KR20200081030A - Polymer electrolyte membrane that suppresses side reactions caused by gas crossover phenomenon and manufacturing method of the same - Google Patents

Abstract

The present invention relates to an electrolyte membrane with suppressed side reactions due to gas crossover. More specifically, provided is a method for realizing cost reduction by differently controlling the catalyst content of a catalyst layer formed on an electrolyte membrane for each zone. In addition, provided is an electrolyte membrane capable of preventing crossover due to hydrogen and oxygen gas flowing in while a fuel cell is driven.

Description

{Polymer electrolyte membrane that suppresses side reactions caused by gas crossover phenomenon and manufacturing method of the same}

The present invention relates to an electrolyte membrane that suppresses side reactions due to a gas crossover phenomenon, and more particularly, to an electrolyte membrane capable of preventing a crossover phenomenon caused by hydrogen and oxygen gas flowing during operation of a fuel cell.

The electrolyte membrane fuel cell generates electricity and water through an electrochemical reaction in which a proton generated by oxidation of hydrogen at a hydrogen electrode passes through the electrolyte membrane and reacts with reduced oxygen ions at the oxygen electrode. However, at the same time, a gas crossover phenomenon occurs in which the supply gas passes through the electrolyte membrane in a molecular state, and in the case of hydrogen, it is supplied at a high concentration and the molecular weight is small, so crossover occurs easily. This is a phenomenon that occurs when the electrolyte membrane does not completely function as a gas barrier. When this phenomenon increases, an open circuit voltage (OCV) decreases and fuel efficiency decreases as much as fuel consumed without participating in an electrochemical reaction. For example, hydrogen that has passed through the electrolyte membrane at the hydrogen electrode meets the oxygen of the oxygen electrode and becomes H ₂ O, H ₂ O ₂ , HO ₂ or the like by catalysis, and is discharged without reacting. A mixed problem is formed with the reduction reaction of oxygen, which is the reaction, and serious problems occur that the H ₂ O ₂ or oxygen radicals attack the electrolyte membrane and the electrode to degrade them to generate pinholes.

Korean Registered Patent No. 10-1669236 relates to a solid polymer electrolyte and a method of manufacturing the same, and a method of improving the life of a fuel cell by providing a catalyst layer containing a catalyst on the surface of the electrolyte membrane to prevent hydrogen crossover is provided. have. However, since the content of the catalyst used is excessively increased compared to the conventional fuel cell, there is a concern that high cost is generated, and there is a problem that it is practically difficult to commercialize.

Korean Registered Patent No. 10-1669236

An object of the present invention is to provide an electrolyte membrane of a fuel cell and a fuel cell using the same, which can realize cost savings by increasing the efficiency of the cell and reducing the content of expensive noble metal catalysts.

An object of the present invention is to provide an electrolyte membrane and a method of manufacturing the same, which can prevent side reactions due to a gas crossover phenomenon that may occur when the fuel cell is driven.

The object of the present invention is not limited to the object mentioned above. The object of the present invention will be more apparent from the following description, and will be realized by means described in the claims and combinations thereof.

According to the invention, the substrate; It includes a catalyst layer on both sides of the substrate, the catalyst layer is a first catalyst layer coated on one surface of the substrate; And a second catalyst layer coated on the other side of the substrate, wherein the catalyst layer includes a catalyst, and the catalyst layer suppresses side reactions due to gas crossover, characterized in that the content of the catalyst is different in the CD direction or the MD direction. An electrolyte membrane for a fuel cell is provided.

The substrate may be expanded polytetrafluoroethylene (ePTFE) or expanded polytetrafluoroethylene (ePTFE) in which pores are impregnated with ionomers.

The catalyst is platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), copper ( Cu), silver (Ag), gold (Au), periphery (Sn), titanium (Ti), chromium (Cr), and combinations thereof.

The catalyst may be supported on a carbon carrier.

The catalyst layer further includes an ionomer, and the ionomer is a fluorine-based polymer, a benzimidazole-based polymer, a polyimide-based polymer, a polyetherimide-based polymer, a polyfetylene sulfide-based polymer, a polysulfone-based polymer, and a polyethersulfone-based polymer. , Polyether ketone-based polymer, polyether-ether ketone-based polymer, polyphenylquinoxaline-based polymer, polystyrene-based polymer, and combinations thereof.

The content of the catalyst in the catalyst layer may be less than 3% by weight of the ionomer.

The catalyst layer may have a reduced content of catalyst in the CD direction or MD direction.

The thickness of the catalyst layer may be constant in the CD direction and the MD direction.

The thickness of the catalyst layer may be 1 to 10㎛.

The catalyst layer forms a stage in the CD direction or the MD direction, and the ?t amount of the catalyst can be decreased according to the stage.

