Subsequently, a composite layer is applied to the carrier membrane with the catalyst layer. A further catalyst layer is applied and / or deposited onto the composite layer. This results in a combined structure (a so-called "catalyst coated membrane"), which, according to a preferred embodiment, is arranged between two substrates, preferably between two aforementioned gas diffusion layers, each of which has a microporous layer.

[0193] As an alternative to using a carrier membrane, for one-sided assembly of a fuel cell, the composite layer can be applied directly to the electrode (as in two-sided assembly). The electrode function is provided in particular by the first catalyst layer, which is optionally applied to the first microporous layer and the first gas diffusion layer.

[0194] Subsequently, a second catalyst layer is applied to the composite layer. Optionally, a second microporous layer and a second gas diffusion layer are applied to the second catalyst layer.

[0195] According to another preferred two-sided alternative for assembling the electrochemical cell, it can be provided that the composite layer is formed on a carrier film, the carrier film is removed, and the composite layer is subsequently positioned between the first catalyst layer and the second catalyst layer. The first catalyst layer and the second catalyst layer are preferably arranged on the first gas diffusion layer or the second gas diffusion layer. It can be provided that the gas diffusion layer is also arranged on a carrier film, which is removed before the non-positive fastening between the bipolar plates.

[0196] Subsequently, a first gas diffusion layer and a second gas diffusion layer are respectively arranged on the surfaces of the first catalyst layer and the second catalyst layer facing away from the composite layer. Optionally, the first gas diffusion layer and the second gas diffusion layer are respectively provided with a microporous layer.

[0197] In all of the aforementioned variants for assembly, in the assembled state of the chemical cell, a bipolar plate is preferably arranged on the surface of the first and second gas diffusion layers facing away from the composite layer.

[0198] Assembly can preferably take place in a so-called roll-to-roll process.

[0199] The nanorods are preferably distributed homogeneously in the resulting composite layer. In particular, the nanorods are distributed isotropically in all spatial directions of the composite layer.

[0200] Furthermore, the present invention relates to an electrochemical cell comprising a composite layer, wherein the composite layer is produced according to the method according to the invention.

[0201] The advantages and / or features mentioned in conjunction with the method according to the invention also apply to the electrochemical cell.

[0202] Furthermore, the present invention relates to the use of the composite layer according to the invention in fuel cells, in particular hydrogen fuel cells or direct alcohol fuel cells, redox flow batteries, electrolyte batteries or ion exchangers.

[0203] The ion exchanger may be a cation exchanger or an anion exchanger.

[0204] The features and / or advantages mentioned in conjunction with the method according to the invention also apply to the use of the composite layer according to the invention.

[0205] The present invention furthermore relates to the use of the composite layer according to the invention for anion conduction or cation conduction.

[0206] The features and / or advantages mentioned in conjunction with the method according to the invention also apply to the further use of the composite layer according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0207] Further preferred features and / or advantages of the present invention are the subject matter of the following description of exemplary embodiments and the accompanying drawings, in which:

[0208] Figure 1 A schematic diagram illustrating an embodiment of an electrochemical cell is shown;

[0209] Figure 2 A schematic flow chart showing an embodiment of a method for producing a composite layer produced according to the present invention;

[0210] Figure 3 A schematic diagram showing a variation of the assembly of a fuel cell;

[0211] Figure 4 A schematic diagram showing another variation of the assembly of a fuel cell;

[0212] Figure 5 A schematic diagram showing another variant of the assembly of a fuel cell;

[0213] Figure 6shows a scanning electron microscope image of a nanofibrous material composed of PBI nanofibers;

[0214] Figure 7 shows a scanning electron microscope image of a single PBI nanorod;

[0215] Figure 8 shows a scanning electron microscope image of a composite layer composed of approximately 90 weight percent ionomer component and approximately 10 weight percent PBI nanorods;

[0216] Figure 9 shows a scanning electron microscope image of a nanofibrous material composed of nanofibers made from a PBI / PVDF blend;

[0217] Figure 10 shows a scanning electron microscope image of a nanofibrous material composed of nanofibers made of ceria-decorated PBI nanofibers;

[0218] Figure 11 shows a scanning electron microscope image of a nanofibrous material composed of nanofibers made of PVP-cerium nitrate nanofibers;

[0219] Figure 12 shows a scanning electron microscope image of a nanofibrous material composed of nanofibers made of PVP / titanium tetraisopropoxide;

[0220] Figure 13 shows a scanning electron microscope image of a nanofibrous material composed of nanofibers made of ceria / titania / PVP;

[0221] Figure 14 shows a scanning electron microscope image of platinum-coated titanium dioxide nanorods; and

[0222] Figure 15 Shown is a scanning electron microscopy image of cross-linked PBI nanorods. DETAILED DESCRIPTION

[0223] The electrochemical cell 100 in the form of a fuel cell 102 is Figure 1 The fuel cell 102 is used to convert the chemical reaction energy generated when a fuel reacts with an oxidant into electrical energy. Hydrogen, alcohols such as methanol, butane, or natural gas are particularly suitable as fuels.

[0224] Currently, the fuel cells are polymer electrolyte fuel cells, which are low-temperature fuel cells and typically operate at operating temperatures of approximately 60° C. to approximately 120° C.

[0225] Preferably, a plurality of fuel cells 102 are connected in series and form a stack (a so-called "stack").

[0226] The fuel cell 102 includes a first electrode plate 110a configured as a first bipolar plate 112a and a second electrode plate 110b configured as a second bipolar plate 112b. Graphite or metal has proven to be particularly preferred materials for the bipolar plates 112a and 112b. While graphite bipolar plates 112a and 112b are less susceptible to corrosion than metal, metal bipolar plates 112a and 112b are less expensive and therefore more suitable for large-scale technical applications.

[0227] Higher efficiencies are achieved by coating the electrode plates 110a, 112b with a catalyst, such as platinum or palladium.

[0228] Gas channels 114 are arranged parallel to each other within the bipolar plates 112a, 112b, which serve to distribute the fuel supplied in gaseous form. The inner diameter of the gas channels 114 is in the range of approximately 0.5 mm to approximately 1.5 mm, preferably approximately 1 mm.

[0229] The first electrode plate 110 a and the second electrode plate 110 b delimit the fuel cell 102 along a proton conduction direction 115 .

[0230] Arranged between the first electrode plate 110a and the second electrode plate 110b along the proton conduction direction 115 are a first gas diffusion layer 116a, a first microporous layer 118a, a first catalyst layer 120a, a membrane 122, a second catalyst layer 120b, a second microporous layer 118b, and a second gas diffusion layer 116b.

[0231] One or more of the aforementioned layers can each be constructed in a multi-layered manner.

[0232] The fuel cell 102 is designed to be mirror-symmetrical with respect to a plane of symmetry formed by the longitudinal center plane 121 of the membrane 122 .

[0233] The first gas diffusion layer 116a and the second gas diffusion layer 116b have a thickness of approximately 1 μm to approximately 100 μm and can be determined by X-ray diffraction. The gas diffusion layers 116a, 116b are made of carbon fibers (nonwoven) treated with PTFE for hydrophobicity.

[0234] For example, gas diffusion layers 116a, 116b made of non-woven carbon fibers (so-called carbon paper, available as gas diffusion layers according to one of the H14C, H15C, H23C and H24C series from the Freudenberg Group, as a product of SGL Carbon SE) can be used. BC 22, BC 25, BC 29, as GD51120, GD52120, GD522100, GD52240, GD52230, GDS3250, GDS3260, GDS3215 and MB30 and available as Toray paper from Toray Industries, Ltd.), which has, for example, a content of 5% by weight of polytetrafluoroethylene (PTFE).

