WO2006038475A1

WO2006038475A1 - Fuel cell and separator for fuel cell

Info

Publication number: WO2006038475A1
Application number: PCT/JP2005/017504
Authority: WO
Inventors: Eiichi Yasumoto; Shinichi Arisaka; Shigeyuki Unoki; Soichi Shibata; Kazuhito Hatoh
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-10-01
Filing date: 2005-09-22
Publication date: 2006-04-13

Abstract

A fuel cell stably operable while securely preventing flooding phenomenon, particularly, even when a gas flow velocity is low which tends to cause the flooding phenomenon. In separator plates (30A) having gas flow passages crossing the direction of a gravity, the hydrophilic property of the inner bottom surface portion (c) of the gas flow passages (32A) crossing the direction of the gravity is increased more than that of the other portions (a) and (b) of the gas flow passages.

Description

Specification

Fuel cell and fuel cell separator

Technical field

TECHNICAL FIELD [0001] The present invention relates to an improvement in a separator plate of a fuel cell, particularly a polymer electrolyte fuel cell, used in a power source for portable devices, a portable power source, a power source for electric vehicles, a domestic cordage energy system, and the like.

Background art

[0002] A polymer electrolyte fuel cell is one in which a fuel gas such as hydrogen and an oxidizing gas such as air are electrochemically reacted by a gas diffusion electrode to simultaneously generate electricity and heat. FIG. 9 is a schematic cross-sectional view showing the configuration of a conventional polymer electrolyte fuel cell. The polymer electrolyte fuel cell 111 basically includes a polymer electrolyte membrane 101 that selectively transports cations (hydrogen ions), and a pair of electrodes (anodes) disposed on both sides of the polymer electrolyte membrane 101. And force sword) 104. The electrode 104 is composed of a catalyst layer 102 mainly composed of carbon powder supporting an electrode catalyst (for example, platinum metal) and a gas diffusion layer 103 formed on the outer surface of the catalyst layer 102 and having air permeability and conductivity. Become.

[0003] Outside the membrane electrode assembly (MEA) 110 composed of the polymer electrolyte membrane 101 and the electrode 104, the MEA is mechanically fixed, and adjacent MEAs 110 are electrically connected to each other in series. Further, separator plates 120 and 130 having gas flow paths for supplying fuel gas or oxidant gas (reactive gas) to the electrode 104 and carrying away gas generated by the reaction or surplus gas are disposed. . In addition, a gas seal material 106 is disposed around the electrode 104 with a polymer electrolyte membrane 101 interposed therebetween so that fuel gas and oxidant gas do not leak out of the battery or mix with each other. O-rings 124 and 125 are also arranged to prevent water from leaking outside the battery.

[0004] The gas flow paths 122, 132 can be provided separately from the separator plates 120, 130. As shown in FIG. 9, the gas flow paths 122 are formed by providing grooves on the surfaces of the separator plates 120, 130. It is common.

Cooling water to keep the battery temperature constant is applied to the other surface of separator plates 120 and 130. Circulating cooling water channels 123 and 133 are provided. By circulating the cooling water, the heat energy generated by the reaction can be used in the form of hot water.

[0005] In this type of fuel cell, especially when the water generated by the cell reaction on the power sword side stays in the gas flow path 132 of the separator plate 130 and the amount of generated water is very large, the gas flow path is completely removed. Blocks 132. This is called the flooding phenomenon. The flooding phenomenon can also occur when the feed gas, which is just due to the product water, is excessively humidified. Once the flooding phenomenon occurs, there is a possibility that the gas will not flow in that part, and the battery performance will be drastically reduced, preventing it from functioning as a battery.

[0006] To deal with such a problem, for example, in Patent Document 1, by performing hydrophilic treatment on the downstream side of the gas flow path of the separator plate, the residual water inside the fuel cell is efficiently discharged out of the fuel cell. A method intended to do so is disclosed. Further, for example, in Patent Document 2, the contact angle between the convex portion and the electrode structure is made smaller than the contact angle of water with respect to the separator surface, regardless of whether the surface property of the separator is hydrophilic or force repellency. Thus, a method intended to enhance the drainage of water staying in the gas flow path is disclosed.

Patent Document 1: Japanese Patent Laid-Open No. 2002-298871

Patent Document 2: JP 2003-197213

Disclosure of the invention

Problems to be solved by the invention

[0007] According to Patent Document 1 described above, since the hydrophilization treatment is performed on the outlet of the gas flow path, the generated water generated inside the battery, the condensed water generated due to excessive humidification in the supply gas, etc. There is a possibility that residual water can be discharged efficiently.

