JPH06267562A - Solid high polymer electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To enable cell reaction to be kept up stably by facilitating gas discharge while gas is being dispersed by means of steam of generated water and moving water even in the downstream of each oxidant flow path, and also facilitating discharge of generated water and moving water which are liquefied and/or formed into a state of droplets. CONSTITUTION:The fuel cell is equipped with a laminated body 31 where an anode and a cathode are disposed on both the surfaces of an electrolyte layer 32 respectively, a fuel distributing plate 37 which is provided for the anode side of the aforesaid layer 31 while being furnished with each fuel flow path 36 feeding fuel to the aforesaid anode, and with oxidant distributing plate 40 which is provided for the cathode side of the aforesaid laminated body 31 while being furnished with each oxidant flow path 39 feeding oxidant to the aforesaid cathode. And the percentage of voids of the cathode to which oxidant is fed is made gradually large along the flow path of oxidant from the upstream side to the downstream side, so that the percentage of voids is thereby changed along an oxidant flow path 39.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell having an improved cathode electrode on the side to which an oxidant is supplied.

[0002]

2. Description of the Related Art In a solid polymer electrolyte fuel cell, as shown in FIG. 1, a polymer ion exchange membrane (for example, a fluororesin ion exchange membrane having a sulfonic acid group) is used as an electrolyte 1 and catalyst electrode layers are provided on both sides. It has an electrode assembly 6 structure including (for example, platinum) 2 and 3 and porous carbon electrodes 4 and 5. Hydrogen in the humidified fuel supplied to the anode electrode side is hydrogen-ionized on the catalyst electrode (anode electrode) 2, and the hydrogen ions pass through the electrolyte 1 in the presence of water to form H ^+. As xH ₂ O, it moves to the cathode side together with water.

The transferred hydrogen ions are transferred to the catalyst electrode (cassette).
Oxygen in the oxidizer and the external circuit 7
Reacts with the incoming electrons to produce water, and the produced water is caustic.
It is discharged from the cathode 3 to the outside of the fuel cell. this
At this time, the electric current flowing through the external circuit 7 is converted into a direct current energy
Available as a ghee. It should be noted that the polymer 1 that serves as the electrolyte 1
In the on-exchange membrane, hydrogen ion permeability as described above
In order to achieve this, keep this membrane in a state of sufficient water retention.
It must be kept in the fuel or oxidizer
Including saturated steam equivalent to the operating temperature of
Humidifying and supplying the fuel and the oxidant to the electrode assembly 6,
I try to keep water retention. Below, the high solid content
The reaction formula in the child electrolyte fuel cell is shown. Anode side: H₂→ 2H⁺ + 2e^-  Cathode side: (1/2) O₂+ 2H⁺ + 2e^- → H₂O Total reaction: H₂+ (1/2) O₂→ H₂O FIG. 2 shows an example of the configuration of a conventional solid polymer electrolyte fuel cell.
Indicates.

Reference numeral 11 in the figure is a laminate in which a first catalyst electrode (anode electrode) 13 and a second catalyst electrode (cathode electrode) 14 are laminated on and under an electrolyte 12. On the upper side of this stack 11, the first
A fuel distribution plate 17 having a carbon electrode (anode electrode) 15 and a fuel flow path 16 is provided. A second carbon electrode (anode electrode) 18 and an oxidant channel are provided below the laminated body 11.
An oxidant distribution plate 20 having 19 is provided.

In such a fuel cell, the fuel passage
The fuel hydrogen flowing through 16 passes through the first carbon electrode 15 and is hydrogen-ionized on the first catalyst electrode 13, and the hydrogen ions are H ^{+ in the} electrolyte 12 with the interposition of water. ・ As xH ₂ O,
It moves to the cathode side together with water. The water generated on the second catalyst electrode 14 by this hydrogen ion and the water that has moved in the electrolyte 12 from the anode side together with the hydrogen ion are
Passing through the second carbon electrode 18 having a uniform porosity structure along the oxidant flow path 19 as vapor or a part of liquid,
The oxidant is discharged to the oxidant channel 19.

[0006]

However, in a porous carbon electrode having a uniform porosity along the oxidant flow path as shown in FIG. 2, the generated water and hydrogen ions generated by the battery reaction are generated. Along with the moving water that moves from the anode electrode to the cathode electrode together with the downstream of the oxidant flow path 17,
Since the partial pressure of water vapor in the oxidant atmosphere increases, it becomes difficult for the gas to diffuse and be discharged as vapor. In addition, the partially liquefied or liquefied generated water or mobile water is clogged in the porous carbon electrode on the cathode electrode side, which makes it easy to prevent gas diffusion of the oxidant in the porous carbon electrode. Was there. Therefore, there has been a situation in which a stable battery reaction is difficult to be performed.

The present invention has been made in consideration of such circumstances, and the porous carbon electrode on the side to which the oxidant is supplied has a porosity of from the upstream flow channel region of the oxidant to the downstream flow channel region. By gradually increasing it, the porosity is changed along the oxidant flow path, so that gas diffusion and discharge due to the vapor of generated water or moving water can be easily performed in the downstream area of the oxidant flow path, and liquefaction or liquid It is an object of the present invention to provide a solid polymer electrolyte fuel cell in which droplets of produced water and mobile water can be easily discharged and a stable cell reaction can be continuously performed.

