JPH09223507A - Solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell-whose structure can be simplified and on which size reduction can be attained by simplifying the constitution of a unit cell, and integrally forming a humidifying part and a power generation part. SOLUTION: A unit cell is constituted in such as way that a negative electrode 2 is formed on an inside surface of hollow yarn 1 of solid polymer electrolyte, and a positive electrode 3 is formed on an outside surface, and fuel is supplied to the negative electrode side, and an oxidizing agent is supplied to the positive electrode side. Mutual electrodes formed on an outside surface and mutual electrodes formed on an inside surface in this unit cell are respectively connected in parallel to each other, and are formed as parallel connection cell groups, and the cell groups are also connected in series to each other. A solid polymer fuel cell constituted so that a part of the hollow yarn 1 of the polymer electrolyte is formed as a humidifying part 7 and the other part is formed as a power generation part 6 is formed. Therefore, a structure of the solid polymer fuel cell is simplified, and size reduction can be attained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to pure hydrogen as a fuel,
Alternatively, the present invention relates to the configuration of a solid polymer fuel cell using a reducing agent such as reformed hydrogen from methanol or fossil fuel and using air or oxygen as an oxidant.

[0002]

2. Description of the Related Art A conventional polymer electrolyte fuel cell uses an ion exchange membrane, which is a polymer electrolyte, as an electrolyte, and its general structure is shown in FIG. In the configuration using the conventional ion exchange membrane 9, the positive electrode 3 or the negative electrode 2 is formed in layers on both sides of the ion exchange membrane 9, and the unit battery 10 has a sheet-like planar structure. As shown in FIG. 6, the unit battery 10 is laminated by gas sealing with a separator plate 11 and a gasket 12 sandwiched therebetween.

When hydrogen is used as a fuel in this fuel cell, the reaction represented by the formula (Formula 1) occurs at the contact interface between the catalyst and the polymer electrolyte in the negative electrode.

[0004]

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When oxygen is used as the oxidant, the positive electrode undergoes the reaction represented by the formula (Formula 2) to produce water.

[0006]

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The catalyst serves as an active site of the reaction, the electrode layer serves as a conductor of electrons in the above reaction, and the polymer electrolyte serves as a conductor of hydrogen ions.

However, a commonly used polymer electrolyte has practical ion permeability only when it contains water. Therefore, methods for humidifying this polymer electrolyte have been widely studied. As represented by US Pat. No. 5,252,410, the unit battery 10 is connected in series with a separator plate 11 and a gasket 12 as shown in FIG.
A laminated body 13 as shown in (1) is formed and tightened with the end plate 14 to form one power generation unit. Oxygen as an oxidant is supplied into the manifold portion 15 of this unit, and hydrogen as a fuel is supplied to the manifold portion 16. In the above-mentioned U.S. patent, the fuel and oxidizer humidifying section is integrally formed with the power generating section of the laminate and the end plate. The humidifying section supplies the fuel or the oxidant to one surface of the ion exchange membrane and the water to the other side, and humidifies the fuel or the oxidant by utilizing the property that the membrane permeates only water. . The humidifying method disclosed in JP-A-5-54900 includes a power atomizer having a nozzle for spraying pressurized water in a fuel or oxidant gas supply passage, or an ultrasonic humidifier having a water surface for producing extremely fine mist. did. JP-A-6-33
In the humidification method disclosed in Japanese Patent No. 8338, a porous fuel distribution plate or oxidizer distribution plate is installed between a separator plate and a unit cell, and water is supplied to the inside of a distribution slope to humidify it through fine holes in the distribution plate. It was configured. Further, Japanese Patent Application Laid-Open No. 7-245116 discloses that a fuel cell is made compact by installing a humidifying device using a hollow fiber membrane in a stack of a laminated battery. Further, in US Pat. No. 5,262,250, a thin path is passed through the inside of the ion exchange membrane, and water is supplied to this path for humidification.

