KR102059965B1 - Composite polymer electrolyte membrane for fuel cell, and method of manufacturing the same - Google Patents

Abstract

Impregnating the hydrogen ion conductive polymer electrolyte solution into the porous support; And applying hot air to two or more directions with respect to the upper surface of the porous support impregnated with the hydrogen ion conductive polymer electrolyte solution.

Description

Composite Polymer Electrolyte Membrane for Fuel Cell and Manufacturing Method Thereof {COMPOSITE POLYMER ELECTROLYTE MEMBRANE FOR FUEL CELL, AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a composite polymer electrolyte membrane for a fuel cell and a method of manufacturing the same. More specifically, the present invention relates to a composite polymer electrolyte membrane for a polymer electrolyte fuel cell (PEMFC) and a method of manufacturing the same.

BACKGROUND OF THE INVENTION Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are a type of fuel cell that is in the spotlight as a next-generation energy source, and a fuel cell using a polymer membrane having hydrogen ion exchange characteristics as an electrolyte. The polymer electrolyte fuel cell (PEMFC) includes a polymer electrolyte membrane having characteristics such as high hydrogen ion conductivity, low electron conductivity and gas permeability, high mechanical strength and dimensional stability, as well as electrical insulation, for initial performance and long term performance. It is required to do

Meanwhile, as a polymer electrolyte membrane for a polymer electrolyte fuel cell (PEMFC), a pure perfluorinated sulfonated polymer electrolyte membrane such as a Nafion monolayer manufactured by DuPont is currently commercialized and is most widely used. However, pure perfluorinated sulfonated polymer electrolyte membranes have high characteristics such as high unit cost and low mechanical and morphological stability despite excellent chemical resistance, oxidation resistance, and ionic conductivity. There is an increasing demand for new polymer electrolyte membranes that are both conventional and economically viable.

As one solution to this, research on the reinforced composite polymer electrolyte membrane in which the porous support is impregnated with an electrolyte solution is actively conducted. This can be thinned by using the porous support as a material having excellent mechanical strength, thereby reducing the resistance due to the thickness of the fuel cell when operating the fuel cell, and ensuring the mechanical and morphological stability, and can be implemented to have the excellent characteristics as described above. Therefore, it is expected to solve various problems of the existing polymer electrolyte membranes and has recently been raised as one of the most important technical issues for commercializing polymer electrolyte fuel cells such as fuel cell vehicles.

However, according to the researches of the present inventors, since it is very difficult to uniformly and tightly impregnate the polymer electrolyte inside the porous support pores, it may be practically limited to implement the composite polymer electrolyte membrane.

Korean Unexamined Patent No. 10-2013-0078153 Korea Patent Registration No. 10-0746339 Korean Patent Application No. 10-2008-0015338 European Application Patent No. 2848620

Xing, Danmin, et al. "Properties and morphology of Nafion / polytetrafluoroethylene composite membrane fabricated by a solution-spray process." International Journal of Hydrogen Energy 38.20 (2013): 8400-8408.

It is an object of the present invention to prepare a reinforced composite thin film electrolyte including a porous support, not only has high hydrogen ion exchange characteristics, but also has low gas permeability, excellent mechanical strength to thickness, and is economical and free from physical damage. A composite polymer electrolyte membrane for a fuel cell and a method of manufacturing the same are provided.

An exemplary embodiment of the present invention includes the steps of impregnating a hydrogen ion conductive polymer electrolyte solution into a porous support; And applying hot air to two or more directions with respect to the upper surface of the porous support impregnated with the hydrogen ion conductive polymer electrolyte solution.

An exemplary embodiment of the present invention provides a composite polymer electrolyte membrane for a fuel cell manufactured according to the above-described manufacturing method.

Exemplary embodiments of the present invention provide a membrane electrode assembly including the above-described composite polymer electrolyte membrane for a fuel cell.

An exemplary embodiment of the present invention provides a fuel cell comprising the membrane electrode assembly described above.

The composite polymer electrolyte membrane for a fuel cell according to the present invention may be prepared in the form of a thin film composite including a porous support through a quenching process and a hot air process.

Particularly, after the impregnation process, hot air is applied in two or more directions with respect to the upper surface of the porous support impregnated with the hydrogen ion conductive polymer electrolyte solution, thereby hydrogen-conducting the inside of the porous support having pores in the form of a three-dimensional network structure. The polymer electrolyte can be filled more uniformly and densely, ie substantially completely. Accordingly, the composite polymer electrolyte membrane may be substantially free of residual pores or voids that are not sufficiently filled with a hydrogen ion conductive polymer electrolyte, and may not cause physical and / or chemical damage or deterioration. As a result, the composite polymer electrolyte membrane may have improved hydrogen ion exchange characteristics, electron conductivity, mechanical strength and dimensional stability, which is higher than or equal to that of the conventional polymer electrolyte membrane for fuel cells, and may have particularly low gas permeability.