However, particularly when the gas is excessively humidified or when the gas flow rate is low, residual water stays in the upstream portion of the gas flow path and a flooding phenomenon occurs. In addition, since the entire inner surface of the outlet portion of the gas flow path is subjected to hydrophilic treatment, if the entire flow path is covered with water, water may remain in the entire flow path, and a flooding phenomenon may occur.

[0008] In addition, according to the method of Patent Document 2, the contact angle between the projection and the electrode structure, which is not related to the surface properties of the separator plate, may be made smaller than the contact angle of water with respect to the separator surface. , The selection range (adopting range) of separator plate components can be widened there is a possibility. In addition, since there is no need to perform a special treatment on the surface of the separator plate, there is a possibility that the process can be saved.

However, according to this method, the contact angle with respect to the electrode structure of the convex portion of the separator plate is uniquely determined, so that the degree of freedom in designing the separator plate is reduced. Also, depending on how the fuel cell is installed, there is a risk that the water pushed out by the interface force between the gas diffusion layer and the separator plate cannot be smoothly discharged outside the fuel cell.

[0009] In view of the above problems, the present invention can reliably prevent the flooding phenomenon even when the gas flow rate is small and the flooding phenomenon occurs. An object of the present invention is to provide a fuel cell that can be operated. Furthermore, the present invention provides a separator capable of easily and reliably constructing a fuel cell that can reliably prevent the flooding phenomenon even when the gas flow rate is low and the flooding phenomenon is likely to occur. It is also an object to provide a board.

Means for solving the problem

[0010] In order to solve the above problems, the present invention provides:

A fuel cell in which a polymer electrolyte membrane and a membrane electrode assembly including an anode and a force sword sandwiching the polymer electrolyte membrane are stacked in a direction substantially perpendicular to the normal direction of the ground plane through a separator plate. And

The separator plate has a gas flow path for supplying fuel gas to the surface facing the anode and supplying oxidant gas to the surface facing the power sword,

The gas channel has a gas channel part that intersects the direction of gravity,

Provided is a fuel cell characterized in that the hydrophilic force of the bottom side region on the inner surface of the gas flow path portion is higher than the other portions on the inner surface of the gas flow path portion.

Here, the “gas flow path portion” that intersects the gravity direction of the gas flow path is, for example, a main flow path (long) extending in a direction substantially perpendicular to the gravity direction in the case of a serpentine type gas flow path. ! /, Channel) part. Therefore, the gas flow path of the separator plate of the present invention does not need to intersect the direction of gravity over the entire length! /.

In the plane of the separator plate in the fuel cell of the present invention, the ratio (area) of the gas flow path portion in the entire gas flow path varies depending on the separator shape and structure. Although it cannot be determined uniquely, it can be set within a range not impairing the effects of the present invention, and from the viewpoint of more effectively suppressing flooding, it is preferably 80% or more and less than 100%. More preferably, it is 80% or more and 98% or less.

In addition, as a gas flow path of the separator plate, a serpentine-type flow path including a plurality of straight portions and a turn portion that connects the ends of adjacent straight portions from the upstream side to the downstream side is often used. In this case, however, the straight part or the turn part intersects the direction of gravity.

In the present invention, the gas flow path of the separator plate may be constituted by a plurality of linear flow paths that are substantially parallel to the installation surface of the fuel cell. In this case, it is preferable to provide a highly hydrophilic region according to the present invention over the entire length of the gas flow path.

In the fuel cell of the present invention, the separator plate has the above-described configuration, so that the gas in the gas flow path intersecting the gravity direction of the hydraulic gas flow path formed into droplets in the gas flow path. It stays in the area below the gravity direction on the inner surface of the flow path, that is, the area on the bottom side. In the fuel cell of the present invention, since the hydrophilicity of the bottom side region is set to be selectively higher than other portions, a hydraulic liquid film is preferentially formed on the bottom side region and spreads. As a result, it is possible to smoothly discharge water with gas diffusion layer strength, and the upper side of the gas flow path portion can be opened without being blocked to prevent blockage of the gas flow path due to flooding. .

Here, in the present invention, the “region on the bottom surface side of the inner surface of the gas flow channel portion” is a partial region intersecting with the direction of gravity of the inner surface of the gas flow channel as described above, and the partial region. Lower part of the region {When assuming that there is no gas flow in the gas channel, water droplets (water droplets smaller than the gas channel) will act on the droplets This is a partial area that lands when it falls in the gas flow path due to gravity.