[0009]

However, in the structure of the above-mentioned conventional polymer electrolyte fuel cell, as shown in FIG. 6, a member for preventing mixing of reaction gases and electrically connecting the unit cells 10 together. The separator plate 11 is required. However, since the polymer electrolyte exhibits acidity due to the nature of the sulfone group which is the ion exchange group,
The carbon material and the titanium material are used because they are acid resistant and need conductivity. Since these materials have poor processability and are expensive, they are one of the problems that increase the cost of the fuel cell body. Also, as a member for stacking, a gasket 1 is used for gas sealing of each part.
2 is required. For each unit battery 10, a positive or negative electrode part, a fuel or oxidizer manifold part 15 or 16
It is necessary to separate and seal each independently,
The gasket 12 has a complicated and precise shape. Therefore, there is a problem that further increases the cost and makes the assembly difficult.

Further, in the structure of the humidifying part of the above-described conventional polymer electrolyte fuel cell, when the membrane humidification is performed, there is a problem of the separator plate and the gasket as in the case of stacking the unit cells, and the spraying device is used. In addition to complicating the system when using a porous plate, a porous plate, or ultrasonic humidification, it is necessary to cover the power source required for the pressurizing device, ultrasonic oscillator, etc. from the output of the fuel cell body, resulting in poor performance. Had the problem of leading to.

The present invention solves such a conventional problem, and simplifies the structure of the unit battery and further integrates the humidifying part and the power generating part into the battery, thereby simplifying the structure and enabling downsizing. It is an object of the present invention to provide a polymer electrolyte fuel cell having the above structure.

[0012]

In order to solve the above problems, the present invention forms a negative electrode on the inner surface or the outer surface of a hollow fiber made of a solid polymer electrolyte and a positive electrode on the other surface to form a hollow fiber negative electrode. It is a polymer electrolyte fuel cell in which the fuel is supplied to the surface and the oxidant is supplied to the surface where the positive electrode is formed.

Further, the present invention is a polymer electrolyte fuel cell in which a power generation part is formed in a part of a hollow fiber made of a solid polymer electrolyte and the other part is used as a humidification part.

According to the present invention, the constitution of the unit cell can be simplified, and a small size and high performance polymer electrolyte fuel cell can be obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer electrolyte fuel cell according to claim 1 of the present invention comprises a hollow fiber made of a solid polymer electrolyte having a negative electrode on the inner or outer surface and a positive electrode on the other surface.
This is a configuration in which the fuel is supplied to the surface of the hollow fiber on which the negative electrode is formed and the oxidant is supplied to the surface of the hollow fiber on which the positive electrode is formed. According to this structure, since the part to which the fuel is supplied and the part to which the oxidant is supplied are completely separated by the hollow fiber, the gas seal can be achieved without using a special separator or a gasket having an expensive and complicated structure. Since there is no gas seal portion, the gas is not mixed and the performance is not deteriorated.

The invention according to claim 2 is a structure in which the electrodes formed on the inner surface of the hollow fiber of claim 1 and the electrodes formed on the outer surface are connected in parallel by bundling, respectively, and are easily connected in parallel. It is possible to

The invention according to claim 3 has a constitution in which the negative electrode and the positive electrode formed on each surface of the hollow fiber of claim 1 are respectively connected in series, and the battery voltage can be easily increased without using a special separator structure. It is possible to

According to a fifth aspect of the invention, the power generation part is formed in a part of the hollow fiber of the first aspect, and the other part is used as a humidification part, which facilitates the humidification structure and the fuel. The fuel cell system body can be miniaturized by integrating the cell structure.

According to a sixth aspect of the invention, at least one of the negative electrode and the positive electrode of the first aspect has a layered structure in which at least two layers of a catalyst layer and a gas diffusion layer are alternately laminated, and the reaction gas diffusion capacity is improved. The current density is improved due to the decrease in concentration polarization. Furthermore, by making the gas diffusion layer have a stronger water repellency than the catalyst layer, the diffusion capacity of the reaction gas is further improved.

(Embodiment 1) FIG. 1 shows a perspective view of an internal cross section of a fuel cell according to Embodiment 1 of the present invention, which is partially cut away.

In FIG. 1, reference numeral 1 denotes a hollow fiber made of a solid polymer electrolyte. A negative electrode 2 is formed on the inner surface of the polymer electrolyte hollow fiber 1 and a positive electrode 3 is formed on the outer surface thereof. The negative electrode 2 is provided with the negative electrode terminal 4, and the positive electrode 3 is provided with the positive electrode terminal 5.
Hydrogen, which is a fuel, is supplied to the inner surface of the polymer electrolyte hollow fiber 1 in which the positive electrode 3 is formed, and air, which is an oxidant, is supplied to the outer surface, where the positive electrode 3 is formed, to form a power generation unit.

