Membrane electrode arrangement

Abstract

A membrane electrode assembly comprises an anode, a cathode adjacent to a cathode gas diffusion layer, and a proton exchange membrane (PEM) separating the anode from the cathode. The PEM includes at least one gas recombination layer, at least one ionomer layer, and reinforcement layers. Each of the reinforcement layers comprises a pair of opposing surfaces, with one of the at least one gas recombination layer or one of the at least one ionomer layer adjacent to each of the two opposing surfaces.

Description

[0001] This description generally relates to electrochemical systems, such as fuel cells for converting hydrogen-rich fuels into electricity or electrolyzers for converting water into hydrogen and oxygen. More specifically, aspects of this description relate to a membrane electrode assembly for electrochemical systems.

[0002] An electrolyzer is an electrochemical device that converts water into hydrogen and oxygen using electrolysis. Electrolyzers are typically used to produce hydrogen. Hydrogen is used in many industrial applications, such as ammonia production. Electrolyzers can be used for the localized production of hydrogen, for example, as fuel for vehicles with hydrogen fuel cells. Electrolyzers can also be used to store energy from dynamic power sources such as wind turbines and solar cells.

[0003] Hybrid-electric and fully electric vehicles use a rechargeable energy storage system, such as a high-voltage, high-energy-density battery system (EVB) or a fuel cell system (FCS), to provide the electricity required to operate the vehicle's drivetrain's electric traction motor(s). A fuel cell is an electrochemical device generally consisting of an anode electrode filled with hydrogen (H 2 ), a cathode electrode which is supplied with an oxidizing agent (O 2 ) and an electrolyte barrier between the anode and cathode electrodes. An electrochemical reaction is triggered to oxidize hydrogen molecules on the anode side of the FCS - hydrogen gas is catalytically split in an oxidation half-cell reaction - to produce free electrons ( - ) and free protons (H +). The free hydrogen protons migrate through the electrolyte barrier to the cathode side of the cell, where these protons react with oxygen and electrons in the cathode to form various stacking byproducts, usually water and heat. However, free electrons from the anode are prevented from crossing the electrolyte; these electrons are diverted to a load, such as a vehicle's traction motors and accessories, before being absorbed at the cathode.

[0004] US 2020 / 0 099 061 A1 describes a catalyst-coated membrane (CCM) for use in a water electrolyzer having a laminate structure comprising: a first layer comprising a first membrane component having a cathode catalyst layer disposed on a first surface thereof; a second layer comprising a second membrane component having an anode catalyst layer disposed on a first surface thereof; and an intermediate layer disposed between the first and second layers and comprising a third membrane component having a recombination catalyst layer disposed on a first surface thereof. The CCM is useful in a water electrolyzer.

[0005] WO 2024 / 126749 A1 describes a multilayer proton exchange membrane for water electrolysis, comprising: at least two recombination catalyst layers, each of the at least two recombination catalyst layers comprising a recombination catalyst and a first ion exchange material, wherein at least two recombination catalyst layers are separated by a region that is free of or substantially free of a recombination catalyst, and at least two reinforcement layers, each of the at least two reinforcement layers comprising a microporous polymer structure and a second ion exchange material that is at least partially imbibed into the microporous polymer structure.

[0006] US 2017 / 0 179 514 A1 describes a reinforced composite membrane and a method for producing the reinforced composite membrane and in particular a reinforced composite membrane having a porous support layer and an electrolyte membrane layer formed on one or both surfaces of the porous support layer, wherein at least a part of the porous support layer is impregnated with an electrolyte.

[0007] CN 1 697 225 A describes a membrane as a multilayer proton exchange membrane consisting of a composite proton exchange membrane reinforced by a bilayer porous polymer. The membrane comprises, from the surface to the inner side, the following parts: inorganic nanoparticles and a thin membrane of solid polyelectrolyte; a composite proton exchange membrane reinforced by a porous polymer filled with inorganic nanoparticles and solid polyelectrolyte; inorganic nanoparticles and a thin membrane of solid polyelectrolyte; inorganic nanoparticles and a thin membrane of solid polyelectrolyte; inorganic nanoparticles, Pt metal nanoparticles, and a thin membrane of solid polyelectrolyte.

