JP3364028B2 - Solid polymer electrolyte membrane fuel cell body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte membrane fuel cell capable of efficiently supplying water to a solid polymer electrolyte membrane. 2. Description of the Related Art A fuel cell does not need to use fossil fuel which has a problem of resource depletion, and generates almost no noise.
Since it has excellent features such as an extremely high energy recovery efficiency as compared with other energy engines, it is used as a relatively small power plant, for example, in a building unit or a factory unit. In recent years, it has been considered that this fuel cell is used as a power source for a motor that operates instead of a vehicle-mounted internal combustion engine, and a vehicle or the like is driven by this motor. In this case, it is important to recycle as much as possible the substances generated by the reaction. It is desirable that the fuel cell be as small as possible. In view of this, a solid polymer electrolyte membrane fuel cell has been receiving attention. Here, as an example, the basic structure of a solid polymer electrolyte membrane fuel cell body will be described with reference to FIG.
As shown in the figure, a battery main body 01 is configured by joining gas diffusion electrodes 03A and 03B to both sides of a solid polymer electrolyte membrane 02. The joined body is provided on both sides of the solid polymer electrolyte membrane 02 with gas diffusion electrodes 03A and 03A.
It is manufactured by hot pressing or the like after combining B. The gas diffusion electrodes 03A and 03B are formed by bonding reaction films 04A and 04B and gas diffusion films 05A and 05B, respectively.
The surface of 4B is in contact. Therefore, the battery reaction mainly occurs at the contact surface between the electrolyte membrane 02 and the reaction membranes 04A and 04B. For example, the gas diffusion electrode 03A is an oxygen electrode and the gas diffusion electrode 03B is a hydrogen electrode,
A and 05B react oxygen and hydrogen with the reaction films 04A and 04B.
To the reaction membranes 04A, 04B and the electrolyte membrane 0A.
At the interface with 2, a reaction as shown in the following “Chemical Formula 1” occurs. Embedded image Interface of the reaction film 04A: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O Interface of the reaction film 04B: 2H ₂ → 4H ⁺ + 4e ^- where 4H ⁺ passes from the hydrogen electrode to the oxygen electrode through the electrolyte film 02. It flows into, 4e ^- is will flow from the hydrogen electrode to the oxygen electrode through the load 06, electrical energy is obtained. [0006] In such a solid polymer electrolyte membrane fuel cell, the solid polymer electrolyte membrane 02 must be hydrated. For this reason, the moisture is supplemented by supplying the hydrogen source reformed gas in a humidified state. Water vapor is supplied to the solid polymer electrolyte membrane 02 by flowing cooling water so as to contact the gas diffusion electrode 03A or the gas diffusion electrodes 03A and 03B. [0007] However, there is a problem that as the performance and size are reduced, the water content of the solid polymer electrolyte membrane 02 becomes insufficient in a high-power region. Further, when water is supplied by flowing cooling water so as to come into contact with the gas diffusion electrodes 03A and 03B, there is a problem that the gas supply is insufficient, especially on the oxygen electrode side. In view of such circumstances, the present invention provides a solid polymer electrolyte membrane fuel cell body capable of efficiently supplying water to the solid polymer electrolyte membrane and achieving high performance and miniaturization. The purpose is to provide. [0010] The structure of a solid polymer electrolyte membrane fuel cell body according to the present invention that achieves the above objects is as follows.
A joined body formed by joining a solid polymer electrolyte membrane between two gas diffusion electrodes and the gas diffusion electrode on one side of the joined body;
Contact the surface of the electrode and supply hydrogen to the solid polymer electrolyte membrane.
Gas separator for the hydrogen side with a hydrogen supply passage
And the surface of the gas diffusion electrode on the other side of the joined body
To supply oxygen to the solid polymer electrolyte membrane
A gas separator for the oxygen side where the element supply passage is formed.
A solid polymer electrolyte membrane fuel cell body having a hydrogen
Gas separator for oxygen side and gas separator for oxygen side
The above gas separator for at least the hydrogen side of the generator
Has water impermeability and is above the gas separator.
The supply passage extends through the gas separator and the through hole.
