JP2002352828A - Solid-state polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell capable of shortening the start-up time. SOLUTION: The solid-state polymer electrolyte fuel cell comprises a hydrogen pole and an oxygen pole supporting a catalyst with a polymer electrolyte film (1) in between, with the poles supplied with hydrogen and oxygen to generate a power. A pixel layer is formed where the absorbancy changes according to humidification at the polymer electrolyte film. By measuring the change in the absorbance of the pixel layer, the humidification of the polymer electrolyte film (1) is judged, and the polymer electrolyte film (1) is supplied with water content according to the absorbancy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a solid polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art In order to cope with the recent problems of air pollution caused by exhaust gas from automobiles and global warming caused by carbon dioxide, fuel cells that enable clean exhaust gas and highly efficient energy conversion have attracted attention. Among them, solid polymer electrolyte fuel cells have attracted attention as power sources for mobile bodies such as automobiles because of their high output density.

In a solid polymer electrolyte fuel cell (hereinafter referred to as a fuel cell), a noble metal catalyst such as platinum is supported on a surface of a perfluorosulfonic acid membrane having a high hydrogen ion conductivity on a polymer membrane. Gas diffusion electrodes (referred to as hydrogen electrode and oxygen electrode, respectively) for transmitting hydrogen gas and air are installed on both surfaces of the polymer film, and a bipolar plate having a gas flow path formed outside the gas diffusion electrode is formed between the polymer film and the gas diffusion electrode. It is configured to sandwich the electrode.

Hydrogen gas molecules are separated into hydrogen ions and electrons by the action of the hydrogen electrode catalyst. The electrons pass through an external load circuit and are then sent to the oxygen electrode side catalyst, where the hydrogen gas passes through the polymer membrane by the oxygen electrode catalyst. It reacts with the ions and supplied air to become water and is discharged to the outside. Here, the higher the conductivity of the hydrogen ions in the polymer membrane (or the lower the electrical resistance indicated by the reciprocal thereof), the higher the power generation efficiency can be obtained.

However, the conductivity depends on the water content of the polymer film, and it is known to control the humidification state of the gas supplied to the gas diffusion electrode according to the wetting state of the polymer film.
No. 2832.

[0006]

However, the technique disclosed in Japanese Patent Application Laid-Open No. 7-282832 uses hydrogen gas and air to a fuel cell, and uses a impedance measurement and a reference electrode after a voltage is generated. Since the voltage measurement is performed to detect the humidified state of the polymer membrane, the humidified state of the polymer membrane cannot be detected unless gas is supplied, and the time required for the measurement when applied to a fuel cell vehicle is reduced. It becomes a problem. In particular, when the power generation of the fuel cell is not performed for a long time, the polymer membrane generally tends to dry, and sufficient power generation cannot be performed immediately after startup.
If the gas is not supplied, the wet state of the polymer film cannot be detected, so that appropriate control of the humidification of the polymer film in accordance with the gas supply cannot be performed, and it takes a long time to reach a predetermined power generation amount.

It is an object of the present invention to provide a fuel cell which solves the above problems.

[0008]

According to a first aspect of the present invention, a hydrogen electrode and an oxygen electrode carrying a catalyst are provided with a polymer electrolyte membrane interposed therebetween, and hydrogen and oxygen are supplied to the respective electrodes to generate power. Is performed in a solid polymer electrolyte fuel cell,
A dye layer whose absorbance changes according to the humidified state of the polymer electrolyte membrane, means for measuring the absorbance of the dye layer, and means for supplying water to the polymer electrolyte membrane according to the measured absorbance.

According to a second aspect of the present invention, in the first aspect, a light emitting section for irradiating light transmitted through the dye layer and a light receiving section for receiving light transmitted through the dye layer are provided. And the absorbance of the dye layer is detected based on the reference absorbance when the light enters and the absorbance transmitted through the dye layer.

In a third aspect based on the second aspect, a bipolar plate sandwiching the polymer electrolyte membrane, the hydrogen electrode and the oxygen electrode is provided, and a pair of optical fibers are placed in the bipolar plate so as to sandwich the dye layer. And each optical fiber is connected to the light emitting unit and the light receiving unit.

In a fourth aspect based on the first or second aspect, a bipolar plate is provided so as to sandwich the polymer electrolyte membrane, a hydrogen electrode and an oxygen electrode, and the polymer electrolyte membrane is formed larger than the bipolar plate. A dye layer is formed on the polymer electrolyte membrane protruding from the bipolar plate.

