Fuel cell with polymer electrolyte membrane

Abstract

The present disclosure relates to a compound represented by the following Formula 1, a polymer electrolyte membrane containing the compound, and a fuel cell having the polymer electrolyte membrane. In the formula, R1 to R4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, or a fluorine atom, wherein at least one of R1 to R4 is a fluorine atom, A is a divalent linking group, M1 and M2 are each independently potassium or sodium, and n and m are each independently an integer of 1 to 10.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2022-0041854, filed on April 4, 2022, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] The following description pertains to fuel cells with polymer electrolytes. Background Technology

[0004] Recently, the anticipated depletion of existing fossil fuels such as oil and coal, as well as the limitations of thermal power generation (which causes significant greenhouse gas emissions and environmental pollution) and nuclear power generation (which faces issues with facility stability and waste disposal), have become increasingly apparent. This has led to growing interest in more environmentally friendly and efficient alternative energy sources. As one such alternative, fuel cells have garnered particular attention due to their high efficiency, lack of emissions of pollutants such as NOx and SOx, and the availability of abundant fuels.

[0005] In fuel cells, polymer electrolyte fuel cells have been developed in various ways since they were first proposed in the 1950s for powering spacecraft, including proton exchange membrane fuel cells (PEMFCs) that use hydrogen as fuel and direct methanol fuel cells (DMFCs) that use liquid methanol as direct fuel supplied to the positive electrode. The supplied fuels, hydrogen and methanol, are virtually perpetual, with water being produced as a byproduct only through electrochemical reactions.

[0006] A fuel cell includes a membrane electrode assembly (including an anode, a cathode, and a hydrogen ion-conducting polymer electrolyte membrane located therebetween). Hydrogen or methanol supplied to the anode (oxidation electrode, positive electrode) forms hydrogen ions through a catalytic reaction. The formed hydrogen ions move through the hydrogen ion-conducting polymer electrolyte membrane to the cathode (reduction electrode, negative electrode) and encounter electrons moving through an external circuit and air or oxygen supplied to the cathode, thereby generating water, electricity, and heat through a reduction reaction.

[0007] Many types of sulfonated polymers and polymer compositions have been tested as hydrogen ion-conducting polymer electrolyte membranes. However, sulfonated polymers possess hydrogen ion transport capabilities in the hydrated state, thus presenting a problem: when fuel cells operate at temperatures above 90°C, the decomposition of sulfonic acid groups at high temperatures leads to a reduction in moisture in the polymer electrolyte membrane, resulting in a rapid decrease in proton conductivity. To address these issues, various methods have been investigated. Typical approaches include introducing inorganic oxides such as TiO2, SiO2, Al2O3, ZrO2, tetraethoxysilane (TEOS), montmorillonite, or mordenite into perfluorosulfonated ionomers such as Nafion to improve moisture carrying capacity at high temperatures and address the decrease in proton conductivity above 100°C; and introducing proton-conducting heteropoly acids (HPAs) such as zirconium phosphate (ZrP), phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, and silicotomolybdic acid to counteract the decrease in moisture carrying capacity and the resulting decrease in proton conductivity at high temperatures. However, due to the uneven dispersion of inorganic oxides, the introduction of inorganic oxides is limited in ensuring balanced physical properties such as mechanical properties and chemical durability, and there are limitations in the degradation of mechanical properties or the degradation of basic properties such as proton conductivity, thermal stability and hydration stability of polymer electrolyte membranes.

[0008] Therefore, there is a need to develop an additive for polymer electrolyte membranes that can synergistically improve properties such as mechanical properties, chemical durability, thermal stability, and proton conductivity.

[0009] [Existing technical documents]

[0010] [Patent Literature]

[0011] (Patent Document 1) KR 10-2010-0006809 A Summary of the Invention

[0012] The present invention is provided in a simplified form to introduce the selection of concepts, which will be further illustrated in the detailed description below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0013] In general, the compound is represented by the following formula 1:

[0014]

[0015] R1 to R4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, or a fluorine atom, wherein at least one of R1 to R4 is a fluorine atom, A is a divalent linking group, M1 and M2 are each independently potassium or sodium, and n and m are each independently an integer from 1 to 10.

[0016] R1 to R4 can each be a hydrogen atom independently, and at least one of R1 to R4 is a fluorine atom.

[0017] The alkyl group may have 1 to 3 carbon atoms, wherein at least one of R1 to R4 is a fluorine atom.

[0018] The fluorinated alkyl group may have 1 to 3 carbon atoms, wherein at least one of R1 to R4 is a fluorine atom.

[0019] R1 to R4 can be fluorine atoms.

[0020] In Equation 1, A can be either -O- or -S-.

[0021] In Equation 1, M1 and M2 can each be potassium independently.

[0022] M1 and M2 can be sodium.

[0023] R1 to R4 can all be fluorine atoms, A can be -O-, M1 and M2 can be sodium, and n and m can each be an integer from 1 to 3 independently.

[0024] The compound represented by Formula 1 can be represented by the following Formula 1-1:

[0025]

[0026] The polymer electrolyte membrane may contain the disclosed compounds.

[0027] The proton conductivity of the polymer electrolyte membrane can be from 24 mS / cm to 38 mS / cm under conditions of 80°C and 50% relative humidity (RH).