In addition, the composite polymer electrolyte membrane can be manufactured using a minimum of a hydrogen ion conductive electrolyte such as an expensive perfluorinated sulfonated ionomer, and thus may have an additional advantage in terms of price competitiveness compared to a conventional polymer electrolyte membrane for fuel cells.

Therefore, through the composite polymer electrolyte membrane for a fuel cell, it is possible to easily implement a membrane electrode assembly having excellent performance, and a fuel cell including the same.

1 is a schematic diagram illustrating a hot air process of a multi-process support for manufacturing a composite polymer electrolyte membrane according to exemplary embodiments of the present invention.
FIG. 2 is a view illustrating the preparation of a composite polymer electrolyte membrane, in which an electrolyte (perfluorinated sulfonated ionomer) is filled in a porous support pore before (a) and hot air process conditions (b) perpendicular to a top surface of the porous support (c) horizontal ( d) SEM photographs showing the cross-sections of the vertical + horizontal cases.
FIG. 3 is a view illustrating a porous perfluorine-based support (a) and hot air processing conditions prior to filling (b) vertical (c) horizontal (d) vertical + horizontal with respect to the upper surface of the porous support prior to filling SEM images showing the upper surfaces are compared.
4 is a graph showing the performance of the unit cell including the composite polymer electrolyte membrane according to Example 1 and Comparative Examples 1 to 4.
FIG. 5 is a graph illustrating electrochemical characteristics of a unit cell including the polymer electrolyte membrane according to Example 1 and Comparative Examples 1 to 4, measured by cyclic voltammetry (CV).
6 is a hydrogen crossover current density (H ₂ crossover current density) of a unit cell including the polymer electrolyte membrane according to Example 1 and Comparative Examples 1 to 4, measured by Linear Sweep Voltammetry (LSV) Is a graph showing comparison.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention disclosed in the text are only illustrated for illustrative purposes, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention may be modified in various ways and may have various forms, and the embodiments are not intended to limit the present invention to the specific disclosed forms, and all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. It will be understood to include.

As used herein, the "top surface" of the porous support means the top surface of the widest surface of the porous support.

As used herein, “complexed” or “complexed” is more effective because the perfluorinated sulfonated polymer electrolyte (ionomer), a polymer electrolyte having hydrogen ion conductivity, is physically and / or chemically bonded to the porous fluorine-based polymer support. It means to be combined to have a function.

In this specification means a hydrogen permeable phenomenon occurs going beyond the cathode (cathode) electrode the "cross-over hydrogen (H ₂ crossover)" is hydrogen, did not react in the anode (anode) electrode through the polymer electrolyte membrane. This hydrogen crossover phenomenon, that is, undesired gas diffusion from the anode electrode to the cathode electrode is known as a major cause of perfluorinated electrolyte membrane deterioration. Generally, the thinner the electrolyte membrane or the polymer electrolyte is impregnated into the support. If not completely, it can happen easily. In the present invention, in order to confirm the occurrence of hydrogen crossover phenomenon and hydrogen crossover current density, 0V to 0.6V (vs. anode) using linear scanning potential method (LSV) while supplying hydrogen to the anode electrode and nitrogen to the cathode electrode. ), The current of the battery was measured.

As used herein, the term "hot air process" refers to a process of applying hot air in two or more directions with respect to the upper surface of the porous support.

Composite Polymer Electrolyte Membrane for Fuel Cell

The composite polymer electrolyte membrane of the present invention is an electrolyte membrane for a fuel cell, specifically, an electrolyte membrane capable of forming a membrane electrode assembly (MEA) of a polymer electrolyte fuel cell (PEMFC). The composite polymer electrolyte membrane includes a porous support and a hydrogen ion conductive polymer electrolyte. At this time, the pores of the porous support may be uniformly and densely filled with the hydrogen ion conductive polymer electrolyte, that is, substantially completely filled, so that there may be substantially no residual pores or voids in the composite polymer electrolyte membrane. Thus, the composite of a polymer electrolyte membrane based hydrogen permeation current density brought about 2.0 mA / cm ² of hydrogen crossover current density (H ₂ crossover current density) or less, is extremely excellent in gas permeability.

The porous support may have a plurality of pores in a three-dimensional mesh structure therein, thereby contributing to improving mechanical strength and morphological stability of the composite polymer electrolyte membrane. As such a porous support, for example, a porous fluorine-based polymer support such as a porous polytetrafluoroethylene (PTFE) support can be used. The porous fluorine-based polymer support is chemically stable due to the strong bonding force between carbon and fluorine and the screening effect characteristic of the fluorine atom, and excellent in mechanical properties and chemical affinity with the electrolyte, and thus may be usefully used in the present invention.

In exemplary embodiments, the porous support may be treated with acetone, methanol, ethanol, propanol or hydrogen peroxide. Porous fluorine-based polymer supports, such as porous polytetrafluoroethylene (PTFE) supports, have hydrophobicity, and are therefore more familiar with air than the hydrophilic hydrogen-ion conductive polymer electrolytes and thus have low wettability. Therefore, despite the advantages described above, it may be difficult to implement a composite polymer electrolyte membrane having a uniform and dense internal structure without using residual pores or voids.

