Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/0012—Apparatus for achieving spraying before discharge from the apparatus
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/08—Plant for applying liquids or other fluent materials to objects
  • B05B5/081—Plant for applying liquids or other fluent materials to objects specially adapted for treating particulate materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
  • B22F1/054—Nanosized particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/137—Spraying in vacuum or in an inert atmosphere
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/88—Processes of manufacture
  • H01M4/8825—Methods for deposition of the catalytic active composition
  • H01M4/886—Powder spraying, e.g. wet or dry powder spraying, plasma spraying
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/921—Alloys or mixtures with metallic elements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/92—Metals of platinum group
  • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B14/00—Arrangements for collecting, re-using or eliminating excess spraying material
  • B05B14/40—Arrangements for collecting, re-using or eliminating excess spraying material for use in spray booths
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
  • B05B17/0615—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers spray being produced at the free surface of the liquid or other fluent material in a container and subjected to the vibrations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/24—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device
  • B05B7/26—Apparatus in which liquids or other fluent materials from different sources are brought together before entering the discharge device
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M2008/1095—Fuel cells with polymeric electrolytes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the invention relates to a device for precise and uniform application of functional layers comprising metal nanoparticles and polymer electrolyte particles as a binder.
• Such functional layers have some extraordinary properties that make them increasingly used in many different technical and biotechnological fields.
• layers of metal or metal oxide nanoparticles with thicknesses of several tens of micrometers containing polymer electrolyte-type binders can serve as electrodes in electrochemical devices, e.g., hydrogen fuel cells, electrolyzers, electrochemical hydrogen compressors and sensors for detecting the presence of gases.
• the invention further relates to a method of applying the functional layers of catalytic nanomaterials and catalytic layers prepared or obtained using this method.
• a hydrogen fuel cell with a polymer electrolyte membrane is an electrochemical device that allows the direct conversion of the chemical energy of the fuel into electrical energy.
• the use of a solid electrolyte in the form of a polymer membrane enables reliable, long-term, noiseless functioning of the fuel cell in various operating environments and modes of operation.
• the core of a fuel cell is a membrane electrode assembly (MEA) , which typically consists of five layers of materials pressed into a functional unit.
• the central layer is a proton-conducting polymer membrane.
• electrodes On both sides of the membrane, there are electrodes, from which hydrogen oxidation (H 2 ⁇ 2H + + 2e-) takes place at the anode and oxygen reduction (O 2 + 4H + + 4e- ⁇ 2 H 2 O) takes place at the cathode.
• the electrodes consist of two layers, i.e., a diffusion layer made mostly of carbon paper and a catalytic layer containing catalyst nanoparticles to accelerate the above chemical reactions.
• the hydrogen fuel cell catalyst is typically composed of platinum nanoparticles immobilized on nanostructured carbon.
• the catalyst may contain other metallic additives that may increase the catalytic effect of the platinum, or increase the lifetime of the material, or reduce the overall cost of production.
• the catalytic layer forms the transition between the membrane and the diffusion layer, and its optimization in terms of composition and structure is critical for the performance of the fuel cell. It also represents a very significant cost item for the fuel cell due to its precious metal content and the complexity of the production processes.
• CCM catalyst-coated membrane
• GDE gas-diffusion electrode
• catalytic ink is a liquid solution of catalytic nanoparticles, an ion-conducting polymer and an organic solvent.
• the catalytic ink is applied in liquid form to the membrane or diffusion layer and forms a solid catalytic layer several tens of micrometers thick when the solvent evaporates.
• the catalytic layer has a suitable ratio of catalytic nanoparticles, ion-conducting polymer binder and open pores to ensure catalysis and transport of reactants and products of chemical reactions.
• the following methods are currently used for applying the catalytic ink:
• Blade-coating It is a basic method of spreading catalytic ink on a diffusion layer using a controlled feed of a precision razor. The coating of catalytic ink tens to hundreds of micrometers thick is then dried in an oven to form a solid catalytic layer. This basic and simple method is used in laboratory research to produce samples of catalytic layers, but it does not achieve high accuracy in thickness and homogeneity of the resulting layer and precise geometric shapes cannot be achieved .