It is characterized by being connected to a hot water passage through a water vapor permeable membrane . In the above construction, when hot water is supplied to the hot water passage, steam is introduced into at least the hydrogen supply passage via the water vapor permeable membrane at a saturated vapor pressure corresponding to the temperature of the hot water. Is supplied to the solid polymer electrolyte membrane through a gas diffusion electrode together with hydrogen or oxygen. Hereinafter, the present invention will be described with reference to an embodiment. FIG. 1 conceptually shows a solid polymer electrolyte membrane fuel cell body according to this embodiment. In FIG. 1, 1 is a solid polymer electrolyte membrane, 2A and 2B are gas diffusion electrodes, and the gas diffusion electrodes 2A and 2B are composed of reaction films 3A and 3B and gas diffusion films 4A and 4B, respectively. In the present embodiment, a plurality of joined bodies in which the solid polymer electrolyte membrane 1 and the gas diffusion electrodes 2A, 2B are joined, and the gas separators 5, 6
Are overlapped. Here, the gas diffusion electrode 2A is a hydrogen electrode and the gas diffusion electrode 2B is an oxygen electrode. The gas separator 5 in contact with the gas diffusion electrode 2A has a hydrogen supply groove 5a in contact with the gas diffusion film 4A. An oxygen supply groove 6 in contact with the gas diffusion film 4B is provided in the gas separator 6 in contact with the gas diffusion electrode 2B.
a are formed respectively. The gas separators 5 and 6 are provided with a hydrogen supply groove 5a or an oxygen supply groove 6a from the surface opposite to the contact surface with the gas diffusion electrodes 2A and 2B.
Through holes 5b and 6b are formed, and a water vapor permeable membrane 7 is provided so as to be in contact with the opposite surfaces, respectively.
Are formed. A gasket 9 is provided around the gas separators 5 and 6 between the contact surfaces with the gas diffusion electrodes 2A and 2B.
However, seal members (not shown) are provided around the surface opposite to the contact surface. In this embodiment, the gas diffusion electrodes 2A and 2B are made of platinum having an average particle diameter of 50 °, hydrophilic carbon black and hydrophobic carbon black having an average particle diameter of 450 °, and an average particle diameter of 0.3 μm.
Of polytetrafluoroethylene in the ratio of 0.7: 7: 3: 3, hydrophobic carbon black having an average particle size of 420 °, and polytetrafluoroethylene having an average particle size of 0.3 μm. And a hydrophobic gas diffusion film 4A, 4B having a ratio of 7: 3. Reaction films 3A, 3
B and the hydrophobic gas diffusion films 4A and 4B can be obtained by mixing a solvent such as solvent naphtha, alcohol, water, and hydrocarbon with each of the raw material powders other than platinum, and then performing compression molding. Then, these are stacked and rolled, and Pt 0.56 is formed on the reaction films 3A and 3B by a platinum chloride redox method.
mg / cm ² to support the gas diffusion electrodes 2A and 2A.
B is manufactured. On the other hand, as the solid polymer electrolyte membrane 1,
A 0.17 mm thick perfluorosulfonic acid polymer membrane (Nafion 117: manufactured by DuPont) was used. Then, the solid polymer electrolyte membrane 1 is sandwiched between the gas diffusion electrodes 2A and 2B and hot-pressed to form a joined body, which is further sandwiched by two gas separators 5 and 6 to form a fuel cell body. The gas diffusion films 4A and 4B may be provided as needed. Further, the water vapor permeable film 7 is
Those similar to A and 4B are used. Here, an example of the gas separator 5 will be described with reference to FIG. FIG. 2 shows the appearance of the joint surface of the gas separator 5 with the gas diffusion electrode 2A. As shown in the figure, the gas separator 5 is formed by forming a hydrogen supply groove 5a in a plate-shaped main body made of, for example, a metal, and each hydrogen supply groove 5a is communicated by two gas communication passages 5c. Note that the gas separator 6 is also the gas separator 5
It has the same structure as. When the gas separator is plastic, a metal film may be inserted into the gas diffusion film. In such a configuration, when hot water of, for example, 90 ° C. is supplied to the hot water passage 8, water vapor is generated through the gas diffusion film 7 at a water vapor partial pressure corresponding to the temperature.