[0014] Furthermore, the present invention provides:

Used in fuel cells in which a polymer electrolyte membrane and a membrane electrode assembly including an anode and a force sword sandwiching the polymer electrolyte membrane are stacked in a direction substantially perpendicular to the normal direction of the ground plane via a separator plate Separator plate,

A gas flow path for supplying gas to the anode or power sword;

The gas channel has a gas channel part that intersects the direction of gravity, The present invention provides a fuel cell separator plate characterized in that the hydrophilic force of the bottom side region on the inner surface of the gas flow path portion is higher than the other portions on the inner surface of the gas flow path portion.

[0015] By using this separator plate, in the gas flow path intersecting with the gravity direction of the hydraulic gas flow path formed into droplets in the gas flow path, the bottom side of the inner surface of the gas flow path, that is, the bottom surface It will stay in the side area. For this reason, the separator of the present invention has higher hydrophilicity on the bottom side than other parts, so that the water spreads as a liquid film on the bottom side, and water can be smoothly discharged from the gas diffusion layer. In addition, since the upper side of the gas flow path portion is open, a highly reliable fuel cell that can prevent the gas flow path from being blocked by flooding can be configured easily and reliably.

The invention's effect

[0016] As described above, according to the present invention, hydrophilicity is selectively imparted to a specific portion in the gas flow path of the fuel cell separator, and the contact angle of water is made smaller than other portions. Even when the gas flow rate is low, it is possible to provide a highly reliable fuel cell that can reliably prevent the flooding phenomenon compared to the conventional case and can perform stable operation. In addition, according to the present invention, it is possible to provide a separator plate for a fuel cell that can easily and reliably constitute the fuel cell of the present invention.

Brief Description of Drawings

FIG. 1 is a schematic longitudinal sectional view showing a basic configuration of a first embodiment of a fuel cell according to the present invention.

2 is an enlarged cross-sectional view of a main part of a separator plate 30 of the fuel cell 100 shown in FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of a separator plate provided in a fuel cell according to a second embodiment of the fuel cell of the present invention.

FIG. 4 is an enlarged cross-sectional view of a main part of a separator plate provided in a fuel cell according to a third embodiment of the fuel cell of the present invention.

FIG. 5 is a diagram for explaining a modification of the installation state of the fuel cell 100 shown in FIG. 1.

FIG. 6 is a graph showing current-voltage characteristics of fuel cells of Examples and Comparative Examples of the present invention.

[Fig. 7] Average when the air utilization of the fuel cells of the examples and comparative examples of the present invention is changed. It is a graph which shows the fluctuation | variation of a voltage.

FIG. 8 is a graph showing current-voltage characteristics of a fuel cell according to an example of the present invention.

FIG. 9 is a schematic longitudinal sectional view showing a basic structure of a conventional fuel cell.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions may be omitted.

[First embodiment]

FIG. 1 is a schematic cross-sectional view showing the basic configuration of the first embodiment of the fuel cell of the present invention. This polymer electrolyte fuel cell 100 basically includes a polymer electrolyte membrane 1 that selectively transports cations (hydrogen ions), and a pair of electrodes (anode and force) disposed on both sides of the polymer electrolyte membrane 1. Sword) consists of four. The electrode 4 includes a catalyst layer 2 mainly composed of carbon powder supporting an electrode catalyst (for example, a noble metal such as platinum metal), and a gas diffusion layer 3 formed on the outer surface of the catalyst layer 2 and having air permeability and conductivity. It consists of.

[0019] On the outer side of the membrane electrode assembly (MEA) 10 composed of the polymer electrolyte membrane 1 and the electrode 4, the MEA is mechanically fixed, and adjacent MEAs 10 are electrically connected in series with each other. The separator plate 20, 30 having a gas flow path for supplying a fuel gas or an oxidant gas (reactive gas) to the electrode 4 and carrying away a gas generated by the reaction or excess gas. Is placed. In addition, a gas seal material 6 is disposed around the electrode 4 with the polymer electrolyte membrane 1 interposed therebetween so that fuel gas and oxidant gas do not leak out of the battery or mix with each other. O-rings 24 and 25 are arranged so that the cooling water does not leak outside the battery. A plurality of MEAs 10 configured as described above are stacked alternately with separator plates interposed therebetween to form a cell stack of a fuel cell.

[0020] The material constituting the gas diffusion layer 3 is not particularly limited, and those known in the art can be used. For example, a conductive porous substrate such as carbon cloth or carbon paper can be used.

The catalyst layer 2 is a catalyst layer forming electrode comprising conductive carbon particles supporting an electrode catalyst made of a noble metal, a polymer electrolyte having cation (hydrogen ion) conductivity, and a dispersion medium. It can be formed by a method known in the art using the ink.

Furthermore, the MEA 10 can also be produced from the polymer electrolyte membrane 1, the catalyst layer 2 and the gas diffusion layer 3 as described above by a technique known in the art.