[0235] According to a preferred embodiment, the gas diffusion layers 116a and 116b are provided with a microporous carbon coating portion (“micro-porous carbon coating”) that forms a first microporous layer 118a and a second microporous layer 118b.

[0236] The gas diffusion layers 116a, 116b act as diffusers for the gas reaching the catalyst layers 120a, 120b. Furthermore, the first and second gas diffusion layers 116a, 116b conduct electrons. Furthermore, the gas diffusion layers 116a, 116b can be used to transfer generated heat to a coolant (not shown).

[0237] It can be provided that, in order to facilitate gas transport, the first and second gas diffusion layers 116 a , 116 b each consist essentially of a layer of plate-like elements, which form a disordered structure.

[0238] The first microporous layer 118a and the second microporous layer 118b have a thickness of about 5 μm to about 80 μm, respectively, and can be characterized by X-ray diffraction. The first microporous layer and the second microporous layer are used to transport reactants of the electrochemical reaction.

[0239] The microporous layers 118a and 118b currently include about 5 weight percent to about 40 weight percent of PTFE, respectively. The first microporous layer 118a and the second microporous layer 118b are currently formed of carbon nanoparticles and a binder.

[0240] Alternatively, the microporous layers 118a, 118b can also be formed with a smaller proportion of PTFE or consist exclusively of carbon nanoparticles.

[0241] The microporous layers 118a, 118b are optional, and the fuel cell 102 may also be constructed without the microporous layers 118a, 118b.

[0242] The catalyst layers 120a, 120b include a material for improving electrical conductivity (currently so-called carbon black nanoparticles), a material for providing proton conductivity (currently ionomer material), and a material for catalytic function (currently platinum nanoparticles).

[0243] The cations formed in the electrochemical reaction (protons in the case of a hydrogen fuel cell) migrate from the cathode to the anode along the proton conduction direction 115 during operation of the fuel cell 102 .

[0244] The cathode and the anode form electrodes, respectively. The anode, on which hydrogen is oxidized, is currently formed by the first catalyst layer 120a.

[0245] The cathode, at which oxygen is reduced, is currently formed by the second catalyst layer 120 b .

[0246] The membrane 122 arranged between the electrodes serves to conduct protons in a proton conduction direction 115. In the present case, the membrane 112 is formed by a composite layer 125 produced according to the invention. Alternatively, it can be provided that the membrane 122 includes further layers in addition to the composite layer 125.

[0247] In the present case, a total thickness 165 of the composite layer 125 perpendicular to the longitudinal center plane 121 is approximately 5 μm to approximately 25 μm.

[0248] Composite layer 125 currently comprises ionomer material 126 into which nanorods 128 (shown schematically) are embedded for mechanical reinforcement and to influence proton conductivity and / or anion conductivity. Ionomer material 126 is formed from an ionomer composition 162 for preparation, discussed subsequently.

[0249] The composite layer 125 may be constructed uniformly along the proton conducting direction 115 or include a plurality of coating layers that are arranged one after another along the proton conducting direction 115. This will be discussed in detail later.

[0250] exist Figure 2 An embodiment of the method for producing a composite layer 125 according to the present invention is shown in the flowchart diagram shown.

[0251] According to a first method step 150 , a nanofiber material 152 is provided.

[0252] According to a preferred embodiment, the nanofiber material 152 is prepared by electrospinning, wherein the precursor solution is injected at an injection rate of about 0.1 μl / min to about 600 μl / min while providing an acceleration voltage in the range of about 5 kV to about 30 kV.

[0253] Preferably, a needleless electrospinning method is used. In the case of a needleless (or also "needleless" or "needle-free") electrospinning method, the nanofiber material 152 is preferably prepared from a free, particularly thin film from a precursor solution on an electrode by providing a high voltage between the electrode and a counter electrode.

[0254] Preferred equipment for performing the needle-free electrospinning process is commercially available from ELMARCO SRO, Liberec XI, 46001, Czech Republic. For example, one of the ELMARCO products NS 851600U, NS 451000U, NS15500U, NS AC150, NS AC1000 or NS AC2000 is used for the needle-free electrospinning process.

[0255] Nanofiber material 152 comprises or consists essentially of nanofibers. The nanofibers preferably comprise oxides, in particular transition metal oxides, or oxides made of rare earths, in particular ceria.

[0256] Alternatively, the nanofibers are formed essentially from oxides, in particular transition metal oxides or oxides made of rare earths, in particular ceria.

[0257] Titanium dioxide and manganese oxide have proven to be particularly suitable as transition metal oxides.

[0258] However, the nanofiber material 152 may also include or consist essentially of nanofibers made from non-metal oxides.

[0259] Additionally or alternatively to oxides, nanofiber material 152 includes, or is formed essentially of, nanofibers composed of a polymer material.

[0260] In order to mechanically stabilize the resulting composite layer 125, nanofibers containing hydrophobic polymers are preferably used in the nanofiber material 152, in particular nanofibers made of one or more of the following polymers: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polybenzimidazole (PBI), polyolefins, such as polyethylene (PE) and polypropylene (PP), and / or polyetheretherketone (PEEK).

[0261] When producing ceramic nanofibers, nanofibers containing a hydrophilic polymer, in particular nanofibers containing polyvinylene pyrrolidone (PVP), are preferably used as an auxiliary in the nanofibrous material 152 .

[0262] The nanofiber material 152 can be optimized to match electrical, optical or thermal properties by supplementing it with additives 155. For this purpose, one or more additives 155 are preferably introduced into the nanofibers of the nanofiber material 152, applied to the nanofibers, or mixed with the nanofibers.

[0263] Suitable additives 155 are granular functional nanoparticles, in particular functional nanoparticles, preferably metal nanoparticles or metal oxide nanoparticles, in particular transition metal oxide nanoparticles or nanoparticles made of rare earth oxides.

[0264] One or more of the following functional nanoparticles have proven to be particularly suitable: palladium nanoparticles, platinum nanoparticles, platinum-cobalt nanoparticles, zirconium phosphate nanoparticles, zeolite nanoparticles, silicon oxide nanoparticles, titanium dioxide nanoparticles, manganese oxide nanoparticles and ceria nanoparticles.

[0265] In addition or as an alternative to granular, in particular nanoparticulate, functional nanoparticles, fibrous functional nanoparticles are suitable additives 155. In this case, fibrous nanoparticles made of the materials described in conjunction with the granular functional nanoparticles are suitable.

[0266] The nanofiber material 152 may include, or consist essentially of, nanofibers coated with platinum or palladium. This coating serves to dissipate hydrogen and oxygen, which parasitically diffuse through the composite layer 125 before reaching the opposing electrode (first catalyst layer 120a or second catalyst layer 120b).

[0267] The nanofiber material 152 provided for producing the composite layer 125 is preferably provided in the form of a fiber body 154. The nanofibers of the nanofiber material 152 form, for example, a fiber mat, a random non-crimp fabric, or a non-woven fabric. This is relevant to the production of the nanofiber material 152.

[0268] When the nanofibrous material 152 is produced by means of an electrospinning method, the nanofibrous material 152 provides a fiber body 154 configured as a random, non-crimped fabric or as a fiber mat.

[0269] As an alternative to the electrospinning method, the nanofibrous material 152 can also be provided by means of a centrifugal spinning method or by means of a solution blown spinning method.

[0270] The rotation speed in the centrifugal spinning method is preferably about 10 rpm to about 6000 rpm.

[0271] In the solution blow spinning method, the injection rate is preferably selected within the range of about 10 μl / min to about 30 μl / min, and the carrier gas flow is adjusted to a pressure of about 100 mPa to about 500 kPa.

[0272] It can be provided that the nanofibrous material 152 is thermally retreated, in particular sintered, before it is subjected to further processing. Water can thus be removed, or an oxidation can also be performed, for example from cerium nitrate to cerium dioxide.

