JP2007305532A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell enhancing drainage efficiency, efficiently supplying fuel or an oxidant, and enhancing power generation efficiency. <P>SOLUTION: The fuel cell has passages for supplying fuel or an oxidant on both sides of an electrolyte membrane, a diffusion member made of a porous medium is installed in at least one part in the passage, the diffusion member made of the porous medium has a water repellent tendency in which a contact angle to water is larger than 90°, and when the positions of the diffusion member at two points where the distances in the direction parallel to the electrolyte membrane form the inlet of the passage are different are represented by x1 and x2, and porosities of the diffusion members in x1 and x2 by p(x1) and p(x2), and the relation of porosities at two points where the distances from the inlet are different is x1<x2, relation of p(x1)>p(x2) is satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell having improved gas diffusion in a flow path when fuel and an oxidant are supplied.

  A typical cross-sectional shape of a polymer electrolyte fuel cell is shown in FIG. The solid polymer fuel cell has a solid polymer electrolyte membrane 5 in the center. The fuel electrode is supplied to one side of the fuel and serves as an anode, and the other side is provided with an oxidant electrode that is supplied with an oxidant and serves as a cathode. These configurations are generally collectively MEA (Mebrane Electrode Assembly). Called. Furthermore, each electrode has diffusion layers 3 and 6 for diffusing fuel or oxidant outside the electrolyte membrane 5 and collecting generated electric power, and further supplying fuel or oxidant outside thereof. There are flow paths 2 and 7 for this purpose. 1 is a separator on the cathode side, 4 is a seal, 8 is a separator on the anode side, 9 is a seal to prevent leakage of hydrogen, 10 is an inlet for oxygen containing oxygen as an oxidizing agent, and 11 is a supply port for hydrogen. To express.

  The diffusion layer 3 or 6 is generally made of, for example, carbon cloth as a conductive porous medium. In addition, a porous medium having a high porosity may be used as a support member in the flow path 2 or 7 as well.

The fuel or the oxidant is forcibly supplied in the flow paths 2 and 7 using, for example, a pressure gradient, diffuses through the diffusion layers 3 and 6, and reaches the anode or the cathode, respectively.
At the anode, the fuel that has reached is oxidized by the oxidizing action of the catalyst of the anode to become protons, and moves in the polymer electrolyte membrane toward the cathode. As this fuel, a gas such as hydrogen or a liquid such as methanol or ethanol is used.

  At the cathode, the oxidant, for example, oxygen that has reached through the diffusion layer from the oxidant flow path, and the proton that has moved through the electrolyte membrane react with the oxidant to generate water. A part of the energy is extracted as electric energy by this series of chemical reactions.

  As described above, water is generated by the power generation reaction at the cathode. This water usually becomes steam or water droplets, moves from the oxidant diffusion layer to the flow path, and is discharged. In some cases, the MEA may pass through and be discharged from the anode side. At this time, when the fuel or oxidant is supplied using a pressure gradient, water is also moved together with the fuel or oxidant and discharged from the discharge port.

  In general, since a single fuel cell cannot obtain sufficient power, it has a stack structure in which several of the above-described structures (cells) 12 are stacked in series as shown in FIG. This type of fuel cell is attracting attention mainly as a power source for automobiles that replace gasoline, and as a cogeneration application for business use or home use.

  Furthermore, in recent years, it is expected to be used as a battery for portable electronic devices such as notebook computers and PDAs (Personal Digital Assistants), and the development is being promoted. In this case, the fuel cell itself must be extremely miniaturized, and therefore a control mechanism such as a fuel or oxidizer supply device using a pressure gradient may not be used. In such a case, the fuel and oxidant must be supplied by diffusion or natural convection.

  For example, Patent Document 1 discloses a technology of a passive fuel cell that supplies oxygen as an oxidizing agent by natural diffusion. FIG. 4 in Patent Document 1 is a diagram showing the cell structure. Oxygen as an oxidant diffuses through the diffusion cell unit 39 and reaches the MEA 55. Further, hydrogen as a fuel is supplied from 58 and reaches the MEA 55.

  As a feature of such a passive fuel cell, oxygen is supplied from the oxidant inlet using a concentration gradient, and at the same time, water vapor needs to be discharged from the same place by the concentration gradient. In general, since oxygen in the air is used as an oxidizing agent, this portion is opened to the atmosphere. In the case of such a passive fuel cell, a design philosophy different from that of a fuel cell in which other flow path inlets and outlets can be clearly defined is required.

