JP3334700B2 - Polymer electrolyte fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more particularly to a structure of a reaction gas flow groove of a separator constituting a unit cell.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view schematically showing a basic structure of a unit cell of a polymer electrolyte fuel cell. A fuel electrode 12 and an oxidant electrode are provided on both sides of the proton conductive polymer electrolyte membrane 11.
13 and place. Further, on both outer sides thereof, a plurality of reaction gas flow grooves 15 for supplying a fuel gas to the fuel electrode 12 and an oxidant gas to the oxidant electrode 13, respectively, and a cooling water to flow therethrough to maintain the battery at an appropriate temperature. The separator 14 provided with the cooling water flow groove 16 is disposed so that the reaction gas flow groove 15 faces the fuel electrode 12 or the oxidant electrode 13, and is kept airtight by a gas seal body 17, and the unit cell is formed. Constitute.

FIG. 2 is a side view schematically showing the structure of a fuel cell stack formed by stacking the unit cells having the structure shown in FIG. A plurality of unit cells 21 are stacked, a current collecting plate 22 is disposed at both ends thereof, and an insulating plate 23 having an electric insulation function is disposed outside the cells 21. The insulating plate 23 is sandwiched by a tightening plate 24, a tightening bolt 25, and a plate. Tighten using a spring 26 and a tightening nut 27,
Press and hold.

FIG. 3 shows a separator 31 constituting a unit cell.
FIG. 3 is a schematic side view as viewed from the electrode side. Separator 31
A plurality of gas flow grooves 33 are arranged in parallel in a central portion facing the electrode region 32 of the first embodiment. Reaction gas supplied from outside,
That is, a fuel gas such as hydrogen or an oxidizing gas such as air is sent from an upper gas inlet 34 to an inlet manifold 35 and distributed there, and flows through a gas flow groove 33 from an upstream side to a downstream side. Then, the gas flows out from the lower gas outlet 36 to the outside.

As the polymer electrolyte membrane, a polystyrene-based cation exchange membrane having a sulfonic acid group is used as a cation conductive membrane, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or a trifluorocarbon matrix formed of trifluorocarbon. Graphite of ethylene, perfluorocarbon sulfonic acid (trade name, manufactured by Dupont, USA; Nafion membrane) and the like are used. These polymer electrolyte membranes have a proton (hydrogen ion) exchange group in the molecule, and have a specific resistance of 20 Ωcm or less at room temperature when saturated with water, and function as a proton conductive electrolyte. The saturated water content of the membrane changes reversibly with temperature.

Each of the fuel electrode and the oxidizer electrode comprises a catalyst layer and an electrode substrate supporting the catalyst layer. The catalyst layer is disposed in close contact with the solid polymer electrolyte membrane, and hydrogen as a fuel gas is supplied to the fuel electrode. When oxygen or air as an oxidant gas is supplied to the oxidant electrode, a three-phase interface is formed at the interface between each catalyst layer and the solid polymer electrolyte membrane, and the following electrical chemical reaction occurs.

[0007] _{(1) H 2 → 2H ++} 2e - ······· fuel electrode (2) 2H ++ 1 / 2O 2 + 2e - → H 2 O ···· oxidant electrode in this reaction, hydrogen and oxygen are reacted Water is produced. The catalyst layer is generally formed of a fine particulate platinum catalyst and a water-repellent fluororesin, and has pores formed so that the reaction gas can efficiently diffuse to the three-phase interface. Since the voltage generated in each cell by this reaction is about 0.7 volt, in order to increase the voltage to a practical level, as shown in FIG. Form and use.

Further, in order to keep the specific resistance of the polymer electrolyte membrane low and to keep the power generation efficiency high, it is usually used at an operating temperature of 70 to 90 ° C. As described above, in a polymer electrolyte fuel cell, the specific resistance of the polymer electrolyte membrane is reduced by saturating the polymer electrolyte membrane with water, and the membrane functions as a proton conductive electrolyte. Therefore, in order to maintain the power generation efficiency of the polymer electrolyte fuel cell, it is necessary to maintain the water-containing state of the membrane at saturation. Therefore, by supplying water to the reaction gas to increase the humidity of the reaction gas and supply it to the fuel cell, water evaporation from the membrane to the gas is suppressed,
A method for preventing drying of the film is employed.