As described above, the fuel cell of the present invention is mainly characterized by the gas flow paths 22 and 32 of the separator plates 20 and 30. Gas channels 22 and 32 are formed by providing grooves on the surfaces of the gas channels 22 and 32. Further, on the other surface of the separator plates 20 and 30, cooling water flow paths 23 and 33 for circulating cooling water for keeping the battery temperature constant are provided. By circulating cooling water here, the heat energy generated by the reaction can be used in the form of hot water.

[0022] The separator plate in the fuel cell of the present invention includes an anode side separator plate 20 and a force sword side separator plate 30, and a cooling water flow path is formed therebetween. The anode-side separator plate 20 has a fuel gas flow path 22 for supplying fuel gas to the anode on the surface facing the anode, and a cooling water flow path 23 on the opposite surface. The force sword side separator plate 30 has an oxidant gas flow channel 32 for supplying an oxidant gas to the force sword on the surface facing the force sword, and a cooling water flow channel on the opposite surface. 33.

[0023] Between the anode-side separator plate 20 and the force-sword-side separator plate 30 of the adjacent single cell, a set of cooling water channels formed by the channels 23 and 33 is formed. A groove 24 is formed in the anode side separator plate 20 so as to surround the cooling water flow path 23. By inserting an O-ring 25 therein, the cooling water flows between the separator plates 20 and 30. Prevent leakage to the outside.

In FIG. 1, a cooling water flow path may be arranged for every two to three force single cells in which a cooling water flow path is formed between the single cells. When the cooling water flow path is not formed between the single cells, the fuel gas flow path is provided on one side and the oxidant gas flow path is provided on the other side. It is also possible to use a single separator plate that doubles as the sword side separator plate.

In addition, the material of the separator plate includes metal, carbon, and a material in which graphite and resin are mixed, and can be used widely. For example, separator plates obtained by injection molding a mixture of carbon powder and binder, or separator plates made of titanium or stainless steel Those having a surface plated with gold can also be used.

Here, as shown in FIG. 1, the fuel cell of the present invention is configured such that a plurality of MEAs are stacked in a direction substantially perpendicular to the normal direction of the ground plane P of the fuel cell via a separator plate, In Fig. 1, the vertical direction indicated by the Z axis in the figure is the direction of gravity.

Hereinafter, a separator plate (first embodiment of the separator plate of the present invention) mounted on the fuel cell 100 will be described in more detail with reference to the drawings.

FIG. 2 is an enlarged cross-sectional view of a main part of the separator plate 30 of the fuel cell 100 shown in FIG. In particular, FIG. 2 shows the main part of the power sword side separator plate 30A of the separator plate 30 shown in FIG. 1 and the gas diffusion layer 3 of the force sword in contact with the force sword side separator plate 30A. FIG. 4 is an enlarged cross-sectional view of a main part when cut along a direction substantially perpendicular to P. Therefore, the gas flow path shown in FIG. 2 is a flow path that intersects the direction of gravity. The oxidant gas flow path 32A of the separator plate 30A is configured by a groove provided to open on the surface of the separator plate. When the groove is covered with the gas diffusion layer 3, the groove has a rectangular cross section. In the fuel cell 100, the hydrophilicity of the bottom portion c of the rectangle (that is, the bottom side region of the inner surface of the gas flow path 32A that intersects the direction of gravity) is the portion of the other two sides of the rectangle described above. It is set larger than the hydrophilicity of a and b.

[0026] With such a configuration, first, generated water is discharged from the gas diffusion layer 3 to the gas flow path 32A in a substantially normal direction of the main surface of the electrode 4 (direction indicated by an arrow X in the figure). Since the gas diffusion layer 3 usually has a certain level of water repellency, the discharged generated water does not return to the gas diffusion layer 3 side. The hydrophilicity of the rectangular c side portion c of the gas flow path 32A (that is, the bottom side area of the inner surface of the gas flow path 32A that intersects the direction of gravity) is that of the other two side portions a and b. Compared to the case where only the action of gravity is applied, the generated water is directed toward the lower part of the gas flow path 32A in the direction of gravity (that is, in the direction substantially parallel to the direction of arrow Y in the figure). It will be easier to fall, and will move preferentially to the area c of the bottom part of the rectangle, and will stay easily.

[0027] Since the hydrophilicity of the region c on the bottom side is higher than that of the other portions, the generated water spreads as a liquid film, and there is a space in which gas can flow on the upper side of the gas flow path 32A. Therefore, the generated water is almost normal to the rectangular cross section of the gas flow path 32A in the figure (paper The gas channel 32A flows smoothly along the direction (substantially perpendicular to the surface) and discharged. That is, water can be smoothly discharged from the gas diffusion layer, and at least the upper side of the gas flow path 32A can be opened without being blocked, and the gas flow path can be prevented from being blocked by flooding. .

