Microporous layers within electrochemical cells

Abstract

The following disclosure relates to electrochemical or electrolysis cells and components thereof, specifically to a microporous layer positioned between a gas diffusion layer and a membrane within an electrochemical cell. The microporous layer may include a carbon-based compound and a binder. Further, the composition of the microporous layer may have a porous structure configured to transport fluids through the microporous layer to the gas diffusion layer or the membrane of the electrochemical cell.

Description

MICROPOROUS LAYERS WITHIN ELECTROCHEMICAL CELLS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 530,002, filed July 31, 2023, which is hereby incorporated by reference in its entirety.FIELD

[0002] The following disclosure relates to electrochemical or electrolysis cells and components thereof. More specifically, the following disclosure relates to microporous layers within electrochemical cells that are configured to reduce a risk of electrical shorting and improve fluid management within the electrochemical cells.BACKGROUND

[0003] Hydrogen has been considered as an ideal energy carrier to store renewable energy. Proton exchange membrane water electrolysis (PEMWE) as a means for hydrogen production offers high product purity, fast load response times, small footprints, high efficiencies, and low maintenance efforts. It is regarded as a promising technology, especially when coupled with renewable energy sources.

[0004] PEMWEs and polymer electrolyte membrane fuel cells (PEMFCs) share similar device architecture. While PEMFCs electrochemically convert hydrogen and oxygen gas into water, PEMWEs perform the opposite reaction, i.e., an electrochemical conversion or splitting of water to hydrogen and oxygen gases. PEMFCs are more commercially established, so PEMWEs have used materials developed for PEMFCs in certain cases. However, there are key operational environment differences between PEMFCs and PEMWEs that result in different material property requirements.

[0005] Therefore, there remains a desire for an improved interface between the gas diffusion layer (GDL) and membrane on the cathode side of the electrochemical cell.SUMMARY

[0006] In one embodiment, a microporous layer (MPL) for an electrochemical cell is provided. The MPL includes: a carbon-based compound; and a binder, wherein the MPL is configured to be positioned between a gas diffusion layer (GDL) and a membrane within the electrochemical cell, wherein a composition of the MPL has a porous structure configured to transport fluids through the MPL to the GDL or the membrane. In certain examples, thecomposition of the MPL has a greater affinity for water than a composition of the GDL therein allowing for a greater transport of water through a combination of the MPL and the GDL in comparison to the GDL alone.

[0007] In another embodiment, an electrochemical cell is provided. The electrochemical cell includes: a proton exchange membrane (PEM); a gas diffusion layer (GDL); and a microporous layer (MPL) positioned between the PEM and GDL, wherein a composition of the MPL has a porous structure configured to transport fluids through the MPL to the GDL or the PEM. In certain examples, the composition of the MPL has a greater affinity for water than a composition of the GDL therein allowing for a greater transport of water through a combination of the MPL and the GDL in comparison to the GDL alone.

[0008] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Exemplary embodiments are described herein with reference to the following drawings.

[0010] Figure 1 depicts an example of an electrochemical cell.

[0011] Figure 2 depicts an additional example of an electrochemical cell.

[0012] Figure 3A depicts an example of a hydrophobic microporous layer (MPL).

[0013] Figure 3B depicts an example of a hydrophilic MPL.

[0014] Figure 4 depicts an additional example of an electrochemical cell having an MPL.DETAILED DESCRIPTION

[0015] The following disclosure provides an improved interface between the gas diffusion layer (GDL) and membrane on the cathode side of the electrochemical cell through the addition of a microporous layer (MPL) on the cathode side of the electrochemical cell.Definitions

[0016] As used herein, "providing" may refer to the provision of, generation or, presentation of, or delivery of that which is provided. Providing may include making something available. For example, providing a powder may refer to a process of making thepowder available, or delivering the powder, such that the powder can be used as set forth in a method described herein. As used herein, providing also may refer to measuring, weighing, transferring, combining, or formulating.

[0017] As used herein, a "thickness" by which is film is characterized refers to the distance, or median measured distance, between the top and bottom faces of a film in a direction perpendicular to the plane of the film layer. As used herein, the top and bottom faces of a film refer to the sides of the film extending in a parallel direction of the plane of the film having the largest surface area.