According to the present invention, the hydrogen-side separator comprising a hydrogen inlet and a hydrogen outlet; An oxygen electrode side separator plate which is joined to the hydrogen electrode side separator plate and includes an oxygen inlet and an oxygen outlet; And a membrane-electrode assembly interposed between the hydrogen electrode side separator plate and the oxygen electrode side separator plate, wherein the membrane electrode assembly comprises an oxygen electrode; Hydrogen pole; And an electrolyte membrane interposed between the oxygen electrode and the hydrogen electrode, wherein a first catalyst layer including a catalyst is coated on one surface of the electrolyte membrane, and a second catalyst layer including a catalyst is coated on the other surface of the electrolyte membrane, The oxygen electrode is provided on the first catalyst layer of the electrolyte membrane, the hydrogen electrode is provided on the second catalyst layer of the electrolyte membrane, the oxygen electrode faces the separator on the oxygen electrode side, and the hydrogen electrode is the hydrogen electrode Facing the side separation plate, the first catalyst layer is a gas crossover phenomenon characterized in that the content of the catalyst is different in the CD direction or MD direction, the second catalyst layer is different in the content of the catalyst in the CD direction or MD direction Provided is a fuel cell that suppresses side reactions.

According to the present invention, comprising a catalyst, an ionomer and a solvent, and preparing a catalyst slurry of two or more oxygen-side catalysts having different catalyst contents; Preparing two or more hydrogen electrode side catalyst slurries containing catalysts, ionomers, and solvents and having different catalyst contents; Coating the first catalyst layer by sequentially applying along the CD direction on release paper in the order of decreasing catalyst content in the catalyst slurry on the oxygen side; Depositing an electrolyte membrane on the first catalyst layer; And coating a second catalyst layer on the electrolyte membrane in the order of decreasing catalyst content in the order of decreasing the amount of catalyst in the cathode electrode catalyst layer in the CD direction, and including the thickness of the first catalyst layer and the second catalyst layer. Provided is a method for manufacturing an electrolyte membrane for a fuel cell that suppresses side reactions due to a gas crossover phenomenon characterized by being constant along the CD direction and the MD direction.

The solvent may be one selected from the group consisting of ethanol, isopropyl alcohol, propanol, ethoxyethanol, butanol, ethylene glycol, distilled water, amyl alcohol and combinations thereof.

There is no oxygen-side catalyst slurry in which the catalyst content is 0% among the two or more oxygen-side catalyst slurries prepared in the step of preparing the oxygen-side catalyst slurry, and the two or more hydrogen-side catalysts prepared in the step of preparing the hydrogen-side catalyst slurry In the slurry, there may be no catalyst slurry on the anode side where the catalyst content is 0%.

In the step of coating the sieve 1 catalyst layer and the step of coating the sieve 2 catalyst layer, a catalyst slurry on the oxygen electrode side and a catalyst slurry on the hydrogen electrode side may be applied through a spray method.

In the step of coating the first catalyst layer, two or more oxygen-catalyst catalyst slurries having different catalyst contents are respectively applied through an applicator prepared according to the number of the oxygen-catalyst catalyst slurry, and the catalyst content is different in the step of coating the second catalyst layer. The above hydrogen electrode side catalyst slurries can be applied to each of the hydrogen electrode side catalyst slurries through an applicator prepared according to the number.

In the step of coating the first catalyst layer, the step of laminating the electrolyte membrane, and the step of coating the second catalyst layer, the method may further include drying after each step.

According to the present invention, while improving the efficiency of the fuel cell while providing a method to reduce the amount of the catalyst introduced into the electrolyte membrane has the effect of increasing the economic efficiency through cost reduction.

According to the present invention, it has an effect that the durability of the fuel cell can be improved by effectively controlling the gas crossover phenomenon that may occur depending on the driving of the fuel cell.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be deduced from the following description.

Figure 1 shows the structure of the (1 unit cell) fuel cell of the present invention.
Figure 2 shows the stage of the catalyst layer included in the electrolyte membrane.
3 schematically shows a cross-section of the bonding structure between the electrolyte membrane and the electrode.
Figure 4 shows the structure of the (1 unit cell) fuel cell of the present invention and the structure of the catalyst layer formed on the electrolyte membrane.
5 schematically shows the electrolyte membrane configuration and the movement path of hydrogen and oxygen related to the crossover phenomenon of hydrogen and oxygen.
Figure 6 briefly shows the position of the hydrogen inlet and hydrogen outlet and the catalyst layer relationship of the electrolyte membrane.
7 shows a flow chart related to the method for manufacturing an electrolyte membrane of the present invention.
8 briefly shows a coating step related to the preparation of an electrolyte membrane.

The above objects, other objects, features and advantages of the present invention will be readily understood through the following preferred embodiments related to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete and that the spirit of the present invention is sufficiently conveyed to those skilled in the art.

In describing each drawing, similar reference numerals are used for similar components. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than the actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this specification, the terms "include" or "have" are intended to indicate the presence of features, numbers, steps, actions, components, parts or combinations thereof described in the specification, one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, actions, components, parts or combinations thereof are not excluded in advance. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case of being "just above" the other part but also another part in the middle. Conversely, when a portion of a layer, film, region, plate, or the like is said to be “under” another portion, this includes not only the case “underneath” another portion, but also another portion in the middle.

Unless otherwise specified, all numbers, values, and/or expressions expressing amounts of ingredients, reaction conditions, polymer compositions, and blends used herein are those numbers that occur in obtaining these values, among other things. As these are approximations that reflect the various uncertainties of the measurement, it should be understood that in all cases they are modified by the term "about". In addition, when numerical ranges are disclosed in this description, these ranges are continuous, and include all values from the minimum value in this range to the maximum value including the maximum value, unless otherwise indicated. Further, when such a range refers to an integer, all integers including the minimum value to the maximum value including the maximum value are included unless otherwise indicated.

