CA2668895A1 - Electrocatalyst layers for fuel cells and methods of making electrocatalyst layers for fuel cells - Google Patents
Electrocatalyst layers for fuel cells and methods of making electrocatalyst layers for fuel cells Download PDFInfo
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- CA2668895A1 CA2668895A1 CA002668895A CA2668895A CA2668895A1 CA 2668895 A1 CA2668895 A1 CA 2668895A1 CA 002668895 A CA002668895 A CA 002668895A CA 2668895 A CA2668895 A CA 2668895A CA 2668895 A1 CA2668895 A1 CA 2668895A1
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- 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
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- 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
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- 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
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- 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
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- 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]
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- 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
Abstract
An electrochemical fuel cell is disclosed. The electrochemical fuel cell comprises a membrane electrode assembly comprising: an anode having an anode gas diffusion layer and an anode electrocatalyst layer; a cathode having a cathode gas diffusion layer and a cathode electrocatalyst layer; and a proton exchange membrane disposed between the anode and the cathode. At least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises an electrocatalyst and polyfurfuryl alcohol. The polyfurfuryl alcohol may be distributed uniformly or non-uniformly within the electrocatalyst layer. Methods of making the electrocatalyst layer having an electrocatalyst and polyfurfuryl alcohol are also disclosed.
Description
ELECTROCATALYST LAYERS FOR FUEL CELLS AND METHODS
OF MAKING ELECTROCATALYST LAYERS FOR FUEL CELLS
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit under 35 U.S.C. 119(e) of U.S.
Provisional Patent Application No. 60/864,877, filed November 8, 2006, where this provisional application is incorporated herein by reference in their entireties.
BACKGROUND
Technical Field The present disclosure generally relates to electrocatalyst layers and electrochemical fuel cells, and to methods of making electrocatalyst layers for electrochemical fuel cells.
Description of the Related Art Electrochemical fuel cells convert reactants, namely fuel and oxidant fluid streams, to generate electric power and reaction products.
Electrochemical fuel cells generally employ a membrane electrode assembly (MEA) disposed between two separator plates that are substantially impermeable to the reactant fluid streams. The plates typically act as current collectors and provide support for the MEA. In addition, the plates may have reactant channels formed therein and act as flow field plates providing access for the reactant fluid streams, such as hydrogen gas and air, to the MEA and providing for the removal of reaction products formed during operation of the fuel cell. Typically, a number of fuel cells are electrically coupled in series to form a fuel cell stack.
One type of electrochemical fuel cells is the polymer electrolyte membrane (PEM) fuel cell, which employs an MEA comprising a solid polymer electrolyte or ion-exchange membrane. The membrane acts both as a barrier for isolating the reactant streams from each other and as an electrical insulator between the two electrodes. A typical commercial PEM is a sulfonated perfluorocarbon membrane sold by E.I. Du Pont de Nemours and Company under the trade designation Nafion .
The MEA further comprises two electrodes, each electrode disposed on opposing surfaces of the ion-exchange membrane. Each electrode typically comprises a porous, electrically conductive substrate, such as carbon fiber paper or carbon cloth, which provides structural support to the membrane and serves as a gas diffusion layer.
Typically, the gas diffusion layer also contains a sublayer of carbon particles with an optional binder. The electrodes further comprise an electrocatalyst, disposed between the membrane and the gas diffusion layers, which is typically a precious metal composition (e.g., platinum metal black or an alloy thereof) and may be provided on a suitable electrocatalyst support (e.g., fine platinum particles supported on a carbon black support). The electrocatalyst may also contain an ionomer to improve proton conduction through the electrode.
The electrode typically contains a hydrophobic material such as polytetrafluoroethylene (PTFE) to impart water management properties to the electrode.
Water management is a key property of the electrode because water is produced during fuel cell operation. Without adequate water removal, the product water may accumulate, creating performance losses due to increased mass transport losses, particularly at high current densities where a relatively large amount of water is produced.
However, the use of PTFE has been limited when used in electrocatalyst compositions containing an ionomer because PTFE is hydrophobic in nature and does not uniformly mix with the ionomer, which is hydrophilic. In addition, the high sintering temperatures required for PTFE to "flow" into the fluid diffusion layer and/or the electrocatalyst damages or destroys most ionomers.
Accordingly, although there have been advances in the field, there remains a need in the art for electrocatalyst layers with improved water management properties. The present invention addresses these needs and provides further related advantages.
OF MAKING ELECTROCATALYST LAYERS FOR FUEL CELLS
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit under 35 U.S.C. 119(e) of U.S.
Provisional Patent Application No. 60/864,877, filed November 8, 2006, where this provisional application is incorporated herein by reference in their entireties.
BACKGROUND
Technical Field The present disclosure generally relates to electrocatalyst layers and electrochemical fuel cells, and to methods of making electrocatalyst layers for electrochemical fuel cells.
Description of the Related Art Electrochemical fuel cells convert reactants, namely fuel and oxidant fluid streams, to generate electric power and reaction products.
Electrochemical fuel cells generally employ a membrane electrode assembly (MEA) disposed between two separator plates that are substantially impermeable to the reactant fluid streams. The plates typically act as current collectors and provide support for the MEA. In addition, the plates may have reactant channels formed therein and act as flow field plates providing access for the reactant fluid streams, such as hydrogen gas and air, to the MEA and providing for the removal of reaction products formed during operation of the fuel cell. Typically, a number of fuel cells are electrically coupled in series to form a fuel cell stack.
One type of electrochemical fuel cells is the polymer electrolyte membrane (PEM) fuel cell, which employs an MEA comprising a solid polymer electrolyte or ion-exchange membrane. The membrane acts both as a barrier for isolating the reactant streams from each other and as an electrical insulator between the two electrodes. A typical commercial PEM is a sulfonated perfluorocarbon membrane sold by E.I. Du Pont de Nemours and Company under the trade designation Nafion .
The MEA further comprises two electrodes, each electrode disposed on opposing surfaces of the ion-exchange membrane. Each electrode typically comprises a porous, electrically conductive substrate, such as carbon fiber paper or carbon cloth, which provides structural support to the membrane and serves as a gas diffusion layer.
