Composite polymer electrolyte ceramic membrane

Abstract

The present disclosure relates to a two-layer polymer electrolyte membrane including a first layer and a second layer, where the first layer contains perfluorosulfonic acid, the second layer contains a metal oxide, and the first layer is disposed on the second layer. The present disclosure further relates to a method of manufacturing the two-layer polymer electrolyte membrane, as well as a membrane electrode assembly and a fuel cell including the two-layer polymer electrolyte membrane.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 348,715, filed Jun. 3, 2022, and U.S. Provisional Application No. 63 / 433,573, filed Dec. 12, 2022. The entire teachings of each of the above applications are incorporated herein by reference.

[0002] Government Support This invention was made with government support under grant number DE-SC0021832 awarded by the Department of Energy and grant number DE-AR0001242 awarded by ARPA-E. The government has certain rights in this invention.

Background Art

[0003] Background of the Invention Proton exchange membrane fuel cells (PEMFCs) are environmentally friendly energy conversion devices that operate at low temperatures and are more efficient than existing internal combustion engines. With these advantages, PEMFCs have emerged as a common alternative to fossil fuels in the transportation industry and have the potential for use in a wide range of applications such as portable devices and stationary power supply systems.

[0004] A proton exchange membrane (PEM) that conducts protons and serves to separate the cathode and anode is one of the most important components of a PEMFC. The PEM significantly affects the overall performance of the fuel cell; thus, improving the efficiency of the fuel cell requires a PEM that has high ionic conductivity, low fuel crossover, and provides high physicochemical and mechanical stability. Since PEMFCs use thin membranes as their electrolytes, these devices are more portable and compact than other types of fuel cells. However, thin membranes can also allow crossover of fuel gas (hydrogen), which negatively affects battery efficiency. Additionally, PEM materials form OH · and OOH ·It is liable to deteriorate due to the presence of free radicals such as. Therefore, a PEM having high ionic conductivity, reduced hydrogen crossover and stability with respect to radical oxidants is required. Summary of the Invention

[0005] Summary of the Invention In a first aspect, the present invention is a two-layer polymer electrolyte membrane comprising a first layer disposed on a second layer, the first layer comprising a perfluorosulfonic acid (PFSA) polymer, and the second layer comprising a crystalline metal oxide.

[0006] In a second aspect, the present invention provides a method for producing a two-layer polymer electrolyte membrane as described herein with respect to the first aspect and its various aspects, the method comprising the steps of: providing a first layer having a first surface and a suspension comprising a metal oxide and a solvent; and coating the suspension on the first surface of the first layer to thereby produce a coated first layer.

[0007] In a third aspect, the present invention is a membrane electrode assembly (MEA) comprising a two-layer polymer electrolyte membrane as described herein with respect to the first aspect and its various aspects; a cathode; and an anode, the two-layer electrolyte membrane being disposed between the anode and the cathode.

[0008] In a fourth aspect, the present invention is a fuel cell comprising one or more MEAs as described herein with respect to the third aspect and its various aspects and one or more gas flow bipolar plates. Brief Description of the Drawings

[0009] Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0010] The foregoing will be apparent from the following more particular description of the exemplary embodiments of the invention as illustrated in the accompanying drawings, in which like reference numerals refer to the same parts throughout the different figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the embodiments of the invention.

[0011] Detailed Description of the Invention The following is an explanation of the exemplary embodiments of the present invention.

[0012] Hydrogen crossover is the undesirable diffusion of hydrogen from the anode to the cathode through the membrane in a fuel cell. Hydrogen crossover can have at least three effects such as reduced fuel efficiency, reduced cathode potential, and the formation of aggressive peroxide radicals. The crossover hydrogen can react directly with oxygen at the cathode surface, resulting in a cathode potential lower than that of a lower fuel cell. More seriously, this direct reaction between H2 and O2 at the cathode can not only attack the catalyst layer but also the membrane, generating peroxide radicals that cause significant degradation of the catalyst layer and the membrane. Also, the formation of hot points or hydrogen peroxide due to the highly exothermic chemical reaction between H2 and O2 can cause pinholes in the membrane, break the MEA, and has been confirmed to cause safety problems. Accelerated sintering of the catalyst can also be caused by this hydrogen crossover. The presence of accompanying Cu and Fe further catalyzes the decomposition of H2O2 into reactive oxygen radicals. To address this root cause, the membrane can be made more durable by reducing the hydrogen permeability through the membrane. Ceramic additives can reduce the gas permeability in the polymer composite according to the Maxwell permeability model. For the SiO2-polyethylene oxide (PEO) system with a 35 vol% ceramic content, the H2 permeability is 8 barrer, and compared with that of hydrated Nafion (120 barrer), the polysulfone-PEO random copolymer has an H2 permeability of 2 barrer.

[0013] Lifetime is always one of the key concerns at the core of proton exchange membrane fuel cells, especially in commercial applications. Membrane degradation caused by chemical decomposition can lead to failure of the entire fuel cell system. Proton exchange membranes with enhanced chemical durability can be produced by the addition of free radical scavengers. Free radical scavengers are a series of compounds that can react preferentially with harmful radicals over ionomers, protecting the membrane. In some embodiments, the present disclosure shows that crystalline metal oxides of reducible metals can act as proton conductors and as radical scavengers while reducing hydrogen crossover (see Figure 9 for the mechanism of radical scavenging by cerium oxide). The free radical scavenging ability depends on the concentration of the scavenging species. Using cerium as an exemplary example, the free radical scavenger can be added either as a cerium salt, as crystalline cerium oxide nanoparticles, or as amorphous cerium oxide particles. Particles are used for the salts to limit the mobility of cerium in the fuel cell in a hydrated environment. Crystalline surface materials can have a higher concentration of active Ce 3+ species because of defect compensation by oxygen vacancies in the system and strain from the crystal lattice, so crystalline nanoparticles are used over amorphous particles. The concentration of active species in the case of metal oxides rather than free cations can be improved by reducing the nanoparticle size or introducing strain into the lattice.

[0014] Without wishing to be bound by any particular theory, since both sides of the crystalline metal oxide are usually covered by organic ligands after synthesis, the interaction between the metal oxide and the polymer is thought to be limited to weak van der Waals interactions. To introduce strong interactions similar to hydrogen bonds, covalent bonds and ionic interactions, metal oxides with exposed surfaces and active M-O, M-H and M-OH groups are preferred. On the polymer side, chains with chelating properties such as amines, carboxylates, phosphates and hydroxyls (for hydrogen bonding) are preferred. By introducing stronger interactions, a higher loading of the crystalline metal oxide can be achieved without suffering from macrophase separation of the particles into the free surface, which is advantageous for properties proportional to the volume fraction such as conductivity and gas permeability.

[0015] Composites of crystalline metal oxide nanoparticles can exhibit both lower and higher gas permeabilities, depending on the pairing of the nanoparticles and the polymer. Previous work on nanoparticles with weak interactions with the host polymer has shown that although the nanoparticle constituents are impermeable, the composite can exhibit significantly higher gas permeability in the system because the weak interactions cause an increase in the free volume of the polymer. That is, the weak interactions result in an intermediate plane of gas permeability that is hindered between the nanoparticles and the polymer, which can act as a pathway for fast gas transport in the system. It has previously been shown that metal oxide / polymer composites do not exhibit ionic conduction properties without the intentional introduction of salts (usually alkali and alkaline earth salts). This understanding is extrapolated to the case of proton conduction systems, where metal oxides are usually added to the polymer in the presence of an acid or base (either as an independent salt such as phosphoric acid or fixed to the polymer backbone in the case of a polymeric acid). The present disclosure unexpectedly shows that metal oxide / polymer composites can exhibit significant ionic conductivity in the absence of salts at high humidity, which may be due to the intrinsic concentration of protons and hydroxide groups on the metal oxide surface.

[0016] In some embodiments, the present disclosure relates to a two-layer polymer electrolyte membrane that exhibits reduced hydrogen crossover and improved membrane durability. The membrane includes a layer of perfluorosulfonic acid (PFSA), such as Nafion®, and a coating that includes a metal oxide. In some embodiments, the coating layer includes a metal oxide, such as cerium oxide, dispersed in a polymer matrix. The coating layer has lower hydrogen permeability compared to PFSA and reduces the level of peroxide radicals, thus reducing hydrogen crossover through the membrane and improving membrane durability (Figures 1 and 2).

[0017] The plot in Figure 3 shows the design criteria for the coated membrane. The plot shows the theoretical calculations of H2 crossover and the resistance of the coated PFSA as a function of the coating thickness. The cyclic voltammogram in Figure 4 shows the hydrogen crossover measurements of Nafion® 211 coated with a 700 nm layer containing cerium oxide nanocrystals dispersed in Nafion® 211 and 75% crosslinked PEG(DA). The plot in Figure 5 shows the fuel cell polarization and power curves of Nafion® 211 coated with a layer consisting of cerium oxide nanocrystals dispersed in a Nafion® 211 and 75% crosslinked PEG(DA) coating. These data show that the coating reduces H2 crossover by 25% compared to uncoated Nafion® 211. Further, the results of the fast accelerated stress test (FAST) in Figure 6 show that the presence of cerium oxide nanocrystals in the crosslinked PEG(DA) coating doubles the durability of the membrane at least. The membrane failure time for Nafion® 211 is about 5000 equivalent hours, and for Nafion® 211 with 1 μm cerium oxide nanocrystals in the crosslinked PEG(DA) coating, the failure time was not reached during the standard duration of the test and lasted for 10,000 equivalent hours. The plot in Figure 8 shows that the cerium oxide nanocrystals in the crosslinked PEG(DA) coating on Nafion® 211 regulate H2 crossover over a range of coating thicknesses. The plot shows that the hydrogen crossover is adjustable by changing the coating thickness and that a reduction of over 50% in hydrogen crossover was achieved using various thicknesses of cerium oxide nanocrystals in the crosslinked PEG(DA) coating on Nafion® 211.

[0018] The plot of FIG. 14 shows the fuel cell polarization and power curves of a membrane comprising a layer of Nafion® 211 coated with a composite layer containing nanocrystalline ZrO2, MnO2, TiO2, Nb2O3 and cross-linked PEG(DA). The data shows that various reducible metal oxide nanocrystals can be used in the bilayer composite membrane.

[0019] The plot of FIG. 15 shows the fuel cell polarization and power curves of a membrane comprising a layer of Nafion® 211 coated with a composite layer containing CeO2 and polyethyleneimine cross-linked with dibromopropane or polyphenylsulfone (PPS) cross-linked with DMSO. The data shows that various cross-linked polymers can be used in the bilayer composite membrane.

[0020] Definitions Numerical ranges include the numbers defining the ranges. For example, "x is an integer from 5 to 14" means that x can be 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14. Measured and measurable values are understood to be approximate, taking into account significant figures and errors associated with the measurement. As used in this application, the terms "about" and "approximately" have the meanings understood in their respective technical fields; the use of one with respect to the other does not necessarily imply different ranges. Unless otherwise indicated, numerical values used in this application are to be understood to include normal deviations and / or variations as would be understood by a person skilled in the relevant art, with or without modifiers such as "about" or "approximately". In one embodiment, the terms "about" or "approximately" refer to a range of values corresponding to 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater or less) of the recited reference value, unless otherwise stated or unless it is clear from the context that this is not the case (except when such a number exceeds 100% of the possible values).

[0021] As used herein, the term "two-layer polymer electrolyte membrane" refers to a membrane comprising two layers disposed on top of each other, each layer containing a polymer electrolyte. The two layers can adhere to each other via the formation of chemical bonds or via van der Waals interactions.

