Classifications

• • 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
  • H01M4/8605—Porous electrodes
• • 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
  • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
  • H01M4/8668—Binders
• • 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
  • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
  • H01M4/8673—Electrically conductive fillers
• • 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
  • H01M4/8875—Methods for shaping the electrode into free-standing bodies, like sheets, films or grids, e.g. moulding, hot-pressing, casting without support, extrusion without support
• • 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
  • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
• • 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
  • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
• • 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
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
  • H01M8/103—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having nitrogen, e.g. sulfonated polybenzimidazoles [S-PBI], polybenzimidazoles with phosphoric acid, sulfonated polyamides [S-PA] or sulfonated polyphosphazenes [S-PPh]
• • 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
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/1041—Polymer electrolyte composites, mixtures or blends
  • H01M8/1046—Mixtures of at least one polymer and at least one additive
  • H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
• • 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
  • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
• • 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
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
  • H01M8/1027—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having carbon, oxygen and other atoms, e.g. sulfonated polyethersulfones [S-PES]
• • 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
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• Gas diffusion electrodes methods of making gas diffusion electrodes and fuel cells using such gas diffusion electrodes.
• the invention relates to gas diffusion electrodes with a plurality of gas-permeable, electrically conductive layers, a method for producing gas diffusion electrodes and fuel cells for service temperatures up to at least 200 0 C and the membrane Elelctroden units using such gas diffusion electrodes.
• US Pat. No. 4,876,115 describes a gas diffusion electrode for membrane electrode assemblies with polymer electrolyte membranes and a method for their production, which are used in fuel cells.
• the gas diffusion electrode is composed of a gas diffusion layer and a gas permeable catalyst layer which is in contact with a solid polymer electrolyte membrane.
• the gas-permeable catalyst layer consists of particles of an electrically conductive carrier material, on the surface of which a catalyst material is dispersed. The interstices formed by the particles allow the reaction gases to penetrate through the electrode structure to the adjacent catalysts where the electrochemical reactions take place.
• additional particles are present, for example made of PTFE.
• a proton conductive material is sprayed, deposited, or painted onto the catalyst layer to provide better conduction of the protons between the catalyst particles and the polymer electrolyte membrane.
• proton-conductive material Nafion ® and ruthenium dioxide is proposed.
• the disadvantage is that the applied Nafion ® has a low porosity and gas permeability, whereby at too high a dosage of Nafion ® blocks the gas permeability of the catalyst layer or at least considerably is lowered. Therefore, Nafion ® must be sprayed on in several layers.
• the catalyst particles which are not on the surface of the catalyst layer, not or insufficiently contacted by the Nafion ® .
• Nafion ® can not be used as a membrane or as a proton-conducting electrode component for the gas diffusion electrode in high-temperature polymer electrolyte membrane fuel cells that operate up to an operating temperature of at least 200 ° C, since Nafion ® in continuous operation at temperatures above 100 ° C is unstable.
• this means on the one hand impairing the gas permeability by sintering together the electrode structure, and on the other hand leads to the elimination of sulfonic acid groups at temperatures> 100 ° C to a loss of proton-conducting properties.
• gas diffusion electrodes are produced by applying a paste or suspension of a catalyst powder in a solution of polybenzimidazole (PBI) in dimethylacetamide (DMAc) to a gas diffusion layer and producing a solid layer by removal of the solvent.
• the electrode layer is impregnated with phosphoric acid to achieve proton conductivity by doping the polymer with the acid while immobilizing the acid.
• PBI polybenzimidazole
• DMAc dimethylacetamide
• the disadvantage is that the PBI layers produced from a solution of the polymer in dimethylacetamide by removal of the solvent constitute dense films. Since the polymer is uniformly distributed throughout the active electrode layer due to the manufacturing procedure described, the gas permeability of the electrode is greatly reduced and the accessibility of the catalyst for the reaction gases is reduced. simultaneously but also the removal of product water is hindered. Thus, the phosphoric acid-doped PBI intensely comes into contact with the product water, which can stir up a discharge of phosphoric acid and result in a decrease in proton
• the object of the invention is therefore to propose gas diffusion electrodes for fuel cells with an improved, independent of the operating conditions proton conduction between a located in a catalyst layer electrocatalyst and an adjacent polymer electrolyte membrane, which can be used at operating temperatures above the boiling point of water and a permanently high gas permeability ensure the catalyst layer.