[0008] CN 1 881 667 A describes a proton exchange film for a fuel battery, in particular a multilayer composite proton exchange film for a self-reinforcing wet fuel battery, wherein the functional film consisting of a supported catalyst and a macromolecular solid electrolyte is arranged on one or two sides of the dense base film.

[0009] A membrane electrode assembly is described herein. The membrane electrode assembly of the invention comprises an anode, a cathode adjacent to a cathode gas diffusion layer, and a proton exchange membrane (PEM) separating the anode from the cathode. The PEM comprises at least one gas recombination layer, at least one ionomer layer, and a plurality of reinforcing layers, each having a pair of opposing surfaces. One of the at least one gas recombination layer or the at least one ionomer layer is disposed adjacent to each of the pair of opposing surfaces. The at least one gas recombination layer comprises an ionomer having at least one gas recombination catalyst. The at least one gas recombination layer comprises a plurality of gas recombination layers, the thickness, uniformity, and composition of which vary for each of the plurality of gas recombination layers.Adjacent reinforcement layers are separated from each other by at least one of the gas recombination layers. The plurality of gas recombination layers comprises different thicknesses, wherein the at least one gas recombination layer between the reinforcement layers is thicker than the gas recombination layer surrounding a perimeter of the membrane. The MEA is arrangeable between pairs of separator plates. The MEA perimeter is a region in which fluids are confined via a pair of separator plates prior to exiting the MEA.

[0010] According to one embodiment, an anode gas diffusion layer is further included, which borders the anode.

[0011] According to a further embodiment, a porous transport layer is included which is adjacent to the anode and is arranged on a side of the anode opposite the PEM.

[0012] According to a further embodiment, one of the plurality of reinforcement layers separates the at least one ionomer layer from the at least one gas recombination layer.

[0013] According to a further embodiment, the plurality of reinforcing layers consists of at least one of the following materials: an ionomer-impregnated woven matrix material or an ionomer-impregnated nonwoven matrix material.

[0014] According to another embodiment, the thickness, matrix and material composition vary for each of the plurality of reinforcement layers.

[0015] According to a further embodiment, the thickness, the matrix and the material composition are the same for each of the reinforcement layers.

[0016] According to a further embodiment, at least one of the reinforcement layers consists of an expanded polytetrafluoroethylene, ePTFE.

[0017] According to a further embodiment, the at least one gas recombination catalyst contains at least one of the elements platinum or palladium and the at least one recombination catalyst is made of at least one of the elements C, SiO 2 , TiO 2 , CEO 2 , Nb 2 O 5 or IrO x worn.

[0018] According to a further embodiment, the at least one gas recombination catalyst is uniformly distributed in at least one of the gas recombination layers.

[0019] According to a further embodiment, the at least one gas recombination catalyst is distributed unevenly in the at least one gas recombination layer.

[0020] According to a further embodiment, the at least one gas recombination catalyst is distributed as particles, fibers or flakes.

[0021] In one application, a vehicle is described. The vehicle includes a vehicle body, wheels supporting the vehicle body, an electric motor configured to drive the wheels, and a battery configured to supply electrical energy to the electric motor. The vehicle also includes a fuel cell configured to provide power to the battery and / or the electric motor. The fuel cell includes a membrane electrode assembly according to the invention and its embodiments. Fig. 1 is an elevated perspective view of a representative motor vehicle with an inset schematic of a rechargeable energy storage system including a traction battery pack and a fuel cell system for operating the electric motor(s) of an electrified powertrain. Fig. Figure 2 is a schematic view of an electrolysis system. Fig. 3 is a cross-sectional view of a cell stack in an electrolyzer of the electrolysis system of Fig. 2. Fig. 4 shows an example of a membrane electrode assembly for use in the electrolysis system of Fig. 2. Fig. Figure 5 shows a proton exchange membrane for use in either the fuel cell system of Fig. 1 or in the electrolysis system of Fig. 2. Fig. Figure 6 shows a proton exchange membrane for use in either the fuel cell system of Fig. 1 or in the electrolysis system of Fig. 2. Fig. Figure 7 shows a proton exchange membrane for use in either the fuel cell system of Fig. 1 or in the electrolysis system of Fig. 2. Fig. Figure 8 shows a proton exchange membrane for use in either the fuel cell system of Fig. 1 or in the electrolysis system of Fig. 2.