(Embodiment 2) FIG. 2 shows a perspective view of an example in which the unit cells of the fuel cell shown in FIG. 1 of Embodiment 2 of the present invention are arranged.

In FIG. 2, the positive electrode terminal 4 and the negative electrode terminal 5 of 14 unit batteries are bundled and connected in parallel to form a parallel connected battery group. Further, the parallel connected battery group is connected in series with another parallel connected battery group.

(Embodiment 3) FIG. 3 is a perspective view showing an example of a structure including a power generation section 6 and a humidification section 7 of a fuel cell according to Embodiment 3 of the present invention. Further, FIG. 4 shows a sectional view of an example of a battery in which the battery of FIG. 3 is casing.

3 and 4, the polymer electrolyte hollow fiber 1 is shown.
The positive electrode 3 and the negative electrode 2 are formed in a part of the above to form a power generation part 6, and the other part is formed as a humidification part 7. Air as an oxidizing agent is supplied to the outer surface of the polymer electrolyte hollow fiber 1 of the power generation section 6, and pure water is supplied to the outer surface of the polymer electrolyte hollow fiber 1 of the humidification section 7. Hydrogen as a fuel is supplied to the inner surface of the polymer electrolyte hollow fiber 1, and hydrogen passing through the inner surface of the polymer electrolyte hollow fiber 1 is humidified by the humidifying section 7 due to the property that only pure water of the polymer electrolyte permeates. The humidified hydrogen is supplied to the power generation unit 6.

[0026]

The present invention will be described in more detail with reference to the following examples.

(Example 1) A unit cell of a polymer electrolyte fuel cell according to an example of the present invention was produced with a structure shown in FIG. As the polymer electrolyte hollow fiber 1, SUNSEP-W ™ manufactured by Asahi Glass Engineering Co., Ltd.
A hollow fiber having a diameter of 5 mm, an inner diameter of 0.35 mm and a length of 12 cm was masked at both ends of 1 cm, and then immersed in a Pt electroless plating bath to form a negative electrode 2 and a positive electrode 3 on the inner and outer surfaces of the polymer electrolyte hollow fiber 1. Was formed into a catalyst layer. The loading amount of Pt was 0.5 mg / cm ² per membrane surface area in both electrodes.
And A Ti wire was connected to each electrode to collect current.

Example 2 The fuel cell of Example 1 was immersed in a dispersion of polytetrafluoroethylene (PTFE) or a copolymer of polytetrafluoroethylene and polyhexafluoropropylene (FEP) to form a catalyst layer. A polymer electrolyte fuel cell of the present invention was produced with the same configuration as in Example 1 except that a water-repellent gas diffusion layer was formed on the surface.

Example 3 As shown in FIG. 2, the positive electrode terminals 5 and the negative electrode terminals 4 of the 14 unit batteries prepared in Example 2 were bundled and connected in parallel to form a parallel connected battery group. Furthermore, the parallel-connected battery group was connected in series with the other nine parallel-connected battery groups.

(Example 4) In the same manner as in Example 2, after masking 1 cm at both ends and 5 cm to be the humidified portion in a polymer electrolyte hollow fiber having a total length of 17 cm, the remaining 10
cm to form a power generation unit in the same manner as in Example 2, and 10c
A unit battery having a power generation part of m and a humidification part of 5 cm was produced. FIG. 3 shows a state in which the unit batteries are connected in parallel as in the third embodiment. Further, the batteries connected in parallel were cased by a casing 8. FIG. 4 shows a cross-sectional view of the casingd battery. In the figure, hydrogen is supplied to the inner surface of the polymer electrolyte hollow fiber 1, pure water is injected into the humidifying section 7 on the outer surface, and air is supplied into the power generation section 6. With such a configuration,
Hydrogen is humidified by the pure water that has passed through the polymer electrolyte in the humidifying section 7, and is supplied to the power generation section 6 in a humidified state.