Typically, the gas diffusion layer also contains a sublayer of carbon particles with an optional binder. The electrodes further comprise an electrocatalyst, disposed between the membrane and the gas diffusion layers, which is typically a precious metal composition (e.g., platinum metal black or an alloy thereof) and may be provided on a suitable electrocatalyst support (e.g., fine platinum particles supported on a carbon black support). The electrocatalyst may also contain an ionomer to improve proton conduction through the electrode.
The electrode typically contains a hydrophobic material such as polytetrafluoroethylene (PTFE) to impart water management properties to the electrode.
Water management is a key property of the electrode because water is produced during fuel cell operation. Without adequate water removal, the product water may accumulate, creating performance losses due to increased mass transport losses, particularly at high current densities where a relatively large amount of water is produced.
However, the use of PTFE has been limited when used in electrocatalyst compositions containing an ionomer because PTFE is hydrophobic in nature and does not uniformly mix with the ionomer, which is hydrophilic. In addition, the high sintering temperatures required for PTFE to "flow" into the fluid diffusion layer and/or the electrocatalyst damages or destroys most ionomers.
Accordingly, although there have been advances in the field, there remains a need in the art for electrocatalyst layers with improved water management properties. The present invention addresses these needs and provides further related advantages.
BRIEF SUMMARY
In brief, the present disclosure generally relates to electrocatalyst layers and electrochemical fuel cells, and to methods of making electrocatalyst layers for electrochemical fuel cells.
In one embodiment, membrane electrode assembly comprises: an anode having an anode gas diffusion layer and an anode electrocatalyst layer; a cathode having a cathode gas diffusion layer and a cathode electrocatalyst layer; and a proton exchange membrane disposed between the anode and the cathode; wherein at least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises polyfurfuryl alcohol. In some embodiments, the cathode electrocatalyst layer comprises a platinum alloy catalyst and an ionomer. In other embodiments, the distribution of polyfurfuryl alcohol is non-uniform.
In another embodiment, a method of making an electrode for an electrochemical fuel cell comprises the steps of: applying an electrocatalyst composition to a sheet material; adding monomeric furfuryl alcohol to the electrocatalyst composition; and polymerizing the monomeric furfuryl alcohol after adding monomeric furfuryl alcohol and applying the catalyst composition.
These and other aspects of the invention will be evident upon reference to the following detailed description and attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawing, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawing are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
In brief, the present disclosure generally relates to electrocatalyst layers and electrochemical fuel cells, and to methods of making electrocatalyst layers for electrochemical fuel cells.
In one embodiment, membrane electrode assembly comprises: an anode having an anode gas diffusion layer and an anode electrocatalyst layer; a cathode having a cathode gas diffusion layer and a cathode electrocatalyst layer; and a proton exchange membrane disposed between the anode and the cathode; wherein at least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises polyfurfuryl alcohol. In some embodiments, the cathode electrocatalyst layer comprises a platinum alloy catalyst and an ionomer. In other embodiments, the distribution of polyfurfuryl alcohol is non-uniform.
In another embodiment, a method of making an electrode for an electrochemical fuel cell comprises the steps of: applying an electrocatalyst composition to a sheet material; adding monomeric furfuryl alcohol to the electrocatalyst composition; and polymerizing the monomeric furfuryl alcohol after adding monomeric furfuryl alcohol and applying the catalyst composition.
These and other aspects of the invention will be evident upon reference to the following detailed description and attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawing, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawing are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
Figure 1 is a schematic illustration of a membrane electrode assembly.
Figure 2 is a graph showing polarization curves for fuel cells having a platinum electrocatalyst and a platinum-cobalt alloy electrocatalyst for the cathode electrode, both in combination with a Nafion ionomer.
DETAILED DESCRIPTION
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the present description.
However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures associated with fuel cells, fuel cell stacks, and fuel cell systems have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.
Unless the context requires otherwise, throughout the specification and claims which follow, the word "comprise" and variations thereof, such as "comprises"
and "comprising" are to be construed in an open, inclusive sense, that is as "including, but not limited to".
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present description. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Figure 1 shows a schematic illustration of an exemplary membrane electrode assembly 10 ("MEA"). As mentioned earlier, MEAs typically include electrocatalyst layers 12,14 disposed between gas diffusion layers 16,18 ("GDL") and a proton exchange membrane 20 ("PEM"). Electrocatalyst layers 12,14 usually contain an electrocatalyst, such as a noble metal, non-noble metal, and/or alloys thereof, combined with an ionomer to increase proton conductivity within the electrocatalyst layers. GDLs 16,18 typically includes a substrate 22,24, such as carbon fiber paper, and an optional sublayer 26,28, such as a layer comprising carbonaceous particles and a binder, for example, PTFE and/or an ionomer.
As mentioned earlier, an important property of the electrocatalyst layer is water management because it has a large influence on performance. If the electrocatalyst layer cannot adequately remove excess product water, fuel cell performance will be adversely affected due to excessive mass transport losses, particularly when operating with air as the oxidant at high current densities where large amounts of water are produced. In particular, it has been found that certain electrocatalysts, such as platinum-cobalt alloy electrocatalysts, have lower kinetic losses than pure platinum catalysts. This performance gain is not realized, however, with increasing current densities.
As shown in Figure 2, two MEAs having the same anode electrode and same membrane, but different cathode electrocatalysts, were tested for fuel cell performance. The anode electrocatalyst was platinum on a graphite support and the loading was 0.1 mg Pt/cm2. The membrane was NRE211, a Nafiori -based polymer electrolyte membrane supplied by E.I. Du Pont de Nemours and Company. The cathode electrocatalyst for one of the MEAs was platinum on a graphite support and mixed with a Nafion binder, while the cathode electrocatalyst for the other MEA was a platinum-cobalt alloy on a graphite support and mixed with a Nafiori binder. Both of these cathodes had a loading of 0.4 mg Pt/cm2. At 1.0 A/cm2, the testing conditions were as follows:
Fuel type 80% H2, balance N2 Fuel stoichiometry 1.8 Fuel pressure 2.2 bara Fuel relative humidity 60%
Air stoichiometry 1.8 Air ressure 2.0 bara Air relative humidity 60%
Coolant Inlet Temperature 65 C
Coolant Outlet Temperature 79 C
Figure 2 is a graph showing polarization curves for fuel cells having a platinum electrocatalyst and a platinum-cobalt alloy electrocatalyst for the cathode electrode, both in combination with a Nafion ionomer.
