JPH05190184A - Electrode-electrolyte joint body, manufacture thereof, and fuel cell using thereof - Google Patents

Abstract

PURPOSE:To improve the water feeding faculty to an electrolyte film and improve the power generation performnce of a fuel battery by forming the part having an electrode catalytic layer from an electrolyte of a solid electrolyte film consisting of only one layer part of a solid electrolyte film. CONSTITUTION:An electrode catalytic paste is applied on a solid electrolyte film through the screen printing, spraying method, coating method, etc., and an electrode catalytic layer part A on which an electrolyte catalytic layer is formed and a water feeding area B consisting of only one layer of tale solid high polymeric electrolyte film are formed. As the electrode catalytic paste, is used the paste which is formed by dispersing the platinum group metal. powders, carbon black, etc., into the solution of an ion exchange film. Accordingly, the water feeding faculty to the electrolyte film is improved to prevent the drying in the electrolyte film, and the power generation performance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode-electrolyte assembly and a method for producing the same, and in particular, it has an excellent ability to supply water to the electrolyte membrane even on the side of the anode that requires water repellency and adhesiveness. The present invention relates to an electrode-electrolyte assembly capable of improving power generation performance and a method for manufacturing the same.

[0002]

2. Description of the Related Art A fuel cell is generally formed by stacking unit cells, ie, cells, each having an electrolyte membrane and an anode and a cathode provided on both sides thereof, that is, a cell.

The reaction gas consists of fuel gas and oxidant gas, and the fuel gas is supplied to the anode side of the separator.
On the other hand, the oxidant gas is supplied to the cathode side of the separator. As a result of such supply of the reaction gas, electrons are generated as the electrochemical reaction progresses, and the electrons are taken out to an external circuit to generate electric energy.

As such a fuel cell, it is conceivable that an electrolyte membrane is formed of a solid polymer electrolyte membrane such as an ion exchange membrane, and an electrode catalyst layer is formed thereon.

[0005] In such a fuel cell, the inside of the electrolyte membrane involving mobile H ⁺ 1 piece per of n H ₂ O in the H ⁺ moves. This number is defined as the electroosmotic coefficient (β). When β decreases, the ionic conductivity of the electrolyte membrane decreases, and the membrane resistance of the electrolyte membrane itself increases. As a result, heat is generated due to the membrane resistance, the temperature rise in the electrolyte membrane further reduces the water content in the electrolyte membrane, and the reduction of β is promoted. This causes the solid polymer electrolyte membrane fuel cell to be difficult to operate in a high current density region.

Further, in the electrode catalyst layer, since H ₂ is adsorbed and atomic (H ₂ ) undergoes an ionization (2H ⁺ + 2e ⁻ ) reaction, an adsorption site of H ₂ must be secured. Therefore, the electrode catalyst layer is required to have a certain degree of water repellency.

Further, a material having an adhesive property is required to keep the shape of the electrolyte membrane in a predetermined thickness by using the electrode catalyst layer as a layer.

As described above, from the viewpoint of both the water repellent property and the adhesive property and the nonreactivity to the electrolyte membrane, the fluororesin such as polytetrafluoroethylene is effective as the adhesive.

However, in the solid polymer electrolyte membrane fuel cell, since it is required to move H ₂ O and maintain the water content in the electrolyte membrane as described above, it is indispensable for H ₂ O to enter the electrolyte membrane. Is.

Conventionally, as a solid polymer electrolyte membrane fuel cell in which the water content of such an electrolyte membrane is kept within a certain range, a solid high fuel cell capable of supplying water to the anode side and simultaneously cooling it. Molecular electrolyte membrane fuel cell (Patent Document 1
No. 309263), a solid polymer electrolyte membrane fuel cell in which a water supply groove is provided between hydrogen supply grooves with respect to a gas separator to be brought into close contact with an anode electrode (JP-A-3-1027).
No. 74), and a solid polymer electrolyte membrane fuel cell [FC Se having an electrode part and a humidifying part on the same electrolyte plate surface].
minar, 330 (1988)] and the like.

However, in the fuel cells disclosed in these prior arts, it is difficult for the electrode catalyst layer to solve these contradictory requirements of water repellent property, tackiness and maintenance of water content. In addition, the characteristics of both the electrolyte layer and the electrode catalyst layer cannot be used up completely. For example, FC Sem
In the solid polymer electrolyte membrane fuel cell of inar, 330 (1988), the electrode part and the humidifying part belong to different areas even on the same electrolyte plate surface, and since the functions are independent, the electrode part and the humidifying part are also humidified. The water content in the electrolyte may differ depending on the distance from the portion, and the structure becomes complicated, so it is difficult to say that the water supply capacity can be sufficiently exhibited.

Further, under the operating conditions of the solid polymer electrolyte membrane fuel cell, the electrolyte plate shows a remarkable decrease in the water content on the anode side, which suggests that the water supply on the anode side is necessary. It can be said that there is.

[0013]

The present invention has been made against the background of the above-mentioned conventional techniques, and enhances the water supply capacity to the electrolyte membrane, and prevents the drying due to the decrease of the water content in the electrolyte membrane. An electrode that can prevent moisture and can supply water into the electrolyte membrane even when an electrode catalyst layer having a high water drainage capacity is used.
It is an object of the present invention to provide an electrolyte joined body, a method for producing the same, and a fuel cell using the same.