[0022] As used herein, "characteristic dimension" refers to the dimension of a crystal that can be measured, for example, by known methods used in the art, such as microscopy. For a spherical crystal, the characteristic dimension is the diameter of the crystal. For non-spherical crystal morphologies, the characteristic dimension of a single crystal can be any dimension selected from the length, width, and height of the crystal, each of randomly assigned X, Y, and Z, for example, the following options (X = Y = Z), (X ≠ Y ≠ Z), (X = Y, X ≠ Z), (X = Z, X ≠ Y), (X ≠ Z, Y = Z)).

[0023] The terms "crystal", "crystals" or "crystalline" refer to a substance in which its constituent atoms, molecules or ions are arranged substantially uniformly and repeat a three-dimensional pattern. The pattern can be detected according to known methods used in the field of chemistry, such as visual identification of crystals and identification by X-ray diffraction (e.g., powder X-ray diffraction (PXRD) and single crystal X-ray diffraction (SXRD)).

[0024] As used herein, the term "metal oxide" refers to a compound containing one or more metal cations and oxide anions. Examples of metal oxides include, but are not limited to, titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, cerium oxide, gadolinium oxide and samarium oxide, and oxides of other d and f elements. As used herein, the term "metal oxide" does not include polyoxometalates. "Polyoxometalate" refers to a material containing polyatomic ions, usually anions, consisting of three or more transition metal oxyanions that are linked together by shared oxygen atoms to form a closed three-dimensional framework. The metal atoms in polyoxometalates are usually group 6 (Mo, W) or group 5 (V, Nb, Ta) transition metals in their high oxidation states.

[0025] As used herein, "reducible metal oxide" refers to an oxide of a metal that can have several different valence (or oxidation) states (e.g., two or more of +1, +2, +3, +4, +5, etc.) in bulk form or as a defect state on the surface of the metal oxide. For example, both Ce and Ti can have oxidation states +3 and +4, so cerium oxide and titanium oxide are reducible oxides.

[0026] As used herein, the term "dopant" refers to a factor introduced into a chemical material in small amounts, e.g., a metal oxide that modifies its optical, electronic, photocatalytic and other properties. When a crystalline substance is doped, the atoms of the dopant are incorporated into the crystal lattice of the substance. Examples of dopants include, but are not limited to, elements such as Gd, Sm, Nb, Ce and Si.

[0027] As used herein, the term "degree of sulfonation" refers to the number of repeating units having at least one sulfonic acid / sulfonate group. For example, a degree of sulfonation of 20% indicates a polymer having 20% of its repeating units sulfonated, and a degree of sulfonation of 100% indicates that all of the repeating units in the polymer contain one sulfonic acid / sulfonate group. This can include polymers containing multiple sulfonic acid / sulfonate groups (e.g., disulfonated, trisulfonated, tetrasulfonated, etc.) per repeating unit. In some embodiments, the sulfonated polymer can contain an average of 2 sulfonic acid groups per repeating unit, which corresponds to a degree of sulfonation of 200%. In some embodiments, the sulfonated polymer can contain an average of 2, 3, 4, or 5 sulfonic acid groups per repeating unit, which corresponds to degrees of sulfonation of 200%, 300%, 400%, or 500% respectively. In some embodiments, the sulfonated polymer can contain an average of 1.5 - 2.5 sulfonic acid groups per repeating unit, which corresponds to a degree of sulfonation of 150% - 200%.

[0028] The sulfonated polymers of the present disclosure can also be characterized by the average number of sulfonic acid groups per repeating unit. For example, sulfonated polyphenylsulfone (sPPS) can contain 1, 2, 3, 4, 5, 6, 7, or 8 sulfonic acid groups per repeating unit. For example, the repeating unit of sPPS can contain two sulfonic acid groups:

Chemical formula

Chemical formula

[0029] In a given polymer, some repeating units can have, for example, 1 sulfonic acid group, some repeating units can have 2 sulfonic acid groups, and some repeating units can have 3 or more sulfonic acid groups. Thus, for example, its 1The number of sulfonic acid groups per repeating unit measured in the bulk polymer by analyzing the 1H NMR spectrum or the ion exchange capacity corresponds to the average number of sulfone groups in all repeating units of the polymer.

[0030] As used herein, the term "polyphenyl sulfone" refers to a polymer containing the following repeating units:

Chemical formula

[0031] As used herein, the term "polyether ether ketone" refers to a polymer containing the following repeating units:

Chemical formula

[0032] As used herein, the term "polyphosphazine" refers to a polymer containing the following repeating units:

Chemical formula

[0033] As used herein, the term "polybenzimidazole" refers to a polymer containing the following repeating units:

Chemical formula

[0034] As used herein, the term "polyether sulfone" refers to a polymer containing the following repeating units:

Chemical formula

[0035] As used herein, the term "polyphenylene oxide" refers to a polymer containing the following repeating units:

Chemical formula

[0036] As used herein, the term "polyarylene ether ketone" refers to a polymer containing the following repeating units:

Chem.

[0037] As used herein, the term "poly(sulfone)" refers to a polymer containing the following repeating units:

Chem.

[0038] As used herein, the term "poly(sulfide sulfone)" refers to the following repeating units:

Chem.

[0039] As used herein, the term "polyimide" refers to a polymer containing the following repeating units:

Chem.

[0040] As used herein, the term "poly(ether imide)" refers to a polymer containing the following repeating units:

Chem.

[0041] As used herein, the term "polysiloxane" refers to a polymer containing the following repeating units:

Chem.

[0042] As used herein, the term "polyacrylate" refers to a polymer containing the following repeating units:

Chem.

[0043] As used herein, the term "poly(ethylene glycol)" refers to a polymer containing the following repeating units:

Chem.

[0044] As used herein, the term "poly(ethylene glycol) diacrylate" (PEG(DA)) refers to a polymer represented by the following structural formula:

Chem.

[0045] As used herein, the term "polyvinylidene fluoride" refers to a polymer containing the following repeating units:

Chem.

[0046] As used herein, the term "polytetrahydrofuran" refers to a polymer containing the following repeating units:

Chem.

[0047] As used herein, the term "polyvinyl butyral" refers to a polymer containing the following repeating units:

Chem.

[0048] As used herein, the term "poly(acrylonitrile-butadiene-styrene)" refers to a polymer containing the following repeating units:​​​​​​ [Chem.] refers to a polymer containing

[0049] As used herein, the term "polyether pyridine" refers to the following repeating units: [Chem.] refers to a polymer containing

[0050] As used herein, the term "poly(ethylene imine)" refers to the following repeating units: [Chem.] refers to a polymer containing

[0051] Any of the above polymer repeating units may be -CN, -NO2, -N3, -OH, F, Cl, Br, I, oxo, -SO2H, -SO3H, -OR aa , -NH(R aa )2, -N(R aa )2, -N(R aa )3 + X - , -SH, -SR aa , -C(=O)R aa , -CO2H, -CHO, -CO2R aa , -OC(=O)R aa , -OCO2R aa , -C(=O)N(R aa )2, -OC(=O)N(R aa )2, -NR aa C(=O)R aa , -NR aa CO2R aa , -NR aa C(=O)N(R aa )2, -C(=NR aa )R aa , -C(=O)NR aa SO2R aa , -NR aa SO2R aa , -SO2N(R aa )2, -SO2Raa 、 -SO2OR aa 、 -OSO2R aa 、 -S(=O)R aa 、 -OS(=O)R aa 、 -Si(R aa )3、 -OSi(R aa )3、 C 1-12 alkyl, C 1-12 alkoxyl, C 1-12 haloalkyl, C 3-12 cycloalkyl, 3- to 16-membered heterocyclyl, and C 6-12 may have one or more hydrogen atoms substituted with aryl, where X - is a counterion, and each example of R aa is independently selected from H, -OH, C 1-10 alkyl, C 1-10 haloalkyl, C 3-12 cycloalkyl, 5- to 16-membered heterocyclyl and C 6-12 aryl, or two R aa groups are linked to form a 3- to 16-membered heterocyclyl.

[0052] As used herein, the term "polyol" refers to an alcohol containing more than one hydroxyl group. Examples of polyols include, but are not limited to, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, glycerol, erythritol, xylitol, hydroquinone, catechol, resorcinol, and phloroglucinol.

[0053] As used herein, the term "polyelectrolyte" refers to a polymer containing repeating units having charged or ionizable groups. Under certain sets of conditions, a polyelectrolyte has a net negative or net positive charge. In some embodiments, the polyelectrolyte is a polycation or includes a polycation; in some embodiments, the polyelectrolyte is a polyanion or includes a polyanion. A polycation has a net positive charge and a polyanion has a net negative charge. The net charge of a given polyelectrolyte can depend on the surrounding chemical conditions, such as pH.

[0054] As used herein, the term "perfluorosulfonic acid" refers to the following structural formula: [Chemical formula] represents a polymer, wherein R f represents a perfluoroalkylene or perfluorooxyalkylene group, and x and y are the respective relative proportions of the perfluoromonomer and the sulfonated monomer. As used herein, the term "perfluoroalkylene" or "perfluorooxyalkylene" refers to an alkylene or oxyalkylene group in which all hydrogen atoms are replaced by fluorine. The class of PFSAs is represented by the structural formula (I): [Chemical formula] Such PFSAs are typically classified according to the length of their side chains. For example, Aquivion® (formerly Dow SSC) PFSAs are generally classified as short side chain (SSC) PFSAs, and Nafion® is considered a long side chain (LSC) PFSA. Examples of commercial PFSAs include the following: [Table 1]

[0055] As used herein, the term "crosslinking" refers to the formation of a covalent or ionic bond between a functional group attached to a polymer backbone and another functional group attached to the same or a different backbone, or between a functional group attached to a polymer backbone and a crosslinking reagent.

[0056] As used herein, the term "crosslinked polymer" refers to a polymer in which two or more non-adjacent repeating units of the same or different backbones are linked through a crosslinking moiety. The term "crosslinked polymer" also refers to two or more different backbones linked through a plurality of crosslinking moieties.

[0057] As used herein, the term "crosslinking moiety" refers to a polyvalent, e.g., divalent or trivalent, moiety that forms a covalent bond with one or more non-adjacent repeating units of the same polymer backbone or with one or more repeating units of a different backbone. The crosslinking moiety may include a charged group, such as an ammonium group, a metal ion, a carboxylate group, or a sulfate group. In some embodiments, the crosslinking moiety has the following structural formula: C 2-6 alkylene,

Chemical formula

[0058] As used herein, the term "crosslinking reaction" refers to a chemical reaction between a functional group attached to the repeating unit of a polymer and a crosslinking reagent that results in a covalent or electrostatic / ionic bond between the polymer chain and the crosslinking reagent. The polymers of the membranes disclosed herein include, but are not limited to, NH2, -CN, -NCO, -N3, -OH, F, Cl, Br, I, oxo, -SO2H, -SO3H, -OCO2H, -OCO2Cl, -SH, -CO2H, -CHO, -CO2Cl, C 2-12 alkenyl and C 2-12 may include one or more functional groups including alkynyl.

[0059] As used herein, the term "conditions sufficient for the polymer and the crosslinking reagent to undergo a crosslinking reaction" refers to an external stimulus (e.g., heat, UV light, microwave irradiation, the presence of a chemical initiator, e.g., a radical initiator) and the time required to form a crosslinked polymer.

[0060] As used herein, the term "degree of crosslinking" in a polymer is defined as the proportion of functional groups attached to all chains of the polymer that react to form crosslinked portions. In some embodiments, the degree of crosslinking is from about 5% to about 95%, from about 10% to about 80%, from about 20% to about 80%, from about 30% to about 70%, from about 40% to about 60%, from about 30% to about 50%, from about 20% to about 50%, from about 40% to about 70%, from about 20% to about 50% or from about 10% to about 50%.