Thus, in the fuel cell 100, water is smoothly discharged from the gas diffusion layer 3. Further, surplus water that has become droplets in other parts of the gas flow path 32A regardless of the presence or absence of generated water also spreads as a liquid film in this region, and the gas flow path 32A is not blocked.

[0028] The degree of hydrophilicity of the inner surface of the gas channel 32A can be confirmed by measuring the contact angle with water. The water contact angle for the hydrophilized region is smaller than the water contact angle for other parts. As a result, in the region on the bottom side of the gas flow path 32A, the generated water and surplus water are more easily spread as a liquid film, and flooding can be prevented. In addition, even when the contact angle of water with respect to the region on the bottom side of the gas flow path 32A is smaller than the contact angle of water with the gas diffusion layer, the surface force of the gas diffusion layer also increases the smoothness of water to the gas flow path 32A. As a result, the flooding can be prevented.

[0029] Depending on the design conditions, arrangement conditions, operating conditions, etc. of the fuel cell 100, the optimum value of the contact angle of water with respect to the region on the bottom surface side of the gas flow path 32A cannot be uniquely defined, but the gas flow path 32A A sufficient effect can be obtained if the contact angle of water with the area on the bottom side is approximately 0 to 50 °.

The contact angle of water can be measured using, for example, FACE X-150 manufactured by Kyowa Interface Chemical Co., Ltd. It can also be measured using the Wilhelmi method, for example.

[0030] The method for hydrophilizing the bottom side region of the gas flow path 32A is not particularly limited as long as the effects of the present invention described above can be obtained. For example, a method of changing the surface property of the part by blasting by spraying a fine powder, or a method of imparting a hydrophilic functional group by ultraviolet irradiation or plasma treatment can be used.

These types of treatment methods can be properly used depending on the material of the separator plate. For example, the blast treatment can be applied to a carbon separator plate and a metal separator plate, and the plasma treatment can be applied to a carbon separator plate.

[0031] In the method using blasting, the surface roughness (Ra) of the surface of the separator plate is changed by blasting, and as a result, the contact angle of water is reduced. Since it varies depending on the material of the separator plate used, etc., it cannot be uniquely defined. However, in the case of a carbon separator plate, the contact angle of water can be reduced by increasing Ra.

On the other hand, the plasma treatment method may be performed under reduced pressure or atmospheric pressure. Moreover, the ultraviolet irradiation process which irradiates an ultraviolet light in ozone atmosphere may be sufficient.

[0032] Contrary to the above, by performing water-repellent treatment by removing the region on the bottom surface side of the inner surface of the gas flow path 32A, the hydrophilicity of the region on the bottom surface side can be improved as a result. . In this case, a fluorine resin dispersion such as polyethylene terephthalate (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is applied to the portion other than the bottom side and dried. Water repellency can be imparted. Of course, as described above, hydrophilicity may be imparted to the region on the bottom side, and water repellent treatment may be applied to the portion other than the region on the bottom side. The method for imparting water repellency is not limited to this.

[0033] Further, in addition to the above, the hydrophilicity of the region on the bottom surface side of the gas flow path 32A can be increased by performing water repellent treatment on the gas diffusion layer 3 side facing the gas flow path 32A. The gas diffusion layer 3 inherently has a certain degree of water repellency. By performing water repellency treatment on the gas diffusion layer 3 side facing the gas flow path 32A, the effect of the present invention can be obtained more reliably. become able to.

[0034] As a method of performing the water repellent treatment on the gas diffusion layer 3, it is sufficient to perform the water repellent treatment at least in the shape similar to the shape of the gas flow channel 32A in the portion facing the gas flow channel of the gas diffusion layer 3. In terms of substantial viewpoint power, it is preferable that the entire gas diffusion layer 3 is subjected to water repellent treatment. Conducting water-repellent treatment by immersing the conductive porous substrate such as carbon paper and carbon cloth described above in a fluorine-containing resin dispersion containing PTFE and FEP, and drying to remove the dispersion medium. Can do.

[0035] [Second Embodiment]

Next, a second embodiment of the fuel cell of the present invention will be described. The fuel cell (not shown) of the second embodiment is the same as that of the fuel cell 100 of the first embodiment shown in FIG. The separator plate 30 is replaced with a different configuration, and the configuration other than the separator plate 30 is the same as that of the fuel cell 100 of the first embodiment.

Hereinafter, the separator plate (second embodiment of the separator plate of the present invention) provided in the fuel cell of the second embodiment will be described.

