JP2009534796A - Method for configuring components for electrochemical cells - Google Patents

Abstract

The present invention relates to a method of configuring components of a membrane electrode assembly. The method includes transferring the catalyst layer to a polymer electrolyte membrane or gas diffusion layer. A method of constructing a membrane electrode assembly with these components is also disclosed. The method includes forming a first transfer assembly, the first transfer assembly comprising a first catalyst material and a hydrophobic binder on a surface of a first release sheet. Providing a catalyst layer, heating the first catalyst layer to a sintering temperature of at least 250 ° C. to form a sintered first catalyst layer, and the sintered first catalyst layer Transferring to the first surface of the polymer electrolyte membrane and removing the first release sheet from the sintered first catalyst layer after bonding.

Description

(Refer to related applications)
This application is filed under US Patent Law under US Provisional Patent Application No. 60 / _______ filed on April 21, 2006 (formerly US Application 11 / 480,787, dated April 16, 2007). The above provisional application is incorporated herein by reference in its entirety.

(Technical field)
The present invention relates to components for electrochemical cells, and in particular to a method for constructing catalyst coated membranes, gas diffusion electrodes, and membrane electrode assemblies.

(Description of related technology)
Electrochemical fuel cells convert fuel and oxidant to electricity. Solid polymer electrochemical fuel cells generally employ a membrane electrode assembly that includes a solid polymer electrolyte membrane disposed between two electrodes. The membrane electrode assembly is typically sandwiched between two conductive flow fields to form a fuel cell. These flow field plates act as current collectors, provide support for the electrodes, and provide passages for reactants and products. Such flow field plates typically include fluid flow paths to direct the flow of fuel and oxidant reactants to the anode and cathode of the membrane electrode assembly, respectively, to remove excess reactant fluid and reaction products. Remove. In operation, the electrodes are electrically coupled to conduct electrons between the electrodes through an external circuit. Typically, a number of fuel cells are electrically coupled in series to form a fuel cell stack having a desired output.

  The anode and cathode each contain a layer of anode catalyst and cathode catalyst, respectively. The catalyst may be a metal, an alloy, or a supported metal / alloy catalyst, such as platinum supported on carbon black. The catalyst layer typically contains an ion conductive material, such as Nafion®, and optionally a binder, such as polytetrafluoroethylene. Each electrode further contains a conductive porous substrate, such as carbon fiber paper or carbon cloth, for reactant distribution and / or mechanical support. The thickness of the porous substrate typically ranges from about 50 to about 250 microns. Optionally, the electrode may include a porous underlayer disposed between the catalyst layer and the substrate. The lower layer usually contains conductive particles, such as carbon particles, and optionally water repellent material for modifying its properties such as gas diffusion and water management.

  One method of constructing a membrane electrode assembly includes applying a layer of catalyst to a porous substrate in the form of an ink or slurry containing dissolved solids, typically mixed with particulates and a suitable liquid carrier. . The electrode is then formed by removing the liquid and leaving a layer of dispersed particulates. An ion exchange membrane such as a polymer electrolyte membrane is then assembled with an anode and a cathode in contact with the opposite surface of the membrane such that the electrode catalyst layer is sandwiched between the membrane and each substrate. The assembly is then bonded, typically under heat and pressure, to form a membrane electrode assembly. When a lower layer is employed, the lower layer may be applied to the porous substrate before applying the catalyst. The substrate is generally referred to as a gas diffusion layer, or if a lower layer is employed, the combination of the substrate and the lower layer may also be referred to as a gas diffusion layer.

  Conventional methods for applying a catalyst to a gas diffusion layer to form a gas diffusion electrode include screen printing and knife coating. However, when a gas diffusion electrode is formed by applying a low-load catalyst to a substrate, a smooth and continuous catalyst layer (that is, no discontinuity across the layer) having a uniform thickness is formed due to the surface roughness of the substrate. It is difficult to get. This can lead to a decrease in fuel cell performance and / or durability.

  Alternatively, a layer of catalyst can be applied to both sides of the polymer electrolyte membrane to form a catalyst coated membrane and then assembled with a porous substrate to form a membrane electrode assembly. For example, the catalyst slurry may be applied directly to the membrane by microgravure coating, knife coating, or spraying.