DETAILED DESCRIPTION
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the present description.
However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures associated with fuel cells, fuel cell stacks, and fuel cell systems have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.
Unless the context requires otherwise, throughout the specification and claims which follow, the word "comprise" and variations thereof, such as "comprises"
and "comprising" are to be construed in an open, inclusive sense, that is as "including, but not limited to".
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present description. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Figure 1 shows a schematic illustration of an exemplary membrane electrode assembly 10 ("MEA"). As mentioned earlier, MEAs typically include electrocatalyst layers 12,14 disposed between gas diffusion layers 16,18 ("GDL") and a proton exchange membrane 20 ("PEM"). Electrocatalyst layers 12,14 usually contain an electrocatalyst, such as a noble metal, non-noble metal, and/or alloys thereof, combined with an ionomer to increase proton conductivity within the electrocatalyst layers. GDLs 16,18 typically includes a substrate 22,24, such as carbon fiber paper, and an optional sublayer 26,28, such as a layer comprising carbonaceous particles and a binder, for example, PTFE and/or an ionomer.
As mentioned earlier, an important property of the electrocatalyst layer is water management because it has a large influence on performance. If the electrocatalyst layer cannot adequately remove excess product water, fuel cell performance will be adversely affected due to excessive mass transport losses, particularly when operating with air as the oxidant at high current densities where large amounts of water are produced. In particular, it has been found that certain electrocatalysts, such as platinum-cobalt alloy electrocatalysts, have lower kinetic losses than pure platinum catalysts. This performance gain is not realized, however, with increasing current densities.
As shown in Figure 2, two MEAs having the same anode electrode and same membrane, but different cathode electrocatalysts, were tested for fuel cell performance. The anode electrocatalyst was platinum on a graphite support and the loading was 0.1 mg Pt/cm2. The membrane was NRE211, a Nafiori -based polymer electrolyte membrane supplied by E.I. Du Pont de Nemours and Company. The cathode electrocatalyst for one of the MEAs was platinum on a graphite support and mixed with a Nafion binder, while the cathode electrocatalyst for the other MEA was a platinum-cobalt alloy on a graphite support and mixed with a Nafiori binder. Both of these cathodes had a loading of 0.4 mg Pt/cm2. At 1.0 A/cm2, the testing conditions were as follows:
Fuel type 80% H2, balance N2 Fuel stoichiometry 1.8 Fuel pressure 2.2 bara Fuel relative humidity 60%
Air stoichiometry 1.8 Air ressure 2.0 bara Air relative humidity 60%
Coolant Inlet Temperature 65 C
Coolant Outlet Temperature 79 C
It is believed that electrocatalyst layers having a platinum-cobalt alloy tend to have higher mass transport loss at high current densities than electrocatalyst layers containing pure platinum due to water retention. Thus, incorporation of a hydrophobic additive, which is compatible with the catalyst layer components, into such an electrocatalyst layer decreases water retention and enhances fuel cell performance at high current densities.
Polyfurfuryl alcohol (PFA) has been found to be a particularly suitable hydrophobic additive for electrocatalyst layers for electrochemical fuel cells because it polymerizes at a temperature below the decomposition temperature of most ionomers, such as Nafion . The literature has shown that Nafiori membranes for direct methanol fuel cells have been made by in-situ acid-catalyzed polymerization of furfuryl alcohol within Nafion structures. It has been suggested that the hydrophilic nature of the monomeric furfuryl alcohol allows uniform and thorough penetration into the hydrophilic structure of Nafion , thereby forming a Nafiori -PFA nanocomposite membrane with reduced methanol permeation. Methanol permeation problems are encountered in direct methanol fuel cells due to the use of liquid methanol fuels, but not for fuel cells operating on gaseous fuels, such as hydrogen gas.
Without being bound by theory, when PFA is employed in the electrocatalyst layer having an ionomer, PFA imparts at least partial hydrophobicity within its relatively hydrophilic ionomer network, thus altering the water management properties of the electrocatalyst layer. Furthermore, ion conductivity should not be affected if PFA exists in the appropriate amounts. PFA may also enhance the tensile and/or adhesive strength between the electrocatalyst and the ionomer in the electrocatalyst layer (thereby decreasing dimensional change of the electrocatalyst layer due to hydration/dehydration), and may prevent cracks from forming on the surface of the electrocatalyst layer.
In one embodiment, PFA is uniformly distributed within the electrocatalyst layer. In other embodiments, PFA is non-uniformly distributed within the electrocatalyst layer. For example, the concentration of PFA through the thickness of the electrocatalyst layer may be varied in the z-direction (i.e., from the PEM to the GDL). Additionally, or alternatively, the concentration of the PFA in the electrocatalyst layer may be varied in the xy-direction (i.e., with respect to a surface of the electrocatalyst layer), for example, from an inlet of the fuel cell to the outlet of the fuel cell.
In further embodiments, PFA may also be in a layer form, for example, as a layer between the electrocatalyst layer and the PEM or as a layer between the electrocatalyst layer and the GDL to enhance its hydrophobic properties.
Again, PFA
may be uniformly or non-uniformly distributed in the xy-direction.