• Other objects of the invention are to propose methods for the effective production of such gas diffusion electrodes and fuel cells for operating temperatures above the boiling point of water using these gas diffusion electrodes.
• gas diffusion electrodes having a plurality of gas-permeable, electrically conductive layers, which consist of at least one gas diffusion layer and one catalyst layer.
• the catalyst layer has at least particles of an electrically conductive carrier material. At least a portion of the particles carries a Elelctrokatalysator, which is preferably located on the surface of the particles. At least some of the particles are at least partially loaded with at least one porous, proton-conducting polymer. This porous proton-conducting polymer can be used at temperatures above the boiling point of water and / or stable up to at least 200 ° C.
• the loading of the surface of the particles of the electrically conductive carrier material with a proton-conducting polymer having a porous structure offers the great advantage that a good proton conduction is realized between the electrocatalyst in the catalyst layer and an adjacent polymer electrolyte membrane, because at corresponding concentrations of the loaded Particles is high probability that the proton-conducting polymer layer of a particle in the catalyst layer is directly in contact with the proton-conducting polymer layer of an adjacent particle in the catalyst layer or with the polymer electrolyte membrane in a membrane electrode unit (MEA) of a fuel cell.
• MEA membrane electrode unit
• the stable to at least 200 0 C porosity of the proton-conducting polymer layer not only ensures a high gas permeability of the catalyst layer, but also an unimpeded transport of the gaseous fuels and oxidants and the gaseous reaction products to the electrocatalysts and from these on.
• the porosity of the proton-conducting polymer layer can be adjusted at least in the range of about 0.001 to 0.1 ⁇ m pore diameter.
• the proportion of the loading of the surface of the particles and the thickness of the load are also adjustable.
• the thickness of the particle coating is 0.1 to 10% of the particle diameter and preferably 50 to 100% of the surface of the particles are loaded.
• the gas diffusion electrodes according to the invention can be used in so-called high-temperature fuel cells which operate at temperatures up to above Boiling point of water and / or at least 200 0 C without loss of power in continuous operation. This is attributed to the fact that the porous structure of the selected proton-conducting polymers does not collapse at these temperatures and thus preserves the structural structure of the gas diffusion electrodes.
• Proton-conducting polymers are to be understood as meaning those which are per se proton-conducting or capable of proton conduction, for example by incorporation of a doping agent, such as, for example, a strong inorganic acid.
• the catalyst layer additionally comprises porous particles which consist of at least the porous proton-conducting polymer.
• These electrically conductive Particles are preferably made of soot. This achieves a better electron conduction and a more uniform gas distribution in the gas diffusion electrodes.
• the gas diffusion layers of the gas diffusion electrodes are usually made of carbon, in particular in the form of carbon fibers, which are processed into paper, nonwovens, mesh, knitted or woven fabrics.
• the electrically conductive support material of the catalyst layer is selected from the group of metals, metal oxides, metal carbides, carbons or mixtures thereof.
• particulate carbon black is selected from carbons. Particularly suitable are those which are known under the designations carbon black, such as Vulcan XC or Shawinigan Black and furthermore spherical graphitized carbon blacks or Mesocarbon microbeads.
• the electrocatalysts used are metals and metal alloys or mixtures thereof. Metals which are selected from the 8th subgroup of the Periodic Table of the Elements have proved particularly useful. Of these, platinum, iridium and / or ruthenium are preferred. Particularly preferred is platinum.
• the loading is preferably 5 to 40 wt .-% electrocatalyst on the support.
• the catalyst particles should have a size of about 2 to 10 nm.
• the at least one porous, proton-conducting polymer consists of at least one polymer containing nitrogen atoms whose nitrogen atoms are chemically bonded to central atoms of polybasic inorganic oxo acids or derivatives thereof.