[0028] The proton conductivity of the polymer electrolyte membrane can be from 92 mS / cm to 120 mS / cm under conditions of 80°C and 90% relative humidity (RH).

[0029] The polymer electrolyte membrane may contain a polymer carrier, and the content of the compound is from 0.5% to 2.0% by weight, based on the weight of the polymer carrier.

[0030] In another general aspect, the membrane electrode assembly includes an anode, a cathode, and an exposed polymer electrolyte membrane disposed between the anode and the cathode.

[0031] In another general aspect, the fuel cell includes a stack comprising at least two disclosed membrane electrode assemblies and a separator disposed between the membrane electrode assemblies, a fuel supplier configured to supply fuel to the stack, and an oxidant supplier configured to supply oxidant to the stack.

[0032] Other features and aspects will become apparent from the following detailed description, drawings, and claims. Attached Figure Description

[0033] The above and other aspects, features and advantages of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0034] Figure 1 The precursor compound prepared in Example 1 according to one embodiment of the present disclosure is shown. 1 H NMR and 19 F NMR results;

[0035] Figure 2 The compound prepared in Example 1, which illustrates an embodiment of this disclosure, is shown. 1 H NMR and 19 FNMR results;

[0036] Figure 3 The FT-IR results of the compound prepared in Example 1 according to one embodiment of the present disclosure are shown;

[0037] Figure 4 The results show the solubility of the compound prepared in Example 1 according to one embodiment of the present disclosure as observed by the naked eye;

[0038] Figure 5 The results of thermogravimetric analysis of the polymer electrolyte membrane according to embodiments of the present disclosure are shown;

[0039] Figure 6 The results of glass transition temperature measurements of polymer electrolyte membranes according to embodiments of the present disclosure are displayed.

[0040] Figure 7 It is a graph showing the measurement results of water absorption and dimensional changes of the polymer electrolyte membrane according to embodiments of the present disclosure;

[0041] Figure 8 The results of proton conductivity measurements of the polymer electrolyte membrane according to embodiments of the present disclosure are shown. Detailed Implementation

[0042] The following detailed description is provided to assist the reader in gaining a full understanding of the methods, apparatus, and / or systems described herein. However, after understanding the disclosure of this application, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent. For example, apart from operations that must be performed in a certain order, it will become clear after understanding the disclosure of this application that the order of operations described herein is merely illustrative and is not limited to those set forth herein, but can be varied. Furthermore, for clarity and brevity, descriptions of features known after understanding the disclosure of this application may be omitted.

[0043] The features described herein may be embodied in various forms and should not be construed as limited to the examples set forth herein. Rather, the examples described herein are merely provided to illustrate some of the many possible ways of implementing the methods, apparatus, and / or systems described herein, which will become apparent upon understanding the disclosure of this application.

[0044] Throughout the specification, when an element such as a layer, region, or substrate is described as being "on" another element, "connected to," or "joined to" another element, it can be directly "on" another element, "connected to," or "joined to" that other element, or there may be one or more other elements in between. Conversely, when an element is described as being "directly on" another element, "directly connected to," or "directly joined to" another element, there cannot be other elements in between.

[0045] As used herein, the term “and / or” includes any one and any combination of more than two of the items listed herein.

[0046] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, elements, regions, layers, or parts, these components, elements, regions, layers, or parts are not limited by these terms. Rather, these terms are used only to distinguish one component, element, region, layer, or part from another. Therefore, the first component, element, region, layer, or part mentioned in the examples described herein may also be referred to as the second component, element, region, layer, or part without departing from the teaching of the examples.

[0047] Spatial relative terms such as “above,” “above,” “below,” and “under” may be used herein to facilitate the description of the relationship between one element and another, as shown in the figure. In addition to the orientation depicted in the figure, such spatial relative terms are also intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, an element described as “above” or “above” relative to another element will be “below” or “under” relative to said other element. Thus, depending on the spatial orientation of the device, the term “above” covers both above and below orientations. The device may also be oriented in other ways (e.g., rotated 90 degrees or otherwise), and the spatial relative terms used herein should be interpreted accordingly.

[0048] The terminology used herein is for describing various instances only and is not intended to limit this disclosure. The articles “a,” “an,” and “the” are intended to include plural forms as well, unless the context clearly indicates otherwise. The terms “comprising,” “including,” and “having” specify the presence of the stated feature, quantity, operation, component, element, and / or combination thereof, but do not exclude the presence or inclusion of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0049] Due to manufacturing techniques and / or tolerances, variations in the shape shown in the figure may occur. Therefore, the examples described herein are not limited to the specific shapes shown in the figure, but include shape variations that occur during manufacturing.

[0050] As will be apparent upon understanding the disclosure of this application, the features of the examples described herein can be combined in various ways. Furthermore, although the examples described herein have multiple configurations, it will be apparent upon understanding the disclosure of this application that other configurations are also possible.

[0051] It will be understood that the words or terms used in the specification and claims of this disclosure should not be construed as having the meanings defined in commonly used dictionaries. It will be further understood that, based on the inventor's ability to appropriately define the meanings of words or terms to best interpret the principles of this disclosure, the words or terms should be interpreted as having meanings consistent with their meanings in the context of the related art and in the technical concept of this disclosure.