However, by treatment with acetone, methanol, ethanol, propanol or hydrogen peroxide, the porous fluorine-based polymer support may have improved wettability and may further contain no impurities on the interior and / or surface.

The improved wettability of the porous fluorine-based polymer support is advantageous for filling the pores of the porous fluorine-based polymer support more uniformly and densely, ie substantially completely with the hydrogen ion conductive electrolyte. Accordingly, the composite polymer electrolyte membrane may have a high membrane density, and as a result, may have an improved mechanical strength. In addition, since the space between the hydrophilic ion domains is narrowed therein, the composite polymer electrolyte membrane may have increased ion conductivity and dimensional stability.

The hydrogen ion conductive polymer electrolyte may be, for example, a perfluorinated sulfonic acid ionomer (PFSA ionomer) such as a Nafion ionomer. The perfluorinated sulfonated ionomer (PFSA) may have a high chemical affinity for the porous fluorine-based polymer support because it has the same structure as the main chain of polytetrafluoroethylene (PTFE). Therefore, the perfluorinated sulfonated ionomer (PFSA ionomer) and the porous fluorine-based polymer support may be strongly bonded to each other, and the composite may finally contribute to improved stability of the composite polymer electrolyte membrane.

The composite polymer electrolyte membrane may sufficiently fill all the pores of the porous fluorine-based polymer support so that the composite polymer electrolyte membrane may be implemented in a thin film form without deterioration characteristics such as low hydrogen ion exchange characteristics and high gas permeability due to electrolyte shortage. It may include perfluorinated sulfonated ionomer in an appropriate content. On the other hand, although the performance of the composite polymer electrolyte membrane may be improved in proportion to the content of the perfluorinated sulfonated ionomer, the production cost may be increased when an excessive amount of the expensive perfluorinated sulfonated ionomer is included, so that it is an effective composite of electrolyte content and thickness. It may be difficult to implement a polymer electrolyte membrane.

In particular, according to the present invention, according to the method for producing a composite polymer electrolyte membrane for a fuel cell to be described later, after the impregnation process, the hot air process is carried out in two or more directions, preferably by applying hot air at 0 to 20 degrees to the polymer in the porous support By adjusting the arrangement of the chain in the horizontal direction, it is possible to obtain the effect of lowering the gas permeability of the resulting electrolyte membrane, the hot air is applied at 70 to 90 degrees by combining the hydrogen ion conductive polymer electrolyte and the porous support to combine the mechanical durability An improved electrolyte membrane can be obtained.

The composite polymer electrolyte membrane may have, for example, a thickness of about 5 μm to less than 25 μm. Existing polymer electrolyte membranes for fuel cells, for example, polymer electrolyte membranes made of pure perfluorinated sulfonated polymer electrolytes, such as Nafion electrolyte membranes, generally have a thick thickness of about 25 μm or more for enhanced mechanical properties. However, since the thickness of the electrolyte membrane increases not only the mechanical properties but also the resistance of the membrane, the thicker the electrolyte membrane, the lower the ionic conductivity of the electrolyte membrane. On the other hand, since the composite polymer electrolyte membrane of the present invention has a high membrane density and mechanical properties as described above, for example, even if the thickness of about 5μm to less than 25μm, specifically about 20μm relatively thin thickness for conventional fuel cells It may have substantially the same or higher ionic conductivity and mechanical properties than the polymer electrolyte membranes. That is, the composite polymer electrolyte membrane may have very good hydrogen ion exchange characteristics and mechanical strength to thickness.

As described above, the composite polymer electrolyte membrane of the present invention is implemented in the form of a homogeneous composite thin film including a porous support, which not only has excellent mechanical strength to thickness, but also has high hydrogen ion exchange characteristics and low electronic conductivity, and particularly has improved gas permeability. Has In addition, the composite polymer electrolyte membrane contains a relatively low content of a high cost perfluorinated sulfonated ionomer (eg, Nafion ionomer), but has excellent characteristics as described above or above the conventional polymer electrolyte membrane. It may have additional advantages in terms of price competitiveness.

Therefore, through this, it is possible to easily implement a membrane electrode assembly (MEA) of excellent performance and a fuel cell including the same. In particular, since the composite polymer electrolyte membrane has high mechanical strength, the composite polymer electrolyte membrane can be easily manufactured without damaging the electrolyte membrane.

Manufacturing method of composite polymer electrolyte membrane for fuel cell

The composite polymer electrolyte membrane of the present invention, with reference to Figure 1, the step of impregnating a hydrogen ion conductive polymer electrolyte solution in a porous support; And applying hot air to two or more directions with respect to the upper surface of the porous support impregnated with the hydrogen ion conductive polymer electrolyte solution.

Although not particularly shown, the porous support as described above may be treated with acetone, methanol, ethanol, propanol or hydrogen peroxide.

