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EP1393399A2 - Pile a combustible - Google Patents

Pile a combustible

Info

Publication number
EP1393399A2
EP1393399A2 EP02732371A EP02732371A EP1393399A2 EP 1393399 A2 EP1393399 A2 EP 1393399A2 EP 02732371 A EP02732371 A EP 02732371A EP 02732371 A EP02732371 A EP 02732371A EP 1393399 A2 EP1393399 A2 EP 1393399A2
Authority
EP
European Patent Office
Prior art keywords
fuel cell
electrode elements
cell according
gas
carrier substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02732371A
Other languages
German (de)
English (en)
Inventor
Georg Frank
Cornelius Haas
Werner Scherber
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mercedes Benz Group AG
Original Assignee
DaimlerChrysler AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by DaimlerChrysler AG filed Critical DaimlerChrysler AG
Publication of EP1393399A2 publication Critical patent/EP1393399A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H01M4/8626—Porous electrodes characterised by the form
    • 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
    • H01M4/96—Carbon-based electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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 fuel cell according to the preamble of patent claim 1.
  • the electrolyte electrode unit (when using an electrolyte in the form of a membrane usually referred to as a MEA membrane electrode assembly) is a complex electrochemical system, the internal structure and mode of operation of which not only directly determine the efficiency of the cell, but also The design of the other components of the fuel cell stack and peripheral units has a decisive influence and plays a dominant role in all considerations regarding the possible increase in performance of the fuel cell (efficiency, compact structure, durability, reliability).
  • the electrochemical reaction on the electrodes of a fuel cell basically only takes place in areas where the catalyst is in direct contact with both an electron-conducting phase and an ion-conducting phase, i.e. every catalyst grain contributing to sales must be physically connected to the PEM on the one hand and the external contact (bipolar plate) on the other hand.
  • reaction gases must be present in these zones if possible can diffuse in and out freely (Fig. 1).
  • a preferred manufacturing process for fuel cell electrodes is based on the wet chemical deposition of the smallest Pt particles on larger carbon particles, which are mixed together with ionomeric binders, solvents and other additives to form a paste, which is then applied to carbon paper (this forms the GDL) and further processed.
  • ionomeric binders, solvents and other additives to form a paste, which is then applied to carbon paper (this forms the GDL) and further processed.
  • 20% of the amount of catalyst introduced can be effectively bound in this way. This factor alone clearly confirms that the 3-phase reaction system cannot be satisfactorily optimized on the basis of disordered, statistically distributed structural elements.
  • US Pat. No. 6,136,412 describes a nanostructure made from needle-shaped elements as a support for the catalyst centers of an MEA configuration.
  • the nanostructure consists of an electrically non-conductive material.
  • the elements of the nanostructure have to be coated subsequently.
  • the nanostructure is partially embedded in the polymer electrolyte membrane.
  • the nanostructure is first produced on an auxiliary substrate. Then the needle-shaped elements of the nanostructure are removed from the auxiliary substrate again, e.g. by scraping or brushing, and transferred to the surface of the membrane, in particular by mechanical pressing. As a result, an initially existing alignment of the needle-shaped elements is lost again. In addition, some of the needle-shaped elements will break off and be shredded during the transfer process. This is shown as an advantage because it makes the surface more rugged and therefore larger.
  • the object of the invention is to provide an MEA configuration with which on the one hand a sufficiently large inner reaction area can be presented and on the other hand with which the most important loss factors of the fuel cell reactions become strong reduced so that almost the full performance potential of the fuel cell can be exploited.
  • the concept on which the invention is based is to use an orderly, regular micro- or nanostructured electrode structure instead of the random 3D reaction layer that is commonly used today.
  • Electrodes on a carrier substrate. These electrode elements can also be porous.
  • the electrode elements are coated with a catalyst and are completely or partially enclosed on the outside by the material of the electrolyte (e.g. a polyelectrolyte membrane).
  • the catalytic reaction zones on the electrode elements are connected to the gas transport system of the fuel cell via openings in the carrier substrate.