• Screen printing This method is traditionally used for printing graphics or producing printed electronics. To form a catalytic layer by screen printing, a higher viscosity catalytic ink must be used. The advantage is high printing capacity, homogeneity of the applied layer and dimensional and shape accuracy of the print .
• Inkjet printing It is a non-contact layer application technique using ink droplets with a diameter of 10-100 pm.
• the droplets are generated by a nozzle with an ejection effect induced by a piezoelectric system (piezoelectric crystal) or a heating element.
• the method allows the printing of complex geometric shapes with high precision. It is also possible to produce functionally graded catalytic layers with variable catalyst concentration in the cross-section of the layer. However, the quality of the catalytic ink must be monitored during application to avoid changes in its properties (viscosity, nanoparticle aggregation) over time.
• Additive manufacturing The process of applying catalytic layers can be combined with polymer electrolyte application to form CCM via an additive procedure.
• a first catalytic layer is applied to a carrier film.
• the polymer electrolyte is printed similar to the catalytic layer. It is appropriate to apply the polymer electrolyte in several layers to avoid disturbing the properties of the underlying catalytic layer.
• a second catalytic layer is applied.
• Additive manufacturing provides opportunities to reduce costs for polymer electrolyte, allows to eliminate the occurrence of cracks and defects in individual layers, and reduce the number of underlying films required to form and transfer individual CCM layers. The process of laminating the individual CCM layers is also eliminated.
• the catalytic ink may change its properties in terms of viscosity and agglomeration of the contained nanoparticles during application. After the drying of the ink, inhomogeneity of the catalytic layer may then occur in terms of layer thickness and spatial distribution of the catalyst nanoparticles. In addition, during the drying of the catalytic ink, i.e., the evaporation of the organic solvent, cracks may form in the catalytic layer or delamination may occur at the interface between the catalytic layer and the polymer membrane.
• the spark evaporation method which is described, e.g., in the publication: Nemec T. , Sonsky J. , Gruber J. , Prado E. , Kupcik J. , Klementova M. : Platinum and platinum oxide nanoparticles generated by unipolar spark discharge . Journal of Aerosol Science, 141, 105502, 2019, may be advantageously used.
• the spark evaporation method uses a spark discharge generator to form nanoparticles in a carrier gas. This allows the nanoparticles to be applied by direct deposition on a suitable substrate.
• Synthesis and deposition in the gaseous phase has additional advantages in terms of high purity of the catalytic nanoparticles, high porosity and homogeneity of the applied nanoparticle layer.
• This publication contains a general description of a chamber for performing the spark discharge, but it does not define, for the purpose of generating a functional layer for a hydrogen fuel cell, what filter can be used and how to place it in the deposition chamber, how to filter through it, and what other particles to deposit along with the metal nanoparticles, which is part of the subject matter of the present invention.
• the spark evaporation method enables the generation of mixed nanoparticles or nanoalloys.
• the principle of generating nanoalloys is well-known and straightforward, where electrodes of two different metals are used in the spark evaporation, or mixed electrodes are used, prepared, e.g., by sintering a mixture of metals of the desired composition.
• it is especially alloys of platinum and other metals that may offer advantages over pure platinum.
• a platinum-ruthenium alloy on the anode side of the fuel cell makes it allows to prevent carbon monoxide poisoning (so-called CO poisoning) of the catalyst, or to use lower-quality hydrogen (with a higher carbon monoxide content) as fuel.
• CO poisoning carbon monoxide poisoning
• platinum alloys with transition metals iron, nickel, cobalt
• platinum nanomaterial includes any nanoalloy of platinum with other metallic additives formed by the spark evaporation method.
• a device of the present invention for applying a nanoparticle layer directly from the gaseous phase, wherein the device comprises a first manifold comprising a discharge chamber for generating catalytic nanoparticles and a first flow controller for setting the carrier gas flow in the first manifold, a second manifold comprising a nebuliser for generating droplets of electrolyte aerosol from the polymer electrolyte and a second flow controller for setting the carrier gas flow in the second manifold, furthermore, a deposition chamber and an outlet manifold leading from the deposition chamber, wherein the first manifold and the second manifold are connected and exit into the deposition chamber.
• the deposition chamber is gas-tight sealed and is adapted to fix the substrate for deposition of the functional catalytic layer.
