DE102012011441A1 - Membrane electrode unit for a fuel cell - Google Patents

Membrane electrode unit for a fuel cell

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Publication number
DE102012011441A1
DE102012011441A1 DE102012011441A DE102012011441A DE102012011441A1 DE 102012011441 A1 DE102012011441 A1 DE 102012011441A1 DE 102012011441 A DE102012011441 A DE 102012011441A DE 102012011441 A DE102012011441 A DE 102012011441A DE 102012011441 A1 DE102012011441 A1 DE 102012011441A1
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Germany
Prior art keywords
membrane
fuel cell
cathode
anode
electrode assembly
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Pending
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DE102012011441A
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German (de)
Inventor
Nils Brandau
Sven Schmitz
Mathias Purmann
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Audi AG
Original Assignee
Volkswagen AG
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Publication date
Priority to DE102011106418 priority Critical
Priority to DE102011106418.8 priority
Application filed by Volkswagen AG filed Critical Volkswagen AG
Priority to DE102012011441A priority patent/DE102012011441A1/en
Publication of DE102012011441A1 publication Critical patent/DE102012011441A1/en
Application status is Pending legal-status Critical

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/04Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H01M8/04156Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal
    • H01M8/04171Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal using adsorbents, wicks or hydrophilic material
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/02Details
    • H01M8/0271Sealing or supporting means around electrodes, matrices or membranes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/04Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H01M8/04126Humidifying
    • H01M8/04149Humidifying by diffusion, e.g. making use of membranes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1004Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/20Fuel cells in motive systems, e.g. vehicle, ship, plane
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/50Fuel cells
    • Y02E60/52Fuel cells characterised by type or design
    • Y02E60/521Proton Exchange Membrane Fuel Cells [PEMFC]
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/30Application of fuel cell technology to transportation
    • Y02T90/32Fuel cells specially adapted to transport applications, e.g. automobile, bus, ship

Abstract

The invention relates to a membrane electrode assembly for a fuel cell, which has a proton exchange membrane (11) having on one side an active surface (12) for forming an anode and on the other side an active surface (12) for forming a Cathode, wherein the active surfaces (12) are each surrounded by a non-active surface (15). It is provided that the non-active surfaces (15) are stabilized on the anode side and on the cathode side with a subgasket, wherein in each case at least one region (17) of the non-active surfaces (15) for forming at least one moistening surface (18) without subgasket remains or with a perforated or perforated subgasket is provided, wherein the at least one moistening surface (18) has a size of 1 to 15% of the total area of the membrane-electrode unit and wherein the at least one moistening surface (18) forming, non-active regions (17) at least sections are congruent. The invention further relates to a fuel cell assembly and a motor vehicle having a fuel cell assembly.

Description

  • The invention relates to a membrane electrode assembly for a fuel cell, which has a proton exchange membrane having on one side an active surface for forming an anode and on the other side an active surface for forming a cathode, wherein the active surfaces of each a non-active surface are surrounded, a fuel cell assembly and a motor vehicle.
  • Fuel cells use the chemical transformation of a fuel with oxygen to water to generate electrical energy. For this purpose, fuel cells contain as core component the so-called membrane electrode assembly (MEA, membrane electrode assembly), which is a composite of a proton-conducting membrane and one on both sides of the membrane arranged gas diffusion electrode (GDE, gas diffusion electrode) as the anode and cathode. In addition, fuel cell types are known which have a liquid electrolyte instead of a membrane. As a rule, the fuel cell is formed by a multiplicity of stacked MEAs whose electrical powers add up. During operation of the fuel cell, the fuel, in particular hydrogen H 2 or a hydrogen-containing gas mixture, is fed to the anode, where an electrochemical oxidation of H 2 to H + takes place with emission of electrons. About the membrane or the electrolyte, which separates the reaction chambers gas-tight from each other and electrically isolated, there is a transport of protons H + from the anode compartment into the cathode compartment. The electrons provided at the anode are supplied to the cathode via an electrical line. The cathode is supplied with oxygen or an oxygen-containing gas mixture, so that a reduction of O 2 to O 2 - takes place under absorption of the electrons. At the same time, these oxygen anions in the cathode compartment react with the protons transported via the membrane to form water. The direct conversion of chemical to electrical energy fuel cells achieve over other electricity generators due to the circumvention of the Carnot factor improved efficiency.
