WO2015095021A1

WO2015095021A1 - Membrane electrode assembly and methods of making the same

Info

Publication number: WO2015095021A1
Application number: PCT/US2014/070293
Authority: WO
Inventors: Joseph W. Frisk; Eric J. Hanson; Daniel M. Pierpont
Original assignee: 3M Innovative Properties Company
Priority date: 2013-12-17
Filing date: 2014-12-15
Publication date: 2015-06-25

Abstract

Membrane electrode assemblies (9) comprising a first gas diffusion layer (12,19) having a first microporous layer (101) on a major surface thereof (99), wherein the first microporous layer (101) has a major surface (110), and wherein the major surface (110) of the first microporous layer (101) has discontinuous areas (103) therein substantially free of material, and wherein at least a portion of at least one discontinuous area (103) is in an active area of the first gas diffusion layer (12,19); and methods of making the same. The membrane electrode assemblies are useful, for example, in fuel cells.

Description

MEMBRANE ELECTRODE ASSEMBLY

AND METHODS OF MAKING THE SAME

Cross Reference To Related Application

This application claims the benefit of U.S. Provisional Patent Application Number 61/917143, filed December 17, 2013, the disclosure of which is incorporated by reference herein in its entirety.

Background

[0001 ] It can be advantageous in fuel cell applications to have a gas diffusion layer with specialized water management properties in order to control flow of product water. Controlling the product water may be even more beneficial to relatively ultra thin (i.e., than about 2 micrometers thick) electrode layers that can easily accumulate too much water during operation and suffer a loss of performance due to limitations in mass transport.

Summary

[0002] In one aspect, the present disclosure describes a membrane electrode assembly comprising a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface, and wherein the major surface of the first microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area is at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 mm, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, 1mm to 3 mm, or even 1 mm to 2 mm) wide and at least in an active area of the first gas diffusion layer. "Active area" as used herein refers to an area in the gas diffusion layer where a major surface of the gas diffusion layer surface is adjacent to the catalyst surface available for electrochemical fuel cell reactions to take place. "Substantially free of material" as used herein refers to at least a portion of a discontinuous area that does not have material (e.g., microporous material) on the applicable major surface of the gas diffusion layer.

[0003] In another aspect, the present disclosure describes a first method of making a membrane electrode assembly, the method comprising:

providing a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface area; removing a portion of the first microporous layer from the first gas diffusion layer to provide at least a first area on the major surface of the first gas diffusion layer substantially free of first microporous material;

providing a catalyst coated membrane having first and second generally opposed major surfaces, wherein the first major surface comprises a anode catalyst, and wherein the second major surface comprises a cathode catalyst;

securing the first gas diffusion layer to at least one of the anode or cathode catalyst of the catalyst coated membrane; and

securing the remaining the anode or cathode catalyst of the catalyst coated membrane and a second gas diffusion layer

to provide the membrane electrode assembly.

[0004] In another aspect, the present disclosure describes a second method of making a membrane electrode assembly, the method comprising:

coating a microporous layer onto a first gas diffusion layer on a major surface thereof using at least one mask to provide a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface, and wherein the major surface of the first microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area is in an active area of the first gas diffusion layer;

to provide the membrane electrode assembly.

[0005] Membrane electrode assemblies described herein are useful, for example, in fuel cells.

Advantages of embodiments of membrane electrode assemblies described herein include water management properties as the channels can help facilitate removal of excess water that may flood or otherwise cover a catalyst and block or impede reactant flow.

Brief Description of the Drawings

[0006] FIG. 1 is an illustration of an exemplary fuel cell including an article described herein;

[0007] FIG. 2 is an exploded view of an exemplary membrane electrode assembly described herein included the fuel cell shown in FIG.1 ; and [0008] FIG. 2A is an expanded view of a gas diffusion layer having discontinuous areas.