[0009]

However, as shown by the above chemical reaction formulas (1) and (2), water is generated as a reaction product during the power generation of the fuel cell, and the water generated by the reaction is surplus. Is discharged to the outside of the fuel cell together with the reaction gas. For this reason, the amount of water contained in the reaction gas in the single cell causes a difference in the flow direction of the reaction gas, and the amount corresponding to the reaction product water on the downstream side, ie, the outlet side, compared with the upstream side, ie, the inlet side, of the reaction gas. Only a large amount of water will be contained.

[0010] For this reason, when a reaction gas humidified to a saturated state is supplied to a unit cell in order to maintain the water-containing state of the membrane in a saturated state, water vapor becomes supersaturated at the outlet side and is mixed as water droplets. As described above, when the reaction gas contains water droplets in a liquid state, the surface tension of the water is large, so that water droplets are stagnated in the gas flow grooves of the separator, which is a reaction gas flow path, and furthermore, the reaction gas is stopped. Obstructing the gas flow by blocking the gas. This tendency is remarkable on the downstream side of the separator where a large amount of water is present. As a result, there is a possibility that the supply amount of the reaction gas is insufficient or the battery characteristics are deteriorated.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object of the present invention is to efficiently remove water droplets generated in a gas flow groove as a result of a chemical reaction to the outside of a fuel cell. It is another object of the present invention to provide a polymer electrolyte fuel cell in which a reaction gas is provided to stably and uniformly flow.

[0012]

In order to solve the above-mentioned problems, a polymer electrolyte fuel cell according to the present invention comprises a hydrogen ion conductive polymer electrolyte membrane and a position interposing the hydrogen ion conductive polymer electrolyte membrane therebetween. A unit cell having a pair of electrodes arranged therein is provided with a pair of conductive members each having a gas flow passage for supplying and discharging a fuel gas containing hydrogen to one of the electrodes and supplying and discharging an oxidizing gas containing oxygen to the other. In a polymer electrolyte fuel cell stacked with a separator interposed therebetween, a protrusion made of a resist material is formed on the surface of the gas passage of the separator.

At this time, it is effective that the surface area of the convex portion made of the resist material in the gas passage increases from the upstream side to the downstream side in the gas flow direction.

It is effective that the contact angle of the resist material to water is smaller than 90 degrees.

It is effective that the convex portions are formed of different resist materials on the upstream side and the downstream side with respect to the gas flow direction.

At this time, it is effective that the contact angle of the resist material disposed on the upstream portion with water is larger than 90 degrees and the contact angle of the resist material disposed on the downstream portion with water is smaller than 90 degrees.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a single cell by arranging electrode layers on both main surfaces of an electrolyte layer comprising a polymer electrolyte membrane, and further arranging separators provided with gas flow grooves on both outer surfaces thereof. A solid polymer electrolyte type in which the unit cells are stacked to form a fuel cell stack, in which fuel gas flows through the gas flow grooves of one separator and oxidant gas flows through the gas flow grooves of the other separator. A fuel cell is characterized in that a protrusion made of a resist material is formed on the surface of a gas flow groove of a separator. According to the above configuration, since the actual surface area is increased as compared with the case where no convex portion is formed, the generated water forms a smaller contact angle with the separator surface and becomes water droplets.

This is due to the following operation. FIG. 10 (a)
FIG. 4 is a diagram showing a dynamic equilibrium state between water droplets, the surface of a flow groove, and a gas (in this case, hydrogen or oxygen) surrounding the water droplet and the flow groove when no protrusion is formed in the flow groove. When the surface energy of the flow groove surface is γs, the surface energy of the water droplet is γL, and the interfacial energy between the flow groove surface and the water droplet is γSL, the water droplet, the flow groove surface and the gas show the relationship of (Equation 1), The contact angle θ of the water droplet is determined from this equation.

