JPH0790665A - Oxygen generation electrode - Google Patents

Abstract

(57) [Summary] [Objective] To provide an electrode for oxygen generation, which has excellent durability and a long service life. This oxygen generating electrode has a base material 1 having at least a surface made of a simple metal or an alloy, and at least two layers of oxides formed on the surface of the base material 1 and made of oxides of elements other than platinum group elements. Coating layers 2 and 3 and oxide coating layers 2 and 3
And a catalyst layer 4 formed of an oxide containing a platinum group element oxide as a main component. The base material 1 is titanium, and the oxide film layer is electrolytically oxidized on the surface of the base material 1. Pyrolysis on the first underlayer 2 and the first underlayer 2 including the single layer 2a of titanium oxide formed by the above process and the single layer 2b of titanium oxide formed by the pyrolysis method formed thereon. And a single layer of tantalum oxide (second underlayer) 3 formed by
It is preferable that the catalyst layer 4 is composed of a mixed oxide of iridium oxide and tantalum oxide formed by a thermal decomposition method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen generating electrode used in the electrochemical industry, and more specifically, when used as an anode in the electrolytic industry such as electroplating, electrorefining, organic electrolytic synthesis, and cathodic protection. In addition, the present invention relates to an insoluble oxygen generating electrode that exhibits excellent durability.

[0002]

In the electrolysis industry, for example, zinc,
When copper, chromium, etc. are plated, for example, iron, copper, titanium, stainless steel, etc. are added to a plating bath containing zinc sulfate, copper sulfate, chromium sulfate, etc. as a main component, or a plating bath formed by adding sulfuric acid thereto. The electrolytic reaction proceeds in a state in which a substrate made of, for example, is immersed as a cathode, and an electrode for oxygen generation by energization is immersed as an anode.

As an oxygen generating electrode at this time, a lead electrode has been widely used. Not only can this lead electrode be manufactured at a low cost, but even if lead is dissolved in the plating bath, the solubility of lead in sulfuric acid is small and the lead concentration in the plating bath can be maintained at a low level.
It has the advantage that the plated surface of the base material is less susceptible to lead ions.

However, when this lead electrode is used as an oxygen generating electrode, the overvoltage during oxygen generation becomes high, and the distance between the two electrodes increases due to the dissolution of lead as the electrolysis progresses. There is a problem that the overall electrolysis voltage rises. That is, it becomes difficult to reduce the power consumption used during energization, and moreover, the frequency of electrode replacement increases with the adjustment of the inter-electrode distance and the thinning of the electrodes.

Instead of the lead electrode having such a defect,
An insoluble electrode whose surface is coated with a noble metal simple substance or a noble metal oxide may be used as an electrode for oxygen generation. This insoluble electrode is usually formed on the surface of a base material made of a valve metal such as titanium or an alloy containing these valve metals as a main component, such as iridium oxide or a mixture of iridium oxide and tantalum oxide. It has a structure in which it is covered with a catalyst layer composed of an oxide containing a noble metal oxide as its main component, and the electrode hardly wears when energized, and the oxygen overvoltage is significantly lower than that of a lead electrode. .

For example, in the production of an electrolytic copper foil, when a base material is made of titanium or a titanium alloy containing it as a main component and an insoluble electrode whose catalyst layer is made of iridium oxide is used as an anode, a conventional lead electrode is used. Compared to when used
It is possible to operate by lowering the cell voltage by about 1 V, and it is possible to significantly reduce the power consumption for energization. Moreover, since the electrodes are hardly consumed during the electrolytic operation, the distance between the electrodes does not change. Therefore, this electrode has the advantage of stabilizing the operating conditions and the product quality.

However, although the oxygen generating electrode having the catalyst layer containing iridium oxide as a main component has the excellent characteristics as described above, on the other hand,
As the electrolysis operation progresses, the electrolysis voltage may suddenly increase after a certain period of time. Especially, when the electrolytic operation is performed at a high current density, the above phenomenon occurs remarkably. Then, it is generally determined that the service life of the oxygen generating electrode is exhausted when such a phenomenon occurs.

The above-mentioned phenomenon is caused by the fact that an oxidizing substance generated on the electrode surface (catalyst layer surface) or a sulfuric acid component in the plating bath in the course of the electrolytic operation penetrates from the catalyst layer to the surface of the substrate located therebelow. By eroding the base material surface,
The adhesion between the base material and the catalyst layer is reduced, and an electrically insulating oxide film is formed on the surface of the base material, which causes a reduction in the conductivity of the entire oxygen generating electrode, and finally It is considered that this is because the electrolysis voltage increases.

Therefore, even if the insoluble oxygen generating electrode, which had excellent characteristics in the initial stage of use, had the above-mentioned phenomenon depending on the electrolysis conditions to be applied, the life of the electrode was shortened. May be shorter. In order to suppress the occurrence of such a phenomenon, attempts have been made to interpose a base layer having excellent durability between the base material and the catalyst layer.

For example, in Japanese Patent Publication No. 49-48072, a base material is subjected to an electrical or chemical oxidation treatment in an aqueous solution in which a valve metal such as Ti, Ta, Nb or Zr is dissolved. Thus, the oxide of the above metal is deposited on the surface of the base material, the thin oxide layer is formed as an underlayer, and then a catalyst layer made of a platinum group element or its oxide is formed on the underlayer. A method of forming is proposed.

According to this method, it is possible to form a relatively thick oxide layer as the underlayer. However, the adhesion between the underlayer formed by such electrodeposition and the substrate is not sufficiently good, and the adhesion at the interface between the underlayer and the catalyst layer is not so good. Therefore, when used as an electrode for oxygen generation, the interfacial peeling between the base material and the base layer or between the base layer and the catalyst layer gradually progresses due to the action of the oxidizing substance generated on the electrode surface, eventually, It cannot function as an electrode having excellent durability.

Further, in JP-A-57-116786, the base material is dipped in an aqueous solution in which Ti, Ta, Zr, Hf and Nb are dissolved, and the same method as in JP-B-49-48072 is carried out. There is disclosed a method in which an oxide layer of the above metal is formed on the surface of a base material by electrodeposition and then a part of the oxide layer is heat-treated in a non-oxidizing atmosphere.