  • The most advanced fuel cell technology currently used, for example, for traction applications for propulsion of motor vehicles is based on polymer electrolyte membranes (PEM) as proton exchange membranes. For the functional principle of the PEM fuel cell, the proton conductivity of the polymer electrolyte membranes is essential. The polymer electrolyte membranes usually consist of a perfluorinated polymer backbone with side chains ending in sulfonic acid groups (-SO 3 H). When water absorption of the polymer electrolyte membrane, the protons of the sulfonic acid groups are separated. Due to the polarity of water, a hydration shell forms around the protons (hydration), causing them to move freely. The water absorption of the polymer electrolyte membranes also leads to a swelling, which has the consequence of increasing the microporosity and thus also increases the proton conductivity. Since the proton transport is based on the dissociation and hydration by water and further increased by swelling, the ionic conductivity σ is crucially dependent on the water content γ of the polymer electrolyte membranes, which is defined as the amount of water moles n H₂O per sulfonic acid moles n SO₃H :
    Figure 00020001
  • The water content of the polymer electrolyte membrane is significantly influenced by the humidity of the supplied gases. If the gases supplied are too dry, water is discharged from the polymer electrolyte membrane and the proton conductivity decreases.
  • The influence of the gas humidity on conductivity can be demonstrated on commercially available membranes, for example, by DuPont under the tradename Nafion ® or by the company Gore with the trade name Gore Select ®.
  • Both of the aforementioned proton exchange membrane types are based on the principle described above, but the Gore Select® proton exchange membranes are substantially thinner due to the higher mechanical strength achieved by using a PTFE (expanded PTFE) backbone.
  • In these proton exchange membranes, although the conductivity increases exponentially with increasing relative humidity of the supplied gases and correspondingly increasing water content of the proton exchange membrane, too much moisture adversely affects the operating behavior and the electrical output of the fuel cell. If too much moisture is added or if product water formed at the cathode can not be sufficiently removed, both liquid water and gaseous water will clog the very small pores in the gas diffusion layer (GDL) and the electrodes within the fuel cell. As a result, the transport of reaction gases is hindered to the active surface and the cell is undersupplied in the appropriate places. At very high humidity condensed water can also clog entire gas distribution channels in the river field and thus, ever according to structure of the flow field, very large cell areas completely separate from the gas supply. According to the decrease of the supplied active cell area, the power density of the cell decreases.
  • An excess of water is usually a problem that occurs on the cathode side, since the product water is formed here. In most fuel cell systems, the operating temperature increases with the current. The amount of product water formed increases linearly with the current. Since both produced water mass as well as operating temperature and pressure have a great influence on the moisture demand of the fuel cell, optimum humidification of the fuel cell must be ensured. In addition, the MEA and GDL material, their structure and composition, as well as the gas supply have great influence. The GDL connects the electrode to the current collector of a fuel cell or to the bipolar plates of a fuel cell stack. In the case of gas supply, the stoichiometry and thus the amount of gas supplied, as well as the pressure loss via a gas supply channel, which essentially depends on the flow field design, determine how well any condensed water droplets can be discharged from the fuel cell. A balanced water regime with high membrane moisture, but with no liquid water and obstructing gas supply, is essential for stable and efficient fuel cell operation with long cell life.
  • In order to obtain an optimization of the moisture content of the proton exchange membranes, a great number of technical developments can be deduced from the prior art, for example it is known from US Pat DE 10 2007 008 214 A1 known to provide a humidification for fuel cells by a water transport unit via a fluid channel water from a moisture-rich flow path transported to another area of the fuel cell, which requires water. Furthermore, the prior art documents DE 10 2008 016 093 A1 . DE 10 2009 017 906 A1 and DE 10 2010 033 525 A1 relevant.
  • The invention has for its object to provide a membrane electrode assembly or a fuel cell assembly, which allows optimized humidification with a low design cost.
  • This object is achieved by a membrane electrode assembly (MEA) having the features of claim 1 and a fuel cell assembly having the features of claim 8.
  • The membrane-electrode assembly (MEA) for a PEM fuel cell according to the invention has a proton exchange membrane having on both sides an active surface which forms an anode on one side of the proton exchange membrane and a cathode on the other side. At the electrodes, the reactions taking place for fuel cells with supply of hydrogen (anode side) and oxygen (cathode side) take place.