Comparative Example 1 Pt-supported carbon fine powder and a polymer electrolyte alcohol solution (manufactured by Aldrich Co.) were mixed to form a paste, which was applied to a conductive carbon paper to form an electrode. The amount of platinum catalyst was 0.5 mg / cm ^{2 in} terms of platinum weight per electrode area for both electrodes. The amount of the polymer electrolyte added was 1.0 mg / cm ² per electrode area. These electrodes and the ion exchange membrane are 120 to 150 ° C., 20 to 200 kg
The negative electrode, the ion-exchange membrane, and the positive electrode were bonded simultaneously by hot pressing at / cm ² . The negative electrode and the positive electrode were electrodes of the same type. The unit cell of the polymer electrolyte fuel cell shown in FIG. 5 was produced using these bonded bodies. In the figure, 2 is the negative electrode,
3 is a positive electrode, and the ion exchange membrane of 9 was Nafion 115 manufactured by DuPont, USA. Area of electrode is 10 cm
^{And 2} .

Comparative Example 2 A unit cell of Comparative Example 1 was laminated with 10 cells as shown in FIG. 7 to prepare a laminated cell as a comparative cell.

Hydrogen gas humidified at a temperature of 60 ° C. was supplied to the negative electrode side of the unit cells of Examples 1 to 3 and Comparative Example 1 of the present invention, and air humidified at a temperature of 60 ° C. was supplied to the positive electrode side. The discharge test was conducted. In addition, in Example 4, hydrogen and air that were not humidified were supplied.

[0034]

[Table 1]

Fuel used in Examples and Comparative Examples of the present invention
The results of discharging the battery are shown in (Table 1). Comparative Example 1
The unit battery has an open circuit voltage of 0.95 V and the unit battery voltage
Current density is 520mA / cm at 0.5V^TwoIn
On the other hand, the open circuit voltage of Example 1 is 1.01V.
However, the current density when the unit cell voltage is 0.5 V is 61
0 mA / cm^TwoMet. Calculation of the current density of this example
It was calculated based on the area of the electrode outside the hollow fiber. Of the embodiment
The reaction area per unit cell is about 1.6 cm ^TwoIn
You.

As a result, it is considered that in the comparative example, the open circuit voltage was lowered to 1 V or less due to a slight mixture of hydrogen and air due to the poor gas sealing of the gasket. On the other hand, in the example, hydrogen and air are completely separated by the polymer electrolyte hollow fiber, it is not necessary to have a gasket part, and an open circuit voltage of 1 V or more is obtained because no defective sealing occurs. It is considered that the diffusion path became shorter and the current density also increased.

The unit cell of Example 2 had a current density of 650 mA / cm ² , which was higher than that of Example 1. It is considered that since the water-repellent diffusion layer was added to the surface of the catalyst layer of the electrode, the diffusion capacity of the reaction gas was improved, the concentration polarization was decreased, and the current density was improved.

In Example 3, the unit cells were connected in parallel and in series. The total open circuit voltage was 10.1 V, the current density when the unit cell voltage was 0.5 V was 630 mA / cm ² , and an output of 143 W was obtained. As described above, the performance deterioration due to the connection of the plurality of batteries was slight.

Example 4 has a constitution in which the same polymer electrolyte hollow fiber is used for humidification. The open circuit voltage at this time is 1.00 V, and the current when the unit cell voltage is 0.5 V. The density was 635 mA / cm ² . The total volume of the battery of the humidifying part type was 20 cm ³ (length 20 cm, height 1 cm, width 1 cm), and an output of 14.2 W was obtained. The output per unit volume was 0.71 W / cm ³ . On the other hand, the volume of the laminated battery of Comparative Example 2 is 320 cm.
³ (8 cm long, 5 cm high, 8 cm wide), 25
An output of W was obtained. Output per unit volume is 0.07
It was 8 W / cm ³ . From these results, comparing the performance per unit volume, although the humidifying section is integrated in the configuration of Example 4 of the present invention, 9 of the conventional laminated battery of Comparative Example 2 having no humidifying section is provided. Double output was obtained.
Therefore, when obtaining the same output, it can be said that the size can be remarkably reduced by a factor of 9.

