JPH06119929A - Fuel electrode of solid oxide fuel cell and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Structure] In a solid oxide fuel cell in which an air electrode is formed on one side and a fuel electrode is formed on the other side with a solid electrolyte plate sandwiched between the solid electrolyte plate and the solid electrolyte plate A fuel electrode that is integrally laminated on a metal thin film. In the fuel electrode, a metal thin film or a metal compound thin film is formed on a solid electrolyte, and then the thin film is used as a metal oxide film, and then the fuel electrode composition is applied on the film and then subjected to reduction treatment to form a porous metal oxide film. It is obtained by forming a thin film and forming a fuel electrode. [Effect] Regarding the fuel cell using the above fuel electrode, the polarization resistance does not increase even if the current increases, so there is almost no resistance due to the electrode reaction, and under a predetermined constant current. Polarization resistance is extremely small over time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel electrode for a solid oxide fuel cell and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a solid oxide fuel cell, a method for forming an electrode on a solid electrolyte is usually to apply an electrode composition to an electrolyte such as a zirconia electrolyte in the form of a green sheet by coating and then integrally sinter. And a method of depositing an electrode on a sintered electrolyte such as a sintered zirconia electrolyte by coating or printing.

In the latter deposition method, the polarization resistance increases as the current increases when the battery formed therefrom is generated, and when the battery is operated for a long time, the anode is sintered and peeled from the electrolyte. However, there is a drawback that polarization resistance increases and deterioration progresses with time.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional fuel cell, and suppresses the increase of polarization resistance even when the current becomes large during power generation and the operation is continued for a long time. The purpose of the present invention is to provide a fuel electrode that provides a solid oxide fuel cell that does not deteriorate over time.

[0005]

The inventors of the present invention have conducted various studies to develop a fuel electrode having the above-mentioned preferable characteristics, and as a result, the polarization resistance, which is a drawback of the conventional deposition method, has been increased. , Paying attention to the fact that a strong interface is not formed between the fuel electrode and the electrolyte, and by implementing a unique device for forming a strong fuel electrode / electrolyte interface,
It has been found that the object can be achieved, and the present invention has been completed based on this finding.

That is, the present invention provides a solid electrolyte fuel cell in which an air electrode is formed on one surface and a fuel electrode is formed on the other surface with a solid electrolyte plate sandwiched between them, and a porous material which is in close contact with the surface of the solid electrolyte on the fuel electrode side is used. The present invention provides a fuel electrode for a solid oxide fuel cell, which is integrally laminated on a metal thin film.

The porous metal thin film forming an important constituent layer of the fuel electrode of the present invention is interposed as an interface layer between the electrolyte serving as a substrate or matrix and the fuel electrode, and firmly adhered to the electrolyte itself. It also holds the fuel electrode firmly. The thickness of the porous metal thin film as the interface layer is preferably 10 μm or less, more preferably about 1 to 5 μm.

In the fuel electrode of the present invention, after a metal thin film or a metal compound thin film is formed on the fuel electrode side surface of the solid electrolyte,
The thin film is formed into a metal oxide film, and then the composition for fuel electrode is applied onto the metal oxide film, and then reduction treatment is applied to form the above-mentioned oxide film into a porous metal thin film and to form a fuel electrode. It

In the present invention, the solid electrolyte is preferably a zirconia-based one such as yttria-stabilized zirconia or partially stabilized zirconia. Further, in the method of the present invention, in order to form a metal thin film or a metal compound thin film on the solid electrolyte, plating, electron beam evaporation,
Surface treatment such as spattering is preferable, and it is particularly preferable to use an electroless plating method that can obtain a film having good adhesion and a uniform film thickness.

The thin film thus obtained is a dense thin film made of a metal or a metal compound, and Ni or Co is preferable as the metal constituting the thin film, and the metal compound is a metal oxide or a metal carbide. Are preferred, and nickel oxide and cobalt oxide are particularly preferred.

When an electrode is formed through a thin film according to a conventional deposition method, the adhesive force between the electrode and the electrolyte becomes stronger as compared with the conventional deposition method in which the electrode is directly formed on the electrolyte. . On the other hand, since the thin film is too dense, there is a problem in that the diffusion of the raw material gas, the gas generated in the battery reaction and water is delayed, and the diffusion resistance increases.

Therefore, in the present invention, such a problem is solved by further using the following method. That is, the thin film obtained as described above is used as a metal oxide film, and then the composition for fuel electrode is applied on the metal oxide film, and then reduction treatment is performed to form the oxide film as a porous metal thin film. Together with this, an electrode is formed. As this specific method, a metal thin film is preferably 800 to 1200 ° C.
After about 1 to 10 hours of oxidation and baking to form a metal oxide film, this thin film is used as a fuel electrode / electrolyte interface layer, and the composition for fuel electrode is applied on this thin film, and then 300 to 400 ° C
Binders are burned off in the process of heating up to 800 ℃
By performing a reduction treatment at 1200 ° C., the metal oxide thin film is reduced to make it porous and form a porous metal thin film.
The method of forming a fuel electrode is mentioned. 5-2 reduction process
It is preferable to use nitrogen to which 0% of hydrogen has been added, and the starting time is 80% when the battery is made and the temperature is raised.
It is desirable that the temperature reaches 0 ° C.

