阅读说明：本技术 膜-电极组件的包括电子绝缘层的电解质膜及其制备方法 (Electrolyte membrane of membrane-electrode assembly including electron insulating layer and method of preparing the same ) 是由 金柄秀 金容民 柳厦英 崔镇怡 朴洙安 李柱泳 金正翊 金民暻 于 2019-11-29 设计创作，主要内容包括：本发明涉及膜-电极组件的包括电子绝缘层的电解质膜及其制备方法,所述电子绝缘层极大地改进电解质膜的耐久性。所述电解质膜包括离子交换层以及设置在离子交换层上的电子绝缘层,所述电子绝缘层包括一种或更多种催化剂复合物和第二离聚物。具体地,一种或更多种催化剂复合物中的每一种包括催化剂颗粒和涂覆在催化剂颗粒的整个或部分表面上的第一离聚物,并且一种或更多种催化剂复合物分散在第二离聚物中。(The present invention relates to an electrolyte membrane of a membrane-electrode assembly including an electron insulating layer that greatly improves the durability of the electrolyte membrane, and a method of preparing the same. The electrolyte membrane includes an ion exchange layer and an electron insulating layer disposed on the ion exchange layer, the electron insulating layer including one or more catalyst composites and a second ionomer. Specifically, each of the one or more catalyst composites includes catalyst particles and a first ionomer coated on the entire or part of the surface of the catalyst particles, and the one or more catalyst composites are dispersed in a second ionomer.)

1. An electrolyte membrane of a membrane-electrode assembly, comprising:

an ion exchange layer; and

an electron insulating layer disposed on the ion exchange layer,

wherein the electronic insulating layer comprises:

one or more catalyst composites, each of which comprises catalyst particles and a first ionomer coated on the entire or part of the surface of the catalyst particles; and a second ionomer comprising a polymer matrix in which the catalyst composite is dispersed.

2. The electrolyte membrane of the membrane-electrode assembly according to claim 1, wherein the ion exchange layer comprises a porous reinforcement layer, a first ion exchange layer disposed on a first surface of the reinforcement layer, and a second ion exchange layer disposed on a second surface of the reinforcement layer.

3. The electrolyte membrane of the membrane-electrode assembly according to claim 1, wherein the ion exchange layer comprises an ion exchange material.

4. The electrolyte membrane of the membrane-electrode assembly of claim 3, wherein the ion exchange material is the same as the second ionomer.

5. The electrolyte membrane of the membrane-electrode assembly according to claim 1, wherein the catalyst particles include a metal catalyst and a carbon support, wherein the metal catalyst is supported on the carbon support.

6. The electrolyte membrane of the membrane-electrode assembly according to claim 5, wherein the metal catalyst includes platinum.

7. The electrolyte membrane of a membrane-electrode assembly according to claim 1, wherein the first ionomer is the same as the second ionomer or comprises a polymeric material having shorter side chain groups than the second ionomer.

8. The electrolyte membrane of the membrane-electrode assembly of claim 1, wherein at least one of the first ionomer and the second ionomer comprises perfluorosulfonic acid.

9. The electrolyte membrane of the membrane-electrode assembly according to claim 1, wherein the electron insulating layer includes the catalyst particles in an amount of 0.5 to 5 wt%, based on the total weight of the electron insulating layer.

10. A membrane-electrode assembly, comprising:

the electrolyte membrane according to claim 1; and

a pair of electrodes disposed on both surfaces of the electrolyte membrane.

11. A method of preparing an electrolyte membrane of a membrane-electrode assembly, comprising:

preparing a first blend by dispersing catalyst particles into a first ionomer solution;

drying the first blend to obtain one or more catalyst composites;

preparing a second blend by dispersing one or more catalyst composites into a second ionomer solution; and

the second admixture is applied onto the ion exchange layer and the applied second admixture is dried to form the electron insulating layer.

12. The method of claim 11, further comprising heat treating the electronically insulating layer.

13. The method of claim 11, wherein the first admixture is dried at a temperature of 25 ℃ to 160 ℃.

14. The method of claim 11, wherein the second blend is dried at a temperature of 25 ℃ to 100 ℃ to form an electronically insulating layer.

15. The method of claim 12, wherein the electronically insulating layer is heat treated at a temperature of 160 ℃ to 200 ℃.