  • The materials used for the proton exchange membrane and the formation of the electrode layer on the proton exchange membrane are known to those skilled in the art.
  • The active area on the anode side or on the cathode side is in each case surrounded by a non-active area, wherein the non-active areas are stabilized on the anode side and on the cathode side with a subgasket.
  • According to the invention, at least one area of the non-active areas remains to form at least one moistening area without a stabilizing subgasket. Alternatively, this area may be provided with a perforated or perforated subgasket. Both alternatives can also be combined to control humidification.
  • The perforated or perforated subgasket may be integrally formed with the remaining subgasket to have been perforated, for example by means of a laser or by mechanical punching. However, it is also possible that the perforated or perforated subgasket is not connected to the rest of the subgasket. The perforations or openings in the subgasket preferably each have an opening diameter of less than 1 millimeter.
  • The anode and cathode-side surfaces without subgasket are arranged congruently at least in sections, so that the at least one moistening surface results, by means of which moisture can be easily transported from one side of the proton exchange membrane to the other. Advantageously, a compensation of the moisture between the anode and cathode space can be ensured in a simple manner via this humidification surface.
  • The at least one moistening surface preferably has a size of 1 to 15% of the total area of the membrane-electrode assembly, more preferably 4 to 6%, with 5% being most preferred to ensure optimum moistening.
  • In the case of commonly used membrane-electrode assemblies, this corresponds to an area of 1 to 20 cm 2 .
  • Preferably, the at least one moistening surface in the flow direction has a length of at least 1 mm.
  • Subgaskets in themselves belong to the state of the art and are used, for example, in the EP 1807893 A1 described. A subgasket is used for mechanical stabilization of the proton exchange membrane, since this usually only has a thickness in the micron range, in order to allow the smallest possible dimensions of a fuel cell stack.
  • As Subgasket example, films of polyethylene terephthalate can be used, which are characterized in particular by a very low water absorption and thus dimensionally stable. In addition, such films are chemically and thermally stable, so that their function is ensured during the service life of the membrane electrode assembly.
  • It is also possible to apply monomers and oligomers to the corresponding regions of the proton exchange membrane by suitable methods, such as spraying using masks, inkjet printing or other coating methods, and then polymerizing them. This can be done depending on the monomers or oligomers used, for example by heat, light or moisture. In principle, all polymers which are chemically and thermally stable and show only a slight tendency to absorb water are suitable. These are, for example, corresponding polyurethanes, polyacrylates or polymethacrylates. The respectively suitable polymers or monomers or oligomers are known to the skilled person from the prior art. The in-situ produced subgaskets are easier to produce than those made of film and reduce the risk of damage to the proton exchange membrane during application of the subgasket.
  • Subgaskets represent resistance to water permeation, as does the active area, i. H. the electrode layer on the proton exchange membrane.
  • Preferably, the moistening surfaces directly adjoin the active surfaces. It is also possible not to place them directly adjacent to the active surfaces, but it is essential that the trained humidifying surface or humidifying surfaces can be swept by the anode and cathode gas streams.
  • To control the transport of moisture, the moistening surface is arranged in the region of an opening for the introduction of an anode gas stream or in the region of an opening for discharging a cathode gas stream or in the region of an opening for the introduction of a cathode gas stream or in the region of an opening for discharging an anode gas stream.
  • The inventive design of the membrane-electrode assembly with at least one moistening surface is accordingly designed for operation with reaction gases in the countercurrent principle.
  • According to a preferred embodiment of the membrane-electrode assembly, the membrane-electrode assembly has two humidifying surfaces disposed on opposite sides of the active surfaces so that in the region of each orifice for introducing or removing a gas flow there is a moisture exchange between anode and gas. and cathode gas can take place. By the countercurrent principle of the reaction gases thus each gas stream is guided at the beginning and at the end of the reaction path in each case via a moistening surface.
  • According to a particularly preferred embodiment, the at least one moistening surface corresponds in width to the width of the active surface, so that the Anodenbeziehungsweise cathode gas stream is completely guided over the at least one moistening surface, whereby advantageously optimal moistening is made possible with a very low design effort.
  • The at least one humidifying surface is preferably rectangular in shape, but other geometries are possible depending on the other parameters of the fuel cell.
