JPH04357163A - Production of porous ceramic electrode - Google Patents

Abstract

PURPOSE:To form a porous electrode excellent in gas diffusibility and electrical conductivity. CONSTITUTION:A slurry 8 composed of a perovskite-type compound oxide having a particle size adjusted to a suitable value is put in a vessel 7 and a porous substrate 2 is then immersed therein for a sufficiently long time while uniformly stirring the slurry 8 by rotating a magnetic bar 9 using a stirrer 10. An uncalcined perovskite-type compound oxide layer is formed on the surface of the porous substrate 2 and film formation is carried out after sufficiently drying the resultant layer in a condition where cracking can be prevented by calcining the dried layer, thus obtaining the objective porous electrode.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode for an element that ionizes gas molecules, such as a fuel cell, an oxygen separation element, or a gas sensor.

0002

[Prior Art] In fuel cells and oxygen separation elements, gas can permeate both sides of a solid electrolyte membrane that is dense enough to allow hydrogen ions and oxygen ions to pass through, but not to allow non-ionized oxygen and hydrogen gases to pass through. It has a structure in which a moderately rough porous electrode layer is formed. Such a porous electrode layer is formed on the surface of a porous base material or a dense solid electrolyte base material by a thermal spraying method.

0003

Problems to be Solved by the Invention Characteristics required for electrodes of fuel cells and oxygen separation elements are excellent gas permeability and electrical conductivity. For this purpose, the average pore diameter should be set to about 0.1 to 10 μm, and the porosity should be set to 10 to 50 vol.
%. However, when an electrode layer is formed by conventional thermal spraying, it is not possible to control the size of the constituent particles of the electrode layer, resulting in an extremely dense structure that reduces gas permeability and improves the efficiency of fuel cells and oxygen separation elements. becomes worse.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention prepares a slurry by kneading perovskite type composite oxide powder with a particle size distribution of 0.5 to 20 μm in a solvent together with a binder. The base material is immersed in the slurry and pulled up to adhere an unfired perovskite composite oxide layer to the surface of the base material, and then after drying this layer,
The firing was carried out at a temperature of 00°C to 1500°C.

[0005]

[Operation] Since the electrode layer is formed by the dipping method, the particle size of the perovskite-type composite oxide that makes up the electrode layer can be controlled, and the pore size and porosity after firing are suitable for use as electrodes for fuel cells and oxygen separation elements. It satisfies the required characteristics.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of an oxygen separation element having a porous electrode formed by the method of the present invention, and FIG. 2 is a diagram showing the particle structure of the porous electrode.

The oxygen separation element 1 has a porous electrode 3 that is also permeable to gas formed on the surface of a cylindrical porous support 2 that is permeable to gas, and allows only oxygen ions to pass through the surface of the porous electrode 3. A dense solid electrolyte layer 4 that does not allow the permeation of oxygen gas in a molecular state is formed, and a porous electrode 5 that allows gas permeation is formed on the surface of this solid electrolyte layer 4. One of the porous electrodes 3 and 5 is used as an anode electrode and the other as a cathode electrode.

[0008]The solid electrolyte layer 4 partitions the low-oxygen side region S1 and the high-oxygen side region S2, and by applying a voltage between the porous electrodes 3 and 5, the oxygen in the low-oxygen side region S1 is removed. Move as ions to the high oxygen side region S2 through the solid electrolyte layer 4

The porous support 2 is produced by extruding a ceramic compound such as alumina to obtain an unfired molded body, and then firing this molded body by a method such as hanging firing.

Furthermore, as shown in FIG. 2, the porous electrode 3 has constituent particles (black parts in the figure) that are sufficiently bonded to each other, and
A predetermined average pore diameter and porosity are ensured. To form such a porous electrode, as shown in FIG. 3, a slurry 7 made of a perovskite-type composite oxide is placed in a container 6, and a stirrer 9 is rotated using a stirrer 8 to uniformly distribute the slurry 7. By stirring and immersing the porous support 2 in this for a sufficiently long time, a layer of unfired perovskite-type composite oxide is formed on the surface of the porous support 2, and this layer is maintained under conditions that do not cause cracks. After sufficiently drying, the film is formed by firing.

Here, as mentioned above, the porous electrodes 3 and 5
must be permeable to oxygen gas molecules, and for this purpose, the average pore diameter of the porous electrodes 3 and 5 after firing must be 0.
The average pore diameter is preferably 1 μm or more, and since mechanical strength decreases if the average pore diameter is made too large, it is preferably 10 μm or less. Also, the porosity is preferably 10 to 50 vol% for the same reason.

[0012] In order to obtain the above average pore diameter and porosity, the particle size distribution of the perovskite type composite oxide must be adjusted to 0.5μ.
m or more and 20 μm or less (preferably 1.0 to 10 μm), and the firing temperature is 1100° C. or more and 1500° C. or less (preferably about 1300° C.).

[0013] Here, as the perovskite type composite oxide, for example, one shown in the following (Chemical formula 1) is used.

0
014]

[Chemical formula 1]

On the other hand, the solid electrolyte layer 4 is formed by thermal spraying, vapor deposition, or the like, and its constituent material is calcia-stabilized zirconia, yttria-stabilized zirconia, or a mixture thereof.

In the examples, the solid electrolyte layer was formed by thermal spraying or CVD.
It may also be formed by a dipping method. However, since the solid electrolyte layer must not allow gases in the molecular state to pass through, but only allow oxygen ions and hydrogen ions to pass through, the average particle size of the stabilized zirconia that makes up the solid electrolyte should be made small, and dipping Do this multiple times.

[0017]

As explained above, according to the present invention, by controlling the particle size and firing temperature of the perovskite-type composite oxide applied to the surface of the substrate by the dipping method, the average pore size can be reduced to 0.1 to 10 μm. and the porosity is 10~50v
ol% porous electrodes can be formed. As a result, as shown in Figures 4 and 5, sufficient gas permeability (conventional 2
Furthermore, since the particles constituting the porous electrode are sufficiently bonded to each other, it also exhibits excellent electrical conductivity (twice as much as the conventional one).

[Brief explanation of the drawing]

[Fig. 1] A perspective view of an oxygen separation element with a porous electrode formed by the method of the present invention.

[Figure 2] Diagram showing the particle structure of the same porous electrode

[Figure 3] Schematic diagram of dipping device

[Figure 4] Graph comparing the N2 gas permeability coefficient between the present invention and a conventional electrode

[Figure 5] Graph comparing electrical conductivity between the present invention and conventional electrodes

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Oxygen separation element, 2... Porous support, 3, 5... Porous electrode, 4... Solid electrolyte layer, 6... Pore, 7... Container, 8... Slurry, 9... Stirrer, 10... Stirrer.

Claims (2)

[Claims] Claim 1: Perovskite type composite oxide powder, which has been classified to have a particle size within a predetermined range, is kneaded with a binder in a solvent to prepare a slurry, a porous or dense base material is immersed in this slurry, and then a porous or dense base material is immersed in the slurry. A method for producing a ceramic porous electrode, characterized in that the base material is pulled up, dried, and then fired. 2. The ceramic porous electrode according to claim 1, wherein the perovskite composite oxide powder has a particle size of 0.5 μm or more and 20 μm or less, and a firing temperature of 1100° C. or more and 1500° C. or less. manufacturing method.