According to a fifth aspect, in any one of the first to fourth aspects, the conductivity of the polymer electrolyte membrane is calculated from the absorbance of the dye layer, and the calculated conductivity is less than a predetermined value. Supplies more water for humidifying the polymer electrolyte membrane into the fuel cell than the amount of water supplied when the calculated conductivity is a predetermined value.

According to a sixth aspect, in any one of the first to fourth aspects, the conductivity of the polymer electrolyte membrane is calculated from the absorbance of the dye layer.
A large amount of water for humidifying the polymer electrolyte membrane is supplied into the fuel cell.

[0014]

According to the first aspect of the present invention, a dye layer whose absorbance changes in accordance with the humidified state of the polymer electrolyte membrane is formed, and the absorbance of the dye layer is measured. By supplying more water to the electrolyte membrane than at the predetermined absorbance, the fuel cell can be quickly started, and the transition to the steady operation of high-efficiency power generation in a short time becomes possible. In addition, the configuration is simpler than the conventional measurement method,
The time required for measurement can be reduced.

According to a second aspect of the present invention, there is provided a light emitting portion for irradiating light transmitted through the dye layer, and a light receiving portion for receiving light transmitted through the dye layer, and a reference when light enters the light receiving portion directly from the light emitting portion. By detecting the absorbance of the dye layer based on the absorbance and the absorbance transmitted through the dye layer, the humidified state of the polymer electrolyte membrane can be detected without supplying the fuel gas to the fuel cell. The necessity of controlling the supply of water to the membrane can be determined in a short time, and the startup time can be reduced.

In the third invention, a bipolar plate sandwiching the polymer electrolyte membrane, the hydrogen electrode and the oxygen electrode is provided, and a pair of optical fibers are fixed in the bipolar plate so as to sandwich the dye layer. By connecting the fiber to the light emitting unit and the light receiving unit, the humidified state of the polymer electrolyte membrane can be detected with a simple configuration.

In the fourth invention, a bipolar plate sandwiching the polymer electrolyte membrane, the hydrogen electrode and the oxygen electrode is provided, and the polymer electrolyte membrane is formed larger than the bipolar plate.
By forming the dye layer on the polymer electrolyte membrane that protrudes from the bipolar plate, the structure can be further simplified, and it can be easily manufactured.

In the fifth and sixth aspects, the conductivity or the water content of the polymer electrolyte membrane is calculated from the absorbance of the dye layer, and if the calculated conductivity or the water content is less than a predetermined value, the polymer electrolyte By supplying more water for humidifying the membrane into the fuel cell than the calculated conductivity or the amount of water when the amount of water is a predetermined value, the water is always high regardless of the start-up operation or the steady operation. The humidified state of the molecular electrolyte membrane can be maintained in an appropriate state.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a solid polymer electrolyte fuel cell according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating the configuration of the fuel cell according to the first embodiment. In the present embodiment, a fuel-side bipolar plate 6 in which a hydrogen gas flow path 5 is formed, an air flow path 7 is formed on one surface, and an air flow path 7 is formed on the other surface so as to sandwich the first solid polymer electrolyte membrane 1 from both sides. An air-side bipolar plate 9 having a cooling water flow path 8 is arranged. A gas diffusion electrode 3a coated with a catalyst layer is disposed between the first solid polymer electrolyte membrane 1 and the fuel-side bipolar plate 6 so as to face the hydrogen gas flow path 5 formed in the fuel-side bipolar plate 6. Similarly, a gas diffusion electrode 3b coated with a catalyst layer between the first solid polymer electrolyte membrane 1 and the air-side bipolar plate 9 so as to face the air channel 7 formed in the air-side bipolar plate 9 Is arranged.

The first solid polymer electrolyte membrane 1 is formed between the bipolar plates 6, 9 in which the hydrogen gas flow path 5 and the air flow path 7 are not formed and the first solid polymer electrolyte membrane 1 by a technique such as adsorption, casting, or spin coating. The second solid polymer electrolyte membrane 2 having the dye layer is sandwiched between the gas diffusion electrodes 3a and 3d.
An O-ring 4 is provided between b and the second solid polymer electrolyte membrane 2 to prevent air or hydrogen from leaking to the outside. A single cell is formed with such a laminated structure. From this state, the second solid polymer electrolyte membrane 2 is fixed by fastening by stacking.

The second solid polymer electrolyte membrane 2 is a membrane having the same chemical composition as the solid polymer electrolyte membrane.
It does not need to be a solid polymer electrolyte membrane.