  • With such a structure and corresponding adjustment of the active area in relation to the internal humidifying surface (s), i. H. with appropriate dimensioning of the different surfaces, the optimum for the respective fuel cell humidification can be easily adjusted.
  • According to a preferred embodiment of the membrane-electrode assembly, the at least one moistening surface on both or on one side of the proton exchange membrane is covered with a fleece.
  • By adjusting its parameters, for example porosity, hydrophilic or hydrophobic properties, water storage capacity and the like, this nonwoven can be advantageously conditioned for a defined moisture exchange between cathode and anode, wherein the respective nonwoven fabric for the anode or cathode side can be designed differently. As a nonwoven, in principle, the materials in question, the expert also known for the gas diffusion layer (GDL). Essential for their suitability are temperature resistance and permeation capacity. Preference is given to carbon webs, preferably with blunt fibers whose hydrophilicity and / or hydrophobicity can be adjusted by suitable means known to the person skilled in the art.
  • This nonwoven may have approximately the thickness of the gas diffusion layer (GDL), which is likewise usually present in a fuel cell. This serves as a diffusive spacer between gas supply channels and is designed to be electrically conductive. The GDL usually has a certain thickness, which can correspond to a multiple of the membrane itself.
  • However, compared to GDL, the nonwoven has more diffuse properties for water (liquid or gaseous). Furthermore, depending on the application, the nonwoven can exhibit hydrophobic or even hydrophilic properties.
  • On the cathode side, the GDL is usually designed so that the resulting product water is led away from the proton exchange membrane. The fleece at the cathode outlet, however, is advantageously designed such that the cathode-side water is passed to the proton exchange membrane.
  • In particular, the focus of humidification is on the anode side, since good humidification is necessary to assist proton conduction of the proton exchange membrane. The optimum performance of a fuel cell is usually achieved when the anode and cathode are each moistened.
  • An advantage of the invention is that the water separator usually used on the anode side can optionally be dispensed with directly at the gas outlet of a fuel cell stack. This water separator serves to catch condensed water in droplet form.
  • Advantageously, the efficiency is also increased by the membrane-electrode unit according to the invention and it can be a cathode-side, external humidification reduced or possibly omitted entirely.
  • Also claimed in the invention is a fuel cell system having the above-described membrane-electrode assembly. The statements regarding the membrane electrode assembly according to the invention therefore apply correspondingly to the fuel cell system.
  • Optimum operation of a fuel cell system with at least one fuel cell, in particular a PEM fuel cell, can be achieved if the cathode and the anode-side gas flows are moistened. Therefore, the internal humidification of the membrane-electrode assembly of the present invention may also be complementary to existing cathode-side humidification applications, such as a membrane humidifier or a hollow fiber module.
  • The fuel cell systems according to the invention have, in addition to other conventional devices, a cathode gas supply and an anode gas supply, which are arranged such that the cathode gas and the anode gas sweep the electrodes according to the countercurrent principle.
  • The benefit of such combined humidification is not only an increase in efficiency, but also a volumetric reduction of an external humidifier and a reduction in the pressure drop across the external humidifier to be overcome by an air compressor as a result of the volumetric reduction.
  • Claimed is also a motor vehicle, which has a fuel cell system with the membrane-electrode unit according to the invention.
  • Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.
  • The invention will be explained below in embodiments with reference to drawings. Show it:
  • 1 in an anode-side view, a membrane electrode assembly (MEA) according to the prior art,
  • 2 in a cathode-side view the membrane-electrode unit (MEA) after 1 .
  • 3 in a sectional side view of the membrane electrode assembly (MEA) after 1 and 2 .
  • 4 in a sectional side view of the membrane electrode assembly (MEA) after 1 and 2 with a representation of the water content of the cathode gas over the length of the membrane-electrode assembly,
  • 5 in an anode-side view of a membrane electrode assembly (MEA) according to a second embodiment of the invention,
  • 6 in a cathode-side view of the membrane electrode assembly (MEA) according to the invention 5 .
  • 7 in a sectional side view of the membrane electrode assembly (MEA) according to the invention 5 and 6 .
  • 8th in an anode-side view of a membrane electrode assembly (MEA) according to another embodiment of the invention,
  • 9 in a cathode-side view of the membrane electrode assembly (MEA) according to the invention 8th .