In exemplary embodiments, the porous fluorine-based polymer support may be washed with acetone, methanol, ethanol, propanol or hydrogen peroxide as the porous support. Through this, the porous fluorine-based polymer support may remove impurities from its inside and / or surface, and may have improved wettability.

Although not specifically illustrated, the hydrogen-ion conductive polymer electrolyte solution may be impregnated into the porous support through a spray or decal process. Preferably, the spray ion process may spray the hydrogen ion conductive electrolyte solution onto the porous support treated with acetone, methanol, ethanol, propanol or hydrogen peroxide. The hydrogen ion conductive electrolyte solution is a solution containing the same hydrogen ion conductive electrolyte as described above, for example, a perfluorinated sulfonated ionomer (PFSA ionomer) solution can be used. Through the spraying process, a plurality of pores distributed in a three-dimensional network structure inside the porous support may be at least partially filled with the hydrogen ion conductive electrolyte solution (perfluorinated sulfonated ionomer solution).

In an exemplary embodiment, the spraying process, the treated porous fluorine-based polymer support is fixed flat to a mold made in a uniform shape, the spray gun (spray gun) connected to the gas cylinder at a certain distance from the This can be done by spraying a perfluorinated sulfonated ionomer solution.

At this time, the perfluorinated sulfonated ionomer solution may be injected at a flow rate of about 2 to 6 ml / min under a pressure of about 2 to 4 bar so that the porous fluorine-based support can be evenly sprayed without damage.

In particular, in one embodiment, the perfluorinated sulfonated ionomer solution may be injected in the direction of gravity. In this case, the blowing force and gravity in the vertical direction of the perfluorinated sulfonated ionomer solution to be sprayed together act in the same direction, the porous fluorine-based polymer than when the perfluorinated sulfonated ionomer solution is injected in a direction other than the gravity direction The pore interior of the support can be filled more effectively.

Meanwhile, in exemplary embodiments, when the spray process is performed, the perfluorinated sulfonated ionomer solution may be about 1 to about 20 wt% based on the total weight of the perfluorinated sulfonated ionomer solution in consideration of dispersibility. It may include a perfluorinated sulfonated ionomer. When the content of the perfluorinated sulfonated ionomer in the perfluorinated sulfonated ionomer solution exceeds about 15 wt%, the viscosity of the perfluorinated sulfonated ionomer solution is gradually increased, and the perfluorinated sulfonated ionomer content is about 20 wt%. In case of exceeding, the perfluorinated sulfonated ionomer solution may not be evenly sprayed due to the high viscosity.

Then, the non-dried porous fluorine-based polymer support filled with the perfluorinated sulfonated ionomer solution was fixed to the glass frame, and as shown in FIG. 1, two kinds of the porous support was impregnated with the hydrogen ion conductive polymer electrolyte solution. By applying hot air in the above direction, the hydrogen ion conductive polymer electrolyte solution sprayed on the porous support may be dried. Accordingly, the solvent in the solution may be volatilized and only the hydrogen ion conductive polymer electrolyte as described above, for example, a perfluorinated sulfonated ionomer, may remain inside the porous support pores.

In exemplary embodiments, the hot air process may be performed in which the pores therein are at least partially filled with the perfluorinated sulfonated ionomer solution by impregnation of the perfluorinated sulfonated ionomer solution into the porous fluorine-based polymer support by a spray impregnation process. It may be performed on the porous fluorine-based polymer support.

In exemplary embodiments, the direction may be between 0 and 90 degrees with respect to the top surface of the porous support, preferably in the directions of 0 to 20 degrees and 70 to 90 degrees, respectively.

When hot air is applied in a direction of 0 to 20 degrees with respect to the upper surface of the porous support, after the impregnation process, since the arrangement of the polymer chains in the porous support is horizontally filled to uniformly fill the electrolyte therein, gas permeation can be minimized.

When hot air is applied in a direction of 70 to 90 degrees with respect to the upper surface of the porous support, the drying may be performed simultaneously or sequentially with the 0 to 20 degrees direction drying to make the impregnation uniform and at the same time increase the drying speed. In particular, the hydrophobic groups of the hydrophobic porous fluorine-based polymer support and the perfluorinated sulfonated ionomer are adhered to each other, and adhesiveness is generated. The ionomer is flexibly bonded to the porous fluorine-based support. In addition, the empty space is bonded to the hydrophilic groups of the perfluorinated ionomer, and the strength is improved while applying the heat of the glass transition temperature.

Therefore, when hot air is applied in two or more directions with respect to the upper surface of the porous support, both of gas permeation and good performance can be obtained. In addition, through the above method, the pores of the porous support may be completely filled with a hydrogen ion conductive polymer electrolyte.

In exemplary embodiments, the hot air may be applied one or more times in two or more directions with respect to the top surface of the porous support.

In exemplary embodiments, the hot air may be applied at a distance of about 30 cm to 70 cm from the top and side surfaces of the porous support. When the distance is less than 30 cm, the porous support may be deformed due to overheating, and when the distance is greater than 70 cm, the effect of uniformly filling the electrolyte by the hot air may be insignificant, and drying may not be complete.