• n XO m Under polybasic inorganic oxo acids (Cotton, Wilkinson, Inorganic Chemistry, Verlag Chemie, Weinheim, Deerfeld Beach, Florida, Basel 1982, 4th edition, pp 238-239) acids with the general formula H n XO m are to be understood, in which n> l, m> 2 and n ⁇ m and X is an inorganic central atom (n and m are integers).
• the central atom is phosphorus, sulfur, molybdenum, tungsten, arsenic, antimony, bismuth, selenium, germanium, tin, lead, boron, chromium or silicon.
• phosphorus Preference is given to phosphorus, molybdenum, tungsten and silicon, and phosphorus is particularly preferred.
• organic derivatives of the oxo acids organic derivatives in the form of alkoxy compounds, esters, amides and acid chlorides are preferred.
• organic derivatives of oxo acids are di (2- ethylhexyl) phosphoric acid ester, molybdenyl acetylacetonate and tetraethoxysilane are particularly preferred.
• the nitrogen-containing polymer is selected from the group comprising polybenzimidazoles, polypyrridines, polypyrimidines. Polyimidazoles, polybenzothiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles,
• the nitrogen-containing polymer should be mechanically and thermally stable and have a glass transition above 200 ° C.
• the mentioned proton-conducting polymers which contain covalently bonded units of oxo acids, per se do not have sufficient proton-conducting properties that would be sufficient for use in gas diffusion electrodes.
• these polymers can excellently absorb and fix dopants, such as, for example, phosphoric acid.
• dopant remains fixed not only at temperatures up to at least 200 ° C., but also at temperatures below 100 ° C., so strongly in the polymers used according to the invention, that it is not discharged from the gas diffusion electrodes even in the start and stop region of fuel cells.
• the proton-conducting polymers have a higher hydrophobicity compared to conventional polybenzimidazoles, which means that they do not absorb the product water of the fuel cell, whereby the discharge of phosphoric acid is prevented, or at least greatly reduced.
• the at least one proton-conducting polymer can be adjusted in its affinity for water on the nature and number of hydrophilic and hydrophobic groups which are introduced into the polymers and / or in the derivatives of oxo acids. Such reactions are familiar to the person skilled in the art. It has proved to be advantageous if the at least one proton-conducting polymer and the central atom of the oxo acid or of the oxo acid derivative are crosslinked to form a network.
• the crosslinked polymer coating has an increased mechanical stability and stabilizes the particles coated therewith and the structure formed with these particles. Furthermore, the crosslinked polymer coating is particularly well-suited for receiving dopants, such as phosphoric acid, with the formation of excellent proton-conducting properties.
• the network is formed at least two-dimensionally, but preferably three-dimensionally, in particular with a small proportion of the oxo acid units with respect to the polymer.
• Particularly suitable proton-conducting polymers for use in the gas diffusion electrodes have a degree of crosslinking of at least 70% of the polymer, preferably of more than 80%, particularly preferably of more than 90%.
• the particles of the electrically conductive carrier material are loaded with various porous, proton-conducting polymers.
• the part of the particles of the electrically conductive support material which carries an elite catalyst is loaded with a different, porous, proton-conducting polymer than the part of the particles without elctrocatalyst.
• the coating of the catalyst-containing support material has by the covalently bound oxo acid derivative used itself catalytic activity or supports the Elelctrokatalysator in its function.
• Gas diffusion electrodes according to the invention may additionally contain additives in the catalyst layer.
• additives include, for example, binders such as perfluoropolymers or particles of stress-promoting additives, such as carbon-based spherical particles.
• the object of the invention is further achieved by a method for producing gas diffusion electrodes having a plurality of gas-permeable, electrically conductive
• Layers which consist of at least one gas diffusion layer and a catalyst layer, wherein the catalyst layer at least particles of an electrically conductive
• Boiling point of water and / or to at least 200 0 C is stable.
• the following steps are carried out: A) The surface of at least the one part of the particles of the electrically conductive carrier material is at least partially loaded with at least one proton-conducting polymer.
• the particles are suspended in a liquid in which the at least one proton-conducting polymer is dissolved.