Also in this method, a relatively thick underlayer can be formed between the substrate surface and the catalyst layer. However, the underlying layer formed by this method is
As in the case of the base layer of 8072, the adhesion to the substrate is poor. Further, in JP-B-60-21232, T is formed on the surface of a base material made of Ti or a Ti alloy.
By thermally decomposing a compound of a or / and Nb, a method of forming a mixed oxide of a Ti oxide existing as a thin film on the surface of a base material and an oxide of Ta or / and Nb as an underlayer is known. Proposed.

However, the above-mentioned underlayer made of a mixed oxide has poor adhesion to the substrate and poor corrosion resistance. Therefore, after all, it cannot function as a long-life electrode. Further, in Japanese Patent Publication No. 60-22074, an oxide of Ti and / or Sn having a valence of 4 and an oxide of Ta and / or Nb having a valence of 5 are formed on the surface of a base material. An electrode has been proposed in which a thin layer of the mixed oxide is formed as a base layer by a thermal decomposition method.

However, in the case of this electrode, although the formed underlayer has a certain degree of conductivity, it cannot be said that this mixed oxide itself has sufficient corrosion resistance in an acidic solution such as sulfuric acid. It cannot be said that this underlayer also exerts a sufficient effect. Further, in Japanese Patent Publication No. 3-27635 and Japanese Patent Application Laid-Open No. 2-61083, Ta, Ti, N are provided between the base material and the catalyst layer.
An electrode has been proposed in which a mixed oxide of at least one oxide selected from the group consisting of b, Sn, and Zr and an iridium oxide is interposed as an underlayer.

All of the underlayers disclosed herein have good conductivity, but since this underlayer is also made of a mixed oxide, the adhesion to the substrate is the same as in the case of the electrode described above. It is also poor in corrosion resistance. Therefore, this electrode cannot be expected to have a long life. Thus, an electrode with an underlayer interposed between the substrate and the catalyst layer has a longer service life than an electrode without an underlayer, but the adhesion between the substrate and the underlayer is insufficient. In addition, since the acid resistance is insufficient, it is hard to say that the oxygen generation electrode is not necessarily an electrode having a satisfactory long life.

[0017]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in various oxygen generating electrodes in which a conductive underlayer is interposed between a base material and a catalyst layer and solves the above problems. The adhesion between the formation layer and the catalyst layer is good, the corrosion resistance of the underlayer is also good, and even under electrolytic operation of high current density, oxygen that can be used for continuous operation for a long time at low oxygen overvoltage The purpose is to provide a generating electrode.

[0018]

In order to achieve the above-mentioned object, in the present invention, a base material having at least a surface made of a simple metal or an alloy, and a base material formed on the surface of the base material, other than a platinum group element, It has at least two oxide coating layers made of oxides of elements, and a catalyst layer formed on the surface of the oxide coating layers and made of oxides containing platinum group element oxides as main components. An electrode for oxygen generation is provided.

As the base material in the electrode of the present invention, at least the surface thereof is composed of a simple metal or an alloy. That is, as the base material, a material formed entirely of a simple metal or an alloy, or a material such as stainless steel is used as a core material, and the surface of the core material is
For example, those coated with a simple metal or an alloy by a film forming method such as lamination, PVD method, CVD method, etc. are used.

The elemental metal or alloy forming at least the surface of the base material is preferably an elemental metal of Ti or Zr or an alloy containing them as a main component. Especially, as a simple metal, it is easy to obtain T
i is preferred. In the case of Ti, JIS H460
Both the first type Ti and the second type Ti defined as 0 can be used.

As an alloy containing Ti as a main component, for example, Ti: 90% by weight, Al: 6% by weight, V: 4
Alloy of composition consisting of wt%, Ti: 77 wt%, Mo:
An alloy having a composition of 15% by weight, Zr: 5% by weight and Al: 3% by weight can be used. The shape of the base material is not particularly limited, and may be formed in an appropriate shape according to the use as an electrode, for example, a plate shape, a rod shape, a lath shape or the like. Usually, it is used in the form of a plate.

On the surface of such a base material, that is, on the surface of the above simple metal or alloy, an oxide coating layer described later is formed as a base layer. Prior to the formation of the oxide coating layer, it is necessary to remove the oxide coating formed on the surface of the base material during the production of the base material or while the base material is left in the atmosphere. . This is because if the oxide film layer is formed on the oxide film without removing the oxide film, the adhesion between the oxide film layer and the surface of the base material is hindered.

The clean surface of the base material from which the above oxide film has been removed has a surface roughness Rz defined by JIS B0601.
When the surface is roughened to 5 to 100 μm, preferably 10 to 40 μm, the adhesion strength between the substrate surface and the oxide coating layer,
Alternatively, it is preferable because the adhesion strength between the oxide coating layer and the catalyst layer described later formed thereon can be increased.

In this case, the method for removing the oxide film on the surface of the base material and roughening the surface of the cleaned base material is, for example, a concentration of 5 to 40% by weight and a liquid temperature of 50 to 100 ° C., preferably Is a method of immersing the base material in an oxalic acid aqueous solution at 90 to 100 ° C. for about 1 to 8 hours, or a base material is immersed in a sulfuric acid aqueous solution having a concentration of 5 to 50%, and the base material is used as an anode, and a current density of 5 to 3
A method of etching at 0 A / dm ² for about 1 to 10 minutes or the like can be adopted.

The oxide coating layer formed on the surface of the substrate has at least a two-layer structure, and each layer constituting the layer structure is a mixture as disclosed in Japanese Patent Publication No. 60-22074. Rather than being an oxide layer, it is formed of a stack of single oxides of oxides of metals other than the platinum group, each with unique properties. In that case, as the oxide coating layer (hereinafter, referred to as the first underlayer) formed first on the surface of the base material, the following configurations can be given.

First, when the first underlayer is formed of an oxide of the same kind of metal as the elemental metal forming the surface of the base material or an oxide of an alloy forming the surface of the base material, an oxidation treatment is applied to the surface of the base material. A method of oxidizing the surface of the substrate by applying is preferable. The oxidation treatment method in that case is not particularly limited, and examples thereof include a method of electrolytically oxidizing the base material surface by immersing the base material in an electrolytic solution, and a method of heating the base material in an oxygen-containing atmosphere. be able to.

In this case, by any method,
Since a part of the surface of the base material is oxidized, naturally, the first underlayer having high adhesion strength with the surface of the base material can be formed. It is preferable because the strength is remarkably increased. Further, when the surface of the base material is oxidized by heating in an oxygen-containing atmosphere, for example, a method in which the base material is subjected to heat treatment in the air at 350 to 600 ° C. for about 5 to 120 minutes is suitable.