[0273] Nanofiber material 152, in this case fiber body 154, is functionalized by contacting nanofiber material 152 with / in a sulfuric acid or phosphoric acid solution and / or heating it, or by contacting nanofiber material 152 with / in a metal salt solution and / or heating it. When nanofiber material 152 is contacted with sulfuric acid or phosphoric acid solution and / or heated, sulfate groups or phosphate groups are bonded to the surface of nanofiber material 152, thereby increasing the proton conductivity of the resulting composite layer 125.

[0274] When the nanofiber material 152 is in contact with a metal salt solution and / or heated therein, metal ions are bound and / or metal islands are formed on the surface of the nanofiber material 152 , thereby optimizing the conductive properties of the material.

[0275] As metal salt solutions, platinum salt solutions, rhodium salt solutions, palladium salt solutions, ruthenium salt solutions or mixed metal salt solutions, for example platinum-cobalt salt solutions or platinum-nickel salt solutions, have proven particularly suitable.

[0276] Alternatively, it can be provided that the nanofibrous material 152, currently the fiber body 154, is contacted with a potassium hydroxide solution or a sodium hydroxide solution and / or heated therein, thereby increasing the anionic conductivity of the resulting composite layer 125. During the functionalization, protons are preferably bound to the surface of the nanofibrous material 152 via hydroxide ions of the potassium hydroxide solution or the sodium hydroxide solution, thereby forming a positive charge on the surface of the nanofibrous material 152.

[0277] According to an alternative mechanism in composite layer 125 acting as an anion exchanger, hydroxide ions covalently or ionically bind to the polymer molecules of ionomer component 162. Thus, the bound hydroxide ions displace other anions and thus increase the hydroxide conductivity of composite layer 125.

[0278] In a second method step 156, nanofibrous material 152 is comminuted. To this end, nanofibrous material 152 is subjected to mechanical energy. The energy required for comminution is preferably introduced by ultrasonic treatment of nanofibrous material 152. Additionally or alternatively, nanofibrous material 152 can be mechanically comminuted in a mortar and / or ball mill.

[0279] Depending on the material composition of the nanofibrous material 152 , comminution can also take place during and by the aforementioned thermal post-treatment. This is described by way of example in conjunction with Examples 7 and 8.

[0280] When the nanofiber material 152 is comminuted, the nanorods 128 are formed from the nanofiber material 152, wherein the nanofibers of the nanofiber material 152 are separated in the longitudinal direction. The average diameter of the nanofibers remains unchanged when comminuted into the nanorods 128.

[0281] Nanorods 128 have an average diameter of about 20 nm to about 3000 nm, preferably about 50 nm to about 700 nm.

[0282] The average length of the nanorods 128 is about 2 μm to about 500 μm, preferably about 5 μm to about 30 μm.

[0283] The preferred aspect ratio of the nanorods 128 is in the range of approximately 5 to 25,000, and particularly preferably in the range of approximately 10 to approximately 500.

[0284] The average diameter, average length, and aspect ratio were determined from scanning electron microscopy images.

[0285] As already described for the nanofibers, it can be provided that the nanorods 128 are thermally treated, in particular sintered, before further processing. This can be used to remove water or oxidize, for example from cerium nitrate to cerium dioxide.

[0286] Suitable temperatures for thermal retreatment are in the range of about 400°C to about 600°C.

[0287] Instead of nanofiber material 152, nanorods 128 resulting from comminuting nanofiber material 152 can also be functionalized, as described in conjunction with first method step 150. For this purpose, reference is made to the embodiments for functionalizing nanofiber material 152. Functionalization can be performed similarly for nanorods 128.

[0288] In a third method step 158 , the nanorods 128 are dispersed in a liquid medium 160 , wherein the liquid medium 160 is provided in advance. The liquid medium 160 includes an ionomer component 162 and a dispersant 163 .

[0289] Alcohols, alcohol mixtures and alcohol-water mixtures are preferred as dispersants 163. Particularly preferred are methanol, ethanol, 2-propanol or 1-butanol or mixtures of the above alcohols. Alternatively, mixtures of the above alcohols with water can also be used as dispersants 163.

[0290] The ionomer composition 162 is selected based on the desired properties of the composite layer 125 .

[0291] For an optimized proton exchange within the resulting composite layer 125 , fluorinated copolymers having sulfonic acid groups, in particular polyfluorinated copolymers having sulfonic acid groups or perfluorinated copolymers having sulfonic acid groups or mixtures thereof are particularly suitable as ionomer component 162 .

[0292] For example, using PFSA (perfluorosulfonic acid), and The product marketed (respectively) as ionomer component 162 has particularly good properties with regard to proton exchange. Available from EI du Pont de Nemours and Company. Available from Asahi Kasei KK. PSFA is available from 3M Company. Available from Fumatech GmbH. Available from Solvay SA.

[0293] Alternatively, the anion exchange in the resulting composite layer 125 can also be improved by a corresponding selection of the ionomer component 162. This is particularly important when the resulting composite layer 125 is used in an anion exchanger. To this end, the ionomer component 162 preferably includes or essentially consists of one or more non-fluorinated polymers.

[0294] Preferred non-fluorinated polymers are, in particular: hexamethyl-p-terphenyl-poly(benzimidazole), polysulfones, such as polyarylethersulfone, ethylenetetrafluoroethylene copolymers and polyetheretherketone (PEEK).

[0295] The nanorod ionomer dispersion 164 is formed by dispersing the nanorods 128 in the dispersant 163 and by adding the ionomer component 162 before or after dispersing the nanorods 128 in the dispersant 163 .

[0296] The proportion of nanorods 128 in nanorod ionomer dispersion 164 is approximately 1 weight percent to approximately 50 weight percent, relative to the total weight of the dispersion.

[0297] In a fourth method step 166 , the nanorod ionomer dispersion 164 is applied to a surface region 168 of a substrate 169 .

[0298] exist Figure 1 In the embodiment shown, the surface area 168 of the substrate 169 is the surface area of ​​the first catalyst layer and / or the surface area of ​​the respective electrode, or more precisely the surface area of ​​the first catalyst layer 120a and / or the second catalyst layer 120b.

[0299] Combine Figures 3 to 5 The variants for assembly shown in FIG discuss different application possibilities or assembly in detail.

[0300] Alternatively, the nanorod ionomer dispersion 164 can also be applied to a surface area 168 in a redox flow battery or to a surface area 168 of an ion exchanger (anion exchanger or cation exchanger), and the resulting composite layer 125 can be used as an electrochemically active membrane in the redox flow battery or ion exchanger.

[0301] To apply the nanorod ionomer dispersion 164 (fourth method step 166 ), the nanorod ionomer dispersion 164 is applied to a surface region 168 of the substrate in the present case in a print coating method.

[0302] Doctor blade coating is particularly preferred as a printing coating method. Alternatively, however, the nanorod ionomer dispersion 164 can also be applied by means of screen printing, slot printing, inkjet printing, or engraving printing.

[0303] As an alternative to printing coating methods, drop coating or spray coating methods are also suitable for applying the nanorod ionomer dispersion 164 to the surface region 168 of the substrate 169 .

[0304] The nanorod ionomer dispersion 164 may be applied to the surface region 168 in one layer or in multiple layers.

[0305] In embodiments in which multiple layers of nanorod ionomer dispersion 164 are applied, a concentration gradient of nanorods 128 can be created in the resulting composite layer 125. To this end, in different application steps (different layers), nanorod ionomer dispersions 164 are used whose nanorod 128 concentration decreases or increases layer by layer.

[0306] Alternatively, differently coated nanorod ionomer dispersions 164 with nanorods 128 made of different materials can also be used. Due to the different materials of the nanorods 128 , composite layers 125 with different properties can be obtained within the respective composite layer 125 .