In the present specification, when a range is described for a variable, it will be understood that the variable includes all values within the stated range including the described endpoints of the range. For example, a range of “5 to 10” includes values of 5, 6, 7, 8, 9, and 10, as well as any subrange of 6 to 10, 7 to 10, 6 to 9, 7 to 9, and the like. It will be understood to include, and include any value between integers pertinent to the stated range of ranges such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also, for example, the range of “10% to 30%” is 10% to 15%, 12% to 10%, 11%, 12%, 13%, etc. and all integers including up to 30% It will be understood that it includes any subranges such as 18%, 20% to 30%, etc., and includes any value between valid integers within the scope of the stated range, such as 10.5%, 15.5%, 25.5%, and the like.

The present invention relates to an electrolyte membrane for a fuel cell capable of preventing a gas crossover phenomenon and a method for manufacturing the same.

In FIG. 1, the configuration of the fuel cell is briefly described. Referring to this, the configuration of the fuel cell to which the electrolyte membrane of the present invention can be applied will be briefly described, and the electrolyte membrane of the present invention and its manufacturing method will be described.

In the fuel cell to which the electrolyte membrane of the present invention is applied, catalyst layers (first catalyst layer and second catalyst layer) are coated on both sides around the electrolyte membrane, and oxygen and hydrogen electrodes are provided on both sides of the electrolyte membrane, respectively. A gas diffusion layer is provided on the oxygen electrode and the hydrogen electrode, an oxygen electrode side separator plate is provided on the gas diffusion layer located on the oxygen electrode, and a hydrogen electrode side separator plate is provided on the gas diffusion layer located on the hydrogen electrode to include a bonded structure. .

At this time, the oxygen-side separator is bonded to the direction in which the first catalyst layer (hereinafter, for convenience, the catalyst layer coated in the direction of the oxygen-side separator is referred to as a first catalyst layer) is located, and the hydrogen-side separator is an electrolyte. The second catalyst layer (hereinafter referred to as a catalyst layer coated in the direction of the hydrogen electrode side separator plate for convenience) is bonded to the direction in which the membrane is centered.

The seven layers are stacked to form one unit cell.

The oxygen pole-side separator includes an oxygen inlet, which is a passage for introducing external oxygen (oxygen gas) into the unit cell, and an oxygen outlet, which is a passage for flowing out of the unit cell, and the hydrogen cathode-side separator is external hydrogen (hydrogen Gas) includes a hydrogen inlet that is a passage for flowing into the unit cell and a hydrogen outlet for a passage that flows out of the unit cell.

In the driving of the unit cell, hydrogen supplied through the hydrogen inlet included in the hydrogen-side separator is decomposed into hydrogen ions and electrons in the hydrogen electrode through a gas diffusion layer, and the hydrogen ions move to the oxygen electrode through the electrolyte membrane. . At this time, the generated electrons generate current through an external circuit, and hydrogen ions at the oxygen electrode and oxygen supplied through the oxygen inlet included in the electron and oxygen electrode side separator plates combine to generate water. More specifically, the decomposition of the hydrogen proceeds in the catalyst contained in the hydrogen electrode, and the bonding proceeds in the catalyst contained in the oxygen electrode.

Among the hydrogen and oxygen supplied through the hydrogen inlet and the oxygen inlet, gases that do not participate in the reaction are discharged through the hydrogen outlet and the oxygen outlet included in the oxygen-side separator and the hydrogen-side separator. Typically, the hydrogen inlet and the hydrogen outlet are located diagonally in the separator on the hydrogen side, and the oxygen inlet and the oxygen outlet are also located in the diagonal direction in the separator on the oxygen side, but in the present invention, this structure is for convenience. This is mainly explained, but is not limited thereto.

The present invention relates to an electrolyte membrane and a method of manufacturing the unit cell formed by stacking the seven layers.

The following electrolyte membrane, electrode and electrolyte membrane manufacturing method will be described separately.

Electrolyte membrane

The electrolyte membrane of the present invention includes a substrate; It includes a catalyst layer on both sides of the substrate, the catalyst layer is a first catalyst layer coated on one surface of the substrate; And a second catalyst layer coated on the other surface of the substrate, wherein the catalyst layer includes a catalyst.

The base material may be any material that is commonly applied to the electrolyte membrane of a fuel cell. For example, the expanded polytetrafluoroethylene (ePTFE) or ionomer, which has been widely used to date, is expanded polytetrafluoro impregnated into pores. Ethylene (ePTFE). At this time, the ionomer impregnated into the pores of the substrate is sufficient as a polymer resin capable of conducting hydrogen ions, for example, fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polypentylene sulfide System polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone polymer, polyether-ether ketone polymer, polyphenylquinoxaline polymer, polystyrene polymer, and combinations thereof. have.

The catalyst layer further includes an ionomer, and the ionomer is sufficient as a polymer resin having hydrogen ion conductivity, for example, a fluorine-based polymer, a benzimidazole-based polymer, a polyimide-based polymer, a polyetherimide-based polymer, and polyfetylene sulfide. -Based polymer, polysulfone-based polymer, polyethersulfone-based polymer, polyether-ketone-based polymer, polyether-ether-ketone-based polymer, polyphenylquinoxaline-based polymer, polystyrene-based polymer, and combinations thereof. have.