16. A fuel cell comprising the membrane-electrode assembly according to claim 10.

Technical Field

The present invention relates to an electrolyte membrane of a membrane-electrode assembly including an electron insulating layer, which can significantly improve the durability of the electrolyte membrane, and a method of preparing the same.

Background

In a Polymer Electrolyte Membrane Fuel Cell (PEMFC), an electrolyte membrane is used to transfer hydrogen ions. In the prior art, ion exchange materials have been used to prepare electrolyte membranes for the transfer of hydrogen ions. The ion exchange material typically contains moisture to selectively move hydrogen ions generated at the anode to the cathode.

The electrolyte membrane is degraded due to the exchange of hydrogen, thereby decreasing the durability of the electrolyte membrane. For example, hydrogen contacts oxygen at the interface between the electrolyte membrane and the cathode due to the exchange of hydrogen and oxygen, thereby generating hydrogen peroxide. The hydrogen peroxide is decomposed into hydroxyl radicals (. OH) and hydroperoxy radicals (. OOH), thereby degrading the electrolyte membrane.

In recent years, in order to reduce the cost and reduce the ionic resistance of the electrolyte membrane, the thickness of the electrolyte membrane has been reduced. However, the thinner the electrolyte membrane is, the more the amount of hydrogen exchange is. As a result, the life of the electrolyte membrane gradually decreases.

In order to solve the above problems, a technique of adding a small amount of catalyst to an electrolyte membrane to prevent generation of radicals has been proposed. However, when the electrolyte membrane starts to deteriorate due to radicals formed from hydrogen peroxide, chemical deterioration of the electrolyte membrane is accelerated due to a catalyst included in the electrolyte membrane. Thus, there remains a need for improvement thereof.

The above information disclosed in this background section is only provided to enhance understanding of the background of the invention and therefore the information that it may contain does not constitute prior art that is already known in this country to a person skilled in the art.

Disclosure of Invention

In a preferred aspect, there is provided an electrolyte membrane of a membrane-electrode assembly, which can effectively prevent degradation of the electrolyte membrane due to exchange of hydrogen and oxygen. Further, an electrolyte membrane of a membrane-electrode assembly having significantly improved durability is provided.

The objects of the present invention are not limited to those described above. The objects of the present invention will be clearly understood from the following description, and can be achieved by the means defined in the claims and combinations thereof.

In one aspect, an electrolyte membrane of a membrane-electrode assembly is provided. The electrolyte membrane must be an electron insulating layer. Not only the electrolyte membrane but also the surroundings of the catalyst composite or composition are required to be electrically insulated. Specifically, the electronically insulating layer can include one or more catalyst composites or compositions and a second ionomer; each of the one or more catalyst composites or compositions can include catalyst particles and a first ionomer coated on all or a portion of a surface of the catalyst particles, and the second ionomer can include a polymer matrix in which the catalyst composites are dispersed.

As used herein, the term "electron insulating layer" refers to a layer or film having significantly reduced electron conductivity such that charges (e.g., electrons) cannot be freely transferred and no or little current is generated even under an applied electric field. For example, the electron insulating layer can have an electron conductivity that is less than the electron conductivity of distilled water, e.g., less than about 5x10^{- 6}S/m, less than about 10^-6S/m, less than about 10^-7S/m, or less than about 10^-8S/m。

The ion exchange layers may suitably comprise a porous reinforcement layer, a first ion exchange layer disposed on a first surface of the reinforcement layer, and a second ion exchange layer disposed on a second surface of the reinforcement layer.

The first surface and the second surface refer to the two surfaces of a single planar structure (e.g., film or layer) facing in opposite directions. The ion exchange layer may comprise an ion exchange material. Preferably, the ion exchange material of the ion exchange layer may be a second ionomer.

The catalyst particles may suitably comprise a metal catalyst and a carbon support, for example, the metal catalyst may be supported on the carbon support.

The metal catalyst may suitably comprise platinum (Pt).

The first ionomer may be the same as the second ionomer. Alternatively, the first ionomer and the second ionomer may differ, for example, in molecular weight, substituents, or other structure. In exemplary embodiments, the first ionomer may include a polymeric material having shorter side chain groups than the second ionomer.

At least one of the first ionomer and the second ionomer may suitably comprise perfluorosulphonic acid (PFSA). Preferably, both the first ionomer and the second ionomer may suitably comprise perfluorosulfonic acid (PFSA).