Detailed Description

[0009] Referring to FIG. 1 , fuel cell 10 includes an exemplary membrane electrode assembly described herein 9. Membrane electrode assembly 9 first gas diffusion layer (GDL) 12 adjacent anode 14.

Adjacent the anode 14 includes electrolyte membrane 16. Cathode 18 is adjacent electrolyte membrane 16, and second gas diffusion layer 19 is adjacent the cathode 18. GDLs 12 and 19 can be referred to as diffuse current collectors (DCCs) or fluid transport layers (FTLs). In operation, hydrogen fuel is introduced into the anode portion of fuel cell 10, passing through first gas diffusion layer 12 and over anode 14. At anode 14, the hydrogen fuel is separated into hydrogen ions (H⁺) and electrons (e^~).

[0010] Electrolyte membrane 16 permits only the hydrogen ions or protons to pass through electrolyte membrane 16 to the cathode portion of fuel cell 10. The electrons cannot pass through electrolyte membrane 16 and, instead, flow through an external electrical circuit in the form of electric current. This current can power, for example, electric load 17, such as an electric motor, or be directed to an energy storage device, such as a rechargeable battery.

[001 1] Oxygen flows into the cathode side of fuel cell 10 via second gas diffusion layer 19. As the oxygen passes over cathode 18, oxygen, protons, and electrons combine to produce water and heat.

[0012] FIGS. 2and 2A provide some further details of exemplary membrane electrode assembly described herein 9. Membrane electrode assembly described herein 9 comprises first gas diffusion layer 12 having first microporous layer 101 on major surface thereof 99, wherein first microporous layer 101 has major surface 1 10. Major surface 99 of first microporous layer 101 has discontinuous areas therein 103 substantially free of material. At least a portion of at least one discontinuous area 103 is in an active area of first gas diffusion layer 12. Optionally, second gas diffusion layer 19 having second microporous layer (not shown) has discontinuous areas therein (not shown) substantially free of material. In some embodiments, for example, as illustrated here, at least a portion of at least one discontinuous area is in an active area of second gas diffusion layer 19.

[0013] Although FIGS. 2 and 2A show an exemplary diffusion layer having the discontinuous areas therein secured to the anode catalyst of the catalyst coated membrane, and a gas diffusion layer which may or may not have the discontinuous areas therein secured to the cathode catalyst of the catalyst coated membrane, other exemplary embodiments of membrane electrode assembly described herein have a diffusion layer having the discontinuous areas therein secured to the cathode catalyst of the catalyst coated membrane, and a gas diffusion layer which may or may not have the discontinuous areas therein secured to the anode catalyst of the catalyst coated membrane. [0014] In some embodiments, the discontinuous areas of a gas diffusion layer are a plurality of channels. In some embodiments, at least a portion of the discontinuous areas substantially free of material are a plurality of unconnected channels. In some embodiments, at least a portion of the discontinuous areas substantially free of material are a plurality of connected channels.

[0015] In some embodiments, the first discontinuous areas substantially free of material associated with a microporous layer are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

[0016] Suitable gas diffusion layers and or methods of making the layers are known in the art, or can be modified as described herein, to make membrane electrode assemblies described herein. Typically the gas diffusion layer comprises sheet material comprises carbon fibers. Typically the gas diffusion layer is a carbon fiber in the form of woven or non-woven carbon fibers. Exemplary carbon fibers are commercially available, for example, under the trade designations "TORAY CARBON PAPER" from Toray Industries from Chuo-ku, Japan; "ZOLTE CARBON CLOTH PANEX 30" from Zoltek

Corporation, St. Louis, MO; and "FREUDENBERG GAS DIFFUSION LAYERS" from Freudenberg FCCT Se & Co. Kg. Weinheim, Germany. Optionally the gas diffusion layer may be coated or impregnated with various materials, including carbon particle coatings, hydrophilizing treatments, and hydrophobizing treatments (e.g., coating with polytetrafluoroethylene (PTFE)).