[0018] As used herein, the term "hydrophilic" may refer to a property of a layer or coating that has a stronger affinity for water (i.e., is more hydrophilic) in comparison to another layer. For example, a hydrophilic porous layer or coating will allow a larger amount of water to be transported through the pores of the layer / coating in comparison to the GDL alone (which represents a more hydrophobic porous layer). In other words, a hydrophilic microporous layer (MPL) may refer to a MPL that has a stronger affinity for water (allowing a greater transport of water through the MPL) than the GDL itself. Nevertheless, physical or chemical properties of the hydrophilic MPLs disclosed herein may overall still be slightly hydrophobic, but the physical or chemical properties of the hydrophilic MPL are just less hydrophobic in comparison to the water affinity properties of the GDL.Electrochemical Cells

[0019] Figure 1 depicts an example of an electrochemical or electrolytic cell for hydrogen gas and oxygen gas production through the splitting of water. The electrolytic cell includes a cathode, an anode, and a membrane positioned between the cathode and anode. The membrane may be a proton exchange membrane (PEM). Proton Exchange Membrane (PEM) electrolysis involves the use of a solid electrolyte or ion exchange membrane. Within the water splitting electrolysis reaction, one interface runs an oxygen evolution reaction (OER) while the other interface runs a hydrogen evolution reaction (HER). For example, the anode reaction is H2O->2H++1 / 2O2+2e and the cathode reaction is 2H++2e->H2. The water electrolysis reaction has recently assumed great importance and renewed attention as a potential foundation for a decarbonized "hydrogen economy." Other types of electrolyzers may be used as well.

[0020] Since the performance of a single electrolytic cell may not be adequate for many use cases, multiple cells may be placed together to form a "stack" of cells, which may be referred to as an electrolyzer stack, electrolytic stack, electrochemical stack, or simply just a stack. In certain examples, a stack may contain 50-1000 cells, 50-100 cells, 500-700 cells, or more than 1000 cells. Any number of cells may make up an electrochemical stack.

[0021] The electrochemical cells within the electrochemical stack may be configured to operate with 200 mV or less of pure resistive loss when operating at a high current density (e.g., at least 3 Amp / cm2at least 4 Amps / cm2, at least 5 Amps / cm2, at least 6 Amps / cm2, at least 7 Amps / cm2, at least 8 Amps / cm2, at least 9 Amps / cm2, at least 10 Amps / cm2, or at least 11 Amps / cm2, at least 12 Amps / cm2, at least 13 Amps / cm2, at least 14 Amps / cm2, at least 15 Amps / cm2, at least 16 Amps / cm2, at least 17 Amps / cm2, at least 18 Amps / cm2, at least 19 Amps / cm2, at least 20 Amps / cm2, at least 25 Amps / cm2, at least 30 Amps / cm2, in a range of 1-30 Amps / cm2, in a range of 3-30 Amps / cm2, in a range of 3-20 Amps / cm2, in a range of 3-15 Amps / cm2, in a range of 3-10 Amps / cm2, or in a range of 10-20 Amps / cm2). In additional examples, the amount of water (e.g., deionized (DI) water) transferred to or circulated through each cell of the stack may be in a range of 0.25-1 mL / Amp / cell / min, in a range of 0.25-5 mL / Amp / cell / min, or in a range of 0.5-1 mL / Amp / cell / min.

[0022] Figure 2 depicts an additional example of an electrochemical or electrolytic cell. Specifically, Figure 2 depicts a portion of an electrochemical cell 200 having a cathode flow field 202, an anode flow field 204, and a membrane 206 positioned between the cathode flow field 202 and the anode flow field 204.

[0023] In certain examples, the membrane 206 may be a catalyst coated membrane (CCM) having a cathode catalyst layer 205 and / or an anode catalyst layer 207 positioned on respective surfaces of the membrane 206. As used throughout this disclosure, the term "membrane" may refer to a catalyst coated membrane (CCM) having such catalyst layers. In certain examples, the membrane 206 (that, in some examples, may include the anode catalyst layer 207 and cathode catalyst layer 205) may have an overall thickness that is less than 1000 microns, 500 microns, 100 microns, 50 microns, 10 microns, etc.

[0024] In certain examples, additional layers may be present within the electrochemical cell 200. These additional layers may include porous media sandwiching the CCM andconfigured to facilitate the transport of fluids (i.e., water to the electrodes and gases from the electrodes) as well as provide electrical conductivity to the electrodes.