The electronically insulating layer may suitably comprise the catalyst particles in an amount of from about 0.5 wt% to 5 wt%, based on the total weight of the electronically insulating layer.

In another aspect, a membrane-electrode assembly is provided that includes an electrolyte membrane and a pair of electrodes disposed on two surfaces (e.g., a first surface and a second surface) of the electrolyte membrane.

In still another aspect, a method of preparing an electrolyte membrane of a membrane-electrode assembly is provided. The method can include preparing a first blend by dispersing catalyst particles into a first ionomer solution; drying the first admixture to obtain a catalyst composite; preparing a second blend by dispersing the catalyst composite into a second ionomer solution; and applying the second admixture onto the ion exchange layer and drying the second admixture to form the electron insulating layer.

The method may further include heat treating the electron insulating layer.

The mixture with dispersed catalyst particles may be dried at a temperature of about 25 c to 160 c.

The mixture in which the catalyst composite is dispersed may be applied to the ion exchange layer and may be dried at a temperature of about 25 to 100 ℃ to form the electron insulating layer.

The electron insulating layer may be heat-treated at a temperature of about 160 c to 200 c.

There is further provided a fuel cell comprising a membrane-electrode assembly as described herein.

Other aspects of the invention are discussed below.

Drawings

The above and other features of this invention will be described in detail below with reference to certain exemplary embodiments thereof as illustrated in the accompanying drawings, which are given by way of illustration only, and thus are not limiting of the invention, wherein:

fig. 1 illustrates an exemplary membrane-electrode assembly in cross-section according to an exemplary embodiment of the present invention;

FIG. 2 illustrates an exemplary electrolyte membrane in cross-section according to an embodiment of the invention;

FIG. 3 illustrates, in cross-section, an exemplary catalyst composite according to an embodiment of the invention;

FIG. 4 illustrates an exemplary electrolyte membrane in cross-section according to an embodiment of the invention; and

fig. 5 illustrates an exemplary method of manufacturing an exemplary electrolyte membrane of a membrane-electrode assembly according to an exemplary embodiment of the present invention.

It is to be understood that the appended drawings are not necessarily to scale, showing somewhat simplified depictions of various preferred features illustrative of the basic principles of the invention. The specific design features of the invention disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

In the drawings, like or equivalent elements of the present invention are designated by reference numerals throughout the several views of the drawings.

Detailed Description

The above objects, and other objects, features and advantages will be clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to these embodiments, and will be embodied in various forms. The embodiments are proposed only to provide a full and complete understanding of the disclosure and to fully inform those skilled in the art of the technical idea of the present invention.

Like reference numerals refer to like elements throughout the description of the figures. In the drawings, the size of structures is exaggerated for clarity. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, the corresponding elements should not be construed as limited by these terms, which are used only to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, within the scope defined by the present invention. The singular is intended to include the plural unless the context clearly dictates otherwise.

It will be further understood that the terms "comprises," "comprising," "includes" and "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. In addition, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. It will also be understood that when an element such as a layer, film, region, or substrate is referred to as being "under" another element, it can be directly under the other element or intervening elements may also be present.

Unless the context clearly dictates otherwise, all numbers, numbers and/or expressions referring to ingredients, reaction conditions, polymer compositions and amounts of mixtures used in the specification are approximate values, which reflect the various uncertainties inherently occurring in measurements other than those obtained when such numbers are obtained. For this reason, it is to be understood that in all instances, the term "about" shall modify all numerical values, numbers and/or expressions. The term "about" as used herein is understood to be within the ordinary tolerance in the art, e.g., within 2 mean standard deviations, unless otherwise indicated or clearly differentiated from the context. "about" can be understood as being within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the stated value. All numerical values provided herein are modified by the term "about" unless the context clearly dictates otherwise.

In addition, unless otherwise limited, when numerical ranges are disclosed in the specification, the ranges are continuous and include all numbers from the minimum to the maximum (including the maximum within the range). Further, unless otherwise defined, when a range refers to an integer, it includes all integers from the minimum to the maximum (including the maximum within the range).

