JP3356465B2 - Method for manufacturing electrode for solid polymer electrolyte fuel cell - Google Patents

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 and a method for manufacturing an electrode thereof.

[0002]

2. Description of the Related Art In recent years, fuel cells have attracted attention as high-efficiency energy conversion devices. Depending on the type of electrolyte used for the fuel cell, for example, an alkaline aqueous solution type,
Low-temperature operation fuel cells such as solid polymer electrolyte type and phosphoric acid type, and high-temperature operation fuel cells such as molten carbonate type and solid oxide electrolyte type are roughly classified.

[0003] Among these fuel cells, a solid polymer electrolyte fuel cell using a polymer membrane having proton conductivity as an electrolyte has a compact structure, a high output density, and can be operated by a simple system. Therefore, it has attracted attention as a power source for mobile use such as for space or vehicles.

As the polymer membrane, a polystyrene cation exchange membrane having a sulfonic acid group, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, and a trifluoroethylene grafted trifluoroethylene are known. Recently, a perfluorocarbon sulfonic acid membrane (for example, Nafion: trade name, manufactured by DuPont) or the like has been used.

[0005] A solid polymer electrolyte using such a polymer membrane
Degraded fuel cells are used as gas diffusion layers and catalyst layers.
A pair of porous electrodes having the same function, that is, a fuel electrode and an oxidizer electrode
And sandwich the polymer membrane with the fuel chamber
And a current collector with a groove forming an oxidant chamber
Is a single cell, and such a single cell is
It is configured by stacking several times. By the way, the proto
In a fuel cell, the hydrogen gas supplied from the fuel electrode side
And the oxygen gas supplied from the oxidant electrode side, the fuel electrode: H_Two→ 2H⁺ + 2e^-  Oxidizer electrode: 1/2 O_Two+ 2H⁺ + 2e^- → H_TwoAn electrochemical reaction O 2 occurs. In the above reaction formula,
Electrons move from the fuel electrode to the oxidizer electrode through an external circuit,
Protons move through the electrolyte membrane.

[0006] The movement of protons in a polymer membrane, that is, the ionic conductivity of the membrane greatly depends on the water content of the membrane, and the ionic resistance increases significantly as the water content decreases.
Therefore, it is necessary to supply water to the polymer membrane so that a constant water content can be always maintained.

For this reason, in a conventional solid polymer electrolyte fuel cell having an operating temperature of about 80 ° C., as shown in, for example, JP-A-3-269955, the supply gas is humidified to increase the operating temperature. Do not allow the molecular film to dry,
As disclosed in JP-A 1-309263 and JP-A-4-95357, various measures have been taken, such as supplying water or steam to the polymer membrane from the fuel electrode support side to supply water to the membrane.

[0008] However, in the solid polymer electrolyte fuel cell configured as described above, it is necessary to stably hold water in the polymer membrane or to supply water satisfactorily to the polymer membrane by using only the above means. And the ionic resistance of the polymer membrane increases during the operation of the battery.

[0009]

As described above, in the conventional solid polymer electrolyte fuel cell, not only the water retention performance of the polymer membrane is inferior structurally, but also it is difficult to supply sufficient water, and the It was difficult to operate stably throughout. Accordingly, an object of the present invention is to provide a method for manufacturing an electrode for a solid polymer electrolyte fuel cell, which can solve the above-mentioned problems .
You.

[0010]

Means for Solving the Problems In order to achieve the above object, the invention corresponding to claim 1 provides a gas diffusion layer with water repellency.
A fuel electrode having a region having
In manufacturing, the polymer material which volatilizes by heating
After pre-coating the area to be hydrophilic of the gas diffusion layer
Immerse in a water-repellent treatment solution, and then heat-treat
It is characterized in that a portion is exposed.

[0011]

[0012]

[0013]

[0014]

[0015]

According to the invention corresponding to the first aspect, it is possible to manufacture a fuel electrode which simultaneously exhibits a fuel gas supply function and a water supply function without complicated steps.