The catalyst included in the catalyst layer is platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) ), copper (Cu), silver (Ag), gold (Au), periphery (Sn), titanium (Ti), chromium (Cr), and a combination thereof, and the catalyst is supported if necessary. Carbon can be used.

The total content of the catalyst contained in the catalyst layer of the present invention is less than 3% by weight of the total ionomer content. It is preferably less than 1% by weight, and more preferably less than 0.5% by weight. At this time, when the total content of the catalyst is 3% by weight or more of the ionomer, the insulating property of the catalyst by the ionomer is deteriorated, and the effect of reducing the cost by reducing the content of the catalyst is not obtained.

In the present invention, the catalyst layer is characterized in that the content of the catalyst is different in the CD direction or the MD direction. Specifically, in the catalyst layer, the content of the catalyst is reduced along the CD direction (cross direction), or the content of the catalyst is reduced along the MD direction (machine direction). As such, when the content of the catalyst is gradually decreased on the first catalyst layer, when the unit cell is manufactured in the region with the highest catalyst content, the hydrogen inlet of the separator on the hydrogen side is located on the back of the electrolyte membrane on which the first catalyst layer is formed ( Specifically, the catalyst content is high in the portion of the first catalyst layer closest to the region where the hydrogen inlet is located in the hydrogen-side separator, and when the catalyst gradually decreases in content on the second catalyst layer, the most catalyst content In this high region, when the unit cell is manufactured, the hydrogen outlet portion where hydrogen is discharged from the hydrogen side separator plate is located (specifically, the catalyst content in the portion of the second catalyst layer closest to the region where the hydrogen outlet portion of the hydrogen electrode side separator plate is located) This is high.) The description related to the above will be described again later when dealing with the configuration of the fuel cell.

The fact that the content of the catalyst decreases on the catalyst layer more specifically forms the stage in the CD direction or MD direction (in the present invention, this is used in the same sense as the zone or region), and the content of the catalyst depends on the stage. It can be said that it will decrease.

2 shows the stage of the catalyst layer. In FIG. 2, a catalyst layer is formed in one direction (horizontal in the drawing, referred to as the CD direction in the present invention), but this is only for convenience of description and does not exclude the vertical direction or the MD direction. . Only two or more stages of the present invention can be applied, and in the case of a single single case, the characteristics of the present invention are excluded to prevent problems caused by a gas crossover phenomenon, but it is impossible to obtain an effect of reducing the amount of catalyst.

In the case of the second stage in FIG. 2, the content of the catalyst in one of the two stages is smaller than the other stage, and in the case of the third stage, the left stage (can be arbitrarily selected according to the structure of the unit cell. It does not exclude that the content decreases.) From the middle stage to the right stage, the content of the catalyst may decrease in turn. In the case of the fourth stage, as in the case of the third stage, the content of the catalyst is gradually decreased for each stage.

The stage of the present invention is not limited to the second to fourth stages, and may be increased more than this depending on the purpose and the size of the unit cell. However, the stage having no catalyst content among the stages formed in the catalyst layer is excluded because it is against the feature of the present invention that effectively suppresses side reactions of gases passing through the electrolyte membrane through the crossover phenomenon.

The thickness of the catalyst layer of the present invention is characterized by being constant in the CD direction and the MD direction (machine direction). That is, even if the stage with the highest content of the catalyst and the stage with the lowest content of the catalyst are formed in one catalyst layer, since the ionomer meets the shortage of the catalyst, the total solids content in all stages becomes the same, and consequently in all stages. The thickness of the catalyst layer becomes constant.

The thickness of the first catalyst layer is 1 to 10 μm, and the thickness of the second catalyst layer is also 1 to 10 μm.

The catalyst contained in the electrolyte membrane of the present invention is characterized in that the content of the catalyst contained in the hydrogen electrode and the oxygen electrode as electrodes is less. This is because the catalyst itself contained in the electrolyte membrane is not intended to serve as an electrode, but is configured for the purpose of removing and reacting with hydrogen or oxygen that has been crossover.

The first coating layer and the second coating layer formed on both sides of the electrode and the electrolyte membrane of the present invention are characterized by being insulated.

3 schematically shows the bonding structure between the electrolyte membrane and the electrode. Referring to this, the catalyst included in the second catalyst layer is surrounded by an ionomer, thereby confirming a structure in which an insulating region is formed. This is essential, and when the catalysts contained in the electrolyte membrane cannot be insulated from the electrodes, they are not freed from electrons flowing in and out of the external wires, so they are not freed from the oxidation and reduction reactions occurring at the electrodes and eventually block the gas generated due to the crossover. And failing to perform the natural function of reacting.

electrode

The electrode of the present invention is provided on both sides of the electrolyte membrane, specifically, a hydrogen electrode reacting with hydrogen introduced from the outside is provided facing the second catalyst layer of the electrolyte membrane, and an oxygen electrode reacting with oxygen introduced from the outside of the electrolyte membrane It is provided facing the first catalyst layer.

The electrode is a substrate; And a catalyst layer coated on the substrate. Specifically, the substrate faces the gas diffusion layer, and the catalyst layer is positioned facing the catalyst layer of the electrolyte membrane.

The substrate is expanded polytetrafluoroethylene (ePTFE).