  In particular, in the passive fuel cell, there is no control mechanism for moving and discharging the fuel gas that could not be reacted actively in the moisture discharge mechanism and the moisture generated by the reaction. Therefore, as described above, not only the fuel and the oxidant are supplied by natural diffusion, but also a mechanism for draining naturally must be provided.

  In addition, when there is a forced circulation mechanism, the supply port for supplying fuel or oxidant and the discharge port for discharging water or water vapor are clearly separated, but in the case of passive fuel cells, they are the same There is also a possibility. For example, in Patent Document 1, the supply port for supplying oxygen as an oxidizing agent and the discharge port for discharging moisture generated by the reaction are the same.

In such a case, in order to reduce the size of the fuel cell, a mechanism for efficiently supplying oxygen as an oxidant and efficiently discharging moisture is required. Patent document 2 is mentioned as an example for discharging | emitting a water | moisture content efficiently. In Patent Document 2, moisture is easily discharged by using a configuration in which the diffusivity in the downstream region of the diffusion layer is made larger than that in the upstream region. However, this method requires a system that forcibly circulates fuel or oxidant, and cannot be applied to a passive fuel cell as it is.
US Pat. No. 6,423,437 JP 2004-273392 A

  In the passive fuel cell in which the fuel or oxidant is mainly supplied by natural diffusion, the present invention improves drainage efficiency by installing a diffusion member made of a porous medium having a different porosity in the flow path, A fuel cell capable of efficiently supplying fuel or an oxidant and having high power generation efficiency is provided.

In a first fuel cell for solving the above problems, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is greater than 90 degrees and tends to be water repellent, and two or more types of diffusion members are continuously installed in a direction parallel to the electrolyte membrane, In addition, the porosity of each diffusion member in the direction parallel to the electrolyte membrane from the inlet of the flow path is the porosity of the diffusion member disposed at a position close to the inlet of the flow path. It is characterized by being larger than the porosity of the diffusing member disposed at a relatively far position.

In a second fuel cell for solving the above problems, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The diffusing member at two points where the contact angle with respect to water of the diffusing member made of the porous medium is greater than 90 degrees and has a water repellent tendency, and the distance in the parallel direction from the inlet of the flow path is different. Are x1 and x2, and the porosity of the diffusion member at x1 and x2 is p (x1) and p (x2), the relationship between the porosity at two points with different distances from the inlet is x1. When <x2, the relationship p (x1)> p (x2) is satisfied.

In a third fuel cell for solving the above problem, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is greater than 90 degrees and tends to be water-repellent, and two or more types of diffusion members are continuously installed in a direction perpendicular to the electrolyte membrane, In addition, the porosity of each diffusion member installed in the direction perpendicular to the electrolyte membrane in the flow path is such that the porosity of the diffusion member disposed at a position close to the electrolyte membrane is higher than that of the diffusion member. It is characterized by being smaller than the porosity of the diffusion member disposed at a relatively distant position.

In a fourth fuel cell for solving the above problem, an anode and a cathode are formed on both surfaces of the electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The position of the diffusing member at two points where the contact angle with respect to the water of the diffusing member made of the porous medium is greater than 90 degrees and tends to be water repellent and the distance in the vertical direction to the electrolyte membrane of the flow path is different. When y1 and y2 are y and the porosity of the diffusion member in y1 and y2 is p (y1) and p (y2), the relationship between the porosity at two points with different distances from the electrolyte membrane is y1> y2 In this case, the relationship p (y1)> p (y2) is satisfied.

In a fifth fuel cell for solving the above problems, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is less than 90 degrees and tends to be hydrophilic, and two or more types of diffusion members are continuously installed in a direction parallel to the electrolyte membrane, and The porosity of each diffusing member in the direction parallel to the electrolyte membrane from the inlet of the flow path is such that the porosity of the diffusing member disposed near the inlet of the flow path is more than that of the diffusing member. A fuel cell characterized by being smaller than the porosity of a diffusion member disposed at a relatively far position.

