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
• • 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
  • 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
  • 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
  • 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 present invention relates to an electrode for a fuel cell with a solid polymer electrolyte comprising in its active layer at least two distinct fields: one is in particular the seat of electrochemical reactions of electronic transfer, the other is devoted only to ionic conduction, and possibly a third domain is used for the transfer of gaseous species such as oxidizer, fuel, reaction products and inert compounds, this independently of the possible presence in the active layer of a binder such as PTFE or FEP.
• gaseous species such as oxidizer, fuel, reaction products and inert compounds
• the improvement in the performance of fuel cells with solid polymer electrolyte as well as the marked reduction in their cost means that the surface power density of their electrodes must be greatly increased. In this way, the cost of the bipolar collectors, the cost of the membrane, and the cost of using the electrodes will be minimized.
• a volume of Nafion TM is generally introduced into the active layer on the order of 33% of that of the platinum carbon present in this layer.
• the ionic conduction in this layer was 5 to 10 times more lower than that calculated knowing the amount of Nafion TM introduced and its specific conductivity. This difference is due to the fact that the Nafion layer, taking into account the porosity characteristics of the agglomerate of carbon particles, is poorly distributed: catalyst sites are not covered by Nafion TM while there are clumps of Nafion TM at other points in the porous layer. This results in a very discontinuous conduction which remains possible at the cost of significant tortuosity.
• the present invention aims to overcome the aforementioned limitations as to the thickness of the effective electrochemical layer.
• the object of the present invention is an electrode for a fuel cell with a solid polymer electrolyte, characterized in that its active layer comprises at least two distinct areas: one is in particular the seat of electrochemical reactions of electronic transfer and the other is devoted only to ionic conduction.
• a third domain is used for the transfer of gaseous species such as oxidizer, fuel, reaction products and inert compounds, this independently of the possible presence of a binder such as PTFE or FEP.
• the seat field of electrochemical reactions is of microporous structure without preferential orientation; its pores, formed by the interstices between carbon particles, have on their surface catalyst microparticles covered by a deposit of ionic conductor whose thickness must be as uniform as possible and between 50 and 200 ⁇ .
• the volume occupied by the fibers impregnated with an ionic conductor will be between 10 and 30% of that of the active layer and the average diameter of the fibers may be between 0.5 and 5 ⁇ m, their length being itself between 20 and 100 ⁇ m.
• the material initially constituting the fibers must have a high capacity for fixing the solution in which the ionic conductor is dissolved or dispersed.
• the suitable material is either an organic compound such as cotton or polyester, or an inorganic compound such as silica.
• the addition of fibers rich in ionic conductor in the active layer makes it possible to limit the amount of conductor covering the microparticles of catalyst so that, according to the invention, the volume of ionic conductor covering these particles represents only 5 to 20% of the volume of the carbon and catalyst assembly present in the active layer, instead of 33%, a value generally used for electrodes of traditional structure.
• the deposition of ionic conductor on the surface of the carbon particles comprising the catalyst microparticles is carried out by immersion and agitation of the carbon particles in a solution or microdispersion of the ionic conductor in an appropriate solvent or solution, followed by the slow evaporation of the liquid phase.
• the electrode according to the invention therefore offers similarities with living organs which are characterized by distinct networks by their functions and by their size: bronchioles for the transfer of gases (oxygen supply, evacuation of C0 2 ), network of arteries and veins for blood, network of arteries and capillary network between them.
• the volume of these tubes, in the active layer should be between 5 and 15% of the volume thereof. According to this process, it can be envisaged to reduce the content of binder (PTFE or FEP) in the active layer.
• an oxygen electrode has been produced, characterized in that it comprises, on the one hand, electrochemically active areas where efforts have been made to produce a very thin and homogeneous layer of Nafion TM and of on the other hand a network of fibers rich in Nafion TM.
• the carbon constituting the active layer is a Vulcan type black on which platinum is dispersed, representing 30% of the carbon mass plus platinum.
• the platinum carbon is dispersed with ultrasonic stirring in a Nafion TM solution, the amount of Nafion TM (expressed as dry extract) represents 10% of the volume occupied by the carbon and the concentration of the Nafion TM solution is only 2% .
• the carbon particles are extracted and the solvent for the solution is evaporated by heating for one hour at 95 ° C.
• platinized carbon particles coated with Nafion TM are then mixed with 35% by mass of PTFE relative to the mass of carbon and with a solvent which is a water + mixture. 50% ethanol.
• a solvent which is a water + mixture. 50% ethanol.
• fibers impregnated with Nafion TM in the proportion of 30% by volume relative to the total volume of platinum carbon.
• the impregnation of these fibers which initially consist of polyester microfibers with an average diameter of 1.5 ⁇ m and an average length of 50 ⁇ m, was carried out by immersing the fibers in the solution of Nafion TM soluble at 5% in clear excess then evaporation by drying at 95 ° C.
• Two batteries were formed: they include 10 cm 2 front surface electrodes. In each cell, the hydrogen electrodes are identical, as is the membrane (Nafion TM 115). After stabilization of the temperature at 80 ° C and supply at 2 bar absolute in 0 2 and H 2 , the current of each cell was recorded under 0.7 V.
• the overall current is 5.5 A.
• the overall current is 8 A.

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

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

Country Status (7)

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Family Cites Families (11)

• 1999
  • 1999-01-14 FR FR9900295A patent/FR2788630B1/fr not_active Expired - Fee Related
• 2000
  • 2000-01-07 JP JP2000594168A patent/JP2002535805A/ja active Pending
  • 2000-01-07 KR KR1020017008759A patent/KR20010110339A/ko not_active Application Discontinuation
  • 2000-01-07 CA CA002360338A patent/CA2360338A1/fr not_active Abandoned
  • 2000-01-07 EP EP00900592A patent/EP1151488A1/de not_active Withdrawn
  • 2000-01-07 WO PCT/FR2000/000084 patent/WO2000042670A1/fr not_active Application Discontinuation
• 2001
  • 2001-07-11 US US09/903,016 patent/US20030003346A1/en not_active Abandoned

Non-Patent Citations (1)

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