[0017] The porous microlayers typically comprise carbon particles and a polymeric composition.

Suitable carbon particles are known in the art. Exemplary carbon particles include primary particles (average sizes ranging from about 1 nanometer (nm) to about 100 nm), primary aggregates of primary particles (average sizes ranging from about 0.01 micrometer to about 1 micrometer), secondary aggregates of primary aggregates (average sizes ranging from 0.1 micrometer to about 10 micrometers), agglomerates of aggregates (average sizes greater than about 10 micrometers), and combinations thereof. In some embodiments, the carbon particles include primary particles, primary aggregates, and combinations thereof.

[0018] Suitable carbon particles are known in the art and include carbon black (e.g., oil-furned carbon black (commercially available, for example, under the trade designation "VULCAN XC-72 CARBON BLACK" from Cabot Corporation, Billerica, MA)). Graphitized carbon particles are also desirable, as they generally exhibit good stability versus oxidation.

[0019] Exemplary polymeric compositions for the porous microlayers are known in the art and include combinations of highly- fluorinated polymers that are non-melt processable and highly- fluorinated polymers that are melt processable. In some embodiments, the non-melt processable polymers and the melt processable polymers are each perfluoropolymers.

[0020] Exemplary non-melt processable polymers include highly-fluorinated polymers that exhibit melt flow indices of less than about 0.5 gram/10 minutes (e.g., homopolymers of tetrafluoroethylene (TFE) copolymers of TFE and other monomers, and combinations thereof). Copolymers of TFE and perluoroalkylvinylethers are typically referred to as "modified PTFE" or "TFM" (commercially available, for example, under the trade designation "DYNEON TFM" from Dyneon, LLC, Oakdale, MN). An example of a suitable monomer for use with TFE in the copolymer includes

perfluoropropylvinylether.

[0021 ] Exemplary melt processable polymers include highly- fluorinated polymers that exhibit melt flow indices of at least about one gram/10 minutes (e.g., highly- fluorinated polymers include perfluoroalkoxyalkanes (PFA) (e.g., copolymers of TFE and perfluoroalkoxyvinylethers), fluorinated ethylene propylene (FEP), perfluoroalkyl acrylates, hexafluoropropylene copolymers, terpolymers of tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride (THV), copolymers of TFE and ethylene (ETFE), perfluoropolymers thereof, and combinations thereof).

[0022] A porous microlayer may be applied to the gas diffusion layer using techniques known in the art, including coating an aqueous suspension to a major the surface of the gas diffusion layer. Suitable aqueous suspensions are known in the art and typically comprise a carrier, a surfactant, the carbon particles, and the polymeric composition. Exemplary carriers include water, alcohols, and combinations thereof. Exemplary surfactants include surfactants capable of substantially dispersing or suspending the carbon particles and the polymeric composition in the carrier. In some embodiments, the aqueous suspension may also include other materials, such as thickening agents, defoaming agents, emulsifiers, and stabilizers.

[0023] The concentrations of the carrier, the surfactant, the carbon particles, and the polymeric composition may vary depending on the components selected. Examples of suitable compositional concentrations of the aqueous suspension include in a range from about 0.1% to about 15% surfactant, about 1% to about 50% carbon particles, and about 0.1% to about 15% polymeric composition, by weight, based on the total weight of the aqueous suspension. Suitable concentrations of the carrier are correspondingly the concentration differences between the aqueous suspension and the sum of the above-listed components.

[0024] The aqueous suspension may be coated using a variety of methods known in the art, including hand methods, machine methods, hand brushing, notch bar coating, wire-wound rod coating, fluid bearing coating, slot-fed knife coating, and three-roll coating. The coating may be achieved in one pass or in multiple passes.