[0052] [Terminology Definition]

[0053] As used herein, the term "antioxidant functional group" refers to a functional group that inhibits oxidation of oxidizing substances under conditions such as light and heat by having the property of preventing and inhibiting reactive oxygen species. For example, in an environment where polymer electrolyte membranes are attacked by free radicals, the functional group that acts as an antioxidant by reacting with oxygen free radicals of reactive oxygen species (ROS) instead of the polymer electrolyte membrane.

[0054] As used herein, the term "ion-conducting functional group" refers to a functional group that increases ion conductivity, particularly proton conductivity, for example, a functional group that does not form ionic bonds with or inhibits the formation of anionic functional groups in polymer electrolyte membranes, thereby inhibiting the reduction of ion conductivity.

[0055] As used herein, the term “membrane electrode assembly (MEA)” refers to an assembly of electrodes (anodes and cathodes) that undergo the electrochemical catalytic reaction of fuel and air and a polymer electrolyte membrane that transports hydrogen ions, and refers to a single integrated unit in which the electrodes (anodes and cathodes) and the polymer electrolyte membrane are combined together.

[0056] It will be further understood that while the terms “comprising,” “including,” and “having,” and their derivatives used herein are not specifically disclosed, these terms are not intended to exclude the presence or addition of optional ingredients, steps, or processes. To avoid any uncertainty, unless otherwise stated, all materials and methods claimed using the term “comprising” may include optional additional additives, auxiliaries, or compounds. In contrast, the term “consistently composed of” excludes optional additional ingredients, steps, or processes that are unnecessary for the work and exclude from the scope of the optional, continuous description. The term “composed of” excludes optional ingredients, steps, or processes that are not specifically described or listed.

[0057] [Measurement Methods and Conditions]

[0058] In this specification, "proton conductivity" is measured as follows: the polymer electrolyte membrane is cut into 0.5cm × 3cm samples, the samples are attached to a four-probe unit, and the temperature / humidity is equilibrated for 2 hours at 80°C and 70% relative humidity (RH) before measurement. The proton conductivity is measured by reducing the humidity from 70% RH to 20% RH using a BekkTech BT-552MX instrument, and then by increasing the humidity from 20% RH to 100% RH.

[0059] New compounds

[0060] This disclosure provides a compound with a novel structure, which is used as an additive for polymer electrolyte membranes to improve the chemical durability, thermal stability and mechanical stability of polymer electrolyte membranes, while also improving properties such as proton conductivity.

[0061] According to one embodiment of this disclosure, the compound is represented by the following formula 1:

[0062] [Formula 1]

[0063]

[0064] In Equation 1 above,

[0065] R1 to R4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, or a fluorine atom, wherein at least one of R1 to R4 is a fluorine atom.

[0066] A is a divalent linker.

[0067] M1 and M2 are each independently potassium or sodium, and

[0068] n and m are each an independent integer from 1 to 10.

[0069] According to one embodiment of the present invention, the compound represented by Formula 1 above contains both antioxidant functional groups and ion-conducting functional groups in its molecule, and is therefore used as an organic additive for polymer electrolyte membranes to prevent oxidation of polymer electrolyte membranes and improve ion conductivity.

[0070] Specifically, as a polymer electrolyte membrane, for example, sulfonated polymer electrolyte membranes are widely used. These membranes are prepared by immersing the membrane in a reagent such as sulfuric acid for sulfonation, after mixing a polymer carrier with a solution containing, if necessary, additives. The compound represented by Formula 1 above includes a butylphenyl group bonded to its molecule, and is used in the preparation of the polymer electrolyte membrane. This allows the -OM1 group of the butylphenyl group to exchange with a -OH group via an ion exchange reaction, forming a hindered phenolic group (3,5-di-tert-butyl-4-hydroxyphenyl) as an antioxidant group in the polymer electrolyte membrane. The hindered phenolic group, through the reduction reaction of its -OH group, replaces the reaction of the polymer electrolyte membrane with oxygen free radicals of ROS to prevent oxidation, thereby improving the chemical durability of the polymer electrolyte membrane.

[0071] Furthermore, since the compound represented by Formula 1 has a structure with a -OM1 group bonded at the 1 position of the phenyl group and tert-butyl groups at the adjacent 2 and 6 positions that can provide a large number of electrons, the -OH group at the 1 position (derived from the -OM1 group) can smoothly generate free radicals such as -O- through the tert-butyl groups at the 2 and 6 positions, and react with free radicals generated during fuel cell driving, thereby more effectively preventing oxidation.

[0072] In addition, additives such as inorganic antioxidants, commonly used to improve the durability of polymer electrolyte membranes, inhibit the decomposition of polymer electrolyte membranes caused by ROS, thereby improving durability. However, these additives have limitations, such as reducing proton conductivity by forming ionic bonds with cation exchange groups (-SO3-) introduced into the polymer electrolyte membrane, thus blocking proton exchange channels. However, the compounds represented by Formula 1 of this disclosure include perfluorinated sulfonate (e.g., -CF2SO3Na) as ionic conductivity functional groups and butylphenyl groups with -OM1 groups bonded to form antioxidant functional groups in the molecule, thereby improving the chemical durability of the polymer electrolyte membrane while simultaneously improving proton conductivity.