• the flowing cross-section for gas is partially blocked by a transversely oriented plate of porous substrate for deposition of the functional layer reinforced by the diffuser support plate.
• a follow-up technical solution can be used where, in addition to the first and second manifolds, a third manifold is attached at the inlet of the deposition chamber, which contains an additional discharge chamber for generating nanoparticles of another type.
• the above technical solutions can be extended by another element, where in the outlet manifold there is installed an inlet pressure controller which is connected by a data link to a pressure sensor located in the second manifold before the inlet of the deposition chamber.
• the device shown in Fig. 1 consists of four main units block-wise. These are the first manifold 1 with the discharge chamber 15, which is connected to the second manifold 2 with an ultrasonic nebuliser 22 , which exits into the deposition chamber 3, which is connected to the outlet manifold 4.
• the device is shown in detail.
• the first manifold 1 which is typically made of a mechanically strong and chemically resistant material (in particular stainless steel, teflon) , there is installed the first flow controller 11 . This is a standard commercial product used for precise control of carrier gas flow.
• the manifold 1 continues with an inlet into the discharge chamber 15, which houses the metal electrodes, i.e., the cathode 12 and the anode 14 , and based on the known principle of spark evaporation of electrodes, the discharge chamber 15 is the source of the catalytic nanoparticles 16, which are directed by the carrier gas further down the first manifold 1 .
• the second manifold 2 starts in Fig. 2 with an inlet of pressure carrier gas to the second flow controller 21 , which is the same type of controller as the first flow controller 11.
• the second manifold 2 continues with the inlet to the ultrasonic nebuliser 22 , which via a standard ultrasonic activation method generates droplets of the electrolyte aerosol 24 which are directed by the carrier gas down the second manifold 2.
• the two manifolds 1 , 2 are connected together at the inlet to the deposition chamber 3, wherein the carrier gas then contains both the catalytic nanoparticles 16 and the droplets of the electrolyte aerosol 24.
• the deposition chamber 3 is gas-tight sealed and fixes a substrate 33 for deposition of a functional catalytic layer 32.
• the substrate 33 is mechanically supported by a diffuser plate 34.
• an outlet manifold 4 is connected, which is terminated by an opening open to the atmosphere.
• the inlet pressure controller 43 is attached to the outlet manifold 4 and connected to a pressure sensor 41 located at the inlet to the deposition chamber 3, which is connected to the inlet pressure controller 43 via a data link 42.
• a third manifold 5 which is schematically identical to the first manifold 1 and which includes its own second discharge chamber 55.
• the method of deposition is explained according to Fig. 2.
• the first manifold 1 which serves to supply the catalytic nanoparticles 16 to the deposition chamber 3_
• the first flow controller 11 is located, which ensures precise dosing of the carrier gas for transporting the catalytic nanoparticles 16 and depositing them on the substrate 33 in the deposition chamber 3.
• the carrier gas enters the discharge chamber 15, in which catalytic nanoparticles 16 entrained by the flowing carrier gas are generated by spark discharge 13 on the principle of evaporation of metal electrodes, i.e., cathode 12 and anode 14.
• the carrier gas is either of an inert nature (argon) , where pure metal nanoparticles are generated, or the carrier gas contains oxygen, which allows the generation of metal oxide nanoparticles. Furthermore, some metals (such as titanium) can form nitrides etc. with nitrogen.
• the generator of the spark discharge 13 also allows the size and concentration of the generated catalytic nanoparticles 16 to be varied by controlling the energy and repetition rate of the spark discharges 13. Alternatively, by controlling the carrier gas flow, the degree of agglomeration of the catalytic nanoparticles 16 and the degree of their oxidation can be controlled.
• Very small droplets of the electrolyte aerosol 24 are fed into the deposition chamber 3. through the second manifold 2.
• a second flow controller 21 located in the second manifold 2, ensures precise dosing of the carrier gas stream for transporting the droplets of the electrolyte aerosol 24 and depositing them on the substrate 33.
• the carrier gas enters the ultrasonic nebuliser 22 and entrains the droplets of the electrolyte aerosol 24 formed by the solution of polymer electrolyte 23 activated by the ultrasonic source 25.