a and the oxygen supply groove 6a. Therefore, when, for example, a hydrogen raw material reforming gas and oxygen are introduced into the hydrogen supply groove 5a and the oxygen supply groove 6a, water vapor is supplied to the polymer electrolyte membrane 1 through the gas diffusion electrodes 2A and 2B together with these raw material gases. Then, the solid polymer electrolyte membrane 1 is always in a water-containing state. In this case, it is preferable that the hydrogen source reformed gas and the air are supplied to the gas separators 5 and 6 at a pressure higher than the partial pressure of steam corresponding to the temperature of the hot water supplied to the hot water passage 8. In the above configuration, the gas separators 5, 6
Since cooling water is not supplied to the grooves contacting the gas diffusion electrodes 2A and 2B, it is necessary to provide a cooling means separately for each cell or, for example, every other cell. Furthermore, in the above configuration, not only is water vapor supplied to the solid polymer electrolyte membrane 1, but also because of the vapor pressure, the oxygen supply groove 6a of the gas separator 6 at the oxygen electrode.
In some cases, the generated water (water vapor) that has flowed into the hot water passage 8 passes through the water vapor permeable membrane 7, thereby also improving the battery performance. With the above configuration, the gas diffusion electrode 2
It is not necessary to make the gas diffusion films 4A and 4B of A and 2B hydrophobic, and a gas diffusion film having water permeability to some extent can be used. That is, for example, a gas diffusion electrode used in a phosphoric acid fuel cell can be used. In the above configuration, the gas separator is a plate-like member made of metal. However, the present invention is not limited to this, and a resin separator may be used. In this case, a metal net or a carbon cloth may be inserted into the gas diffusion film or at the boundary between the gas diffusion film and the separator to collect current. As the gas separator, any gas separator may be used as long as the gas is permeable. For example, a porous material having continuous pores or a corrugated material may be used as appropriate. In the above configuration, the cooling water is not directly in contact with the surfaces of the gas diffusion films 4A and 4B of the gas diffusion electrodes 2A and 2B. However, as shown in FIG. , 2B, the gas diffusion electrodes 2A, 2B
The water supply passage 10 together with the hydrogen supply passage 5a and the oxygen supply passage 5b contacting the surfaces of the gas diffusion films 4A and 4B of
And the hydrogen supply passage 5a and the oxygen supply passage 5b
Hydrogen and oxygen flowing inside the solid polymer electrolyte membrane 1 may be supplied to both sides of the solid polymer electrolyte membrane 1, and a hot water passage 8 may be provided so as to communicate with the water supply passage 10 when power is generated. (1) With such a configuration, the cooling performance is further improved as compared with the configuration shown in FIG. FIG. 4 shows an overall system of a solid polymer electrolyte membrane fuel cell using the fuel cell body described above. As shown in FIG. 1, the methanol reformed gas supplied to the hydrogen electrode 12 of the fuel cell body 11 is produced by a methanol reformer 13. The methanol reforming apparatus 13 includes a reforming section 14 and a preheating section 15, and the reforming section 14 is heated by combustion of a combustion gas composed of unreacted gas and air from the hydrogen electrode 12. The heating unit 14 is heated by the exhaust gas of the combustion gas heated. The preheating unit 15 is connected to a methanol tank 17 via a methanol supply pipe 16 for reforming.