  • the carrier substrate can also consist of a porous material, so that no additional openings need to be produced.
  • the electrode elements are electrically conductively connected to one another and to the outer connections of the single cell (typically bipolar plates).
  • the electrode elements are arranged substantially regularly distributed over the carrier substrate and can in particular be aligned essentially parallel to one another.
  • the electrode elements are oriented out of the plane of the carrier substrate.
  • the angle between the plane of the carrier substrate and the Electrode elements is greater than 20 °, preferably greater than 40 ° and in particular greater than 60 °, for example 90 °.
  • Figure 1 is a schematic diagram of the elementary reaction zone of a fuel cell.
  • FIG 3 shows the schematic representation of an MEA configuration according to the invention (nanowhisker);
  • FIG. 4 shows the schematic representation of a further MEA configuration according to the invention (nanotubes);
  • FIG. 5 shows the recording of a nanoporous oxide matrix for the production of an electrode structure according to the invention
  • FIG. 6 shows the recording of an electrode structure made of parallel aligned nickel needles on a self-supporting nickel membrane.
  • FIG. 3 shows a schematic representation of a first MEA configuration according to the invention.
  • the needle-shaped, nanoscale electrode elements which are regularly arranged on a metal foil and together with this form the electrode of the MEA.
  • the needle-shaped electrode elements which can in particular consist of a metallic material, for example nickel, penetrate almost completely or to a defined depth t into the PEM and have a platinum coating in this zone.
  • the metallic carrier foil of the needles has gas-permeable openings through which the reaction gases enter a gas distribution channel g between the metal foil and the PEM and from there directly to the catalytic reaction zones.
  • the GDL adjoins the smooth side of the metal foil and is adjacent to the macro gas distribution channels of the bipolar plate (not shown).
  • the gas transport system (bipolar plate, GDL and gas distribution channel) is structured hierarchically, similar to the bronchial system of a lung (trachea, trachea, alveoli), and can function very effectively in this way.
  • a typical reaction area of approximately 10 cm 2 could be achieved, for example, with a parallel aligned needle structure of the following dimensions:
  • This needle structure is comparable with the state of the art in terms of reaction area and catalyst use, but offers decisive advantages with regard to the reaction kinetics.
  • Gas diffusion is significantly favored due to the relatively open needle structure, which is directly connected to the macroscopic GDL via the gas channel g.
  • the gas molecules no longer have to move through a relatively deep nanoporous structure.
  • Estimates of this effect suggest an improvement of more than two orders of magnitude, i.e. gas diffusion would no longer be a limiting factor.
  • the situation is similar with ion conductivity; the whiskers couple directly to the highly conductive PEM, so that the active layer of a conventional type with its geometrically determined compromises can be dispensed with and impoverishment effects in the reaction zone are practically negligible.
  • FIG. 4 Another solution according to the invention, with which the principle of the hierarchical gas transport system is implemented even more consistently, is shown schematically in FIG. 4.
  • Porous, nanoscale tubes e.g. made of graphite
  • the carrier membrane is metallized on its smooth side, so that the nanoscale tubes are connected to one another in an electrically conductive manner.
  • the outside of the tubes are completely enclosed by the ion-conducting layer.
  • the carrier membrane has gas-permeable openings through which the reaction gases pass directly from the macrogas channels of the bipolar plate into the interior of the tubes and further through the porous wall of the tubes to the catalytic reaction zones.
  • - MEA can be represented as a self-supporting module, making it a prerequisite for using simplified, light bipolar plates;
  • the MEA configurations according to the invention offer substantial savings in the use of noble metals and improved heat dissipation.
  • a membrane was used as the ion-conducting electrolyte. It is pointed out that the invention is not restricted to this special type of electrolyte, but that in principle any ion-conducting layer or coating can be used.
  • an oxide matrix with regularly arranged cylindrical pores is initially generated on the basis of an anodizing process, template process (FIG. 5), the geometric parameters being able to be set reliably over a wide range.
  • anodizing process template process (FIG. 5)