[0073] Meanwhile, as shown in reaction scheme 1 described below, the compound represented by Formula 1 above is synthesized by reacting a compound providing an ion-conducting functional group with a hindered phenol, and due to the reactivity, the reaction can occur only at the 4 position of the phenolic group. Therefore, the compound represented by Formula 1 above according to the embodiments of this disclosure has a structure in which -OM1 is bonded at the 1 position of the phenyl group, tert-butyl groups are bonded at the adjacent 2 and 6 positions, and an ion-conducting functional group is bonded at the 4 position.

[0074] Specifically, in Formula 1 above, R1 to R4 can each be a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a fluorine-substituted alkyl group having 1 to 3 carbon atoms, or a fluorine atom, wherein at least one of R1 to R4 can be a fluorine atom.

[0075] Furthermore, in Equation 1 above, A can be -O- or -S-.

[0076] In addition, in Equation 1 above, M1 and M2 can each be potassium or sodium independently.

[0077] As another example, in Equation 1 above, R1 to R4 can all be fluorine atoms, A can be -O-, M1 and M2 can be sodium, and n and m can each be an integer from 1 to 3 independently.

[0078] More specifically, the compound represented by Formula 1 can be a compound represented by Formula 1-1:

[0079] [Equation 1-1]

[0080]

[0081] Furthermore, the compound represented by Formula 1 according to the embodiments of this disclosure can be prepared by reacting the compound represented by Formula a with the compound represented by Formula b to prepare the compound represented by Formula c as a precursor compound, and by reacting the compound represented by Formula c with an alkali metal hydroxide, as shown in the following reaction scheme 1:

[0082] [Reaction Scheme 1]

[0083]

[0084] In the above reaction scheme 1, R1 to R4, A, M1, M2, n, and m can be the same as defined in Equation 1, and B1 and B2 can each be independently F, Cl, Br, or I. B1 and B2 can each be independently F, Cl, Br, or I, and can be different from each other; more specifically, B1 can be I, and B2 can be F.

[0085] Polymer electrolyte membrane

[0086] Furthermore, this disclosure provides a polymer electrolyte membrane comprising units derived from the compound.

[0087] According to one embodiment of the present invention, the polymer electrolyte membrane comprises units derived from the compound represented by Formula 1 above, and the units derived from the compound represented by Formula 1 above may be included as monomers polymerized in the polymer constituting the polymer electrolyte membrane, or may be included as additives, specifically, may be included as additives.

[0088] Here, the unit derived from the compound represented by Formula 1 can be the compound represented by Formula 2 below.

[0089] [Equation 2]

[0090]

[0091] In Equation 2 above, R1 to R4, A, M2, n and m are the same as those defined in Equation 1.

[0092] The compound represented by Formula 1 according to embodiments of the present disclosure can exist in the polymer electrolyte membrane with the same structure as the compound represented by Formula 2, because when applied to the polymer electrolyte membrane, the -OM1 group forms a -OH group by ion exchange during the sulfonation reaction used to form the polymer electrolyte membrane.

[0093] When the compound represented by Formula 1 above is included as an additive to the polymer electrolyte membrane, the polymer electrolyte membrane may comprise a polymer carrier and units derived from the compound represented by Formula 1 above, and the content of units derived from the compound represented by Formula 1 above may be from 0.5% to 2.0% by weight relative to 100% by weight of the polymer.

[0094] In addition, there are no particular restrictions on the polymer carrier, as long as it is known. However, it can be, for example, a perfluorosulfonic acid polymer, a hydrocarbon polymer, a polyimide, polyvinylidene fluoride, a polyethersulfone, a polyphenylene sulfide, a polyphenylene ether, a polyphosphazene, a polyethylene naphthalate, a polyester, a doped polybenzimidazole, a polyetherketone, a polysulfone, or an acid or base thereof.

[0095] Furthermore, in addition to containing units derived from compounds represented by Formula 1, the polymer electrolyte membranes according to embodiments of this disclosure can be prepared by materials or methods known in the art, and their thickness can range from several micrometers to hundreds of micrometers.

[0096] Furthermore, the polymer electrolyte membrane disclosed herein contains units derived from compounds represented by Formula 1, and therefore can possess excellent chemical durability, thermal stability, and mechanical properties, as well as excellent proton conductivity.

[0097] For example, the proton conductivity of the polymer electrolyte membrane under conditions of 80°C and 50% relative humidity (RH) can be from 24 mS / cm to 38 mS / cm.

[0098] Furthermore, the proton conductivity of the polymer electrolyte membrane can be from 92 mS / cm to 120 mS / cm under conditions of 80°C and 90% relative humidity (RH).

[0099] Furthermore, the ion exchange capacity (IEC) of the polymer electrolyte membrane can be from 0.70 mEq / g to 0.80 mEq / g.

[0100] Membrane electrode assembly

[0101] Furthermore, this disclosure provides a membrane electrode assembly comprising the polymer electrolyte membrane.

[0102] A membrane electrode assembly according to an embodiment of the present disclosure includes: an anode; a cathode; and a polymer electrolyte membrane disposed between the anode and the cathode.

[0103] As another example, a membrane electrode assembly may include a polymer electrolyte membrane and an anode and a cathode facing each other, separated by the polymer electrolyte membrane therebetween.