A pump 20 driven by a motor 19 for pressure-feeding methanol 18 in a methanol tank 17, which is a raw material of the reformed gas, to the methanol reformer 13 is provided in the middle of the reforming methanol supply pipe 16. In the middle of the reforming methanol supply pipe 16, one end is connected to the other end of a water supply pipe 22 that communicates with the water tank 21. A pump 25 driven by a motor 24 for pumping water 23 in a water tank 21 to be supplied into the methanol supply pipe 16 for reforming is attached. Therefore, while passing through the preheating pipe 26 in the preheating section 15, the reforming raw material comprising the methanol 18 and the water 23 is mixed with the high-temperature combustion exhaust gas generated by burning the combustion gas. 200 ~ 500 ℃ by heat exchange in
Preheated to a degree. The preheated reforming raw material is gasified in the reforming section 14 and passes through the reformed gas generation pipe 27,
It comes into contact with the reforming catalyst filled in the reformed gas generation pipe 27 under heating, and is reformed by a reforming reaction shown in the following “Chemical formula 2”. Embedded image CH ₃ OH + nH ₂ O → (1-n) CO +
nCO ₂ + (2 + n) H ₂ where 0 <n <1 In such reforming, methanol 1
The mixing ratio of 8 to water 23 is desirably set to 0.05 mol to 5 mol of water per 1 mol of methanol. Further, in order to efficiently carry out the reforming reaction of the raw material gas, the pressure in the reformed gas generation pipe 27 is set to about 0 to 20 kgf per square centimeter. Is desirably set to about 200 ° C. to 600 ° C. As the reforming catalyst, for example, platinum (Pt), palladium (Pd) and rhodium (R
h) and one containing at least one element of nickel (Ni), or copper (Cu) and one containing at least one element of zinc (Zn) and chromium (Cr). When the methanol reformer 13 is started, methanol 18 in a methanol tank 17 is supplied in place of unreacted gas from the battery body 11 used for combustion gas. That is, the starting methanol supply pipe 2 connecting the reformer 14 and the methanol tank 17
8 is provided, and the methanol supply pipe 28 for starting is provided.
A starting device 29 is provided in the middle of the process. The starting device 29 includes a starting fuel supply pump (not shown) for pumping methanol 18 in the methanol tank 17 to a nozzle unit (not shown) in the reforming unit 14, and methanol 18 supplied from the starting fuel supply pump. And a methanol vaporizer (not shown) for evaporating and sending the vapor to a nozzle (not shown). On the other hand, a first CO reduction device 30 is provided so as to communicate with the reformed gas outlet side of the methanol reformer 13. The first CO reduction device 30 is filled with a CO shift catalyst for reducing CO in the reformed gas generated by the reforming reaction in the reformed gas generation pipe 27. As the CO shift catalyst, for example, copper (C
u) and those containing at least one element of zinc (Zn). Here, in the CO shift processing in the first CO reduction device 30, CO is converted into CO ₂ by a reaction with H ₂ O, and the CO concentration is reduced to about 1%. The reformed gas supply pipe 31 communicating with the first CO reduction device 30 is connected to a second CO reduction device 32. In the second CO reduction device 32, by introducing air into the reformed gas, as described above, 1%
A process (select oxo) for further reducing the reduced CO to about 100 ppm is performed. The reformed gas thus reduced in CO is sent to the hydrogen electrode 12 of the fuel cell main body 11, and the excess unreacted gas in the reformed gas is removed from the fuel cell main body 11 and the methanol. The gas is supplied to the reforming unit 14 via an unreacted gas supply pipe 34 that communicates with the reforming unit 14 of the reformer 13. On the other hand, a blower 37 is connected to the oxygen electrode 35 of the fuel cell main body 11 via an air supply pipe 36.
The pressurized air from the blower 37 is sent under pressure to the oxygen electrode 35 side. Then, this air is supplied to a steam-water separator 38 connected to the oxygen electrode 35 in a state of containing reaction product water on the oxygen electrode 35 side in the fuel cell main body 11, and water in the water is collected by a water recovery pipe. 39 through the water tank 21
And the gaseous component is discharged from the exhaust pipe 40 to the outside. Here, the blower 37 is driven by a blower drive motor 42 supplied with electricity from a storage battery 41 as a power supply. The storage battery 41 has the first CO
The electricity generated by the generator 44 driven by the exhaust turbine 43 interposed in the reformed gas supply pipe 31 between the reduction device 30 and the second CO reduction device 32 is stored. Further, a second air supply pipe 45 branched from the air supply pipe 36 from the blower 37 communicates with the middle of the methanol supply pipe 28, and the methanol is supplied through the second air supply pipe 45 as described above. Reformer 1
Air serving as combustion gas in the third reforming section 14 is supplied. The motors 19 and 24 are also operated by electricity supplied from the storage battery 41, similarly to the blower drive motor. In the present embodiment, the hot water 47 in the hot water tank 46 is supplied through the hot water circulation pipe 48 to the fuel cell main body 1.
