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
• • 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
• • 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
  • H01M4/8636—Inert electrodes with catalytic activity, e.g. for fuel cells with a gradient in another property than porosity
• • 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
  • H01M4/8636—Inert electrodes with catalytic activity, e.g. for fuel cells with a gradient in another property than porosity
  • H01M4/8642—Gradient in composition
• • 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
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
• • 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
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
  • H01M8/0265—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant the reactant or coolant channels having varying cross sections
• • 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
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
• • 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
  • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
  • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
  • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
• • 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
  • H01M8/1007—Fuel cells with solid electrolytes with both reactants being gaseous or vaporised
• • 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 fuel cells, and in particular proton exchange membrane fuel cells.
• Fuel cells are considered in particular as a source of energy for motor vehicles produced on a large scale in the future.
• a fuel cell is an electrochemical device that converts chemical energy directly into electrical energy.
• a fuel cell comprises a stack of several cells in series. Each cell generates a voltage of the order of 1 Volt, and their stack can generate a supply voltage of a higher level, for example of the order of a hundred volts.
• each cell comprises an electrolyte membrane allowing only the passage of protons and not the passage of electrons.
• the membrane separates the cell into two compartments to avoid a direct reaction between the reactive gases.
• the membrane comprises an anode on a first face and a cathode on a second face, this assembly being usually designated by the term membrane-electrode assembly.
• dihydrogen used as fuel is ionized to produce protons crossing the membrane.
• the electrons produced by this reaction migrate to a flow plate and then pass through an electrical circuit external to the cell to form an electric current.
• oxygen is reduced and reacts with the protons to form water.
• the fuel cell may comprise a plurality of flow plates, for example of metal, stacked one on top of the other.
• the membrane is disposed between two flow plates.
• the flow plates may include channels and orifices to guide reagents and products to / from the membrane.
• the plates are also electrically conductive to form collectors of electrons generated at the anode.
• Gaseous diffusion layers (for Gas Diffusion Layer in English) are interposed between the electrodes and the flow plates and are in contact with the flow plates.
• Proton exchange membrane fuel cells still have a reduced service life. Fuel cells thus undergo aging, which is characterized for example by clogging of the cathode with water or irreversible degradation of the nanomaterials of the fuel cell. cathode, for example due to the degradation of the carbon support and the catalyst. These phenomena result in a gradual degradation of the performance of the battery.
• the management of the presence of water in the fuel cell is relatively complex. Indeed, the cathodic reaction involves the generation of water and water is also necessary to maintain the proton conductivity of the membrane. The reactive gases may thus require their prior humidification to allow the humidification of the membrane. However, an excessive amount of water can cause flooding of the catalytic sites and thus an interruption of the battery operation by blocking access of oxygen to the reactive sites.
• the redox potential of this reaction is about 0.2V (ENH).
• the cathode potential of the cell is generally greater than 0.2 V, the conditions of such a reaction are then respected. In addition, the permanent presence of water in large quantities at the cathode favors the reaction.
• corrosion can be accentuated during the stop / start phases or power cycles of the battery.
• the membrane is not perfectly impermeable to gases.
• oxygen diffuses through the membrane to reach the anode.
• the amount of dihydrogen available may be insufficient to react with the oxygen at the anode.
• the oxygen at the anode then reacts with the protons generated by the corrosion reaction. This oxygen acts as a proton pump and accentuates the phenomenon of corrosion.
• the corrosion of the carbon support reduces the catalytic surface of the cathode, induces the separation of platinum particles from the support, and increases the electrical contact resistance between the cathode and its gaseous diffusion layer.
• JP2005317492A discloses a proton exchange membrane fuel cell for minimizing the amount of catalyst material.
• the thickness of the catalyst layer on the anode is decreased stepwise between fuel inlet and outlet zones. Such anode is difficult to achieve without a really prohibitive cost.
• the invention thus relates to a fuel cell, comprising:
• anode and a cathode fixed on either side of the proton exchange membrane the anode delimiting a flow conduit between a dihydrogen entry zone and a hydrogen exit zone and having a quantity of catalyst at the level of the hydrogen output lower than the amount of catalyst at the dihydrogen input.
• the thickness of the anode decreases continuously between the inlet zone and the exit zone.
• the anode has a catalyst concentration at the inlet zone at least two times greater than the catalyst concentration at the exit zone.
• the anode comprises a catalyst fixed on a support including graphite.
• the cathode delimits a flow conduit between a dioxygen inlet zone and a water outlet zone, the water outlet zone being disposed opposite the zone of entry of dihydrogen.
• FIG 1 is a schematic exploded perspective view of a fuel cell cell
• FIG 2 is a sectional view of a fuel cell cell according to a first embodiment of the invention
• FIG. 3 is a sectional view of a fuel cell cell according to a first variant of the first embodiment
• FIG 4 is a sectional view of a fuel cell cell according to a second variant of the first embodiment.