However, the use of a catalyst material and a catalyst containing a hydrophobic binder is desirable for fuel cell durability. As discussed in U.S. Patent No. 6,053,077, series fuel cells are potentially susceptible to voltage reversal, a situation where a cell must be reversed in polarity by another series cell. This can occur when a battery cannot generate current that is pushed through it by other batteries. Damage due to voltage reversal can be mitigated by increasing the amount of water available for electrolysis during reversal, thereby making the water more harmless than harmful oxidation of the anode component. In electrolysis, current that is pushed through the battery is used. By restricting this water passage through the anode structure into the fuel stream, more water remains near the catalyst. This can be achieved, for example, by causing the anode catalyst layer to block water flow (either water vapor or liquid phase). For example, the addition of hydrophobic materials such as PTFE and / or FEP to these layers prevents water flow through the anode by making them more hydrophobic. However, if these polymers are not sintered, they may be sufficiently hydrophobic and may be washed away from the catalyst layer over time. Using conventional methods of applying the catalyst layer directly to the membrane, the catalyst layer must be sintered with the membrane. However, the sintering temperature is usually higher than the thermal decomposition temperature of the ionomer. For example, Nafion® membranes typically begin to decompose at about 250 ° C. Thus, when the membrane is coated with a catalyst having a hydrophobic binder and then subjected to a temperature sufficient to sinter the hydrophobic binder (eg, 330 ° C. for PTFE), the ion conductivity of the ionomer and Water uptake characteristics may be reduced or destroyed.
US Pat. No. 6,517,962

  Thus, while progress has been made in the art, there remains a need for improved methods of constructing gas diffusion electrodes and catalyst coated membranes. The present invention addresses this problem and provides further related advantages.

  Briefly, the present invention relates to a method of configuring a component for an electrochemical fuel cell.

  In one embodiment, the method comprises a first transfer assembly comprising a first catalyst layer comprising a first catalyst material and a hydrophobic binder on a surface of a first release sheet. Forming a transfer assembly; heating the first catalyst layer to a sintering temperature of at least 250 ° C. to form a sintered first catalyst layer; and A step of transferring to the first surface of the electrolyte membrane; and a step of removing the first release sheet from the sintered first catalyst layer after bonding.

  In another embodiment, a method includes forming a diffusion lower layer on a surface of a release sheet, forming a catalyst layer comprising a first catalyst material on the diffusion lower layer, and applying the catalyst layer to the surface of an ion exchange membrane. And a step of removing the first release sheet from the diffusion lower layer. In some embodiments, the catalyst layer may comprise a hydrophobic binder or ionomer.

  In yet another embodiment, the method forms a first catalyst layer comprising a catalyst material on the surface of the release sheet and forms a first diffusion underlayer on the first surface of the first catalyst layer. A step of forming a second diffusion lower layer on the surface of the gas diffusion substrate, a step of transferring the first diffusion lower layer to the second diffusion lower layer, and a first so as to form a gas diffusion electrode. Removing the first release sheet from the catalyst layer.

  These and other aspects will become apparent upon reference to the attached drawings and the following detailed description.

  In the figures, identical reference numbers identify similar elements or actions. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of the various elements are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve the clarity of the figure. Furthermore, as depicted, the particular shape of the element is not intended to convey information about the actual shape of the particular element, but is only selected for ease of recognition in the figures.

  Throughout the following specification and claims, the word “comprising” and its variations, such as “comprising” and “comprising”, unless the context indicates otherwise. Is to be interpreted in an inclusive, non-limiting sense, ie, “including but not limited to”.

  As used herein and in the appended claims, “sintering” means the stabilization of a hydrophobic polymer, typically by heat treatment to a temperature above about 250 ° C. One skilled in the art will appreciate that the sintering conditions are different for different polymers. For example, suitable sintering conditions are about 330 ° C. to about 420 ° C. for polytetrafluoroethylene (“PTFE”) and about 250 ° C. to about 280 ° C. for fluorinated ethylene propylene (“FEP”). For perfluoroalkoxy ("PFA"), including sintering temperatures ranging from about 300 ° C to about 310 ° C.

  In this text, “load” refers to the amount of material that is formed or applied to a substrate and is usually expressed as the mass of material per unit area of the substrate.

  As used herein, “homogeneous” means that the constituents are substantially uniformly dispersed in the mixture.

  The present invention adheres a catalyst layer to a polymer electrolyte membrane to form a catalyst coated membrane (“CCM”), or adheres to a gas diffusion layer (“GDL”) to form a gas diffusion electrode (“GDE”). To a method of configuring components of a membrane electrode assembly.