The amount of PFA in the resulting electrode after polymerization may range from, for example, about 0.1 wt% of the total ionomer in the electrocatalyst layer to about 20 wt% of the total ionomer in the electrocatalyst layer, depending on its penetration into the ionomer of the electrocatalyst layer. For example, if PFA
is dispersed within the electrocatalyst layer, then the amount of PFA in the resulting electrode after polymerization is preferably less than 8 wt% of the total ionomer in the electrocatalyst layer. This is because it has been shown in the literature that ion conductivity of the membrane is negatively affected if the amount of PFA is greater than 8 wt% of the total ionomer. However, if the PFA is applied as a layer onto the electrocatalyst layer (i.e., between the electrocatalyst layer and the GDL), then the amount of PFA in the resulting electrode after polymerization may be higher, for example, less than 20 wt% of the total ionomer in the electrocatalyst layer, thereby forming a gradient in hydrophobicity in the z-direction of the electrocatalyst layer. A
higher amount of PFA can be tolerated in this case because the affect on proton conductivity through the electrocatalyst layer is not significantly impacted if PFA is applied as a layer and without significant penetration into the electrocatalyst layer.
Methods of making electrocatalyst layers and MEAs using electrocatalyst compositions comprising PFA are discussed hereinbelow.
The electrocatalyst composition typically comprises an electrocatalyst, such as a noble metal, for example, platinum, ruthenium, and iridium; a non-noble metal, for example, cobalt, nickel, iron, chromium, and tungsten; or combinations or alloys thereof. In specific embodiments, the electrocatalyst is a platinum-cobalt alloy.
In other embodiments, the electrocatalyst may be a non-noble metal, such as those described in published U.S. Appl. No. 2004/0096728. The electrocatalyst may be supported on an electrically conductive material, such as a carbonaceous or graphitic support material, for example, a carbon black or carbide, or other oxidatively stable supports. The electrocatalyst composition may optionally include a pore former, such as methyl cellulose, durene, camphene, camphor, and naphthalene, that is removed in the process of making the electrocatalyst layer to increase the porosity thereof. In addition, the electrocatalyst composition may optionally contain an ionomer, such as, but not limited to, a perfluorinated ionomer, a partially fluorinated ionomer, or a non-fluorinated ionomer; and an optional solvent, for example, a polar aprotic solvent, such as N-methylpyrrolidinone, dimethylsulfoxide, and N,N-dimethylacetamide.
Furthermore, the electrocatalyst composition may optionally include other additives, such as carbonaceous particles and carbon nanotubes and/or nanofibres.
In one embodiment, monomeric furfuryl alcohol is mixed with the electrocatalyst composition by any method known in the art, such as stirring, shear mixing, microfluidizing, and ultrasonic mixing. The monomeric furfuryl alcohol may be employed in the form of a neat solution or dispersed in a solvent, such as isopropanol, ethanol, methanol, deionized water, or mixtures thereof, before adding to the electrocatalyst composition. Optionally, an acid catalyst may be added to the electrocatalyst composition to induce and/or enhance the polymerization process.
The electrocatalyst composition may be applied onto a sheet material by any method known in the art, such as knife-coating, slot-die coating, dip-coating, microgravure coating, spraying, and screen-printing. In one embodiment, the sheet material is the surface of the electrocatalyst layer. In other embodiments, the sheet material may be a transfer material such as polytetrafluoroethylene, polyester, and polyimide sheet materials that can be used to decal transfer the electrocatalyst layer to a surface of the GDL to form a gas diffusion electrode, or to a surface of the PEM to form a catalyst-coated membrane (CCM).
In another embodiment, the electrocatalyst composition may be applied onto a surface of the sheet material to form an electrocatalyst layer, and then monomeric furfuryl alcohol is applied onto a surface of the electrocatalyst layer by any method known in the art, such as those described above. In some embodiments, monomeric furfuryl alcohol may also be applied to the surface of the sheet material before application of the electrocatalyst composition.
In this embodiment, the monomeric furfuryl alcohol and electrocatalyst layer may be subjected to impregnation conditions prior to polymerization to create a non-uniform distribution of furfiuyl alcohol in the electrocatalyst layer, for example, a gradient of furfuryl alcohol through the thickness of the electrocatalyst layer. In further embodiments, monomeric furfuryl alcohol may be homogeneously impregnated into the electrocatalyst layer by using a sufficient amount of monomeric furfuryl alcohol and/or subjecting the monomeric furfuryl alcohol and electrocatalyst layer to the appropriate impregnation conditions. Impregnation of the monomeric furfuryl alcohol into the electrocatalyst layer may be controlled by varying the amount of furfuryl alcohol and/or the impregnation conditions, such as the impregnation temperature and time, to achieve the desired gradient through the thickness of the electrocatalyst layer.
Polymerization of the monomeric furfuryl alcohol may occur before and/or during bonding of the MEA. For example, the monomeric furfuryl alcohol may be polymerized during or after application to the sheet material, and before assembling the MEA. Alternatively, polymerization occurs simultaneously with bonding of the MEA components by assembling an MEA with an electrocatalyst layer containing monomeric (unpolymerized) furfuryl alcohol and then subjecting the MEA to bonding conditions that are similar to the required polymerization conditions. In yet another example, the monomeric furfuryl alcohol may be partially polymerized during or after application to the sheet material, and then further polymerized during MEA
bonding.
The polymerization conditions may include a polymerization temperature, for example, heating to a temperature of between about 80 C and about 140 C, and a polymerization time of about 5 seconds to about 15 minutes. The polymerization time will be dependent on the polymerization temperature and the amount of furfuryl alcohol. For instance, the polymerization time from about 5 to 10 minutes for a low polymerization temperature and a high amount of furfuryl alcohol, but may range from about 1 to 2 minutes for a high polymerization temperature and a low amount of furfuryl alcohol. In some instances, the furfuryl alcohol may be cross-linked by exposure to ultraviolet rays, for example, by exposure to a mercury lamp.
In some embodiments, the amount of furfuryl alcohol and/or degree of polymerization of the furfuryl alcohol in or on the electrocatalyst layer is non-uniform in the xy-direction to preferentially control the hydrophobic properties in different regions of the fuel cell. In one embodiment, a higher concentration of monomeric furfuryl alcohol and/or a greater degree of polymerization of the monomeric furfuryl alcohol may be employed in regions of the electrocatalyst layer that tends to be wetter during fuel cell operation (for example, the outlet region of the fuel cell in comparison to the inlet region) to improve water removal therefrom. Further, the loading of the electrocatalyst composition with monomeric furfuryl alcohol may be varied when it is applied to the sheet material. In another example, the loading of monomeric furfuryl alcohol may be varied when it is applied to the electrocatalyst layer. In yet another example, the polymerization conditions may be varied along the xy-direction of the electrocatalyst layer to vary the degree of polymerization.