[0061] As used herein, the term "gel fraction (%)" is calculated based on the following formula: [[M(f) / [M(i)]]*100, where M(f) is the dry mass of the membrane exposed to the solvent that dissolves the original polymer and the crosslinking agent, and M(i) is the dry mass of the membrane before exposure to the dissolving solvent. The gel fraction indicates the percentage of polymer and linker remaining in the network structure after exposure to the solvent that dissolves each individual component.

[0062] In some embodiments, the gel fraction of the crosslinked first polymer is from about 50% to about 100%. For example, the gel fraction of the crosslinked first polymer is about 50%, about 60%, about 70%, about 80%, about 90% or about 100%.

[0063] As used herein, the term "repeating unit" (also known as monomer unit) refers to the chemical moiety that, by being continuously linked together in sequence, repeats itself periodically to form a complete polymer chain (excluding end groups). A polymer can contain one or more different repeating units.

[0064] As used herein, the "main chain" of a polymer or the "backbone" of a polymer is a series of bonded atoms that together form the continuous chain of the molecule. As used herein, the "side chain" of a polymer is a series of bonded atoms that are appendages from the main chain of the polymer.

[0065] As used herein, "PFSA and the matrix polymer form an interpenetrating network structure" refers to a porous matrix containing PFSA within its pores. PFSA can penetrate into the porous matrix, for example, by immersing the matrix in a solution of PFSA or by spraying a solution of PFSA onto the porous matrix. Alternatively, a solution of PFSA monomers can penetrate into the porous matrix and a polymerization reaction can continue within the pores of the matrix.

[0066] As used herein, an "unsupported membrane" refers to a membrane that contains only a PFSA layer and a metal oxide-containing layer and does not contain any other layer, support or reinforcing substance.

[0067] As used herein, the term "continuous layer" refers to a layer in which no gaps or openings are present and any point on the layer can be connected to any other point on the layer by a straight line, with each point of the straight line belonging to the layer.

[0068] As used herein, the term "glass" refers to an amorphous material that exhibits a glass transition when heated to a liquid state. The atomic structure of glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bond constraints, glass has a high degree of short-range order with respect to local atomic polyhedra. Examples of glass include, but are not limited to, silicate glass, soda-lime glass, aluminates, phosphates, borates, chalcogenides, fluorides, germinates, and metal oxide glasses such as niobium oxide glass, tantalum oxide glass, tungsten oxide glass, vanadium oxide glass, or molybdenum oxide glass.

[0069] As used herein, the term "alkyl" refers to a radical of a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms ("C 1-10 alkyl"). In some embodiments, the alkyl group has 1 to 9 carbon atoms ("C 1-9 alkyl"). In some embodiments, the alkyl group has 1 to 8 carbon atoms ("C 1-8 alkyl"). In some embodiments, the alkyl group has 1 to 7 carbon atoms ("C 1-7 alkyl"). In some embodiments, the alkyl group has 1 to 6 carbon atoms ("C 1-6 alkyl"). In some embodiments, the alkyl group has 1 to 5 carbon atoms ("C 1-5 alkyl"). In some embodiments, the alkyl group has 1 to 4 carbon atoms ("C 1-4 alkyl"). In some embodiments, the alkyl group has 1 to 3 carbon atoms ("C 1-3"alkyl"). In some embodiments, the alkyl group has 1 to 2 carbon atoms ("C 1-2 alkyl"). In some embodiments, the alkyl group has 1 carbon atom ("C1 alkyl"). In some embodiments, the alkyl group has 2 to 6 carbon atoms ("C 2-6 alkyl"). C 1-6 Examples of alkyl groups include methyl (C1), ethyl (C2), propyl (C3) (e.g., n-propyl, isopropyl), butyl (C4) (e.g., n-butyl, tert-butyl, sec-butyl, iso-butyl), pentyl (C5) (e.g., n-pentyl, 3-pentanyl, amyl, neopentyl, 3-methyl-2-butanil, tertiary amyl) and hexyl (C6) (e.g., n-hexyl). Further examples of alkyl groups include n-heptyl (C7), n-octyl (C8), etc. Unless otherwise specified, each example of an alkyl group is independently unsubstituted ("unsubstituted alkyl") or substituted with one or more substituents (e.g., a halogen such as F) ("substituted alkyl"). In one embodiment, the alkyl group is unsubstituted C 1-10 alkyl (unsubstituted C 1-6 alkyl, e.g., -CH3 (Me), unsubstituted ethyl (Et), unsubstituted propyl (Pr, e.g., unsubstituted n-propyl (n-Pr), unsubstituted isopropyl (i-Pr)), unsubstituted butyl (Bu, e.g., unsubstituted n-butyl (n-Bu), unsubstituted tert-butyl (tert-Bu or t-Bu), unsubstituted sec-butyl (sec-Bu), unsubstituted iso-butyl (i-Bu), etc.). In one embodiment, the alkyl group is substituted C 1-10 alkyl (substituted C 1-6 alkyl, e.g., -CF3, Bn, etc.).

[0070] As used herein, the term "alkenyl" refers to a radical of a straight or branched chain hydrocarbon group having 2 to 10 carbon atoms and one or more carbon-carbon double bonds (e.g., 1, 2, 3 or 4 double bonds) ("C 2-10 alkenyl"). In some embodiments, the alkenyl group has 2 to 9 carbon atoms ("C 2-9"(alkenyl). In some embodiments, the alkenyl group has 2 to 8 carbon atoms ("C 2-8 alkenyl). In some embodiments, the alkenyl group has 2 to 7 carbon atoms ("C 2-7 alkenyl). In some embodiments, the alkenyl group has 2 to 6 carbon atoms ("C 2-6 alkenyl). In some embodiments, the alkenyl group has 2 to 5 carbon atoms ("C 2-5 alkenyl). In some embodiments, the alkenyl group has 2 to 4 carbon atoms ("C 2-4 alkenyl). In some embodiments, the alkenyl group has 2 to 3 carbon atoms ("C 2-3 alkenyl). In some embodiments, the alkenyl group has 2 carbon atoms ("C2 alkenyl"). One or more carbon-carbon double bonds can be internal (e.g., within 2-butenyl) or terminal (e.g., within 1-butenyl). C 2-4 Examples of alkenyl groups include, without limitation, vinyl (C2), 1-propenyl (C3), 2-propenyl (C3), 1-butenyl (C4), 2-butenyl (C4), etc. C 2-6 Examples of alkenyl groups include the aforementioned C 2-4 alkenyl groups, as well as pentenyl (C5), hexenyl (C6), etc. Further examples of alkenyl include heptenyl (C7), octenyl (C8), etc. Unless otherwise specified, each example of an alkenyl group is independently unsubstituted ("unsubstituted alkenyl") or substituted with one or more substituents ("substituted alkenyl"). In one embodiment, the alkenyl group is unsubstituted C 2-10 alkenyl. In one embodiment, the alkenyl group is substituted C 2-10 alkenyl.

[0071] As used herein, the term "alkynyl" refers to a radical of a straight-chain or branched-chain hydrocarbon group having 2 to 10 carbon atoms and one or more carbon-carbon triple bonds (e.g., 1, 2, 3, or 4 triple bonds) ("C 2-10"alkynyl"). In some embodiments, the alkynyl group has 2 to 9 carbon atoms ("C 2-9 "alkynyl"). In some embodiments, the alkynyl group has 2 to 8 carbon atoms ("C 2-8 "alkynyl"). In some embodiments, the alkynyl group has 2 to 7 carbon atoms ("C 2-7 "alkynyl"). In some embodiments, the alkynyl group has 2 to 6 carbon atoms ("C 2-6 "alkynyl"). In some embodiments, the alkynyl group has 2 to 5 carbon atoms ("C 2-5 "alkynyl"). In some embodiments, the alkynyl group has 2 to 4 carbon atoms ("C 2-4 "alkynyl"). In some embodiments, the alkynyl group has 2 to 3 carbon atoms ("C 2-3 "alkynyl"). In some embodiments, the alkynyl group has 2 carbon atoms ("C2 alkynyl"). One or more carbon-carbon triple bonds can be internal (e.g., within 2-butynyl) or terminal (e.g., within 1-butynyl). C 2-4 Examples of alkynyl groups include, without limitation, ethynyl (C2), 1-propynyl (C3), 2-propynyl (C3), 1-butynyl (C4), 2-butynyl (C4), etc. C 2-6 Examples of alkynyl groups include the aforementioned C 2-4 alkynyl groups, as well as pentynyl (C5), hexynyl (C6), etc. Further examples of alkynyl include heptynyl (C7), octynyl (C8), etc. Unless otherwise specified, each example of an alkynyl group is independently unsubstituted ("unsubstituted alkynyl") or substituted with one or more substituents ("substituted alkynyl"). In one embodiment, the alkynyl group is unsubstituted C 2-10 alkynyl. In one embodiment, the alkynyl group is substituted C 2-10 alkynyl.

[0072] The term "aryl" refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system having 6 to 14 ring carbon atoms and 0 heteroatoms provided within an aromatic ring system (e.g., having 6, 10, or 14 π electrons shared in a cyclic array) ("C 6-14 aryl"). In some embodiments, the aryl group has 6 ring carbon atoms ("C6 aryl"; e.g., phenyl). In some embodiments, the aryl group has 10 ring carbon atoms ("C 10 aryl"; e.g., naphthyl such as 1-naphthyl and 2-naphthyl). In some embodiments, the aryl group has 14 ring carbon atoms ("C 14 aryl"; e.g., anthracyl). "Aryl" also includes a ring system where the aryl ring as defined above is fused with one or more carbocyclic or heterocyclic groups and the point of the radical or bond is on the aryl ring, and in such an example the number of carbon atoms continues to specify the number of carbon atoms in the aryl ring system. Unless otherwise specified, each example of the aryl group is independently unsubstituted ("unsubstituted aryl") or substituted with one or more substituents ("substituted aryl"). In one embodiment, the aryl group is unsubstituted C 6-14 aryl. In one embodiment, the aryl group is substituted C 6-14 aryl.

[0073] The term "haloalkyl" refers to a substituted alkyl group where one or more of the hydrogen atoms are independently substituted with a halogen, e.g., fluoro, bromo, chloro, or iodo. In some embodiments, the haloalkyl moiety has 1 to 12 carbon atoms ("C 1-12 haloalkyl"). In some embodiments, the haloalkyl moiety has 1 to 6 carbon atoms ("C 1-6 haloalkyl"). In some embodiments, the haloalkyl moiety has 1 to 4 carbon atoms ("C 1-4 haloalkyl"). In some embodiments, the haloalkyl moiety has 1 to 3 carbon atoms ("C 1-3"haloalkyl"). In some embodiments, the haloalkyl moiety has 1 to 2 carbon atoms ("C 1-2 haloalkyl"). Examples of haloalkyl groups include -CHF2, -CH2F, -CF3, -CH2CF3, -CF2CF3, -CF2CF2CF3, -CCl3, -CFCl2, -CF2Cl, and the like.

[0074] The term "sulfonic acid group" refers to the following group: -S(O)2OH.

[0075] The term "sulfonate" refers to a salt or ester of sulfonic acid, -S(O)2OR, where R represents a cation, such as a metal or ammonium cation, or an aliphatic or aromatic substituent. Examples of sulfonates include salts such as lithium sulfonate, sodium sulfonate, potassium sulfonate, or ammonium sulfonate. In some embodiments, the term "sulfonate" refers to an ester of sulfonic acid, such as an optionally substituted C 1-12 alkyl sulfonate or an optionally substituted C6- 12 aryl sulfonate. In some embodiments, R is a polyvalent (e.g., divalent or trivalent) radical that forms a covalent or ionic bond with one or more sulfonic acid groups attached to the same or different sulfonated polymer chains, and thus forms a crosslinked moiety together with two or more -S(O)2O- groups to which it is attached.

[0076] The term "sulfonamide" refers to an amide of sulfonic acid, -S(O)2NRR', where R and R' are each hydrogen or an optionally substituted aliphatic or aromatic substituent, such as an optionally substituted C 1-12 alkyl or an optionally substituted C6- 12 aryl. In some embodiments, R and / or R' are each a polyvalent (e.g., divalent or trivalent) radical that forms a covalent or ionic bond with one or more sulfonic acid groups attached to the same or different sulfonated polymer chains, and thus forms a crosslinked moiety together with two or more -S(O)2O- groups to which it is attached.

[0077] Attaching based on the suffix “-en” indicates that the base is a divalent moiety. For example, alkylene is the divalent moiety of alkyl, alkenylene is the divalent moiety of alkenyl, alkynylene is the divalent moiety of alkynyl, and arylene is the divalent moiety of aryl.

[0078] The term "substituted" refers to a moiety having a substituent that replaces one or more hydrogens on one or more carbons of the backbone. "Substitution" or "substituted with" is understood to include the implicit proviso that such substitution follows the valences of the atoms being substituted and the substituents and that the substitution results in a stable compound that does not undergo transformation, e.g., by rearrangement, cyclization, elimination, etc. As used herein, the term "substituted" is intended to include all permissible substituents of organic compounds. In a broad aspect, permissible substituents include substituents of acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic organic compounds. Permissible substituents can be one or more and can be the same or different for suitable organic compounds. For the purposes of the present invention, heteroatoms such as nitrogen can have any permissible substituent of the organic compounds described herein that satisfies the valence of the hydrogen substituent and / or the heteroatom. Substituents include any of the substituents described herein, such as halogen, hydroxyl, carbonyl (e.g., carboxyl, alkoxycarbonyl, formyl or acyl), thiocarbonyl (e.g., thioester, thioacetate or thiocarbonate), alkoxyl, phosphoryl, phosphate, phosphonate, phosphinate, amino, amide, amidine, imine, cyano, nitro, azide, sulfhydryl, alkylthio, sulfate, sulfonate, sulfamoyl, sulfonamide, sulfonyl, heterocyclyl, aralkyl or aromatic or heteroaromatic moieties. It is understood by those skilled in the art that substituents can themselves be substituted where appropriate. References to chemical moieties herein are understood to include substituted variants unless specifically described as "unsubstituted". For example, a reference to an "aryl" group or moiety implicitly includes both substituted and unsubstituted variants.

[0079] Exemplary carbon atom substituents include, but are not limited to, halogen, -CN, -NO2, -N3, -OH, F, Cl, Br, I, oxo, -SO2H, -SO3H, -OR aa , -NH(R aa )2, -N(R aa)2, -N(R aa )3 + X - , -SH, -SR aa , -C(=O)R aa , -CO2H, -CHO, -CO2R aa , -OC(=O)R aa , -OCO2R aa , -C(=O)N(R aa )2, -OC(=O)N(R aa )2, -NR aa C(=O)R aa , -NR aa CO2R aa , -NR aa C(=O)N(R aa )2, -C(=NR aa )R aa , -C(=O)NR aa SO2R aa , -NR aa SO2R aa , -SO2N(R aa )2, -SO2R aa , -SO2OR aa , -OSO2R aa , -S(=O)R aa , -OS(=O)R aa , -Si(R aa )3, -OSi(R aa )3, C 1-12 alkyl, C 1-12 haloalkyl, 3- to 16-membered heterocyclyl and C 6-12 aryl, wherein X - is a counterion and each example of R aa is independently selected from H, -OH, C 1-10 alkyl, C 1-10 haloalkyl, C 3-12 cycloalkyl, 5- to 16-membered heterocyclyl and C 6-12 aryl or two R aa groups are linked to form a 3- to 16-membered heterocyclyl.

[0080] In a first aspect, the present invention is a two-layer polymer electrolyte membrane comprising a first layer disposed on a second layer, where: the first layer comprises a perfluorosulfonic acid (PFSA) polymer and the second layer comprises a crystalline metal oxide.

[0081] In a first aspect, a first aspect of the PFSA is of structural formula (I):

Chemical formula

Chemical formula

[0082] In a second aspect of the first aspect, the PFSA is a polymer containing repeating units represented by structural formula (I) from about 500 to about 1500. For example, the PFSA is a polymer containing repeating units represented by structural formula (I) from about 600 to about 1400, from about 700 to about 1300, from about 800 to about 1200, or from about 900 to about 1100. For example, the PFSA is a polymer containing repeating units represented by structural formula (I) of about 1000. The remaining features and exemplary features of the second aspect are as described above with respect to the first aspect of the first aspect.

[0083] In a third aspect of the first embodiment, the metal oxide includes reducible metal oxides. For example, the metal oxide includes, for example, consists of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, cerium oxide, gadolinium oxide, and samarium oxide, or combinations thereof. For example, the metal oxide includes, for example, consists of titanium oxide, zirconium oxide, niobium, and cerium oxide, or combinations thereof. For example, the metal oxide includes, for example, consists of titanium oxide, manganese oxide, niobium, and cerium oxide, or combinations thereof. For example, the metal oxide includes cerium oxide, for example, consists of cerium oxide. For example, the metal oxide is cerium oxide. For example, the metal oxide is zirconium oxide. For example, the metal oxide is manganese oxide. For example, the metal oxide is cerium oxide, zirconium oxide, or manganese oxide. The remaining of the features and exemplary features of the third aspect are as described above with respect to the first and second aspects of the first embodiment.

[0084] In the fourth aspect of the first embodiment, the metal oxide is doped with one or more dopants. For example, the metal oxide doped with one or more dopants is selected from cerium oxide doped with gadolinium, cerium oxide doped with samarium, titanium oxide doped with niobium, or zirconium oxide doped with cerium. For example, the dopant is selected from Si, In, Bi, Al, Y, Ga, Pb, Sn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For example, the metal oxide contains about 0.5 wt.% to about 5 wt.% of the dopant, such as about 0.5 wt.%, about 1 wt.%, about 1.5 wt.%, about 2 wt.%, about 2.5 wt.%, about 3 wt.%, about 3.5 wt.%, about 4.5 wt.%, about 4.5 wt.%, or about 5.0 wt.%. The remaining features and exemplary features of the fourth aspect are as described above with respect to the first to third aspects of the first embodiment.

[0085] In the fifth aspect of the first embodiment, the metal oxide is in the form of crystalline particles having a characteristic dimension of about 1 nm to about 100 nm. For example, the metal oxide is in the form of crystalline particles having a characteristic dimension of about 1 nm, about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 12 nm, about 14 nm, about 16 nm, about 18 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 690 nm, or about 100 nm. For example, the metal oxide is in the form of crystalline particles having a characteristic dimension of about 2 nm to about 50 nm, about 3 nm to about 30 nm, or about 4 nm to about 20 nm. For example, the metal oxide is in the form of crystalline particles having a characteristic dimension of about 2 nm to about 10 nm. For example, the metal oxide is in the form of crystalline particles having a characteristic dimension of about 4 nm. The remaining features and exemplary features of the fifth aspect are as described above with respect to the first to fourth aspects of the first embodiment.

[0086] In the sixth aspect of the first embodiment, the second layer further includes a polymer matrix, and the metal oxide is dispersed within the polymer matrix. For example, the second layer includes from about 5 wt.% to about 85 wt.% of the metal oxide. For example, the second layer includes from about 10 wt.% to about 85 wt.%, from about 15 wt.% to about 85 wt.%, from about 20 wt.% to about 85 wt.%, from about 25 wt.% to about 85 wt.%, from about 30 wt.% to about 85 wt.%, from about 35 wt.% to about 85 wt.%, from about 40 wt.% to about 85 wt.%, from about 45 wt.% to about 85 wt.%, from about 50 wt.% to about 85 wt.%, from about 55 wt.% to about 85 wt.%, from about 60 wt.% to about 85 wt.%, from about 65 wt.% to about 85 wt.%, from about 70 wt.% to about 85 wt.%, or from about 75 wt.% to about 85 wt.% of the metal oxide. For example, the second layer includes about 10 wt.% of the metal oxide, about 15 wt.%, about 20 wt.%, about 25 wt.%, about 30 wt.%, about 35 wt.%, about 40 wt.%, about 45 wt.%, about 50 wt.%, about 55 wt.%, about 60 wt.%, about 65 wt.%, about 70 wt.%, or about 75 wt.% of the metal oxide. For example, the second layer includes from about 30 wt.% to about 45 wt.% of the metal oxide. The remaining features and exemplary features of the sixth aspect are as described above with respect to the first to fifth aspects of the first embodiment.

[0087] In a seventh aspect of the first embodiment, the polymer matrix comprises one or more first polymers selected from polyethers, polysulfonates, polysulfones, poly(imidazoles), polysiloxanes, polyacrylates, polysulfides, polyolefins, polyamides, poly(triazoles), benzimidazoles, polyesters and polycarbonates. For example, the one or more first polymers are selected from polyethylene glycol (PEG), polyether ether ketone (PEEK), polytetrahydrofuran, polyvinyl butyral, poly(acrylonitrile-butadiene-styrene), polyether pyridine, polyphenyl sulfone (PPS), polyphosphazene (POP), polybenzimidazole (PBI), polyether sulfone (PES), polyphenylene oxide (PPO), polyarylene ether ketone (PAEK), polysulfone, poly(sulfide sulfone), polyimide (PI), poly(ether imide) (PEI), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and poly(amine). For example, the one or more first polymers are selected from PEG, PEEK, PPS, PBI and PVDF. For example, the one or more first polymers are selected from PEG, PPS, poly(ethylene imine) and PVDF. For example, the one or more first polymers comprise PEG. For example, the first polymer is PEG. For example, the first polymer is PEG diacrylate. The remaining features and exemplary features of the seventh aspect are as described above with respect to the first to sixth aspects of the first embodiment.

[0088] In an eighth aspect of the first embodiment, the one or more first polymers have a molecular weight of from about 250,000 g / mol to about 4,000,000 g / mol, such as from about 500,000 g / mol to about 1,000,000 g / mol. For example, the one or more first polymers have a molecular weight of about 300,000 g / mol, about 400,000 g / mol, about 500,000 g / mol, about 600,000 g / mol, about 700,000 g / mol, about 800,000 g / mol, about 900,000 g / mol, about 1,000,000 g / mol, about 1,500,000 g / mol, about 2,000,000 g / mol, about 2,500,000 g / mol, about 3,000,000 g / mol or about 3,500,000 g / mol. The remaining features and exemplary features of the eighth aspect are as described above with respect to the first to seventh aspects of the first embodiment.

[0089] In a ninth aspect of the first embodiment, the one or more first polymers are sulfonated. For example, the first polymer is sulfonated PPS (sPPS). The remaining features and exemplary features of the ninth aspect are as described above with respect to the first to eighth aspects of the first embodiment.

[0090] In a tenth aspect of the first embodiment, at least one of the one or more first polymers is crosslinked. For example, at least one of the one or more first polymers has the following structural formula: C 2-6 alkylene,

Chemical formula

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

[0091] In the eleventh aspect of the first embodiment, the first layer further includes a porous matrix containing a matrix polymer, where PFSA and the matrix polymer form an interpenetrating network structure. For example, the first layer contains about 50 wt.% to about 99 wt.% of PFSA, about 55 wt.% to about 98 wt.% of PFSA, about 60 wt.% to about 97 wt.% of PFSA, about 70 wt.% to about 96 wt.% of PFSA, or about 80 wt.% to about 96 wt.% of PFSA. For example, the first layer contains about 70 wt.% to about 99 wt.% of PFSA, for example, about 78 wt.% to about 95 wt.% of PFSA. The remaining features and exemplary features of the eleventh aspect are as described above with respect to the first to tenth aspects of the first embodiment.

[0092] In the twelfth aspect of the first embodiment, the matrix polymer is polytetrafluoroethylene (PTFE). For example, the matrix polymer is expanded PTFE (ePTFE). The remaining features and exemplary features of the twelfth aspect are as described above with respect to the first to eleventh aspects of the first embodiment.

[0093] In the thirteenth aspect of the first embodiment, one or more of the first polymers have a gel fraction of about 50% to about 100%. For example, the gel fraction is about 50%, about 60%, about 70%, about 80%, about 90%, or about 100%. The remaining features and exemplary features of the thirteenth aspect are as described above with respect to the first to twelfth aspects of the first embodiment.

[0094] In a fourteenth aspect of the first embodiment, the first layer has a thickness of from about 5 μm to about 200 μm. For example, the first layer has a thickness of about 5 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, about 75 μm, about 80 μm, about 85 μm, about 90 μm, about 95 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm or about 170 μm, about 180 μm, about 190 μm or about 200 μm. For example, the first layer has a thickness of from about 5 μm to about 175 μm. For example, the first layer has a thickness of about 25 μm. The remaining features and exemplary features of the fourteenth aspect are as described above with respect to the first to thirteenth aspects of the first embodiment.

[0095] In a fifteenth aspect of the first embodiment, the thickness of the second layer is from about 0.2 μm to about 175 μm. For example, the thickness of the second layer is about 0.2 μm, about 0.4 μm, about 0.6 μm, about 0.8 μm, about 1.0 μm, about 2.0 μm, about 3.0 μm, about 4.0 μm, about 5 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, about 75 μm, about 80 μm, about 85 μm, about 90 μm, about 95 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm or about 170 μm. For example, the thickness of the second layer is from about 0.2 μm to about 10 μm, from about 0.4 μm to about 5 μm, from about 0.6 μm to about 2 μm, from about 0.8 μm to about 1.5 μm. For example, the thickness of the second layer is about 1 μm. For example, the second layer has a thickness of from about 0.5 μm to about 1 μm. For example, the second layer has a thickness of about 0.7 μm. The remaining features and exemplary features of the fifteenth aspect are as described above with respect to the first to fourteenth aspects of the first embodiment.

[0096] In a sixteenth aspect of the first embodiment, the first layer is continuous. The remaining features and exemplary features of the sixteenth aspect are as described above with respect to the first to fifteenth aspects of the first embodiment.

[0097] In the 17th aspect of the first aspect, the membrane is not supported. The remaining features and exemplary features of the 17th aspect are as described above with respect to the 1st to 16th aspects of the first aspect.

[0098] In the 18th aspect of the first aspect, the first layer is made of PFSA, and PFSA is a polymer containing repeating units represented by structural formula (I):

Chemical formula

Chemical formula

[0099] In the 19th aspect of the first aspect, the second layer further contains glass, and the metal oxide is dispersed in the glass. For example, the glass contains niobium oxide, silica, tantalum oxide, tungsten oxide, vanadium oxide or molybdenum oxide. The remaining features and exemplary features of the 19th aspect are as described above with respect to the 1st to 18th aspects of the first aspect.

[0100] In the 20th aspect of the first embodiment, the sulfonation degree of the first polymer is from about 100% to about 400%. For example, the sulfonation degree of the first polymer is from about 10% to about 100%, from about 20% to about 100%, from about 30% to about 100%, from about 40% to about 100%, from about 50% to about 100%, from about 60% to about 100%, from about 70% to about 100%, from about 80% to about 100%, from about 50% to about 200%, from about 80% to about 200%, from about 100% to about 200%, from about 100% to about 250%, from about 150% to about 200%, from about 100% to about 300%, from about 100% to about 350%, from about 100% to about 400%, from about 150% to about 250%, from about 150% to about 300%, from about 150% to about 350%, from about 150% to about 400%, from about 200% to about 300%, from about 200% to about 350%, from about 200% to about 400% or from about 250% to about 350%. For example, the sulfonation degree of the first polymer is about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 100%, about 120%, about 140%, about 160%, about 180%, about 200%, about 220%, about 240%, about 260%, about 280%, about 300%, about 320%, about 340%, about 360%, about 380% or about 400%. For example, the sulfonation degree of the first polymer is from about 100% to about 300%. For example, the sulfonation degree of the first polymer is about 200%. For example, the first polymer contains, on average, a combined total of about 1 to about 3 sulfonic acid, sulfonate and sulfonamide groups per repeating unit. For example, the first polymer contains, on average, a combined total of about 2 sulfonic acid, sulfonate and sulfonamide groups per repeating unit. The remaining features and exemplary features of the 20th aspect are as described above with respect to the 1st to 19th aspects of the first embodiment.

[0101] In the 21st aspect of the first embodiment, the crosslinking degree of the first polymer is from about 10% to about 95%. For example, the crosslinking degree of the first polymer is from about 15% to about 90%, from about 20% to about 80%, from about 20% to about 70%, from about 20% to about 60%, from about 20% to about 50%, from about 20% to about 45%, from about 20% to about 40%, from about 30% to about 50%, from about 25% to about 30% or from about 30% to about 35%. For example, the crosslinking degree of the first polymer is about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% or about 95%. For example, the crosslinking degree of the first polymer is about 70%. For example, the crosslinking degree of the first polymer is about 40%. The remaining features and exemplary features of the 21st aspect are as described above with respect to the 1st to 20th aspects of the first embodiment.

[0102] In the 22nd aspect of the first embodiment, the first layer is made of PFSA, where PFSA is a polymer containing repeating units represented by structural formula (I): [Chemical formula] wherein: x is an integer from 5 to 14, m is 1 or 2, n is 2 or 3; the metal oxide is CeO2, The second layer further comprises crosslinked PEG(DA) containing a crosslinked portion represented by the following structural formula: [Chemical formula] For example, the membrane is unsupported, the crystalline particles of CeO2 have a characteristic dimension of about 4 nm, and the crosslinking degree of the crosslinked PEG(DA) is about 70%. The remaining features and exemplary features of the 22nd aspect are as described above with respect to the 1st to 21st aspects of the first embodiment.

[0103] In the 23rd aspect of the first embodiment, the membrane is unsupported, PFSA is represented by structural formula (I): [Chemical formula] A polymer containing repeating units represented by, where in the formula: x is an integer from 5 to 14, m is 1 or 2, n is 2 or 3; and further The metal oxide is CeO2, The second layer further has the following structural formula: [Chemical formula] It contains crosslinked sPPS containing a crosslinked portion represented by, The sulfonation degree of sPPS is about 200%, The crosslinking degree of sPPS is about 40%. The remaining features and exemplary features of aspect 23 are as described above with respect to aspects 1 to 22 of the first aspect.

[0104] In aspect 24 of the first aspect, The membrane is unsupported, and PFSA is a polymer containing repeating units represented by structural formula (I): [Chemical formula] where in the formula: x is an integer from 5 to 14, m is 1 or 2, n is 2 or 3; and further The metal oxide is CeO2, The second layer further has the following structural formula: [Chemical formula] It contains crosslinked sPPS containing a crosslinked portion represented by one of, The sulfonation degree of sPPS is about 200%, The crosslinking degree of sPPS is from about 25% to about 30. The remaining features and exemplary features of aspect 24 are as described above with respect to aspects 1 to 23 of the first aspect.

[0105] In a second aspect, the present invention provides a step of providing a first layer having a first surface and a suspension containing a metal oxide and a solvent; and a step of coating the first surface of the first layer with the suspension, thereby producing a coated first layer, which is a method for producing a two-layer polymer electrolyte membrane described herein with respect to the first aspect and its various aspects.

[0106] In a first aspect of the second aspect, the suspension contains about 0.01 v.% to about 74 v.% of a metal oxide. For example, the suspension contains about 0.01 v.% to about 1 v.% of a metal oxide, such as about 0.05 v.% to about 1 v.%, about 0.1 v.% to about 0.8 v.%, about 0.2 v.% to about 0.6 v.% or about 0.05 v.% to about 0.5 v.% of a metal oxide. For example, the suspension contains about 0.4 v.% of a metal oxide. For example, the suspension contains about 1 v.% to about 74 v.% of a metal oxide, such as about 1 v.% to about 74 v.%, about 10 v.% to about 70 v.%, about 15 v.% to about 65 v.%, about 20 v.% to about 60 v.%, about 25 v.% to about 55 v.% or about 30 v.% to about 50 v.% of a metal oxide. For example, the suspension contains about 35 v.% of a metal oxide.

[0107] In a second aspect of the second aspect, the suspension further contains a first polymer. For example, the suspension contains about 0.2 wt.% to about 25 wt.% of the first polymer, such as about 0.5 wt.% of the first polymer. For example, the suspension contains about 0.2 wt.%, about 0.3 wt.%, about 0.4 wt.%, about 0.6 wt.%, about 0.7 wt.%, about 0.8 wt.%, about 0.9 wt.%, about 1.0 wt.%, about 2 wt.%, about 3 wt.%, about 4 wt.%, about 5 wt.%, about 6 wt.%, about 7 wt.%, about 8 wt.%, about 9 wt.%, about 10 wt.%, about 15 wt.% or about 20 wt.% of the first polymer. The remaining features and exemplary features of the second aspect are as described above with respect to the first aspect of the second aspect.

[0108] In a third aspect of the second embodiment, the first polymer includes a crosslinkable group. For example, the crosslinkable group includes OH, NH2, NH, SH, C(O)OH, C(O)Cl, C(O)Br, NHNH2, N3, S(O)2OH, S(O)2Cl, -NCO, [Chemical formula] and is selected from the group consisting of. For example, the crosslinkable group includes OH, NH2, SH, C(O)OH, C(O)Cl, C(O)Br, NHNH2, N3, S(O)2OH, S(O)2Cl, -NCO, [Chemical formula] and is selected from the group consisting of. For example, the crosslinkable group [Chemical formula] is. For example, the crosslinkable group is NH. For example, the crosslinkable group is S(O)2OH. The remaining features and exemplary features of the third aspect are as described above with respect to the first and second aspects of the second embodiment.

[0109] In a fourth aspect of the second embodiment, the suspension further includes a crosslinking initiator. For example, the crosslinking initiator is selected from 2,2-dimethoxy-2-phenylacetophenone (DMPA), azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO). The remaining features and exemplary features of the fourth aspect are as described above with respect to the first to third aspects of the second embodiment.

[0110] In a fifth aspect of the second embodiment, the method further includes a step of crosslinking the first polymer under conditions sufficient for the crosslinking initiator to initiate crosslinking of the first polymer. For example, the conditions sufficient for the crosslinking initiator to initiate crosslinking of the first polymer include visible light irradiation, UV light irradiation, application of heat, microwave irradiation, ultrasonic waves, or gamma ray irradiation. The remaining features and exemplary features of the fifth aspect are as described above with respect to the first to fourth aspects of the second embodiment.

[0111] In the sixth aspect of the second embodiment, the suspension contains from about 0.5 wt.% to about 50 wt.% of a crosslinking initiator. For example, the suspension contains from about 5 wt.% to about 15 wt.% of a crosslinking initiator. For example, the suspension contains about 0.2 wt.%, about 0.3 wt.%, about 0.4 wt.%, about 0.6 wt.%, about 0.7 wt.%, about 0.8 wt.%, about 0.9 wt.%, about 1.0 wt.%, about 2 wt.%, about 3 wt.%, about 4 wt.%, about 5 wt.%, about 6 wt.%, about 7 wt.%, about 8 wt.%, about 9 wt.%, about 10 wt.%, about 15 wt.% or about 20 wt.% of a crosslinking initiator. The remaining features and exemplary features of the sixth aspect are as described above with respect to the first to fifth aspects of the second embodiment.

[0112] In the seventh aspect of the second embodiment, the suspension further contains a crosslinking reagent. For example, the crosslinking reagent is selected from polyalcohols, aldehydes, amines, epoxides, thiols or compounds containing terminal alkenes or alkynes. For example, the crosslinking reagent is selected from glycerol, ethylene glycol, hydroquinone, 2,5-dihydroxybenzenesulfonic acid, 2,5-dihydroxybenzene-1,4-disulfonic acid, biphenyl, tetraglycidyl bis(p-aminophenyl)methane, phenylenediamine, 4,4'-thiobisbenzenethiol and tetrafluorostyrene. For example, the crosslinking reagent is selected from glycerol, ethylene glycol, tetraglycidyl bis(p-aminophenyl)methane, phenylenediamine, 4,4'-thiobisbenzenethiol, glutaraldehyde, styrene and tetrafluorostyrene. For example, the crosslinking reagent is a polyalcohol, such as glycerol or ethylene glycol. For example, the crosslinking reagent is hydroquinone or 2,5-dihydroxybenzenesulfonic acid. The remaining features and exemplary features of the seventh aspect are as described above with respect to the first to sixth aspects of the second embodiment.

[0113] In the eighth aspect of the second embodiment, the conditions sufficient for the first polymer and the crosslinking reagent to undergo a crosslinking reaction include heating the coated first layer to a crosslinking temperature of from about 150°C to about 200°C for a crosslinking time of from about 2 hours to about 96 hours. For example, the crosslinking temperature is about 150°C, about 160°C, about 170°C, about 180°C, about 190°C or about 200°C. For example, the crosslinking temperature is about 180°C and the crosslinking time is about 4 hours. For example, the crosslinking time is about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 20 hours, about 30 hours, about 40 hours, about 50 hours, about 60 hours, about 70 hours, about 80 hours or about 90 hours. For example, the crosslinking time is about 4 hours. The remaining features and exemplary features of the eighth aspect are as described above with respect to the first to seventh aspects of the second embodiment.

[0114] In the ninth aspect of the second embodiment, coating the first surface of the first layer with the suspension includes spray coating, spin coating, drop casting, zone casting, dip coating, blade coating, printing, vacuum filtration, slot die coating, curtain coating, or combinations thereof. For example, coating the first surface of the first layer with the suspension includes spray coating. The remaining features and exemplary features of the ninth aspect are as described above with respect to the first to eighth aspects of the second embodiment.

[0115] In the tenth aspect of the second embodiment, the solvent is selected from dimethylformamide, tetrahydrofuran, N-methylformamide, formamide, acetonitrile, dimethylacetamide, propylene carbonate, ethylene carbonate, N-methylpyrrolidone, dimethyl sulfoxide, or combinations thereof. For example, the solvent is dimethylformamide. The remaining features and exemplary features of the tenth aspect are as described above with respect to the first to ninth aspects of the second embodiment.

[0116] In a third aspect, the present invention is a membrane electrode assembly (MEA) comprising a two-layer polymer electrolyte membrane, a cathode, and an anode as described herein with respect to the first aspect and its various aspects, the two-layer electrolyte membrane being disposed between the anode and the cathode.

[0117] In a first aspect of the third aspect, the cathode is disposed on the first layer of the two-layer electrolyte membrane and the anode is disposed on the second layer of the two-layer electrolyte membrane. Alternatively, the anode is disposed on the first layer of the two-layer electrolyte membrane and the cathode is disposed on the second layer of the two-layer electrolyte membrane.

[0118] In a fourth aspect, the present invention is a fuel cell comprising one or more MEAs as described herein with respect to the third aspect and its various aspects and one or more gas flow bipolar plates.

[0119] In various aspects, the present invention is 1. A two-layer polymer electrolyte membrane comprising a first layer disposed on a second layer, wherein: the first layer comprises a perfluorosulfonic acid (PFSA) polymer, and the second layer comprises a crystalline metal oxide, the two-layer polymer electrolyte membrane. 2. The PFSA polymer has the structural formula (I): [Chemical formula] and contains repeating units represented by wherein: x is an integer from 1 to 15, m is an integer from 0 to 2, n is an integer from 1 to 5, the symbol [Chemical formula] represents the point of attachment to adjacent repeating units, the two-layer polymer electrolyte membrane according to claim 1. 3. x is an integer from 5 to 14, m is 1 or 2, The two-layer polymer electrolyte membrane according to claim 2, wherein n is 2 or 3. 4. The two-layer polymer electrolyte membrane according to claim 2 or 3, wherein the PFSA polymer contains from about 900 to about 1100 repeating units represented by structural formula (I). 5. The two-layer polymer electrolyte membrane according to any one of claims 1 to 4, wherein the metal oxide contains a reducible metal oxide. 6. The two-layer polymer electrolyte membrane according to any one of claims 1 to 5, wherein the metal oxide contains titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, cerium oxide, gadolinium oxide and samarium oxide, or a combination thereof. 7. The two-layer polymer electrolyte membrane according to claim 5, wherein the metal oxide contains titanium oxide, zirconium oxide, niobium oxide and cerium oxide, or a combination thereof. 8. The two-layer polymer electrolyte membrane according to claim 5, wherein the metal oxide contains cerium oxide. 9. The two-layer polymer electrolyte membrane according to any one of claims 1 to 8, wherein the metal oxide is doped with one or more dopants. 10. The two-layer polymer electrolyte membrane according to claim 9, wherein the metal oxide doped with one or more dopants is selected from cerium oxide doped with gadolinium, cerium oxide doped with samarium, titanium oxide doped with niobium or zirconium oxide doped with cerium. 11. The two-layer polymer electrolyte membrane according to claim 9, wherein the metal oxide contains from about 0.5 wt.% to about 5 wt.% of a dopant. 12. The two-layer polymer electrolyte membrane according to any one of claims 1 to 11, wherein the metal oxide is in the form of crystalline particles having a characteristic dimension of from about 1 nm to about 100 nm. 13. The two-layer polymer electrolyte membrane according to any one of claims 1 to 11, wherein the metal oxide is in the form of crystalline particles having a characteristic dimension of from about 2 nm to about 50 nm. 14. The two-layer polymer electrolyte membrane according to any one of claims 1 to 13, wherein the second layer further contains a polymer matrix, and the metal oxide is dispersed in the polymer matrix. 15. The two-layer polymer electrolyte membrane according to claim 14, wherein the second layer contains about 5 wt.% to about 85 wt.% of a metal oxide. 16. The two-layer polymer electrolyte membrane according to claim 14 or 15, wherein the polymer matrix contains one or more first polymers selected from polyethers, polysulfonates, polysulfones, poly(imidazoles), polysiloxanes, polyacrylates, polysulfides, polyolefins, polyamides, triazoles, benzimidazoles, polyesters, and polycarbonates. 17. The two-layer polymer electrolyte membrane according to claim 14 or 15, wherein the one or more first polymers are selected from polyethylene glycol (PEG), polyether ether ketone (PEEK), polytetrahydrofuran, polyvinyl butyral, poly(acrylonitrile-butadiene-styrene), polyether pyridine, polyphenyl sulfone (PPS), polyphosphazene (POP), polybenzimidazole (PBI), polyether sulfone (PES), polyphenylene oxide (PPO), polyarylene ether ketone (PAEK), polysulfone, poly(sulfide sulfone), polyimide (PI), poly(ether imide) (PEI), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and poly(amine). 18. The two-layer polymer electrolyte membrane according to claim 14 or 15, wherein the one or more first polymers are selected from PEG, PEEK, PPS, PBI, and PVDF. 19. The two-layer polymer electrolyte membrane according to claim 16, wherein the first polymer is PEG. 20. The two-layer polymer electrolyte membrane according to any one of claims 16 to 19, wherein the one or more first polymers have a molecular weight of about 250,000 g / mol to about 4,000,000 g / mol. 21. The two-layer polymer electrolyte membrane according to claim 20, wherein the one or more first polymers have a molecular weight of about 500,000 g / mol to about 1,000,000 g / mol. 22. The two-layer polymer electrolyte membrane according to any one of claims 16 to 21, wherein the one or more first polymers are sulfonated. 23. The two-layer polymer electrolyte membrane according to any one of claims 16 to 22, wherein at least one of the one or more first polymers is crosslinked. 24. At least one of the one or more first polymers has the following structural formula:

Chem.

Chem.

Chem.

Chem.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Example

[0120] Example Materials Nafion® PFSA membrane (NR - 211) was purchased from Fuel Cell Store. Sulfuric acid (H2SO4) was purchased from Sigma - Aldrich (95 - 98%, CAS 7664 - 93 - 9). Ethylene glycol was purchased from Sigma - Aldrich (≧99%, CAS 107 - 21 - 1).

[0121] Example 1. Synthesis of cerium oxide nanocrystals. In the synthesis of 4 nm cerium oxide nanocrystals, 8.68 g of cerium nitrate hexahydrate (20 mmol, Sigma 99.999%) and 53.6 g of oleylamine (200 mmol, 90% Acros Organics) were dissolved in 100 ml of 1 - octadecene (Aldrich 90%). Doping can be introduced by replacing a portion of the cerium nitrate with an aliovalent dopant such as gadolinium or samarium nitrate. After the initial mixing, the solution was stirred at 80 °C for 1 hour under nitrogen, and then degassed at <100 mTorr vacuum at 120 °C for 1 hour. Then, the solution was heated to 230 °C at 10 °C / min. Once the solution temperature reached 230 °C, the solution was further heated to 250 °C and reacted for 2 hours. After the reaction was complete, the solution was cooled in air at about 80 °C, and 50 mL of toluene was added to the solution at that time. Then the solution was centrifuged at 1500 rpm for 10 minutes to remove the bulk precipitate. The supernatant was mixed with 600 mL of reagent alcohol and centrifuged at 7000 rpm for 10 minutes. The nanocrystals were purified three times after synthesis using a hexane / reagent alcohol combination for dispersion and precipitation, and filtered and stored using a 0.2 μm PTFE filter.

[0122] Example 2. Nanocrystal Ligand Exchange Cerium oxide nanocrystals prepared according to Example 1, suspended in hexane (Aldrich >95% n-hexane), were purified by four cycles of suspension and precipitation using hexane and reagent alcohol or acetone. The nanocrystal concentration was then diluted to 5 mg / mL, and an equal volume of N,N-dimethylformamide (DMF) (Aldrich ≧99%) was added to form a two-phase mixture. The two-phase mixture was stirred to ensure proper washing of the nanocrystals, followed by ligand stripping. If the two-phase mixture became cloudy during stirring, the nanocrystals precipitated, were washed two or more times, and the test was repeated. If the mixture remained clear and separated back into the two-phase mixture, an amount equal to approximately half the weight of the nanocrystals in solution of nitrosyltetrafluoroborate (Aldrich 95%) was added to the mixture, and the mixture was sonicated for 30 minutes to facilitate ligand removal. After phase transfer from hexane to DMF, the hexane phase was removed, replaced with fresh hexane, and shaken. After phase separation, the hexane phase was removed, and this hexane wash was repeated two or more times. The nanocrystals in DMF were purified using a DMF / toluene combination for suspension and precipitation, and purified up to six times while tracking a DMF / toluene ratio that changed from 1:2, 1:3, 1:4 to finally 1:6 DMF to toluene. For the final wash, the nanocrystals were precipitated with toluene and resuspended in anhydrous DMF for storage.

[0123] Example 3. Preparation of Polymer Solutions and Polymer-Metal Oxide Suspensions To prepare a typical polymer solution, a polymer in the range of 10 - 50 mg was weighed into a 4 mL glass vial, and 1 mL of solvent was added to the vial along with a 0.25 inch stir bar. The solution was then stirred overnight under ambient conditions.

[0124] To prepare the composite solution, the ligand-removed nanocrystals were precipitated from solution using the procedure outlined in the purification step for ligand removal in Example 2. A certain volume of the prepared polymer solution from the above was added to a centrifuge tube containing the nanocrystal pellet, and the assembly was sonicated to promote resuspension.

[0125] Example 4. Spray Coating of CeO2-PEG(DA) Suspension on Nafion® 211 Layer Using Sonotek ExactaCoat, layers of poly(ethylene glycol) diacrylate (PEG(DA)) and cerium oxide (CeO2) were deposited onto Nafion®. The spray suspension prepared as described in Example 3 consisted of 0.5 wt.% PEG(DA)700 (50 mg of PEG(DA)) and 0.04 v.% CeO2 in DMF (35 v.% CeO2 with respect to the combined volume of PEG(DA) and CeO2). The suspension was stirred overnight before use. After adding 2,2-dimethoxy-2-phenylacetophenone (DMPA) (10 wt.% with respect to PEG(DA)) to the suspension, the material was deposited and stirred for 30 minutes. During deposition, the Nafion® membrane substrate was held under vacuum. The ExactaCoat parameters used were: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 80 °C, flow rate 0.25 - 0.5 mL / min. The deposition parameters can vary as follows: Poly(ethylene glycol) diacrylate molecular weight: PEG(DA)250 - 4,000,000 Amount of CeO2: 5 v.% - 74 v.%; Substrate temperature: 5 °C - 200 °C; Nozzle height: 10 mm - 100 mm; Flow rate: 0.25 mL / min - 4 mL / min; Power: 0.8 W - 5 W; Amount of crosslinking initiator: 0.5 wt.% - 50 wt.%.

[0126] Example 5. Spray Coating of ZrO2-PEG(DA) Suspension on Nafion® 211 Layer Spray coating was performed as described in Example 4. The spray suspension prepared as described in Example 3 consisted of 0.5 wt.% PEG(DA)700 (50 mg of PEG(DA)) and 0.04 v.% ZrO2 in ethanol (35 v.% ZrO2 with respect to the combined volume of PEG(DA) and ZrO2). The following ExactaCoat parameters were used: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 60 °C, flow rate 0.25 - 0.5 mL / min.

[0127] Example 6. Spray Coating of MnO2 - PEG(DA) Suspension on Nafion® 211 Layer. Spray coating was performed as described in Example 4. The spray suspension prepared as described in Example 3 consisted of 0.5 wt.% PEG(DA)700 (50 mg of PEG(DA)) and 0.04 v.% MnO2 in ethanol (35 v.% MnO2 with respect to the combined volume of PEG(DA) and MnO2). The following ExactaCoat parameters were used: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 60 °C, flow rate 0.25 - 0.5 mL / min.

[0128] Example 7. Spray Coating of TiO2 - PEG(DA) Suspension on Nafion® 211 Layer. Spray coating was performed as described in Example 4. The spray suspension prepared as described in Example 3 consisted of 0.5 wt.% PEG(DA)700 (50 mg of PEG(DA)) and 0.04 v.% TiO2 in ethanol (35 v.% TiO2 with respect to the combined volume of PEG(DA) and TiO2). The following ExactaCoat parameters were used: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 60 °C, flow rate 0.25 - 0.5 mL / min.

[0129] Example 8. Spray Coating of Nb2O3 - PEG(DA) Suspension on Nafion® 211 Layer. Spray coating was performed as described in Example 4. The spray suspension prepared as described in Example 3 consisted of 0.5 wt.% PEG(DA)700 (50 mg of PEG(DA)) and 0.04 v.% Nb2O3 in ethanol (35 v.% Nb2O3 with respect to the combined volume of PEG(DA) and Nb2O3). The following ExactaCoat parameters were used: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 60 °C, flow rate 0.25 - 0.5 mL / min.

[0130] Example 9. Crosslinking of the metal oxide - PEG(DA) layer. The PEG(DA) / metal oxide composite coating on Nafion® prepared according to Examples 4 - 8 was crosslinked using 2,2 - dimethoxy - 2 - phenylacetophenone (DMPA) as a UV initiator at 10 wt.% in the spray - dried suspension. The crosslinking initiator was added to the suspension before deposition. The membrane was placed under UV light for 1 hour after deposition. The crosslinking parameters can vary as follows: Crosslinking time: 15 min - 48 h; Crosslinking temperature; up to 200 °C. In the preparation of solutions with equivalent results, azobisisobutyronitrile (AIBN) was also used instead of DMPA.

[0131] Example 10. Spray coating of a CeO2 - polyethyleneimine suspension on a layer of Nafion® 211. Using Sonotek ExactaCoat, layers of polyethyleneimine and cerium oxide (CeO2) were deposited onto Nafion®. The spray suspension was prepared according to Example 3 and consisted of 0.5 wt.% polyethyleneimine (60,000 MW) and 0.04 v.% CeO2 in DMF (35 v.% CeO2 with respect to the combined volume of polyethyleneimine and CeO2). The suspension was stirred overnight before use. Dibromopropane (DBP) (30 wt.% with respect to polyethyleneimine) was added to the solution and then the material was deposited and used immediately. The Nafion® membrane substrate was held under vacuum during deposition. The ExactaCoat parameters used were: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 80 °C, flow rate 0.25 - 0.5 mL / min. The deposition parameters can vary as follows: Molecular weight of polyethyleneimine: 250 - 4,000,000; Amount of CeO2: 5 v.% - 74 v.%; Substrate temperature: 5 °C - 200 °C; Nozzle height: 10 mm - 100 mm; Flow rate: 0.25 mL / min - 4 mL / min; Power: 0.8 W - 5 W; Amount of crosslinking agent: 10 wt.% - 100 wt.%.

[0132] Example 11. Crosslinking of the CeO2 - polyethyleneimine layer. The polyethyleneimine / CeO2 composite coating on Nafion® prepared according to Example 10 was crosslinked using DBP as a crosslinking agent at 30 wt.% in the spray - dried suspension. The crosslinking agent was added to the suspension before deposition. After deposition, the membrane was heated in air to 200 °C for 2 hours. The crosslinking parameters can vary as follows: Crosslinking time: 5 minutes - 48 hours; Crosslinking temperature: up to 250 °C.

[0133] Example 12. Spray coating of a CeO2 - PPS suspension on a layer of Nafion® 211. Using Sonotek ExactaCoat, layers of polyethyleneimine and cerium oxide (CeO2) were deposited onto Nafion®. The spray suspension was prepared according to Example 3 and consisted of 0.5 wt.% PPS (55,000 MW) and 0.04 v.% CeO2 in 1:1 DMSO / DMF (35 v.% CeO2 with respect to the combined volume of polyethyleneimine and CeO2). The suspension was stirred overnight before use. During deposition, the Nafion® membrane substrate was held under vacuum. The ExactaCoat parameters used were: power 0.8 - 1.3 W, nozzle height 40 mm, temperature 80 °C, flow rate 0.25 - 0.5 mL / min. The deposition parameters can vary as follows: PPS molecular weight: 1,000 - 5,000,000; Amount of CeO2: 5 v.% - 74 v.%; Substrate temperature: 5 °C - 200 °C; Nozzle height: 10 mm - 100 mm; Flow rate: 0.25 mL / min - 4 mL / min; Power: 0.8 W - 5 W; Amount of crosslinking agent: 0.5 wt.% - 100 wt.%; Amount of DMSO: 0.5 v.% - 100 v.%.

[0134] Example 13. Crosslinking of the CeO2 - PPS layer. The PPS / CeO2 composite coating on Nafion® prepared according to Example 12 was crosslinked using residual DMSO from the spray - casting solvent as a crosslinking agent. The membrane was heated to 200 °C for 2 hours in air after deposition. The crosslinking parameters can vary as follows: Crosslinking time: 15 minutes - 48 hours; Crosslinking temperature; up to 250 °C.

[0135] Example 14. Preparation of the membrane - electrode assembly. A two - layer polymer electrolyte membrane in a membrane - electrode assembly (MEA) was used to test in a single fuel cell having an active area of 5 cm 2 For MEA preparation, a 3 - inch x 3 - inch membrane was each 5 cm 2It was placed between two gas diffusion electrodes (GDEs) having an area of. The GDE has a pre-deposited catalyst layer on the surface of the microporous layer and is equipped with a catalyst layer that communicates with the membrane. 5 cm 2 A 3-inch x 3-inch PTFE gasket with a window of was placed on each surface of the membrane, the gas diffusion electrodes were included, and leakage of the reactant gas was prevented. The gasket thickness was adjusted to allow 80% compression of the GDE when the MEA was fixed between two fuel cell end plates.

[0136] Example 15. Test of a two-layer polymer electrolyte membrane in a fuel cell. The membrane performance in the fuel cell was evaluated by H2 crossover measurement, fuel cell polarization curve, and accelerated stress test.

[0137] H2 crossover measurement H2 crossover was measured by performing cyclic voltammetry, where the cathode surface electrode was scanned between 0.1 V and 0.8 V at a voltage scan rate of 2 mV / s at 80 °C and 100% RH, and the 0.4 lpm H2 flow on the anode surface and the 0.4 lpm Ar flow on the cathode surface had no back pressure. The fuel cell polarization curve was measured by performing constant voltage measurements from the open circuit potential to 0.3 V and back to the open circuit potential at 80 °C, at various RH values, with 0.5 V increments between the open circuit potential and 0.7 V and 1 V increments between 0.7 V and 0.3 V, and the 0.2 lpm H2 flow on the anode surface and the 0.2 lpm air or O2 flow on the cathode surface had a back pressure of 50 kPa g with a back pressure of.

[0138] Electrochemical impedance spectroscopy Electrochemical impedance spectroscopy was performed at 150 mA / cm using an excitation amplitude under H2 pump mode 2 at 75 mA / cm 2 The measurement was performed at 80 °C and 100% RH, and the 0.05 lpm H2 flow on the anode surface and the 0.05 lpm Ar flow on the cathode surface had no back pressure.

[0139] Surprisingly, the data in Figure 16 show that in a bilayer membrane containing Nafion® 211 coated with CeO2 nanocrystals (nancrystl) / crosslinked PEG(DA) composite, the composite and Nafion® layers show no contact resistance between each other, which means that protons do not experience excessive resistance by moving between the layers. Contact resistance between hetero-materials is frequently observed in conductive systems and presents a significant barrier to layered geometries. Therefore, a bilayer system containing two materials layered on top of each other is expected to show a decrease in ionic conductivity due to interface / contact resistance. To evaluate the contact resistance in the bilayer membrane, the area specific resistance (ASR) of a bilayer membrane containing a 25 μm Nafion® 211 membrane, a 1 μm thick coating containing 35 v.% 4 nm CeO2 particles in crosslinked PEG(DA) (75% crosslinked), and a 25 μm Nafion® 211 layer coated with a 1 μm thick coating containing 35 v.% 4 nm CeO2 particles in crosslinked PEG(DA) (75% crosslinked) was measured in a single cell fuel cell. Surprisingly, the ASR of the bilayer system is approximately equal to the sum of the ASR values of the individual layers, which means that protons do not experience excessive resistance by moving between the layers.

[0140] Accelerated Stress Test (AST) The accelerated stress test included an aggressive strenuous stage and a periodic hydration stage, with the duration of each stage reaching 4.5 h and 0.5 h respectively. During the aggressive strenuous stage, the cell was set at 110 °C, and the 0.1 lpm H2 flow on the anode and 0.1 lpm O2 flow on the cathode had no backpressure, and both gases were at 30% RH. During the hydration stage, the cell was set at 80 °C, and the 0.1 lpm H2 flow on the anode and 0.1 lpm O2 flow on the cathode had no backpressure, and both gases were at 100% RH. During the accelerated stress test, H2 crossover was measured periodically and the consumed water was recovered. The test results are shown in FIGS. 4-6.

[0141] The data in FIG. 13 show that the bilayer membrane containing Nafion® 211 coated with CeO2 nanocrystals / crosslinked PEG(DA) composite is at least twice as durable as the single-layer Nafion® 211 membrane.

[0142] Example 16. Determination of the degree of crosslinking in the PEG(DA)-containing composite. The degree of crosslinking of the PEG(DA)-containing membrane was determined by Fourier transform infrared spectroscopy (FTIR). The change in the C=C bond absorption intensity was determined by calculating the area of the IR absorption at ~1636 cm -1 which is denoted as integral(C=C). The degree of crosslinking was calculated as follows:

Equation

[0143] Example 17. Conductivity measurement of the self-supporting membrane. The membrane conductivity was measured in a four-probe geometry using an Admiral Squidstat potentiostat in a Scribner Bekktech BT-112 HT conductive cell. Conductivity was evaluated by measuring the current during linear sweep voltammetry from -0.5 V to 0.5 V. The conductivity was then calculated from the current-voltage slope using the sample thickness.

[0144] Example 18. Sulfonation of PPS. General procedure: The polymer was reacted with H2SO4 to sulfonate PPS. PPS was dissolved in concentrated H2SO4 at a concentration of 25 mg / mL and stirred at 60 - 70 °C for 10 - 48 h. The reaction mixture was added dropwise to H2O at 0 °C to precipitate the sulfonated polymer. The resulting precipitated polymer was isolated by centrifugation. Sulfonated PPS (sPPS) was redispersed in H2O at room temperature and washed using dialysis until a neutral pH was recorded. The washed sPPS was dried on a hot plate to obtain the final product. The degree of sulfonation of sPPS can be adjusted (1 - 72 h) by adjusting the reaction time.

[0145] Exemplary synthesis: The polymer was reacted with H2SO4 to sulfonate PPS (Radel-5000 NT). The PPS resin was ground into powder using an industrial grinder. PPS powder (20 g) was dissolved in concentrated H2SO4 at a concentration of 25 mg / mL and stirred at 60 °C for 8 h. The reaction mixture was added dropwise to H2O at 0 °C to precipitate the resulting sulfonated polymer. The resulting precipitated polymer was centrifuged and isolated. Sulfonated PPS (sPPS) was redispersed in H2O at room temperature and washed using dialysis until a neutral pH was recorded. The washed sPPS was dried on a hot plate to obtain the final product. The yield of the reaction was determined to be 91% by mass. When measured according to the procedure described in Example 3, the resulting product had a titration-determined IEC of 3.605 meq / g (corresponding to 2.0 sulfonic acids per repeating unit).

[0146] Of the sulfonated polymer 11H NMR was measured at a concentration of approximately 10 wt.% in DMSO-d6 to confirm the polymer structure and degree of sulfonation. 1 1H NMR spectra were acquired using a 500 MHz Bruker Ultrashield 500 Plus Spectrometer and processed using SpinWorks 4. A 30° pulse angle and 5 s pulse delay with 32 scans were used to 1 perform the 1H NMR experiment. The prepared sPPS 1 1H NMR spectra are shown in Figure 10. Using the peak integrations as shown below in Table 1, the number and position of sulfonic acid groups in the repeating unit were established as shown in Figure 10.

Table 2

[0147] The peaks were integrated and standardized by setting the peak integration of peak B to a value of 4, which is the number of B-site protons per repeating unit (Table 1). The identity of peak B is assigned based on the steric and electronic protection of the B-site from sulfonation due to the presence of the sulfone bond. The number of sulfonic acid moieties per repeating unit was calculated by the ratio of the peak integration with peak C. Furthermore, the IEC value was calculated based on the peak integration values as follows. The value of IEC is related to the weight of the material per sulfonic acid moiety. This is known as the effective weight (EW). Since the prepared sPPS has a monopolymer backbone, the ratio of the C peak integration to any hydrogen peak (matched to the number of sulfonic acid groups in the structure) was used in the following equation:

Equation

[0148] The number of sulfonic acid moieties per repeating unit was converted to EW using the following equation:

Equation

Number

Number

[0149] For sPPS, 1 Based on each of the integrated peaks in the 1H NMR spectrum, the numbers and average values obtained for IEC are in excellent alignment with the experimental IEC values obtained by titration (see Table 1). This alignment indicates that there are no other significant sulfonation positions on the repeating unit and that sPPS contains two sulfonic acid moieties located on the biphenyl moiety of the backbone as shown in FIG. 10 per repeating unit.

[0150] The teachings of all patents, published applications, and references cited herein are incorporated by reference in their entirety.

[0151] Although the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. A bilayer polymer electrolyte membrane comprising a first layer disposed on a second layer, The first layer contains a perfluorosulfonic acid (PFSA) polymer. A bilayer polymer electrolyte membrane in which the second layer contains crystalline metal oxide.

2. PFSA polymer, structural formula (I): 【Chemistry 1】 Includes iteration units represented by During the ceremony: x is an integer between 1 and 15. m is an integer between 0 and 2, n is an integer from 1 to 5, symbol 【Chemistry 2】 However, it represents a point of connection to adjacent repeating units. The two-layer polymer electrolyte membrane according to claim 1.

3. The two-layer polymer electrolyte membrane according to claim 1, wherein the metal oxide contains a reducible metal oxide.

4. The two-layer polymer electrolyte membrane according to Claim 1, wherein the metal oxide comprises titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, cerium oxide, gadolinium oxide, and samarium oxide, or a combination thereof.

5. The two-layer polymer electrolyte membrane according to claim 4, wherein the metal oxide contains cerium oxide.

6. The two-layer polymer electrolyte membrane according to claim 1, wherein the metal oxide is doped with one or more doping agents.

7. The two-layer polymer electrolyte membrane according to claim 6, wherein the metal oxide doped with one or more doping agents is selected from cerium oxide doped with gadolinium, cerium oxide doped with samarium, titanium oxide doped with niobium, or zirconium oxide doped with cerium.

8. The two-layer polymer electrolyte membrane according to claim 1, wherein the second layer further comprises a polymer matrix and metal oxides are dispersed within the polymer matrix.

9. The bilayer polymer electrolyte membrane according to claim 8, wherein the polymer matrix comprises one or more first polymers selected from polyethers, polysulfonates, polysulfones, poly(imidazoles), polysiloxanes, polyacrylates, polysulfides, polyolefins, polyamides, poly(triazoles), benzimidazoles, polyesters, and polycarbonates.

10. The two-layer polymer electrolyte membrane according to claim 8, wherein one or more first polymers are selected from poly(ethylene glycol) (PEG), polyetheretherketone (PEEK), polytetrahydrofuran, polyvinyl butyral, poly(acrylonitrile-butadiene-styrene), polyetherpyridine, polyphenylsulfone (PPS), polyphosphazene (POP), polybenzimidazole (PBI), polyethersulfone (PES), polyphenylene oxide (PPO), polyaryleneetherketone (PAEK), polysulfone, poly(sulfide sulfone), polyimide (PI), poly(etherimide) (PEI), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and poly(amine).

11. The two-layer polymer electrolyte membrane according to claim 8, wherein the first polymer is PEG-diacrylate (PEG(DA)).

12. The bilayer polymer electrolyte membrane according to claim 9, wherein one or more first polymers are sulfonated.

13. The two-layer polymer electrolyte membrane according to claim 12, wherein the first polymer is sulfonated PPS (sPPS).

14. The bilayer polymer electrolyte membrane according to claim 9, wherein at least one of one or more first polymers is crosslinked.

15. At least one of the one or more first polymers has the following structural formula: C 2-6 Alkylene, 【Chemistry 3-1】 【Chemistry 3-2】 It includes a bridge portion represented by one of the following: During the ceremony: Each of R1, R2, R3, R4, and R5 is independently selected from H, C1-12 alkyl, C1-12 haloalkyl, C6-14 aryl, and C6-14 aryl (C1-12 alkylene); R 6 is H or -SO3H, Ra is H or C1-12 alkyl; M²⁺ is selected from Mr²⁺, Ca²⁺, Ba²⁺, and Al(X)²⁺, where X is a halide, acetate, or nitrate; symbol" 【Chemistry 4】 The two-layer polymer electrolyte membrane according to claim 14, wherein " represents a point of bonding of the crosslinked portion to one or more repeating units of the first polymer.

16. The crosslinked portion has the following structural formula: 【Transformation 5】 A two-layer polymer electrolyte membrane according to claim 15, represented by one of the following.

17. The two-layer polymer electrolyte membrane according to claim 1, wherein the first layer further comprises a porous matrix containing a second polymer, and the PFSA polymer and the second polymer form a network structure in which they permeate each other.

18. The two-layer polymer electrolyte membrane according to claim 1, wherein the first layer is continuous and / or the second layer is continuous.

19. The two-layer polymer electrolyte membrane according to claim 1, wherein the membrane is not supported.

20. The first layer is made of PFSA, and the PFSA has structural formula (I): 【Transformation 6】 A polymer containing repeating units represented by, During the ceremony: x is an integer between 5 and 14, m is 1 or 2, n is 2 or 3; The metal oxide is CeO₂, (i) The second layer has the following structural formula: 【Transformation 7】 The cross-linked PEG(DA) further includes a cross-linked portion represented by, or (ii) The second layer has the following structural formula: 【Transformation 8】 Further includes a cross-linked sPPS containing a cross-linked portion represented by one of the following: The two-layer polymer electrolyte membrane according to claim 1.

21. The membrane is not supported, The crystalline particles of CeO2 have a characteristic size of approximately 4 nm. The second layer further contains cross-linked PEG(DA), The two-layer polymer electrolyte membrane according to claim 20, wherein the degree of crosslinking of the crosslinked PEG(DA) is approximately 70%.

22. The second layer further comprises glass, Metal oxides are dispersed within the glass. The two-layer polymer electrolyte membrane according to claim 1.

23. A step of providing a suspension comprising a first layer having a first surface, a metal oxide and a solvent; and A process of coating the first surface of the first layer with a suspension, thereby creating a coated first layer. A method for producing a two-layer polymer electrolyte membrane according to any one of claims 1 to 21, including the above.

24. A two-layer polymer electrolyte membrane according to any one of claims 1 to 22; Cathode; and A membrane electrode assembly (MEA) including an anode, A membrane electrode assembly (MEA) in which a two-layer electrolyte membrane is placed between the anode and cathode.

25. A fuel cell comprising one or more MEAs according to claim 24 and one or more gas flow bipolar plates.

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