The catalyst layer is a catalyst; And ionomers.

The ionomer is sufficient if a polymer resin having hydrogen ion conductivity is sufficient, for example, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyfetylene sulfide polymer, a polysulfone polymer, poly It may be one selected from the group consisting of ethersulfone-based polymers, polyether-ketone-based polymers, polyether-ether-ketone-based polymers, polyphenylquinoxaline-based polymers, polystyrene-based polymers, and combinations thereof.

The catalyst is platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), copper ( Cu), silver (Ag), gold (Au), circumferential speed (Sn), titanium (Ti), chromium (Cr), and one selected from the group consisting of a combination thereof. Can.

The catalyst content of the catalyst layer included in the oxygen electrode or hydrogen electrode of the present invention is 20% to 80% by weight of the ionomer content.

Fuel cell

The fuel cell of the present invention includes a hydrogen-side separation plate including a hydrogen inlet and a hydrogen outlet; An oxygen electrode side separator plate which is joined to the hydrogen electrode side separator plate and includes an oxygen inlet and an oxygen outlet; And a membrane-electrode assembly interposed between the hydrogen electrode side separator plate and the oxygen electrode side separator plate, and including the membrane electrode assembly and the oxygen electrode side separator plate and the membrane electrode assembly and the hydrogen electrode side separator plate. It further includes a gas diffusion layer interposed between each.

The gas diffusion layer is porous in order to diffuse the external gas to the reaction region of the electrode, and can be used without particular limitation as long as it is a kind capable of performing a function capable of supporting the electrode. For example, carbon paper or carbon cloth including carbon may be used.

The membrane-electrode assembly includes an oxygen electrode; Hydrogen pole; And an electrolyte membrane interposed between the oxygen electrode and the hydrogen electrode.

One side of the electrolyte membrane includes a first catalyst layer, the other side of the electrolyte membrane includes a second catalyst layer, the oxygen electrode is provided on the first catalyst layer of the electrolyte membrane, and the hydrogen electrode is on the second catalyst layer of the electrolyte membrane. Is provided in, the oxygen electrode faces the separator on the oxygen pole side, the hydrogen electrode faces the separator on the hydrogen electrode side, the first catalyst layer has a different content of the catalyst in the CD direction or MD direction, the The second catalyst layer is characterized in that the content of the catalyst is different in the CD direction or the MD direction.

Specifically, the first catalyst layer and the second catalyst layer form a stage in the CD direction or the MD direction. At this time, in the direction in which the hydrogen inlet is located in the hydrogen-side separator, a stage having the highest catalyst content among the first catalyst layers is formed, and in the direction in which the hydrogen outlet is located in the hydrogen-side separator, catalyst in the second catalyst layer It is characterized by the formation of the group with the highest content.

FIG. 4 briefly shows an example of a unit cell structure of the fuel cell of the present invention. (Since the gas diffusion layer, the oxygen electrode, and the hydrogen electrode are unnecessary structures for explaining this feature, they are omitted from FIG. 4 and the description, and are excluded. 4, the first catalyst layer and the second catalyst layer are formed on both sides of the electrolyte membrane. Specifically, the right end of the second catalyst layer is located on the back side of the electrolyte membrane corresponding to the left end of the first catalyst layer, and the left end of the second catalyst layer is located on the back side of the electrolyte membrane corresponding to the right end of the first catalyst layer. do.

When the unit cell structure is joined to the left end of the first catalyst layer, the hydrogen outlet of the hydrogen-side separator is located at the right end of the second catalyst layer corresponding to the left end of the first catalyst layer, and the first catalyst layer When the right end of the unit cell structure is joined, the hydrogen inlet of the hydrogen-side separator is positioned at the left end of the second catalyst layer corresponding to the right end of the first catalyst layer. In this case, the left end of the first catalyst layer has a low content of the catalyst, the right end has a high content of the catalyst, the outer end of the second catalyst layer has a low content of the catalyst, and the right end has a high content of the catalyst.

The unit cell structure, more specifically, the catalyst distribution of the first catalyst layer and the second catalyst layer according to the position of the hydrogen inlet and the hydrogen outlet of the hydrogen-side separator, results in problems caused by hydrogen and oxygen crossover. It can be solved, and this will be described with reference to FIG. 5.

FIG. 5 briefly shows the path of hydrogen and oxygen along with the electrolyte membrane configuration related to the hydrogen and oxygen crossover.

As the unit cell configuration is applied, hydrogen that has passed through the second catalyst layer and the substrate of the electrolyte membrane from the hydrogen inlet region of the hydrogen-side separator (hydrogen inlet region hydrogen flow rate, density, or partial pressure is relatively large) It reacts with oxygen on a catalyst present in a high content in the first catalyst layer to form condensate and prevents it from being passed to the oxygen electrode (not shown).

In the case of the hydrogen outlet region of the hydrogen-side separator, the flow rate of hydrogen is relatively small compared to the hydrogen inlet region, whereby condensed water is locally formed. Due to the locally formed condensate, a region in which hydrogen supply is reduced occurs, and a crossover phenomenon of oxygen is relatively generated on the back side of the electrolyte membrane corresponding to the region. In this case, as the above-described unit cell configuration is applied, the oxygen that has passed through the first catalyst layer and the substrate reacts with hydrogen on a catalyst present in a high content in the second catalyst layer to form condensed water and a hydrogen electrode (not shown) ).