• the electrolyte 23 both serves as a binder for the applied functional catalytic layer 32 and also provides it with the necessary proton conductivity.
• the carrier gas contains both catalytic nanoparticles 16 and droplets of the electrolyte aerosol 24 in the desired concentrations.
• the deposition chamber 3_ serves to fix and seal the substrate 33 for deposition of the functional catalytic layer 32.
• a typical material for the substrate 33 for use in a low-temperature hydrogen fuel cell is a diffusion layer of porous carbon paper.
• the plate of the substrate 33 acts as a filter on which catalytic nanoparticles 16 and droplets of the electrolyte aerosol 24 from the carrier gas stream 31 are deposited simultaneously by filtration.
• the substrate 33 is mechanically supported by a diffuser plate 34.
• the diffuser plate 34 both provides mechanical support for the substrate 33 during deposition of the functional catalytic layer 32 and also creates sufficient aerodynamic resistance for laminarization and homogenization of the carrier gas stream 31 .
• the diffuser plate 34 is typically composed of a solid porous inert material of the type of sintered metal (e.g., brass) microspheres.
• the outlet manifold _4 connected to the outlet of the deposition chamber 3 conducts the carrier gas from the device into the atmosphere .
• the pressure gradually increases.
• the layer of catalytic nanoparticles 16 deposited on the substrate increases its aerodynamic resistance to the carrier gas flow with its increasing thickness, i.e., pressure loss increases as the carrier gas passes through the functional catalytic layer 32.
• the increasing pressure in the deposition chamber _3 does not necessarily affect the mechanical properties of the deposited layer, however the increasing pressure is also reflected in the discharge chamber 15. This can change the parameters of the spark discharge 13 , as the breakdown voltage of the carrier gas increases at higher pressures, leading to an increase in the energy of the spark discharges 13 and a higher evaporation intensity of the metal electrodes.
• the outlet manifold _4 for conducting the carrier gas from the deposition chamber 3 is equipped with the inlet pressure controller 43 for the pressure control.
• the inlet pressure controller 43 allows the pressure to be increased above the value of atmospheric pressure throughout the entire deposition device.
• the inlet pressure controller 43 can be connected via the data link 42 to the pressure sensor 41 located upstream of the carrier gas inlet to the deposition chamber _3.
• the relative power of the individual generators of the spark discharge 13 is controlled over time, e.g. so as to achieve an increased concentration of one kind of nanoparticles at the beginning of deposition, i.e., in the lower half of the functional catalytic layer 32 , and an increased concentration of another type of nanoparticles at the end of deposition, i.e., in the upper half of the functional catalytic layer 32.
• FIG. 1 shows a block diagram of the technical solution with the main units labeled and fig. 2 showing all the details.
• Fig. 3 shows a block diagram of an embodiment with two independent manifolds for feeding two different types of nanoparticles into the deposition chamber 3.
• the active surface of the membrane electrode assembly (MEA) of a low-temperature hydrogen fuel cell of the PEM type, i.e., with a polymer electrolyte membrane ranges in size from units of cm 2 for laboratory test samples to hundreds of cm 2 for use in high- performance automotive fuel cells.
• the shape of the active surface is usually square or even rectangular and is determined by the design of the fuel cell of which the MEA is a part.
• the substrate 33 in the deposition chamber 3_ consists of carbon paper (e.g., Sigracet GDL 28BC) with a 5 cm 2 square shaped surface.
• the flow of the carrier gas nitrogen, argon, forming gas, etc.
• the repetition rate of the spark discharges 13 is 2 kHz and the energy of the individual spark discharges 13 is 20 mJ. Under these spark synthesis parameters, 2 mg of platinum nanomaterial is produced in 15 minutes.
• the carrier gas flow is set by the second flow controller 21 to the same or a different flow value than the first flow controller 11 (e.g., 0.1 slpm) .
• the carrier gas then passes through a nebuliser, for example the ultrasonic nebuliser 22 , and entrains droplets of the electrolyte aerosol 24 (Nafion solution, e.g., lonPower Liquion) .
• the carrier gas streams from the manifolds 1 and 2 are mixed and thus the platinum nanoparticles and the droplets of the electrolyte aerosol 24 are mixed. These two types of particles suspended in the carrier gas are then simultaneously deposited into the catalytic layer 32 being formed.