Fig. 1 shows a cross-sectional view of an exemplary membrane-electrode assembly according to an exemplary embodiment of the present invention. As shown in fig. 1, the membrane-electrode assembly may include an electrolyte membrane 1 and a pair of electrodes 2 formed on both opposite surfaces of the electrolyte membrane 1. Here, the "pair of electrodes" refers to an anode and a cathode arranged on two opposite surfaces (e.g., a first surface and a second surface) of the electrolyte membrane.

Fig. 2 shows a cross-sectional view of an exemplary electrolyte membrane 1 according to an exemplary embodiment of the invention. As shown in fig. 2, the electrolyte membrane 1 may include an ion exchange layer 10 and an electron insulating layer 20 disposed on the ion exchange layer 10.

The electron insulating layer 20 may include a catalyst composite 21 and a second ionomer 22, which second ionomer 22 may be a polymer matrix in which the catalyst composite 21 is dispersed. For example, the electron insulating layer 20 may be provided to the cathode of one of the electrodes 2.

The ion exchange layer 10 included in the electrolyte membrane 1 according to the exemplary embodiment of the present invention may be configured in the form of a single membrane made of an ion exchange material. The ion exchange layer 10 may further comprise an antioxidant.

The ion exchange material may be the same material as the second ionomer 22.

Although there is no particular limitation on the ion exchange material, the ion exchange material may suitably include perfluorosulfonic acid (PFSA). For example, the ion exchange material may include perfluorosulfonic acid, or the ion exchange material may be perfluorosulfonic acid.

Fig. 3 shows a cross-sectional view of an exemplary catalyst composite 21. As shown in fig. 3, the catalyst composite 21 may include catalyst particles 211 and a first ionomer 212 coated on the entire or part of the surface of the catalyst particles 211. Specifically, in catalyst composite 21, first ionomer 212 may be coated on the entire surface of catalyst particles 211. However, the present invention is not limited thereto.

The catalyst particles 211 may suitably include: a metal catalyst supported on a carbon support. The metal catalyst may suitably comprise one or more noble metal elements, which may be selected from platinum (Pt), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru) and combinations thereof. The metal catalyst may specifically include platinum (Pt).

When the exchange of hydrogen and oxygen occurs, the catalyst particles directly convert the hydrogen into water to inhibit the formation of radicals in the electrolyte membrane. Therefore, the chemical durability of the electrolyte membrane can be significantly improved.

However, hydrogen may not be converted into water by the catalyst particles, but may pass between adjacent catalyst particles, and may form radicals at the interface between the cathode 2 and the electrolyte membrane. The radicals may accelerate chemical degradation of the second ionomer 22 of the electron insulating layer 20, whereby the catalyst particles 211 in an electron insulating state are exposed, so that their functions may be lost. According to various exemplary embodiments of the present invention, the first ionomer 212 may be coated on the entire or part of the surface of the catalyst particles 211. The electron-insulating state of the catalyst particles 211 can be maintained even if the chemical degradation of the electron insulating layer 20 is caused to some extent by the radicals. Therefore, the electrolyte membrane according to the exemplary embodiment of the invention may maintain improved durability for a long time.

First ionomer 212 may be the same polymeric material as second ionomer 22 or may be a polymeric material having shorter side chain groups than second ionomer 22. Preferably, a polymeric material having shorter side chain groups than second ionomer 22 may be used as first ionomer 212 because a polymeric material having short side chain groups may be more resistant to chemical degradation.

Each of the first ionomer 212 and the second ionomer 22 may suitably comprise perfluorosulfonic acid (PFSA). Specifically, the first ionomer 212 may be a short side chain PFSA.

The electron insulating layer 20 may suitably include the catalyst particles 211 in an amount of about 0.5 wt% to 5 wt%, based on the total weight of the electron insulating layer 20. When the content of the catalyst particles 211 is less than about 0.5 wt%, the effect of suppressing the generation of radicals may not be significant. When the content of the catalyst particles 211 is greater than about 5 wt%, the ionic conductivity in the electrolyte membrane 1 or the mechanical integrity of the electrolyte membrane 1 may be reduced, and thus the durability of the electrolyte membrane 1 may be reduced.

Fig. 4 shows a cross-sectional view of an exemplary electrolyte membrane 1 according to an exemplary embodiment of the invention. As shown in fig. 4, the electrolyte membrane 1 may include an ion exchange layer 10 and an electron insulating layer 20 disposed on the ion exchange layer 10. An electron insulating layer 20 may be provided on one of the electrodes 2, in particular the cathode. Alternatively, the electron insulating layer 20 may be provided to one or both of the cathode and the anode.