[0307] For example, a first coating of nanorod ionomer dispersion 164 having a content of approximately 1 weight percent of platinum-coated titanium dioxide nanorods 128 is applied. Subsequently, a second coating of nanorod ionomer dispersion 164 having a content of approximately 10 weight percent of platinum-coated titanium dioxide nanorods 128 is applied.

[0308] The resulting composite layer 125 then has a coating with a higher proportion of nanorods and a coating with a lower proportion of nanorods 128. The coating of the composite layer 125 with a higher proportion of nanorods is, in particular, more mechanically and thermally stable.

[0309] The multiple coatings are preferably applied by means of a spraying method.

[0310] When applying the nanorod ionomer dispersion 164 in multiple layers, functional intermediate layers can also be integrated in a targeted manner into the composite layer 125 .

[0311] For example, a coating of the nanorod ionomer dispersion 164 comprising ceria nanorods 128 is positioned toward the anode side of the fuel cell 102. Thus, the chemical degradation occurring on the anode side can be influenced.

[0312] According to another exemplary embodiment, a gradient for thermal stabilization with a higher proportion of titanium dioxide nanorods 128 is arranged on the anode side of the fuel cell 102 . This serves to maintain the humidity of the fuel cell 102 .

[0313] According to another exemplary embodiment, the coating with a higher proportion of PBI or DVDF nanorods 128 is arranged toward the cathode side of the fuel cell 102 in order to substantially prevent or reduce swelling there due to cathode-side water production.

[0314] Similarly, functional intermediate coatings and / or concentration gradients can be constructed in composite layers 125 for use in electrolyte cells, redox flow batteries, or ion exchangers.

[0315] The total thickness 165 of the composite layer 125 is typically in the range of approximately 1 μm to 100 μm.

[0316] If already combined Figure 1 As mentioned, for use in a fuel cell 102, in particular in a vehicle (e.g. Figure 1 The total thickness 165 of the composite layer 125 (shown) is preferably about 5 μm to about 25 μm.

[0317] In the composite layer 125 used in the electrolyte cell, the total thickness 165 of the composite layer 125 is preferably in the range of about 20 μm to about 80 μm.

[0318] In the composite layer 125 used in the redox flow battery, the total thickness 165 of the composite layer 125 is preferably in the range of about 20 μm to about 50 μm, respectively.

[0319] Ionomer component 162 is contained in composite layer 125 in a proportion of approximately 80 weight percent to approximately 95 weight percent, relative to the total mass of composite layer 125 .

[0320] According to a fifth method step 170 , the composite layer 125 formed during and / or after application of the nanorod ionomer dispersion 164 is crosslinked.

[0321] exist Figure 15 A scanning electron microscope image of cross-linked nanorods 128 made of PBI is shown in . This will be discussed in detail in conjunction with Example 9.

[0322] As an alternative to PBI nanorods 128, nanorods 128 made of other materials can also be crosslinked. Nanorods 128 made of polymer materials are particularly preferred for crosslinking.

[0323] During crosslinking, molecules of the polymer of one nanorod 128 react chemically with molecules of the polymer of another nanorod 128 , wherein the nanorods 128 must be in spatial contact for crosslinking.

[0324] Additionally or alternatively, a chemical reaction of the molecules of the polymer of the ionomer component 162 with the molecules of the polymer of the ionomer component 162 and / or with the molecules of the polymer of the nanorods 128 occurs.

[0325] The chemical reaction is initiated by thermal treatment and / or treatment with electromagnetic radiation, in particular in the UV range.

[0326] After the composite layer 125 has been formed, crosslinking, in particular covalent bonding, of the different nanorods 128 at the contact points of these nanorods 128 is used to additionally increase the mechanical reinforcement of the composite layer 125 .

[0327] In the case of crosslinking by chemical and / or thermal means, a crosslinking agent that reacts with the material of the respective nanorods 128 is either

[0328] - before the preparation process of the nanofibrous material 152, for example before an electrospinning process; or

[0329] After the composite layer 125 has been formed, for example by immersing the composite layer 125 in a crosslinker solution,

[0330] is provided for reaction.

[0331] According to another alternative, the crosslinking agent may also be added during the application of the nanorod ionomer dispersion 164 to the surface region 168 of the substrate 169 .

[0332] Suitable crosslinking agents for crosslinking the nanorods 128 comprising PVDF are diamines, triamines or polyamines, in particular primary diamines.

[0333] For crosslinking of nanorods 128 comprising or essentially consisting of PBI, for example, dialdehydes, in particular glutaraldehyde, dichloro compounds or dibromo compounds, in particular (α,α′)-dibromo-p-xylene, or diiodo compounds, in particular diiodooctane, for example 1,8-diiodooctane, are suitable as crosslinking agents.

[0334] For example, PBI is introduced into the composite layer 125 in anionic form using alkali metal ions as counterions and is subsequently electrophilically and / or covalently crosslinked via 1,8-diiodooctane.

[0335] Covalent crosslinks between different nanorods 128 can be formed by conversion with 1,8-diaminooctane. For example, 1,8-diaminooctane is used to crosslink PVDF-based nanorods 128.

[0336] According to the invention, there are several variants according to which the electrochemical cell 100 can be assembled.

[0337] Figure 3 A variant for assembling an electrochemical cell 100 in the form of a fuel cell 102 is shown.

[0338] First, an electrode material, in this case the first catalyst layer 120a, is applied to the first gas diffusion layer 116a using an application method, such as spraying. The first gas diffusion layer 116a forms a substrate 202 for the first catalyst layer 120a.

[0339] The first microporous layer 118a (see FIG. 1 ) is disposed between the first gas diffusion layer 116a and the first catalyst layer 120a. Figure 1 ) not shown.

[0340] To apply the electrode material, the first dispensing device 200a is preferably moved over the surface of the first gas diffusion layer 116a. Alternatively, the first dispensing device 200a can be spatially fixed, while the first gas diffusion layer 116a is moved relative to the first dispensing device 200a.

[0341] After forming first catalyst layer 120a on first gas diffusion layer 116a, nanorod ionomer dispersion 164 is applied to surface region 168 of first catalyst layer 120a by means of second application device 200b, in this case by means of a spraying method, thereby forming composite layer 125. In this case, a continuous spraying method is used.

[0342] The arrangement of the first gas diffusion layer 116a and the first catalyst layer 120 (serving as an electrode) forms a substrate 169 for the composite layer. The nanorod ionomer dispersion 164 is now applied to the surface region 168 formed by the first catalyst layer 120a.

[0343] Alternatively to the spraying method, it is also possible to combine Figure 2 The described method applies a nanorod ionomer dispersion 164 .

[0344] The composite layer 125 preferably has one or more bonding Figure 2 Describe the characteristics.

[0345] A first arrangement is produced consisting of a first gas diffusion layer 116a, a first catalyst layer 120a (electrode) and a composite layer 125. A second arrangement identical in production is produced from a second gas diffusion layer 116b, a second catalyst layer 120b (electrode) and another composite layer 125.

[0346] Even when the arrangement in terms of production is identical, the layer thickness can still vary. The layer thickness of the second catalyst layer 120b (cathode) is preferably four times the layer thickness of the first catalyst layer 120a (anode).

[0347] The first arrangement and the second arrangement are connected to one another in such a way that the two composite layers 125 are directly adjacent to one another and are directly connected to one another.

[0348] according to Figure 4 The further variants shown for combining electrochemical cells 100 are firstly (as in Figure 3 In the variant shown, a first catalyst layer 120a is applied to the first gas diffusion layer 116a by means of a first application device 200a.

[0349] Subsequently, the composite layer 125 is constructed by applying, in this case spraying, the nanorod ionomer dispersion 164 onto the first catalyst layer 120a.