However, since the constitutions of the examples and comparative examples are not fully optimized constitutions, it is expected that the numerical values of the above-mentioned examples and comparative examples may differ by adding various improvements. The superiority of the configuration can be sufficiently guaranteed.

In this embodiment, the negative electrode was formed on the inner surface of the polymer electrolyte hollow fiber, and the positive electrode was formed on the outer surface. However, the positive and negative electrodes are not limited to this, and the positive electrode is formed on the inner surface. A negative electrode may be formed on the outer surface.

Further, the material and the manufacturing method of the polymer electrolyte hollow fiber and the catalyst of the present invention are not limited to this embodiment, and other materials and manufacturing methods may be used as long as they have the same function. it can.

Further, in this embodiment, the hydrogen-air fuel cell was taken up as an example of the polymer electrolyte fuel cell.
Fuel cells that use reformed hydrogen that uses methanol, natural gas, naphtha, propane, etc. as fuels, fuel cells that use oxygen as an oxidant, and fuel cells that directly react liquid fuels such as methanol. It can also be applied to a polymer electrolyte fuel cell.

[0044]

As described above, according to the structure of the present invention, the portion to which the fuel is supplied and the portion to which the oxidant is supplied are completely separated by the hollow fiber made of the solid polymer electrolyte. Gas sealing is possible without using a unique gasket structure. Also, these unit batteries can be easily connected in parallel by bundling them so that the electrodes on the same side are in contact, and the battery voltage can be easily connected by connecting these parallel-connected batteries in series without using a special separator structure. Can be increased. Further, by constructing a part of the hollow fiber as a power generation part and another part as a humidification part, the humidification structure and the fuel cell structure can be easily integrated, and the structure can be simplified and downsized. A polymer electrolyte fuel cell can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cutaway internal cross-section of a fuel cell according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of an arrangement configuration concept of a fuel cell according to an embodiment of the present invention.

FIG. 3 is a perspective view showing an example of the configuration of a fuel cell according to an embodiment of the present invention.

FIG. 4 is a sectional view showing an example of the configuration of a fuel cell according to an embodiment of the present invention.

FIG. 5 is a sectional view of a unit cell of a fuel cell using a conventional solid polymer electrolyte membrane.

FIG. 6 is a cross-sectional view of a unit cell of a fuel cell stack using a conventional solid polymer electrolyte membrane.

FIG. 7 is an assembled perspective view of a stack of a fuel cell using a conventional solid polymer electrolyte membrane.

[Explanation of symbols]

 1 Solid Polymer Electrolyte Hollow Fiber 2 Negative Electrode 3 Positive Electrode 4 Negative Terminal 5 Positive Electrode Terminal 6 Power Generation Section 7 Humidification Section 8 Case 9 Ion Exchange Membrane 10 Unit Battery 11 Separator Plate 12 Gasket 13 Laminate 14 End Plate 15 Manifold 16 Manifold

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuo Eda 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A hollow fiber made of a solid polymer electrolyte is provided with a negative electrode on the inner or outer surface and a positive electrode is formed on the other surface to form a power generation section, and a fuel and a positive electrode are formed on the surface of the hollow fiber on which the negative electrode is formed. A polymer electrolyte fuel cell that supplies an oxidant to the surface. 2. The polymer electrolyte fuel cell according to claim 1, wherein the electrodes formed on the outer surfaces of the plurality of hollow fibers and the electrodes formed on the inner surfaces are connected in parallel. 3. The polymer electrolyte fuel cell according to claim 1, wherein a positive electrode and a negative electrode formed on each surface of the hollow fiber are connected in series. 4. The polymer electrolyte fuel cell according to claim 1, wherein a negative electrode is formed on the inner surface of the hollow fiber and a positive electrode is formed on the outer surface. 5. The polymer electrolyte fuel cell according to claim 1, wherein the power generation part is formed in a part of the hollow fiber and the other part is used as a humidification part. 6. The polymer electrolyte fuel cell according to claim 1, wherein at least one of the negative electrode and the positive electrode has a layered structure in which at least two catalyst layers and gas diffusion layers are alternately laminated. 7. The polymer electrolyte fuel cell according to claim 6, wherein the gas diffusion layer has a structure having stronger water repellency than the catalyst layer.