[0025] For example, one or more additional layers 208 may be positioned between the cathode flow field 202 and membrane 206. In certain examples, this may include a gas diffusion layer (GDL) 208 may be positioned between the cathode flow field 202 and membrane 206. This may be advantageous in providing a hydrogen diffusion barrier adjacent to the cathode on one side of the multi-layered membrane to mitigate hydrogen crossover to the anode side. In other words, the GDL is a porous media responsible for the transport of gaseous hydrogen to the cathode side flow field. For a wet cathode PEM operation, liquid water transport across the GDL is needed for heat removal in addition to heat removal from the anode side. In certain examples, the GDL 208 may be made of carbon fibers. In certain examples, the thickness of the GDL 208 may be in a range of 100-1000 microns.

[0026] Similarly, one or more additional layers 210 may be present in the electrochemical cell between the membrane 206 and the anode 204. In certain examples, this may include a porous transport layer (PTL) positioned between the membrane 206 (e.g., the anode catalyst layer 207 of the catalyst coated membrane 206) and the anode flow field 204.

[0027] Similar to the GDL, the PTL is a porous media configured to allow the transportation of the reactant water to the anode catalyst layers, remove produced oxygen gas, and provide good electrical conductivity for effective electron conduction. In other words, liquid water flowing in the anode flow field is configured to permeate through the PTL to reach the CCM. Further, gaseous byproduct oxygen is configured to be removed from the PTL to the flow fields. In such an arrangement, liquid water functions as both reactant and coolant on the anode side of the cell.

[0028] In certain examples, the thickness of the PTL may be in a range of 100-1000 microns. The thickness of the PTL may affect the mass transport within the cell as well as the durability / deformability and electrical / thermal conductivity of the PTL. In other words, thinner PTLs compared to thicker PTLs (e.g., 1 mm) may provide better mass transport. However, when the PTL is too thin (e.g., less than 100 microns), the PTL may suffer frompoor two phase flow effects as well. PTLs are less prone to deformation compared to GDLs. Thickness of PTLs may also affect lateral electron conduction resistance along the lands in between channels.

[0029] The cathode flow field 202 and anode flow field 204 of the cell may individually include a flow field plate composed of metal, carbon, or a composite material having a set of channels machined, stamped, or etched into the plate to allow fluids to flow inward toward the membrane or out of the cell.

[0030] An improved electrochemical or electrolysis cell is desired with an efficient interchange on the cathode side of the cell. Specifically, as disclosed in greater detail below, a microporous layer (MPL) positioned adjacent to or coating the GDL is provided to improve the properties / performance on the cathode side of the cell. For example, the MPL may be advantageous in providing: (1) an electrically conductive interface, (2) a thermally conductive interface, (3) mechanical compliance to prevent electrical shorting, and (4) improved fluid (i.e., water and gas) management within the cell.

[0031] Such a MPL differs from the state of the art with regard to fuel cells / PEMFCs. Specifically, electrochemical cells or PEMWEs are configured to operate at significantly higher current densities than fuel cells. As noted above, the electrochemical cells disclosed herein may be configured to operate with 200 mV or less of pure resistive loss when operating at a high current density (e.g., at least 3 Amp / cm2at least 4 Amps / cm2, at least 5 Amps / cm2, at least 6 Amps / cm2, at least 7 Amps / cm2, at least 8 Amps / cm2, at least 9 Amps / cm2, at least 10 Amps / cm2, or at least 11 Amps / cm2, at least 12 Amps / cm2, at least 13 Amps / cm2, at least 14 Amps / cm2, at least 15 Amps / cm2, at least 16 Amps / cm2, at least 17 Amps / cm2, at least 18 Amps / cm2, at least 19 Amps / cm2, at least 20 Amps / cm2, at least 25 Amps / cm2, at least 30 Amps / cm2, in a range of 1-30 Amps / cm2, in a range of 3-30 Amps / cm2, in a range of 3-20 Amps / cm2, in a range of 3-15 Amps / cm2, in a range of 3-10 Amps / cm2, or in a range of 10-20 Amps / cm2).

[0032] Due to the higher operating current densities, the electrochemical cells or PEMWEs disclosed herein require higher electrical and thermal conductivity to reduce polarization and remove excess heat from the catalyst layers. As such, having a MPL within the electrochemical cell that is electrically and thermally conductive is advantageous.