On the other hand, FIG. 10 (b) is a diagram showing a dynamic equilibrium between water droplets, the surface of the flow groove, and gas when a convex portion is formed in the flow groove. Let the surface energy of the flow channel surface be γ
s, the surface energy of the water droplet is γL, the interfacial energy between the flow groove surface and the water droplet is γSL, and the ratio of the actual surface area Sb to the apparent surface area Sa represented by (Equation 3) is represented by r. The surface of the flow groove and the gas show the relationship of (Equation 2). In this state, since the surface area of the surface of the flow groove / water droplet interface and the surface area of the surface of the flow groove / gas interface become large, water droplets and the flow groove The relational expression between the surface and the gas is given by (Equation 2), and as a result, the contact angle of the water droplet is smaller than that in the case where no convex portion is formed.

[0020]

(Equation 1)

[0021]

(Equation 2)

[0022]

(Equation 3)

Due to this action, the water droplet does not grow into a water droplet enough to close the gas flow groove, but is guided along the surface of the flow groove and to a predetermined flow path without remaining in the gas flow groove. As a result, the drainage efficiency of the generated water is improved, the reactant gas flows stably, and deterioration of the performance of the polymer electrolyte fuel cell can be suppressed.

Further, the fuel cell according to the present invention is characterized in that the surface area occupied by the resist material in the gas flow grooves differs between the upstream side and the downstream side of the gas flow grooves. Although the amount of water is different between the upstream side and the downstream side of the separator as described above, it is possible to provide a contact angle suitable for efficient drainage on the upstream side and the downstream side, respectively, by the configuration,
The water droplets are guided to a predetermined flow path without staying in the flow channel, and the reaction gas flows stably, which can suppress the deterioration of the performance of the polymer electrolyte fuel cell become.

Further, the fuel cell of the present invention is characterized in that the occupied surface area of the resist material on the downstream side of the gas flow groove is larger than the occupied surface area of the resist material on the upstream side of the gas flow groove. Due to the above configuration, the water repellency is emphasized more on the upstream side, and the binding force from the surface of the flow groove is reduced, so that a small amount of water on the upstream side is efficiently carried to the downstream side, and the downstream side is described above. By the same action, the water droplets make a small contact angle with the surface of the flow groove, so a large amount of water accumulated on the downstream side spreads on the wall of the flow groove and is guided to a predetermined flow path, and the generated water is drained. The efficiency is improved, the reaction gas flows stably, and the deterioration of the performance of the polymer electrolyte fuel cell can be suppressed.

The fuel cell according to the present invention is characterized in that the contact angle of the resist material with water is smaller than 90 degrees. According to the above-described configuration, the contact angle of the water droplet becomes smaller on the downstream side according to (Equation 2), so that a large amount of water accumulated on the downstream side spreads on the wall surface and is guided to a predetermined flow path, and the generated water The drainage efficiency of the fuel cell is improved, and the reactant gas flows stably, so that deterioration of the performance of the solid polymer electrolyte fuel cell can be suppressed.

Further, in the fuel cell of the present invention, a convex portion made of the first resist material is provided on the upstream surface of the gas flow groove of the separator, and the projection is formed on the downstream surface of the gas flow groove. 2 is provided with a convex portion made of a resist material. Although the amount of water is different between the upstream side and the downstream side of the separator as described above, a contact angle suitable for efficient drainage can be given on the upstream side and the downstream side, respectively, by the above-described configuration, and water droplets flow The reaction gas is guided to a predetermined flow path without remaining in the groove, so that the reactant gas flows stably, and deterioration of the performance of the solid polymer electrolyte fuel cell can be suppressed.

At this time, the contact angle of the first resist material to water is larger than 90 degrees, and the contact angle of the second resist material to water is smaller than 90 degrees.
According to the above configuration, according to (Equation 2), the water repellency is emphasized more on the upstream side of the separator, and the binding force from the surface of the flow groove is reduced, so that a small amount of water on the upstream side is efficiently carried to the downstream side. , And on the downstream side, similarly according to (Equation 2),
Since the water droplets make a smaller contact angle with the flow groove surface, a large amount of water accumulated on the downstream side spreads on the flow groove wall surface and is guided to a predetermined flow path, improving the drainage efficiency of generated water However, the reaction gas flows stably, and the deterioration of the performance of the solid polymer electrolyte fuel cell can be suppressed.