[0014]

Means for Solving the Problems The present invention relates to an electrode-electrolyte assembly in which an electrode catalyst layer is formed on a solid polymer electrolyte membrane, a portion where the electrode catalyst layer is formed and a solid polymer electrolyte membrane which is not formed. An electrode-electrolyte assembly using a solid polymer electrolyte membrane as an electrolyte, which has a portion having only one molecular electrolyte membrane, and a method for producing the same, and a fuel cell using the same.

A fuel cell according to one embodiment of the present invention typically forms a laminate in which a plurality of electrolyte membranes and separators are alternately laminated, and has fuel gas inlets and outlets at both ends, and It has a structure in which a manifold having an inflow port and an outflow port for the oxidant gas is attached. A cell of such a fuel cell is composed of one electrolyte plate and electrode catalyst layers arranged on both sides thereof.

FIG. 1 shows the layer structure of the electrode-electrolyte assembly which can be used in the fuel cell of the present invention. The electrode-electrolyte assembly 1 comprises an electrolyte membrane 1a and electrode catalyst layers 1b on both sides thereof. It is effective to use a solid polymer electrolyte membrane as the electrolyte membrane, and the thickness thereof is approximately 50 to 2
It is about 00 μm.

The electrode catalyst layer 1b is formed from a paste prepared by dispersing a platinum group metal powder, carbon black or a platinum group metal supported on carbon black in a solution of an ion exchange membrane. The above-mentioned paste is a solution of a fluororesin such as 1 to 200 parts by weight of platinum group metal powder, 1 to 500 parts by weight of carbon black, and polytetrafluoroethylene per 100 parts by weight of the solid content of the solution of the above-mentioned ion exchange membrane resin (dry). It can be produced by mixing 1 to 200 parts by weight). In addition to the platinum group metal, an alloy with another metal can also be used.

Next, the above-mentioned electrode catalyst paste is applied onto the electrolyte membrane 1a by screen printing, spraying, coating or the like as shown in FIGS. 2 and 3, thereby forming an electrode catalyst layer. A and a water supply area B which is not formed and consists of only one layer of the solid polymer electrolyte membrane are formed. The amount of paste applied by the screen printing method is about 0.5 to ²⁰ mg / cm ^{2 in} dry weight. According to this method, both the electrode catalyst layer and the water supply area can be adjacent to each other on the same surface, and the printing or coating pattern can be freely selected.

The electrode-electrolyte assembly 1 thus obtained is usually subjected to a heat and pressure treatment such as hot pressing. The conditions of the heating and pressurizing treatment are a temperature of 60 to 20.
0 ° C, pressure 50-300kg / cm ² , preferably temperature 100-120 ° C, pressure 100-150k
It is about g / cm ² .

Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this and can be applied to various types of stacked fuel cells.

[0021]

The present invention will be described in more detail by the following examples. Example 1 2 g of platinum black, 1 g of carbon black, and 1 g of polytetrafluoroethylene powder were mixed with 40 m of a Nafion (registered trademark) solution (5% by weight solution manufactured by Aldrich).
It mixed with 1 and prepared the paste for electrode catalysts.

Next, 10 cm of Nafion (registered trademark)
A × 10 cm film (thickness: 175 μm) was washed with acetone, subsequently treated with hydrochloric acid, and then dried. On the other hand, with a sputtering device, the size of 50 mmφ
A plasma etching process was performed for a minute.

The above-mentioned paste was pattern-printed on this film by a cut-out plate making screen to a size of 50 mmφ. Furthermore, it is 10 with a heating press.
Hot pressing was performed at 0 ° C. and 150 kg / cm ² for 1 minute to obtain an electrode-electrolyte assembly for a fuel cell having a thickness of about 230 μm.

[0024]

As described above in detail, the electrode of the present invention
The electrolyte assembly enhances the ability to supply water to the electrolyte membrane, prevents drying due to a decrease in the water content in the electrolyte membrane, and even when using an electrode catalyst layer with high water repellent and adhesive ability The fuel cell can be supplied, and further the power generation performance of the fuel cell can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a layer structure of an electrode-electrolyte assembly used in a fuel cell of the present invention.

FIG. 2 is a schematic surface view of an electrode-electrolyte assembly used in the fuel cell of the present invention.

FIG. 3 is a schematic cross-sectional view on the electrode side of an electrode-electrolyte assembly used in the fuel cell of the present invention.

[Explanation of symbols]

 1 Electrode-Electrolyte Assembly 1a Electrolyte Membrane 1b Electrolytic Catalyst Layer A Electrode Catalyst Layer Part B Water Supply Area

Claims (3)

[Claims] 1. In an electrode-electrolyte assembly in which an electrode catalyst layer is formed on a solid polymer electrolyte membrane, a portion where an electrode catalyst layer is formed and a portion where the electrode catalyst layer is not formed and only one solid polymer electrolyte membrane is formed. There is an electrode-electrolyte assembly using a solid polymer electrolyte membrane as an electrolyte. 2. The electrode catalyst layer is formed by applying a paste electrode catalyst.
A method for producing the described electrode-electrolyte assembly. 3. A fuel cell comprising the electrode-electrolyte assembly according to claim 1.