[0013]

EXAMPLE 30 A partially stabilized zirconia which is a zirconia prepared by adding 8 mol% of yttria to a solid electrolyte plate 30
A plate-like material having a size of x30x0.2 mm was used. One surface of the solid electrolyte plate was treated with an electroless plating bath for 1 minute to form a 1 μm thick Ni dense film. Next, the film is heated to 1000 ° C.
The film was baked in an air atmosphere for 1 hour to form a nickel oxide film. An Ni / ZrO ₂ (weight ratio 10/1) cermet mixed powder dispersed in an organic binder was applied on the film in an area of 2 cm ² to form a coating composition having a thickness of 0.1 to 0.2 mm. The film was formed. Further, on the other surface of the solid electrolyte plate, within the area of 2 cm ² , La _0.8 S _r0.2
A coating composition in which MnO ₃ powder (average particle size of about 5 μm) was dispersed in an organic binder was applied to a thickness of 0.1 to 0.2 mm to form a cathode forming film.

The electrolyte plate provided with the electrode-forming film thus obtained was integrated with two types of terminal plates of the same size as the solid electrolyte fuel cell. These terminal plates are current collectors having a groove on one side for conducting each raw material gas, that is, La.
_It was composed of a cathode side current collector made of _{0.8 Sr0.2} Cr _0.9 Co _0.1 O ₃ and an anode side current collector made of Inconel 600.

The fuel cell thus manufactured was heated. Heated air flows from room temperature to 350 ℃, 350 ℃
From 800 to 800 ° C, nitrogen gas is flowed to prevent oxidation of the anode on the hydrogen passage side.
H ₂ / N ₂ = 5/50 (cc / min) up to 0 ° C
Flowing mixed gas to reduce, 10 ℃ / m
The temperature was raised in. By this treatment, a porous Ni film was formed and the electrode was formed by firing. Then, the temperature was maintained at 1000 ° C., hydrogen was flown to the anode side and oxygen was flown to the cathode side to start power generation. Table 1 and Table 2 show the polarization characteristics and the polarization characteristics (when the current is a constant current of 1.6 A) with time according to the change in the current of the battery, respectively.

[0016]

[Table 1]

[0017]

[Table 2]

Example 2 A fuel cell was prepared in the same manner as in Example 1 except that the Ni dense film having a thickness of 10 μm was formed by performing the plating treatment on the electrolyte plate for 60 minutes. Similarly, heat treatment was performed to generate power. Table 3 and Table 4 show the polarization characteristics and the polarization characteristics (when the current is a constant current of 1.6 A) with time of the battery, respectively.

[0019]

[Table 3]

[0020]

[Table 4]

From these results, the polarization resistance of the battery of the embodiment does not increase even if the current increases, so that there is almost no resistance due to the electrode reaction, and under the predetermined constant current. It can be seen that the polarization resistance of 1 is extremely small even over time. The polarization voltage itself does not change up to about 100 hours, and increases little by little over 200 hours or only over 100 hours. Therefore, it can be seen that the resistance caused by the electrode reaction is extremely small. It

Comparative Example A coating composition in which the same predetermined cermet powder as in the example was dispersed in an organic binder without inserting a porous Ni film at the interface on the hydrogen passage side of the solid electrolyte plate was prepared in the same manner as in the example. A fuel cell was prepared in the same manner as in Example except that the anode forming film was formed by coating. This fuel cell was subjected to heat treatment and power generation in the same manner as in the example. Table 5 and Table 6 show the polarization characteristics and the polarization characteristics (when the current is a constant current of 1.6 A) with time of the battery, respectively.

[0023]

[Table 5]

[0024]

[Table 6]

As a result, the battery of the comparative example has a larger polarization resistance than the battery having the porous Ni film of the example,
Moreover, since the polarization voltage also increases as the current increases, it can be seen that there is considerable resistance due to the electrode reaction and that the polarization deterioration with time is large.

[0026]

The fuel electrode of the present invention has almost no resistance due to the electrode reaction in the fuel cell using the fuel electrode because the polarization resistance does not increase even if the current increases. Moreover, there is an advantage that the polarization resistance under a predetermined constant current is extremely small even with time.

Front Page Continuation (72) Inventor Motoaki Ando Nishitsurugaoka 1-3-1 Oi-cho, Iruma-gun, Saitama Prefecture Tonen Corporation Research Institute (72) Inventor Toshihiko Yoshida Nishitsurugaoka 3-chome, Oi-cho, Saitama No. 1 Tonen Co., Ltd. Research Institute

Claims (2)

[Claims] 1. An air electrode on one side of a solid electrolyte plate,
A solid electrolyte fuel cell having a fuel electrode formed on the other surface, wherein the fuel electrode of the solid electrolyte fuel cell is laminated and integrated on a porous metal thin film that is in close contact with the surface of the solid electrolyte on the fuel electrode side. 2. A metal thin film or a metal compound thin film is formed on the fuel electrode side surface of the solid electrolyte, the thin film is used as a metal oxide film, and then the fuel electrode composition is applied on the metal oxide film. A method for producing a fuel electrode of a solid oxide fuel cell, which comprises subjecting the above-mentioned oxide film to a porous metal thin film by a reduction treatment and forming a fuel electrode.