[0033] Further, while fuel cells or PEMFCs use a symmetric structure of flexible carbonbased porous media on both electrodes, electrochemical cells or PEMWEs may use a noncompliant titanium porous transport layer (PTL) as the fluid transport layer on the anode side and are thus more prone to electrical shorting if the membrane is punctured. As such, it is advantageous to protect or cushion the membrane from being punctured by carbon fibers of the GDL. The addition of a MPL that is adjacent to or coats a surface of the GDL is advantageous in providing such a mechanical compliance, therein reducing the chance of a membrane puncture or electrical shorting.

[0034] Finally, electrochemical cells or PEMWEs draw water into the active area at the membrane for the water splitting reaction. In contrast, fuel cells PEMFCs expel the water generated using a hydrophobic layer to exclude water vapor and prevent the water vapor from condensing into liquid water.

[0035] Figures 3A and 3B depict examples of the difference between a hydrophobic MPL and a hydrophilic MPL. In other words, the hydrophilic MPL may refer to a layer or coating that has a stronger affinity for water (allowing a greater transport of water through the MPL) than the GDL itself. Nevertheless, physical or chemical properties of the hydrophilic MPLs disclosed herein may overall still be slightly hydrophobic, but the physical or chemical properties of the hydrophilic MPL are just less hydrophobic in comparison to the water affinity properties of the GDL.

[0036] Specifically, in Figure 3A, a more hydrophobic microporous layer (in comparison with the microporous layer in Figure 3B) is positioned adjacent to a gas diffusion layer. A larger volume of water is repelled from reaching the gas diffusion layer due to the hydrophobic properties of the microporous layer. In contrast, in Figure 3B, a more hydrophilic microporous layer (in comparison with the microporous layer in Figure 3A) is positioned adjacent to a gas diffusion layer. The more hydrophilic properties of the microporous layer within the example in Figure 3B allow for a larger volume of water to flow through the pores of the layer to reach and pass through the gas diffusion layer.

[0037] The addition of such a hydrophilic MPL may advantageously improve or optimize water transport and hydration in PEMWEs, in contrast to the state of the art known within fuel cells / PEMFCs.

[0038] While Figures 3A and 3B disclose non-limiting examples of microporous layers that are more hydrophilic than the adjacently positioned gas diffusion layer, other alternative microporous layer compositions and properties are also possible. For instance, the MPL may be composed of a composition that is thermally and electrically conductive in nature, for example, while being more hydrophobic that the GDL.Electrochemical Cells with Microporous Layers (MPLs)

[0039] Figure 4 depicts an example of an electrochemical cell 400 including a microporous layer (MPL). Similar to the example discussed above in Figure 2, the example in Figure 4 depicts a portion of an electrochemical cell 400 having a cathode flow field 402, an anode flow field 404, and a membrane 406 positioned between the cathode flow field 402 and the anode flow field 404.

[0040] As noted above, the membrane 406 may be a catalyst coated membrane (CCM) having a cathode catalyst layer 405 and / or an anode catalyst layer 407 positioned on respective surfaces of the membrane 406.

[0041] A gas diffusion layer (GDL) 408 is positioned between the cathode flow field 402 and membrane 406. As noted above, the GDL 408 is a porous media responsible for the transport of gaseous hydrogen to the cathode side flow field. In certain examples, the GDL 408 may be made of carbon fibers. In certain examples, the thickness of the GDL 408 may be in a range of 100-1000 microns.

[0042] On the opposite side of the cell, a porous transport layer (PTL) 410 may be present in the electrochemical cell between the membrane 406 and the anode 404. In certain examples, the thickness of the PTL 410 may be in a range of 100-1000 microns.Similar to the GDL 408, the PTL 410 is a porous media configured to allow the transportation of the reactant water to the anode catalyst layers, remove produced oxygen gas, and provide good electrical conductivity for effective electron conduction. In other words, liquid water flowing in the anode flow field is configured to permeate through the PTL to reach the CCM. Further, gaseous byproduct oxygen is configured to be removed from the PTL to the flow fields. In such an arrangement, liquid water functions as both reactant and coolant on the anode side of the cell.

[0043] As noted above, the cathode flow field 402 and anode flow field 404 of the cell may individually include a flow field plate composed of metal, carbon, or a composite material having a set of channels machined, stamped, or etched into the plate to allow fluids to flow inward toward the membrane or out of the cell.