[0025] After the aqueous suspension is coated on gas diffusion layer may initially be heated to sufficient temperatures and durations to substantially remove the carrier, the surfactant, and

decomposition products of the surfactant. After the initial heating, the microlayer substantially retains the relative concentrations of the carbon particles and the polymeric composition as provided in the aqueous suspension. Exemplary compositional concentrations in a microlayer (following the initial heating) include in a range from about 50% to about 90% (in some embodiments, about 75% to about 85%) carbon particles, and from about 10% to about 50% (in some embodiments, about 15% to about 25%) polymeric composition, by weight, based on the total weight of the given microlayer.

[0026] After the initial heating, a second heating step may then be used to sinter the polymeric composition. Examples of suitable sintering temperatures and durations include temperatures and durations capable of sintering the non-melt processable polymers and the melt processable polymers (e.g., about 330°C for PTFE).

[0027] For the second method described herein gas diffusion layers having the discontinuous areas (including more than one discontinuous area (e.g., a second area; a second area and a third area; a second area, third area, and a fourth area, etc.)) on a gas diffusion layer can be made using masks when coating (including casting) the microporous layer. The mask can be used to prevent the desired portion(s) of the gas diffusion layer (e.g., the outer peripheral edge of the gas diffusion layer) from being coated with the microporous layer material. Typically the mask covers in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

[0028] For the first method described herein a portion(s) of a microporous layer on a gas diffusion layer can be removed, for example, via at least one of mechanical removal (e.g., machining and adhesive removal) or laser ablation. Laser ablation can be completed by concentrating energy with enough strength to remove microporus layer down to the gas diffusion layer fibers. Typically the ablation may remove microporous layer down to the fibers making channels or lines in the microporous layer reducing the area covered by the microporous layer byl% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

[0029] Removal of a portion of the microporous layer by adhesive can also be performed. For example, using a pressure sensitive adhesive such as that available under the trade designation "SCOTCH ATG ADHESIVE TRANSFER TAPE #924" from 3M Company, St. Paul , MN, a patterned adhesive, or adhesive tape such as that available under the trade designation "3M MICROCOMPLY ADHESIVE" from 3M Company in the active area and then pulling the adhesive off to remove microporous layer material and create channels in the microporous layer in the range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

[0030] In some embodiments, microporous layer material is removed from at least one additional area (e.g., a second area; a second area and a third area; a second area, third area, and a fourth area, etc.) on the major surface of the gas diffusion layer.

[0031 ] Suitable catalyst coated membranes (CCMs) comprising anode and cathode catalyst layers and a polymer electrolyte membrane (PEM) are known in the art and can be made using techniques known in the art, including laminating, roll bonding, screen printing, pressing, of catalyst onto the polymer electrolyte membrane. [0032] Suitable polymer electrolyte membranes are known in the art, and typically comprise polymer electrolytes bearing anionic functional groups bound to a common backbone, which are typically sulfonic acid groups but may also include carboxylic acid groups, imide groups, amide groups, or other acidic functional groups. In some embodiments, the polymer electrolytes are highly fluorinated (e.g., perfluorinated). In some embodiments, the polymer electrolytes are copolymers of tetrafluoroethylene and at lest one fluorinated, acid-functional comonomers. Polymer electrolytes are commercially available, for example, under the trade designations "NAFION" from DuPont Chemicals, Wilmington DE) and "FLEMION" from Asahi Glass Co. Ltd., Tokyo, Japan. In some embodiments, the polymer electrolyte is be a copolymer of tetrafluoroethylene (TFE) and FS02-CF2CF2CF2CF2-0-CF=CF2as described, for example, in U.S. Pat. No. 6,624,328 (Guerra) and 7,348,088 (Hamrock et al.) and U.S. Pat. Pub. Nos. US 2004-01 16742 Al, published December 17, 2004, the disclosures of which are incorporated herein by reference. Typically, the polymer has an equivalent weight (EW) of no greater thanl200 (in some embodiments, no greater than 1 100, 1000, 900, or even no greater than 800).