1 is supplied to the above-described hot water passage 8 (see FIG. 1). The hot water 47 is introduced into the hot water passage 8 and then returned to the hot water tank 46. Note that such circulation of the hot water 47 is performed by a pump 50 driven by a motor 49, and the motor 49 is operated by electricity of the storage battery 41. The temperature of the hot water 47 is set to 90
A heating device is provided which can be kept at ° C. When power is generated by such a device, the solid polymer electrolyte membrane 1 is operated while always being kept in a water-containing state, so that the power generation performance is improved. FIG. 5 compares the cell performance of the fuel cell of the above embodiment and the fuel cell of the prior art. The fuel cell according to the above embodiment does not allow hot water to flow through the hot water passage 8,
The performance of the battery is remarkably improved as compared with Comparative Example 1 in which cooling water is supplied to a half of the hydrogen supply groove of the gas separator so as to humidify and supply the hydrogen source reformed gas and contact the gas diffusion electrode on the hydrogen electrode side. are doing. In Comparative Example 2 in which cooling water was flowed in half of the oxygen supply groove of the gas separator so as to further contact the gas diffusion electrode on the oxygen electrode side in Comparative Example 1, although the cell voltage was improved, the cell voltage was 1 A / cm ^2. Although the voltage drops due to lack of oxygen on the high current side, such a problem is solved in the above embodiment. As described above in detail with the embodiments, according to the present invention, the raw material gas supply groove of the gas separator of the solid polymer electrolyte membrane fuel cell body communicates with the raw material gas supply groove via the water vapor permeable membrane. A hot water passage is provided, and steam is introduced into the gas supply groove by flowing hot water through the hot water passage, so that the steam is supplied to the solid polymer electrolyte membrane together with the raw material gas, and the supply of water to the membrane is efficiently performed. As a result, the battery performance can be significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram of a solid polymer electrolyte membrane fuel cell body according to one embodiment of the present invention. FIG. 2 is an external view of the gas separator. FIG. 3 is a schematic view of a solid polymer electrolyte membrane fuel cell body according to another embodiment. FIG. 4 is a conceptual diagram showing the entire system. FIG. 5 is a graph showing the results of a power generation test. FIG. 6 is a conceptual diagram showing a solid polymer electrolyte membrane fuel cell according to the prior art. [Description of Signs] 1 Solid polymer electrolyte membranes 2A, 2B Gas diffusion electrodes 3A, 3B Reaction membranes 4A, 4B Gas diffusion membranes 5, 6 Gas separators 5a Hydrogen supply grooves 5b Through holes 6a Oxygen supply grooves 6b Through holes 7 Water vapor transmission Membrane 8 Hot water passage 10 Water supply passage 11 Fuel cell body 12 Hydrogen electrode 13 Methanol reformer 14 Reforming unit 15 Preheating unit 16 Reforming methanol supply pipe 17 Methanol tank 18 Methanol 21 Water tank 23 Water 30 First CO reduction Apparatus 31 Reformed gas supply pipe 32 Second CO reduction apparatus 35 Oxygen electrode 36 Air supply pipe 46 Hot water tank 47 Hot water 48 Hot water circulation pipe

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-102774 (JP, A) JP-A-6-338338 (JP, A) JP-A-6-275284 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 8/02 H01M 8/04 H01M 8/10

Claims (1)

(57) and bonded body formed by bonding across the solid polymer electrolyte membrane Claims 1. A two gas diffusion electrodes, the surface of one side of the gas diffusion electrode of the assembly Contact
Hydrogen supply to supply hydrogen to the solid polymer electrolyte membrane
Contact the gas separator for the hydrogen side with the passage formed and the surface of the gas diffusion electrode on the other side of the joined body
And supplying oxygen to the solid polymer electrolyte membrane.
A solid polymer electrolyte membrane fuel cell body comprising a gas separator for the oxygen side having a passage formed therein , wherein the gas separator for the hydrogen side and the gas for the oxygen side are provided.
The above gas separator for at least the hydrogen side of the separator
The data separator has water impermeability and the gas separator
Of the supply passage penetrates through the gas separator.
A solid polymer electrolyte membrane fuel cell main body, which communicates with a hot water passage through a hole and a water vapor permeable membrane .