In a sixth fuel cell for solving the above problems, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The diffusion member made of the porous medium has a contact angle with water of less than 90 degrees and tends to be hydrophilic, and the diffusion member has two different distances from the inlet of the flow path in the parallel direction. Assuming that the positions are x11 and x21, and the porosity of the diffusion member at x11 and x21 is p (x11) and p (x21), the relationship between the porosity at two points with different distances from the inlet is x11 < When x21, the relationship of p (x11) <p (x21) is satisfied.

In a seventh fuel cell for solving the above problems, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is less than 90 degrees and tends to be hydrophilic, and two or more types of diffusion members are continuously installed in a direction perpendicular to the electrolyte membrane, and The porosity of each diffusion member installed in the direction perpendicular to the electrolyte membrane in the flow path is such that the porosity of the diffusion member disposed at a position close to the electrolyte membrane is relatively higher than that of the diffusion member. It is characterized by being larger than the porosity of the diffusion member disposed at a far position.

In an eighth fuel cell for solving the above problem, an anode and a cathode are formed on both surfaces of an electrolyte membrane, fuel is supplied to the anode side, an oxidant is supplied to the cathode side, and the fuel and the oxidant are reacted. In a fuel cell that generates electric power by
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The position of the diffusing member at two points where the contact angle with respect to the water of the diffusing member made of the porous medium is less than 90 degrees and tends to be hydrophilic and the distance in the direction perpendicular to the electrolyte membrane of the flow path is different is y11. And y21, and the porosity of the diffusion member at y11 and y21 is p (y11) and p (y21), the relationship between the porosity at two points with different distances from the electrolyte membrane is y11> y21 In some cases, the relationship p (y11) <p (y21) is satisfied.

  In the passive fuel cell according to the present invention, by installing a diffusion member made of a porous medium having a different porosity in the flow path, drainage efficiency is improved, and fuel or oxidant can be efficiently supplied. A fuel cell with good power generation efficiency can be provided.

The present invention will be described below.
The present invention efficiently supplies fuel or oxidant to a catalyst layer by discharging water generated by power generation, particularly liquefied water, in a passive fuel cell that mainly supplies fuel or oxidant by natural diffusion. To do.

  Specifically, a diffusion member made of a porous medium having a different porosity is installed in the flow path at a location where water generated by the power generation of the fuel cell is liquefied, and the change in the porosity causes the droplet to A driving force (driving force) is generated, and the droplets are discharged.

  Specifically, (1) When the contact angle of the diffusion member made of a porous medium with respect to water is greater than 90 degrees and tends to be water-repellent, the porosity of the diffusion member is set in a horizontal direction with respect to the solid electrolyte membrane. On the other hand, it is preferable to decrease the distance from the fuel or oxidant inlet and to increase the distance from the electrolyte membrane in the direction perpendicular to the solid electrolyte membrane. (2) When the contact angle with respect to water of the diffusion member made of a porous medium is less than 90 degrees and tends to be hydrophilic, the porosity of the diffusion member is a fuel in a direction parallel to the solid electrolyte membrane. Alternatively, it is preferable to increase the distance from the inlet of the oxidant and to decrease the distance from the electrolyte membrane in the direction perpendicular to the solid electrolyte membrane.

Next, an embodiment of the present invention will be described.
A cross-sectional structure of a rectangular parallelepiped fuel cell as shown in FIG. 1 is shown as a model of a passive small fuel cell. Hydrogen is supplied in the vertical direction on the anode side, and air containing oxygen as an oxidant is supplied in the horizontal direction on the cathode side. On the anode side, hydrogen undergoes an oxidation reaction and becomes protons and moves to the cathode side. On the cathode side, protons and oxygen react to produce water. This difference in energy becomes electric power and is supplied to the device connected to the fuel cell.

  The generated water becomes water vapor and is discharged outside through the path through which oxygen has passed. However, some water vapor liquefies and stays in the cell. This staying water eventually obstructs the supply of fuel or oxidant and makes the fuel cell not function (flooding phenomenon). Therefore, a separate mechanism for discharging the droplets out of the cell is necessary.

  In the case of a fuel cell having a system for forcibly circulating fuel or oxidant, it is possible to forcibly exclude the droplets in the flow path by a pressure gradient. However, in the case of a passive type fuel cell, since there is no driving force for liquid, there is no choice but to expect droplets to vaporize and be discharged by diffusion. For this reason, there is a problem that it is difficult to remove droplets generated at a location far from the entrance.