[0044] A microporous layer (MPL) 412 is positioned adjacent to the GDL 408 on the cathode side of the electrochemical cell 400. In certain examples, the thickness of the MPL may be in a range of 10-200 microns, 10-100 microns, 10-50 microns, 50-100 microns, 20- 100 microns, or 30-90 microns.

[0045] The MPL 412 includes pores or openings within the layer allowing the transport of fluids (i.e., water and gas) through the layer. The average size of the pores may be on a micrometer or nanometer scale. For example, the average pore size may be less than 50 microns, less than 10 microns, less than 1 micron, less than 100 nm, less than 50 nm, less than 10 nm, less than 5 nm, in a range of 1-1000 nm, in a range of 1-100 nm, in a range of 1- 50 nm, in a range of 1-10 nm, or in a range of 1-5 nm.

[0046] In this particular example, the MPL 412 is positioned between the GDL 408 and the cathode catalyst layer 405 of the membrane 406. Alternatively, (while not depicted) the MPL may be positioned on the opposite surface of the GDL 408, i.e., between the GDL and cathode flow field.

[0047] As noted above, the MPL 412 is advantageous in improving or optimizing the electrical conductivity, thermal conductivity, mechanical compliance, and fluid management within the electrochemical cell on the cathode side of the cell. In certain examples, the MPL may assist in providing a thermal conductivity within a range of 10 W / mK to 1000 W / mK. In additional examples, the MPL having the carbon-based composition may assist in providing an electrical conductivity within a range of 10 S / cm to 1000 S / cm.

[0048] Specifically, the MPL 412 is advantageous in providing a mechanically compliant and protective / cushioning layer that protects against electrical shorts in the electrochemical cell / PEMWE that could be caused by mechanical puncturing of the membrane separating the anode and cathode. In comparison, fuel cells / PEMFCs may utilize carbon fiber cloth GDLs on both the anode and cathode side with both mechanically compliant layers able to distribute the pressure on the CCM. In PEMWEs, as noted above, the PTL on the anode sideof the cell may be composed of a stiff porous sheet of (e.g., Ti) metal that can cause pinching of the membrane if pressure is uneven. Thus, PEMWEs may rely on the cathode GDL to even the pressure distribution. The GDL fibers themselves become a shorting risk in PEMWEs because of the unyielding anode. As such, the addition of the MPL may advantageously provide a protective / cushioning layer to shield the membrane from pressure hot spots from both the PTL and the GDL fibers. This function becomes especially important as the thickness of the membrane is decreased in PEMWEs.

[0049] In certain examples, the composition of the MPL 412 may include a carbon-based compound and a binder. Additional components, such as additional additive or filler compounds, may also be included within the MPL 412 composition.

[0050] The carbon-based compound within the MPL may be advantageous in providing thermal and electrical conductivity through the porous layer. Thermal conductivity is particularly important within the electrochemical cell for higher current density cells / stacks as described herein. Higher current densities increase the joule heating in the membrane. Overheating of the cell may damage the membrane, so the excess heat must be transported away from the active area. The addition of a thermally conductive MPL may be advantageous in improving or facilitating the heat management within the cell. As such, a thermally conductive carbon-based compound is advantageous to include within the MPL.

[0051] In certain examples, the carbon-based composition may be a carbon powder. In certain examples, the carbon powder is a graphitic carbon, which may have higher thermal and / or electrical conductivity properties. In certain examples, the MPL having the carbonbased composition may provide a thermal conductivity within a range of 10 W / mK to 1000 W / mK. In additional examples, the MPL having the carbon-based composition may provide an electrical conductivity within a range of 10 S / cm to 1000 S / cm.

[0052] In some examples, the carbon-based composition may be any type of carbon powder or carbon fiber such as activated carbon, carbon nanofibers (CNFs), or carbon black (e.g., acetylene black, channel black, furnace black, lamp black, or thermal black). Nonlimiting examples of such carbon powders may include Vulcan carbon (e.g., Vulcan XC72 Conductive Carbon Black), graphitized carbon nanofibers (CNFs), Super P® Carbon Black, Super C45 Conductive Carbon Black, or combinations thereof.

