Patent Application
20230207850
The present technology relates to reinforcement of proton-exchange membranes, including proton-exchange membranes used in membrane electrode assemblies and fuel cells including such membrane electrode assemblies.
This section provides background information related to the present disclosure which is not necessarily prior art.
Fuel cell systems can be used as power supplies in numerous applications, such as vehicles and stationary power plants. Such systems can deliver power economically and with environmental and other benefits. To be commercially viable, however, fuel cell systems should exhibit adequate reliability in operation, even when the fuel cell systems are subjected to conditions outside their preferred operating ranges.
Fuel cells convert reactants, namely, fuel and oxidant, to generate electric power and reaction products. Proton-exchange membrane fuel cells (PEM fuel cells), also referred to as polymer-electrolyte membrane fuel cells, can employ a membrane electrode assembly (MEA) comprised of a proton exchange membrane (e.g., proton conducting ionomer) disposed between two electrodes, namely a cathode and an anode. A catalyst typically facilitates the desired electrochemical reactions at the electrodes. Separator plates or bipolar plates, including plates providing a flow field for directing the reactants across a surface of each electrode, and/or various types of gas-diffusion media, can be disposed on each side of the MEA.
In operation, the output voltage of an individual fuel cell under load can be below one volt. Therefore, in order to provide greater output voltage, multiple fuel cells can be stacked together and can be connected in series to create a higher voltage fuel cell stack. End plate assemblies can be placed at each end of the fuel cell stack to hold the stack together and to compress the stack components. Compressive force can provide sealing and adequate electrical contact between various stack components. Fuel cell stacks can be further connected in series and/or parallel combinations with other fuel cell stacks or power sources to form larger arrays for delivering higher voltages and/or currents.
Proton-exchange membranes used in fuel cells can experience wide ranges of operating conditions, including changes with respect to relative humidity as well as temperature, where a proton-exchange membrane can be reinforced both chemically and mechanically to increase the durability of proton-exchange membrane. For example, expanded polytetrafluoroethylene (e-PTFE) can be used for membrane mechanical reinforcement, while one or more antioxidants can be included in the membrane to improve chemical stability against certain radicals, such as those generated by Fenton's reaction (e.g., hydroxyl radicals).
Accordingly, there is a continuing need for optimizing mechanical and chemical stability of a proton-exchange membrane to obtain desired performance and durability requirements for PEM fuel cells.
In concordance with the instant disclosure, optimized proton-exchange membranes, including membrane electrode assemblies and fuel cells including such proton-exchange membranes, and methods of making such proton-exchange membranes have been surprisingly discovered.
The present technology includes articles of manufacture, systems, and processes that relate to a proton-exchange membrane including a first layer, a second layer, and a third layer. The first layer includes a first ionomer and has first side and a second side. The second layer including a graphene oxide and has a first side and a second side, where the first side of the second layer is adjacent the second side of the first layer. The third layer includes a second ionomer and has a first side and a second side, where the first side of the third layer is adjacent the second side of the second layer.
Ways of making a proton-exchange membrane are provided that include disposing a first layer on a support layer, where the first layer includes a first ionomer. A second layer is disposed on the first layer, where the second layer includes graphene oxide. A third layer is disposed on the second layer, where the third layer includes a second ionomer. The support layer can be removed thereafter.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
DRAWINGS
The drawing described herein is for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
The following description of technology is merely exemplary in nature of the subject matter, manufacture and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as may be filed claiming priority to this application, or patents issuing therefrom. Regarding methods disclosed, the order of the steps presented is exemplary in nature, and thus, the order of the steps can be different in various embodiments, including where certain steps can be simultaneously performed, unless expressly stated otherwise. “A” and “an” as used herein indicate “at least one” of the item is present; a plurality of such items may be present, when possible. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word “about” and all geometric and spatial descriptors are to be understood as modified by the word “substantially” in describing the broadest scope of the technology. “About” when applied to numerical values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” and/or “substantially” is not otherwise understood in the art with this ordinary meaning, then “about” and/or “substantially” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters.