Therefore, as a mechanism for actively discharging water, there is a method of changing the porosity of a porous medium disposed in a flow path to give a driving force.
The movement of the liquid in the porous medium depends on a gradient such as a contact angle and a porosity of the porous medium. In general, the capillary pressure (capillary pressure / capillary pressure) Pc of a liquid in a porous medium increases as the porosity decreases, particularly when it tends to be hydrophobic, and increases as the porosity increases when it tends to be hydrophilic. . (C. Y. Wang, P. Cheng, “Adv. Heat Transfer”, 30 (1997) p. 93).

By utilizing the gradient of the capillary pressure Pc for the driving force that moves the droplet, a mechanism for discharging the droplet can be created.
The specific configuration in the present invention is roughly divided into two. One is a configuration in the direction parallel to the solid electrolyte surface for guiding the droplets to the discharge hole, and the other is to keep the droplets away from the solid electrolyte surface to prevent the droplets from flooding. The configuration is perpendicular to the direction.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
A configuration for moving droplets in a direction horizontal to the solid electrolyte surface will be described. In this case, it is important that water is efficiently guided outside as described above. For this purpose, it is desirable that the porosity of the diffusion member is as large as the porosity near the entrance.

In the following examples, the cathode is all described, but the same configuration is also effective when draining water at the anode.
FIG. 2 is a schematic view showing an embodiment of the fuel cell of the present invention. FIG. 2 shows a case where the contact angle of the diffusion member made of a porous medium with respect to water is larger than 90 degrees and tends to be water repellent. FIG. 2 shows a case in which two or more types of diffusion members made of a porous medium and having different porosity are continuously installed in the direction parallel to the electrolyte membrane in the cathode flow path in the configuration of FIG. It is.

  Usually, nothing is arranged in the flow path or a porous medium having a high porosity is used, but in this example, a porous member subjected to hydrophobic treatment was used in the flow path. In addition, gradation was applied so that the porosity of the porous member was maximized near the entrance.

  In this case, the water droplets in the porous medium are subjected to a driving force by capillary pressure due to the influence of hydrophobicity. It receives driving force and is directed toward the inlet of the flow path. By applying a strong hydrophobic treatment and taking a large difference in porosity, the driving force increases and the liquid can be discharged more efficiently.

The same configuration can also be applied to the gas diffusion layer.
Example 2
In order to achieve efficient liquid discharge, it is most desirable to provide gradation to the water repellency of the porous medium of the diffusion member as described in the first embodiment, but such a configuration cannot be adopted. In some cases, there are methods of joining several porous media having different porosity.

  FIG. 3 is a schematic view showing an embodiment of the fuel cell of the present invention. FIG. 3 shows a case where the contact angle of the diffusion member made of a porous medium with respect to water is larger than 90 degrees and tends to be water repellent. FIG. 3 shows a case where two types of diffusion members made of a porous medium and having different porosity are installed in a direction parallel to the electrolyte membrane in the cathode flow path in the configuration of FIG.

  Diffusion near the inlet by changing the porosity of the diffusion member 1 at the position x1 close to the inlet of the flow path p (x1)) and the porosity of the diffusion member 2 at the far position x2 (p (x2)) Driving at the interface between the two diffusion members by satisfying the relationship of p (x1)> p (x2) so that the porosity of the member 1 is larger than the porosity of the distant diffusion member 2 Force is generated. As a result of the liquid droplets being guided even closer to the inlet, the drainage efficiency is improved compared with the first embodiment, although it is inferior.

  That is, the minimum constituent factor of the present invention is the distance x from the inlet when the diffusion member is a porous medium in the flow path or gas diffusion layer and the diffusion member is water repellent. When the porosity of a part is P (x), if two positions are x1 <x2, there is a configuration in which p (x1)> p (x2) exists at least in one place. .

Example 3
In general, a water-repellent member is used for the gas diffusion layer. This is intended to efficiently drain moisture. However, there is also a method in which a hydrophilic porous member is installed in the flow path portion adjacent to the gas diffusion layer in order to discharge moisture more efficiently.

  Thus, when installing a hydrophilic member, the relationship between the gradation of porosity and the direction of the driving force is reversed. That is, the liquid is guided toward the lower porosity. In this case, in order to improve drainage, it is better that the air efficiency at the air intake port is relatively smaller than the depth.