In order to form the above-mentioned separator, the resist material is made of a negative type material. As a result, the resist on the current collecting portion located under the light shielding portion is completely uncured. Since the separator can be removed, the conductivity of the separator itself is not impaired, and a decrease in the performance of the solid polymer electrolyte fuel cell can be avoided. Then, a first step of providing a coating film of a resist material on the gas flow groove surface of the separator, and a second step of disposing a mask having a light shielding part and a light opening part in the separator in parallel.
A third step of irradiating the resist coating film with light through a mask to cure the resist, a fourth step of washing the separator and removing the uncured portion of the resist, and an electrolyte comprising a solid polymer electrolyte membrane. Placing electrode layers on both major surfaces of the layer,
And a fifth step of arranging the separators produced through the first to fourth steps on both outer sides so that the gas flow grooves of the separator face the electrode layer side. .

According to the above-described manufacturing method, a convex portion made of a resist material can be efficiently formed in the gas flow groove of the separator. This is because the resist is hardened in the area where light is irradiated through the light opening of the mask, the resist remains uncured in the area where light is blocked by the mask, and the uncured resist is completely removed by the cleaning process That is because

A first step of providing a coating of a resist material on the surface of the gas flow groove of the separator; and a second step of arranging a mask having a light shielding portion and a light opening on the separator in parallel. A third step of curing the resist by irradiating the mask and the separator with light obliquely to the resist coating film through the mask, a fourth step of cleaning the separator and removing the uncured portion of the resist, Electrode layers are arranged on both main surfaces of an electrolyte layer composed of an electrolyte membrane, and the separators produced through the first to fourth steps are placed outside both of them so that the gas flow grooves of the separator face the electrode layer side. And a fifth step of arranging the steps.

According to the above manufacturing method, it is possible to efficiently form a projection made of a resist material over the entire surface of the gas flow groove of the separator. This means that light is incident obliquely through the light opening of the mask, and light is applied not only to the vertical surface but also to the side surface as viewed from the mask side, so that light is applied to all surfaces of the flow grooves. This is because the resist material is cured over the entire surface, while the resist remains uncured in the portion where light is shielded by the mask, and the uncured resist is completely removed in the cleaning step.

Further, a first step of providing a coating film of a resist material on the gas flow groove surface of the separator, and a second step of obliquely disposing a mask having a light shielding part and a light opening part on the separator, A third step of irradiating the resist coating film with light through a mask to cure the resist, a fourth step of cleaning the separator and removing uncured portions of the resist, and an electrolyte layer comprising a solid polymer electrolyte membrane. A fifth step of arranging the electrode layer on the surface, and arranging the separator prepared through the first to fourth steps on both outer sides such that the gas flow grooves of the separator face the electrode layer side. Manufacturing method can be used.

According to the above-mentioned manufacturing method, a convex portion made of a finer resist material can be efficiently formed on the gas flow groove surface of the separator, and the drainage efficiency can be improved. This is because the mask is arranged at a constant angle with respect to the flow groove surface, so that if the angle formed between the mask and the flow groove surface is θ, the area of the optical aperture becomes COS θ times This is because the resist projections are finer and the surface area is increased as a whole.

At this time, the mask is provided with a light-shielding portion and an optical opening, and the light-shielding portion is located at the portion of the separator located at the current collector, and the light-shielding portion and the optical opening is located at the portion located at the flow groove. Arrange so that the part exists. With this configuration, since the resist is completely removed from the current collecting portion of the separator, the conductivity of the current collecting portion is not impaired, so that a decrease in battery performance due to a decrease in conductivity can be suppressed.

Further, a manufacturing method can be used in which the area occupied by the light opening or the light shielding portion in the portion located in the flow channel is different between the upstream side and the downstream side of the separator flow channel. It is characterized by the following. With this configuration, the surface area occupied by the resist material can be changed in the gas flow groove on the upstream side and the downstream side of the separator flow groove, and the water droplet does not stay in the flow groove, but reaches a predetermined flow path. Will be led,
The reaction gas flows stably, and it is possible to suppress the deterioration of the performance of the solid polymer electrolyte fuel cell.

Although the amount of water is different between the upstream side and the downstream side of the separator as described above, by adopting the above configuration, the contact angles suitable for efficient drainage are respectively formed on the upstream side and the downstream side. Because it can be given.