FIG. 3 is an enlarged cross-sectional view of a main part of a separator plate provided in the fuel cell according to the second embodiment. More specifically, FIG. 3 shows a cathode side separator plate 30B among the separator plates of the fuel cell of the second embodiment, and main portions of the gas diffusion layer 3 of the force sword in contact with the force sword side separator plate 30B. FIG. 4 is an enlarged cross-sectional view of a main part when cut along a direction substantially perpendicular to the ground plane of the battery.

The gas flow path 32B of the power sword side separator plate 30B of the fuel cell of the second embodiment is formed by a groove provided on the surface of the separator plate as in the fuel cell 100 of the first embodiment described above. . Here, when the groove is covered with the gas diffusion layer 3, a substantially trapezoidal cross section with the gas diffusion layer side at the bottom is formed. The lower side c of this trapezoidal side is the area on the bottom side of the inner surface of the gas flow path 32B that intersects the direction of gravity, and the hydrophilicity of this area is greater than the other parts a and b. is doing.

[0037] [Third embodiment]

Next, a third embodiment of the fuel cell of the present invention will be described. The fuel cell (not shown) of the third embodiment is obtained by replacing the separator plate 30 in the fuel cell 100 of the first embodiment shown in FIG. The configuration is the same as that of the fuel cell 100 of the first embodiment.

Hereinafter, a separator plate (third embodiment of the separator plate of the present invention) provided in the fuel cell of the third embodiment will be described.

FIG. 4 is an enlarged cross-sectional view of a main part of a separator plate provided in the fuel cell of the third embodiment. More specifically, FIG. 4 shows a cathode side separator plate 30C among the separator plates of the fuel cell according to the third embodiment, and main portions of the gas diffusion layer 3 of the force sword in contact with the force sword side separator plate 30C. FIG. 4 is an enlarged cross-sectional view of a main part when cut along a direction substantially perpendicular to the ground plane of the battery.

The power sword side separator plate 30C of the fuel cell of the second embodiment and the force sword in contact with the separator 30C The main part of the gas diffusion layer 3 is shown as a cross section cut in a direction perpendicular to the ground plane of the battery. The gas flow path 32C of the force sword side separator plate 30C is the fuel cell 1 of the first embodiment.

Like the fuel cell of 00 and the second embodiment, it is formed by a groove provided on the surface of the separator plate. This groove has a U-shaped cross section, and the hydrophilicity of the region on the bottom side e of the inner surface of the gas flow path constituted by the groove is made larger than the hydrophilicity of the other part d.

[0039] As shown in FIGS. 3 and 4, by making the hydrophilicity of the region on the bottom side of the inner surface of the gas flow path intersecting the direction of gravity larger than the hydrophilicity of other portions, the first embodiment The same effect can be demonstrated and flooding can be prevented.

[0040] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment.

For example, in the above-described embodiment, as described as the ground contact surface P in FIG. 1, the “ground contact surface” on which the fuel cell is disposed has been described as a smooth surface (ground) substantially perpendicular to the direction of gravity. The “ground plane” in the invention is not limited to this. The “ground plane” in the present invention may vary depending on the installation space where the fuel cell of the present invention is installed, and may be a slope having a certain angle with respect to the horizontal direction. . For example, as shown in FIG. 5, the fuel cell 100 of the first embodiment is installed in a normal state inclined obliquely with respect to a plane R (for example, the ground) parallel to the horizontal direction via a support 200. You can ask! / In this case, the surface Q force including the tangent line between the contact point S between the fuel cell 100 and the support 200 and the contact point T between the fuel cell 100 and the ground surface is a ground contact surface in the present invention.

[0041] In the present invention, the cross-sectional shape of the gas flow path provided in the separator plate is not particularly limited as long as the region on the bottom side of the gas flow path that intersects the direction of gravity is made hydrophilic. Shapes other than the rectangular shape, the trapezoidal shape, and the U shape (R shape) described using the above-described embodiments may be used. This region of increasing hydrophilicity can be appropriately changed depending on the operating conditions of the fuel cell and the type of electrolyte membrane electrode assembly used. It should be decided as appropriate within the range up to about half of the gas flow path.

Furthermore, in each of the above-described embodiments, the force sword side separator plate has “the hydrophilicity of the region on the bottom surface side of the inner surface of the gas flow path portion is higher than the other portions of the inner surface of the gas flow channel portion. Although the description has been given of the case of applying the “Yes” configuration, the present invention is not limited to this. Similarly, a configuration in which “the hydrophilicity of the region on the bottom surface side on the inner surface of the gas flow path portion is made higher than the other portions on the inner surface of the gas flow path portion” can be applied to the anode side separator plate as well. it can. In addition, a configuration in which “the hydrophilic force of the region on the bottom surface side of the inner surface of the gas flow path portion is made higher than the other portions on the inner surface of the gas flow path portion” is simultaneously applied to the force sword side separator plate and the anode side separator plate. May be.