[0022] This description may be embodied in many different forms. Representative embodiments of the description are illustrated in the drawings and are described in detail herein, with the understanding that these embodiments serve as examples of the principles described and are not limitations on the general aspects of the description. As such, elements and limitations described, for example, in the "Summary," "Introduction," "Description," and "Detailed Description" sections, but not expressly recited in the claims, should not be incorporated into the claims, individually or in the aggregate, by implication, inference, or otherwise.

[0023] For the purposes of this detailed description, unless expressly excluded: the singular includes the plural and vice versa; the words "and" and "or" apply in both the subjunctive and disjunctive moods; the words "each" and "all" mean "each and all"; and the words "including," "including," "comprising," "with," and the like each mean "including without limitation." Furthermore, words of approximation such as "approximately," "almost," "substantially," "generally," "about," and the like may be used herein to mean "at, near, or almost at," or "within 0-5% of," or "within acceptable manufacturing tolerances," or any logical combination thereof, for example.Finally, directional adjectives and adverbs such as "front", "rear", "inside", "outside", "starboard", "port", "vertical", "horizontal", "up", "down", "forward", "backward", "left", "right", etc., may refer to a motor vehicle, for example, the forward travel of a motor vehicle when the vehicle is operated on a horizontal driving surface.

[0024] With reference to the figures, in which like reference numerals refer to like features in the several views, Fig. 1 depicts a representative automobile, generally designated 10, which is depicted here for discussion purposes as a sedan-style fuel cell electric vehicle (FCEV). The depicted automobile 10—also referred to herein as a “motor vehicle” or “vehicle” for short—is merely an exemplary application with which new aspects of this description may be practiced. Likewise, the incorporation of the present concepts into an all-electric powertrain should be understood as a non-limiting implementation of the described features. It is understood that aspects and features of this description may be applied to other powertrain architectures, utilized for a variety of different fuel cell system configurations, and incorporated into any logically relevant vehicle type.In addition, selected components of the motor vehicles, FCS, and manufacturing systems are shown and described in additional detail herein. Nevertheless, the vehicles and systems described below may include numerous additional and alternative features and other available peripheral components to perform the various methods and functions of this disclosure.

[0025] A representative fuel cell system 14 is located in a vehicle body 12 forming the passenger compartment of a motor vehicle 10 for driving a prime mover, for example, an electric motor-generator unit (MGU) 16, which serves to drive a combination of vehicle wheels 18. An electrochemical system, such as the proton exchange membrane fuel cell system 14 in Fig. 1, is equipped with one or more fuel cell stacks 20, each consisting of a plurality of PEM-type fuel cells 22 stacked and electrically connected in series or parallel to one another. In the illustrated architecture, each fuel cell 22 is a multi-layer construction having an anode side 24 and a cathode side 26 separated by a proton-conducting semipermeable polymer membrane 28. On the anode side 24 of the PEMFC 22 is an anode gas diffusion electrode (GDE) layer 30 with an anode catalyst layer 32 disposed on top of the GDE layer 30 or sandwiched between the membrane 28 and the corresponding GDE layer 30, operatively connecting them. In addition to the anode layers 30 and 32 there is a cathode gas diffusion electrode (GDE) layer 34, which is provided on the cathode side 26 of the PEMFC 22.A cathode catalyst layer 36 is disposed on or between the GDE layer 34 and interconnects the membrane 28 and the corresponding GDE layer 34. The two GDE layers 30 and 34, the two catalyst layers 32 and 36, and optional subgaskets (see . Fig. 2 below) together with the membrane 28 form, in whole or in part, a membrane electrode assembly (MEA) 38.