• the inventors have found that proton exchange membrane fuel cells have a generally higher wear on the cathode at the oxygen inlet.
• the invention provides a fuel cell in which the anode has a catalyst amount at the hydrogen output lower than the amount of catalyst at the dihydrogen input.
• the thickness of the anode decreases continuously between the inlet zone and the exit zone.
• the invention optimally improves the protection against corrosion of the cathode at the oxygen inlet by reducing the possibility of reaction of the oxygen diffused towards the anode through the membrane, without altering the battery performance and with a reasonable cost of production.
• Figure 1 is a schematic exploded perspective view of a cell 1 of a fuel cell.
• Cell 1 is of the proton exchange membrane or polymer electrolyte membrane type.
• the cell 1 of the fuel cell comprises a fuel source 1 1 0 dihydrogen supplying a first inlet 1 68 of the cell.
• the cell 1 also comprises a first outlet 116 for evacuating the excess dihydrogen.
• the cell 1 comprises a flow duct extending between the first inlet and the first outlet.
• the cell 1 also comprises an air source January 1 supplying a second inlet 1 62 of the air cell, the air containing oxygen used as oxidant.
• Cell 1 further includes a second outlet 64 for discharging excess oxygen, reaction water and heat.
• the cell 1 comprises a flow duct extending between the second inlet 1 62 and the second outlet 1 64.
• the cell 1 may also have a cooling circuit not shown.
• Cell 1 comprises an electrolyte layer 1 formed, for example, of a polymer membrane.
• the cell 1 also comprises an anode 1 22 and a cathode 1 24 placed on either side of the electrolyte 1 20 and fixed on the electrolyte 1 20.
• the cell 1 has flow guide plates 142 and 144 arranged opposite the anode 1 22 and the cathode 144.
• the cell 1 furthermore has a gas diffusion layer 1 32 disposed in the flow duct between the anode 122 and the heating plate. 142.
• the cell 1 also has a gas diffusion layer 134 disposed in the flow conduit between the cathode 1 24 and the guide plate 144.
• the plates 142 and 144 comprise faces oriented towards the electrolyte layer 1, respectively comprising zones 1 52 and 154 comprising a set of grooves or channels.
• the zones 1 52 and 1 54 comprising the grooves or channels make it possible to convey respectively the hydrogen and the air inside the cell 1.
• the plates 142 and 144 are made of metal such as stainless steel in a manner known per se.
• the plates 142 and 144 are usually referred to as bipolar plates, the same component generally comprising a guide plate 142 belonging to a cell and a guide plate 144 belonging to an adjacent cell.
• the plates 142 and 144 are conductive and make it possible to collect the current generated by the cell 1.
• the electrolyte layer 1 forms a semipermeable membrane allowing proton conduction while being impermeable to the gases present in the cell 1.
• the electrolyte layer 1 also prevents the electrons from passing between the anode 1 22 and the cathode 1 24.
• the electrolyte layer 1 does not form a perfect barrier to the diffusion of gas, and in particular to the dioxygen diffusion.
• a cell 1 During its operation, a cell 1 usually generates a DC voltage between the anode and the cathode of the order of 1 V.
• the output 1 66 is vis-à-vis the input 1 62
• the input 1 68 is vis-à-vis the output 164.
• the dihydrogen and oxygen flow in opposite directions inside cell 1.
• the diffusion of oxygen is particularly critical at the level of the entry 162, this zone being the most subject to corrosion. Indeed, at the inlet 162, only a limited portion of this oxygen has then reacted at the cathode 124, and the inlet 162 is at the outlet of hydrogen evacuation anode side 122, and therefore at the level of an area where the amount of dihydrogen that can react with the diffused oxygen is reduced.
• FIG. 2 is a diagrammatic sectional view of the cell 1 of the fuel cell according to a first embodiment of the invention.
• Anode 122 has a homogeneous catalyst concentration.
• the thickness of the anode 122 at the outlet 166 is, however, less than its thickness at the inlet 168.
• the amount of catalyst at the outlet 166 is less than the amount of catalyst at the the inlet 168.
• the thickness of the anode 122 can decrease continuously between the inlet 168 and the outlet 166.
• the thickness of the anode 122 can also decrease exponentially.
• Such a configuration makes it possible to obtain an anode 122 having distinct quantities of catalyst at the inlet and the fuel outlet and at a relatively limited cost.
• the anode 122 generally comprises a catalyst layer including, for example, a catalyst such as platinum supported by a graphite support and a proton-conducting ionomer, for example the product distributed under the commercial reference Nafion. Platinum is used for its catalyst properties.