[0033] The polymer can be formed into a membrane by techniques known in the art, including casting from a suspension (e.g., bar coating, spray coating, slit coating, and brush coating). Other techniques for forming the polymer into the membrane include melt process (e.g., via extrusion) a neat polymer. After forming, the membrane may be annealed, typically at a temperature of at least 120°C (in some embodiments, at least 130°C, or even at least 150°C). Typically, the polymer electrolyte membrane has a thickness not greater than 50 micrometers (in some embodiments, not greater than 40 micrometers, not greater than 30 micrometers, or even not greater than 15 micrometers).

[0034] In some embodiments, the polymer electrolyte membrane further comprises a porous support, such as a layer of expanded PTFE, where the pores of the porous support contain the polymer electrolyte. In some embodiments, the polymer electrolyte membrane has no porous support. In some embodiments, the polymer electrolyte membrane further comprises a crosslinked polymer.

[0035] Suitable catalyst coated membranes are known in the art. In some embodiments, carbon- supported catalyst particles are used. Typical carbon-supported catalyst particles are 50-90% carbon and 10-50% catalyst metal by weight, wherein the catalyst metal typically comprises Pt for the cathode and Pt and Ru in a weight ratio of 2: 1 for the anode. Typically, the catalyst is applied to the polymer electrolyte membrane or to the gas diffusion layer in the form of a catalyst ink. Alternately, for example, the catalyst ink may be applied to a transfer substrate, dried, and thereafter applied to the polymer electrolyte membrane or to the gas diffusion layer as a decal. The catalyst ink typically comprises polymer electrolyte material, which may or may not be the same polymer electrolyte material which comprises the polymer electrolyte membrane. The catalyst ink typically comprises a dispersion of catalyst particles in a dispersion of the polymer electrolyte. The ink typically contains 5-30% solids (i.e., polymer and catalyst) and more typically 10-20% solids. The electrolyte dispersion is typically an aqueous dispersion, which may additionally contain alcohols and polyalcohols (e.g., glycerin and ethylene glycol). The water, alcohol, and polyalcohol content may be adjusted to alter rheological properties of the ink. In some embodiments, the ink typically contains 0-50% alcohol and 0-20% polyalcohol. In some embodiments, the ink may contain 0-2% of a suitable dispersant. The ink can be made, for example, by stirring with heat followed by dilution to a coatable consistency. Ink can be coated, for example, onto a liner or the membrane itself by both hand and machine methods, including hand brushing, notch bar coating, fluid bearing die coating, wire-wound rod coating, fluid bearing coating, slot-fed knife coating, three-roll coating, or decal transfer. Coating may be achieved in one application or in multiple applications.

[0036] Membrane electrode assemblies can be assembled using techniques known in the art, including attaching the gas diffusion layers to either side of a catalyst coated membrane by adhering them using an adhesive. Exemplary adhesives include ones that will not contaminate the fuel cell (e.g., acrylates or thermal adhesives (e.g., ethylene vinyl acetate or ethylene ethyl acrylate)).

[0037] The gas diffusion layer can be attached, for example, by pressure or a combination of pressure and temperature in a press or nip for roll attachment. In some embodiments, the second gas diffusion layer is secured to the catalyst coated membrane before the first gas diffusion layer is secured to the catalyst coated membrane.

[0038] In use, membrane electrode assemblies described herein are typically sandwiched between two rigid plates, known as distribution plates, also known as bipolar plates (BPP's) or monopolar plates. Like the gas diffusion layer, the distribution plate must be electrically conductive. The distribution plate is typically made of a carbon composite, metal, or plated metal material. The distribution plate distributes reactant or product fluids to and from the membrane electrode assembly electrode surfaces, typically through at least one fluid-conducting channel engraved, milled, molded, or stamped in the surface(s) facing the membrane electrode assembly. These channels are sometimes designated a flow field. The distribution plate may distribute fluids to and from two consecutive membrane electrode assemblies in a stack, with one face directing fuel to the anode of the first membrane electrode assembly while the other face directs oxidant to the cathode of the next membrane electrode assembly (and removes product water), hence the term "bipolar plate." Alternately, for example, the distribution plate may have channels on one side only, to distribute fluids to or from a membrane electrode assembly on only that side, which may be termed a "monopolar plate." The term bipolar plate, as used in the art, typically encompasses monopolar plates as well. A typical fuel cell stack comprises a number of membrane electrode assemblies stacked alternately with bipolar plates.