• the catalytic layer 32 then has both a homogeneous composition throughout its thickness due to the fact that time- constant parameters of the carrier gas flows through both manifolds 1 and 2, and constant parameters for the generation of platinum nanoparticles, and constant parameters for the operation of the ultrasonic nebuliser 22 were set.
• the catalytic layer 32 has a homogeneous composition over its entire active surface, since it was supported by the diffuser plate 34 during the deposition, ensuring a uniform carrier gas flow over the entire active surface.
• catalytic layer 32 is deposited by first applying the desired amount of platinum nanomaterial in a first step.
• the generator of the spark discharge 13 is started and a non-zero carrier gas flow is set in the first manifold 1 by the first flow controller 11 .
• the ultrasonic nebuliser 22 in the second manifold is turned off, and likewise the second flow controller 21 shuts off the flow of carrier gas in the second manifold 2.
• the ultrasonic nebuliser 22 and the carrier gas flow in the second manifold 2. are turned on in a second step. In this step, only droplets of the electrolyte aerosol 24 are deposited.
• the resulting catalytic layer 32 thus obtains a non- homogeneous structure in a cross-section of its thickness, such that the bottom part is dominated by platinum nanoparticles in a higher concentration than in example 1 and the upper part is dominated by the polymer electrolyte 23.
• the advantage of this deposition method is that the polymer electrolyte 23 forms a solid outer layer of the catalytic layer 32 and fixes the platinum nanoparticles, the layer thereby obtaining more resistance to abrasion during further handling, and in addition obtaining better adhesion to the polymer membrane during MEA pressing.
• the pressure in the deposition chamber 3 increases by 15 kPa within 15 minutes of deposition.
• the pressure increase is caused by the increasing aerodynamic resistance of the deposited catalytic layer 32, which with its increasing thickness exhibits a higher aerodynamic resistance to the passage of the carrier gas.
• the pressure increase may be even higher, e.g., due to the use of the substrate 33 with a lower porosity and therefore higher aerodynamic resistance, or when higher carrier gas flows are set, etc.
• an inlet pressure controller 43 is installed on the outlet manifold 4 which allows the pressure in the bottom half of the deposition chamber _3 to be released during deposition such that the pressure in the upper half of the deposition chamber 32 , and thus in the entire system of the inlet manifolds 1 and 2, remains constant .
• the inlet pressure controller 43 will be set to a value 15 kPa higher than the atmospheric pressure.
• the pressure loss on the deposited catalytic layer 32 increases at a rate of 1 kPa per minute. It is necessary to reduce the pressure value on the input pressure controller 43 by the same value.
• the process of controlling the inlet pressure controller 43 may preferably be automated on the basis of data from a pressure sensor 41 located, e.g., in a manifold before the carrier gas enters to the deposition chamber 3, and connected via the data link 42 to the control of the inlet pressure controller 43.
• catalytic nanoparticles 16 with a diameter of 5 nm will be generated, and at a pressure of 4 atm, the catalytic nanoparticles 16 will have a diameter of 10 nm.
• the inlet pressure controller 43 will therefore be used in this example to continuously linearly increase the pressure during the deposition from a value of 1 atm at the start of deposition to a value of, e.g., 4 atm after 15 minutes of the deposition process.
• the size of the contained catalytic nanoparticles 16 will steadily increase, and the degree of agglomeration of the catalytic nanoparticles 16 will also increase.
• An increase in the performance of the hydrogen fuel cell catalytic layer can be achieved by using another type of nanomaterial deposited at the same time as the platinum catalyst.
• the addition of another nanomaterial typically a metal oxide (TiO 2 , ZrO 2 , etc. ) or even, e.g., a nano-mixture of nitrides and metal oxides such as, e.g., titanium, contributes to the proton conductivity of the catalytic layer .
• This method of deposition is an extension of the procedure of example 1, where another manifold, i.e. , the third manifold 5. with its own second discharge chamber 55, is installed in parallel to the inlet manifolds 1 and 2.
• This second discharge chamber 55 is operated such that the electrode material is composed of titanium and the carrier gas contains a certain proportion of oxygen (air, synthetic air, pure oxygen, etc. ) .