• a catalyst layer including, for example, a catalyst such as platinum supported by a graphite support and a proton-conducting ionomer, for example the product distributed under the commercial reference Nafion. Platinum is used for its catalyst properties.
• the formation of such anode 122 may be performed by inkjet printing methods.
• the thickness of the membrane 120 at the oxygen inlet 162 is greater than its thickness at the outlet 164.
• the portion of the membrane 120 at the level of the The input has a proton resistance greater than its proton resistance at the output 164. Thus, the diffusion of the oxygen at the input 162 is reduced.
• the membrane 120 By using a lower thickness of the membrane 120 at the level of the outlet 164, it is preferred to pass through the protons in a zone of the cathode 124 that is less critical in terms of corrosion. Thus, the performance of the cell 1 is only marginally reduced for a gain in long life.
• the membrane 120 has a thickness which decreases continuously between the inlet 162 and the outlet 164.
• a membrane 1 can be made particularly easily, for example by a method of casting combined with evaporation, which makes it possible to easily control the local thickness of the membrane 120.
• Such variation in thickness can be achieved by locally depositing a greater or lesser amount of material during casting.
• the thickness of the membrane 120 at the inlet 162 is at least 40% greater than the thickness of the membrane 120 at the outlet 164.
• the cathode 124 generally comprises a catalyst layer including, for example, platinum fixed on a graphite support and a proton-conducting ionomer. Platinum is used for its catalyst properties.
• the cathode 124 may have a homogeneous composition and thickness.
• the anode 122 and the cathode 124 may for example comprise supports made by combining aggregates of carbon and ionomers. Platinum nanoparticles are then fixed on these aggregates.
• the ionomer of the cathode or anode may be identical to the ionomer used to form the membrane.
• the cathode 124 and the anode 122 may be made by applying an ink to the membrane 120 or a respective gas diffusion layer.
• the ink may typically comprise the combination of a solvent, an ionomer and platinum carbon.
• the gas diffusion layer 132 serves to diffuse dihydrogen from a flow channel of the plate 142 to the anode 122.
• the gas diffusion layer 134 serves to diffuse air from a flow channel of the plate 144 to the cathode 124.
• the gas diffusion layers 132 and 134 may, for example, be produced in a manner known per se in the form of fiber, felt or graphite fabric to which a hydrophobic agent such as polytetrafluoroethylene is attached.
• the gas diffusion layers 132 and 134 have a thickness at least 5 times greater than the thickness of the assembly, including the membrane 120, the anode 122 and the cathode 124.
• the gas diffusion layers 132 and 134 being in fact generally compressible, these then allow to absorb the thickness heterogeneity of the membrane-electrode assembly.
• the gas diffusion layers 132 and 134 may, for example, have a thickness of between 200 and 500 ⁇ m.
• the cathode 124 comprises a support of the catalyst material including a first graphite material on which the catalyst is fixed.
• the cathode support 124 also includes a second material to which the catalyst is attached, the second material having an oxygen corrosion resistance greater than the strength of the graphite material.
• the quantity of this second material at the entry of oxygen 162 is greater than the quantity of this second material at the outlet 164. This reduces the corrosion phenomenon of the cathode 124 without unduly altering the cost price of the cell.
• the second material may for example include fullerene, doped SnO2 or doped T1O2. This second material will have to allow a diffusion of the gases and a diffusion of the protons. By limiting the use of this second material to the necessary areas, the cost price of the cathode 124 is included.
• the cathode 124 comprises two layers Z5 and Z6.
• the layers Z5 and Z6 are superimposed in the direction of their thickness.
• the Z5 layer has a homogeneous concentration of reinforced material.
• the Z6 layer has a homogeneous concentration of graphite material.
• the thickness of the layer Z5 decreases continuously between the input 162 and the output 164.
• the thickness of the layer Z6 increases continuously between the input 162 and the output 164.
• the assembly of the layers Z5 and Z6 has a constant thickness.
• cathode 124 having a layer having a decreasing concentration of reinforced material between the inlet 162 and the outlet 164.

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• 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)

Applications Claiming Priority (2)

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• 2011
  • 2011-03-31 FR FR1152743A patent/FR2973581A1/fr not_active Withdrawn
• 2012
  • 2012-03-29 EP EP12711866.9A patent/EP2692009A1/fr not_active Withdrawn
  • 2012-03-29 JP JP2014501616A patent/JP2014512646A/ja not_active Ceased
  • 2012-03-29 US US14/008,641 patent/US20140099565A1/en not_active Abandoned
  • 2012-03-29 WO PCT/EP2012/055619 patent/WO2012130932A1/fr active Application Filing
  • 2012-03-29 KR KR1020137028093A patent/KR20140020297A/ko not_active Application Discontinuation

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