• the suspension is successively introduced into a moving nonsolvent for the polymer, wherein phase inversion is induced to form a porous polymer structure on the surface of the particles of the carrier material and of porous particles of the at least one proton-conducting polymer;
• Suitable liquids are agents in which the polymers dissolve.
• NMP N-methylpyrrolidone
• DMF dimethylformamide
• DMSO dimethylsulfoxide
• DMAc dimethylacetamide
• concentration of the at least one polymer in the suspension is in the range of 0.05 to 5 wt .-%, particularly preferably from 0.1 and 1 wt .-%.
• the content of the particles of the electrically conductive carrier material in the suspension is adjusted in the range of 5 to 30 wt .-% and particularly preferably from 10 and 15 wt .-%.
• the suspension further contains the neutralized derivative of an oxo acid in a concentration in the range of 0.01 and 0.5 wt .-%, particularly preferably from 0.1 and 0.3 wt .-%.
• the polymer in the suspension thus come between about 10 and 400 wt .-% Oxoklarederivat, more preferably in the range of 200 and 350 wt .-%.
• the suspension contains additional crosslinker molecules or a catalyst.
• the concentration of the additional crosslinker molecules is between about 1 to 10 wt .-% based on the polymer, more preferably is a range of 2 to 5 wt .-%.
• the concentration of the catalyst is in the range of 0.1 and 5 wt .-% based on the polymer, more preferably in the range of 0.5 and 2 wt .-%.
• the suspension contains pore-forming additives.
• the suspension is prepared by successively adding the electrically conductive carrier material and the partially dissolved in the solvent formulation ingredients to the polymer solution and stirred for about 30 minutes, preferably at room temperature.
• the non-solvent used is preferably water.
• the non-solvent may also contain additives that affect particle formation and pore formation during the phase inversion process.
• the suspension is introduced into the non-solvent, the latter is intensively stirred in order to achieve a high distribution of the suspension constituents and to prevent sticking of the particles.
• the suspension is preferably introduced into the non-solvent at room temperature.
• the product of suspension and non-solvent is stirred for about one hour at temperatures in the range of 50 and 100 ° C, preferably 80 and 95 ° C.
• a drying step is connected to the process according to the invention.
• the drying takes place by means of a process known to the expert for powder drying, in the simplest case at temperatures in the range of 50 and 200 ° C, more preferably at temperatures in the range of 80 and 150 ° C over a period of about 24 hours in a drying oven.
• the powder drying can also be done by freeze-drying to achieve a particularly fine-grained powder.
• the diameter of the pores in the proton-conducting polymer layer can be adjusted in the range of about 1 ⁇ m to 1 ⁇ m in which certain parameters of the layer-producing phase inversion process, such as concentration of the polymer in the suspension, type of oxo acid derivative used, addition of pore formers and composition of the precipitation bath are changed.
• the proportion of the loading of the surface of the particles and the thickness of the charge can in particular be adjusted by the concentration of the proton-conducting polymer in the suspension from which the porous polymer layer is produced in the phase inversion process.
• the layer thickness of the polymer with which the particles are loaded is less than 1 ⁇ m.
• the electrocatalyst can be distributed in the catalyst layer of the gas diffusion electrode in such a way that the electrocatalyst is connected to the polyelectrolyte membrane in proton-conducting fashion but is not coated so comprehensively with the proton-conducting polymer that it does is impaired in its function.
• additives are added to the provided carrier material before carrying out step C). Suitable additives are binders, such as perfluoropolymers and structure-forming additives, such as additional spherical carbon particles or pore formers.
• the forming of the catalyst layer into the electrode form can preferably be carried out by rolling the powder.
• the use of the polymer-coated carrier material according to the invention is advantageous since it leads to a significant improvement in the mechanical stability of the shaped electrode strip.
• the catalyst layer is preferably formed into the electrodeposit mold by applying the suspension or the paste to at least one support and then drying.
• the use of the polymer-coated carrier material according to the invention is advantageous, since this is much more suspendable than uncoated carrier material.
• both the gas diffusion layer and the membrane may be used as a support.