[0053] In some examples, the binder within the MPL composition is a polymeric binder. Any polymer with good binding properties may be used. Specifically, polymeric binder compositions with higher affinities for water may be advantageous, as such hydrophilic properties within the binder composition may assist in providing a MPL composition that is more hydrophilic than the adjacent GDL. In some examples, an ionomer within the iontransporting binder within the cathode catalyst layer 405 may be used as a binder within the MPL composition. Additionally, or alternatively, an ionomer used within the membrane 406 configured to facilitate water transport may be used as a binder within the MPL composition. The membrane ionomer may be an anion exchange ionomer that is used in anion exchange membrane water electrolyzer MPLs or a proton exchange ionomer that is used in proton exchange membrane water electrolyzer MPLs.

[0054] As noted above, the binder within the MPL 412 may have hydrophilic properties or may have a higher affinity for water than the GDL. This is advantageous in improving the water transport to / from the membrane, therein assisting in maintaining hydration of the membrane and catalyst layer, contrary to the state of the art within fuel cells / PEMFCs, which are designed to prevent liquid transport and prevent flooding of the catalyst layer.

[0055] In certain examples, the water transport properties (e.g., the hydrophilicity) and / or the additional properties (e.g., electrical conductivity, thermal conductivity, mechanical compliant properties) of the MPL 412 may be optimized by changing the surface properties of the carbon compounds and polymeric binder within the MPL 412. Additionally, or alternatively, the water transport and / or additional properties of the MPL 412 may be adjusted / optimized by changing: (1) an equivalent weight of the binder, (2) a molecular weight of the binder, (3) a binder to carbon (B / C) ratio of the MPL composition.

[0056] Specifically, the binder to carbon ratio within the MPL may be optimized to have enough binder to establish connectivity among the porous layer, but the binder is not electrically conductive so too much binder reduces electrical and thermal conductivity. In other words, increasing the amount of binder (i.e., increasing the B / C ratio) may increase the hydrophilic property of the MPL while decreasing the electrical and / or thermal conductivity of the MPL. As such, an optimized ratio of binder and carbon within the MPLprovides acceptable thermal and conductivity from the carbon and hydrophilic and binding properties from the binder.

[0057] In certain examples, the binder may make up 5-50 wt.% of the composition within the MPL. The remaining components of the MPL may include the carbon-based composition and any additional additives or fillers.

[0058] In one particular example, the binder to carbon ratio within the MPL may be in a range of 10 parts by weight binder:l part by weight carbon to 1 part by weight binder:10 parts by weight carbon, in a range of 5 parts by weight binder:l part by weight carbon to 1 part by weight binder:5 parts by weight carbon, or in a range of 2 parts by weight binder:l part by weight carbon to 1 part by weight binder: parts by weight carbon.Methods of Making Microporous Layer and Electrochemical Cell

[0059] The process of forming the microporous layer may include an ex-situ process, wherein a mixture or solution of a carbon-based compound and one or more additives / binders / fi Ilers is formed. The mixture may be subsequently applied to a surface of an adjacent layer within the electrochemical cell or a substrate through a variety of different methods. The viscosity of the mixture may be adequately tuned to perfect any of these process methods.

[0060] In one example, the mixture having the carbon-based compound and one or more additives / bi nde rs / fi I le rs may be spray coated onto an adjacent layer of the cell (e.g., the GDL or membrane) or a substrate using a spray brush and ultrasonic sprayer.

[0061] In another example, the mixture may be casted with a myer rod, doctor blade, gravure, or casting knife.

[0062] In another example, the mixture may be first sputter coated or added using ALD (atomic layer deposition).

[0063] In another example, the mixture may be formed as a thin film on a temporary substrate such as polytetrafluoroethylene (PTFE) or ethylene tetrafluoroethylene (ETFE), and subsequently, and then subsequently applied or adhered to the adjacent layer within the electrochemical cell.

[0064] One or more embodiments of the disclosure may be referred to herein, individually and / or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, are apparent to those of skill in the art upon reviewing the description.

[0065] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0066] As used herein, "for example," "for instance," "such as," or "including" are meant to introduce examples that further clarify more general subject matter. Unless otherwise expressly indicated, such examples are provided only as an aid for understanding embodiments illustrated in the present disclosure and are not meant to be limiting in any fashion. Nor do these phrases indicate any kind of preference for the disclosed embodiment.

[0067] The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

[0068] It is intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it is understood that the following claims including all equivalents are intended to define the scope of the disclosure. The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed as the disclosure.