In further embodiments, an ionomer layer may also be employed between the PEM and electrocatalyst layer and/or between the electrocatalyst layer and GDL. The ionomer layer may also contain monomeric furfuryl alcohol and then polymerized after application to a surface of the PEM and/or the electrocatalyst layer, for example, polymerizing immediately after application or polymerizing during MEA
bonding. Again, the ionomer layer may be applied by any method known in the art, such as those described above, and may be uniform or non-uniform with respect to the planar surface of the catalyst layer.
The following examples are provided for the purpose of illustration, not limitation.
Example 1 Polymerization of furfuryl alcohol to form an electrode An electrocatalyst composition is made by mixing 662 grams of 10% by weight Nafion solution with 132 grams of a platinum-containing catalyst powder, 2 grams of monomeric furfuryl alcohol, 6 grams of isopropanol, and 290 grams of de-ionized water. The mixture is then mixed using an ultrasonic mixer and then sprayed onto a fluid diffusion layer comprising a carbon fiber paper and a microporous carbonaceous layer. The resulting electrode is then subjected to a temperature of about 140 C for about 2 to 10 minutes to polymerize the monomeric furfuryl alcohol, thereby producing an electrode with PFA.
Example 2 Polymerization of furfuryl alcohol to form a catalyst-coated membrane A solution of monomeric furfuryl alcohol is prepared by mixing 6 grams of monomeric furfuryl alcohol with 12 grams of isopropanol and 6 grams of de-ionized water. The solution is then sprayed onto the cathode electrocatalyst layer of a CCM.
The monomeric furfuryl alcohol is allowed to penetrate into the cathode electrocatalyst layer for about 1 hour at 20 C. After penetration, the CCM is heated to about 140 C for about 2 to about 10 minutes to polymerize the monomeric furfuryl alcohol, thereby producing a CCM with PFA in the cathode electrocatalyst layer.
Example 3 Polymerization of furfuryl alcohol as a layer on a carbon/Nafiori subla yer A solution of monomeric furfuryl alcohol was prepared by mixing 6 grams of monomeric furfuryl alcohol (98% Lancaster) with 12 grams of isopropanol and 6 grams of de-ionized water. The solution was then sprayed at room temperature onto a GDL having a sublayer containing carbon black and Nafion on one surface of the substrate. The sprayed GDL was then placed onto a hot plate at 140 C for about 10 minutes to polymerize the furfuryl alcohol. The final loading of PFA was about 45wt%.
The polymerized GDL was then subjected to a mercury intrusion porosimetry test using the Autopore III supplied by Micromeritics Instrument Corporation, and a series of through-plane permeability tests using the 58-21 Roughness and Air Permeance Tester supplied by Testing Machines (TMI Inc.). (A through-hole was bored through the bottom jig of the tester and a rubber seal was placed around the test piece so that air was forced from the top jig to the bottom jig through the test piece.) Mercury intrusion porosimetry tests showed that the average pore diameter shifted from about 0.67 microns with no PFA to 1.11 microns with PFA, while through-plane permeability tests showed that the air permeability increase from an average of 129 mL/min with no PFA to an average of 183 mL/min with PFA. The furfuryl alcohol likely shrinks as it polymerizes, thus pulling the pores wider apart and increasing the size and through-plane permeability thereof. This increase in pore size and through-plane permeability may improve water removal and reactant accessibility when PFA is employed in the electrocatalyst layer, in addition to increasing the hydrophobicity of the electrocatalyst layer.
All of the above U.S. patents, U.S. patent application publications, U.S.
patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
While particular steps, elements, embodiments and applications of the present invention have been shown and described herein for purposes of illustration, it will be understood, of course, that the description is not limited thereto since modifications may be made by persons skilled in the art, particularly in light of the foregoing teachings, without deviating from the spirit and scope of the present disclosure. Accordingly, the invention is not limited except as by the appended claims.
Polyfurfuryl alcohol (PFA) has been found to be a particularly suitable hydrophobic additive for electrocatalyst layers for electrochemical fuel cells because it polymerizes at a temperature below the decomposition temperature of most ionomers, such as Nafion . The literature has shown that Nafiori membranes for direct methanol fuel cells have been made by in-situ acid-catalyzed polymerization of furfuryl alcohol within Nafion structures. It has been suggested that the hydrophilic nature of the monomeric furfuryl alcohol allows uniform and thorough penetration into the hydrophilic structure of Nafion , thereby forming a Nafiori -PFA nanocomposite membrane with reduced methanol permeation. Methanol permeation problems are encountered in direct methanol fuel cells due to the use of liquid methanol fuels, but not for fuel cells operating on gaseous fuels, such as hydrogen gas.
Without being bound by theory, when PFA is employed in the electrocatalyst layer having an ionomer, PFA imparts at least partial hydrophobicity within its relatively hydrophilic ionomer network, thus altering the water management properties of the electrocatalyst layer. Furthermore, ion conductivity should not be affected if PFA exists in the appropriate amounts. PFA may also enhance the tensile and/or adhesive strength between the electrocatalyst and the ionomer in the electrocatalyst layer (thereby decreasing dimensional change of the electrocatalyst layer due to hydration/dehydration), and may prevent cracks from forming on the surface of the electrocatalyst layer.
In one embodiment, PFA is uniformly distributed within the electrocatalyst layer. In other embodiments, PFA is non-uniformly distributed within the electrocatalyst layer. For example, the concentration of PFA through the thickness of the electrocatalyst layer may be varied in the z-direction (i.e., from the PEM to the GDL). Additionally, or alternatively, the concentration of the PFA in the electrocatalyst layer may be varied in the xy-direction (i.e., with respect to a surface of the electrocatalyst layer), for example, from an inlet of the fuel cell to the outlet of the fuel cell.