[0043] From the viewpoint of fuel cell design and cost reduction, flooding is likely to occur! / ヽ It may be applied to only one of the separator plates. Further, the position of the bottom side region and other regions, the size of the bottom side region and other regions, the hydrophilicity of the bottom side region, and the area of the anode side separator plate and the force sword side separator plate are independently determined. The hydrophilicity of other areas can also be set.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1

First, a catalyst layer was produced. Catalyst body (50% by mass is 1 ^) obtained by supporting platinum as an electrode catalyst on Ketjen Black (Ketjen Black EC, Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder. ) 66 parts by mass of 33 parts by mass (polymer dry mass) of perfluorocarbon sulfonic acid ionomer (5% by mass Nafion dispersion manufactured by Aldric h, USA) that is a hydrogen ion conductive material and binder After mixing, the obtained mixture was molded to prepare a catalyst layer (10 to 20 μm).

The catalyst layer thus obtained and a carbon cloth (Carbon GF-20-31E manufactured by Nippon Carbon Co., Ltd.) to be used as a gas diffusion layer are combined with a polymer electrolyte membrane (Nafionl l2 membrane manufactured by DuPont USA, ion exchange group capacity). : 0.9 meqZg) was bonded by hot pressing to produce an 18 cm square MEA with a 12 cm square anode and a force sword.

Thus, the fuel cell of the present invention having the structure shown in FIG. 1 was assembled using the obtained MEA. The anode side separator plate and the force sword side separator plate have outer dimensions of 160 mm X 16 Omm X 5 mm, and have a gas flow path with a width of 0.9 mm and a depth of 0.7 mm, as shown in Fig. 4. Graphite plate impregnated with phenol resin having carbon (carbon separator plate) Was subjected to a hydrophilic treatment for assembly.

The hydrophilic treatment was performed using an oxygen plasma treatment apparatus. As the oxygen plasma device, a general RF plasma device of a decompression parallel plate type is used, the RF power source is 13.56 MHz frequency, the output is 500 W, the oxygen supply amount is 500 sccm, the processing time is 5 minutes, and the chamber internal pressure is 0.5 Torr.

[0046] A masking material is arranged in advance in all parts other than the part e, which is a hydrophilic treatment area, so that only a specific partial area is subjected to plasma treatment. The contact angle of water with the part e after the plasma treatment was 0 °, and the contact angle of water with the part d was 100 °, and it was confirmed that the part e was selectively hydrophilized. .

[0047] Using the anode side separator plate and the force sword side separator plate treated in this way, 80 single cells were stacked to produce a fuel cell (stack). Hydrogen gas is supplied to the anode of this stack and air is supplied to the power sword with humidification so that the dew point is 75 ° C. Coolant inlet temperature is 80 ° C, fuel utilization is 80%, air The battery characteristics were examined by adjusting the utilization rate to 40%.

[0048] Fig. 6 shows the average battery voltage per single cell when the current density was changed from 0 to 0.8 AZcm ² . At this time, the amount of gas was adjusted so that the utilization rate of the gas would be the above value. As a result, even when the current density was high, the battery voltage was not greatly reduced. Fig. 7 shows the average battery voltage when the current density is fixed at 0.3 AZcm ² and the air utilization is varied from 40% to 70%. As a result, even when the air utilization rate was high, flooding was suppressed, with a small drop in battery voltage, and the battery voltage was stable.

Fuel cell stacks of Examples 2 and 3 were fabricated in the same manner as in Example 1 except that the separator plate having the structure shown in FIGS. 2 and 3 was used, and the same battery test as in Example 1 was performed. The parts subjected to the hydrophilic treatment were designated as part c in FIG. 2 and part c in FIG.

As a result, as in Example 1, the battery voltage was not significantly reduced even in the high current density region, and the battery voltage was stable. Further, when the air utilization rate was changed, the flooding was suppressed, and the battery voltage was stable as in Example 1, in which the decrease in battery voltage was small.

[0050] << Comparative Example 1 >> A fuel cell stack having the same configuration as in Example 1 was prepared except that a separator plate not subjected to hydrophilic treatment was used in the gas flow path, and the same cell test as in Example 1 was performed.

As a result, as shown in Fig. 6, a large drop in battery voltage and unstable behavior were observed in the high current density region. In addition, as shown in Fig. 7, when the air utilization rate was changed, the stability of the battery voltage deteriorated due to the large decrease in battery voltage when the air utilization rate was high, that is, when the gas flow rate was small.