In exemplary embodiments, the temperature of the hot air may be 100 to 200 ° C. When the temperature of the hot air is less than 100 ° C., drying may not be sufficient, and it may be difficult to remove residual pores not filled with the hydrogen ion conductive polymer electrolyte.

In exemplary embodiments, the wind speed of the hot air may be 10 to 15L / min, it may be added uniformly. When the wind speed is less than 10L / min, it is difficult to horizontally arrange the chain of the polymer chain on the porous support, and the drying rate may be slow, and when it is more than 15L / min, it may be difficult to remove residual pores not filled with the hydrogen ion conductive polymer electrolyte. .

In exemplary embodiments, the hot air may be applied for 10 to 50 seconds. If the time is less than 10 seconds, the drying may not be sufficient, if over 50 seconds the overheating may deform the porous support, the overall process speed may be slow.

In example embodiments, the method may further include drying the porous support to which the hot air is applied in an oven. Further drying in the oven after the hot air process can minimize the possibility of residual pores.

The temperature in the oven may be 100 to 200 ℃. If the temperature is less than 100 ℃ may not be enough to dry, if it is above 200 ℃ may cause chemical damage or deterioration.
The drying may proceed for 20 to 50 minutes.

In the manufacture of a polymer electrolyte membrane for fuel cells, in particular, a composite polymer electrolyte membrane, conventionally, a dipping process, a casting process, a coating process, and the like are used. However, these processes can be difficult to fill the pores of the porous support, especially the porous support including a hydrophobic polytetrafluoroethylene with a hydrophilic polymer electrolyte (hydrogen ion conductive polymer electrolyte). If the pores of the porous support are not sufficiently filled and residual pores are present in the composite polymer electrolyte membrane, fuel permeates through the membrane to deteriorate the performance of the membrane, and radicals are released during long-term operation of the fuel cell including the composite polymer electrolyte membrane. Can form and act as a cause of deterioration of the film.

Moreover, the dipping process, casting process, coating process, etc. are generally required to be repeated several times, which may cause complexity in manufacturing, and nevertheless polymer electrolyte There may be residual pores that are not sufficiently filled, so that after treatment, additional workup processes such as hot pressing processes should be performed.

However, the composite polymer electrolyte membrane according to the present invention may be prepared in the form of a uniform composite thin film including a porous support through a method of sequentially performing the pretreatment process, the electrolyte impregnation process, the hot air process, and the oven drying process as described above. .

In particular, as described above, by performing the hot air process after the impregnation process at two or more angles, the inside of the porous support pores distributed in a three-dimensional network structure is more uniform and tighter, that is, substantially completely, with a hydrogen ion conductive polymer electrolyte. I can fill it.

Therefore, the composite polymer electrolyte membrane may be substantially free of residual pores or voids that are not sufficiently filled with a hydrogen ion conductive polymer electrolyte, and may not cause physical and / or chemical damage or deterioration. As a result, the composite polymer electrolyte membrane may have improved hydrogen ion exchange characteristics, electron conductivity, mechanical strength and dimensional stability, which is higher than or equal to that of the conventional polymer electrolyte membrane for fuel cells, and may have particularly low gas permeability.

In addition, the composite polymer electrolyte membrane can be manufactured using a minimum of a hydrogen ion conductive electrolyte such as an expensive perfluorinated sulfonated ionomer, and thus may have an additional advantage in terms of price competitiveness compared to a conventional polymer electrolyte membrane for fuel cells.

Even when a small amount of hydrogen ion conductive electrolyte is used, it is easy to impregnate the inside of the porous support by the pressure of the hot air in the 70-90 degree direction with respect to the upper surface of the porous support during the hot air process, and the hot air is applied in the 0-20 degree direction. It is possible to impregnate a large area by the, because the hot air in the 0 to 20 degrees direction makes the arrangement of the polymer chain in the porous support to have a high conductivity.

Meanwhile, only the polymer electrolyte membrane for a fuel cell and a method of manufacturing the same have been described so far, but the membrane electrode assembly composed of the composite polymer electrolyte membrane as described above, and all fuel cells including the same, for example, a polymer electrolyte fuel cell ( It will be apparent to those skilled in the art that PEMFC) is also within the scope of the present invention.

The present invention is described in more detail through the following implementation. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.

[ Example  Hot air is applied in the vertical-horizontal direction with respect to the upper surface of the 1-porous support body]

Porous polytetrafluoroethylene supports (GORE PTFE, GMM-405) were washed with acetone (Sigma Aldrich) to remove impurities and improve wettability.

Acetone-washed porous polytetrafluoroethylene scaffold is fixed flat and firmly with a teflon tape to a mold made to have a uniform shape, and then a spray gun connected to a nitrogen gas cylinder (EWATA spray gun, W-300-101G). Nafion resin solution (Nafion perfluorinated resin solution 5wt%, Sigma Aldrich) was evenly sprayed on the porous polytetrafluoroethylene support at a certain distance. At this time, the Nafion resin solution was injected at a flow rate of 2 to 6 ml / min under 2 to 4 bar pressure in the direction of gravity.