In further embodiments, PFA may also be in a layer form, for example, as a layer between the electrocatalyst layer and the PEM or as a layer between the electrocatalyst layer and the GDL to enhance its hydrophobic properties.
Again, PFA
may be uniformly or non-uniformly distributed in the xy-direction.
The amount of PFA in the resulting electrode after polymerization may range from, for example, about 0.1 wt% of the total ionomer in the electrocatalyst layer to about 20 wt% of the total ionomer in the electrocatalyst layer, depending on its penetration into the ionomer of the electrocatalyst layer. For example, if PFA
is dispersed within the electrocatalyst layer, then the amount of PFA in the resulting electrode after polymerization is preferably less than 8 wt% of the total ionomer in the electrocatalyst layer. This is because it has been shown in the literature that ion conductivity of the membrane is negatively affected if the amount of PFA is greater than 8 wt% of the total ionomer. However, if the PFA is applied as a layer onto the electrocatalyst layer (i.e., between the electrocatalyst layer and the GDL), then the amount of PFA in the resulting electrode after polymerization may be higher, for example, less than 20 wt% of the total ionomer in the electrocatalyst layer, thereby forming a gradient in hydrophobicity in the z-direction of the electrocatalyst layer. A
higher amount of PFA can be tolerated in this case because the affect on proton conductivity through the electrocatalyst layer is not significantly impacted if PFA is applied as a layer and without significant penetration into the electrocatalyst layer.
Methods of making electrocatalyst layers and MEAs using electrocatalyst compositions comprising PFA are discussed hereinbelow.
The electrocatalyst composition typically comprises an electrocatalyst, such as a noble metal, for example, platinum, ruthenium, and iridium; a non-noble metal, for example, cobalt, nickel, iron, chromium, and tungsten; or combinations or alloys thereof. In specific embodiments, the electrocatalyst is a platinum-cobalt alloy.
In other embodiments, the electrocatalyst may be a non-noble metal, such as those described in published U.S. Appl. No. 2004/0096728. The electrocatalyst may be supported on an electrically conductive material, such as a carbonaceous or graphitic support material, for example, a carbon black or carbide, or other oxidatively stable supports. The electrocatalyst composition may optionally include a pore former, such as methyl cellulose, durene, camphene, camphor, and naphthalene, that is removed in the process of making the electrocatalyst layer to increase the porosity thereof. In addition, the electrocatalyst composition may optionally contain an ionomer, such as, but not limited to, a perfluorinated ionomer, a partially fluorinated ionomer, or a non-fluorinated ionomer; and an optional solvent, for example, a polar aprotic solvent, such as N-methylpyrrolidinone, dimethylsulfoxide, and N,N-dimethylacetamide.
Furthermore, the electrocatalyst composition may optionally include other additives, such as carbonaceous particles and carbon nanotubes and/or nanofibres.
In one embodiment, monomeric furfuryl alcohol is mixed with the electrocatalyst composition by any method known in the art, such as stirring, shear mixing, microfluidizing, and ultrasonic mixing. The monomeric furfuryl alcohol may be employed in the form of a neat solution or dispersed in a solvent, such as isopropanol, ethanol, methanol, deionized water, or mixtures thereof, before adding to the electrocatalyst composition. Optionally, an acid catalyst may be added to the electrocatalyst composition to induce and/or enhance the polymerization process.
The electrocatalyst composition may be applied onto a sheet material by any method known in the art, such as knife-coating, slot-die coating, dip-coating, microgravure coating, spraying, and screen-printing. In one embodiment, the sheet material is the surface of the electrocatalyst layer. In other embodiments, the sheet material may be a transfer material such as polytetrafluoroethylene, polyester, and polyimide sheet materials that can be used to decal transfer the electrocatalyst layer to a surface of the GDL to form a gas diffusion electrode, or to a surface of the PEM to form a catalyst-coated membrane (CCM).
In another embodiment, the electrocatalyst composition may be applied onto a surface of the sheet material to form an electrocatalyst layer, and then monomeric furfuryl alcohol is applied onto a surface of the electrocatalyst layer by any method known in the art, such as those described above. In some embodiments, monomeric furfuryl alcohol may also be applied to the surface of the sheet material before application of the electrocatalyst composition.
In this embodiment, the monomeric furfuryl alcohol and electrocatalyst layer may be subjected to impregnation conditions prior to polymerization to create a non-uniform distribution of furfiuyl alcohol in the electrocatalyst layer, for example, a gradient of furfuryl alcohol through the thickness of the electrocatalyst layer. In further embodiments, monomeric furfuryl alcohol may be homogeneously impregnated into the electrocatalyst layer by using a sufficient amount of monomeric furfuryl alcohol and/or subjecting the monomeric furfuryl alcohol and electrocatalyst layer to the appropriate impregnation conditions. Impregnation of the monomeric furfuryl alcohol into the electrocatalyst layer may be controlled by varying the amount of furfuryl alcohol and/or the impregnation conditions, such as the impregnation temperature and time, to achieve the desired gradient through the thickness of the electrocatalyst layer.
Polymerization of the monomeric furfuryl alcohol may occur before and/or during bonding of the MEA. For example, the monomeric furfuryl alcohol may be polymerized during or after application to the sheet material, and before assembling the MEA. Alternatively, polymerization occurs simultaneously with bonding of the MEA components by assembling an MEA with an electrocatalyst layer containing monomeric (unpolymerized) furfuryl alcohol and then subjecting the MEA to bonding conditions that are similar to the required polymerization conditions. In yet another example, the monomeric furfuryl alcohol may be partially polymerized during or after application to the sheet material, and then further polymerized during MEA
bonding.