The first underlayer is formed by coating a solution of a compound of a metal other than platinum group in a predetermined solvent on the surface of the substrate, and then thermally decomposing the coating layer in an oxygen-containing atmosphere. As a result, a metal oxide layer can be formed. This method is applied even when the first underlayer is an oxide of the same metal or alloy as the simple metal or alloy forming the surface of the base material, or when it is an oxide of a different metal or alloy. can do.

Further, the first underlayer is formed by PVD method or CV method.
It can also be formed by a method such as the D method. Also in the case of this method, as in the case of the above-described thermal decomposition method, even when the first underlayer is an oxide of the same metal or alloy as the simple metal or alloy forming the substrate surface,
Alternatively, it can be applied even in the case of oxides of different metals or alloys.

The first underlayer may be a single layer of each oxide coating layer formed by the above method,
Further, it may be a plurality of layers obtained by combining the above methods. When forming the first underlayer as a plurality of layers, for example, the following method can be adopted.

That is, for example, as shown in FIG.
When a Ti material is used as the material, first, as described above, the oxide film on the surface of the base material 1 (Ti), that is, the titanium oxide film is removed and roughened, and then the surface is electrolytically oxidized to form a base material. An extremely thin layer of titanium oxide having excellent adhesion to the material 1 (hereinafter referred to as a single layer 2a of titanium oxide) is formed, and a solution of a titanium compound is further applied onto the layer, which is then placed in an oxygen-containing atmosphere. Then, the titanium oxide layer (hereinafter referred to as titanium oxide single layer 2b) is pyrolyzed to form a titanium oxide single layer (first underlayer 2) composed of a plurality of layers.

The amount of the titanium oxide single layer formed by the electrolytic oxidation is 0.01 to 1.0 g / titanium equivalent per unit surface area (m ² ) of the substrate.
It is preferably m ² . If it is less than 0.01 g / m ² , sufficient corrosion resistance is not imparted to the manufactured electrode,
On the other hand, if it is more than 1.0 g / m ² , the conductivity will be lowered. A more preferable amount of formation is 0.05
Is 0.5 g / m ² .

The single layer 2a of titanium oxide is composed of sulfuric acid,
An aqueous solution of an inorganic acid such as nitric acid or phosphoric acid; an aqueous solution of an inorganic salt such as sodium sulfate or potassium sulfate; a substrate immersed in an aqueous solution of an inorganic alkali such as sodium hydroxide or potassium hydroxide. Use as an anode, for example, platinum as a cathode, and between both electrodes 0.2 with respect to the standard hydrogen electrode potential reference.
The electrolytic oxidation can be performed in the range of up to 100 V, but the electrolytic oxidation potential that improves the corrosion resistance varies depending on the structure of the underlayer. For example, in the case of a relatively thin underlayer having a total thickness of about 1 μm, the titanium oxide single layer 2a is preferably 3 mAh / under a potential of 0.5 to 15 V, more preferably 1.5 to 3 V. It is formed by electrolytic oxidation in which electricity of less than cm ² is applied.

The single layer 2a of titanium oxide formed by the above-mentioned electrolytic oxidation has excellent adhesion to the substrate 1, but its thickness is so thin that it is difficult to exhibit sufficient corrosion resistance by itself. Therefore, a thick titanium oxide single layer 2b is formed on the titanium oxide single layer 2a by a thermal decomposition method. The single layer 2b of titanium oxide is
First, for example, a solution obtained by dissolving a titanium compound in a predetermined solvent is applied onto the above-mentioned titanium oxide single layer 2a, and then the applied layer is subjected to 400 in an oxygen-containing atmosphere.
It is formed by thermal decomposition at a temperature of ˜650 ° C.

The composition of the titanium oxide single layer 2b formed by the above-mentioned thermal decomposition method is usually TiO 2 although it varies depending on the heating temperature and the oxygen concentration in the atmosphere.
It has a non-stoichiometric composition represented by _2-x (0 <x <0.5), and the layer has conductivity. Even if an oxidizing substance such as oxygen generated on the electrode surface enters from the electrode surface toward the base material, TiO _{2−x is} slightly oxidized (x slightly increases), so that the base material surface becomes electrically conductive. It is possible to prevent it from being covered with an insulating oxide film.

For example, titanium tetra-n-butoxide can be used as n
-Dissolved in butyl alcohol, the solution is directly applied to the surface of the titanium oxide single layer 2a by, for example, a brush or a spray, and then the applied layer is dried at a temperature of about 120 ° C, and then the whole is 400-650. The coating layer is composed of titanium oxide having a non-stoichiometric composition as described above by thermally decomposing the coating layer by heating in the atmosphere at 50 ° C., preferably 440 to 500 ° C. for 5 to 60 minutes, preferably 10 to 20 minutes. The single layer 2b of titanium oxide can be formed. Single layer 2b of titanium oxide formed under these conditions
Has a conductivity of 0.1 to 10 mS / cm and has sufficient conductivity as an electrode.

The application life of the electrode can be sufficiently extended even if the work of applying the titanium compound and the pyrolysis at the time of forming the single layer 2b of the titanium oxide is sufficiently extended. You may repeat. The thickness of the single layer 2b of titanium oxide is preferably 0.1 to 5 μm,
It is particularly preferably 0.5 to 2 μm. Thickness is 0.1
If the thickness is less than μm, the corrosion resistance of the electrode during actual use becomes insufficient, and if the thickness is more than 5 μm, sufficient conductivity cannot be obtained.

Since both of the titanium oxide single layer 2a and the titanium oxide single layer 2b thus obtained are made of titanium oxide, the mutual affinity is good and the two layers are The adhesion strength is high. The single layer 2a of titanium oxide formed by electrolytic oxidation is the base material 1
Since the surface itself is converted to an oxide, the adhesion strength with the substrate 1 is high. Therefore, the adhesion of the first underlayer 2 made of a single layer of titanium oxide to the substrate 1 is significantly improved as a whole.

Then, this titanium oxide single layer (first layer)
Since the underlayer 2) is composed only of titanium oxide, not of mixed oxide, its corrosion resistance is excellent. In the electrode of the present invention, the second oxide coating layer (hereinafter, referred to as the second underlayer 3) is formed on the titanium oxide single layer which is the first underlayer 2 described above, and the oxide coating as a whole is formed. The layers are constructed.