[0026] The gas diffusion layers 30 and 34 may be porous structures that allow fluid inlet into and outlet from the MEA 38. An anode flow field plate 40 (with optional bipolar plate) is provided on the anode side 24 in abutting relationship with the anode GDE layer 30. Similarly, a cathode flow field plate 42 (with optional bipolar plate) is provided on the cathode side 26 in abutting relationship with the cathode GDE layer 34. Coolant channels 44 traverse each of the plates 40 and 42 to allow coolant to flow through the fuel cell 22. Fluid inlet ports and manifolds direct a hydrogen-rich fuel and an oxidizer to the respective passages in the anode and cathode flow field plates 40, 42.A central active region of the anode flow field plate 40, facing the proton-conducting membrane 28, may be provided with an anode flow field consisting of serpentine flow channels for distributing hydrogen across an opposing surface of the GDE layer 30 and the membrane 28. The MEA 38 and the flow field plates 40, 42 may be stacked together between current collector plates and monopolar end plates (not shown). The fuel cell system 14 may also utilize anode recycle, in which an anode recycle gas is supplied from an exhaust manifold or manifold through an anode recycle line to recycle hydrogen back to the inlet of the anode side 24 and conserve hydrogen gas in the stack 20.

[0027] The hydrogen inlet (H 2) - whether gaseous, concentrated, entrained, or otherwise - is supplied from a hydrogen source, for example, a fuel reservoir 46, via a fluid injection nozzle 47 connected to a (first) fluid inlet line or hose 48, to the anode side 24 of the fuel cell stack 20. The anode exhaust gas leaves the stack 20 via a (first) fluid exhaust line or hose 50. On the inlet (left) side of the stack 20 is a compressor or pump 52 which supplies a cathode inlet stream, for example, ambient air and / or concentrated gaseous oxygen (O 2), via a (second) fluid inlet line or manifold 54 to the cathode side 26 of the stack 20. The cathode exhaust gases are discharged from the stack 20 via a (second) fluid exhaust line or manifold 56. Flow control valves, flow restrictors, filters, and other available devices for regulating the fluid flow can be used in the PEMFC system 14 of Fig. 1. The power generated by the fuel cell stack(s) 20 and output by the fuel cell system 14 may be transferred to an on-vehicle traction battery pack 82 within a rechargeable energy storage system (RESS) 80 for storage.

[0028] The fuel cell system 14 from Fig. 1 may also include a thermal subsystem for controlling the temperature of the fuel cell stack 20, for example, during preconditioning, break-in, and postconditioning. According to the illustrated example, a cooling pump 58 pumps a cooling fluid through a coolant circuit 60 to the fuel cell stack 20 and into the cooling channels 44 in each cell 22. A cooler 62 and an optional heater 64, connected to the coolant circuit 60, are used to maintain the stack 20 at a desired operating temperature. This thermal subsystem may be equipped with various instruments for monitoring regular system operation as well as the progress of fuel cell conditioning and break-in.For example, a (first) inlet temperature sensor 66 monitors the temperature of the coolant at the coolant inlet of the fuel cell stack 20, and a (second) outlet temperature sensor 68 measures the temperature of the coolant at the coolant outlet of the stack 20. An electrical connector or cable 74 connects the fuel cell stack 20 to an electrical load 76, which can be used to draw power from each cell 22 in the stack 20. A voltage / current sensor 70 is used to measure, monitor, or otherwise sense the fuel cell voltage and / or current at the fuel cells 22 in the stack 20.

[0029] A programmable electronic control unit (ECU) 72 helps control the operation of the fuel cell system 14. For example, the ECU 72 receives one or more temperature signals T1 from one or more of the temperature sensors 66, 68 that indicate the temperature of the fuel cell stack 20; the ECU 72 can be programmed to then output one or more command signals C1 to modulate the operation of the stack 20. The ECU 72 of Fig. 1 also receives one or more voltage signals V1 from the voltage sensor / current sensor 70; the ECU 72 can be programmed to then output one or more command signals C2 to modulate the operation of a hydrogen source (e.g., the fuel storage 46) and / or the compressor / pump 52, thereby regulating the electrical power of the stack 20. The ECU 72 of Fig. 1 is also shown receiving one or more coolant temperature signals T2 from sensors 66 and / or 68; the ECU 72 may be programmed to then output one or more command signals C3 to modulate the operation of the fuel cell thermal subsystem. Additional sensor signals S N can be received by the ECU 72 and additional control commands C N may be output simultaneously by the ECU 72, for example, to control any other subsystem or component shown and / or described herein. The ECU 72 may output a command signal to control the resulting hydrogen and liquid H 2 O from the cathode side 26 through the fluid outlet line 56 to a water separator 78 ( Fig. 1) where hydrogen and water from the cathode are combined with the spent hydrogen expelled from the anode through the fluid outlet line / hose 50.