The polymerization conditions may include a polymerization temperature, for example, heating to a temperature of between about 80 C and about 140 C, and a polymerization time of about 5 seconds to about 15 minutes. The polymerization time will be dependent on the polymerization temperature and the amount of furfuryl alcohol. For instance, the polymerization time from about 5 to 10 minutes for a low polymerization temperature and a high amount of furfuryl alcohol, but may range from about 1 to 2 minutes for a high polymerization temperature and a low amount of furfuryl alcohol. In some instances, the furfuryl alcohol may be cross-linked by exposure to ultraviolet rays, for example, by exposure to a mercury lamp.
In some embodiments, the amount of furfuryl alcohol and/or degree of polymerization of the furfuryl alcohol in or on the electrocatalyst layer is non-uniform in the xy-direction to preferentially control the hydrophobic properties in different regions of the fuel cell. In one embodiment, a higher concentration of monomeric furfuryl alcohol and/or a greater degree of polymerization of the monomeric furfuryl alcohol may be employed in regions of the electrocatalyst layer that tends to be wetter during fuel cell operation (for example, the outlet region of the fuel cell in comparison to the inlet region) to improve water removal therefrom. Further, the loading of the electrocatalyst composition with monomeric furfuryl alcohol may be varied when it is applied to the sheet material. In another example, the loading of monomeric furfuryl alcohol may be varied when it is applied to the electrocatalyst layer. In yet another example, the polymerization conditions may be varied along the xy-direction of the electrocatalyst layer to vary the degree of polymerization.
In further embodiments, an ionomer layer may also be employed between the PEM and electrocatalyst layer and/or between the electrocatalyst layer and GDL. The ionomer layer may also contain monomeric furfuryl alcohol and then polymerized after application to a surface of the PEM and/or the electrocatalyst layer, for example, polymerizing immediately after application or polymerizing during MEA
bonding. Again, the ionomer layer may be applied by any method known in the art, such as those described above, and may be uniform or non-uniform with respect to the planar surface of the catalyst layer.
The following examples are provided for the purpose of illustration, not limitation.
Example 1 Polymerization of furfuryl alcohol to form an electrode An electrocatalyst composition is made by mixing 662 grams of 10% by weight Nafion solution with 132 grams of a platinum-containing catalyst powder, 2 grams of monomeric furfuryl alcohol, 6 grams of isopropanol, and 290 grams of de-ionized water. The mixture is then mixed using an ultrasonic mixer and then sprayed onto a fluid diffusion layer comprising a carbon fiber paper and a microporous carbonaceous layer. The resulting electrode is then subjected to a temperature of about 140 C for about 2 to 10 minutes to polymerize the monomeric furfuryl alcohol, thereby producing an electrode with PFA.
Example 2 Polymerization of furfuryl alcohol to form a catalyst-coated membrane A solution of monomeric furfuryl alcohol is prepared by mixing 6 grams of monomeric furfuryl alcohol with 12 grams of isopropanol and 6 grams of de-ionized water. The solution is then sprayed onto the cathode electrocatalyst layer of a CCM.
The monomeric furfuryl alcohol is allowed to penetrate into the cathode electrocatalyst layer for about 1 hour at 20 C. After penetration, the CCM is heated to about 140 C for about 2 to about 10 minutes to polymerize the monomeric furfuryl alcohol, thereby producing a CCM with PFA in the cathode electrocatalyst layer.
Example 3 Polymerization of furfuryl alcohol as a layer on a carbon/Nafiori subla yer A solution of monomeric furfuryl alcohol was prepared by mixing 6 grams of monomeric furfuryl alcohol (98% Lancaster) with 12 grams of isopropanol and 6 grams of de-ionized water. The solution was then sprayed at room temperature onto a GDL having a sublayer containing carbon black and Nafion on one surface of the substrate. The sprayed GDL was then placed onto a hot plate at 140 C for about 10 minutes to polymerize the furfuryl alcohol. The final loading of PFA was about 45wt%.
The polymerized GDL was then subjected to a mercury intrusion porosimetry test using the Autopore III supplied by Micromeritics Instrument Corporation, and a series of through-plane permeability tests using the 58-21 Roughness and Air Permeance Tester supplied by Testing Machines (TMI Inc.). (A through-hole was bored through the bottom jig of the tester and a rubber seal was placed around the test piece so that air was forced from the top jig to the bottom jig through the test piece.) Mercury intrusion porosimetry tests showed that the average pore diameter shifted from about 0.67 microns with no PFA to 1.11 microns with PFA, while through-plane permeability tests showed that the air permeability increase from an average of 129 mL/min with no PFA to an average of 183 mL/min with PFA. The furfuryl alcohol likely shrinks as it polymerizes, thus pulling the pores wider apart and increasing the size and through-plane permeability thereof. This increase in pore size and through-plane permeability may improve water removal and reactant accessibility when PFA is employed in the electrocatalyst layer, in addition to increasing the hydrophobicity of the electrocatalyst layer.
All of the above U.S. patents, U.S. patent application publications, U.S.
patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
While particular steps, elements, embodiments and applications of the present invention have been shown and described herein for purposes of illustration, it will be understood, of course, that the description is not limited thereto since modifications may be made by persons skilled in the art, particularly in light of the foregoing teachings, without deviating from the spirit and scope of the present disclosure. Accordingly, the invention is not limited except as by the appended claims.
Claims (20)
1. A membrane electrode assembly comprising:
an anode comprising an anode gas diffusion layer and an anode electrocatalyst layer;
a cathode comprising a cathode gas diffusion layer and a cathode electrocatalyst layer; and a proton exchange membrane disposed between the anode and the cathode;
wherein at least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises polyfurfuryl alcohol.
an anode comprising an anode gas diffusion layer and an anode electrocatalyst layer;
a cathode comprising a cathode gas diffusion layer and a cathode electrocatalyst layer; and a proton exchange membrane disposed between the anode and the cathode;
wherein at least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises polyfurfuryl alcohol.
2. The membrane electrode assembly of claim 1 wherein the cathode electrocatalyst layer comprises a platinum alloy catalyst.