At this time, if there is no catalyst in the first catalyst layer and the second catalyst layer that reacts with the crossover gas on opposite sides of the electrolyte membrane, oxygen and hydrogen meet to form OH radicals to attack the ionomer and electrolyte membranes of the electrodes (oxygen and hydrogen electrodes). Is done. The process of forming the OH radical is as follows.

[Formula 1]

H ₂ + O ₂ → HOOH → HOㆍ+ㆍOH

If the reaction as described above continues, the ionomer layer and the electrolyte membrane of the electrode under attack by OH radicals are deteriorated, adversely affecting the performance of the fuel cell.

As described above, by partially controlling the catalyst contents of the first catalyst layer and the second catalyst layer of the electrolyte membrane, problems caused by a gas crossover phenomenon can be prevented, and a relatively small amount of crossover occurs to require a large catalyst content. It is possible to reduce the catalyst content in an area not being furnaced, thereby realizing cost reduction. The region that does not require much of the catalyst content is the first catalyst layer region (ie, the left end of the first catalyst layer) on the back side of the electrolyte membrane corresponding to the second catalyst layer adjacent to the hydrogen outlet of the hydrogen side separator plate, It is a second catalyst layer region (ie, the left end of the second catalyst layer) adjacent to the hydrogen inlet of the hydrogen-side separator.

The first catalyst layer and the second catalyst layer are composed of two stages, but as described above, this is an example for convenience of description, and the stages may be composed of two or more stages. In addition, in the drawings of the present invention, the oxygen inlet portion is located on the upper side and the oxygen outlet portion is located on the lower side, but this can also be freely set according to the purpose of the design, as is the hydrogen inlet and the hydrogen outlet. As an example of this, FIG. 6 discloses that the positions of the hydrogen inlet and the hydrogen outlet can be adjusted.

Referring to FIG. 6, in the case of the first catalyst layer formed on the surface of the electrolyte membrane on the oxygen electrode side, the hydrogen inlet of the hydrogen-side separator plate located on the rear surface of the electrolyte membrane may be located on the upper side, the middle side, and the lower side. Since it belongs to the left column, the catalyst content in the left column is large and the catalyst content in the right column is relatively small. In addition, in the case of the second catalyst layer, the hydrogen outlet of the hydrogen electrode side separation plate may be located at the upper, middle, and lower sides. Since it belongs to the right stage of the second catalyst layer composed of two stages, the catalyst content in the left stage is large and the right stage is large. The catalyst content of is relatively small. This is because, as described above, the crossover phenomenon of oxygen proceeds better in the region where the hydrogen outlet is formed.

Electrolyte membrane manufacturing method

The electrolyte membrane manufacturing method of the present invention comprises the steps of preparing a catalyst slurry containing two or more oxygen anodes containing catalysts, ionomers, and solvents and having different catalyst contents; Preparing two or more hydrogen electrode side catalyst slurries containing catalysts, ionomers, and solvents and having different catalyst contents; Coating the first catalyst layer by sequentially applying along the CD direction on release paper in the order of decreasing catalyst content in the catalyst slurry on the oxygen side; Laminating a substrate on the first coating layer; And coating the second catalyst layer by sequentially applying along the CD direction on the substrate in the order in which the catalyst content in the cathode catalyst slurry is decreased.

7 shows a flow chart related to the method of manufacturing the electrolyte membrane of the present invention. Each step will be described with reference to FIG. 7. However, parts overlapping with the features of the present invention already described in the electrolyte membrane and fuel cell configurations are partially omitted.

Oxygen side catalyst slurry preparation step

It is a step of preparing two or more oxygen-catalyst catalyst slurries containing catalysts, ionomers and solvents and having different catalyst contents. The oxygen electrode side catalyst slurry is a slurry that is applied to release paper to form a first catalyst layer.

The catalyst and the ionomer are dispersed by being introduced into the solvent. At this time, the temperature and the mixing environment can be freely controlled so that the dispersion proceeds well, and the method is not particularly limited.

The solvent may be one selected from the group consisting of ethanol, isopropyl alcohol, propanol, ethoxyethanol, butanol, ethylene glycol, distilled water, amyl alcohol and combinations thereof.

The catalyst slurry of two or more oxygen anodes having different catalyst contents is prepared for each number in order to be applied independently according to the number of the catalyst slurry. The prepared two or more oxygen cathode catalyst slurries are characterized by having different catalyst contents. In this case, the catalyst slurry of the oxygen cathode side, in which the catalyst content in the prepared catalyst slurry of the anode electrode becomes 0%, should be excluded. If there is an oxygen cathode catalyst slurry in which the catalyst content in the oxygen anode catalyst slurry is 0%, there is a region that does not react with the supplied oxygen, resulting in a decrease in the efficiency of the fuel cell.

Hydrogen anode catalyst slurry preparation step

It is a step of preparing two or more hydrogen electrode side catalyst slurries containing catalysts, ionomers, and solvents and having different catalyst contents. The catalyst slurry on the cathode side is a slurry that is applied to a substrate to form a second catalyst layer.

The catalyst and the ionomer are dispersed by being introduced into the solvent. At this time, the temperature and the mixing environment can be freely controlled so that the dispersion proceeds well, and the method is not particularly limited.