Further, the fuel cell according to the present invention is characterized in that the occupied area of the light opening increases from the upstream side to the downstream side of the mask. With this configuration, the surface area occupied by the resist material in the gas flow grooves of the separator can be increased from the upstream side to the downstream side of the gas flow grooves. Since the binding force from the groove surface is reduced, a small amount of water on the upstream side is efficiently carried to the downstream side,
On the downstream side, water droplets form a small contact angle with the surface of the flow groove by the same action as described above, so that a large amount of water accumulated on the downstream side spreads on the wall of the flow groove and is guided to a predetermined flow path. As a result, the drainage efficiency of the generated water is improved, the reactant gas flows stably, and deterioration of the performance of the polymer electrolyte fuel cell can be suppressed.

The fuel cell of the present invention is characterized in that the contact angle of the resist material with water is smaller than 90 degrees. According to the above configuration, according to (Equation 2), a large amount of water accumulated on the downstream side spreads on the wall surface and is guided to a predetermined flow path because the contact angle of the water droplet becomes smaller on the downstream side, and the generated water The drainage efficiency is improved, the reaction gas flows stably, and the deterioration of the performance of the polymer electrolyte fuel cell can be suppressed. In this manufacturing method, since the resist on the current collector located under the light shielding part is completely uncured by making the resist a negative type material, it can be completely removed by washing,
The conductivity of the separator itself is not impaired, and a decrease in the performance of the polymer electrolyte fuel cell can be avoided.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to clarify the configuration and operation of the present invention described above, embodiments of the present invention will be described below based on embodiments with reference to the drawings.

(Embodiment 1) First, a method of forming a separator, which is a point of this embodiment, will be described. FIG.
FIG. 3 is a conceptual diagram showing a step of providing a convex portion made of a resist material on a surface of a flow passage of a separator according to a first embodiment of the polymer electrolyte fuel cell of the present invention.

As shown in FIG. 7A, as a separator 71, a mixture of carbon powder and phenol resin was placed in a fixed mold and heated and formed under pressure. After being immersed in an alcohol-based negative resist for 1 minute, a resist coating film 72 was provided in the take-out passage. Subsequently, as shown in FIG. 7B, an optical mask 73 having a light-shielding portion and a light-transmitting portion is installed at regular intervals on the surface where the flow groove exists, and the mask is formed by using an ultra-high pressure mercury lamp as a light source. Light 74 was irradiated from the surface. Thereafter, as shown in FIG. 7C, after removing and developing the mask, the mask is washed with pure water, baked at 110 ° C., and among the side surfaces of the flow groove, the surface located perpendicular to the mask surface. A convex portion 75 made of a resist material was provided. The contact angle of the completed resist convex portion with water was measured.
Was ゜.

Next, a method of manufacturing a hydrogen ion conductive polymer electrolyte fuel cell using the above separator will be described. FIG. 4A is an exploded sectional view of a unit cell which is a component of the polymer electrolyte fuel cell according to the present embodiment, and FIG. 4B is an enlarged view schematically showing a structure of a separator passage groove. It is.

Fuel electrode 42 sandwiching polymer electrolyte membrane 41
The separator 44 having a protrusion made of a resist material on the outer surface of the separator 45 on both outer surfaces of the oxidizer electrode 43 and the passage 45 of the separator, that is, the side surface of the passage that is perpendicular to the mask surface. Is arranged so that the reaction gas flow groove 45 faces the fuel electrode 42 or the oxidant electrode 43, and is kept airtight by a gas seal body 47. In this example, a Nafion membrane (manufactured by DuPont) was used as the polymer electrolyte membrane 41.

Generally, in order to maintain the water-containing state of the polymer electrolyte membrane 41 at saturation, the moisture of the reaction gas supplied by humidification to the saturation state and the reaction water generated during power generation of the fuel cell are supersaturated. Liquefied in the state, separator 4
It is conceivable that a situation may occur in which the droplets adhere to the reaction gas flow grooves 4 as water drops. However, in this configuration, a convex portion 48 made of a resist material is provided on the surface of the flow path 45 of the reaction gas, and the surface area is increased, so that the wettability of the surface is emphasized, and the water droplet has a small contact angle. And spreads on the surface of the flow channel, so that the water droplet does not grow enough to close the gas flow groove.
Therefore, the reaction gas is guided to a predetermined flow path without remaining in the gas flow filter along the surface of the communication flow path. It will flow uniformly.