Although the open-ended term “comprising,” as a synonym of non-restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments may alternatively be described using more limiting terms such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting materials, components, or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components, or process steps excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a composition or process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that may be recited in the art, even though element D is not explicitly described as being excluded herein.
As referred to herein, disclosures of ranges are, unless specified otherwise, inclusive of endpoints and include all distinct values and further divided ranges within the entire range. Thus, for example, a range of “from A to B” or “from about A to about B” is inclusive of A and of B. Disclosure of values and ranges of values for specific parameters (such as amounts, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein. It is envisioned that two or more specific exemplified values for a given parameter may define endpoints for a range of values that may be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, 3-9, and so on.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The present technology is drawn to optimized proton-exchange membranes that provide enhanced mechanical and chemical stability in operating environments encountered within PEM fuel cells. In this way, the proton-exchange membrane can be used to obtain desired performance and durability requirements for PEM fuel cells. Proton-exchange membranes provided herein can include a first layer, a second layer, and a third layer. The first layer can include a first ionomer and can have a first side and a second side. The second layer can include a graphene oxide and can have a first side and a second side, where the first side of the second layer can be adjacent the second side of the first layer. The third layer can include a second ionomer and can have a first side and a second side, where the first side of the third layer can be adjacent the second side of the second layer. In certain embodiments, the first side of the second layer can be directly adjacent the second side of the first layer, and the first side of the third layer can be directly adjacent the second side of the second layer. The proton-exchange membrane can also include a support layer adjacent the first side of the first layer, where the support layer can also be directly adjacent the first side of the first layer. Accordingly, the second layer can be sandwiched between the first layer and the second layer. The construction of the proton-exchange membrane provides increased mechanical stability, including improved stability in response to humidity and temperature changes, as well as increased chemical stability. Such proton-exchange membranes constructed in accordance with the present disclosure can also provide increased stability with respect to antioxidant effect provided thereby and can minimize migration of antioxidant out of the membrane.
The support layer, for example configured as a blank or a web, can be used in forming the proton-exchange membrane. For example, the support layer can provide a stable platform upon which successive layers can be disposed, applied, or formed in various ways to produce the proton-exchange membrane. The support layer can include a fluoropolymer layer that can facilitate later removal from the formed proton-exchange membrane. Certain methods of making a proton-exchange membrane include providing support layer as a blank or web, where the support layer can include a fluoropolymer layer. A first layer including the first ionomer can be disposed on or applied to the support layer. A second layer including the graphene oxide can be disposed on or applied to the first layer. A third layer including a second ionomer can be disposed on or applied to the second layer. The support layer can be removed to leave a proton-exchange membrane including the second layer sandwiched by the first layer and the second layer.
The support layer can include the following aspects. The support layer can be configured as a blank of predetermined size or a continuous web of material. The support layer can include a fluoropolymer layer. The fluoropolymer layer can include one or more various fluoropolymers, such as polytetrafluoroethylene (PTFE), polyethylenetetrafluoroethylene (ETFE), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA), fluorinated ethylene-propylene (FEP), polyehtylenechlorotrifluoroethylene (ECTFE), perfluorinated elastomer (FFPM), perfluoropolyether (PFPE), and perfluorosulfonic acid (PFSA). Embodiments include where the support layer consists solely of the fluoropolymer layer and where the support layer can also include other polymers, elastomers, and combinations of materials, for example, where the fluoropolymer layer can be applied as a release layer on other materials or layer(s) of materials. The release layer can be applied by spray coating or dip coating, among other means. Where the support layer includes a fluoropolymer layer, the fluoropolymer layer can have a thickness of about 0.1 mil (2.54 microns) to about 5 mil (127 microns).
Each layer including ionomer (e.g., the first layer and the second layer) can include the following aspects. Embodiments include where the ionomer in each layer is the same and other embodiments include where the ionomer in different layers is different. The ionomer can include a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer; e.g., Nafion™ fluoropolymer-copolymer by DuPont. The ionomer, in the first layer and/or the third layer, for example, can have an ionomer equivalent weight (EW) of about 700 g/mol to about 1,100 g/mol. The first layer and/or the third layer can have a thickness of about 2.54 microns to about 127 microns. It is also possible to have the first layer and the third layer be substantially the same.