As the method for forming the second underlayer 3, PVD among the methods described for forming the first underlayer 2 is used.
Examples thereof include a film forming method such as a CVD method and a CVD method, and a method of thermally decomposing a coating layer of a solution of a metal compound in an oxygen-containing atmosphere. The oxide forming the second underlayer 3 may be any oxide that is an oxide of a metal other than the platinum group and has excellent durability, such as Ta oxide,
Examples thereof include Nb oxide, Ti oxide and Sn oxide. Among these, when the manufactured electrode is actually used, it is possible to effectively suppress the oxidation of the base material surface due to the oxygen generated on the electrode surface.
Is preferably composed of tantalum oxide alone.

Since the second underlayer 3 itself is dense and has high strength and good corrosion resistance, the electrolytic solution and the oxidizing substance may enter the surface of the base material when the electrode is actually used. Works to prevent In particular, when the second underlayer 3 is made of tantalum oxide, in addition to the above-mentioned function, it also functions to enhance both the adhesion to the first underlayer 2 and the adhesion to the catalyst layer 4 described later. So useful.

The thickness of the second underlayer 3 is 0.01-10.
It is preferably μm. This is because if the thickness is less than 0.01 μm, the above-mentioned effects are not sufficiently exhibited, and if it is more than 10 μm, the adhesion to the first underlayer 2 is deteriorated. More preferably, it is 0.02 to 1.0 μm. When forming the second underlayer 3 composed of a single layer of tantalum oxide, it is preferable to apply a thermal decomposition method using a tantalum compound.

That is, for example, a solution of tantalum chloride dissolved in n-butyl alcohol or a solution of tantalum penta-n-butoxide dissolved in n-butyl alcohol is applied on the first underlayer 2, The coating layer is dried at a temperature of about 120 ° C. Then, the whole 40
The coating layer is thermally decomposed by heating in the atmosphere at 0 to 650 ° C., preferably 440 to 550 ° C. for 5 to 60 minutes, preferably 10 to 20 minutes, and a tantalum oxide film is formed on the first underlayer 2. It is formed as the second base layer 3.

When the second underlayer 3 is formed by a thermal decomposition method, the service life of the electrode can be made sufficiently long even if the above-mentioned coating-pyrolysis operation is performed once. The above operation may be repeated once. In the electrode of the present invention, the surface of the oxide coating layer formed as described above, that is, the surface of the second underlayer 3 is covered with the catalyst layer 4.

The catalyst layer 4 is made of Ru, Rh, Pd, Os, I.
It is composed of an oxide whose main component is an oxide of a platinum group element such as r and Pt. The catalyst layer 4 is made of PV described above.
It can be formed by applying a film forming method such as the D method or the CVD method or the thermal decomposition method described above, and the latter method is particularly preferable.

These oxides may be used alone or as a mixed oxide of two or more kinds. Examples of oxides other than platinum group element oxides include Ta oxides, Nb oxides, Ti oxides, and Sn oxides. In particular, a mixed oxide whose main component is iridium oxide and the other oxide is tantalum oxide is suitable for the catalyst layer 4.

In this case, it is preferable that the iridium oxide is contained in an amount of 50 to 95 mol% in terms of chemical equivalent of iridium metal. If this content is less than 50 mol%, the catalytic activity of the catalyst layer will be reduced, and 95 mol%
This is because if it is above, it becomes difficult to form a dense catalyst layer. Particularly preferable content of iridium oxide is 55
Is about 65 mol%.

The thickness of the catalyst layer 4 is not particularly limited, but if it is too thin, the function as the catalyst layer 4 is not sufficiently exerted, and if it is too thick, the effect only reaches saturation.
This usually causes a rise in manufacturing cost, so it is usually 3 to 30μ.
It is set to about m. In the case of forming the catalyst layer 4 which is mainly composed of iridium oxide and is mixed with tantalum oxide,
For example, iridium chloride hexahydrate and tantalum penta-
n-Butoxide is dissolved in n-butyl alcohol at a desired ratio, the resulting solution is applied onto the oxide coating layer, and then the coating layer is dried at a temperature of about 120 ° C. Then, the whole is 400 to 650 ° C., preferably 440 to 55
The coating layer is thermally decomposed by heating in the atmosphere of 0 ° C. for 5 to 60 minutes, preferably 10 to 20 minutes. As a result, a mixed oxide layer formed by mixing iridium oxide and tantalum oxide in a desired ratio is formed on the oxide coating layer.

By repeating this coating-pyrolysis operation several times to several tens of times, the catalyst layer 4 having a desired thickness is formed on the oxide coating layer. The electrode of the present invention may be manufactured in various structures by the base material 1, the oxide coating layer (the first underlayer 2, the second underlayer 3), the constituent material of the catalyst layer 4, the layer forming method, and the like. it can.

Of these, the electrodes having excellent corrosion resistance and acid resistance during actual use of the electrodes are formed in a state in which the adhesion between the layers is good, and as a result, an electrode having an excellent service life can be realized. Those having such a structure can be mentioned as preferable ones. That is, first, a Ti material having a roughened surface is selected as the base material 1. The surface of the base material 1 is electrolytically oxidized to form a single layer 2a of titanium oxide. Then, a titanium oxide single layer 2b is formed on the titanium oxide single layer 2a by a thermal decomposition method, and both layers are combined to form a first underlayer 2. Then, a second layer of tantalum oxide alone is formed on the first underlayer 2 by a thermal decomposition method.
The base layer 3 is formed to form an oxide coating layer having a three-layer structure.

Finally, a mixed oxide of iridium oxide and tantalum oxide is formed on the oxide coating layer by a thermal decomposition method to form the catalyst layer 4.

[0052]

Next, the function of the electrode for oxygen generation of the present invention will be described.
i, a first underlayer 2 consisting of a titanium oxide single layer 2a formed by electrolytic oxidation of the surface thereof and a pyrolytic titanium oxide single layer 2b formed by laminating the titanium oxide single layer 2a A single layer of tantalum oxide (second underlayer) 3 formed on the underlayer 2 by a thermal decomposition method, and a catalyst comprising a mixed oxide of iridium oxide and tantalum oxide on the second underlayer 3. The electrode on which the layer 4 is formed will be described.

In the electrode having this structure, the oxide coating layer interposed between the surface of the substrate 1 and the catalyst layer 4 is composed of the first underlayer 2 and the second underlayer 3, and the first underlayer is 2 has a two-layer structure, and the oxide coating layer as a whole has a three-layer structure. Each of the layers forming the oxide coating layer is made of a single oxide, not a mixed oxide.

