JP2001229937A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell, capable of quickly draining a water produced in a supply flow passage for a fuel gas and an oxidizer gas, and which is superior in productivity. SOLUTION: The fuel cell comprises an electrolyte layer, an electrode layer, holding the electrolyte layer counterposed and a flow passage forming member for holding counterposed a laminate of the electrolyte layer and the electrode layer to form the flow passage for the fuel gas and the oxidizer gas in a space to the electrode layer. A photocatalyst layer, having hydrophilic property, is provided on the face of the flow passage forming member where the flow passage is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly to a fuel cell comprising an electrolyte layer, a plurality of electrode layers sandwiching the electrolyte layer, and a laminate comprising the electrolyte layer and the electrode layer sandwiching the electrode layer. And a flow path forming member that forms a flow path for a fuel gas or an oxidizing gas therebetween.

[0002]

2. Description of the Related Art In a polymer electrolyte fuel cell, a fuel gas containing hydrogen and an oxidizing gas containing oxygen are supplied to a fuel electrode and an air electrode which face each other with an electrolyte layer interposed therebetween. A chemical reaction is performed to generate power.
In order to carry out the above reaction continuously and smoothly, it is necessary to continuously supply the fuel gas to the fuel electrode and to diffuse hydrogen ions generated at the fuel electrode into the electrolyte layer. The hydrogen ions move along the electrolyte layer from the fuel electrode side to the air electrode side together with water, so that the fuel gas is humidified to replenish moisture. For this reason, depending on the operation state, water vapor may condense on the surface on which the fuel gas supply flow path is formed and adhere as water droplets, thereby obstructing the flow of the fuel gas. Therefore, it is necessary to quickly drain the condensed water droplets from the fuel gas supply channel. Further, in the air electrode, it is necessary to quickly discharge water generated by the reaction and continuously supply the oxidant gas to the air electrode.

In order to solve such a problem, a water-repellent fluororesin film is formed on the surface on which the fuel gas or oxidizing gas supply flow path is formed, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-2462. Things have been suggested. However, in this method, a plurality of water droplets collect in the supply flow path to generate large water drops, which may hinder the supply of the fuel gas or the oxidizing gas, or the case where the supply flow path is blocked by the surface tension of the water. It has been pointed out that there is. In order to solve this problem, for example, Japanese Unexamined Patent Application Publication No.
In Japanese Patent Laid-Open Publication No. H11-264, there is proposed a technique in which a plurality of short fibers made of carbon are planted on a surface on which a fuel gas or oxidant gas supply flow path is formed. This short carbon fiber causes hydrophilicity on the surface on which the supply flow path is formed, thereby preventing generation of large water droplets.

[0004]

However, in such a fuel cell in which a plurality of short carbon fibers are planted, it is very troublesome to attach the short carbon fibers, which leads to a serious problem of lowering productivity and increasing costs. was there. The present invention has been made in view of the problems of the related art, and an object of the present invention is to provide a fuel cell that can quickly discharge water generated in a fuel gas and an oxidizing gas supply channel and that has excellent productivity. .

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, a fuel cell according to claim 1 is provided.
An electrolyte layer, a plurality of electrode layers sandwiching the electrolyte layer, and a flow forming a flow path of a fuel gas or an oxidizing gas between the electrode layer and a laminate of the electrolyte layer and the electrode layer. And a passage forming member, wherein a photocatalytic layer having hydrophilicity is provided on a surface of the passage forming member on which the passage is formed.

[0006] A fuel cell according to a second aspect is characterized in that it has a means for irradiating the photocatalyst layer with ultraviolet rays. Since the hydrophilicity of the photocatalyst is excited by irradiating ultraviolet rays, the hydrophilicity can be restored and maintained for a long period of time by separately providing a means for irradiating ultraviolet rays.