[0350] As combined Figure 3 As in the described variant for assembly, the first catalyst layer 120a forms a surface region 168 of a substrate 169. The substrate is formed by the first gas diffusion layer 116a and the first catalyst layer 120a.

[0351] For this purpose, the second dispensing device 200 b is moved relative to the surface region 168 of the substrate 169 formed by the first gas diffusion layer 116 a and the first catalyst layer 120 a .

[0352] After forming the composite layer 125, the second catalyst layer 120b is applied to the composite layer 125 by means of a third applying device 200c moving relative to the surface of the composite layer 125. Subsequently, the second gas diffusion layer 116b is applied to the second catalyst layer 120b and / or fixed thereto.

[0353] Previously described and Figure 4 The variant for assembly schematically shown in FIG is a variant for assembling the electrochemical cell 100 on one side, wherein assembly takes place from one side of the composite layer 125 .

[0354] Figure 5 A further variant for assembling an electrochemical cell 100, in this case a fuel cell 102, is shown. According to this variant, the composite layer 125 is processed separately. This variant is a variant for assembling an electrochemical cell 100 on both sides, assembling from both sides of the composite layer 125.

[0355] On the supporting film 204, the nanorod ionomer dispersion 164 is sprayed onto the surface area 168 of the supporting film 204 by means of a first dispensing device 200a, or by means of another combination Figure 2 The carrier film 204 is here a substrate 169 for the composite layer 125 .

[0356] The carrier film 204 is also called a so-called Decal film. There are different materials suitable as the carrier film 204. For example, a film made of PTFE, PP, PE, glass, and especially Plexiglas can be used. It is particularly preferred to use a film made of or from - A carrier membrane 204 made of fiber-reinforced PTFE from KUNSTSTOFFTECHNIK GMBH & CO.KG.

[0357] The resulting composite layer 125 is then removed from the carrier cover film 204 by peeling.

[0358] Composite layer 125 is then positioned between the first arrangement of first carrier membrane 206a and first catalyst layer 120a and the second arrangement of second carrier membrane 206b and second catalyst layer 120b. Composite layer 125 is positioned directly adjacent to first and second catalyst layers 120a, 120b.

[0359] After the first catalyst layer 120a or the second catalyst layer 120b is connected to the composite layer 125, the first supporting film 206a for the first catalyst layer 120a and the second supporting film 206b for the second catalyst layer 120b are removed from the respective catalyst layers 120a and 120b.

[0360] Subsequently, the first gas diffusion layer 116a and the second gas diffusion layer 116b are applied to the surface of the first catalyst layer 120a or the second catalyst layer 120b facing away from the composite layer 125, respectively.

[0361] Each of the aforementioned variations can be used to prepare Figure 1 The fuel cell 102 is shown. Here, it can be provided that a first microporous layer 118a or a second microporous layer 118b is arranged between the first gas diffusion layer 116a and the first catalyst layer 120a, and between the second gas diffusion layer 116b and the second catalyst layer 120b.

[0362] As an alternative to applying the composite layer 125 to the carrier membranes 206a, 206b provided with the catalyst layers 120a, 120b, the composite layer 125 can also be arranged between the gas diffusion layers 116a, 116b provided with the catalyst layers 120a, 120b.

[0363] The first and second bipolar plates 112a, 112b can be placed on the gas diffusion layers 116a, 116b before carrying out the described variants for assembling the electrochemical cell 100. Alternatively, the first and second bipolar plates 112a, 112b can also be fastened to the first and second gas diffusion layers 120a, 120b according to one of the aforementioned variants for assembling the electrochemical cell 100.

[0364] The following describes, with reference to eight examples, the preparation of nanofiber material 152 and the comminution of the nanofiber material into nanorods 128. Furthermore, the preparation of composite layer 125 is described in Example 1. The crosslinking of nanorods 128 is described as an example with reference to Example 9.

[0365] Room temperature within the meaning of the present invention is understood to be a temperature of approximately 25°C.

[0366] Example 1 -PBI nanofiber

[0367] A precursor solution having about 16 to about 18 weight percent PBI and about 8 to about 9 weight percent lithium chloride in N,N-dimethylacetamide (relative to the total weight of the precursor solution, respectively) was prepared and stirred at about 140° C. for about 24 hours.

[0368] After the precursor solution was cooled to room temperature, the electrospinning process was performed in a controlled environment with a relative humidity of about 30% and a temperature of about 30° C. The distance between the nozzle and the counter electrode was about 15 cm, and the nozzle had a diameter of about 0.6 mm.

[0369] An accelerating voltage of approximately 12 kV was applied between the nozzle and the counter electrode, and the precursor solution was injected through the nozzle at an injection rate of approximately 8 μl / min into the electric field generated by the applied voltage.

[0370] The nanofiber material 152 is deposited on the aluminum film. The aluminum film is positioned on or in front of the counter electrode. After the electrospinning process is completed, the nanofiber material 152, now configured as a fiber mat (fiber body 154), is peeled off from the aluminum film.

[0371] The fiber mat was treated with water at room temperature for approximately 12 hours in order to dissolve the lithium chloride present in the fiber mat. The fiber mat was then dried in vacuo (less than 0.1 mbar, room temperature) for approximately 24 hours.

[0372] Nanofiber material 152 nanofiber Figure 6 The scanning electron microscope images shown show substantially monodisperse nanofibers with diameters ranging from about 0.12 μm to about 0.24 μm. The scanning electron microscope images were taken using a secondary electron detector at an accelerating voltage of about 15 kV.

[0373] Subsequently, PBI nanofiber material 152 was added to a mixture of 2-propanol and deionized water (1:1 volume ratio) to obtain a PBI nanofiber material content of approximately 1 weight percent. The mixture containing PBI nanofiber material 152 was then homogenized in an ice bath using an ultrasonic blast gun with a power of 250 W for approximately 2 hours, thereby generating PBI nanorods 128 from the PBI nanofibers of PBI nanofiber material 152.

[0374] Subsequently, the nanorods 128 composed of PBI are separated from the remaining mixture.

[0375] Figure 7 A scanning electron microscope image of a single nanorod 128, which consists essentially of PBI, is shown. The image was taken with an accelerating voltage of approximately 15 kV and using a secondary electron detector.

[0376] and Figure 6 Compared to the nanofibers of the nanofiber material 152, the nanorods 128 have a significantly reduced length of slightly more than 5 μm. The diameter of the nanorods 128 is approximately 186 nm. Figure 6Compared to the images shown, the comminution occurs along the longitudinal direction.

[0377] Subsequently, nanorods 128 composed of PBI were added to a liquid medium 160 composed of an ionomer component 162 and a dispersant 163 in the form of 2-propanol, with the weight ratio of ionomer component 162 to nanorods 128 adjusted to 9:1, thereby producing a nanorod ionomer dispersion 164 .

[0378] Subsequently, the nanorod ionomer dispersion 164 was applied by ultrasound-assisted spraying to the surface region 168 of the substrate 169. The spraying method was performed using a deposition rate of approximately 0.2 ml / min and an ultrasound power of approximately 3 W at the nozzle.

[0379] Figure 8 The scanning electron microscope image shown in FIG shows a composite layer 125 , which was prepared as previously described. The image was taken at a 45° angle to the surface of the composite layer 125 .

[0380] The composite layer 125 characterized by scanning electron microscopy has a relatively uniform total thickness. Currently, the total thickness of the composite layer 125 is about 10 μm. As can be seen from the scanning electron microscopy image, the nanorods 128 are embedded in the ionomer material formed by the ionomer component.