The mixed oxide generally has a problem that the characteristics of each oxide constituting the mixed oxide are not sufficiently exhibited. For example, in the case of a mixed oxide in which titanium oxide and tantalum oxide are mixed, the oxidation resistance to sulfuric acid and the oxidation resistance to generated oxygen have a greater degree of deterioration than those of individual oxides. In other words, titanium oxide and tantalum oxide are more effective in acid resistance and oxidation resistance when used alone than when they are used as a mixture.

In the case of the electrode of the present invention, since each of the layers constituting the oxide coating layer is made of a single titanium oxide or tantalum oxide, each layer has its own acid resistance and oxidation resistance. Independently and effectively exhibit sexual characteristics,
As a result, the acid resistance and oxidation resistance of the entire electrode are improved and the electrode life is extended. In the electrode having the above structure, the first
The single layer 2a of titanium oxide, which constitutes the lower layer of the base layer 2, is formed by electrolytically oxidizing the surface of the Ti base material 1.
It is a modified layer on the surface of the Ti base material, so to speak, and has excellent adhesion to the surface of the base material.

Since the single layer of titanium oxide 2b constituting the upper layer of the first underlayer 2 is the same type of titanium oxide as the single layer of titanium oxide formed by the above-mentioned electrolytic oxidation, they adhere firmly to each other. Can be integrated into one. Therefore,
In the formed first underlayer, the lower layer is firmly adhered to the surface of the Ti base material, and the upper layer is firmly adhered to the lower layer, so that the Ti base material is firmly adhered as a whole. It is in a state of Then, the first underlayer 2 is
Since it is composed entirely of titanium oxide, the characteristics as titanium oxide are effectively exhibited, and the acid resistance of the base material against sulfuric acid and the like is remarkably improved. In addition, its composition is usually a non-stoichiometric composition represented by TiO _2-x (0 <x <0.5), and the layer is not only conductive but also generated on the electrode surface. Even if oxidizable substances such as oxygen enter from the electrode surface toward the substrate,
_2-x slightly oxidizes (x slightly increases),
It is possible to prevent the surface of the base material from being covered with an electrically insulating oxide film.

The second underlayer 3 formed on the first underlayer 2 is a single layer of tantalum oxide formed by a thermal decomposition method. In the formation process, solid solutions of both oxides are produced as a by-product at the interface between the single layer of tantalum oxide and the single layer of titanium oxide of the first underlayer 2, so that the adhesion between the two layers is good. . Therefore, the second underlayer 3, which is a single layer of this tantalum oxide, also comes into close contact with the surface of the Ti base material via the above-mentioned first underlayer 2.

On the other hand, the single layer of tantalum oxide is far superior to the single layer of titanium oxide in the barrier effect against oxygen generated on the surface of the catalyst layer. Therefore, since the second underlayer 3 in the present invention is a single layer of tantalum oxide formed by a thermal decomposition method, the adhesion with the first underlayer 2 is good, and as a barrier against generated oxygen. It functions effectively and enhances the acid resistance and oxidation resistance of the entire substrate.

The catalyst layer 4 formed on the second underlayer 3 is a mixed oxide in which iridium oxide and tantalum oxide are mixed, and the tantalum oxide component of them is
Compared with the case where the catalyst layer 4 is composed of only iridium oxide, the catalyst layer 4 is made denser, and thus oxygen generated on the surface of the catalyst layer is prevented from entering the oxide coating layer side, and at the same time, the surface of the oxide coating layer is Is composed of tantalum oxide, the catalyst layer 4 is mediated by the tantalum oxide.
Also has a function of adhering to the oxide coating layer well.

As described above, in the oxygen generating electrode of the present invention, all the layers formed on the surface of the Ti base material are in close contact with each other, and the characteristics of each layer can be effectively exhibited. There is. Therefore, the peeling phenomenon of each layer does not easily occur during use, and the oxidation of the surface of the base material by the oxidizing component is effectively prevented, so that the service life of the electrode is extended.

In general, in the case of an electrode whose surface is coated with an oxide layer, its impedance is measured by the current intercaptor method, and its value is the electric double layer at the interface between the electrode and the electrolytic bath. It is possible to separately measure the reaction resistance of the charge transfer process in parallel and the resistance generated in the oxide layer on the substrate, but in the electrode of the structure of the present invention, the resistance of the electrode is expected to be 50 to ²⁰⁰ mΩcm ^2. It is low outside and can be fully used as an electrode.

[0062]

Examples of the invention

Examples 1 to 3 and Comparative Examples 1 to 3 A second type Ti plate having a length of 200 mm, a width of 20 mm and a thickness of 2 mm was degreased and washed with acetone and then dried. Next, this Ti
The plate was placed in an oxalic acid aqueous solution with a concentration of 10% by weight (liquid temperature 90 ° C).
After being immersed in the solution for 5 hours for roughening treatment, it was washed with water and dried to obtain a substrate.

This Ti substrate was used as an anode, a platinum plate was used as a cathode, and a sulfuric acid aqueous solution having a concentration of 10% by weight (solution temperature 30 ° C.) was used as an electrolytic solution. A DC voltage of 30 V was applied between both electrodes to obtain about 1%.
Electrolytic oxidation treatment for 5 minutes, converted to Ti 0.1g
/ M ² of the titanium oxide single layer 2a was formed. The surface of the obtained Ti base material was blue. Titanium tetra
A total of 100 ml of a solution was prepared by dissolving 34.0 g of n-butoxide in n-butyl alcohol.

This solution was brush-coated on the surface of the Ti base material after electrolytic oxidation treatment, the coating layer was dried at a temperature of 120 ° C. for 3 minutes, and further 10 minutes in air at a temperature of 450 ° C.
By heating for 1 minute, a single layer 2b of titanium oxide was formed. Then, 54.6 g of tantalum penta-n-butoxide was dissolved in n-butyl alcohol to prepare a total solution of 100 ml, and this solution was brushed on the surface of the single layer 2b of the titanium oxide. Apply the coating layer at a temperature of 120 ° C for 3
It was dried for 1 minute, and further heated in the air at a temperature of 450 ° C. for 10 minutes to form the second underlayer 3 composed of a single layer of tantalum oxide.