[0051] <Comparative Example 2>

A fuel cell stack having the same configuration as in Example 1 was prepared, except that a separator plate with a hydrophilic treatment applied to the entire flow path without masking the gas flow path was prepared, and a battery test similar to that in Example 1 was performed. It was.

As a result, as shown in Fig. 6, a decrease in battery voltage and unstable behavior were observed in the high current density region. In addition, as shown in Fig. 7, when the air utilization rate is changed, the stability of the battery voltage is higher than that of Comparative Example 1 when the air utilization rate is high, that is, when the gas flow rate is small, the battery voltage decreases greatly. Slightly improved power It was worse than Example 1.

[0052] <Example 4>

In this example, a fuel cell stack having the same configuration as in Example 1 was prepared, except that a water-repellent gas diffusion layer was used, and the same cell test as in Example 1 was performed.

In this example, the carbon paper was preliminarily reinforced with tetrafluoroethylene monohexafluoropropylene copolymer Dispurgeon (ND-1 (trade name) manufactured by Daikin Industries, Ltd.). Water was immersed in a water repellent treatment solution mixed at a volume ratio of 1: 1, dried, and then fired at 380 ° C. to give a water repellent treatment to obtain a gas diffusion layer.

FIG. 8 shows the battery voltage when the current density was changed from 0 to 0.8 AZcm ² in comparison with Example 1. At this time, the amount of gas was adjusted so that the utilization rate of the gas would be the above value. As a result, flooding was suppressed even when the current density was high, no significant decrease in battery voltage was observed, and the decrease in battery voltage in the high current density region was smaller than in Example 1.

[0054] <Example 5>

In this example, a fuel cell stack was constructed in the same manner as in Example 1 except that a separator plate subjected to the following treatment was used, and the cell characteristics were examined under the same conditions as in Example 1. In other words, the parts a and b of the gas flow path of the separator plate having the structure shown in FIG. 2 are disperseed with tetrafluoroethylene monohexafluoropropylene copolymer (manufactured by Daikin Industries, Ltd.). ND-1 (trade name)) and water in a volume ratio of 1: 1 were applied, dried, and then fired at 380 ° C for water repellent treatment. Thereafter, the oxygen plasma apparatus used in Example 1 was used to perform hydrophilic treatment on the portion c of the gas flow path. Masking material was previously placed on all other parts so that only part c was plasma treated. The water contact angle for part c of the final separator plate was 0 ° and the water contact angle for parts a and b was 120 °.

As a result, flooding was suppressed as in Example 1, and the battery voltage was not significantly reduced even in the high current density region, and the battery voltage was stable.

Industrial applicability

[0056] In the fuel cell of the present invention, the flooding phenomenon is suppressed and stable operation can be performed. Therefore, it can be used as a power source for portable devices and a power source for portable devices. It can also be applied to fuel cells for electric vehicles or household cogeneration systems.

Claims

The scope of the claims

[1] A plurality of membrane electrode assemblies including a polymer electrolyte membrane, an anode sandwiching the polymer electrolyte membrane, and a force sword are laminated in a direction substantially perpendicular to the normal direction of the ground plane via a separator plate A fuel cell,

The separator plate has a gas flow path for supplying fuel gas to the surface facing the anode and supplying oxidant gas to the surface facing the force sword;

The gas flow path has a gas flow path portion that intersects the direction of gravity,

A fuel cell characterized in that the hydrophilic force of the bottom side region on the inner surface of the gas flow path portion is higher than the other portions on the inner surface of the gas flow path portion.

[2] The gas flow path is a groove force formed in the separator plate,

The cross-sectional shape of the gas flow path formed when the groove is covered with the anode or the force sword is substantially rectangular,

2. The fuel cell according to claim 1, wherein the region on the bottom surface side is a region of a bottom side portion of the substantially rectangular shape.

3. The fuel cell according to claim 1, wherein a contact angle of water in the bottom side region is smaller than a contact angle of water in the other part.

[4] The region according to claim 1, wherein the bottom side region is blasted or plasma treated.

V, a fuel cell according to any of the above.

[5] The inner surface of the gas flow path is subjected to water repellent treatment except for the region on the bottom surface side.

~ 4! The fuel cell according to any one of the above.

[6] A plurality of membrane electrode assemblies including a polymer electrolyte membrane and an anode sandwiching the polymer electrolyte membrane and a force sword are laminated in a direction substantially perpendicular to the normal direction of the ground plane via a separator plate A separator plate used in a fuel cell,

A gas flow path for supplying gas to the anode or power sword;

A separator plate for a fuel cell, characterized in that the hydrophilic force of the bottom side region on the inner surface of the gas flow path portion is higher than the other portions on the inner surface of the gas flow path portion.