The second layer including the graphene oxide can include the following aspects. The graphene oxide can include a functionalized graphene oxide having various ionized units, such as sulfonic acid units. For example, graphene oxide can be functionalized in various ways to include various functional groups. Certain embodiments include where the graphene oxide can be functionalized by using 3-mercaptopropyl trimethoxysilane (MPTMS) as a sulfonic acid functional group precursor.
The second layer including the graphene oxide can also include an antioxidant. Certain embodiments include cerium oxide as the antioxidant, where the cerium oxide can be present at about 0.01 mg/2 to about 0.3 mg/cm2. It is also possible to have the second layer include a functionalized graphene oxide and the antioxidant (e.g., cerium oxide). Furthermore, the second layer can include a functionalized graphene oxide, antioxidant (e.g., cerium oxide), and an ionomer such as a proton form ionomer and/or a sodium form ionomer. The second layer can have a thickness of about 2.5 microns to about 5 microns.
Graphene oxide possesses excellent physical, chemical, and mechanical properties that can surprisingly enhance the proton-exchange membranes provided herein. Graphene oxide can be readily processed and coated as one or more thin films, where graphene oxide by itself can also act as a good antioxidant. The graphene oxide layer can allow protons to pass therethrough but can prevent gasses from passing therethrough, resulting in special characteristics for its use as a reinforcement layer in the present proton-exchange membranes. Graphene oxide can also be processed in an aqueous/alcoholic medium with different concentrations and can be coated as a sandwiched layer relative to the other component layers; e.g., the second layer including the graphene oxide can be sandwiched by the first layer and the third layer in construction of the proton-exchange membrane. The graphene oxide can provide reinforcement to the overall proton-exchange membrane structure.
The proton-exchange membrane can be used in various ways. A membrane electrode assembly can include one or more proton-exchange membranes as provided herein in conjunction with one or more electrodes. For example, the proton-exchange membrane can be disposed between two electrodes; e.g., a cathode and an anode. Such membrane electrode assemblies can be used in one or more fuel cells, including various fuel cell stacks. Individual fuel cells or stacks including such fuel cells having one or more proton-exchange membranes as provided herein can be used as power plants in various applications, including providing an electrical power source for a vehicle.
Various ways of making proton-exchange membranes are provided by the present technology. For example, one or more of the various component layers can be disposed on another by various means, including where successive layers are laminated, applied by one or more rollers, calendared, sprayed, or deposited onto one another to form complete layered proton-exchange membranes or partial proton-exchange membranes that are then further combined or laminated to form complete membranes. Webs of certain component layers can have other component layers applied thereto and/or transferred therefrom. Likewise, discrete blanks having predetermined dimensions of certain component layers can have other component layers applied thereto.
Certain methods of making a proton-exchange membrane can include the provision of a support layer, such as a blank or web including a fluoropolymer layer. A first layer including ionomer can be disposed on the fluoropolymer layer. A second layer including graphene oxide can be disposed on the first layer. A third layer including ionomer can be disposed on the second layer. The support layer can be removed leaving a proton-exchange membrane including the second layer sandwiched by the first layer and the second layer. Disposing various layers onto one another includes various means of application, lamination, calendaring, spraying, deposition, and other film-forming techniques, as applicable.
The present technology can accordingly extend the durability of proton-exchange membrane applications and can provide economic advantages. In some embodiments, the proton-exchange membrane can simultaneously provide increased mechanical durability and chemical durability. In other proton-exchange membranes, it has been observed that an amount of an antioxidant (e.g., CeO2) can leach out of the proton-exchange membrane and effect fuel cell performance in a negative way. However, the proton-exchange membranes provided by the present technology can stabilize added antioxidant and minimize migration thereof out of the membrane.
Example embodiments of the present technology are provided with reference to the several figures enclosed herewith.
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Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Equivalent changes, modifications and variations of some embodiments, materials, compositions, and methods can be made within the scope of the present technology, with substantially similar results.
This application claims the benefit of U.S. Provisional Application No. 63/293,459, filed on Dec. 23, 2021. The entire disclosure of the above application is hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63293459 | Dec 2021 | US |