Next, iridium chloride hexahydrate 12.
2 g and 8.7 g of tantalum penta-n-butoxide were dissolved in n-butyl alcohol to prepare a total 100 ml solution for catalyst layer. This solution was brushed on the surface of the tantalum oxide layer (second underlayer 3) described above, and then the temperature was adjusted to 12
Dry at 0 ° C for 3 minutes, then in air at 450 ° C for 1
After heating for 0 minutes, each component of the solution is thermally decomposed to form a mixed oxide film (iridium oxide: 61% by weight in terms of iridium equivalent), and the solution is brushed-dried-heated again. The catalyst layer 4 was formed repeatedly. In addition,
The final heating time was 1 hour. In this way, the example electrode 1 was manufactured.

The applied voltage during the electrolytic oxidation treatment is 70V.
Then, the titanium oxide single layer 2a of 0.2 g / m ^{2 in} terms of Ti was formed, and the single layer of tantalum oxide was directly formed on the titanium oxide single layer 2a by electrolytic oxidation (second layer).
An electrode was produced in the same manner as in Example electrode 1 except that the underlayer 3) was formed, and this was designated as Example electrode 2.

An electrode was prepared in the same manner as in Example 1 except that the titanium oxide single layer 2b was formed directly on the surface of the Ti substrate 1 without electrolytic oxidation treatment. Was manufactured, and this was designated as Example Electrode 3. The catalyst layer 4 was directly formed on the surface of the Ti base material 1 used for manufacturing the example electrode 1 under the same conditions as in the case of the example electrode 1 to manufacture an electrode, which was designated as a comparative example electrode 1.

A single layer of tantalum oxide (second underlayer 3) was formed directly on the surface of the Ti base material 1 used in the manufacture of the electrode 1 of the example under the same conditions as in the case of the electrode 1 of the example. A catalyst layer 4 was formed thereon under the same conditions to manufacture an electrode, which was designated as Comparative Example Electrode 2. The same Ti as in the case of Example electrode 1
On the surface of the substrate 1, titanium tetra-n-butoxide 17.0
g and tantalum penta-n-butoxide 27.3 g were dissolved in n-butyl alcohol to make a total of 100 ml, and the solution was brush-coated, and the coating layer was dried at a temperature of 120 ° C. for 3 minutes, and then the temperature was increased. Except that heating was performed in the air at 450 ° C. for 10 minutes to form a layer of a mixed oxide of titanium oxide and tantalum oxide, and that the coating-pyrolysis operation was performed twice. Similarly to the case of manufacturing the electrode 1, the catalyst layer 4 was formed on the mixed oxide layer to manufacture an electrode, which was used as a comparative electrode 3.

Each of these electrodes had a concentration of 1 mol / mol.
l soak in a sulfuric acid aqueous solution (liquid temperature 100 ° C) to make an anode,
Applying a DC voltage between both electrodes with the platinum plate as the cathode, 100
A / dm ²It energized with the current density of. The anode is working properly
Terminal voltage is 3 to 5V. But the anode deteriorates
Then, the anode potential rises rapidly, and the terminal voltage
Also suddenly rises to over 10V.

The time from the start of energization to the terminal voltage exceeding 10 V was measured. The results are shown in Table 1. Example 4, Comparative Example 4 A Zr plate having a length of 200 mm, a width of 20 mm and a thickness of 2 mm was degreased and washed with acetone and then dried. Next, this Zr plate was immersed in an aqueous solution of oxalic acid having a concentration of 10% by weight (liquid temperature 90 ° C.) for 5 hours for roughening treatment, then washed with water and dried to obtain a substrate.

Titanium tetra-n-butoxide (34.0 g) was dissolved in n-butyl alcohol to prepare a total solution of 100 ml. This solution is brushed on the surface of a Zr substrate, the coating layer is dried at a temperature of 120 ° C. for 3 minutes, and further heated in the air at a temperature of 450 ° C. for 10 minutes to form a single layer of titanium oxide 2b. Was formed.

Then, 54.6 g of tantalum penta-n-butoxide was dissolved in n-butyl alcohol to obtain a total of 10
0 ml of a solution was prepared, and this solution was brush-coated on the surface of the titanium oxide single layer 2b, and then the coating layer was dried at a temperature of 120 ° C. for 3 minutes, and further at a temperature of 450 ° C.
Was heated in the atmosphere for 10 minutes to form a single layer of tantalum oxide (second base layer 3).

Next, iridium chloride hexahydrate 12.
2 g and 8.7 g of tantalum penta-n-butoxide were dissolved in n-butyl alcohol to prepare a total 100 ml solution for catalyst layer. This solution is brush-coated on the surface of the above-mentioned single layer of tantalum oxide (second underlayer 3), dried at a temperature of 120 ° C. for 3 minutes, and then heated in the air at 450 ° C. for 10 minutes. Each component of the solution was pyrolyzed to form a mixed oxide film, and the operation of brush coating-drying-heating the solution was repeated four times to form the catalyst layer 4.
The final heating time was 1 hour. Thus, Example electrode 4 was manufactured.

Example 4 was repeated except that the single layer of tantalum oxide (the second underlayer 3) was formed directly on the surface of the Zr substrate without forming the single layer of titanium oxide.
An electrode was manufactured in the same manner as above, and this was designated as Comparative Example Electrode 4. The deterioration time of these electrodes was measured in the same manner as in Examples 1 to 3. The results are summarized in Table 1
Shown in.

[0075]

[Table 1] Examples 5 to 16 A second type Ti plate having a length of 200 mm, a width of 20 mm and a thickness of 2 mm was degreased and washed with acetone and then dried. Next, this Ti
The plate was placed in an oxalic acid aqueous solution with a concentration of 10% by weight (liquid temperature 90 ° C).
After soaking for the time shown in Table 2 to roughen the surface,
It was washed with water and dried. A Ti plate having a surface roughness Rz specified in JIS B0601 shown in Table 2 was obtained. The Ti plates used in Examples 12 and 13 had an average particle size of 30.
It was subjected to physical surface roughening treatment by sandblasting using a 0 μm alumina abrasive.

Then, using these Ti plates as anodes and platinum plates as cathodes, an aqueous sulfuric acid solution having a concentration of 1 mol% (liquid temperature 30
(.Degree. C.) as an electrolytic solution and electrolytic oxidation was performed under the conditions shown in Table 2 to form a single layer 2a of titanium oxide having the indicated thickness. In addition, 34.0 g of titanium tetra-n-butoxide was added to n.
Dissolved in butyl alcohol to make a total of 100 ml solution.