The solvent may be one selected from the group consisting of ethanol, isopropyl alcohol, propanol, ethoxyethanol, butanol, ethylene glycol, distilled water, amyl alcohol and combinations thereof.

Two or more hydrogen electrode side catalyst slurries having different catalyst contents are prepared for each number to be applied independently according to the number of the catalyst slurries. The prepared two or more hydrogen electrode side catalyst slurry is characterized in that the content of the catalyst is different. At this time, the catalyst slurry in the cathode side, where the catalyst content is 0%, should be excluded in the catalyst slurry in the cathode side. If there is a hydrogen-catalyst catalyst slurry in which the catalyst content is 0% in the hydrogen-catalyst catalyst slurry, a region that does not react with the supplied hydrogen is generated, thereby deteriorating the efficiency of the fuel cell.

First catalyst layer coating step

It is a step of coating the first catalyst layer by applying the prepared catalyst slurry on the anode side to each CD in the CD direction. Specifically, the catalyst electrode slurry prepared for each catalyst content is independently applied along the CD direction on release paper through an applicator prepared according to the number of catalyst catalyst slurry on the oxygen electrode side. It is applied in order to increase or decrease.

Referring to FIG. 6 with respect to the application method, as shown in the first catalyst layer coating step, the oxygen electrode side catalyst slurry is applied in a spray manner by allowing the applicators to be provided in a line along the CD direction on the release paper. It is characterized in that the catalyst content of the catalyst slurry on the oxygen side applied through is gradually increased or decreased for each applicator.

The applicator is sufficient as an applicator conventionally used in the field of fuel cells, and the type is not particularly limited. However, it is preferable that a plurality of applicators can be lined up in a row in the CD direction on release paper and satisfy the condition of being suitable for a continuous process.

When the catalyst slurry on the oxygen electrode side is applied to the release paper in a desired size, the solvent is dried through a hot air drying furnace to form a first catalyst layer.

Substrate lamination step

As a step of laminating a substrate on the prepared first catalyst layer, specifically, a substrate prepared on a first catalyst layer formed by drying on the release paper is formed. In this case, the substrate is dried through a hot air drying furnace as necessary.

Second catalyst layer coating step

It is a step of coating the second catalyst layer by applying the prepared catalyst slurry on the cathode side according to the content of the catalyst in the CD direction on the substrate. Specifically, the catalyst electrode slurry prepared for each catalyst content is independently applied along the CD direction on the substrate through an applicator prepared according to the number of the catalyst catalyst slurry, and the applied catalyst slurry has a catalyst content It is applied sequentially in order to increase or decrease gradually.

Referring to FIG. 8 in relation to the coating method, as shown in the second catalyst layer coating step, the hydrogen electrode side catalyst slurry is applied in a spray manner by allowing the applicator to be provided in a line along the CD direction on the electrolyte membrane. The catalyst content of the catalyst slurry on the cathode side applied through the applicator is characterized by gradually increasing or decreasing for each applicator.

The applicator is sufficient to be a conventional applicator used to perform a coating process in the field of fuel cell manufacturing, and the type is not particularly limited. However, it is preferable that a plurality of applicators can be lined up in a row in the CD direction on the substrate and satisfy the condition that they are suitable for a continuous process.

When the catalyst slurry on the cathode side is applied to the desired size, the solvent is dried through a hot air drying furnace to form a second catalyst layer.

Through the above steps, an electrolyte membrane for a fuel cell is manufactured, wherein the thickness of the first catalyst layer and the second catalyst layer is kept constant along the CD direction and the MD direction. This is possible because, in the step of preparing the catalyst slurry for the anode side and the catalyst slurry for the cathode side, the contents of the solids of the catalyst and the whole ionomer constituting the slurry are kept the same and dispersed in a solvent. For example, in the case of a slurry having a small catalyst content, the ionomer content is increased by that amount, and in the case of a slurry with a relatively large catalyst content, the ionomer content is reduced by that amount, thereby maintaining the solid content.

Claims (17)