[0104] The anode may include an anode catalyst layer and an anode gas diffusion layer, and the anode gas diffusion layer may further include an anode microporous layer and an anode electrode substrate. In this case, the anode gas diffusion layer is disposed between the anode catalyst layer and the polymer electrolyte membrane.

[0105] Furthermore, the cathode may include a cathode catalyst layer and a cathode gas diffusion layer, and the cathode gas diffusion layer may further include a cathode microporous layer and a cathode electrode substrate. In this case, the cathode gas diffusion layer is disposed between the cathode catalyst layer and the polymer electrolyte membrane.

[0106] The anode catalyst layer is where the fuel oxidation reaction occurs, and catalysts selected from the group consisting of platinum, ruthenium, osmium, platinum-ruthenium alloys, platinum-osmium alloys, platinum-palladium alloys, and platinum-transition metal alloys can be used. The cathode catalyst layer is where the oxidant reduction reaction occurs, and platinum or platinum-transition metal alloys can be used as catalysts. Here, the catalyst can be used alone or supported on a carbon-based support.

[0107] Furthermore, the catalyst layer for each electrode can be introduced into the electrode using methods known in the art. For example, the catalyst layer can be formed by directly coating the polymer electrolyte membrane with catalyst ink or by coating a gas diffusion layer with catalyst ink. In this case, there are no particular limitations on the coating method of the catalyst ink; for example, spraying, casting, screen printing, blade coating, extrusion coating, or spin coating can be used. In addition, the catalyst ink may contain a catalyst, a polymer ionomer, and a solvent.

[0108] The gas diffusion layer of each electrode acts as a current conductor and serves as a channel for the movement of reactant gases and water, and can have a porous structure. Therefore, the gas diffusion layer can contain a conductive substrate, such as carbon paper, carbon cloth, or carbon felt. Furthermore, the gas diffusion layer can also contain a microporous layer located between the catalyst layer and the electrode substrate. This microporous layer can reduce the amount of water flowing out of the gas diffusion layer to maintain a sufficiently wetted polymer electrolyte membrane, thereby improving the performance of the fuel cell under low humidity conditions.

[0109] fuel cells

[0110] Furthermore, this disclosure provides a fuel cell including the membrane electrode assembly.

[0111] A fuel cell according to an embodiment of the present disclosure includes: a stack comprising at least two membrane electrode assemblies and a separator disposed between the membrane electrode assemblies; a fuel supply configured to supply fuel to the stack; and an oxidant supply configured to supply oxidant to the stack.

[0112] The stack may contain at least two membrane electrode assemblies, and a partition may be disposed between the membrane electrode assemblies. The partition serves to prevent electrical connection between the membrane electrode assemblies and to deliver fuel and oxidant supplied from the outside to the membrane electrode assemblies.

[0113] Oxidant suppliers are used to supply oxidants to the stack, and oxygen can typically be used as the oxidant, which can be injected by a pump.

[0114] In addition, the fuel supply unit, used to supply fuel to the stack, may include a fuel tank configured to store fuel and a pump configured to supply the fuel stored in the fuel tank to the stack. Alternatively, gaseous or liquid hydrogen or hydrocarbons may be used as fuel, and hydrocarbons may include methanol, ethanol, propanol, butanol, or natural gas.

[0115] Example

[0116] The present disclosure will be described in more detail below with reference to embodiments. However, embodiments of the present disclosure may be modified in many different forms, and the scope of the present disclosure should not be construed as limited to the embodiments described below. Rather, embodiments of the present disclosure are provided to make this description sufficiently complete and to fully convey the scope of the present disclosure to those skilled in the art.

[0117] Example 1

[0118] (1) Preparation of 2-(2-(3,5-di-tert-butyl-4-hydroxyphenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonyl fluoride

[0119] 2,6-Di-tert-butylphenol (0.2 g, 0.96 mmol) and tetrafluoro-2-(tetrafluoro-2-iodoethoxy)ethanesulfonyl fluoride (2.47 g, 6.0 mmol) were reacted in 4 mL of solvent (CHCl3:H2O = 1:1) with a catalyst consisting of Na2S2O4 (1.7 g, 9.6 mmol), NaHCO3 (0.07 g, 0.84 mmol), and hexadecyltrimethylammonium bromide (0.35 g, 0.96 mmol) at 70 °C for 48 hours with stirring. After the reaction, 1M HCl (0.8 mL) was added to adjust the pH to 1-2. The mixture was diluted with 2 mL of distilled water, extracted with diethyl ether (3 x 10 mL) and brine (2 x 10 mL), and purified by column chromatography (100% hexane) to prepare 2-(2-(3,5-di-tert-butyl-4-hydroxyphenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonyl fluoride as a precursor compound. The synthesis was carried out by... 1 H NMR (CDCl3) and 19 F NMR (CDCl3) analysis confirmed the results, as shown in... Figure 1 .

[0120] like Figure 1 As shown, the benzene ring peak (peak 1), methyl moiety peak (peak 2), and -OH peak (peak 3) of the phenolic group are identified in... 1 In the H NMR results. Furthermore, from 19 The F NMR results are identified by the CF2 peaks (peaks 1, 2, 3, and 4) and the sulfonyl fluoride peak (peak 5).