This solution was brushed on the titanium oxide single layer 2a formed on the surface of the Ti plate.
The coating layer is dried at a temperature of 120 ° C. for 3 minutes and further heated in an atmosphere at a temperature of 450 ° C. for 10 minutes to have a thickness of about 1
A single layer 2b of titanium oxide with a thickness of μm was formed. Next, 1 g of tantalum penta-n-butoxide was dissolved in n-butyl alcohol to prepare a solution of 100 ml in total, and this solution was brush-coated on the single layer 2b of the titanium oxide and then its coating. The layer was dried at a temperature of 120 ° C. for 3 minutes and further heated in an atmosphere at a temperature of 450 ° C. for 10 minutes to form a second underlayer 3 composed of a single layer of tantalum oxide.

Further, 12.2 g of iridium chloride hexahydrate
And 8.7 g of tantalum penta-n-butoxide were dissolved in n-butyl alcohol to prepare a total 100 ml solution for the catalyst layer. This solution is brushed on the second underlayer 3 and then dried at a temperature of 120 ° C. for 3 minutes.
The mixture was heated in an atmosphere of 0 ° C. for 10 minutes to thermally decompose each component of the solution to form a mixed oxide film, and again the steps of brush coating-drying-pyrolysis of the solution were repeated 4 times to obtain a film having a thickness of A catalyst layer 4 having a thickness of about 4 μm was formed. The final heating time was 1 hour.

In Example 14, 2.1 g of iridium chloride hexahydrate and 18.2 g of tantalum penta-n-butoxide were dissolved in n-butyl alcohol to give a total solution of 100 ml. For Example 15, 6.5 g of iridium chloride hexahydrate and tantalum penta-n-
A solution obtained by dissolving 14.1 g of butoxide in n-butyl alcohol to make a total solution of 100 ml. For Example 16, 21.0 g of iridium chloride hexahydrate and 0.4 g of tantalum penta-n-butoxide. Was dissolved in n-butyl alcohol to obtain a total solution of 100 ml, and a catalyst layer 4 was formed.

The mixing ratio of Ir oxide in these catalyst layers 4 was as shown in Table 2 in terms of Ir metal equivalent chemical equivalent. Each of these electrodes was immersed in a sulfuric acid aqueous solution (solution temperature 100 ° C.) having a concentration of 1 mol / l to serve as an anode, and a platinum plate was used as a cathode to apply a DC voltage between the electrodes to 100 A /
Current was applied at a current density of dm ² .

When the anode is operating normally, the terminal voltage is 3-5V. However, when the anode deteriorates, the anode potential rises sharply and the terminal voltage rises sharply with it.
It becomes V or more. The time from the start of energization to the terminal voltage exceeding 10 V was measured. The results are collectively shown in Table 2.

[0082]

[Table 2]

As is clear from Table 2, Example 11
The electrodes of Nos. 13 to 13 have the same layer structure as the electrodes of Example 5 except that the surface roughness of the substrate surface is different, but the time until the terminal voltage of these electrodes exceeds 10V. That is, comparing the lifetimes, the lifetimes of the electrodes of Examples 11 to 13 are about 1/4 to 1/3 of the lifetimes of the electrodes of Example 5, which are very short. Moreover, the electrodes of Examples 14 to 16 were
Except that the ratio of Ir oxide in the catalyst layer is different, it has the same layer structure as the electrode of Example 5, but these electrodes are also compared with each other in life. Is about 1/5 to 2/5 that of the electrode of Example 5.
And it is very short.

Thus, the layer structure of the electrodes is the same,
Further, it can be seen that even if the conditions of electrolytic oxidation are the same, if the roughened state of the substrate surface or the composition of the catalyst layer changes, the life of the electrode also changes significantly. Therefore, in the oxygen generating electrode of the present invention, it is preferable to set the conditions for forming the base material and the catalyst layer to the conditions shown in claims 3 and 9 in order to further prolong the life thereof.

[0085]

The electrode for oxygen generation according to claim 1 has at least a single oxide composed of an oxide of one kind of metal other than the platinum group element as an oxide coating layer between the base material and the catalyst layer. Two
Since the metal oxide has a structure in which the layers are interposed and the inherent characteristics such as acid resistance and oxidation resistance of each metal oxide are effectively exhibited, the service life of the electrode is extended.

In the oxygen generating electrode of claim 2, since at least one surface of the base material is made of at least one selected from the group consisting of Ti and Zr or an alloy containing them as a main component, the base material is easily available. Also, the corrosion resistance of the base material itself is improved. In the oxygen generating electrode according to claim 3, since the surface of the base material has a surface roughness Rz of 5 to 100 μm,
The adhesion strength between the base material and the oxide coating layer formed thereon is improved, and peeling between the base material and the oxide coating layer during actual use can be suppressed.

In the oxygen generating electrode according to claim 4, the oxide coating layer has a titanium oxide single layer having excellent conductivity on the lower side and a tantalum oxide single layer having high strength and good corrosion resistance on the upper side. Since it has a two-layer structure formed, it is possible to effectively suppress the oxidation of the surface of the base material due to the oxygen generated on the electrode surface while ensuring the conductivity as the electrode when the electrode is actually used. Therefore, the service life of this electrode is further extended.

In the oxygen generating electrode according to claim 5, the base material is made of titanium or an alloy containing titanium as a main component, and the single layer of the titanium oxide is a titanium oxide formed by oxidizing the surface of the base material. At least one titanium oxide selected from the group consisting of a single layer of titanium oxide, a single layer of titanium oxide formed by physical vapor deposition, and a single layer of titanium oxide formed by thermally decomposing a coating layer of a titanium compound. It is a single layer. That is, since this titanium oxide layer is composed of only titanium oxide, not a mixed oxide, it exhibits excellent corrosion resistance. Therefore, the service life of this electrode is extended.

In the oxygen-generating electrode according to the sixth aspect of the present invention, at least the surface of the base material made of titanium or an alloy containing it as a main component is electrolytically oxidized to form a single layer of titanium oxide. The single layer of oxide is an oxide that includes a so-called epitaxial structure, which is converted into an oxide while the titanium structure on the surface of the base material is maintained as it is, and the adhesion strength with the base material is extremely high. It's getting higher. Therefore, the durability of this electrode is further improved.