[0039] Membrane electrode assemblies described here are useful, for example, in fuel cells.

Exemplary Embodiments 1A. A membrane electrode assembly comprising a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface, and wherein the major surface of the first microporous layer has discontinuous areas therein substantially free of material, and wherein at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 mm, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, 1mm to 3 mm, or even 1 mm to 2 mm) wide and at least a portion of at least one discontinuous area is in an active area of the first gas diffusion layer.

2A. The membrane electrode assembly of Exemplary Embodiment 1A, wherein at least a portion of the first discontinuous areas substantially free of material are a plurality of channels.

3A. The membrane electrode assembly of Exemplary Embodiment 1A, wherein at least a portion of the first discontinuous areas substantially free of material are a plurality of unconnected channels.

4A. The membrane electrode assembly of Exemplary Embodiment 1A, wherein at least a portion of the first discontinuous areas substantially free of material are a plurality of connected channels.

5A. The membrane electrode assembly of any preceding A Exemplary Embodiment, wherein at least some of the first discontinuous areas have a width in a range from 0.5 mm to 4 mm (in some embodiments in a range from 1 to 3 mm, or even 1 mm to 2 mm).

6A. The membrane electrode assembly of any preceding A Exemplary Embodiment, wherein the first discontinuous areas substantially free of microporous material are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

7A. The membrane electrode assembly of any preceding A Exemplary Embodiment, further comprising a second gas diffusion layer having a second microporous layer on a major surface thereof, wherein the second microporous layer has a major surface, and wherein the major surface of the second microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area is in an active area of the second gas diffusion layer. 8A. The membrane electrode assembly of Exemplary Embodiment 7 A, wherein at least a portion of the second discontinuous areas substantially free of material are a plurality of channels.

9A. The membrane electrode assembly of Exemplary Embodiment 7A, wherein at least a portion of the second discontinuous areas substantially free of material are a plurality of unconnected channels.

1 OA. The membrane electrode assembly of Exemplary Embodiment 7A, wherein at least a portion of the second discontinuous areas substantially free of material are a plurality of connected channels, and wherein at least a portion of at least one discontinuous area is in an active area of the second gas diffusion layer.

1 1A. The membrane electrode assembly of any of Exemplary Embodiments 8 A to 10A, wherein at least a some of the second discontinuous areas have a width of at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 mm, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, lmm to 3 mm, or even 1 mm to 2 mm).

12A. The membrane electrode assembly of any of Exemplary Embodiments 8A to 1 1A, wherein the second discontinuous areas substantially free of material are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

IB. A method of making a membrane electrode assembly, the method comprising:

providing a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface area;

removing a portion of the first microporous layer from the first gas diffusion layer to provide at least a first area on the major surface of the first gas diffusion layer substantially free of first microporous material;

securing the first gas diffusion layer to at least one of the anode or cathode catalyst of the catalyst coated membrane; and securing the remaining the anode or cathode catalyst of the catalyst coated membrane and a second gas diffusion layer

to provide the membrane electrode assembly of any of Exemplary Embodiments 1A to 12A.

2B. The method of Exemplary Embodiment IB, wherein the second gas diffusion layer is secured to the catalyst coated membrane before the first gas diffusion layer is secured to the catalyst coated membrane.

3B. The method of either of Exemplary Embodiment IB or 2B, wherein the first gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane.