  According to the first embodiment of the present invention, a method of configuring a CCM is shown in FIGS. 1A to 1D. The method includes the steps of forming the catalyst layer 2 on the release sheet 4 to form the transfer assembly 6 (FIG. 1A) and sintering the catalyst layer 2 above about 250 ° C. to yield a sintered catalyst layer 8. Heating to temperature (FIG. 1B), transferring the catalyst layer 8 sintered at the appropriate transfer temperature and / or pressure (“T / P”) to the membrane 10 (FIG. 1C), and removing the backing layer (FIG. 1D).

  Referring to FIG. 1A, catalyst layer 2 contains a catalyst material such as a noble metal or a compound thereof, a supported noble metal, a supported noble metal compound, or a combination thereof. The catalyst layer 2 also contains a hydrophobic binder such as PTFE, FEP, PFA, or combinations thereof, and preferably does not contain an ionomer material. The constituents of the catalyst layer may be first dispersed in a suitable liquid carrier such as alcohol, water, or a combination thereof, mixed homogeneously to form a dispersion, and later applied to the release sheet. In some embodiments, the dispersion may further include a dispersion stabilizing material, eg, a surfactant such as Triton®-X or Tergitol, and / or a pore-forming material such as methylcellulose. Any method known in the art for applying dispersion may be used, including but not limited to knife coating, screen printing, slot die coating, microgravure coating, transfer, and jetting. In some embodiments, the liquid carrier may be removed or partially removed prior to sintering, for example, by evaporation. Alternatively, the liquid carrier may be removed during sintering.

  A suitable release sheet material should be inert, non-tacky and heat resistant to the maximum temperature it will undergo so that the release sheet will not deform and can be reused. In one example, the release sheet is a metal sheet, such as a 2SB finish, a K05 metal coating, or a stainless steel plate with a ceramic coating, an aluminum sheet, or a heat resistant polymer film, for example, a polyimide film such as Kapton®. If desired, the release sheet may be pretreated with a release agent prior to forming a layer thereon to facilitate removal of the release sheet from the transferred catalyst layer or diffusion bottom layer. The release agent may be an alcohol such as polyvinyl alcohol.

  As shown in FIG. 1C, the sintered catalyst layer 8 is transferred to the membrane 10 after being sintered by applying heat and / or pressure (T / P). For most solid polymer electrolyte membranes, a suitable transfer temperature may range from about 90 ° C. to about 200 ° C., and a suitable transfer pressure may range from about 5 to about 40 bar. Preferably, the opposite surface of the membrane 10 is supported by the support material 12 during transport. The support material 12 should be the same material as the release sheet 4 because it is inert, non-tacky and should be heat resistant to the highest temperature it undergoes and the transfer temperature is typically lower than the sintering temperature. There is no. For example, the support material 12 may be a PTFE, polyethylene, polypropylene, or polyester film, such as Mylar®. As shown in FIG. 1D, the release sheet 4 and the support material 12 are removed from the sintered catalyst layer after being transferred so as to form a catalyst-coated film 16.

  2A and 2B show that the diffusion lower layer 14 is formed on the release sheet 4 (FIG. 2A) and then the catalyst layer 2 is formed on the diffusion lower layer 14 (FIG. 2B) before sintering and transfer. FIG. 6 is an illustration of a further embodiment. The diffusion lower layer 14 contains a conductive material that may be fibrous or particulate. For example, the conductive material is carbon black, graphitized carbon black, flake graphite, spherical graphite, short carbon fiber, pulverized carbon fiber, carbon whisker, carbon nanotube, short graphite fiber, pulverized graphite fiber, graphite whisker, and graphite nanotube, Or, a combination thereof or the like, but not limited thereto, is carbon or graphite. In some embodiments, it may be desirable to incorporate a hydrophobic binder into the diffusion underlayer to change its water transport properties and / or improve adhesion between layers. The diffusion lower layer 14 may be formed on the release sheet 4 by dispersing constituents in a suitable liquid carrier and then applied thereon by the method described above.

It is anticipated that the diffusion underlayer may serve to transfer the catalyst layer to the membrane. We use a prior art method of transferring the catalyst layer to the membrane, especially when the thickness of the catalyst layer is low, eg, about 5 microns or less, and typically the catalyst load is low. For example, it has been found that incomplete transfer occurs (that is, a part of the catalyst layer may remain on the release sheet after transfer) when it is about 0.15 mg Pt / cm ² or less, for example. . Incomplete transfer of the catalyst layer is undesirable because it results in fuel cell performance loss, durability, and cost issues. However, as shown in FIGS. 2A and 2B, it is possible to completely transfer the catalyst layer to the membrane by employing a diffusion lower layer between the release sheet and the catalyst layer.