materials;
Includes a catalyst layer on both sides of the substrate,
The catalyst layer is a first catalyst layer coated on one surface of the substrate; And
Including; a second catalyst layer coated on the other side of the substrate,
The catalyst layer includes a catalyst,
The catalyst layer is an electrolyte membrane for a fuel cell that suppresses side reactions due to gas crossover, characterized in that the content of the catalyst is different in the CD direction or the MD direction. According to claim 1,
The substrate is an expanded polytetrafluoroethylene (ePTFE) or an electrolyte membrane for suppressing side reactions due to gas crossover phenomenon, characterized in that the expanded polytetrafluoroethylene (ePTFE) impregnated with ionomers in the pores. According to claim 1,
The catalyst is platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), copper ( Cu), silver (Ag), gold (Au), periphery (Sn), titanium (Ti), chromium (Cr), and a side reaction due to gas crossover, characterized in that one selected from the group consisting of combinations thereof A suppressed electrolyte membrane for fuel cells. According to claim 3,
The catalyst is an electrolyte membrane for a fuel cell that suppresses side reactions due to a gas crossover phenomenon, characterized in that supported on a carbon carrier. According to claim 1,
The catalyst layer further includes an ionomer,
The ionomer is a fluorine-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polypetylene sulfide-based polymer, polysulfone-based polymer, polyethersulfone-based polymer, polyether ketone-based polymer, polyether -Electrolyte membrane for fuel cell suppressing side reaction due to gas crossover phenomenon, characterized in that it is one selected from the group consisting of ether ketone polymer, polyphenylquinoxaline polymer, polystyrene polymer and combinations thereof. The method of claim 5,
The content of the catalyst in the catalyst layer is less than 3% by weight of the ionomer electrolyte membrane for suppressing side reactions due to gas crossover phenomenon. According to claim 1,
The catalyst layer is an electrolyte membrane for a fuel cell that suppresses side reactions due to gas crossover, characterized in that the content of the catalyst decreases in the CD direction or the MD direction. According to claim 1,
The thickness of the catalyst layer is an electrolyte membrane for a fuel cell suppressing side reactions due to the gas crossover phenomenon characterized in that the CD direction and MD direction is constant. According to claim 1,
The thickness of the catalyst layer is 1 to 10㎛, the electrolyte membrane for a fuel cell suppressing side reactions due to the gas crossover phenomenon. According to claim 1,
The catalyst layer forms a stage in the CD direction or MD direction,
The ?t amount of the catalyst is reduced according to the stage, an electrolyte membrane for a fuel cell that suppresses side reactions due to a gas crossover phenomenon. A hydrogen electrode side separation plate including a hydrogen inlet and a hydrogen outlet;
An oxygen electrode side separator plate which is joined to the hydrogen electrode side separator plate and includes an oxygen inlet and an oxygen outlet; And
Includes; a membrane-electrode assembly interposed between the hydrogen electrode side separator plate and the oxygen electrode side separator plate,
The membrane-electrode assembly includes an oxygen electrode; Hydrogen pole; And an electrolyte membrane interposed between the oxygen electrode and the hydrogen electrode.
A first catalyst layer including a catalyst is coated on one surface of the electrolyte membrane,
A second catalyst layer containing a catalyst is coated on the other surface of the electrolyte membrane,
The oxygen electrode is provided on the first catalyst layer of the electrolyte membrane,
The hydrogen electrode is provided on the second catalyst layer of the electrolyte membrane,
The oxygen electrode faces the separation plate on the oxygen electrode side,
The hydrogen electrode faces the separator on the hydrogen electrode side,
The first catalyst layer has a different content of the catalyst in the CD direction or MD direction,
The second catalyst layer is a fuel cell suppressing side reactions due to a gas crossover phenomenon, characterized in that the content of the catalyst is different in the CD direction or MD direction. Preparing two or more oxygen-catalyst catalyst slurries containing catalysts, ionomers, and solvents and having different catalyst contents;
Preparing two or more hydrogen electrode side catalyst slurries containing catalysts, ionomers, and solvents and having different catalyst contents;
Coating the first catalyst layer by sequentially applying along the CD direction on release paper in the order of decreasing catalyst content in the catalyst slurry on the oxygen side;
Depositing an electrolyte membrane on the first catalyst layer;
Including the step of coating the second catalyst layer by sequentially applying along the CD direction on the electrolyte membrane in the order of decreasing the catalyst content in the catalyst slurry on the cathode side;
A method for manufacturing an electrolyte membrane for a fuel cell that suppresses side reactions due to a gas crossover phenomenon, wherein the thickness of the first catalyst layer and the second catalyst layer is constant along the CD direction and the MD direction. The method of claim 12,
The solvent is an ethanol, isopropyl alcohol, propanol, ethoxyethanol, butanol, ethylene glycol, distilled water, amyl alcohol, and a fuel that suppresses side reactions due to gas crossover, characterized in that one selected from the group consisting of combinations thereof Method for manufacturing electrolyte membrane for batteries. The method of claim 12,
In the step of preparing the catalyst slurry on the oxygen electrode side, there is no catalyst electrode slurry on the oxygen electrode side having a catalyst content of 0% among the prepared two or more oxygen electrode catalyst slurry,
In the step of preparing the catalyst slurry on the cathode side, there is no hydrogen anode catalyst slurry having a catalyst content of 0% among the prepared two or more cathode catalyst slurries, for fuel cells suppressing side reactions due to gas crossover. Electrolyte membrane manufacturing method. The method of claim 12,
In the step of coating the sieve catalyst layer and the step of coating the sieve catalyst layer, an electrolyte for a fuel cell suppressing side reactions due to a gas crossover phenomenon characterized by applying an oxygen cathode catalyst slurry and a hydrogen cathode catalyst slurry through a spray method. Membrane manufacturing method. The method of claim 12,
In the step of coating the first catalyst layer, two or more oxygen-side catalyst slurries having different catalyst contents are respectively applied through an applicator prepared according to the number of the oxygen-side catalyst slurry,
In the step of coating the second catalyst layer, side reactions due to a gas crossover phenomenon are suppressed, characterized in that two or more catalyst anode catalyst slurries having different catalyst contents are applied through an applicator prepared according to the number of catalyst cathode slurry. Method for manufacturing an electrolyte membrane for a fuel cell. The method of claim 12,
In the step of coating the first catalyst layer, the step of laminating the electrolyte membrane and the step of coating the second catalyst layer, drying after each step further comprises an electrolyte membrane for suppressing side reactions due to gas crossover. Manufacturing method.

Images