• the generated nanoparticles are then composed of titanium dioxide, or another non-stoichiometric titanium oxide, or a mixture of titanium oxides and nitrides.
• the carrier gas with titanium oxide nanoparticles is mixed with the carrier gas from the first manifold 1 containing the platinum catalytic nanoparticles 16 from the first discharge chamber 15, and also with the carrier gas from the second manifold 2 containing droplets of the electrolyte aerosol 24 before entering the deposition chamber 3_.
• the resulting catalytic layer 32 is then composed of a homogeneous mixture of platinum nanoparticles, titanium oxide nanoparticles, and polymer electrolyte 23.
• the ratio of the concentrations of platinum nanoparticles and titanium oxide nanoparticles is controlled by setting the relative powers (i.e., repetition rates of the spark discharges 13 ) of the two generators of the spark discharge 13 used.
• an additional parallel inlet manifold may be attached to the deposition system to feed additional types of nanoparticles into the deposition cell to form catalytic layers 32 containing three or more kinds of nanoparticles .
• another option for depositing multiple nanomaterials is to deposit the catalytic layer 32 with a variable ratio of individual components varying across the cross-section of the catalytic layer 32.
• the power of the individual generators of the spark discharges 13 must be controlled over time by varying the frequency of the spark discharges 13.
• the preferred solution is a catalytic layer 32 with an increasing ratio of metal oxide (e.g. , titanium oxide from the previous example) towards the upper boundary of the catalytic layer 32.
• metal oxide e.g. , titanium oxide from the previous example
• the density of the metal oxide will increase in the catalytic layer 32 towards its connection with the polymer membrane.
• the local proton conductivity of the catalytic layer 32 towards the connection with the polymer membrane will also increase.
• the linear increase in metal oxide concentration is achieved by controlling the frequency of the generator of the spark discharge 13 in the second discharge chamber 55, where the frequency is linearly increased from an initial (e.g. , zero) value to a target frequency (e.g. , 2 kHz) over 15 minutes of the deposition process.
• the generator of the spark discharge 13 in the first discharge chamber 15 for generating platinum nanoparticles may be operated in a constant- frequency mode in this example. Alternatively, it may be operated in a linear (or non-linear) frequency decrease mode, where the concentration of the platinum nanoparticles in the catalytic layer 32 will decrease towards its upper edge and thus towards the connection with the polymer membrane.
• catalytic layers 32 for PEM-type electrolyzers may be further produced. These devices are similar in design to fuel cells but differ in the materials used for their individual components.
• the substrate 33 for the catalytic layer 32 on the anode of the electrolyzer is not carbon paper, but titanium fabric. This is because carbon structures degrade under electrical potentials during the operation of the electrolyzer and need to be replaced by more resistant materials, e.g., titanium.
• the procedure of producing the catalytic layer 32 for the PEM electrolyzer consists in the use of a substrate 33 in the form of a titanium fabric, e.g., again having a square shaped surface of 5 cm 2 .
• the flow of the carrier gas (forming gas for the case of deposition of pure iridium nanoparticles, or air, or synthetic air, or oxygen for the case of deposition of iridium oxide nanoparticles) is set to the value of example 1, the other setting parameters of the generator of the spark discharge 13 also being maintained. Only the deposition time of the nanoparticles will be approximately 2.5 times longer due to the fact that the target iridium loading for the purpose of electrolysis is around 1 mg/cm 2 .
• a device for applying functional catalytic layers 32 of nanomaterials can be used to produce catalytic layers 32 in the electrodes of a hydrogen fuel cell without the need for using catalytic ink.
• the deposition of the catalytic nanoparticles 16 proceeds directly from the gaseous phase and excels in the purity of the applied nanomaterials and the homogeneity of the applied layer.
• the catalytic layer 32 production process is virtually waste-free and allows a high degree of automation for the series production of hydrogen fuel cells .

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Nanotechnology (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Composite Materials (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Crystallography & Structural Chemistry (AREA)
• Catalysts (AREA)
• Inert Electrodes (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=92075745

Family Applications (1)

Country Status (1)

• 2022
  • 2022-10-24 EP EP22834837.1A patent/EP4420174A1/de active Pending

Similar Documents

Legal Events