[0016]

【Example】

 Example 1

A perfluorocarbon sulfonic acid membrane having a thickness of 0.2 mm was immersed in an aqueous solution of a zirconium phosphate compound at room temperature for one week. FIG. 1 shows the results of differential scanning calorimetry between the untreated film and the film immersed in the zirconium phosphate compound Zr (O ₃ PCH ₂ SO ₃ H) ₂ . As can be seen from FIG. 1, the evaporation of water in the treated film occurs at a higher temperature than in the untreated film, and the evaporation at around 80 ° C. is suppressed.

Next, the treated film is sandwiched between two catalyst-carrying carbon electrodes, and is heated at 180 ° C. and 20 kg / cm ^2. Hot pressing was performed for 3 minutes under the above pressure to produce a unit cell in which the treated film and the electrode were joined.

The manufactured unit cell is humidified in an atmosphere of 80 ° C., and at a current density of 0.2 A / cm ^{2 at} normal temperatures of 60, 80, 100 and 140 ° C. For 100 hours. When the voltage characteristics at each temperature after 100 hours from the start of the operation were examined, the results shown in FIG. 2 were obtained. As can be seen from the figure, the single cell using the treated film has more stable characteristics than the single cell using the untreated film (conventional example) even in a high cell temperature range. Example 2

As a compound having a phosphate group, H ₃ PO ₄
(85 wt%), a processing film was prepared in the same manner as in Example 1, and a single cell using this was assembled and operated under the same conditions. As shown in FIG. Similar stable results were obtained. Example 3

As shown in FIG. 3, using a screen pattern on carbon paper 1 having a porosity of 75%, as shown by hatching 2 in the figure, polyvinyl butyral (PVB)
(20 wt%) was applied.

Next, this was immersed in an aqueous solution of 20 wt% polytetrafluoroethylene (PTFE) and dried. Next, this was heat-treated in air at 320 ° C. for 30 minutes. When water repellency was examined after the treatment, it was found that the area treated with PTFE showed water repellency, and the area treated with PVB (indicated by hatching 2 in FIG. 1) showed hydrophilicity. Observed by seeping.

PTFE is coated on the surface of the carbon paper 1 by 10
Carbon black containing wt% was applied to a thickness of 30 μm.
This coating was performed by a screen printing method in which a slurry containing carbon black was placed on a 250-mesh screen and extruded with a spatula. After drying, a solution obtained by dispersing a platinum-supported carbon catalyst in a solution containing perfluorosulfonic acid on the carbon layer is applied to a thickness of 20 μm by screen printing to obtain a solid polymer electrolyte fuel cell fuel. The pole was made.

Next, an oxidizer electrode was prepared by the following method.
That is, a water slurry composed of carbon black, PTFE, and polyethylene glycol is applied to a water-repellent carbon paper having a porosity of 75% by screen printing to a thickness of 30 μm.
After drying, it was heat-treated at 320 ° C. for 30 minutes.

Next, a solution prepared by dispersing a carbon catalyst carrying platinum in a solution containing perfluorosulfonic acid is applied to the carbon layer by 10 μm by screen printing to form an oxidizing agent for a solid polymer electrolyte fuel cell. The pole was made.

A perfluorosulfonic acid membrane is sandwiched between the oxidizer electrode and the fuel electrode produced as described above, and a 20 kg
/ cm ² A single cell was fabricated by hot pressing at 180 ° C for 3 minutes.

The power generation characteristics were measured while supplying ion-exchanged water to the fuel electrode side of the single cell thus produced.
As a result, the characteristics shown in FIG. 4 were obtained. As can be seen from the figure, the performance of the conventional water-repellent treatment on the entire fuel electrode side (broken line) deteriorated in a short time. However, those partially treated for water repellency as in this example exhibited stable characteristics for a long time.