For example, the ion exchange layer 10 may include a reinforcing layer 11 for increasing the mechanical rigidity thereof, and the reinforcing layer 11 may be impregnated with an ion exchange material such that the ion exchange layer 10 has a three-layer structure.

Specifically, the ion exchange layer 10 may include a reinforcing layer 11, a first ion exchange layer 12 provided on one surface of the reinforcing layer 11, and a second ion exchange layer 13 provided on the other surface of the reinforcing layer 11.

The reinforcing layer 11 may suitably include a porous membrane made of expanded polytetrafluoroethylene (e-PTFE) and may have a large number of pores.

The electron insulating layer 20 included in the electrolyte membrane 1 according to the exemplary embodiment of the present invention may be the same as previously described, and a description thereof will be omitted.

Fig. 5 shows a flowchart of an exemplary method of manufacturing an exemplary electrolyte membrane of an exemplary membrane-electrode assembly, according to an exemplary embodiment of the present invention. As shown in fig. 5, the method of preparing the electrolyte membrane may include: for example, a step of preparing a first admixture by introducing and dispersing catalyst particles into the first ionomer solution (S10); a step (S20) of drying the first admixture in which the catalyst particles are dispersed to obtain a catalyst composite; for example, a step of preparing a second blend by introducing and dispersing the catalyst composite into the second ionomer solution (S30); a step of applying the second admixture in which the catalyst composite is dispersed on the ion exchange layer and drying to form an electron insulating layer (S40), and optionally, a step of heat-treating the electron insulating layer (S50).

The step of preparing the first admixture by introducing and dispersing the catalyst particles into the first ionomer solution (S10) may be carried out by a suitable device under appropriately set conditions so that the catalyst particles are uniformly dispersed in the first ionomer solution.

The first ionomer solution may be obtained by dispersing the first ionomer in a solution such as water or alcohol, or may be in the form of an emulsion of the first ionomer.

Subsequently, the mixture in which the catalyst particles are dispersed may be dried to obtain a catalyst composite (S20). The mixture may be dried above about 25 ℃ and below the temperature at which the first ionomer loses side chains. The temperature at which the first ionomer loses side chains varies depending on the type of first ionomer. For example, when the first ionomer is perfluorosulfonic acid (PFSA), the mixture can be dried at a temperature of about 25 ℃ to 160 ℃.

The catalyst composite has been previously described, and thus further description thereof will be omitted.

The step of preparing the second admixture by introducing and dispersing the catalyst composite into the second ionomer solution (S30) may be carried out by a suitable device under appropriately set conditions so that the catalyst composite is uniformly dispersed in the second ionomer solution.

The second ionomer solution may be obtained by dispersing the second ionomer in a solution such as water or alcohol, or may be in the form of an emulsion of the second ionomer.

Subsequently, the second admixture in which the catalyst composite is dispersed may be applied on the ion exchange layer and dried to form an electron insulation layer (S40). The amount of the second admixture applied is not particularly limited, but may be appropriately adjusted according to the desired thickness of the electronic insulating layer. Additionally, the mixture may be dried at a temperature of about 25 ℃ to 100 ℃.

In the step of heat-treating the electronic insulating layer (S50), the electronic insulating layer may be heat-treated at a temperature of about 160 ℃ to 200 ℃. The step of forming the electronic insulating layer (S40) and the step of heat-treating the electronic insulating layer (S50) may be performed continuously or discontinuously.

According to various exemplary embodiments of the present invention, the electrolyte membrane may include an electron insulating layer capable of blocking air to prevent hydrogen peroxide formed due to the exchange of hydrogen from being decomposed into radicals, so that the chemical durability of the electrolyte membrane may be greatly improved.

Further, the catalyst particles included in the electron insulating layer may be coated with an ionomer, so that the catalyst particles may be maintained in an electron insulating state even when the electrolyte membrane is chemically degraded, whereby the chemical durability of the electrolyte membrane may be further greatly improved.

The effects of the present invention are not limited to those described above. It is to be understood that the effects of the present invention include all the effects that can be inferred from the foregoing description of the present invention.

The present invention has been described in detail with reference to exemplary embodiments thereof. It would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.