  In other embodiments, the second catalyst layer 18 may be formed on the opposite surface of the membrane 10 to form the CCM 20, as shown in FIG. 3A. The catalyst layer 18 may contain the same material composition as the catalyst layer 2 in the same or different amounts, or may contain a different material composition, for example a catalyst with ionomer. A catalyst layer with fluorinated and / or hydrocarbon-based ionomers may be beneficial for use where an increase in ionic conductivity in the catalyst layer is desired. Those skilled in the art will readily select a suitable catalyst for a given application.

  In some embodiments, the catalyst layer 18 is formed at a later time (FIG. 3B) or simultaneously (FIG. 3C) in a manner similar to that previously described (ie, forming the catalyst layer 18 on the release sheet 22). ) May be transferred to the membrane 10. Optionally, a diffusion underlayer such as that represented in FIGS. 2A and 2B may also be transferred with the catalyst layer 18 (not shown). Note that if the catalyst layer 18 contains an ionomer, the diffusion underlayer should be sintered before forming the catalyst layer 16 thereon. In other embodiments, the catalyst layer 18 can be applied directly to the membrane by any method known in the art before or after transfer (not shown).

  In further embodiments, the CCM of the foregoing embodiments may be assembled with GDL and / or GDE to form a membrane electrode assembly (“MEA”). For example, referring to FIG. 1D, the GDL may be disposed adjacent to the catalyst layer 8 while the GDE may be disposed adjacent to the second surface on the opposite side of the membrane 10. Alternatively, referring to FIG. 3A, the GDL may be disposed adjacent to the sintered catalyst layer 8, while another GDL may be disposed adjacent to the catalyst layer 16. In any case, the assembled MEA may substantially bond each of the components together under the bonding temperature and / or pressure. One skilled in the art can readily determine the appropriate bonding temperature, pressure, and duration.

  According to another embodiment of the invention, a method for configuring a GDE is disclosed. The method comprises the steps of forming a catalyst layer 2 on the support material 12 (FIG. 4A), forming a diffusion underlayer 14a on the catalyst layer 2 to form a transfer assembly 24 (FIG. 4B), partial GDL 28 Forming additional diffusion lower layer 14b on diffusion substrate 26 to form (FIG. 4C), transferring diffusion lower layer 14a to diffusion lower layer 14b (FIG. 4D), and sintering to form GDE 30 (FIG. 4E). The support material 12 may be removed before or after sintering (not shown).

  The catalyst layer 2 preferably contains a hydrophobic binder such as those mentioned above and a catalyst material. Still further, the diffusion lower layers 14a, 14b may contain the same constituents as described in the previous embodiment. In this embodiment, the diffusion lower layers 14a, 14b may have the same or different composition and may have the same or different loads. Further, the liquid carrier of the catalyst layer 2 may be removed or partially removed before the first diffusion lower layer 14a is formed thereon.

  Any suitable diffusion substrate material may be used as long as it is conductive and porous. Exemplary diffusion substrate materials are TGP-H-090 (Toray Industries Inc., Tokyo, Japan), AvCarb® P50 and EP-40 (Ballard Material Products Inc., Lowell, MA, Lowell, MA, Lowell, MA). Including non-woven mats of carbonized or graphitized carbon fibers such as, but not limited to, 25 series materials (SGL Carbon Corp., Charlotte, NC). The selection of the porous substrate is not essential to the present invention and those skilled in the art will be able to select an appropriate porous substrate for a given application. In some embodiments, the porous substrate may be hydrophobized, such as by impregnating the substrate in a solution containing a hydrophobic binder, which is dried and applied prior to application of the diffusion underlayer 14b. And / or sintered or simultaneously with the diffusion lower layers 14a, 14b and the catalyst layer 2 after transfer.

  The transfer conditions may be the same as those described in the previous embodiment. Still further, in some embodiments, the liquid carrier of the first and / or second lower layer 14a, 14b is removed during transfer.