Further, the bipolar plates 6 and 9 have the second
A hole 10 opened to face the solid polymer electrolyte membrane 2,
Optical fibers 11 and 14 are inserted into the holes 10 and 13, respectively, and the ends thereof face the second solid polymer electrolyte membrane 2. Optical fiber 11, 1
The other end of 4 is connected to light emitting unit 12 or light receiving unit 15.

The dye layer formed on the second solid polymer electrolyte membrane 2 may be a dye layer that changes its color due to moisture. For example, an inorganic compound such as cobalt chloride or a cyanine-based organic compound may be used. Is possible.

In the present embodiment, the structure in which the dye layer is formed on the second solid polymer electrolyte membrane 2 by a method such as adsorption, casting, spin coating, etc., is disclosed.
It can be directly formed on the solid polymer electrolyte membrane 1 by a technique such as adsorption, casting, or spin coating.

The light emitting section 12 and the light receiving section 15 are configured using light emitting elements such as light emitting diodes and laser diodes and light receiving elements such as photodiodes and phototransistors. By using a wavelength region of these optical elements near the maximum absorbance of the dye to be used, the membrane resistance or the humidified state of the solid polymer electrolyte membrane can be detected with high sensitivity. In the measurement of the absorbance, light that does not pass through the dye layer is detected as reference light, and the reference light and the detected light are compared to measure the absorbance, thereby eliminating errors due to deterioration of the measuring instrument over time, More accurate measurement can be performed.

In this embodiment, the humidified state of the first solid polymer electrolyte membrane 1 is detected from the humidified state of the second solid polymer electrolyte membrane 2 having the dye layer formed thereon. Even if a dye layer is formed in a portion of the polymer electrolyte membrane 1 that is not in contact with the gas diffusion electrodes 3a and 3b, and the humidified state is directly detected from this portion, the first solid height in contact with the gas diffusion electrodes 3a and 3b can be detected. If the correlation between the humidified state of the molecular electrolyte membrane 1 and the humidified state of the first solid polymer electrolyte membrane 1 that is not in contact is measured in advance, the gas diffusion electrodes 3a, 3b
The humidified state of the first solid polymer electrolyte membrane 1 that has come into contact with can be accurately detected.

FIG. 2 is a schematic diagram of a fuel cell system using the fuel cell of the present invention. Detector 21 for detecting the humidified state of first solid polymer electrolyte membrane 1 provided in fuel cell 20
The signal transmitted from the light emitting unit 12 and the light receiving unit 15 is input to the controller 22, and the controller 22 determines the amount of water supplied to the fuel cell 2 based on the detected humidification state. Is controlled using.

FIG. 3 is a flowchart for explaining the contents of control at the time of startup performed by the controller 22.

First, in step S1, the absorbance of the first solid polymer electrolyte membrane 1 is detected based on the output signal from the detection unit 21 and the reference light stored in advance. In the following step S2, the water content of the first solid polymer electrolyte membrane 1 is calculated from the absorbance,
Detects the humidification state. To determine the water content from the absorbance,
For example, a map as shown in FIG.
2, and the water content is calculated from the absorbance based on this map.

In step S3, the conductivity of the first solid polymer electrolyte membrane 1 is calculated from the amount of water. At this time, a map for calculating the conductivity from the amount of water as shown in FIG. The conductivity is calculated from the water content based on this map.

In step S4, the necessity of controlling the humidification of the first solid polymer electrolyte membrane 1 is determined based on the calculated conductivity. That is, it is determined whether or not the water amount is controlled by the water injector 24 to change. For example, when the conductivity is not less than 7 × 10- ² S / cm change in supplied amount of water is determined to be unnecessary, the flow ends. When it is necessary to control the water supply amount, for example, when the water supply amount is less than the reference value, step S5
To calculate the amount of water to be supplied. The water calculated in step S6 is supplied from the water injector 24 to the fuel cell 2
0 hydrogen gas or air to the inlet manifold,
The amount of humidification of the first solid polymer electrolyte membrane 1 is increased. The supply of water may be performed by providing holes for supplying water to the bipolar plates 6 and 9, and further, the water or the manifold may be heated in accordance with the supply of water.

By such control, the start-up time can be reduced, and the rated output can be obtained from the fuel cell.

It is needless to say that the control contents described above can be applied not only at the time of starting but also at the time of steady operation.
Further, even when an error occurs in one of the measured values due to a change in the voltage of the cell voltmeter 23 and a change in the absorbance detected by the detection unit 21, the water supply control can be performed more accurately. Further, it is possible to appropriately control the water supply amount by the hydrogen gas supply amount.