[0121] (2) Preparation of sodium 2-(2-(3,5-di-tert-butyl-4-oxophenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonate

[0122] 2-(2-(3,5-di-tert-butyl-4-hydroxyphenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonyl fluoride (1 g, 1.98 mmol) and NaOH (0.23 g, 5.95 mmol) prepared in 3 mL of distilled water were reacted at 95 °C for 16 h. The solvent was then removed using an evaporator, the organic layer was dissolved by adding ethanol, the salt was removed by vacuum filtration, and the mixture was dried in a vacuum oven at 50 °C for 12 h to prepare sodium 2-(2-(3,5-di-tert-butyl-4-oxophenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonate as the compound represented by formula 1-1. The synthesis was carried out via... 1 H NMR (DMSO-d6) and 19 F NMR (DMSO-d6) analysis confirmed the results, as shown in... Figure 2 Furthermore, the synthesis of the compound was confirmed by FT-IR analysis, and the results are shown in... Figure 3 .

[0123] like Figure 2 As shown, in 1 In the H NMR results, it was confirmed that... Figure 1 In comparison, the benzene ring peak (peak 1) shifted and changed, while the -OH peak of the phenolic group (peak 3) disappeared. Furthermore, in 19 In the F NMR results, it was confirmed that... Figure 1 In comparison, the -CF2 peaks (peaks 1, 2, 3 and 4) shifted slightly and the sulfonyl fluoride peak (peak 5) disappeared.

[0124] like Figure 3 As shown, the hydrogen bond peak is at 3615 cm⁻¹. -1 The vicinity is identifiable, thus confirming that the -OH peak of the phenolic group has been replaced by -O-Na, and the CH peak is at 2960 cm⁻¹. -1 Nearby was detected, CF key is 1200cm -1 nearby.

[0125] Experimental Example 1

[0126] The thermal stability and solubility of the compound in Example 1 were compared and analyzed.

[0127] (1) Thermal stability

[0128] Thermal stability was confirmed by thermogravimetric analysis (TGA). Specifically, each compound sample was placed in the furnace of the TGA analyzer and heated from room temperature to 120°C at a rate of 20°C / min and held for 10 minutes to remove residual water and stabilize the sample. Subsequently, the sample was cooled to 60°C at a rate of 20°C / min and then heated from 60°C to 800°C at a rate of 10°C / min under a nitrogen atmosphere, while the weight change of the sample was measured. The results are shown in Table 1 below.

[0129] (2) Solubility

[0130] The solubility of each compound sample was observed by dissolving equal amounts in a total of six solvents, including water, dimethylacetamide (DMAc), methanol, ethanol, 1-propanol, and 2-propanol. The results are shown in Table 1 and [other tables not provided]. Figure 4 In the results, if phase separation is not visible to the naked eye and the sample dissolves well, it is indicated by ○; if phase separation is visible or the sample does not dissolve, it is indicated by ×.

[0131] [Table 1]

[0132]

[0133] Referring to Table 1 above, it is confirmed that the compound of Example 1 is insoluble in water and decomposes when the temperature reaches very high levels.

[0134] Example 2

[0135] Prepare a polymer electrolyte membrane containing the compound prepared in Example 1 as an additive.

[0136] The compound prepared in Example 1, at 0.5 wt% relative to Nafion, was added to 3 g of a 20 wt% Nafion solution. The solution was stirred at room temperature for 1 hour to prepare a solution. The solution was cast onto a glass plate and dried in an oven at 60°C for 3 hours to prepare a membrane. The membrane was then separated from the glass plate using a water permeation method, impregnated with a 1M sulfuric acid solution at 60°C for 6 hours, and then washed until neutral. The membrane was then dried at 50°C for 2 hours using a gel desiccator to prepare a polymer electrolyte membrane with a thickness of 50 μm.

[0137] Example 3

[0138] The polymer electrolyte membrane was prepared in the same manner as in Example 2, except that the compound prepared in Example 1 was added at 1.0 wt% relative to Nafion.

[0139] Example 4

[0140] The polymer electrolyte membrane was prepared in the same manner as in Example 2, except that the compound prepared in Example 1 was added at 2.0 wt% relative to Nafion.

[0141] Comparative example

[0142] The polymer electrolyte membrane was prepared in the same manner as in Example 2, except that no compound was added.

[0143] Experimental Example 2

[0144] The thermal stability, chemical durability, mechanical properties, ion exchange capacity, and proton conductivity of the polymer electrolyte membranes prepared in Examples 2 to 4 and the Comparative Examples were compared and analyzed.

[0145] (1) Thermal stability

[0146] Thermal stability was confirmed by thermogravimetric analysis (TGA) and glass transition temperature (Tg) measurements, and the results are shown in Table 2. Figure 5 and Figure 6 .

[0147] In the thermogravimetric analysis, each polymer electrolyte membrane sample was placed in the heating furnace of the thermogravimetric analyzer and heated from room temperature to 120°C at a rate of 20°C / min and held for 10 minutes to remove residual water and stabilize the sample. Subsequently, the sample was cooled to 60°C at a rate of 20°C / min and heated from 60°C to 800°C at a rate of 10°C / min under a nitrogen atmosphere, while the weight change of the sample was measured.

[0148] Glass transition temperature was analyzed using a dynamic mechanical analyzer. Each polymer electrolyte membrane was cut into 20mm×5mm pieces and used as a sample. The conditions were set to a frequency of 1Hz and an amplitude of 15μm. Tanδ was measured while the temperature was increased from 30℃ to 120℃ at a rate of 3℃ / min. The maximum point of tanδ was recorded as the glass transition temperature.

[0149] [Table 2]

[0150]

[0151] According to Table 2, Figure 5 and Figure 6 The results confirmed that the polymer electrolyte membranes of Examples 2 to 4, which contained the compound of Example 1 as an additive, had higher glass transition temperature and decomposition temperature than the polymer electrolyte membranes of the comparative examples. Therefore, it can be confirmed that the polymer electrolyte membranes of Examples 2 to 4 have excellent thermal stability.

[0152] (2) Chemical durability

[0153] The chemical durability of the polymer electrolyte membrane was confirmed by measuring water absorption and dimensional changes. Three measurements were performed on each sample, and the results are shown as averages. The results are presented in Table 3 and... Figure 7 .

[0154] Each polymer electrolyte membrane, after being dried in a desiccator, was cut into 1cm × 3cm pieces, and its thickness and weight were measured. Then, the cut polymer electrolyte membranes were placed in small vials, filled with distilled water, and stored in a 30°C drying oven for 12 hours. The swollen polymer electrolyte membranes were then removed, and their area, thickness, and weight were measured. Water absorption and dimensional changes were measured using the following formulas 1 and 2.

[0155] [Calculation Formula 1]

[0156] Water absorption (%) = [(W) 湿 -W 干 ) / W 干 ]×100

[0157] [Calculation Formula 2]

[0158] Size change (%) = [((A) 湿 ×T 湿 )-(A 干 ×T 干 )) / (A 干 ×T 干 )]×100

[0159] In calculations 1 and 2, W 干 and W 湿 A represents the weight of the dry polymer electrolyte membrane and the swollen polymer electrolyte membrane, respectively. 干 and A 湿 T represents the area of ​​the dry polymer electrolyte membrane and the swollen polymer electrolyte membrane, respectively. 干 and T 湿 These represent the thicknesses of the dry polymer electrolyte membrane and the swollen polymer electrolyte membrane, respectively.

[0160] [Table 3]

[0161]

[0162] See Table 3 and Figure 7 It can be confirmed that the polymer electrolyte membranes of Examples 2 to 4 have significantly less water absorption and dimensional change than the polymer electrolyte membranes of the comparative examples. Therefore, it can be confirmed that the polymer electrolyte membranes of Examples 2 to 4 have excellent chemical durability.

[0163] (3) Mechanical properties

[0164] The mechanical properties of each polymer electrolyte membrane were determined by tensile strength, elastic modulus, and elongation.

[0165] Specifically, a 250N load cell was connected to the LLOYD UTM LSI apparatus, and polymer electrolyte membrane samples prepared according to ASTM D638V were used. Tensile strength, elastic modulus, and elongation were then measured at a tensile rate of 5 mm / min. In this case, each sample was measured seven times, and the results are shown as the average value, as presented in Table 4 below:

[0166] [Table 4]

[0167]

[0168] Referring to Table 4, it is confirmed that the mechanical properties of the polymer electrolyte membranes of Examples 2 to 4 are significantly better than those of the polymer electrolyte membranes of the comparative examples.

[0169] (4) Proton conductivity

[0170] Proton conductivity was measured in two states: the un-oxidized state and the oxidized state.

[0171] 1) Uninduced oxidized proton conductivity

[0172] Proton conductivity was measured as follows: Each polymer electrolyte membrane was cut into 0.5 cm × 3 cm samples, which were then bonded to a four-probe unit. Before measurement, the samples were equilibrated at 80°C and 70% relative humidity (RH) for 2 hours. Proton conductivity was measured using a BekkTech BT-552MX instrument by decreasing the humidity from 70% RH to 20% RH, and then by increasing the humidity from 20% RH to 100% RH. Each polymer electrolyte membrane was measured three times, and the results are shown in Table 5. Figure 8 The average value is shown in the figure.

[0173] [Table 5]

[0174]

[0175] See Table 5 and Figure 8 It was confirmed that the polymer electrolyte membranes of Examples 2 to 4 had significantly improved proton conductivity compared with the polymer electrolyte membranes of the comparative examples.

[0176] 2) Proton conductivity after induced oxidation (Fenton test)

[0177] The polymer electrolyte membranes of Example 3 and Comparative Example 2 were each cut into 0.5 cm × 3 cm samples, their weights were measured, and then placed in 30 mL vials. 25 mL of Fenton's reagent (3% hydrogen peroxide, 4 ppm ferric sulfate aqueous solution) was added to the vials, and the samples were immersed in the reagent at 80°C for 24 hours. Afterward, each immersed sample was washed several times with distilled water and dried, and then its proton conductivity was measured in the same manner as described in 1) above. The results are shown in Table 6 below:

[0178] [Table 6]

[0179]

[0180] Referring to Table 6, in Example 2, there was no significant change in proton conductivity before and after induced oxidation, and the proton conductivity was superior to that of the comparative example. However, in the comparative example, the proton conductivity was significantly reduced after oxidation compared to before oxidation. This means that the polymer electrolyte membrane of Example 2 was prevented from being oxidized, and therefore the compound of this disclosure has excellent antioxidant effects.