  • the dependence of the geometry parameters pore diameter, pore spacing and oxide layer thickness on the process parameters anodizing voltage, current density, temperature, type and acidity of the electrolyte are known in principle from classic anodizing technology. Typical values that can be achieved are pore diameters and pore spacings of about 10 nm to a few 100 nm, the smaller dimensions below 100 nm appearing particularly interesting for the MEA application for the reasons given.
  • the height of the structures is a few 100 nm to 1000 or 2000 nm.
  • an aspect ratio of a whisker structure of 1:10 corresponds to the above-mentioned area ratio of 10 cm 2 reaction area over 1 cm 2 base area of an active layer according to the prior art.
  • Electrochemical and electroless galvanic processes are particularly suitable for the deposition of metallic particles from nickel, cobalt, chromium, manganese, copper, zinc, tin and noble metals, while pyrolytic processes are used for the deposition of graphite-like layers or other metals. Examples here are the decomposition of acetylene or other hydrocarbons, or of organometallic compounds in the gas phase by the action of temperature, catalysts and / or plasma discharges.
  • the oxide structure can also be impregnated with a wetting solution of suitable monomers (acrylonitrile, emulsifier, initiator) and then polymerized.
  • suitable monomers acrylonitrile, emulsifier, initiator
  • the polymer polyacrylonitrile
  • the polymer is pyrolyzed at higher temperatures and converted into graphite-like tubes or fibers.
  • nanoscale electrode structures made of graphite is regarded as particularly attractive, since good electrical conductivity, high chemical stability and low costs of the starting materials can be reconciled in this way.
  • the oxide matrix can then be removed in whole or in part.
  • a special challenge of the Nanotubes concept is to reduce the porosity of the tube walls, e.g. made of graphite, specifically adjusted to achieve the desired gas permeability. It has been shown that a special feature of the template process using anodized oxide masks can advantageously be used for this task.
  • the formation of the pores does not run exactly cylindrical, but with numerous small lateral dislocations, as can be seen on closer microscopic examination.
  • the dislocations depend on the anodizing parameters and the starting material and are typically a fraction of less than 50% of the pore diameter, but a continuous opening is retained in almost all of the pores formed in a template.
  • This whisker- or tube-shaped electrode structure can then be coated efficiently with the desired catalyst, for example by galvanic or electroless noble metal deposition.
  • tubular structures are expediently to be closed at the end, for example by a special polymerization process in which the tips are slightly wetted with the monomer and, if necessary, the interspaces are washed out in the partially crosslinked state. Punctual promotion of the polymerization at the tips can also be carried out by applying catalytic polymerization initiators or by heating the Structural elements happen. The tubes remain closed in the further manufacturing process.
  • the integration of the MEA can take place in various ways.
  • the nanostructured electrode foil and the membrane are pressed together under defined conditions (pressure, temperature, degree of humidity and duration).
  • the natural surface structure of the membrane prevents a gas-tight connection and allows gas to a certain degree.
  • the gas channel can be enlarged by further measures before integration, e.g. by micro-embossing the PEM, by applying a highly porous spacer layer (which does not have to perform any electrical or chemical functions) or by applying a thin sacrificial layer, which is dissolved again after the connection process.
  • a further method for producing a regular electrode structure in an electrolyte membrane consists of the following steps: First, as usual, metal whiskers are embedded in a porous anodized aluminum foil and then the oxide layer is partially etched away, so that the whiskers protrude above the surface at a certain height. This structure is coated with the catalyst, pressed into the electrolyte membrane and then the aluminum carrier foil and the remaining Al oxide are chemically removed. The free ends of the whiskers are then connected to a gas permeable porous electrically conductive layer, e.g. by applying (brushing on, slurrying, evaporating) a two-component mixture from which a component is subsequently removed again by thermal or chemical treatment.
  • the nanotube structure does not require a gas channel between the PEM and the carrier film, i.e. the electrode can be pressed fully into the membrane. This process can be promoted by swelling of the membrane and by the action of temperature, so that mechanically sensitive structures can also be processed.
  • the interstices of the electrode elements are first filled with a monomer, polymerized to an ion-conducting polymer and only then connected to the PEM film or another electrolyte.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Fuel Cell (AREA)
  • Inert Electrodes (AREA)