[0008]

According to the present invention, there is provided a laminated body in which an anode electrode and a cathode electrode are arranged on both surface sides of an electrolyte, and an anode electrode side of the laminated body, and fuel is supplied to the anode electrode. A fuel distribution plate having a fuel flow path,
An oxidant distribution plate having an oxidant flow channel for supplying an oxidant to the cathode electrode of the laminate, and oxidizing the cathode electrode on the oxidant supply side. The solid polymer electrolyte fuel cell is characterized in that the porosity is gradually increased from the upstream flow channel region of the agent to the downstream flow channel region, and the porosity is changed along the oxidant flow channel.

[0009]

[Function] In the porous carbon electrode structure on the side to which the oxidant is supplied, the porosity is gradually increased by gradually increasing the porosity from the upstream flow channel region to the downstream flow channel region of the oxidant flow channel. By changing along the flow path, even if the partial pressure of water vapor in the oxidant atmosphere rises in the downstream flow path area of the oxidant flow path, the generated water or moving water easily becomes vapor and is diffused and discharged by gas, Alternatively, liquefied or liquefied generated water or moving water easily passes through the carbon electrode and is discharged into the oxidant flow channel.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.

Reference numeral 31 in the drawing denotes a first catalyst electrode (anode electrode) 33 above and below an electrolyte 32 made of a polymer ion exchange membrane (for example, a fluororesin ion exchange membrane having a sulfonic acid group).
It is a laminated body in which the second catalyst electrodes (cathode electrodes) 34 are laminated respectively. A fuel distribution plate 37 having a first carbon electrode (anode electrode) 35 and a fuel flow path 36 is provided above the stack 31.
Is provided. An oxidant distribution plate 40 having a second carbon electrode (anode electrode) 38 and an oxidant flow channel 39 is provided below the laminated body 31. In such a fuel cell, the porous second carbon electrode 38 on the side to which the oxidant is supplied has a porosity that gradually increases from the upstream flow channel region of the oxidant flow channel to the downstream flow channel region (arrow direction). The porosity is changed along the oxidant flow channel 39.

In the solid polymer electrolyte fuel cell having such a structure, the fuel hydrogen flowing through the fuel flow path 36 passes through the first carbon electrode 36 and is hydrogen-ionized on the first catalyst electrode 33, and the hydrogen ion is converted into the electrolyte 32. H ⁺ under the presence of water ・
As xH ₂ O, it moves to the cathode side together with water. The water generated on the second catalyst electrode 34 by the hydrogen ions and the water that has moved in the electrolyte 32 from the anode side together with the hydrogen ions are vapor or even if the water vapor partial pressure in the oxidant atmosphere is high. A part of the liquid remains as it is, passes through the second carbon electrode 38, and is discharged to the oxidant channel 39 through which the oxidant flows. According to the above-mentioned embodiment, the porous second carbon electrode 38 on the side to which the oxidant is supplied has the porosity gradually increased from the upstream flow channel region of the oxidant flow channel 39 to the downstream flow channel region. The porosity is changed along the oxidant channel 39. Therefore, due to the generated water or the moving water discharged in the upstream flow channel area of the oxidant flow channel 39, the oxidant flow channel 39
Although the partial pressure of water vapor in the oxidant atmosphere rises in the downstream flow passage region of, the porosity of the porous second carbon electrode 38 is large, so that it is also generated in the downstream region of the oxidant flow passage 39. It is easy for gas to be diffused and discharged by the vapor of water and moving water, and the liquefied and dropletized generated water and moving water are also
It easily passes through the carbon electrode 38 and is discharged into the oxidant channel 39. This makes it possible to continuously perform a stable battery reaction.

[0013]

As described above in detail, according to the present invention, the porosity of the porous carbon electrode on the side to which the oxidant is supplied is gradually increased from the upstream flow channel region of the oxidant to the downstream flow channel region. By increasing the porosity, the porosity can be changed along the oxidant flow channel, so that gas diffusion and discharge due to vapor of generated water or moving water can be easily performed in the downstream region of the oxidant flow channel, and liquefaction or droplets It is possible to provide a solid polymer electrolyte fuel cell in which the produced water and the mobile water that have been turned into are easily discharged, and a stable cell reaction can be continued.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the function of a solid polymer electrolyte fuel cell.

FIG. 2 is an explanatory view of a conventional solid polymer electrolyte fuel cell.

FIG. 3 is an explanatory diagram of a solid polymer electrolyte fuel cell according to an embodiment of the present invention.

[Explanation of symbols]

31 ... Laminated body, 32 ... Electrolyte, 33 ...
First catalyst electrode, 34 ... Second catalyst electrode, 35 ... First carbon electrode, 36 ... Fuel flow path, 37 ... Fuel distribution plate, 38 ...
Second carbon electrode, 39 ... Oxidizing agent flow path, 40 ... Oxidizing agent distribution plate.

Claims (1)

[Claims] 1. A fuel distribution system having a laminated body in which an anode electrode and a cathode electrode are arranged on both sides of an electrolyte, and a fuel flow path provided on the anode electrode side of the laminated body and for supplying fuel to the anode electrode. A plate and an oxidant distribution plate provided on the cathode side of the laminated body and having an oxidant flow channel for supplying an oxidant to the cathode electrode. The solid polymer electrolyte fuel cell is characterized in that the porosity is gradually increased along the oxidant from the upstream flow path area to the downstream flow path area, and the porosity is changed along the oxidant flow path.