The means for irradiating the ultraviolet rays is preferably an optical fiber provided in the flow path of the flow path forming member or a luminous agent. Preferably, the optical fiber is detachable.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of a polymer electrolyte fuel cell showing one embodiment of the present invention. The electrode layer 2 is arranged so as to sandwich the electrolyte layer 1 in opposition. Further, the flow path forming member 3 is disposed so as to sandwich the laminate 10 of the electrolyte layer 1 and the electrode layer 2 so as to face each other (only one of the flow path forming members 3 is shown). In the flow path forming member 3, a supply flow path 4 for a fuel gas or an oxidizing gas is formed. The supply flow path 4 is generally formed by forming multiple grooves on the surface of the flow path forming member 3. The fuel gas or the oxidizing gas flows in a space surrounded by the supply channel 4 formed in the channel forming member 3 and the electrode layer 2, and by coming into contact with the electrode layer 2, an electrochemical reaction occurs to generate power. On the other hand, the flow path forming member 3 is formed of a conductive member, is closely connected to the electrode layer 2 by the ribs 7 and is electrically connected thereto, and also has a function of a current collecting member for collecting electric power generated by the fuel cell. are doing.

The photocatalyst layer 5 is formed on the surface of the supply channel 4 formed in the channel forming member 3 so as not to impair the conductivity. The photocatalyst layer 5 is a material that exhibits hydrophilicity when irradiated with ultraviolet rays, and titanium oxide, tungsten oxide, or a combination thereof can be used. The photocatalyst layer 5 can be formed by a simple method such as a spray method or a coating method, and can be manufactured with high productivity in actual production.

In assembling the fuel cell, it is desirable to irradiate the photocatalyst layer 5 with sufficient ultraviolet rays so as to maintain hydrophilicity for a long operation time of the fuel cell. In the polymer electrolyte fuel cell configured as described above,
Since the photocatalyst layer 5 has a hydrophilic property, the condensed water droplets and the generated water droplets do not spread in a thin film shape on the surface of the photocatalyst layer 5 to generate large water droplets. Therefore, the flow path is not blocked by water droplets, and the operation of the polymer electrolyte fuel cell is not hindered.

An optical fiber 6 is inserted into the supply channel 4. Since the optical fiber 6 is a light conducting member made of a glass-based material or a plastic-based material, it is possible to irradiate a photocatalyst layer formed on the surface of the supply channel 4 with ultraviolet light from a light source outside the fuel cell. . When the hydrophilicity of the photocatalyst layer 5 is reduced, the hydrophilicity can be restored by irradiating ultraviolet rays with the optical fiber 6. Although not shown, the photocatalyst layer 5 can be formed only on a portion where water droplets are likely to be generated, such as a lower portion of the fuel cell, a downstream portion of the fuel gas or the oxidizing gas, or a portion where blocking by water droplets is likely to occur. .

FIG. 2 is a sectional view showing an outline of a polymer electrolyte fuel cell showing another embodiment of the present invention. Electrolyte layer 1
Are arranged so as to face each other.
Further, the flow path forming member 3 is arranged so as to sandwich the laminate 10 of the electrolyte layer 1 and the electrode layer 2 so as to face each other. The flow path forming member 3 has a fuel gas or oxidizing gas supply flow path 4.
Are formed, and a photocatalyst layer is formed on the surface of the supply flow path 4 as described above. An optical fiber 6 is inserted into the supply channel 4. Since the optical fiber 6 is a light conducting member made of a glass-based material or a plastic-based material, ultraviolet light from an external light source 9 can be applied to a photocatalyst layer formed on the surface of the supply channel 4. . The through hole 8 into which the optical fiber 6 is inserted needs to have a gas-tight structure so that the fuel gas or the oxidizing gas does not leak or the foreign gas does not enter from the outside.