  FIG. 4 is a schematic view showing an embodiment of the fuel cell of the present invention. FIG. 4 shows a case where the diffusing member made of a porous medium has a hydrophilic tendency that the contact angle with respect to water is smaller than 90 degrees. FIG. 4 shows a case where two or more types of diffusion members made of a porous medium and having different porosity are continuously installed in a direction parallel to the electrolyte membrane in the cathode flow path in the configuration of FIG. It is.

In FIG. 4, when two hydrophilic members are combined and continuously arranged in the flow path, the porosity of the diffusion member at a position far from the inlet is increased.
Example 4
In order to achieve efficient liquid discharge, it is most desirable to impart gradation to the hydrophilicity of the porous medium of the diffusion member as described in Example 3, but such a configuration cannot be adopted. In some cases, there are methods of joining several porous media having different porosity.

  FIG. 5 is a schematic view showing an embodiment of the fuel cell of the present invention. FIG. 5 shows a case where the diffusing member made of the porous medium has a hydrophilic tendency that the contact angle with respect to water is smaller than 90 degrees. FIG. 5 shows a case where two types of diffusion members made of a porous medium and having different porosity are installed in a direction parallel to the electrolyte membrane in the cathode flow path in the configuration of FIG.

  Diffusion near the inlet by changing the porosity of the diffusion member 1 at the position x11 close to the inlet of the flow path to p (x11)) and the porosity of the diffusion member 2 at the far position x21 (p (x21)) Driving at the interface between the two diffusion members by satisfying the relationship of p (x11) <p (x21) so that the porosity of the diffusion member 11 is smaller than the porosity of the distant diffusion member 21. Force is generated. Although the liquid droplets are guided to a position closer to the inlet as much as possible, the drainage efficiency is improved although it is inferior to that of the third embodiment.

  That is, the minimum constituent factor of the present invention is the distance x from the inlet when the diffusion member is made of a porous medium in the flow path or gas diffusion layer and the diffusion member is hydrophilic. In the case where the porosity of the location is P (x), if the two positions are x11 <x21, there is a configuration where p (x11) <p (x21) exists in at least one location. .

Example 5
Examples 1 to 4 are cases in which diffusion members made of a porous medium and having different porosity are installed in a direction parallel to the electrolyte membrane. In this example, the porosity of the porous medium is low. This is a case where different diffusion members are installed in a direction perpendicular to the electrolyte membrane.

  In this case, the important thing is to apply a driving force so that moisture generated and liquefied by the catalyst is quickly moved away from the catalyst layer. There are several previous examples of such examples. For example, Japanese Patent Application Laid-Open No. 2003-173789 discloses a technique in which the porosity of the gas diffusion layer is increased on the side opposite to the catalyst layer so that excessive moisture does not stay in the electrode catalyst layer. However, this document is a technique for the gas diffusion layer, and does not mention water discharged to the flow path.

  However, in the case of a small fuel cell, it is desirable to have a similar configuration in the flow path. The reason is that if the moisture produced from the gas diffusion layer stays on the surface opposite to the catalyst layer, a “flooding phenomenon” occurs as a result.

  FIG. 6 is a schematic view showing an embodiment of the fuel cell of the present invention. FIG. 6 shows a case where the contact angle of the diffusion member made of a porous medium with respect to water is greater than 90 degrees and tends to be water repellent. FIG. 6 shows a case where two or more types of diffusion members made of a porous medium and having different porosity are continuously installed in the cathode flow path in the configuration of FIG. 1 in a direction perpendicular to the electrolyte membrane. It is.

  For this purpose, as shown in FIG. 6, the diffusion member has a gradation in which the porosity is small at a position close to the electrolyte membrane of the MEA and large at a position far from the electrolyte membrane. That is, a diffusion member that has been processed so that the porosity of the diffusion member is small on the side close to the MEA and the porosity increases as the distance increases.

As a result, a driving force from the electrolyte membrane to the flow path is generated for the liquid droplet, the liquid droplet is guided to the flow path, and flooding is avoided.
Example 6
FIG. 7 shows a method of providing two or more types of diffusion members in the flow path.