[0181] (5) Ion exchange capacity

[0182] Weigh each dried polymer electrolyte membrane and place it in a 30 mL vial. Add 15 mL of 1 M NaCl solution to the vial and stir at 60 °C for at least 6 hours to prepare a sample for ion exchange capacity measurement. Use a potentiometric titrator (TITRANDO 888) to add 0.01 M NaOH solution to the vial containing the polymer electrolyte membrane until the pH of the solution inside the vial reaches 7.0. Check the total input NaOH volume, and then calculate the ion exchange capacity using the following formula 3. The results are shown in Table 7 below.

[0183] [Calculation Formula 3]

[0184] IEC w =[C NaOH ×(△V NaOH / W s )]×1000

[0185] In calculation formula 3, C NaOH The value represents the concentration of NaOH (0.01M), ΔV. NaOH W represents the total volume of injected NaOH. s This indicates the weight of the dried polymer electrolyte membrane.

[0186] [Table 7]

[0187]

[0188] Referring to Table 7, it is confirmed that the polymer electrolyte membranes of Examples 2 to 4 exhibited superior ion exchange capacities equal to or higher than those of the comparative examples.

[0189] According to Tables 2 to 7 and Figures 4 to 8 The results show that the compound represented by Formula 1 according to the embodiments of the present disclosure has excellent antioxidant and ion conduction effects, and the polymer electrolyte membrane of the present disclosure contains the compound as an additive, thereby having excellent chemical durability, thermal stability and mechanical stability, and significantly improving proton conductivity.

[0190] The compounds disclosed herein contain both antioxidant and ion-conducting functional groups in their molecules, and are therefore used as additives for polymer electrolyte membranes to improve the chemical durability, thermal stability and mechanical stability of polymer electrolyte membranes, while also enhancing properties such as proton conductivity.

[0191] The polymer electrolyte membrane disclosed herein contains a compound represented by Formula 1 as an additive, thus exhibiting improved chemical durability, thermal stability, and mechanical stability, as well as excellent properties such as proton conductivity.

[0192] The membrane electrode assembly and fuel cell disclosed herein are provided with the polymer electrolyte membrane, and therefore have excellent durability and efficiency.

[0193] Although this disclosure includes specific examples, it will be apparent upon understanding the disclosure of this application that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein should be considered merely illustrative and not for limiting purposes. The description of features or aspects in the various examples should be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are implemented in a different order and / or if components in the described system, architecture, apparatus, or circuit are combined in different ways and / or replaced or supplemented by other components or their equivalents. Therefore, the scope of this disclosure is not limited by the detailed description but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be construed as being included in this disclosure.

Claims

1. The compound represented by Formula 1 below: in, R1 to R4 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group having 1 to 6 carbon atoms, or a fluorine atom, wherein at least one of R1 to R4 is a fluorine atom. A is -O- or -S-. M1 and M2 are each independently potassium or sodium, and n and m are each an independent integer from 1 to 10.

2. The compound of claim 1, wherein, R1 to R4 are each independently a hydrogen atom, and at least one of R1 to R4 is a fluorine atom.

3. The compound of claim 1, wherein, The alkyl group has 1 to 3 carbon atoms, wherein at least one of R1 to R4 is a fluorine atom.

4. The compound of claim 1, wherein, The fluorinated alkyl group has 1 to 3 carbon atoms, wherein at least one of R1 to R4 is a fluorine atom.

5. The compound of claim 1, wherein, R1 to R4 are fluorine atoms.

6. The compound of claim 1, wherein, M1 and M2 are potassium.

7. The compound of claim 1, wherein, M1 and M2 are sodium.

8. The compound of claim 1, wherein, R1 to R4 are fluorine atoms. A is -O-, M1 and M2 are sodium, and n and m are each an independent integer from 1 to 3.

9. The compound of claim 1, wherein, The compound represented by Formula 1 is the compound represented by Formula 1-1 below:

10. A polymer electrolyte membrane comprising the compound of claim 1.

11. The polymer electrolyte membrane of claim 10, wherein, The polymer electrolyte membrane exhibits a proton conductivity of 24 mS / cm to 38 mS / cm under conditions of 80°C and 50% relative humidity (RH).

12. The polymer electrolyte membrane of claim 10, wherein, The polymer electrolyte membrane exhibits a proton conductivity of 92 mS / cm to 120 mS / cm under conditions of 80°C and 90% relative humidity (RH).

13. The polymer electrolyte membrane of claim 10, further comprising a polymer support, and the content of the compound being from 0.5% by weight to 2.0% by weight based on the weight of the polymer support.

14. A membrane electrode assembly comprising: anode; cathode; and The polymer electrolyte membrane of claim 10 is disposed between the anode and the cathode.

15. A fuel cell comprising: A stack comprising at least two membrane electrode assemblies as described in claim 14 and a spacer disposed between the membrane electrode assemblies; A fuel supply configured to supply fuel to the stack; and An oxidant supplier configured to supply oxidant to the stack.

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