After fixing the porous polytetrafluoroethylene support filled with Nafion ionomer to the glass frame, the pores inside were perpendicular to the upper surface of the support for 10 seconds at a temperature of 150 ° C. and a wind speed of 13 L at a distance of 30 cm-70 cm. And horizontally for 20 seconds. This process was repeated three times so that the composite electrolyte membrane was evenly subjected to heat and pressure.

After the composite electrolyte membrane was prepared using the hot air drying, the mixture was dried at 150 ° C. for 30 minutes in an oven.

Finally, a 20 μm-thick composite polymer electrolyte membrane was manufactured through the above-described processes, and then a membrane electrode assembly and a single cell including the same were manufactured by performing the following processes.

A catalyst solution was prepared by dissolving 46.5 wt% Pt / C catalyst in Nafion ionomer and isopropyl alcohol (Sigma Aldrich) solvent. After spreading and fixing the composite polymer electrolyte membrane, the catalyst solution was sprayed onto the composite polymer electrolyte membrane using a spray gun for catalyst injection. At this time, the catalyst loading amount of the anode (anode) was 0.2 mg _pt / cm ² and the catalyst loading amount of the cathode (cathode) was 0.4 mg _pt / cm ² , the active area (active area) was 1 cm ² . Thereafter, the solvent is naturally dried until all of the solvent in the catalyst solution evaporates, and thus, a membrane electrode assembly including an anode electrode and a cathode electrode disposed to face each other, and a composite polymer electrolyte membrane positioned therebetween. electrode assembly, MEA).

The membrane electrode assembly (MEA) is sequentially tightened at 30 In * lb, 50 In * lb, 70 In * lb by using a Teflon gasket and a carbon bipolar plate. A single cell was produced.

[ Comparative example  Hot air is applied in a direction perpendicular to the upper surface of the 1-porous support body]

A composite polymer electrolyte membrane, a membrane electrode assembly, and a unit cell were manufactured in the same manner as in Example 1, except that hot air was applied only in the vertical direction with respect to the upper surface of the porous support.

[ Comparative example  Hot air is applied only horizontally with respect to the upper surface of the 2-porous support body]

A composite polymer electrolyte membrane, a membrane electrode assembly, and a unit cell were manufactured in the same manner as in Example 1, except that hot air was applied only in the horizontal direction with respect to the upper surface of the porous support.

[ Comparative example  3-commercial electrolyte membrane]

A membrane electrode assembly (MEA) and a unit cell including the same were fabricated using a Nafion 211 membrane having a thickness of 25 μm.

[ Comparative example  4-electrolyte membrane without hot air drying]

A porous polytetrafluoroethylene support prepared by spraying a Nafion resin solution was prepared in the same manner as in Example 1. The support was first dried in an oven at 60 ° C. for 1 hour and secondly dried for 12 hours in a vacuum oven at the same temperature to volatilize all the solvents in the sprayed Nafion resin solution. Accordingly, the porous polytetrafluoroethylene support was impregnated with 0.097 g of Nafion ionomer, and the thickness of the porous polytetrafluoroethylene support in which the pores therein were filled with the Nafion ionomer was 20 μm.

In addition, a membrane electrode assembly (MEA) and a unit cell including the same were manufactured using the prepared composite polymer electrolyte membrane.

Experimental Example : Evaluation of Microstructure of Composite Polymer Electrolyte Membrane

In order to evaluate the microstructure of the composite polymer electrolyte membrane, the surface and the cross section of the porous support and the prepared composite polymer electrolyte membrane (the cross section perpendicular to the upper surface of the porous support (the surface in contact with the sprayed Nafion ionomer solution)) are scanned. Observations and comparisons were made using a scanning electron microscope (SEM). The result is as shown in Figs.

Specifically, (a) is a porous perfluorine-based support shown in Figure 2, (d) is a composite polymer electrolyte membrane prepared according to Example 1, (b) and (c) is prepared according to Comparative Examples 1 and 2 SEM photographs showing cross sections of the composite polymer electrolyte membrane, respectively.

(A) is a porous perfluorine-based support shown in Figure 3, (d) is a composite polymer electrolyte membrane prepared according to Example 1, (b) and (c) is a composite polymer electrolyte prepared according to Comparative Examples 1 and 2 SEM images showing the top surface of the film, respectively.

Referring to FIG. 2, in the case of the porous support of FIG. 2 (d), a large difference in morphology was not observed on the surface of the prepared composite polymer electrolyte membrane, but as in FIG. 2 (b), the adhesion state between the porous support and the ionomer is good. Compared to 2 (c), it was shown that no residual pores existed and the impregnation in the support was better.