  FIG. 7 is a schematic view showing another embodiment of the fuel cell of the present invention. FIG. 7 shows a case where the contact angle of the diffusion member made of a porous medium with respect to water is larger than 90 degrees and tends to be water repellent. FIG. 7 shows a case where two types of diffusion members made of a porous medium and having different porosity are installed in a direction perpendicular to the electrolyte membrane in the flow path of the cathode.

The porosity of the two types of diffusion members is set to be small at a position close to the MEA electrolyte membrane and large at a position far from the electrolyte membrane.
The porosity (p (y2)) of the diffusing member 2 at the position y2 close to the electrolyte membrane and the porosity (p (y1)) of the diffusing member 1 at the far position y1 are changed (y1> y2). Driving force is generated at the interface between the two members by satisfying the relationship of p (y1)> p (y2) so that the contact angle of the diffusing member with respect to water becomes smaller.

  That is, as a minimum constituent factor of the present invention, in the diffusion member made of a porous medium in the flow path or the gas diffusion layer, and when the diffusion member is water repellent, the diffusion member becomes the electrolyte membrane. On the other hand, in the case where the porosity at a position at a distance of y in the vertical direction is P (y), if two positions are y1> y2, then p (y1)> p (y2) Exists in at least one place.

Example 7
In general, a water-repellent member is used for the gas diffusion layer. This is intended to efficiently drain moisture. However, there is also a method in which a hydrophilic porous member is installed in the flow path portion adjacent to the gas diffusion layer in order to discharge moisture more efficiently.

  Thus, when installing a hydrophilic member, the relationship between the gradation of porosity and the direction of the driving force is reversed. That is, the liquid is guided toward the lower porosity. In this case, in order to improve drainage, it is better that the air efficiency at the air intake port is relatively smaller than the depth.

  FIG. 8 is a schematic view showing one embodiment of the fuel cell of the present invention. FIG. 8 shows a case where the diffusing member made of a porous medium has a hydrophilic tendency that the contact angle with respect to water is smaller than 90 degrees. FIG. 8 shows a case where two or more kinds of diffusion members made of a porous medium and having different porosity are continuously installed in a direction perpendicular to the electrolyte membrane in the cathode flow path in the configuration of FIG. It is.

In FIG. 8, when two hydrophilic members are combined and continuously arranged in the flow path, the porosity of the diffusion member at a position far from the electrolyte membrane is reduced.
Example 8
In order to achieve efficient liquid discharge, it is most desirable to impart gradation to the hydrophilicity of the porous medium of the diffusing member as described in Example 7, but such a configuration cannot be adopted. In some cases, there are methods of joining several porous media having different porosity.

  FIG. 9 is a schematic view showing one embodiment of the fuel cell of the present invention. FIG. 9 shows a case where the diffusing member made of a porous medium has a hydrophilic tendency where the contact angle with respect to water is smaller than 90 degrees. FIG. 9 shows a case where two types of diffusion members made of a porous medium and having different porosity are installed in the cathode channel in the direction perpendicular to the electrolyte membrane.

  The porosity (p (y21)) of the diffusing member 21 at the position y21 close to the electrolyte membrane and the porosity (p (y11)) of the diffusing member 11 at the distant position y11 are changed (y11> y21) to be far Driving force is generated at the interface between the two members by satisfying the relationship of p (y11) <p (y21) so that the contact angle of the diffusion member at the position with respect to water becomes smaller.

  That is, as a minimum constituent factor of the present invention, in the diffusion member made of a porous medium in the flow path or the gas diffusion layer, and when the diffusion member is hydrophilic, the diffusion member becomes the electrolyte membrane. On the other hand, in the case where the porosity at a position at a distance of y in the vertical direction is P (y), if the two positions are y11> y21, then p (y11) <p (y21). Exists in at least one place.

  According to the present invention, by installing a diffusion member made of a water-repellent or hydrophilic porous medium having different porosity in the flow path, drainage efficiency is improved and fuel or oxidant can be efficiently supplied. Furthermore, it can be used for a passive fuel cell with good power generation efficiency.