Abstract

Pile à combustible comportant une ou plusieurs cellules, chaque cellule individuelle comprenant une unité électrolyte-électrodes, des moyens de répartition des gaz réactifs sur les électrodes, ainsi qu'un contact électrique de ladite cellule. Selon la présente invention, les électrodes comportent des éléments électriquement conducteurs, disposés de manière régulière, à l'échelle du micron ou du nanomètre et ayant une forme d'aiguille ou tubulaire, qui sont fixés sur un substrat de support perméable aux gaz et recouverts d'un catalyseur. Les éléments d'électrode sont entourés à l'extérieur partiellement ou totalement par la matière de l'électrolyte. Les zones de réaction catalytique sur les éléments d'électrode sont reliées aux moyens de répartition des gaz par l'intermédiaire du substrat de support perméable aux gaz. Les éléments d'électrode sont reliés entre eux et avec le contact électrique de manière électriquement conductrice.
EP02732371A 2001-04-14 2002-04-04 Pile a combustible Withdrawn EP1393399A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10118651 2001-04-14
DE10118651A DE10118651A1 (de) 2001-04-14 2001-04-14 Brennstoffzelle
PCT/DE2002/001218 WO2002084773A2 (fr) 2001-04-14 2002-04-04 Pile a combustible

Publications (1)

Publication Number Publication Date
EP1393399A2 true EP1393399A2 (fr) 2004-03-03

Family

ID=7681627

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02732371A Withdrawn EP1393399A2 (fr) 2001-04-14 2002-04-04 Pile a combustible

Country Status (5)

Country Link
US (1) US20040170884A1 (fr)
EP (1) EP1393399A2 (fr)
AU (1) AU2002304886A1 (fr)
DE (1) DE10118651A1 (fr)
WO (1) WO2002084773A2 (fr)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040167014A1 (en) * 2002-11-13 2004-08-26 The Regents Of The Univ. Of California, Office Of Technology Transfer, University Of California Nanostructured proton exchange membrane fuel cells
WO2004062006A1 (fr) * 2002-12-16 2004-07-22 The Trustees Of The University Of Pennsylvania Anodes céramiques à haute performance et procédé de production desdites anodes
US20060008696A1 (en) * 2004-06-30 2006-01-12 Suk-Won Cha Nanotubular solid oxide fuel cell
JP4752216B2 (ja) * 2004-08-26 2011-08-17 トヨタ自動車株式会社 チューブ型燃料電池用膜電極複合体
WO2006047765A1 (fr) * 2004-10-27 2006-05-04 Pacific Fuel Cell Corp. Catalyseur cathodique resistant au methanol pour des piles a combustibles directes au methanol
US8247136B2 (en) 2005-03-15 2012-08-21 The Regents Of The University Of California Carbon based electrocatalysts for fuel cells
US7901829B2 (en) * 2005-09-13 2011-03-08 3M Innovative Properties Company Enhanced catalyst interface for membrane electrode assembly
JP5108240B2 (ja) * 2006-03-20 2012-12-26 トヨタ自動車株式会社 燃料電池及び燃料電池の製造方法
DE102007005232B4 (de) * 2007-01-30 2019-06-19 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Brennstoffzellenanordnung und ein Verfahren zu deren Herstellung
DE102008047142A1 (de) * 2008-09-12 2010-04-15 o.m.t. Oberflächen- und Materialtechnologie GmbH Katalyischer Werkstoff
US8859164B2 (en) * 2011-02-15 2014-10-14 Ford Global Technologies, Llc Bipolar plates and electrochemical cells employing the same
US10648092B2 (en) * 2015-11-10 2020-05-12 Kabushiki Kaisha Toshiba Electrode, membrane electrode assembly, electrochemical cell, and stack

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5338430A (en) * 1992-12-23 1994-08-16 Minnesota Mining And Manufacturing Company Nanostructured electrode membranes
US6136412A (en) * 1997-10-10 2000-10-24 3M Innovative Properties Company Microtextured catalyst transfer substrate
US6042959A (en) * 1997-10-10 2000-03-28 3M Innovative Properties Company Membrane electrode assembly and method of its manufacture

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO02084773A2 *

Also Published As

Publication number Publication date
WO2002084773A3 (fr) 2003-11-27
US20040170884A1 (en) 2004-09-02
DE10118651A1 (de) 2002-10-24
AU2002304886A1 (en) 2002-10-28
WO2002084773A2 (fr) 2002-10-24

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