3. The membrane electrode assembly of claim 2 wherein the platinum alloy catalyst is a platinum-cobalt alloy catalyst.
4. The membrane electrode assembly of claim 2 wherein the cathode electrocatalyst layer comprises an ionomer.
5. The membrane electrode assembly of claim 1 wherein a distribution of the polyfurfuryl alcohol is non-uniform in a z-direction of the at least one of the anode and cathode electrocatalyst layers.
6. The membrane electrode assembly of claim 1 wherein a distribution of the polyfurfuryl alcohol is non-uniform in a xy-direction of the at least one of the anode and cathode electrocatalyst layers.
7. A catalyst-coated membrane comprising an anode electrocatalyst layer, a cathode electrocatalyst layer, and a proton exchange membrane interposed therebetween; wherein at least one of the anode electrocatalyst layer and the cathode electrocatalyst layers comprises polyfurfuryl alcohol.
8. The catalyst-coated membrane of claim 7, wherein the cathode electrocatalyst layer comprises a platinum alloy catalyst.
9. The catalyst-coated membrane of claim 8 wherein the cathode electrocatalyst layer comprises a platinum alloy catalyst.
10. The catalyst-coated membrane of claim 7 wherein a distribution of the polyfurfuryl alcohol is non-uniform in a z-direction of the at least one of the anode and cathode electrocatalyst layers.
11. A method of making an electrode for an electrochemical fuel cell, the method comprising the steps of:
applying an electrocatalyst composition to a sheet material;
adding monomeric furfuryl alcohol to the electrocatalyst composition; and polymerizing the monomeric furfuryl alcohol after adding monomeric furfuryl alcohol and applying the catalyst composition.
applying an electrocatalyst composition to a sheet material;
adding monomeric furfuryl alcohol to the electrocatalyst composition; and polymerizing the monomeric furfuryl alcohol after adding monomeric furfuryl alcohol and applying the catalyst composition.
12. The method of claim 11 wherein the electrocatalyst composition further comprises at least one of an ionomer, a polar aprotic solvent, and a pore former.
13. The method of claim 11 wherein the electrocatalyst composition is applied to the sheet material subsequent to the step of adding monomeric furfuryl alcohol to the electrocatalyst composition.
14 14. The method of claim 11 wherein the electrocatalyst composition is applied to the sheet material prior to the step of adding monomeric furfuryl alcohol to the electrocatalyst composition.
15. The method of claim 14 further comprising the step of subjecting the monomeric furfuryl alcohol and electrocatalyst composition to an impregnation temperature and time prior to the step of polymerizing the monomeric furfuryl alcohol.
16. The method of claim 15 wherein the impregnation temperature is about 20°C to about 85°C.
17. The method of claim 11 wherein the sheet material is selected from the group consisting of a gas diffusion layer, a proton exchange membrane, and a transfer material.
18. The method of claim 11 wherein the step of polymerizing the monomeric furfuryl alcohol comprises subjecting the monomeric furfuryl alcohol to a temperature of about 120°C or greater.
19. The method of claim 11 wherein the step of polymerizing the monomeric furfuryl alcohol comprises subjecting the monomeric furfuryl alcohol to a temperature of about 140°C or less.
20. The method of claim 11 wherein the step of polymerizing the monomeric furfuryl alcohol comprises subjecting the monomeric furfuryl alcohol to an acidic environment.
Applications Claiming Priority (3)
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| US86487706P | 2006-11-08 | 2006-11-08 | |
| US60/864,877 | 2006-11-08 | ||
| PCT/US2007/083954 WO2008058199A1 (en) | 2006-11-08 | 2007-11-07 | Electrocatalyst layers for fuel cells and methods of making electrocatalyst layers for fuel cells |
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| CA2668895A1 true CA2668895A1 (en) | 2008-05-15 |
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| CA002668895A Abandoned CA2668895A1 (en) | 2006-11-08 | 2007-11-07 | Electrocatalyst layers for fuel cells and methods of making electrocatalyst layers for fuel cells |
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| Country | Link |
|---|---|
| KR (1) | KR20090082457A (en) |
| CN (1) | CN101558519A (en) |
| CA (1) | CA2668895A1 (en) |
| WO (1) | WO2008058199A1 (en) |
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| CN109585858B (en) * | 2018-10-08 | 2021-06-15 | 武汉船用电力推进装置研究所（中国船舶重工集团公司第七一二研究所） | Preparation method of fuel cell gas diffusion layer with hydrophobicity |
| CN111540882A (en) * | 2020-06-04 | 2020-08-14 | 湖北亿纬动力有限公司 | Negative pole piece, preparation method and application thereof |
| CN114566653B (en) * | 2021-09-08 | 2023-01-31 | 中自环保科技股份有限公司 | Non-uniform catalyst layer, membrane electrode and preparation method thereof |
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| JP3245929B2 (en) * | 1992-03-09 | 2002-01-15 | 株式会社日立製作所 | Fuel cell and its application device |
| US6054230A (en) * | 1994-12-07 | 2000-04-25 | Japan Gore-Tex, Inc. | Ion exchange and electrode assembly for an electrochemical cell |
| JPH09283153A (en) * | 1996-04-09 | 1997-10-31 | Ishikawajima Harima Heavy Ind Co Ltd | Solid high molecular electrolyte fuel cell |
| US6087032A (en) * | 1998-08-13 | 2000-07-11 | Asahi Glass Company Ltd. | Solid polymer electrolyte type fuel cell |
| US6300000B1 (en) * | 1999-06-18 | 2001-10-09 | Gore Enterprise Holdings | Fuel cell membrane electrode assemblies with improved power outputs and poison resistance |
| WO2001094668A1 (en) * | 2000-06-06 | 2001-12-13 | Toagosei Co., Ltd. | Gas diffusion electrode, method for manufacturing the same and fuel cell using it |
| CN100350659C (en) * | 2003-11-26 | 2007-11-21 | 日立麦克赛尔株式会社 | Power generating element for liquid fuel cell, method for producing the same, and liquid fuel cell using the same |
-
2007
- 2007-11-07 KR KR1020097011524A patent/KR20090082457A/en not_active Application Discontinuation
- 2007-11-07 CN CNA2007800458342A patent/CN101558519A/en active Pending
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