4B. The method of either of Exemplary Embodiment IB or 2B, wherein the first gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane.

5B. The method of any of Exemplary Embodiments IB to 4B, wherein removing the portion of the first microporous material from the first gas diffusion layer is done via at least one of laser ablation or adhesive transfer.

6B. The method of any of Exemplary Embodiments IB to 5B, wherein at least a portion of the first area substantially free of first microporous material is a plurality of channels.

7B. The method of any of Exemplary Embodiments IB to 5B, wherein at least a portion of the first area on the major surface of the first gas diffusion layer substantially free of first microporous material is a plurality of connected channels.

8B. The method of Exemplary Embodiments IB to 7B further comprising removing a portion of first microporous material from the first gas diffusion layer to provide at least one additional area (e.g., a second area; a second area and a third area; a second area, third area, and a fourth area, etc.) on the major surface of the first gas diffusion layer substantially free of the first microporous material. 9B. The method of Exemplary Embodiment 8B, wherein at least a portion of the areas on the major surface of the first gas diffusion layer substantially free of first microporous material are a plurality of unconnected channels.

10B. The method of any of Exemplary Embodiments IB to 9B, wherein at least a portion of at least one area on the major surface of the first gas diffusion layer substantially free of first microporous material has a width of at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 mm, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, 1mm to 3 mm, or even 1 mm to 2 mm).

1 IB. The method of any of Exemplary Embodiments IB to 10B, wherein areas substantially free of first microporous material are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

12B. The method of any of Exemplary Embodiments IB to 1 IB, wherein the second gas diffusion layer having a second microporous layer on a major surface thereof, wherein the second microporous layer has a major surface area, and wherein the method further comprises removing a portion of the second microporous layer from the second gas diffusion layer to provide at least a first area on the major surface of the second gas diffusion layer substantially free of second microporous material.

13B. The method of Exemplary Embodiment 12B, wherein removing the portion of second microporous material from the second gas diffusion layer is done via at least one of laser ablation or adhesive transfer.

14B. The method of either Exemplary Embodiment 12B or 13B, wherein at least a portion of the second area substantially free of second microporous material is a plurality of channels.

15B. The method of either Exemplary Embodiment 12B or 13B, wherein at least a portion of the second area on the major surface of the second gas diffusion layer substantially free of second microporous material are a plurality of connected channels. 16B. The method of Exemplary Embodiments 12B to 15B, further comprising removing a portion of the second microporous material from the second gas diffusion layer to provide at least one additional area (e.g., a second area; a second area and a third area; a second area, third area, and a fourth area, etc.) on the major surface of the second gas diffusion layer substantially free of the second microporous material.

17B. The method of Exemplary Embodiment 16B, wherein at least a portion of the areas on the major surface of the second gas diffusion layer substantially free of second microporous material are a plurality of unconnected channels.

18B. The method of any of Exemplary Embodiments 12B to 17B, wherein at least a portion of at least one area on the major surface of the second gas diffusion layer substantially free of second microporous material has a width of at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 mm, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, 1mm to 3 mm, or even 1 mm to 2 mm).

19B. The method of any of Exemplary Embodiments 12B to 18B, wherein areas substantially free of second microporous material are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

1C. A method of making a membrane electrode assembly, the method comprising:

to provide the membrane electrode assembly of any of Exemplary Embodiments 1A to 12A. 2C. The method of Exemplary Embodiment 1C, wherein the second gas diffusion layer is secured to the catalyst coated membrane before the first gas diffusion layer is secured to the catalyst coated membrane.

3C. The method of either of Exemplary Embodiment 1C or 2C, wherein the first gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane.

4C. The method of either of Exemplary Embodiment 1C or 2C, wherein the first gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane.

5C. The method of any of Exemplary Embodiments 1C to 4C, wherein at least a portion of the first area substantially free of material is a plurality of channels.