It is sectional drawing which shows the cross-section of a rectangular parallelepiped fuel cell. It is the schematic which shows one Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is the schematic which shows the other Example of the fuel cell of this invention. It is sectional drawing which shows the structure of the cross-sectional shape of the conventional polymer electrolyte fuel cell. It is the schematic which shows the structure which laminated | stacked the fuel battery cell in series.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Flow path 3 Diffusion layer 4 Seal member 5 Electrolyte membrane 6 Diffusion layer 7 Flow path 8 Separator 9 Seal member 10 Air intake 11 Hydrogen supply port 12 Cell

Claims (8)

In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is greater than 90 degrees and tends to be water repellent, and two or more types of diffusion members are continuously installed in a direction parallel to the electrolyte membrane, In addition, the porosity of each diffusion member in the direction parallel to the electrolyte membrane from the inlet of the flow path is the porosity of the diffusion member disposed at a position close to the inlet of the flow path. A fuel cell characterized by being larger than the porosity of a diffusion member disposed at a relatively far position. In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The diffusing member at two points where the contact angle with respect to water of the diffusing member made of the porous medium is greater than 90 degrees and has a water repellent tendency, and the distance in the parallel direction from the inlet of the flow path is different. Are x1 and x2, and the porosity of the diffusion member at x1 and x2 is p (x1) and p (x2), the relationship between the porosity at two points with different distances from the inlet is x1. A fuel cell characterized by satisfying a relationship of p (x1)> p (x2) when <x2. In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is greater than 90 degrees and tends to be water-repellent, and two or more types of diffusion members are continuously installed in a direction perpendicular to the electrolyte membrane, In addition, the porosity of each diffusion member installed in the direction perpendicular to the electrolyte membrane in the flow path is such that the porosity of the diffusion member disposed at a position close to the electrolyte membrane is higher than that of the diffusion member. A fuel cell characterized by being smaller than the porosity of a diffusion member disposed at a relatively distant position. In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The position of the diffusing member at two points where the contact angle with respect to the water of the diffusing member made of the porous medium is greater than 90 degrees and tends to be water repellent and the distance in the vertical direction to the electrolyte membrane of the flow path is different. When y1 and y2 are y and the porosity of the diffusion member in y1 and y2 is p (y1) and p (y2), the relationship between the porosity at two points with different distances from the electrolyte membrane is y1> y2 And satisfying the relationship of p (y1)> p (y2). In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is less than 90 degrees and tends to be hydrophilic, and two or more types of diffusion members are continuously installed in a direction parallel to the electrolyte membrane, and The porosity of each diffusing member in the direction parallel to the electrolyte membrane from the inlet of the flow path is such that the porosity of the diffusing member disposed near the inlet of the flow path is more than that of the diffusing member. A fuel cell characterized by being smaller than the porosity of a diffusion member disposed at a relatively far position. In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The diffusion member made of the porous medium has a contact angle with water of less than 90 degrees and tends to be hydrophilic, and the diffusion member has two different distances from the inlet of the flow path in the parallel direction. Assuming that the positions are x11 and x21, and the porosity of the diffusion member at x11 and x21 is p (x11) and p (x21), the relationship between the porosity at two points with different distances from the inlet is x11 < When x21, the fuel cell satisfies the relationship of p (x11) <p (x21). In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is continuously installed in at least one place in the flow path. ,
The contact angle with respect to water of the diffusion member made of the porous medium is less than 90 degrees and tends to be hydrophilic, and two or more types of diffusion members are continuously installed in a direction perpendicular to the electrolyte membrane, and The porosity of each diffusion member installed in the direction perpendicular to the electrolyte membrane in the flow path is such that the porosity of the diffusion member disposed at a position close to the electrolyte membrane is relatively higher than that of the diffusion member. A fuel cell characterized by being larger than the porosity of a diffusion member arranged at a far position. In the fuel cell in which the anode and the cathode are formed on both surfaces of the electrolyte membrane, the fuel is supplied to the anode side, the oxidant is supplied to the cathode side, and the fuel and the oxidant are respectively reacted to generate electric power.
The fuel cell has a flow path for supplying fuel or an oxidant on both sides of the electrolyte membrane, and a diffusion member made of a porous medium is installed in at least one place in the flow path,
The position of the diffusing member at two points where the contact angle with respect to the water of the diffusing member made of the porous medium is less than 90 degrees and tends to be hydrophilic and the distance in the direction perpendicular to the electrolyte membrane of the flow path is different is y11. And y21, and the porosity of the diffusion member at y11 and y21 is p (y11) and p (y21), the relationship between the porosity at two points with different distances from the electrolyte membrane is y11> y21 In some cases, the fuel cell satisfies the relationship of p (y11) <p (y21).

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