[0030] With further reference to Fig. 1, the traction battery pack 82 includes a series of rechargeable lithium-class (secondary) battery modules 84. Aspects of the described concepts may be similarly applicable to other electrical storage architectures, including those employing nickel-metal hydride (NiMH) batteries, lead-acid batteries, lithium-metal batteries, or other rechargeable electric vehicle (EVB) batteries. Each battery module 84 may include a stack or group of electrochemical battery cells, such as lithium-ion (Li-ion) or Li-ion polymer battery cells 86. For example, a single battery module 84 may consist of a grouping of 10-80 lithium-ion battery cells stacked side by side and connected in parallel or series to store and deliver electrical energy.Although the cells 86 are described as silicon-based Li-ion batteries (“pouch cells”), they can also be adapted to other designs, including cylindrical and prismatic designs.

[0031] Fig. 2 is a schematic top view of a portion of an electrolysis system 100. In the illustrated example, the electrolysis system 100 includes an electrolyzer, such as a proton exchange membrane (PEM) electrolyzer. In one example, the PEM electrolyzer includes a cell bank comprised of a plurality of stacked cells (e.g., in series), each cell comprising various components, including various membrane electrode assembly (MEA) components. The MEA components include a solid polymer membrane (i.e., a proton exchange membrane, or PEM) disposed between an anode and a cathode. The MEA components comprising the cathode include a catalyst layer disposed adjacent to a gas diffusion layer (GDL). The MEA components comprising the anode also include a catalyst layer adjacent to a porous transport layer (PTL).The PEM selectively allows positively charged hydrogen ions to pass through the membrane between the anode and the cathode to convert water into hydrogen and oxygen during the electrolysis process.

[0032] As in Fig. 2, the electrolysis system 100 includes a water source 102 in fluid communication with an electrolyzer stack 110 via a conduit 104 to supply a water feedstock to the electrolyzer stack 110. Unused, remaining, and / or byproduct water is returned from the electrolyzer stack 110 to the water source 102 via a return conduit 114. Additionally, a power source 106 and power electronics 116 are in fluid communication with the electrolyzer stack 110 via conduits 108 and 114, respectively. In one or more embodiments of the disclosure, a hydrogen storage device 118 is in fluid communication with the electrolyzer stack 110 via conduit 112 to receive the hydrogen product produced in the electrolyzer stack 110 during electrolysis, as further explained below.

[0033] As shown, the electrolyzer stack 110 receives electricity (i.e., an electric current) from the power source 106 via line 108 and water from the water source 102 via line 104. The electrolyzer stack 110 converts the water from the water source 102 into hydrogen and oxygen through electrolysis using the power supplied by the power source 106. The hydrogen gas is discharged from the electrolyzer stack 110 as a hydrogen product stream and conveyed to the hydrogen storage 118 via line 112.

[0034] During operation of the electrolysis system 100, the power source 106 supplies direct current to the electrolyzer stack 110. Examples of power sources include batteries, solar cells, direct current generators, wind turbines, hydroelectric power plants, and / or the like.

[0035] The power electronics 116 is in communication with the electrolyzer stack 110 and is configured to control the operation of the electrolyzer stack 110. For example, the power electronics 116 can control the voltage and current supplied to the electrolyzer stack 110 from the power source 106.

[0036] Fig. 3 shows a cross-sectional view of the electrolyzer stack 110 along line 3-3 of Fig. 2. In one or more embodiments of the description, the electrolyzer stack 110 comprises a cell block 180 formed from a plurality of cells 182.

[0037] The plurality of cells 182 includes a plurality of gaskets 142 and a plurality of separator plates 140. The cells in the plurality of cells 182 are stacked in the cell block 180 and electrically connected in series. Each cell in the plurality of cells 182 includes various components, including the membrane electrode assembly (MEA) 138, a pair of separator plates 140, and a pair of gaskets 142.

[0038] The pair of separator plates (of the plurality of separator plates 140) include flow channels connected to the MEA 138 and allowing the flow of fluids (e.g., water, hydrogen gas, and oxygen gas) to or from the MEA 138. Each separator plate 140 is electrically conductive and facilitates the transport of electrons to assist in establishing the electrical circuit of the electrolysis process.