• the contacting of the catalyst layer with the gas diffusion layer (D) takes place during the shaping of the catalyst layer.
• the catalyst layer located on the membrane is contacted with the gas diffusion layer.
• the shaped catalyst layer alone, or the composite of catalyst layer and gas diffusion layer can be tempered again before further use in order to stabilize the composite or to heat out pore formers. It has proven advantageous if an additional gas-distributing microstructure layer of electrically conductive particles is applied to the side of the gas diffusion layer which is brought into contact with the catalyst layer.
• the polymers used as proton-conducting polymers in step (A) are those comprising at least one polymer containing nitrogen atoms whose nitrogen atoms are chemically bonded to central atoms of polybasic inorganic oxo acids or derivatives thereof.
• the reaction between the polymer and the oxo acid or its derivative takes place during the course of step A.
• polymers containing nitrogen atoms are those polymers selected from the group consisting of polybenzimidazole (PBI), polypyrridine, polypyrimidine, polyimidazoles, polybenzothiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles, poly (tetrazapyrene), or wherein the polymers are used to form Amide bonds capable of bearing reactive groups in the Seitehkette or have primary and secondary amino groups and a combination of two or more thereof or with other polymers.
• PBI polybenzimidazole
• polypyrridine polypyrimidine
• polyimidazoles polybenzothiazoles
• polybenzoxazoles polyoxadiazoles
• polyquinoxalines polyquinoxalines
• polythiadiazoles poly (tetrazapyrene)
• oxo acids or their derivatives are used whose central atom consists of phosphorus, sulfur, molybdenum, tungsten, arsenic, antimony, bismuth, selenium, germanium, tin, lead, boron, chromium and / or silicon.
• organic derivatives in the form of alkoxy compounds, esters, amides and acid chlorides are preferred.
• 2- (diethylhexyl) phosphoric acid esters, molybdenyl acetylacetonate and tetraethoxysilane is set in a range of 10 to 400% by weight, more preferably in a range of 200 to 350% by weight, based on the content of the nitrogen atom-containing polymer.
• the particles of the carrier material are loaded with a polymer of PBI and 2- (diethylhexyl) phosphate ester.
• a PBI is selected whose solution of 1 wt .-% in DMAc has an intrinsic viscosity or intrinsic viscosity at 25 ° C of 0.90 dl / g or higher.
• the intrinsic viscosity results in an average molar mass of 60,000 g / mol and higher using the Mark-Houwink relationship.
• a PBI with molecular weights in the range from 35,000 to 100,000 g / mol is used according to the invention.
• the polymer-coated electrically conductive support material is cured at temperatures in the range from 100 to 300 ° C., preferably in the range from 150 to 250 ° C., for about 1 hour, in order to crosslink the polymer with the oxo acid derivative to complete.
• the annealing temperature it may be necessary to extend the annealing process to up to about 5 hours.
• the mechanical stability of the polymer coating on the particles of the electrically conductive carrier material can be influenced by the type of oxo acid derivative used and its concentration.
• the at least one proton-conducting polymer is adjusted in its affinity for water via the type and number of hydrophilic and hydrophobic groups on the polymers and / or on the derivatives of the oxo acids.
• the object of the invention is further achieved by fuel cells, which consist of at least one membrane electrode unit (MEA), which consists of two flat gas diffusion electrodes according to the invention and a sandwich interposed membrane are joined together and from a dopant for the membrane.
• MEA membrane electrode unit
• the gas diffusion electrodes according to the invention have a plurality of gas-permeable, electrically conductive layers which comprise at least one gas diffusion layer and one catalyst layer, wherein the catalyst layer comprises at least particles of an electrically conductive support material, and at least a part of the particles carries an electrocatalyst and / or at least partially with at least one porous, proton-conducting polymers is loaded and this polymer is used at temperatures above the boiling point of water and / or is stable to at least 200 0 C.
• the gas diffusion electrodes are loaded with the dopant such that they represent a dopant reservoir for the membrane, wherein the membrane has become proton conductive by receiving the dopant under the action of pressure and temperature and is connected proton-conducting to the gas distribution electrodes.