Referring to FIG. 3, in the case of (b) in which hot air is applied only in the vertical direction of the upper surface of the porous support, the polymer does not appear to be arranged in the horizontal direction, and in the case of (c) in which hot air is applied only in the horizontal direction, Compared to the drying process, the bond between the porous perfluorine-based support and Nafion ionomer appeared weak. However, in the case of (d) according to Example 1, the Nafion ionomer was well bonded to the support by the vertical force, so that the bond between the resulting grains between the porous fluorine-based support was also well and the polymer was arranged in the horizontal direction. In general, the horizontal alignment was observed, and as a result of the support, the gap between the grains was thicker.

Therefore, in the case of the electrolyte membrane prepared according to Example 1, the bond between the porous perfluorine-based support and the Nafion ionomer by hot air drying in the vertical direction, and also the bond between the porous perfluorine-based support and the Nafion ionomer are good. The durability and performance could be expected to be excellent, and the polymer array is also arranged in the horizontal direction by hot air drying in the horizontal direction can be expected to improve the gas permeability.

Experimental Example Performance Evaluation of Composite Polymer Electrolyte Membrane Ⅰ

In order to evaluate the performance of the composite polymer electrolyte membrane, single cells (sigle cells) including the composite polymer electrolyte membranes prepared according to Example 1 and Comparative Examples 1 to 4 were operated to measure a current-voltage (IV) change, The change in power density was measured. At this time, the anode was supplied with hydrogen at a flow rate of 200 cc / min, and the air was supplied at a flow rate of 600 cc / min to the cathode. The results are as shown in Figure 4 and Table 1. Specifically, FIG. 4 illustrates a current-voltage (I-V) change and a power density change. On the other hand, the performance of the composite polymer electrolyte membrane in the current-voltage (I-V) curve was evaluated based on the current density value at OCV (open circuit voltage) and 0.6V.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Open circuit voltage (OCV) 0.995 0.998 0.977 0.978 0.976 A / cm ² @ 0.6V (IV curve) 1.4 1.4 1.1 0.7 1.5 Maximum power density (W / cm ² ) 1.011 1.011 0.991 0.548 1.053 mA / cm ² @ 0.4V (LSV) 2.29 1.82 2.15 3.58 1.20 Thickness (μm) 15 20 25 20 20 Impregnation rate 75 73 100 75 75

4 and Table 1, the performance of the Example was better than Comparative Example 3, the cell according to Example 1 showed a significantly better performance than the cell according to Comparative Example 4 (see Figure 4 ).

In particular, power density is expressed as the product of current density and voltage, and the performance of the cell is evaluated based on the maximum power density. Higher means that the performance of the unit cell is excellent. Referring to FIG. 4, the power density of Example 1 is much higher than that of Comparative Example 4 as well as Comparative Example 3.

Since the composite polymer electrolyte membranes according to Example 1 and Comparative Example 4 both contain Nafion ionomer in the same content and have similar thicknesses, the performance characteristic difference between the single cells as described above is different in the electrolyte membrane morphology characteristics depending on the manufacturing process. It can be seen that.

Experimental Example : Performance Evaluation of Composite Polymer Electrolyte Membrane II

In order to evaluate the performance of the composite polymer electrolyte membrane, the cyclic voltammetry (CV) and linear scanning potential method (Linear Sweep) to the unit cells including the composite polymer electrolyte membrane prepared according to Example 1 and Comparative Examples 1 to 4 Voltammetry, LSV) was performed. At this time, the anode was supplied with hydrogen at a flow rate of 200 cc / min, and the cathode was supplied with nitrogen at a flow rate of 600 cc / min. The results are shown in FIGS. 5, 6 and Table 1.

Specifically, FIG. 5 is a graph illustrating comparison of electrochemical characteristics of the corresponding cells measured using the cyclic voltammetry (CV), and FIG. 6 shows the corresponding cells measured using the linear scanning potential method (LSV). It is a graph comparing the hydrogen crossover current density (H ₂ crossover current density).

Referring to FIG. 5, the electrochemically active region of the catalyst was confirmed by observing the adsorption / desorption reaction occurring between hydrogen supplied during operation of the unit cell and the platinum electrode of the unit cell through cyclic voltammetry (CV). The graph shows the fifth measurement value after measuring a total of five times at a potential scanning speed of 50 mV / s from 0.05 V to 1.2 V to ensure reproducibility. The electrochemically active surface was evaluated based on hydrogen desorption peaks observed from 0.05V to 0.35V. As a result of comparing the platinum active areas in the cyclic current voltage (CV) graphs of the cells according to Example 1 and Comparative Examples 1 to 4, the electrochemically active regions of the platinum catalysts in Example 1 and Comparative Examples 1 to 4 were A match was found. Through this, it can be seen that the performance of the unit cells according to Example 1 and Comparative Examples 1 to 4 is due to the characteristics of the electrolyte membrane included in the cells, not the catalyst.