In the structure shown in FIG. 4, the unit cell is cooled by providing the cooling water flow groove 46 in the separator.
The cooling function is not limited to this, and another component other than the separator may have the cooling function.

Embodiment 2 First, a method for forming a separator will be described. FIG. 8 is a conceptual diagram showing a process of providing a convex portion made of a resist material on the surface of the flow passage of the separator prepared in this example.

First, as shown in FIG. 8A, a separator 81 prepared by mixing a mixture of carbon powder and a phenolic resin in a fixed mold and heating it under pressure is prepared. After the separator was immersed in a polyvinyl alcohol-based negative resist for 1 minute, a resist coating film 82 was provided in the takeout channel. Subsequently, as shown in FIG. 8B, an optical mask 83 having a light-shielding portion and a light-transmitting portion is provided at regular intervals on the surface where the communication channel exists, and the mask surface is formed by using an ultra-high pressure mercury lamp as a light source. , The light 84 having the incident angles of + 45 ° and −45 ° was simultaneously applied to the mask surface. Thereafter, as shown in FIG. 8C, the mask is removed,
After the development, the substrate was washed with pure water, baked at 110 ° C., and a convex portion 85 made of a resist material was provided on the entire side surface of the flow groove. When the contact angle of the completed resist convex portion with water was measured, the contact angle was 65 °.

FIG. 5A is an exploded sectional view of a unit cell which is a component of the fuel cell of this embodiment, and FIG. 5B is an enlarged view schematically showing the structure of the separator passage groove. is there.

Fuel electrode 52 sandwiching polymer electrolyte membrane 51
The separator 54 having a convex portion made of a resist material over the entire side surface of the flow channel of the separator, that is, the entire side surface of the flow channel, is provided on both outer surfaces of the oxidizer electrode 53 and the oxidizer electrode 53. Alternatively, it was arranged so as to face the oxidant electrode 53, and was kept airtight by a gas seal body 57.

In this embodiment, a Nafion membrane (manufactured by DuPont) was used as the polymer electrolyte membrane 51. In this configuration, even if a situation occurs where water droplets adhere to the reaction gas flow groove of the separator 54, a convex portion 58 made of a resist material is provided on the surface of the reaction gas flow groove 55, and the surface area increases. Because the wettability of the surface is emphasized, the water droplet spreads on the surface of the flow groove with a small contact angle, so it does not grow into a water droplet that closes the gas flow groove, and the surface of the flow groove Without being stopped in the gas flow groove, it is guided to a predetermined flow path, so that the risk of insufficient supply of the reaction gas is avoided, and the reaction gas flows stably and uniformly. In the configuration shown in FIG. 5, the unit cell is cooled by providing the cooling water flow groove 56 in the separator. However, the present invention is not limited to this. You may.

(Embodiment 3) FIG. 9 is a conceptual view showing a step of providing a projection made of a resist material on the surface of a flow groove of a separator of a fuel cell according to the present invention. As shown in FIG. 9 (a), a separator 91 prepared by mixing a mixture of carbon powder and a phenol resin into a fixed mold and heating and preparing it under pressure is prepared. After being immersed in the negative resist for one minute, a resist coating film 92 was provided in the takeout channel. Subsequently, FIG.
As shown in (b), an optical mask 93 having a light-shielding portion and a light-transmitting portion at regular intervals on the surface where the flow groove is present is installed at an angle of + 45 ° with respect to the separator and the flow groove,
Light 94 was irradiated perpendicularly to the separator and the flow channel from the mask surface using an ultrahigh pressure mercury lamp as a light source. Then, FIG.
As shown in (a), the mask was removed, developed, washed with pure water, baked at 110 ° C., and a convex portion 95 made of a resist material was provided on the entire side surface of the flow groove.

When the contact angle of the completed resist convex portion with water was measured, the contact angle was 65 °.

FIG. 6A is an exploded sectional view of a unit cell of the fuel cell of the present invention, and FIG. 6B is an enlarged view schematically showing a structure of a separator passage groove. On both outer surfaces of the fuel electrode 62 and the oxidizer electrode 63 sandwiching the polymer electrolyte membrane 61, there are convex portions made of a resist material over the entire side surface of the flow channel 65, that is, the flow channel formed according to the method described above. The separator 64 is disposed so that the reaction gas flow groove 65 faces the fuel electrode 62 or the oxidant electrode 63.
At 7 it was kept airtight.