In the oxygen generating electrode according to claim 7, the titanium oxide single layer is a titanium oxide single layer formed by electrolytically oxidizing the surface of the base material, and a titanium compound thermal layer formed on the single layer. It consists of a single layer of titanium oxide produced by the decomposition method. Both layers of the titanium oxide single layer thus obtained are made of titanium oxide, so that the mutual affinity is good and the adhesion strength between both layers is high. And, the single layer of titanium oxide formed by electrolytic oxidation, since the surface itself of the substrate is converted to oxide,
High adhesion strength with the base material. Therefore, the adhesion of the single layer of titanium oxide to the substrate is significantly improved as a whole.
Therefore, the durability of this electrode is improved.

In the oxygen-generating electrode of claim 8, electrolytic oxidation is used.
The amount of titanium oxide single layer formed by
Tan-metal equivalent 0.01-1.0 g / unit area of base material
(M ²), This titanium oxide layer is excellent.
Shows corrosion resistance and conductivity. Therefore, this electrode is useful
It has a long life and shows sufficient conductivity as an electrode.
You

In the oxygen generating electrode according to claim 9, since the catalyst layer is made of a mixture of iridium oxide and tantalum oxide, a dense layer excellent in catalytic activity can be obtained. for that reason,
The electrode has a good oxygen generating capability, and at the same time, the oxygen generated on the surface of the catalyst layer is suppressed from entering the underlayer side. As is clear from the above description, the electrode of the present invention has excellent durability and long service life, and is useful as an insoluble oxygen generating electrode in the electrolytic industry.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of an oxygen generating electrode of the present invention.

[Explanation of symbols]

 1 Base Material 2 First Underlayer (Oxide Coating Layer) 2a Titanium Oxide Single Layer (by Electrolytic Oxidation) 2b Titanium Oxide Single Layer (by Pyrolysis Method) 3 Second Underlayer (Oxide Coating Layer) 4 Catalyst layer

[Procedure amendment]

[Submission date] August 11, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

The thickness of the catalyst layer 4 is not particularly limited, but if it is too thin, the function as the catalyst layer 4 is not sufficiently exerted, and if it is too thick, the effect only reaches saturation.
This usually causes a rise in manufacturing cost, so it is usually 3 to 30μ.
It is set to about m. In the case of forming the catalyst layer 4 which is mainly composed of iridium oxide and is mixed with tantalum oxide,
For example, iridium chloride hexahydrate and tantalum penta-n-butoxide are dissolved in n-butyl alcohol at a desired ratio, the resulting solution is applied on the oxide film layer, and then the temperature is about 120 ° C. To dry the coating layer. Then, the whole is 400 to 650 ° C., preferably 440 to 5
5 to 60 minutes in the atmosphere of 50 ° C., preferably 10 to 20
The coating layer is pyrolyzed by heating for a minute. As a result, a mixed oxide layer formed by mixing iridium oxide and tantalum oxide in a desired ratio is formed on the oxide coating layer.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction content]

Furthermore, iridium chloride hexahydrate 12.2
g and tantalum penta-n-butoxide (8.7 g) were dissolved in n-butyl alcohol to prepare a total 100 ml solution for the catalyst layer. After this solution is brush-coated on the second underlayer 3, it is dried at a temperature of 120 ° C. for 3 minutes, and further 4
The mixture was heated in the atmosphere at 50 ° C. for 10 minutes to thermally decompose each component of the solution to form a mixed oxide film, and the operation of brush coating-drying-pyrolysis of the solution was repeated 4 times to obtain a film having a thickness of A catalyst layer 4 having a thickness of about 4 μm was formed. The final heating time was 1 hour.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0079

[Correction method] Change

[Correction content]

For Example 14, iridium chloride was used.
Uranic acid hexahydrate ( 2.1 g) and tantalum penta-n-butoxide (18.2 g) were dissolved in n-butyl alcohol to give a total solution of 100 ml.
6.5 g of iridium chloride hexahydrate and tantalum penta
A solution obtained by dissolving 14.1 g of n-butoxide in n-butyl alcohol to make a total solution of 100 ml. For Example 16, 21.0 g of iridium chloride hexahydrate and tantalum penta-n-butoxide 0 The catalyst layer 4 was formed by using a solution obtained by dissolving 0.4 g and n-butyl alcohol into a total solution of 100 ml.

Claims (9)

[Claims] 1. A substrate having at least a surface made of a simple metal or an alloy, at least two oxide coating layers formed on the surface of the substrate and made of an oxide of an element other than a platinum group element, and the oxide. An electrode for oxygen generation, comprising: a catalyst layer formed on the surface of a material coating layer and made of an oxide containing a platinum group element oxide as a main component. 2. The oxygen generating electrode according to claim 1, wherein the surface of the base material is made of at least one selected from the group consisting of Ti and Zr or an alloy containing them as a main component. 3. The electrode for oxygen generation according to claim 1, wherein the surface of the base material is a rough surface having a surface roughness Rz defined by JISB0601 of 5 to 100 μm. 4. The oxygen generating electrode according to claim 1, wherein the oxide coating layer has a single layer of titanium oxide as a lower layer and a single layer of tantalum oxide as an upper layer. 5. A titanium oxide single layer formed by oxidizing the surface of the base material, wherein at least the surface of the base material is made of Ti or an alloy containing Ti as a main component, and the single layer of titanium oxide is a physical layer. A single layer of at least one titanium oxide selected from the group consisting of a single layer of titanium oxide formed by a vapor deposition method and a single layer of titanium oxide formed by thermally decomposing a coating layer of a titanium compound. 4. Oxygen generation electrode. 6. The oxygen generating electrode according to claim 5, wherein the single layer of titanium oxide formed by oxidizing the surface of the base material is formed by electrolytic oxidation of the surface of the base material. 7. A single layer of titanium oxide formed by oxidizing the surface of the base material, a titanium oxide layer formed by electrolytically oxidizing the surface of the base material, and a thermal decomposition method of a titanium compound thereon. The electrode for oxygen generation according to claim 5, which comprises a titanium oxide layer formed by. 8. The amount of titanium oxide layer formed by electrolytic oxidation is 0.01 to 1.0 g in terms of titanium metal equivalent.
/ Unit surface area of the substrate (m ²⁾ at a claim 6 or 7 oxygen generating electrode. 9. The catalyst layer comprises a mixture of iridium oxide and tantalum oxide, and the mixture has an iridium oxide chemical equivalent of 50 to 95 mol%.
The oxygen generating electrode according to claim 1, which contains.