[0381] As an alternative to spraying, the aforementioned nanorod ionomer dispersion 164 is applied to the surface area 168 by doctor blade coating. For this purpose, the liquid medium 160 preferably comprises 20 weight percent of the ionomer component 162 in a mixture of 2-propanol and deionized water (1:1 volume ratio), relative to the total weight of the liquid medium 160. The weight ratio of the ionomer component 162 to the PBI nanofiber material 152 is 9:1.

[0382] The wet film thickness in the doctor blade coating was set to approximately 50 μm. The resulting total thickness 165 of the composite layer 125 was approximately 11 μm. The proportion of nanorods 128 composed of PBI in the composite layer 125 was approximately 10 weight percent.

[0383] Example 2 -PBI / PVDF nanofibers:

[0384] A precursor solution having approximately 11 weight percent PBI, approximately 11.5 weight percent PVDF, and approximately 5.5 weight percent lithium chloride in N,N-dimethylacetamide (relative to the total weight of the precursor solution, respectively) was prepared and stirred at approximately 160° C. for approximately 24 hours. After cooling to room temperature, the electrospinning process was performed in a controlled environment at a relative humidity of approximately 30% and a temperature of approximately 30° C.

[0385] The distance between the nozzle and the counter-electrode was approximately 15 cm, and the nozzle had a diameter of approximately 0.6 mm. The accelerating voltage provided between the nozzle and the counter-electrode was approximately 18 kV.

[0386] The precursor solution was injected through the nozzle into the electric field generated based on the applied acceleration voltage at an injection rate of about 10 μl / min.

[0387] The produced nanofiber material 152 is deposited on an aluminum coating, which is positioned on or above the counter electrode for this purpose. Alternatively, other substrates can also be used for deposition.

[0388] The nanofiber material 152 is peeled off from the aluminum film using tweezers, for example.

[0389] In the present case, a fiber body 154 in the form of a fiber mat is produced during deposition, which is cleaned by treatment with water at room temperature for approximately 12 hours and subsequently dried in a vacuum, ie, at less than 0.1 mbar and room temperature, for approximately 24 hours.

[0390] In the nanofiber material 152, the nanofiber Figure 9 As can be seen in the scanning electron microscope images shown, substantially monodisperse nanofibers were produced with diameters ranging from about 0.18 μm to about 0.41 μm.

[0391] Alternatively to the aforementioned nanofibers, nanofibers can also be produced from a PBI-PVDF mixture. For this purpose, the precursor solution contains approximately 1.8 weight percent PVDF, approximately 16.2 weight percent PBI, and approximately 8.1 weight percent lithium chloride in N,N-dimethylacetamide.

[0392] The precursor solution is processed into nanofiber material 152 in an electrospinning process using the aforementioned parameters.

[0393] The comminution of the nanofiber material 152 composed of PBI / PVDF may be performed as described in conjunction with the first embodiment.

[0394] Example 3 -Ceria-decorated PBI nanofibers

[0395] A precursor solution having approximately 16 weight percent PBI, approximately 8 weight percent lithium chloride, and approximately 4 weight percent ceria (CeO 2 ) nanoparticles in N,N-dimethylacetamide (relative to the total weight of the precursor solution, respectively) was prepared and stirred for approximately 24 hours at approximately 140° C. The ceria nanoparticles had an average diameter of approximately 25 nm.

[0396] After the precursor solution was cooled to room temperature, the electrospinning process was performed in a controlled environment with a relative humidity of about 30% and a temperature of about 30°C.

[0397] The distance between the nozzle and the counter electrode was about 15 cm, and the diameter of the nozzle was about 0.6 mm. An accelerating voltage of about 12 kV was provided between the nozzle and the counter electrode, and the precursor solution was injected through the nozzle at an injection rate of about 8 μl / min into the electric field generated by the provided accelerating voltage.

[0398] The nanofibers 152 generated here are deposited on the aluminum coating, forming a nanofiber mat 154. The formed nanofiber mat 154 is peeled off from the aluminum coating, cleaned with water (at room temperature) for approximately 12 hours, and then dried in a vacuum (less than 0.1 mbar, room temperature) for approximately 24 hours.

[0399] Figure 10 The scanning electron microscope images shown in FIG show a nanofiber material comprising nanofibers made of PBI, which are decorated with ceria nanoparticles. The images show spherical ceria nanoparticles, which are fixed to the nanofibers. It can be seen that the ceria nanoparticles are still present in particulate form, and that two exemplary nanofibers measured have diameters ranging from approximately 0.29 μm to approximately 0.40 μm.

[0400] Due to the ceria nanoparticles, the resulting composite layer 125 has a higher chemical stability due to the improved radical scavenging properties of the cerium (IV) compound.

[0401] The comminution of the nanofiber material 152 may be performed according to the method described in conjunction with Example 1.

[0402] Example 4 -Cerium dioxide nanoparticles

[0403] A precursor solution having about 17.6 weight percent PVP, about 14 weight percent cerium (III) nitrate hexahydrate in deionized water (relative to the total weight of the precursor solution, respectively) was prepared and stirred at room temperature for about 24 hours.

[0404] Subsequently, the electrospinning process was performed in a controlled environment with a relative humidity of approximately 30% and a temperature of approximately 30°C.

[0405] The distance between the nozzle and the counter-electrode was about 15 cm, and the nozzle had a diameter of about 0.4 mm. An accelerating voltage of about 25 kV was provided between the nozzle and the counter-electrode.

[0406] The precursor solution was injected through the nozzle at an injection rate of approximately 25 μl / min into the electric field generated by the supplied voltage.

[0407] The resulting nanofiber material 152 is deposited on the aluminum coating, wherein in this case a fiber body 154 in the form of a fiber mat is produced.

[0408] In the present case, the nanofiber material 152 is thermally reprocessed in a boiler in air at approximately 500° C. for approximately 6 hours. The PVP used as the supporting polymer is oxidized to volatile or vaporizable products (carbon dioxide, nitrogen oxides, and water). During the thermal reprocessing, cerium (II) nitrate is oxidized to cerium (IV).

[0409] It may be advantageous for the nanofiber material 152 to have fewer nanofiber coatings (particularly less than ten coatings) in order to avoid melting the individual nanofibers during thermal reprocessing.

[0410] The nanofiber material 152 has nanofibers in Figure 11 The scanning electron microscope images shown in FIG. 1 illustrate that nanofibrous material 152 consists essentially of at least approximately monodisperse nanofibers. Two nanofibers measured by way of example have a diameter of approximately 0.37 μm or approximately 0.38 μm. The scanning electron microscope images were taken before the aforementioned thermal post-treatment.

[0411] The nanofiber material 152 was subsequently dispersed in 2-propanol and comminuted by means of ultrasound treatment (ultrasonic blaster power 250 W). The resulting nanorods 128 were distributed on a Petri dish, and the solvent present was evaporated.

[0412] As an alternative to thermal reprocessing before comminution, nanofibrous material 152 can also be comminuted first and then thermally reprocessed.

[0413] For this purpose, the nanorods 128 were thermally further treated in a furnace at approximately 500° C. in air for approximately 6 hours, during which volatile or vaporizable oxidation products of the supporting polymer were again removed and the cerium nitrate was oxidized to cerium dioxide.

[0414] In embodiments where the nanofiber material 152 has been thermally reprocessed, the ceria nanofibers are comminuted as described in connection with the previous examples.

[0415] Since the nanoparticles 128 are made of cerium dioxide, the resulting composite layer 125 can have improved chemical stability due to the radical scavenging properties of the cerium (IV) compound.

[0416] Example 5 -Titanium dioxide nanofibers

[0417] A precursor solution having approximately 9 weight percent of PVP and approximately 9 weight percent of titanium (IV) tetraisopropoxide in a mixture of methanol and glacial acetic acid (methanol to glacial acetic acid ratio of 4:1, respectively, relative to the total weight of the precursor solution) was prepared and treated in an ultrasonic bath at room temperature for approximately 30 minutes and then stirred at room temperature for approximately 2 hours.