In this embodiment, a Nafion membrane (manufactured by DuPont) was used as the polymer electrolyte membrane 61. In the present configuration, a convex portion 68 made of a resist material is provided on the surface of the reaction gas flow groove 65, and the wettability of the surface is emphasized because the surface area is increased. For this reason, the water droplet spreads on the surface of the flow groove with a small contact angle, so that the water droplet does not grow to the extent that the gas flow groove is closed, and does not stay on the gas flow groove along the flow groove surface. Is led to a predetermined flow path, so that the risk of insufficient supply of the reaction gas is avoided, and the reaction gas flows stably and uniformly. In the configuration shown in FIG. 6, the separator is provided with cooling water flow grooves 66 to cool the unit cells. However, the present invention is not limited to this, and other components other than the separator may have this cooling function. You may.

Example 4 A polymer electrolyte fuel cell was operated in exactly the same manner as in Example 1 except that the occupation ratio of the light opening in the flow passage of the separator was changed to a mask that increased toward the downstream side. Was prepared.

In this configuration, the moisture of the reactant gas supplied by humidifying the polymer electrolyte membrane to a saturated state in order to maintain the water-containing state of the polymer electrolyte in a saturated state, and the reaction water generated in the power generation of the fuel cell are in a supersaturated state. Even if a situation occurs in which water droplets adhere to the reaction gas flow grooves of the separator as a result, the water repellency is emphasized more on the upstream side, and the binding force from the flow groove surface is alleviated. A small amount of water on the side is efficiently transported downstream. At the same time, on the downstream side, water droplets form a small contact angle with the surface of the flow groove by the same action as described above, so that a large amount of water accumulated on the downstream side spreads on the flow groove wall surface and is guided to a predetermined flow path. , The drainage efficiency of the generated water is improved, and the reactant gas flows stably.

With the above effects, the risk of shortage of the supply of the reaction gas is avoided, and the reaction gas flows stably and uniformly. In this configuration, the separator is provided with a cooling water flow groove to cool the unit cells, but the present invention is not limited to this, and a separate component other than the separator may have this cooling function.

Example 5 The resist material provided in the flow passage of the separator was changed to an acrylic first resist material on the upstream side and a polyvinyl alcohol-based second resist material on the downstream side. Except for the above, a polymer electrolyte fuel cell was manufactured in exactly the same manner as in Example 1.

The contact angle of the projections of the completed resist material with water was measured to be 95 ° for the first resist material and 65 ° for the second resist material. In this configuration, the moisture of the reaction gas supplied by being humidified to a saturated state in order to maintain the water-containing state of the polymer electrolyte at saturation, and the moisture of the reaction water generated during power generation of the fuel cell are supersaturated. Even if a situation occurs in which the liquid is liquefied and adheres to the reaction gas flow grooves of the separator as water droplets, the water repellency is emphasized on the upstream side, and the binding force from the flow groove surface is reduced, A small amount of water on the upstream side is efficiently conveyed to the downstream side, and on the downstream side, water droplets form a small contact angle with the surface of the flow groove by the same action as described above. For this,
A large amount of water accumulated on the downstream side spreads on the wall of the flow channel and is led to a predetermined flow path, improving the drainage efficiency of the generated water and allowing the reaction gas to flow stably. The danger of insufficient gas supply is avoided, and the reaction gas flows stably and uniformly. In this configuration, the separator is provided with a cooling water flow groove to cool the unit cells, but the present invention is not limited to this, and a separate component other than the separator may have this cooling function.

[0061]

As described above, according to the present invention, in the polymer electrolyte fuel cell, the surface of the gas passage of the separator is
Convex portions are made of a resist material. At this time, the contact angle of the resist material to water is set to 90 ° or less, the occupied surface area of the resist material increases from the upstream side to the downstream side of the gas flow groove, and the upstream side of the gas flow groove of each separator. The first surface has a contact angle to water greater than 90 degrees
By providing a convex portion made of a second resist material having a contact angle with water of less than 90 degrees on the downstream surface of the gas flow groove, Blockage due to water droplets in the grooves is suppressed, and a solid polymer electrolyte fuel cell in which the reaction gas flows stably and uniformly can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a basic configuration of a unit cell which is a constituent element of a polymer electrolyte fuel cell.