  Referring to FIG. 4E, catalyst layer 2 and diffusion lower layers 14a and 14b are sintered after the transfer of diffusion lower layers 14a and 14b. Alternatively, the catalyst layer 2 and the diffusion lower layers 14a and 14b may be sintered separately before transfer, or may be simultaneously sintered during transfer (not shown). Again, the support material 12 can be any of the materials described above as long as it is heat resistant to the maximum temperature it undergoes (eg, transfer or sintering temperature depending on when the support material 12 is removed). Good.

  The inventors have discovered that when transferring a catalyst layer containing a hydrophobic binder to the GDL, incomplete transfer of the catalyst typically occurs, especially when transferring a thin catalyst layer. . However, by directly applying the first diffusion lower layer 14a on the catalyst layer 2, the transport of the catalyst layer 2 is improved. Still further, the second diffusion lower layer 14b is applied on the diffusion substrate 26, and the liquid carrier in the first and / or second diffusion lower layers 14a, 14b is removed during the transfer, so that the space between the diffusion lower layers 14a, 14b is reduced. The adhesion is also strengthened. As a result, the catalyst layer 2 can be completely transferred, and the adhesion between each of the layers can be improved compared to conventional methods.

  In further embodiments, GDE 30 may be assembled with a membrane and another GDE, or may be assembled with CCM and GDL to form an MEA. For example, the GDE 30 may be assembled with the membrane 10 (not shown) such that the catalyst layer 8 contacts the membrane 10. Another GDE is then assembled adjacent to the opposite surface of the membrane 10 to form the MEA. Alternatively, GDE 30 may be assembled with a CCM such as that shown in FIG. 1D and a GDL adjacent to catalyst layer 8 to form an MEA (not shown). Again, the assembled MEA may be bonded as described above.

  In any of the above embodiments, an adhesive layer, such as that described in US Patent Application No. 2004/0258979, may be employed between any of the layers prior to transfer. . The adhesive layer includes ionomers, and optionally carbon and / or graphite particles. It is anticipated that the adhesive layer may improve adhesion and may enhance proton conductivity through the catalyst layer.

  All of the above U.S. patents, U.S. patent publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications referenced herein and / or listed in the application data sheet are: In its entirety, incorporated herein by reference.

  While particular elements, embodiments and applications of the present invention have been illustrated and described, modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure, particularly in light of the preceding teachings. It will be appreciated that the invention is not so limited.

1A-1D show cross-sectional views representing a series of steps for forming a catalyst-coated membrane according to a first embodiment of the present invention. 1A-1D show cross-sectional views representing a series of steps for forming a catalyst-coated membrane according to a first embodiment of the present invention. 1A-1D show cross-sectional views representing a series of steps for forming a catalyst-coated membrane according to a first embodiment of the present invention. 1A-1D show cross-sectional views representing a series of steps for forming a catalyst-coated membrane according to a first embodiment of the present invention. FIG. 2A shows a cross-sectional view depicting steps for forming a catalyst coated membrane according to a further embodiment of the present invention. FIG. 2B shows a cross-sectional view depicting steps for forming a catalyst coated membrane according to a further embodiment of the present invention. 3A-3C show cross-sectional views depicting steps for forming a catalyst-coated membrane according to a still further embodiment of the present invention. 3A-3C show cross-sectional views depicting steps for forming a catalyst-coated membrane according to a still further embodiment of the present invention. 3A-3C show cross-sectional views depicting steps for forming a catalyst-coated membrane according to a still further embodiment of the present invention. 4A-4E are cross-sectional views illustrating a series of steps for forming a gas diffusion electrode according to another embodiment of the present invention. 4A-4E are cross-sectional views illustrating a series of steps for forming a gas diffusion electrode according to another embodiment of the present invention. 4A-4E are cross-sectional views illustrating a series of steps for forming a gas diffusion electrode according to another embodiment of the present invention. 4A-4E are cross-sectional views illustrating a series of steps for forming a gas diffusion electrode according to another embodiment of the present invention. 4A-4E are cross-sectional views illustrating a series of steps for forming a gas diffusion electrode according to another embodiment of the present invention.

