JPS6366859A - Manufacture of perovskite type composite oxide thin film electrode or thin film electrode catalyst - Google Patents

Abstract

PURPOSE:To make it possible to manufacture an electrode having wide area and high efficiency by forming the thin film of an organic metal compound on the surface of an electrolyte film or a current collector from the solution containing a specific metal organic salt or metal alkoxide, then baking. CONSTITUTION:Metal organic salt or metal alkoxide containing metal ion which forms conductive perovskite type composite oxide is mixed. A mixed solution diluted with organic solvent if necessary, or the solution prepared by adding a metal or an inorganic compound which increases the activity and selectivity of a catalyst in the mixed solution is dropped on or applied to an electrolyte film or a current collector, or the electrolyte film or the current collector is immersed in the solution, then the solution is dried to form the metal organic compound on the surface of the electrolyte film or the current collector, and they are baked. Thereby, the perovskite type composite oxide is formed on the complicated surface or the micropores, and the efficiency of the electrode is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The unexploded EA relates to a method VC for producing a perovskite-type composite oxide thin film electrode or an N-film electrostatic catalyst.

[Conventional technology and problems]

Perovskite-type composite oxides with good conductivity not only have high electronic conductivity, but also have high oxidation activity as a catalyst.
It has excellent properties as an L electrode or VL electrode catalyst. Furthermore, since it has excellent heat resistance and exhibits ion conductive gold at high temperatures, it is attracting wide attention as a FL electrode catalyst for high-temperature fuel cells, a gas permeation electrode, and an electrode catalyst. When used as an electrode for these purposes, it is actually desirable to be able to form a thin film, and as an electrode catalyst, it is necessary to thinly cover the surface of a current collector electrode having a complicated shape of gold.

The vapor phase method and the table cast powder sintering method have been widely used as the platform method for producing oxide thin films, but the vapor phase method requires large-scale equipment and is difficult to manufacture for large areas. Moreover, the tape cast powder sintering method has a thinness limit (20 to 3 O/j), it is difficult to synthesize a uniform thin film, and the sintering temperature is high. is necessary.

[Structure of the invention]

The present invention provides 1 g of a mixed bath prepared by mixing a plurality of metal organic acid salts or metal alkoxides containing metal ions to form an electrically conductive perovskite-type composite oxide and diluting the mixture with an appropriate organic solvent as necessary, or A mixed solution in which a metal or an inorganic compound thereof that works to enhance the sensitivity and selectivity of the catalyst is added to this solution at an appropriate time is dropped or applied onto the electrolyte membrane or current collector, or the electrolyte membrane or the electrolyte is added to the solution. Immerse the entire current collector, pull it out, and dry it to find a thin film of organometallic compound! This is a method for producing a perovskite U composite oxide thin film electrode or thin film electrode catalyst by forming a film on the surface of an L solute membrane or a current collector and firing it.

The coating pyrolysis method of organometallic compounds of the present invention does not have the above-mentioned drawbacks and can easily synthesize thin films of 1μ or less at a low temperature of f000℃ or less, and is superior to the above two conventional methods. It should be replaced.

Until now, methods for synthesizing thin films using organometallic compounds have been reported for the purpose of solid electrolyte thin films and gas sensors. This is the first time that its effectiveness as a thin film electrode catalyst has been confirmed, and this is the result of many years of effort by the inventors. This method enables the formation of perovskite-type composite oxides even on surfaces with complex shapes and in the pores of porous materials, and is expected to improve electrode efficiency.

Furthermore, according to the present invention, the FF1J composite oxide thin film electrode and electrocatalyst have separate catalytic functions. It is also possible to add noble metals or other oxide catalysts with good uniformity and dispersibility, and binary or ternary functional thin film electrodes and thin film electrode catalysts can be synthesized.

By firing the metal organic acid salt and metal alkoxide, the organic components are decomposed, oxidized, and removed, and a uniform oxide thin film is produced. Decomposition and combustion of organic matter at 200-500℃
After that, the formation of dispersion and crystallization occur, so a low firing temperature of 400 to 800°C is sufficient. Further, the thickness of the thin film can be adjusted from several tens of angstroms to tens of thousands of angstroms by using a thin film diluted with an organic solvent.

Although the substrate 1 is covered with a decomposition membrane or a current collector, it is also possible to disintegrate it even if it is a planar spherical surface, a dense material, a porous material, or a fibrous material.

The basic composition of electrically conductive perovskite-type composite oxide is ABO3, but in order to enhance the properties, AOtll, B
Although it is common practice to partially replace elements of type i on both sides, adjusting the content of these elements is extremely difficult with vapor phase methods and powder sintering methods, whereas this method So,
It is a great advantage that this can be achieved simply by preparing a mixed solution in which the organic compound of the element to be added is added in an amount matching the composition. Furthermore, even when adding prize money and the like, a uniformly dispersed catalyst can be easily supported.