6C. The method of any of Exemplary Embodiments 1 C to 4C, wherein at least a portion of the first area on the major surface of the first gas diffusion layer substantially free of material is a plurality of connected channels.

7C. The method of any of Exemplary Embodiments 1 C to 6C, wherein at least a portion of at least one area on the major surface of the first gas diffusion layer substantially free of material has a width of at least 0.1 mm (in some embodiments at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.75 mm, 1mm, 2 m, or even at least 4 mm; in some embodiment, in a range from 0.1 mm to 4 mm, 0.2 mm to 4 mm, 0.3 mm to 4 mm, 0.5 mm to 4 mm, 1mm to 3 mm, or even 1 mm to 2 mm).

8C. The method of any of Exemplary Embodiments 1C to 7C, wherein areas substantially free of material are collectively in a range of 1% to 50% (in some embodiments, 1% to 25%, 1% to 10%, or even 1% to 5%) of the major surface of the microporous layer.

9C. The method of any of Exemplary Embodiments 1C to 8C, further comprises coating a microporous layer onto a second gas diffusion layer on a major surface thereof using at least one mask to provide a second gas diffusion layer having a second microporous layer on a major surface thereof, wherein the second microporous layer has a major surface, and wherein the major surface of the second microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area is in an active area of the second gas diffusion layer.

IOC. The method of Exemplary Embodiment 9C, wherein at least a portion of the second area substantially free of material is a plurality of channels.

l lC. The method of Exemplary Embodiment 9C, wherein at least a portion of the second area on the major surface of the second gas diffusion layer substantially free of second material are a plurality of connected channels.

[0040] Foreseeable modifications and alterations of this disclosure will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes.

Claims

What is claimed is:

1. A membrane electrode assembly comprising a first gas diffusion layer having a first microporous layer on a major surface thereof, wherein the first microporous layer has a major surface, and wherein the major surface of the first microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area has a width of at least 0.1 mm wide and at least is in an active area of the first gas diffusion layer.

2. The membrane electrode assembly of claim 1, wherein at least a portion of at least one discontinuous area has a width of at least 0.2 mm wide.

3. The membrane electrode assembly of claim 1, wherein at least a portion of at least one discontinuous area has a width in a range from 0.1 mm to 4 mm.

4. The membrane electrode assembly of any preceding claim, wherein at least a portion of the first discontinuous areas substantially free of material are a plurality of channels.

5. The membrane electrode assembly of any preceding claim, further comprising a second gas diffusion layer having a second microporous layer on a major surface thereof, wherein the second microporous layer has a major surface, and wherein the major surface of the second microporous layer has discontinuous areas therein substantially free of material, and wherein at least a portion of at least one discontinuous area has a width of at least 0.1 mm wide and at least is in an active area of the second gas diffusion layer.

6. A method of making a membrane electrode assembly, the method comprising:

to provide the membrane electrode assembly of any preceding claim..

7. The method of claim 6, wherein the second gas diffusion layer is secured to the catalyst coated membrane before the first gas diffusion layer is secured to the catalyst coated membrane.

8. The method of either of claim 6 or 7, wherein the first gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane.

9. The method of either of claim 6 or 7, wherein the first gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane.

10. The method of any of claims 6 to 9, wherein removing the portion of the first microporous material from the first gas diffusion layer is done via at least one of laser ablation or adhesive transfer.

1 1. A method of making a membrane electrode assembly, the method comprising:

to provide the membrane electrode assembly of any of claims 1 to 6.

12. The method of claim 11, wherein the second gas diffusion layer is secured to the catalyst coated membrane before the first gas diffusion layer is secured to the catalyst coated membrane.

13. The method of either of claim 1 1 or 12, wherein the first gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane.

14. The method of either of claim 11 or 12, wherein the first gas diffusion layer is secured to the cathode catalyst of the catalyst coated membrane, and wherein the second gas diffusion layer is secured to the anode catalyst of the catalyst coated membrane.