[0039] As in Fig. 4, the MEA 138 includes a solid polymer membrane (i.e., proton exchange membrane 28 or PEM), an anode 132 (i.e., anode catalyst layer), and a cathode 136 (i.e., cathode catalyst layer). The PEM 28 is disposed between the anode catalyst layer 132 and the cathode catalyst layer 136. The cathode catalyst layer 136 is disposed adjacent to a gas diffusion layer (GDL) 134. Likewise, the anode catalyst layer 132 is disposed adjacent to a porous transport layer (PTL) 130. In the case of fuel cells, a GDL is used instead of the PTL. The PEM 28 contains an active zone where the electrochemical reaction to convert water to hydrogen by electrolysis takes place. The PEM 28 selectively allows positively charged hydrogen ions to pass through the membrane between the anode 132 and the cathode 136 as part of the electrolysis process to convert water into hydrogen and oxygen.

[0040] Each cell 182 is constructed such that the MEA 138 is disposed between pairs of separator plates 140. The pair of seals (one of the plurality of seals 142) prevents fluids (e.g., water, hydrogen gas, and oxygen gas) from escaping from the interface between the MEA 138 and the pair of separator plates 140. The pair of seals 142 defines an MEA perimeter. The MEA perimeter is an area where fluids are confined prior to exiting the MEA 138 via the pair of separator plates 140.

[0041] As in Fig. 5, the membrane 28 comprises a plurality of gas recombination layers 28-G and a plurality of reinforcement layers 28-R. In the illustrated example, adjacent reinforcement layers 28-R are separated from each other by at least one of the gas recombination layers 28-G. An ionomer layer 28-I is located immediately adjacent to one of the plurality of reinforcement layers 28-R. A feature of the plurality of reinforcement layers 28-R is to reduce the formation of cracks in the membrane 28.

[0042] At least one of the reinforcement layers 28-R separates the ionomer layer 28-I from the plurality of gas recombination layers 28-G. The reinforcement layers 28-R consist of at least one ionomer-impregnated woven matrix material or one ionomer-impregnated nonwoven matrix material. In the illustrated example, the thickness of each of the plurality of reinforcement layers 28-R is the same, with the matrix or composition being the same or different between the layers. At least one of the plurality of reinforcement layers may consist of an expanded polytetrafluoroethylene (ePTFE).

[0043] The gas recombination layers 28-G may contain an ionomer with at least one gas recombination catalyst. The gas recombination catalyst may contain at least one of the elements platinum or palladium. The gas recombination catalyst is supported by a support structure containing at least one of the elements C, SiO 2 , TiO 2, CEO 2 , Nb 2 O 5 or IrOx. The gas recombination catalyst may be uniformly or non-uniformly distributed in at least one of the gas recombination layers. Furthermore, the gas recombination catalyst may be distributed in the form of particles, fibers, or flakes in the gas recombination layer 28-G. The gas recombination layers 28-G may have a gas recombination catalyst loading of between about 0.1% and 99.9%. In another example, the gas recombination layers 28-G may have a gas recombination catalyst loading of between about 0.1% and 50%.

[0044] The gas recombination layers 28-G may also overlap with the reinforcement layers to an extent of 0 to 100%. In the example shown, the thickness of each of the gas recombination layers 28-G is the same, with the uniformity or composition between the layers being the same or different. One feature of the gas recombination layers 28-G is a reduction in hydrogen or oxygen permeation through the membrane 28.

[0045] Fig. Figure 6 shows another example of a diaphragm 228 that is similar to diaphragm 28, except where shown in the drawings or described below. Similar or identical elements between diaphragm 228 and diaphragm 28 contain the same numbering with the addition of a leading "2" in Fig. 6. As in Fig. 6, the gas recombination layers 228-G have different thicknesses, with the gas recombination layer 228-G between the reinforcement layers 228-R being thicker than the gas recombination layer 228-G in the vicinity of a perimeter of the membrane 228.

[0046] Fig. Figure 7 shows another example of a diaphragm 328 that is similar to diaphragm 28, except where shown in the drawings or described below. Similar or identical elements between diaphragm 328 and diaphragm 28 are numbered the same, with Fig. 7 a leading “3” is added. As in Fig. 7, an ionomer layer 328-I is located in the center of the membrane 328, with a first reinforcement layer 328-R separating the ionomer layer in the center from another ionomer layer 328-I on a first side, and a second reinforcement layer 328-R separating the middle ionomer layer 328-I from a gas recombination layer 328-G on a second side.