Although the hydrophilic region is formed in a band shape in this embodiment, it may be formed in an island shape. Also,
The hydrophilic region may be 20 to 80% of the entire area, and water and gas are not sufficiently supplied outside this range.
Good battery characteristics cannot be obtained. Also, when the repeating unit of the hydrophilic region and the water-repellent region is larger than about 10 mm square,
Since the effect of providing the hydrophilic region is reduced, the value needs to be smaller than the above value. In addition, the material for pre-coating the hydrophilic region is not limited to polyvinyl butyral, but volatilizes at a temperature lower than the heat treatment temperature of the water repellent (polytetrafluoroethylene). At room temperature, solid wax or polyethylene is used. You may. Furthermore, the screen is used as a mask to set the hydrophilic area, but the concave or convex part of the roller having the uneven pattern on the surface is made to contain the alcohol solution of PVB in the concave part or the convex part, and the hydrophilic area is transferred by transferring the alcohol solution. May be set. Alternatively, after immersion in a solution of a resin that cures with ultraviolet light or the like, only the portion to which hydrophilicity is to be imparted may be irradiated with ultraviolet light to be cured, and the remaining resin may be washed away to form a hydrophilic region.

In the case where the stacked battery 10 in which a plurality of single cells are stacked as shown in FIG.
As shown in (b), the separator 11 formed of a dense material
A cooling water flow path 12 is provided in the cooling water flow path 12, and the cooling water guided to the cooling water flow path 12 is passed through a humidified water transmission plate 13 formed of a hydrophilic material through a fuel flow path of a fuel distribution plate 14 formed of a hydrophilic material. 15, and the water that seeps into the fuel channel 15 may be supplied to the fuel electrode side of the electrode / polymer membrane integrated plate 16. In the figure, reference numeral 17 is provided on the periphery of the separator 11, the humidified water permeable plate 13, and the fuel distribution plate 14,
A hole provided for a passage for guiding and supplying fuel, air as an oxidant, and cooling water is shown.

[0030]

As described above, according to the present invention, complicated
The fuel gas supply function and the water supply function without the need for complicated processes.
Solid polymer electrolyte capable of producing a fuel electrode that can sometimes be demonstrated
And a method for manufacturing an electrode for a fuel cell.

[Brief description of the drawings]

FIG. 1 shows a polymer film as an electrolyte formed of Zr (O ₃ PCH ₂ S).
O ₃ H) shows the result of differential scanning calorimetry with that of untreated and those obtained by dipping in ₂ aqueous solution

FIG. 2 is a graph showing battery characteristics of a single cell incorporating a polymer membrane subjected to immersion treatment and a single cell incorporating an untreated polymer membrane after operation at each temperature for 100 hours.

FIG. 3 is a diagram for explaining a hydrophilic treatment for a fuel electrode;

FIG. 4 is a diagram showing battery characteristics of a single cell incorporating a fuel electrode having a hydrophilic region and a water-repellent region and a single cell incorporating a fuel electrode subjected to only water-repellent treatment.

FIG. 5 is a diagram for explaining a configuration example of a laminated electric field;

[Explanation of symbols]

 1: carbon paper 2: hydrophilic region

Continuation of the front page (56) References JP-A-5-242898 (JP, A) JP-A-6-196016 (JP, A) JP-A-59-23473 (JP, A) JP-A-3-182052 (JP U.S. Pat. No. 4,466,761 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/86 H01M 4/88 H01M 8/04 H01M 8/10

Claims (1)

(57) [Claims] 1. A water-repellent region and a hydrophilic region in a gas diffusion layer.
In producing an anode having a region having an
A polymer material that evaporates due to heat and is hydrophilic in the gas diffusion layer.
Immersed in water-repellent treatment liquid after pre-coating the area to be treated
And then heat-treated to expose the hydrophilic region
Solid polymer electrolyte characterized by comprising a process
For producing an electrode for a fuel cell.