FIG. 2 is a side view schematically showing a configuration of a fuel cell stack formed by stacking unit cells.

FIG. 3 is a schematic side view of a separator constituting a unit cell viewed from an electrode side.

FIG. 4 is a schematic diagram of a unit cell used in a polymer electrolyte fuel cell according to a first embodiment of the present invention;

FIG. 5 is a schematic view of a unit cell used in a polymer electrolyte fuel cell according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram of a unit cell used in a polymer electrolyte fuel cell according to a third embodiment of the present invention.

FIG. 7 is a conceptual diagram showing a process of forming a separator used in the first embodiment of the present invention.

FIG. 8 is a conceptual diagram showing a process of forming a separator used in a second embodiment of the present invention.

FIG. 9 is a conceptual diagram showing a process of forming a separator used in a third embodiment of the present invention.

FIG. 10 is a conceptual diagram showing the mechanical balance of water droplets on the surface of the passage of the separator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Polymer electrolyte membrane 12 Fuel electrode 13 Oxidizer electrode 14 Separator 15 Gas passage 16 Cooling water passage 17 Gas seal 21 Cell 22 Current collector 23 Insulating plate 24 Tightening plate 25 Tightening bolt 26 Disc spring 27 Tightening With nut 31 Separator 32 Electrode area 33 Gas passage 34 Gas inlet 35 Manifold 36 Gas outlet 41 Polymer electrolyte membrane 42 Fuel electrode 43 Oxidant electrode 44 Separator 45 Gas passage 46 Cooling water passage 47 Gas seal body 48 Resist convex part 51 Polymer electrolyte membrane 52 Fuel electrode 53 Oxidant electrode 54 Separator 55 Gas flow groove 56 Cooling water flow groove 57 Gas seal body 58 Resist convex part 61 Polymer electrolyte membrane 62 Fuel electrode 63 Oxidant electrode 64 Separator 65 Gas flow groove 66 Cooling water flow path 67 Gas seal body 68 Resist convex part 7 REFERENCE SIGNS LIST 1 communication channel 72 resist coating 73 resist projection 74 mask 75 light 81 separator communication channel 82 resist coating 83 resist projection 84 mask 85 light 91 separator communication channel 92 resist coating 93 resist projection 94 mask 95 light 101 flow channel surface 102 water drop 103 gas 104 convex part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-22537 (JP, A) JP-A-3-205576 (JP, A) JP-A-7-235324 (JP, A) JP-A 8- JP 138692 (JP, A) JP-A-11-97041 (JP, A) JP-A-11-195422 (JP, A) JP-A 2000-36309 (JP, A) JP-A 2001-6708 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) H01M 8/02 H01M 8/10

Claims (5)

(57) [Claims] 1. A unit cell comprising a hydrogen ion conductive polymer electrolyte membrane and a pair of electrodes disposed at a position sandwiching the hydrogen ion conductive polymer electrolyte membrane. In a polymer electrolyte fuel cell stacked and disposed via a pair of conductive separators that supply and discharge a gas and supply and discharge an oxidizing gas containing oxygen to the other, in the gas flow path of the separator, A polymer electrolyte fuel cell, wherein a convex portion made of a resist material is formed on the surface. 2. The gas flow path according to claim 1, wherein the surface area of the projection made of the resist material increases from the upstream side to the downstream side in the gas flow direction. Polymer electrolyte fuel cell. 3. The polymer electrolyte membrane fuel cell according to claim 1, wherein the contact angle of the resist material to water is smaller than 90 degrees. 4. The polymer electrolyte membrane fuel cell according to claim 1, wherein the convex portions are formed of different resist materials on the upstream side and the downstream side with respect to the gas flow direction. 5. The method according to claim 4, wherein the contact angle of the resist material disposed on the upstream portion to water is larger than 90 degrees, and the contact angle of the resist material disposed on the downstream portion to water is smaller than 90 degrees. Polymer electrolyte fuel cell.