Claims

CLAIMS1. A microporous layer (MPL) for an electrochemical cell, the MPL comprising: a carbon-based compound; and a binder, wherein the MPL is configured to be positioned between a gas diffusion layer (GDL) and a membrane within the electrochemical cell, and wherein a composition of the MPL has a porous structure configured to transport fluids through the MPL to the GDL or the membrane.

2. The MPL of claim 1, wherein the composition of the MPL has a greater affinity for water than a composition of the GDL therein allowing for a greater transport of the water through a combination of the MPL and the GDL in comparison to the GDL alone.

3. The MPL of claim 2, wherein the binder is a polymeric binder that has the greater affinity for water than the composition of the GDL, and wherein the polymeric binder is configured to provide improved fluid flow to and from the membrane in comparison to an electrochemical cell without the MPL.

4. The MPL of claim 1, wherein a thickness of the MPL is in a range of 10-100 microns.

5. The MPL of claim 1, wherein the porous structure comprises pores having an average pore size in a range of 1-1000 nm.

6. The MPL of claim 1, wherein the MPL is configured to provides a protective layer between the GDL and the membrane, therein protecting the membrane from puncture by the GDL and preventing or reducing a risk of electrical shorting within the electrochemical cell.

7. The MPL of claim 1, wherein the carbon-based compound comprises a carbon powder or a carbon nanofiber.

8. The MPL of claim 7, wherein the carbon powder comprises activated carbon, carbon black, or combinations thereof.

9. The MPL of claim 7, wherein the carbon powder is a Vulcan carbon, graphitized carbon nanofibers, Super P® Carbon Black, Super C45 Conductive Carbon Black, or combinations thereof.

10. The MPL of claim 1, wherein the carbon-based compound within the MPL is electrically conductive and thermally conductive and configured to transport heat away from the membrane during operation of the electrochemical cell.

11. The MPL of any of claims 1-10, wherein a ratio of the binder to the carbon-based compound is in a range of 10 parts by weight binder:l part by weight carbon to 1 part by weight binder:10 parts by weight carbon.

12. An electrochemical cell comprising: a proton exchange membrane (PEM); a gas diffusion layer (GDL); and a microporous layer (MPL) positioned between the PEM and the GDL, and wherein a composition of the MPL has a porous structure configured to transport fluids through the MPL to the GDL or the PEM.

13. The electrochemical cell of claim 12, wherein the composition of the MPL has a greater affinity for water than a composition of the GDL therein allowing for a greater transport of the water through a combination of the MPL and the GDL in comparison to the GDL alone.

14. The electrochemical cell of claim 12, wherein a thickness of the MPL is in a range of 10-100 microns.

15. The electrochemical cell of claim 12, wherein the porous structure comprises pores having an average pore size in a range of 1-1000 nm.

16. The electrochemical cell of claim 12, wherein the MPL is configured to provides a protective layer between the GDL and the PEM, therein protecting the PEM from puncture by the GDL and preventing or reducing a risk of electrical shorting within the electrochemical cell.

17. The electrochemical cell of claim 12, wherein the MPL comprises a carbon-based compound and a binder.

18. The electrochemical cell of claim 17, wherein the carbon-based compound comprises a carbon powder or a carbon nanofiber.

19. The electrochemical cell of claim 18, wherein the carbon powder is a Vulcan carbon, graphitized carbon nanofibers, Super P® Carbon Black, Super C45 Conductive Carbon Black, or combinations thereof.

20. The electrochemical cell of claim 17, wherein the carbon-based compound within the MPL is electrically conductive and thermally conductive and configured to transport heat away from the PEM during operation of the electrochemical cell.

21. The electrochemical cell of claim 17, wherein the binder is a polymeric binder that has a greater affinity for water than the composition of the GDL, and wherein the polymeric binder is configured to provide improved fluid flow to and from the PEM in comparison to an electrochemical cell without the MPL.

22. The electrochemical cell of claim 17, wherein a ratio of the binder to the carbonbased compound is in a range of 10 parts by weight binder:l part by weight carbon to 1 part by weight binder:10 parts by weight carbon.

23. The electrochemical cell of any of claims 12-22, wherein the electrochemical cell is configured to operate with 200 mV or less of pure resistive loss when operating at a current density in a range of 3-30 Amps / cm2.

24. The electrochemical cell of any of claims 12-22, wherein the electrochemical cell is configured to transfer 0.25-5 mL of water through the electrochemical cell per Amp per min.

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