[0047] Fig. Figure 8 shows another example membrane 428 that is similar to membrane 28 except where shown in the drawings or described below. Similar or identical elements between membrane 428 and membrane 28 are numbered the same, with Fig. 8 a leading “4” is added. As in Fig.As shown in Figure 8, a gas recombination layer 428-G is located in the center of the membrane 428 and is surrounded by reinforcing layers 428-R. An ionomer layer 428-I is located adjacent to each of the reinforcing layers 428-R, opposite the gas recombination layer 428-G, which is located between the reinforcing layers 428-R.

[0048] The terms "a" and "an" do not imply a limitation of quantity, but denote the presence of at least one of the mentioned elements. The term "or" means "and / or" unless the context clearly indicates otherwise. Whenever "an aspect" is mentioned throughout the description, this means that a particular element (for example, a feature, structure, step, or property) described in connection with the aspect is included in at least one of the aspects described therein and may or may not be present in other aspects. Furthermore, the described elements in the different aspects may be combined as appropriate.

[0049] When an element, such as a layer, film, region, or substrate, is described as being "on" another element, it may be directly on top of the other element, or there may be intervening elements. Conversely, when an element is described as being "directly on" another element, there are no intervening elements.

[0050] Unless otherwise specified herein, examination standards shall be deemed to be the most recent standards in force on the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0051] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this description belongs.

Claims

[1] Membrane electrode assembly (138), MEA, comprising: an anode (132); a cathode (136) adjacent to a cathode gas diffusion layer; and a proton exchange membrane, PEM, (228) separating the anode (132) from the cathode (136); wherein the PEM (228) comprises: at least one gas recombination layer (228-G); at least one ionomer layer (228-I); and a plurality of reinforcement layers (228-R), each having a pair of opposing surfaces, wherein one of the at least one gas recombination layer (228-G) or the at least one ionomer layer (228-I) is disposed adjacent to each of the pair of opposing surfaces; wherein the at least one gas recombination layer (228-G) comprises an ionomer with at least one gas recombination catalyst; wherein the at least one gas recombination layer (228-G) comprises a plurality of gas recombination layers (228-G) whose thickness, uniformity, and composition vary for each of the plurality of gas recombination layers (228-G); wherein adjacent reinforcement layers (228-R) are separated from one another by at least one of the gas recombination layers (228-G); wherein the plurality of gas recombination layers (228-G) comprise different thicknesses, wherein the at least one gas recombination layer (228-G) between the reinforcement layers (228-R) is thicker than the gas recombination layer (228-G) in the vicinity of an MEA perimeter of the membrane (228); wherein the MEA (138) is displaceable between pairs of separator plates (140); wherein the MEA perimeter is an area in which the fluids are confined via a pair of separator plates (140) prior to leaving the MEA (138). [2] The membrane electrode assembly (138) of claim 1 having an anode gas diffusion layer adjacent to the anode (132). [3] Membrane electrode assembly (138) according to claim 1, comprising a porous transport layer (130) adjacent to the anode (132) and arranged on a side of the anode (132) opposite the PEM (228). [4] The membrane electrode assembly (138) of claim 1, wherein one of the plurality of reinforcement layers (228-R) separates the at least one ionomer layer (228-I) from the at least one gas recombination layer (228-G). [5] The membrane electrode assembly (138) of claim 1, wherein the plurality of reinforcing layers (228-R) are made of at least one of the following materials: an ionomer-impregnated woven matrix material or an ionomer-impregnated non-woven matrix material. [6] The membrane electrode assembly (138) of claim 5, wherein the thickness, matrix, and material composition vary for each of the plurality of reinforcement layers (228-R). [7] The membrane electrode assembly (138) of claim 5, wherein the thickness, matrix, and material composition are the same for each of the plurality of reinforcement layers (228-R). [8] The membrane electrode assembly (138) of claim 5, wherein at least one of the plurality of reinforcing layers (228-R) is made of expanded polytetrafluoroethylene, ePTFE.

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