[0418] Subsequently, the electrospinning process was performed in a controlled environment with a relative humidity of approximately 30% and a temperature of approximately 30°C.

[0419] The distance between the nozzle and the counter electrode was approximately 15 cm. The nozzle had a diameter of approximately 0.4 mm. An accelerating voltage of 18 kV was applied between the nozzle and the counter electrode.

[0420] The precursor solution was injected through the nozzle into the electric field formed based on the applied acceleration voltage at an injection rate of about 500 μl / h.

[0421] In the present case, a fiber body 154 is produced in the form of a fiber mat, which essentially consists of nanofibers deposited on an aluminum coating.

[0422] The nanofiber material 152 has nanofibers in Figure 12 The scanning electron microscope image shown in illustrates that nanofibers with different diameters are present, but can still be considered as essentially monodisperse overall. Nanofibers with relatively large diameters and nanofibers with relatively small diameters are present. The image shows the nanofibers together with the supporting polymer before thermal retreatment.

[0423] As described in conjunction with Example 4, the nanofiber material 152 can either be thermally reprocessed before it is comminuted into the nanorods 128 , or the comminution can only be performed before the nanorods 128 are thermally reprocessed.

[0424] Thermal retreatment was performed according to the parameters described in conjunction with Example 4.

[0425] Example 6 – Ceria-doped titanium dioxide nanofibers

[0426] A precursor solution having approximately 9 weight percent of PVP, approximately 9 weight percent of titanium (IV) tetraisopropoxide, and approximately 0.9 weight percent of cerium (III) nitrate in a mixture of methanol and glacial acetic acid (methanol to glacial acetic acid ratio of 4:1, respectively, relative to the total weight of the precursor solution) was prepared and treated in an ultrasonic bath at room temperature for approximately 30 minutes and then stirred at room temperature for approximately 2 hours.

[0427] Subsequently, the electrospinning process was performed in a controlled environment with a relative humidity of approximately 30% and a temperature of approximately 30°C.

[0428] The distance between the nozzle and the counter electrode was approximately 15 cm. The nozzle had a diameter of approximately 0.4 mm. An accelerating voltage of 18 kV was applied between the nozzle and the counter electrode.

[0429] The precursor solution was injected through the nozzle into the electric field generated based on the applied acceleration voltage at an injection rate of about 500 μl / h.

[0430] The resulting fiber body 154 is formed in the form of a fiber mat by depositing the nanofibers onto an aluminum coating. The fiber mat is peeled off from the aluminum coating for further processing.

[0431] The nanofiber material 152 has nanofibers in Figure 13 The scanning electron microscope image shown in FIG illustrates that a nanofiber material 152 is produced that includes relatively thick nanofibers having diameters in the range of about 0.44 μm to about 0.68 μm. In addition, relatively thin nanofibers are produced, with diameters of the thin nanofibers being four times or more smaller than the corresponding diameters of the thick nanofibers.

[0432] For thermal retreatment and comminution, reference is made to the previous examples.

[0433] Example 7 – Platinum-coated titanium dioxide nanofibers

[0434] A precursor solution having approximately 9 weight percent of PVP, approximately 9 weight percent of titanium (IV) tetraisopropoxide, and approximately 0.6 weight percent of platinum (II) acetylacetonate in a mixture of methanol and glacial acetic acid (methanol to glacial acetic acid ratio of 4:1, respectively, relative to the total weight of the precursor solution) was prepared and treated in an ultrasonic bath at room temperature for approximately 30 minutes and then stirred at room temperature for approximately 2 hours.

[0435] Subsequently, the electrospinning process was performed in a controlled environment with a relative humidity of approximately 30% and a temperature of approximately 30°C.

[0436] The distance between the nozzle and the counter electrode was about 15 cm. The diameter of the nozzle was about 0.4 mm. An accelerating voltage of about 18 kV was provided between the nozzle and the counter electrode.

[0437] The precursor solution was injected through the nozzle into the electric field generated based on the applied acceleration voltage at an injection rate of about 500 μl / h.

[0438] In the present case, a nanofiber material 152 is produced, which is deposited on an aluminum coating positioned at or on a counter electrode, wherein a fiber body 154, in the present case a fiber mat, is formed. The fiber body 154 is stripped from the aluminum coating for further processing.

[0439] The nanofiber material 152 is thermally retreated in a boiler in the presence of air at approximately 500° C. for approximately 6 hours. During the thermal retreatment, the supporting polymer PVP is oxidized to volatile or vaporizable products (carbon dioxide, nitrogen oxides, and water), and tetraisopropoxytitanium (IV) is oxidized to titanium dioxide.

[0440] Furthermore, platinum in platinum (II) acetylacetonate is reduced from the acetylacetonate ligand to platinum having an oxidation level of 0 (zero) by oxidation.

[0441] Due to the thermal stress in the thermal reprocessing, the nanofiber material 152 has already been pulverized into nanorods 128 during the thermal reprocessing, and thus an additional pulverization step is not required.

[0442] Nanorods 128 Figure 14 The scanning electron microscope image shown in shows that substantially monodisperse nanorods 128 are produced.

[0443] Example 8 – Platinum-coated ceria-doped titania nanofibers having a precursor solution of approximately 9 weight percent PVP, approximately 9 weight percent titanium (IV) tetraisopropoxide, approximately 0.9 weight percent cerium (III) nitrate, and approximately 0.6 weight percent platinum (II) acetylacetonate in a mixture of methanol and glacial acetic acid (methanol to glacial acetic acid volume ratio of 4:1) (relative to the total weight of the precursor solution, respectively) was treated in an ultrasonic bath at room temperature for approximately 30 minutes and then stirred at room temperature for approximately 2 hours.

[0444] The electrospinning process was then performed. With regard to the parameters selected for the electrospinning process, reference is made to Example 7.

[0445] Regarding the thermal re-treatment performed after the nanofiber material 152 is prepared, reference is also made to Example 7.

[0446] As in Example 7, in the case where the nanofibrous material 152 is made of platinum-coated ceria-doped titania nanofibers, comminution of the nanofibrous material 152 into nanorods 128 already occurs during the thermal reprocessing.

[0447] Example 9 - Cross-linked PBI nanorods 128

[0448] The PBI nanorods 128 are dispersed in water to produce a PBI nanorod dispersion of approximately 0.5 weight percent (relative to the total weight of the dispersion). The PBI nanorods 128 can be prepared, for example, according to the method described in Example 1.

[0449] Sodium hydroxide was added to the PBI nanorod dispersion until an approximately 2 molar sodium hydroxide solution was generated. The sodium hydroxide-containing dispersion was stirred at room temperature for approximately 12 hours.

[0450] The dispersion is then dispensed onto a substrate by means of a drop coating method, wherein a film with nanorod junctions is produced. The substrate is selected in such a way that the resulting film with nanorod junctions can be peeled off from the substrate.

[0451] The film with nanorod junctions was peeled from the substrate and immersed in a solution consisting of approximately 10% by weight 1,8-diiodooctane in 2-propanol. The 1,8-diiodooctane solution containing the film with nanorod junctions was heated to approximately 50°C and maintained at approximately 50°C for approximately 24 hours. The nanorods 128 in the film with nanorod junctions were crosslinked, forming crosslinked nanorods 128.

[0452] After the cross-linking is completed, the cross-linked nanorods 128 are washed with water to remove the remaining (unreacted) 1,8-diiodooctane and sodium hydroxide as well as the sodium iodide formed during the cross-linking of the nanorods 128 .

[0453] The resulting cross-linked PBI nanorods 128 are no longer soluble in N,N-dimethylacetamide.