By the method of the present invention, almost all perovskite-type composite oxides can be synthesized, but for example, La1-z
srzcOOl, LaCrO3, Lal-1srz
) zin03.

LaNiO3, La1-zcazcol-yFey03
, CaVO3, 5rFe03.

CaRu03, BaPb1. zBiz03, 5r
Ce03, LaCuO3.

Examples of the metal organic acid salts include metal salts with naphthenic acid, octylic acid, caprylic acid, etc., and metal alkoxides include ethoxide, propioxide, butoxide, and the like.

Generally, it is not enough for electrodes used in batteries to exhibit high electronic conductivity; they are also required to have high activity for electrochemical reactions at high potentials.

Perovskite-type composite oxides are known to have high activity for oxygen reduction reactions at the cathode, but their electronic conductivity is not sufficiently high near room temperature, so they are mixed with graphite particles, etc. Widely used as poles.

However, if the surface of a current collector such as carbon fiber or carbon plate can be coated thinly, the internal resistance due to insufficient electron conductivity will be negligible. Therefore, by synthesizing a thin film according to the method of the present invention, it becomes possible to manufacture highly efficient electrodes having a wide electrode area.

Further, at high temperatures, some perovskite-type composite oxides exhibit mixed conductivity of electrons and ions. When using fc electrodes with only normal electron conductivity, the exchange of electrons is as follows:
The reaction occurs only at the point where the electrolyte, electrode, and gas coexist, and the effective electrode area is extremely small. However, in this mixed conductor, the reaction proceeds at the contact point between the gas and the electrode, or the gas and the electrolyte. Therefore, the effective I'It pole area increases significantly. Here, too, thinning the film is an important technical issue in order to increase the transmission rate of ions and electrons, and the method of the present invention can be effectively used as an electrode manufacturing technology for high-temperature fuel cells. There is no need to worry about deterioration of electrode properties due to volatilization or sintering, which is a problem when used at high temperatures such as
Excellent properties last.

Furthermore, this perovskite-type composite oxide catalyst can be easily and uniformly and dispersedly supported with catalysts such as noble metals having other catalytic functions, and is expected to be used as a multifunctional electrode catalyst.

Example 1 Nanthenates of lanthanum, strontium, iron, and cobalt were used as organometallic compounds, and La, Sr,
Co and Fe were mixed in a molar ratio of 5:1:5:1 and diluted with butanol to obtain a 2Dwt% butanol solution. This solution was mixed with At20. It was applied onto a substrate, dried, and then fired at 1000°C to create a thin film. As a result of Xa analysis, perovskite type La5rCoFe03-α
was confirmed to be generated. Approximately 10m above this thin film
A platinum paste was coated and baked at intervals of 2 to 30°C to form electrodes, and the surface conductivity of the thin film was measured from room temperature to 900°C. The conductive properties show a semiconducting behavior that increases as the temperature increases, and at 400°C to 900°C, 10''3 to 10-! It was confirmed that the conductivity was sufficiently high because it was Ω-.

Example 2 The mixed solution used in Example 1 was applied to both sides of a Y2O3-stabilized Zr01 dense sintered disk, dried, and fired to form La5rC.
After the oFe03-α electrodes were attached, they were fixed with platinum paste, and the platinum lead wires were taken out from both end faces of the disk. This ZrO2 disk was used as a partition wall, an airtight chamber was provided on both sides, argon was placed on one side, and air was placed on the other side. When a DC power source (■) was applied to the argon side and (■) was applied to the air side at 700°C, the oxygen concentration on the argon gas side was determined. In addition, it was confirmed that the voltage-current characteristics at this time were the same potential as those of the platinum electrode, and a high current density was obtained.

Claims (1)

[Claims] 1. Mix a plurality of metal organic acid salts or metal alkoxides containing metal ions to form an electrically conductive perovskite-type composite oxide, dilute with an appropriate organic solvent as necessary, and prepare the mixed solution. A thin film of the organometallic compound is deposited on the surface of the electrolyte membrane or the current collector by dropping or coating it, or by immersing the electrolyte membrane or the current collector in the solution, pulling it up, and drying it. A method for producing a perovskite-type composite oxide thin film electrode or thin film electrode catalyst, which is produced on the surface of an electric body and heated and fired. 2. The perovskite-type composite oxide thin film electrode catalyst according to claim 1, which uses a mixed solution in which a metal or an inorganic compound thereof is dispersed or dissolved and further functions to enhance the sensitivity and/or selectivity of the catalyst. Manufacturing method.