Claims (24)

Forming a first transfer assembly, the first transfer assembly comprising a first catalyst layer comprising a first catalyst material and a hydrophobic binder on a surface of the first release sheet; , That,
Heating the first catalyst layer to a sintering temperature of at least 250 ° C. to form a sintered first catalyst layer;
Transferring the sintered first catalyst layer to a first surface of a polymer electrolyte membrane;
Removing the first release sheet from the sintered first catalyst layer after bonding. A method of constructing a component for an electrochemical fuel cell.   The method of claim 1, wherein the first catalyst material comprises a noble metal or an alloy thereof.   The method of claim 1, wherein the hydrophobic binder is polytetrafluoroethylene, fluorinated ethylene propylene, or a combination thereof.   The method of claim 1, wherein the first catalyst layer consists essentially of the first catalyst material and the hydrophobic binder.   The method of claim 1, wherein the sintering temperature is at least 330 ° C.   The method of claim 1, wherein the first release sheet is a polymer thin film.   The method of claim 1, wherein transferring comprises subjecting the first sintered catalyst layer and the polymer electrolyte membrane to at least one of a transfer temperature and a transfer pressure.   The method of claim 1, further comprising forming an ionomer layer on at least one of the first surface of the sintered first catalyst layer and the first surface of the membrane prior to transfer. the method of.   The method of claim 1, further comprising forming a second catalyst layer comprising a second catalyst material on a second surface opposite the polymer electrolyte membrane. Forming the second catalyst layer comprises:
Forming a second transfer assembly, the second transfer assembly comprising the second catalyst layer on a surface of a second release sheet;
Transferring the second catalyst layer to a second surface opposite the polymer electrolyte membrane;
The method according to claim 9, further comprising removing the release sheet from the second catalyst layer.   The method of claim 10, wherein the sintered first catalyst layer and the second catalyst layer are simultaneously transferred to the first and second surfaces of the polymer electrolyte membrane, respectively. Coupling a first gas diffusion layer to the first catalyst layer;
Coupling a gas diffusion electrode to the opposite surface of the polymer electrolyte membrane, the gas diffusion electrode comprising a second gas diffusion layer and a second catalyst layer, so that the opposite side The method of claim 1, further comprising: contacting the surface to form a membrane electrode assembly. Forming a diffusion lower layer on the surface of the release sheet;
Forming a catalyst layer comprising a first catalyst material on the diffusion underlayer;
Transferring the catalyst layer to the surface of the polymer electrolyte membrane;
Removing the first release sheet from the diffusion underlayer. A method of constructing a component for an electrochemical fuel cell.   The method of claim 13, wherein the diffusion underlayer comprises a carbon material, a graphite material, or a combination thereof.   The method of claim 13, wherein transferring comprises subjecting the catalyst layer and the polymer electrolyte membrane to at least one of heat and pressure.   The method of claim 13, wherein the catalyst layer further comprises an ionomer. Coupling a first gas diffusion substrate to the diffusion underlayer;
Coupling a gas diffusion electrode to the opposite surface of the polymer electrolyte membrane, the gas diffusion electrode comprising: a second gas diffusion substrate, a second catalyst layer, a second gas diffusion substrate, and a second gas diffusion substrate; Further comprising a second diffusion lower layer inserted between the two catalyst layers, such that the second catalyst layer contacts the opposite surface to form a membrane electrode assembly. The method according to claim 13. Forming a first catalyst layer comprising a catalyst material on the surface of the release sheet;
Forming a first diffusion underlayer on a first surface of the first catalyst layer;
Forming a second diffusion underlayer on the surface of the gas diffusion substrate;
Transferring the first diffusion lower layer to the second diffusion lower layer;
Removing the first release sheet from the first catalyst layer to form a gas diffusion electrode. A method of configuring components for an electrochemical fuel cell.   The first catalyst layer and the first diffusion layer further comprise a hydrophobic binder, the method comprising heating the first diffusion lower layer and the catalyst layer to a sintering temperature of at least 250 ° C. The method of claim 18 further comprising:   The method of claim 18, wherein the second diffusion underlayer comprises a hydrophobic binder and the method further comprises heating the second diffusion underlayer to a sintering temperature of at least 250 ° C.   The method of claim 18, wherein the first and second diffusion underlayers comprise a carbon material, a graphite material, or a combination thereof.   The method of claim 18, wherein the first and second diffusion underlayers are the same.   19. The method of claim 18, further comprising removing a liquid carrier in at least one of the first and second lower layers during transfer. Bringing the gas diffusion electrode into contact with the first surface of the polymer electrolyte membrane so that the first catalyst layer faces the first surface;
Bringing the second gas diffusion electrode into contact with the second surface opposite to the polymer electrolyte membrane so that the second catalyst layer faces the second surface;
The method of claim 18, further comprising: bonding the gas diffusion electrode to the polymer electrolyte membrane.

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