[0454] exist Figure 15 The resulting cross-linked PBI nanorods 128 can be seen in a scanning electron microscope image. As can be seen from the image, the nanorods 128 are cross-linked, thereby creating a more complex nanostructure.

[0455] As an alternative to continuous addition, sodium hydroxide and 1,8-diiodooctane can also be added in a single step, thereby crosslinking the nanorods 128 in situ. The resulting dispersion is heated to approximately 50° C. over approximately 24 hours. Subsequently, the solvent is evaporated, and the crosslinked nanorods 128 are washed with water as described.

[0456] The cross-linked nanorods 128 are no longer soluble in N,N-dimethylacetamide.

Claims

1. A method for preparing a composite layer (125), wherein: The method comprises: - providing a nanofiber material (152), wherein the nanofiber material (152) comprises a hydrophobic polymer selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polybenzimidazole (PBI), polyolefin and / or polyetheretherketone (PEEK); - pulverizing the nanofiber material (152) to form nanorods (128); - providing a liquid medium (160), said liquid medium comprising an ionomer component (162) and a dispersant (163); - dispersing the nanorods (128) in the liquid medium (160) to form a nanorod ionomer dispersion (164); and - applying the nanorod ionomer dispersion (164) to a surface region (168) of a substrate (169) to construct a composite layer (125) as part of a hydrogen fuel cell.

2. The method according to claim 1, characterized in that The nanofiber material (152) is provided by means of an electrospinning method, wherein the injection rate is in the range of 0.1 μl / min to 600 μl / min and / or the acceleration voltage is in the range of 5 kV to 30 kV.

3. The method according to claim 2, characterized in that The electrospinning method is a needle-free electrospinning method.

4. The method according to claim 1, wherein The nanofiber material (152) is provided by means of a centrifugal spinning method, wherein the rotation speed is in the range of 10 rpm to 6000 rpm.

5. The method according to claim 1, wherein The nanofiber material (152) is provided by means of a solution blow spinning method, wherein the injection rate is in the range of 10 μl / min to 30 μl / min, and / or the pressure of the carrier gas flow is in the range of 100 kPa to 500 kPa.

6. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) is provided as a fiber body (154), wherein the fiber body is provided as a random non-crimp fabric and / or a non-woven fabric and / or a fiber mat.

7. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) includes nanofibers having an average diameter of 20 nm to 3000 nm.

8. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) is sintered before being comminuted, or the nanorods (128) are sintered before being dispersed.

9. The method according to any one of claims 1 to 5, characterized in that Applying the nanorod ionomer dispersion is performed by one or more of the following methods: drop coating, print coating method and spray coating method, wherein the print coating method includes doctor blade coating, screen printing, slot printing, engraving printing, inkjet printing.

10. The method according to any one of claims 1 to 5, characterized in that The nanorod ionomer dispersion (164) is applied in multiple layers.

11. The method according to any one of claims 1 to 5, characterized in that The nanorods (128) are contained in the nanorod ionomer dispersion (164) in a proportion of 1 weight percent to 50 weight percent relative to the total weight of the dispersion (164).

12. The method according to any one of claims 1 to 5, characterized in that The ionomer component (162) is contained in the composite layer (125) in a proportion of 80 weight percent to 95 weight percent relative to the total weight of the composite layer (125).

13. The method according to any one of claims 1 to 5, characterized in that The composite layer (125) has a total thickness (165) in the range of 1 μm to 100 μm.

14. The method according to any one of claims 1 to 5, characterized in that The composite layer (125) and / or its components are crosslinked by treatment with electromagnetic radiation in the ultraviolet range and / or by chemical methods and / or by thermal measures, wherein chemical crosslinking includes ionic or covalent crosslinking.

15. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) is functionalized before comminution by contacting the nanofiber material (152) with caustic soda or caustic potash or sulfuric acid or phosphoric acid or a metal salt solution or a mixed metal salt solution, and / or heating the nanofiber material (152) in caustic soda or caustic potash or sulfuric acid or phosphoric acid, or in a metal salt solution or a mixed metal salt solution, wherein the metal salt solution includes a platinum salt solution, a rhodium salt solution, a palladium salt solution, or a ruthenium salt solution.

16. The method according to any one of claims 1 to 5, characterized in that A nanofibrous material (152) in the form of a fiber body (154) is provided, wherein the fiber body includes one or more additives (155), wherein optionally, the one or more additives (155) form an integral part of the nanofibers of the nanofibrous material (152), are applied to the nanofibers, and / or are mixed with the nanofibers.

17. The method according to claim 16, characterized in that The one or more additives (155) include functional nanoparticles in the form of grains and / or fibers.

18. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) is loaded with mechanical energy or thermal energy during comminution, and the nanofiber material (152) is optionally comminuted by means of ultrasonic treatment and / or mechanical comminution.

19. The method according to any one of claims 1 to 5, characterized in that The nanofiber material (152) includes, or is formed essentially of, coated nanofibers.

20. The method according to any one of claims 1 to 5, characterized in that The nanorods (128) have an aspect ratio of an average length to an average diameter of the nanorods (128) in the range of 5 to 25,000.

21. The method according to any one of claims 1 to 5, characterized in that The liquid medium (160) includes one or more of the following materials: a fluorinated copolymer having a sulfonic acid group, and a non-fluorinated polymer, wherein the non-fluorinated polymer includes hexamethyl-p-terphenyl-poly(benzimidazole), polysulfone, ethylene-tetrafluoroethylene copolymer and polyetheretherketone (PEEK).

22. The method according to any one of claims 1 to 5, characterized in that The surface region (168) is a surface region (168) of an electrode (120a, 120b) or a support, wherein the surface region (168) comprises carbon and / or metal or is essentially formed thereof.

23. The method according to any one of claims 1 to 5, characterized in that The composite layer (125) is peeled from the surface region (168) and processed as a separate element.

24. The method according to any one of claims 1 to 5, characterized in that The hydrophobic polymer comprises a polyolefin selected from polyethylene (PE) and / or polypropylene (PP).

25. The method according to claim 7, wherein The nanofiber material (152) includes nanofibers having an average diameter of 50 nm to 700 nm.

26. The method according to claim 13, wherein The composite layer (125) has a total thickness (165) in the range of 5 μm to 25 μm.

27. The method according to claim 13, wherein The composite layer (125) has a total thickness (165) in the range of 20 μm to 80 μm.

28. The method according to claim 15, wherein The nanofiber material (152) is provided in the form of a fiber body (154).

29. The method according to claim 15, wherein The mixed metal salt solution is a platinum-cobalt salt solution or a platinum-nickel salt solution.

30. The method according to claim 17, wherein The functional nanoparticles in the form of crystallites and / or fibers include platinum, palladium, platinum cobalt, zirconium phosphate, zeolite materials, silicon oxide and / or one or more metal oxides.

31. The method according to claim 20, wherein The nanorods (128) have an aspect ratio of an average length to an average diameter of the nanorods (128) in the range of 10 to 500.

32. The method according to claim 20, wherein And the nanorods (128) have an average length of 5 μm to 30 μm.

33. The method according to claim 19, wherein The nanofiber material (152) includes or is formed essentially of noble metal-coated nanofibers.

34. The method according to claim 33, wherein The noble metal is selected from platinum and / or palladium.

35. The method according to claim 20, wherein The nanorods (128) have an average length of 2 μm to 500 μm.

36. The method according to claim 21, wherein The polysulfone is polyarylethersulfone.

37. The method according to claim 22, wherein The carrier is a carrier film (204).

38. The method according to claim 30, wherein The one or more metal oxides are selected from metal oxides of ceria and transition metal oxides, wherein the transition metal oxides include titanium oxide and / or manganese oxide.

39. A hydrogen fuel cell comprising a composite layer, wherein: The composite layer (125) is produced by the method according to any one of claims 1 to 5.

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