  • 10 in a sectional side view of the membrane electrode assembly (MEA) according to the invention 8th and 9 .
  • 11 in a sectional side view of the membrane electrode assembly (MEA) according to the invention 5 and 6 with a representation of the water content of the anode and cathode gas over the length of the membrane electrodes.
  • 12 in an anode-side view of a membrane electrode assembly (MEA) according to the invention according to a third embodiment,
  • 13 in a cathode-side view of the membrane electrode assembly (MEA) according to the invention 12 .
  • 14 in a sectional side view of the membrane electrode assembly (MEA) according to the invention 12 and 13 ,
  • The 1 to 3 show a membrane-electrode unit 10 (MEA) according to the prior art for a PEM fuel cell, not shown here, via a proton exchange membrane 11 has an active surface on both sides 12 owns, whereby the in 1 shown side of the proton exchange membrane 11 the anode and the other side of the proton exchange membrane 11 according to 2 the cathode is forming. The cut for the in 3 shown side view of the membrane electrode assembly 10 is in the 1 and 2 by the reference numeral 13 characterized. On both sides of the active area 12 are schematic openings 14 for the supply and discharge of cathode gas O 2 and anode gas H 2 and for a coolant shown. The cathode gas O 2 and the anode gas H 2 are on opposite sides of the counterflow principle on the cathode side or on the anode side over the active surface 12 guided. The non-active area 15 that the active area 12 surrounds, is on both sides with a foil 16 (Subgasket) mechanically stabilized.
  • In 4 is the membrane-electrode unit 10 according to the prior art in relation to the water content γ of the cathode gas O 2 as a function of the length l of the membrane-electrode assembly 10 shown. During operation of the fuel cell flows a not actively humidified and oxygen-rich cathode gas O 2 , for example, air on the cathode side of the membrane electrode assembly 10 past. In the beginning, ie before the air is the active area 12 overflowed, the cathode gas O 2 has a low moisture content. Subsequently, the cathode gas O 2 flows over the active surface 12 , Wherein during the fuel cell-typical reaction on the cathode side product water is formed, which is proportionally absorbed by the cathode gas O 2 . The water content γ can increase to saturation. Is the cathode gas O 2 over the active area 12 has flowed, this therefore has a higher water content γ than at the beginning of the active area 12 , The foil 16 at the beginning and at the end of the active area 12 represents a resistance to water permeation, so that the non-active area 15 significantly inhibits water permeation.
  • The 5 to 7 show a membrane electrode assembly according to the invention 10 facing the known membrane electrode assembly 10 this distinguishes that the active area 12 for anode and cathode in and counter to the direction of the cathode gas O 2 and the anode gas H 2 to a region 17 the proton exchange membrane 11 borders, which is free of a foil 16 for stabilization. This area 17 is on the anode side and cathode side congruently positioned and forms a total of one humidifying surface 18 out. The humidifying surface 18 one has a length X1 or Y1 and a width of X2 and Y2, respectively. Apart from the area 17 or the humidification surface 18 is the non-active area 15 again with a foil 16 provided for stabilization.
  • The 8th to 10 show a membrane electrode assembly according to the invention 10 according to a second embodiment, which is opposite to in the 5 to 7 represented membrane electrode unit 10 thereby distinguishes that the area 17 or the moistening surface of the proton exchange membrane also with a film 16a is covered, which is perforated, so that a passage of moisture is possible. Otherwise, the reference numerals correspond to those of 5 to 7 ,
  • As in 11 relating to the embodiment according to the 5 - 7 can be seen, in which the water content γ of the cathode gas O 2 and the anode gas H 2 over the length l of the membrane electrode assembly 10 is applied, via the humidifying surfaces 18 a water exchange, there the moist cathode gas O 2 the active surface 12 locally leaves where the dry anode gas H 2 in the active area 12 entry. Accordingly, a moisture exchange can take place, so that cathode gas O 2 and anode gas H 2 are optimally moistened.
  • In the 12 to 14 is a third embodiment of a membrane electrode assembly according to the invention 10 shown, differing from the first embodiment of the membrane electrode assembly 10 according to the 5 to 7 this distinguishes that the free areas 17 or the humidifying surfaces 18 anode side and cathode side with a nonwoven 19 covered for that the humidifying surfaces 18 ensures the required mechanical stability while supporting the permeation of moisture in the desired direction. This fleece 19 may correspond approximately to the thickness of a gas diffusion layer (GDL), not shown here.