On the other hand, linear scanning potential (LSV) was performed at a potential scan rate of 2 mV / s in the voltage range of 0.0V to 0.6V, through which hydrogen, which did not react at the anode, was transmitted to the cathode and reacted with the cathode electrode layer. the hydrogen crossover current density (H ₂ crossover current density) was measured. At this time, the hydrogen crossover current density was evaluated based on a battery voltage of 0.4V (see Table 1), and the higher the hydrogen crossover current density, the more easily hydrogen gas can permeate through the electrolyte membrane (the electrolyte membrane has a high gas permeability). Means).

6, the hydrogen crossover current density in the unit cell was 0.4V is shown a land 2.15mA / cm ² according to the comparative example 3, in the case of Comparative Example 4 exhibited a 3.58mA / cm ^2. In addition, the hydrogen crossover current densities of Comparative Examples 1 and 2 are 2.29 mA / cm ² and 1.82 mA / cm ² , respectively, indicating that residual pores exist in an environment without a hot air process in two or more directions.

However, the unit cell according to Example 1 exhibited a hydrogen crossover current density of 1.20 mA / cm ² , which is clearly different from the unit cell according to Comparative Example 4. This is because there are substantially no residual pores on the surface and inside of the composite polymer electrolyte membrane according to the embodiments prepared through the hot air process in the horizontal direction, and the Nafion ionomer array is also present in the horizontal direction so that the composite polymer electrolyte is present. This means that hydrogen gas permeation into the membrane hardly occurs. In addition, the Nafion ionomer was well bonded to the support by the vertical force through the hot air process in the vertical direction.

These results are consistent with the results of the microstructure evaluation of the composite polymer electrolyte membrane, which was examined through the results shown in FIG. 3.

Claims (25)

Impregnating the hydrogen ion conductive polymer electrolyte solution into the porous support; And
And applying hot air to two or more directions with respect to an upper surface of the porous support impregnated with the hydrogen ion conductive polymer electrolyte solution.
The method of claim 1,
The direction is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that 0 to 90 degrees with respect to the upper surface of the porous support.
The method of claim 1,
The hot air is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that in the direction of 0 to 20 degrees and 70 to 90 degrees with respect to the upper surface of the porous support.
The method of claim 1,
Through the method, the pores of the porous support is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that completely filled with a hydrogen ion conductive polymer electrolyte.
The method of claim 1,
Method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that the hot air is applied simultaneously or sequentially.
The method of claim 1,
The method of manufacturing a composite polymer electrolyte membrane for a fuel cell, characterized in that the hot air is applied at least once to the upper surface of the porous support in at least two directions.
The method of claim 1,
The hot air is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that the addition of 30 to 70cm away from the porous support.
The method of claim 1,
The temperature of the hot air is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that 100 to 200 ℃.
The method of claim 1,
The wind speed of the hot air is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that 10 to 15L / min.
The method of claim 1,
The hot air is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that applied for 10 seconds to 50 seconds.
The method of claim 1,
The porous support is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that the porous fluorine-based polymer support.
The method of claim 1,
The hydrogen ion conductive polymer electrolyte solution is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that the perfluorinated sulfonic acid ionomer (PFSA ionomer) solution.
The method of claim 12,
The perfluorinated sulfonated ionomer solution, based on the total weight of the perfluorinated sulfonated ionomer solution, a method for producing a composite polymer electrolyte membrane for a fuel cell comprising 1 to 20 wt% perfluorinated sulfonated ionomer.
The method of claim 1,
In the impregnating step, the hydrogen ion conductive polymer electrolyte solution is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that the injection at a flow rate of 2 to 6 ml / min under a pressure of 2 to 4 bar.
The method of claim 1,
The hydrogen ion conductive polymer electrolyte solution is a method of manufacturing a composite polymer electrolyte membrane for a fuel cell, characterized in that the injection in the direction of gravity.
The method of claim 1,
Prior to impregnating the porous support,
And treating the porous support with acetone, methanol, ethanol, propanol or hydrogen peroxide.
The method of claim 1,
Drying the porous support to which the hot air is applied in an oven; Method of producing a composite polymer electrolyte membrane for a fuel cell further comprising.
The method of claim 17,
The temperature in the oven is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that 100 to 200 ℃.
The method of claim 17,
The drying is a method for producing a composite polymer electrolyte membrane for a fuel cell, characterized in that 20 to 50 minutes.
20. A composite polymer electrolyte membrane for a fuel cell prepared according to the method according to any one of claims 1 to 19.
The method of claim 20,
The hydrogen crossover current density of the polymer electrolyte membrane (H ₂ crossover current density) is a composite polymer electrolyte membrane for a fuel cell, characterized in that less than 2.0 mA / cm ² .
The method of claim 20,
The hydrogen ion conductive polymer electrolyte and the porous support are combined and complexed, and the polymer chain in the porous support has a composite polymer electrolyte membrane for a fuel cell, characterized in that horizontal.
The method of claim 20,
The composite polymer electrolyte membrane is a composite polymer electrolyte membrane for a fuel cell having a thickness of less than 5μm to 25μm.
A membrane electrode assembly comprising a composite polymer electrolyte membrane for a fuel cell according to claim 23.
A fuel cell comprising the membrane electrode assembly according to claim 24.

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