• the dopant used is preferably phosphoric acid.
• the fuel cell can be operated at operating temperatures between room temperature and above the boiling point of water and / or up to at least 200 ° C in the hydrogen / air mode.
• the gas diffusion electrodes and the polymer electrolyte membrane of the MEA have the same at least one proton-conducting polymer.
• example 2 shows the course of a current-voltage curve for a further embodiment of a fuel cell according to the invention.
• example 1
• the resulting suspension (slurry), again with stirring, heated to 100 ° C for about 1 hour, then cooled to about 50 ° C and filtered.
• the filtrate is dried at 100 ° C overnight in a drying oven and then passed through a sieve with 50 microns mesh size.
• the now coated with a porous PBI particles are annealed at 200 ° C for one hour in an oven under an inert gas atmosphere.
• the resulting suspension (slurry), again with stirring, heated to 100 0 C for about 1 hour, then cooled to about 50 ° C and filtered.
• the filtrate is added 100 0 C dried overnight in a drying oven and then passed through a sieve with 50 microns mesh size.
• the now coated with a porous PBI carbon black is annealed at 200 0 C for one hour in an oven under inert gas atmosphere.
• Example 3 Production of gas diffusion electrodes with an electrically conductive carrier material obtained according to example 1 by a suspension process.
• Example 4 Production of gas diffusion electrodes with an electrically conductive carrier material obtained according to Example 2 by a suspension process.
• Example 3 For the preparation of an MEA, two 10 cm 2 square pieces are punched from the gas diffusion electrodes according to Example 3 and impregnated with 13 mg of concentrated phosphoric acid. The two impregnated with phosphoric acid gas diffusion electrodes are placed centrally over their catalyst layer on a 56.25 cm 2 square piece of a 35 micron thick polymer electrolyte membrane of PBI. The membrane-electrode sandwich is pressed for 2 hours at 160 ° C with a contact pressure of 3 IdST to an MEA. The obtained MEA can be installed in fuel cells.
• Example 6 Preparation of Membrane Electrode Units (MEA) with the Gas Diffusion Electrodes of Example 4
• Example 7 For the production of an MEA, two 10 cm 2 square pieces are punched from the gas diffusion electrodes according to Example 4 and impregnated with 17 mg of concentrated phosphoric acid. The impregnated with phosphoric acid gas diffusion electrodes are applied centrally over their catalyst layer on a 56.25 cm 2 square piece of a 35 micron thick polyelectrolyte membrane of PBI. The membrane-electrode sandwich is pressed for 2 hours at 160 ° C with a contact pressure of 3 kN to an MEA. The obtained MEA can be installed in fuel cells.
• Example 7 Example 7
• the MEA produced according to Example 5 is installed in a test fuel cell of Fuel Cell Technology, Inc. and sealed with a contact pressure of 15 bar.
• Fig. 1 the course of a current-voltage curve for the fuel cell at an operating temperature of 16O 0 C is shown.
• the gas flow for H 2 was 180 sml / min and for air 580 sml / min. Unhumidified gases were used.
• Performance parameters were determined on a FCATS Advanced Screener from Hydrogenics, Inc. When maximum power at 4 bar absolute was W / cm 2 at a current density of 0.6 A / cm 2 measured 0.25.
• the cell impedance was 0.5 ⁇ cm 2 .
• Example 8 Determining the Performance Parameters of a Fuel Cell with an MEA Produced According to Example 6.
• the MEA produced according to Example 6 is installed in a test fuel cell of Fuel Cell Technology, Inc. and sealed with a contact pressure of 15 bar.
• Fig. 2 the course of a current-voltage curve for the fuel cell at a working temperature of 16O 0 C is shown.
• the H 2 gas flow was 180 mL / min and air 580 mL / min. Unhumidified gases were used.
• Performance parameters were determined on a FCATS Advanced Screener from Hydrogenics, Inc. When maximum power at 4 bar absolute were W / cm 2 at a current density of 0.95 A / cm 2 measured 0.39.
• the cell impedance was 0.3 ⁇ cm 2 .

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