In the polymer electrolyte fuel cell configured as described above, when the hydrophilicity of the photocatalyst layer 5 is reduced, the hydrophilicity can be restored by irradiating ultraviolet rays using the optical fiber 6. In recent years, with the progress of material development, photocatalysts having an ultraviolet intensity required for exhibiting hydrophilicity of several μW per square cm have been recently proposed. If this is used, it is possible to maintain hydrophilicity for a considerably long period even with the amount of ultraviolet light irradiated at the time of assembling the fuel cell.
Even if the hydrophilicity is reduced, the optical fiber 6
The hydrophilicity can be easily restored by the ultraviolet rays radiated. As described above, when the photocatalyst layer is formed limited to a specific portion, the optical fiber 6 may be provided only for that portion. Further, since there is no need to constantly irradiate ultraviolet rays during the operation of the fuel cell, the optical fiber 6 can be configured to be detachable. That is,
The optical fiber 6 is not provided permanently, and only the through hole 8 is provided.
It is also possible to connect the optical fiber 6 periodically and irradiate ultraviolet rays. According to this method,
Since it is not necessary to always install the optical fiber 6 in each fuel cell, the cost can be reduced.

As a method of irradiating the photocatalyst layer with ultraviolet rays,
A luminous agent can also be used. The luminous agent is a material that absorbs and stores ultraviolet rays such as sunlight and fluorescent light, and then emits light by itself. When the hydrophilicity of the photocatalyst layer is reduced, such a phosphorescent agent powder is irradiated with sufficient ultraviolet rays to absorb the ultraviolet rays inside the phosphorescent agent, mixed with a fuel gas or an oxidizing gas and circulated, and then distributed to the photocatalytic layer. It becomes possible to restore the hydrophilicity of the photocatalyst layer by the emitted ultraviolet light when passing through the region where is formed. As described above, by using a photocatalyst having an ultraviolet intensity of several μW per square cm required for exhibiting hydrophilicity, hydrophilicity can be easily recovered by ultraviolet rays from the phosphorescent powder. Further, since there is no need to constantly irradiate ultraviolet rays during the operation of the fuel cell, it is not necessary to mix the luminous agent with the fuel gas or the oxidizing gas at all times. It may be distributed depending on the operating conditions of the fuel cell, the performance of the photocatalyst layer used, and the like.

[0015]

As described above, according to the present invention,
Due to the hydrophilicity of the photocatalyst layer coated on the surface of the flow channel forming member that forms the fuel flow channel, generated water and moisture attached to the flow channel forming surface do not become water droplets, and blockage of the flow channel by water droplets. Will not occur. Generated water and attached water
Although a thin water layer is formed on the surface of the photocatalyst layer, since the contact angle of the photocatalyst layer is very small, the resistance to the flow is minimized, and the flow is smoothly discharged by the flow of the fuel gas or the oxidizing gas. Therefore, the diffusion of the fuel to the electrode is not hindered by the water generated in the fuel flow path, and the operation efficiency of the fuel cell can be maintained high.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a configuration of a fuel cell according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a fuel cell according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 electrolyte layer 2 electrode layer 3 flow path forming member 4 supply flow path 5 photocatalyst layer 6 optical fiber 7 rib 8 through hole 9 light source 10 laminated body

Claims (5)

[Claims] 1. An electrolyte layer, a plurality of electrode layers sandwiching the electrolyte layer, and a flow of a fuel gas or an oxidizing gas between the electrode layer sandwiching a laminate comprising the electrolyte layer and the electrode layer. A fuel cell, comprising: a flow path forming member that forms a passage; and a photocatalyst layer having hydrophilicity is provided on a surface of the flow path forming member that forms the flow path. 2. The fuel cell according to claim 1, further comprising means for irradiating the photocatalyst layer with ultraviolet light. 3. The fuel cell according to claim 2, wherein the means for irradiating the ultraviolet rays is an optical fiber. 4. The fuel cell according to claim 2, wherein the means for irradiating the ultraviolet rays is a luminous agent provided on a surface forming a flow path. 5. The fuel cell according to claim 3, wherein said optical fiber is detachable.