  • LIST OF REFERENCE NUMBERS
  • 10
    Membrane-electrode assembly
    11
    Proton exchange membrane
    12
    active area
    13
    Reference number for section
    14
    opening
    15
    not active area
    16
    Film / Subgasket
    17
    free area
    18
    dampening
    19
    fleece
    l
    length
    O 2
    cathode gas
    H 2
    Anodic gas water content
    X1, Y1
    length
    X2, Y2
    width
  • QUOTES INCLUDE IN THE DESCRIPTION
  • This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.
  • Cited patent literature
    • DE 102007008214 A1 [0009]
    • DE 102008016093 A1 [0009]
    • DE 102009017906 A1 [0009]
    • DE 102010033525 A1 [0009]
    • EP 1807893 A1 [0021]

Claims (11)

  1. Membrane electrode unit for a fuel cell, which has a proton exchange membrane ( 11 ) having on one side an active area ( 12 ) for forming an anode and on the other side an active area ( 12 ) for forming a cathode, wherein the active surfaces ( 12 ) each from a non-active area ( 15 ), characterized in that the non-active surfaces ( 15 ) are stabilized on the anode side and on the cathode side with a subgasket, wherein in each case at least one region ( 17 ) of non-active surfaces ( 15 ) for forming at least one moistening surface ( 18 ) remains without subgasket or is provided with a perforated or perforated subgasket, wherein the at least one moistening surface ( 18 ) has a size of 1 to 15% of the total area of the membrane-electrode unit and wherein the at least one moistening area ( 18 ) forming non-active areas ( 17 ) are at least partially congruent.
  2. Membrane electrode assembly according to claim 1, characterized in that the moistening surface ( 18 ) in the region of an opening ( 14 ) for the introduction of an anode gas stream or in the region of an opening ( 14 ) arranged to divert a cathode gas flow or in the region of an opening ( 14 ) for the introduction of a cathode gas flow or in the region of an opening ( 14 ) is arranged for discharging an anode gas flow.
  3. Membrane-electrode assembly according to claim 1, characterized in that the membrane-electrode assembly ( 10 ) two moistening surfaces ( 18 ) on opposite sides of the active surfaces ( 12 ) are arranged.
  4. Membrane-electrode assembly according to claim 3, characterized in that a moistening surface ( 18 ) in the region of an opening ( 14 ) for the introduction of an anode gas stream or in the region of an opening ( 14 ) is arranged for the derivation of a cathode gas flow and a second moistening surface ( 18 ) in the region of an opening ( 14 ) for the introduction of a cathode gas flow or in the region of an opening ( 14 ) is arranged for discharging an anode gas flow.
  5. Membrane electrode unit according to one of claims 1 to 4, characterized in that the at least one moistening surface ( 18 ) in their width (X2, Y2) of the width of the active surfaces ( 12 ) corresponds.
  6. Membrane-electrode assembly according to one of claims 1 to 5, characterized in that the at least one moistening surface ( 18 ) on the anode side and / or cathode side with a nonwoven ( 19 ) is covered.
  7. Membrane-electrode assembly according to claim 6, characterized in that the fleece ( 19 ) on the anode side and on the cathode side different properties which relate to the permeation has.
  8. Membrane-electrode assembly according to one of claims 1 to 7, characterized in that the at least one humidifying surface has a size of 4 to 6%, preferably 5% of the total area of the membrane-electrode unit.
  9. Fuel cell arrangement with at least one fuel cell, a membrane-electrode unit ( 10 ) according to any one of claims 1 to 8.
  10. Fuel cell arrangement according to claim 9, characterized in that the fuel cell arrangement comprises a second, external humidifying device.
  11. Motor vehicle, a fuel cell assembly according to claim 10 having.
DE102012011441A 2011-07-02 2012-06-08 Membrane electrode unit for a fuel cell Pending DE102012011441A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE102011106418 2011-07-02
DE102011106418.8 2011-07-02
DE102012011441A DE102012011441A1 (en) 2011-07-02 2012-06-08 Membrane electrode unit for a fuel cell

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