Therefore, the humidified state of the first solid polymer electrolyte membrane 1 can be detected by measuring the absorbance using the dye layer whose absorbance changes depending on the humidified state, and the fuel cell can be quickly started. Power generation and high-efficiency power generation. Before supplying hydrogen gas,
Since the humidified state of the polymer electrolyte membrane 1 can be grasped, the amount of power generated by the fuel cell can be estimated in advance. Furthermore, by detecting the cell voltage of the fuel cell, the operating state of the fuel cell and the humidified state of the polymer electrolyte membrane can be detected, and the flow of water and hydrogen gas can be controlled to quickly provide the required power generation. It is possible to do. Further, the configuration is simpler than that of the conventional measuring method, and the time required for the measurement can be reduced.

FIG. 6 shows the configuration of a fuel cell according to the second embodiment. The configuration is the same as that of the first embodiment, but the number of the second solid polymer electrolyte membranes 2 and the second solid polymer Electrolytic membrane 2
Are different in the position where the humidification state is detected. The second solid polymer electrolyte membrane 2 is provided only on one surface of the first solid polymer electrolyte membrane 1, and the first and second solid polymer electrolyte membranes 1, 2 extend beyond the bipolar plates 6, 9. Thus, the humidified state of the first solid polymer electrolyte membrane 1 is detected at the protruding portion. With this configuration, it is possible to detect the humidified state of the solid polymer electrolyte membrane with a simpler configuration.

The present invention is not limited to the above-described embodiment, and it is apparent that various changes can be made within the scope of the technical idea described in the claims.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a solid polymer electrolyte fuel cell illustrating a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a solid polymer electrolyte fuel cell system.

FIG. 3 is a flowchart for explaining control contents performed by the controller.

FIG. 4 is a map for calculating the water content from the absorbance of the polymer electrolyte membrane.

FIG. 5 is a map for calculating the electric conductivity from the water content of the polymer electrolyte membrane.

FIG. 6 is a schematic view of a solid polymer electrolyte fuel cell illustrating a second embodiment.

[Description of Signs] 1 First solid polymer electrolyte membrane 2 Second solid polymer electrolyte membrane 3a, 3b Gas diffusion electrode 4 Ring 5 Hydrogen gas flow path 6 Bipolar plate 7 Air flow path 8 Cooling water flow path 9 Bipolar plate 11 Light Fiber 12 Light emitting part 14 Optical fiber 15 Light receiving part

Claims (6)

[Claims] 1. A solid polymer electrolyte fuel cell in which a hydrogen electrode and an oxygen electrode carrying a catalyst are provided with a polymer electrolyte membrane interposed therebetween, and power is generated by supplying hydrogen and oxygen to the respective electrodes. In, a dye layer whose absorbance changes according to the humidified state of the polymer electrolyte membrane, means for measuring the absorbance of the dye layer, and means for supplying water to the polymer electrolyte membrane according to the measured absorbance A solid polymer electrolyte fuel cell, comprising: 2. A light-emitting portion for irradiating light transmitted through the dye layer, and a light-receiving portion for receiving light transmitted through the dye layer, a reference absorbance when light directly enters the light-receiving portion from the light-emitting portion;
2. The solid polymer electrolyte fuel cell according to claim 1, wherein the absorbance of the dye layer is detected based on the absorbance transmitted through the dye layer. 3. A bipolar plate sandwiching the polymer electrolyte membrane, the hydrogen electrode and the oxygen electrode is provided, and a pair of optical fibers is fixed in the bipolar plate so as to sandwich the dye layer. 3. The solid polymer electrolyte fuel cell according to claim 2, wherein the fuel cell is connected to a light emitting part and a light receiving part. 4. A bipolar plate sandwiching said polymer electrolyte membrane, a hydrogen electrode and an oxygen electrode, wherein said polymer electrolyte membrane is formed larger than said bipolar plate, and a dye layer is formed on said polymer electrolyte membrane protruding from said bipolar plate. The solid polymer electrolyte fuel cell according to claim 1, wherein: 5. The method according to claim 1, wherein the conductivity of the polymer electrolyte membrane is calculated from the absorbance of the dye layer, and when the calculated conductivity is less than a predetermined value, water for humidifying the polymer electrolyte membrane is supplied to the fuel cell. 5. The solid polymer electrolyte fuel cell according to claim 1, wherein the amount of supplied water is larger than the amount of water supplied when the calculated conductivity is a predetermined value. 6. 6. The method according to claim 6, wherein the conductivity of the polymer electrolyte membrane is calculated from the absorbance of the dye layer, and the smaller the calculated conductivity, the more water for humidifying the polymer electrolyte membrane is supplied into the fuel cell. The solid polymer electrolyte fuel cell according to any one of claims 1 to 4, wherein: