JP2919169B2 - Electrode for oxygen generation and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel oxygen generating electrode and a method for producing the same. More specifically, the present invention provides an oxygen-generating electrode having excellent durability and a low oxygen overvoltage, which is preferably used for a reaction for generating oxygen at an anode by electrolyzing a desired aqueous solution. It relates to a method for manufacturing.

[0002]

2. Description of the Related Art Conventionally, metal electrodes having a conductive substrate made of titanium metal and provided thereon with a coating layer of a platinum group metal or an oxide thereof have been used in various fields of the electrolytic industry.
For example, an electrode in which a ruthenium and titanium oxide or a ruthenium and tin oxide is coated on a titanium substrate is known as an anode for generating oxygen by salt electrolysis (Japanese Patent Publication No. 46-21884, Japanese Patent Publication No. 48-3954,
JP-B-50-11330).

In the electrolysis industry, in addition to electrolysis involving chlorine generation as in the case of the above-described salt electrolysis,
Oxygen generation such as recovery of acids, alkalis or salts, collection of metals such as copper and zinc, plating, and cathodic protection may be involved.

In such electrolysis involving oxygen generation, an electrode commonly used for generating chlorine, such as the above-mentioned titanium substrate, is coated with a ruthenium-titanium oxide or a ruthenium-tin oxide. Using the electrode
Corrosion in a short period of time makes electrolysis impossible. For this reason, electrodes configured specifically for oxygen generation are used. As such an electrode, an iridium oxide-platinum-based electrode, an iridium oxide-tin oxide-based electrode, a platinum-plated titanium electrode and the like are known, and the most commonly used are a lead-based electrode and a soluble zinc-based electrode. The anode.

[0005] However, these known electrodes cause various troubles depending on the purpose of use, and are not necessarily suitable. For example, when a soluble zinc anode is used as an anode for galvanizing, the dissolution of the anode is remarkable, so the distance between the electrodes must be adjusted frequently, and when a lead-based insoluble anode is used, it is mixed into the electrolytic solution. Plating defects occur due to the influence of lead. In addition, when performing so-called high-speed zinc plating at a high current density of 100 A / dm ² or more, the platinum-plated titanium electrode is extremely consumed and cannot be used.

[0006] Therefore, development of an electrode which can be universally applied to a wide range of fields without any hindrance for electrolysis involving oxygen generation has become one of the important issues in electrode manufacturing technology.

On the other hand, when electrolysis involving the generation of oxygen is generally performed using a titanium substrate electrode having a coating layer as an anode, a titanium oxide layer is formed between the substrate and the coating layer, and the anode potential gradually increases. It is often observed that the layers detach and the anode is passivated. Therefore, in order to suppress the formation of titanium oxide formed in the middle, prevent passivation of the anode, and prevent an increase in electric resistance, various metal oxides are provided as an appropriate intermediate layer. (JP-B-60-21232, JP-B-60-22)
075, JP-A-57-116786 and JP-A-60-184690. )

However, since the intermediate layer provided in this manner is generally lower in conductivity than the coating layer, the expected effect cannot be obtained when performing electrolysis at a high current density. It is. Further, an intermediate layer in which platinum is dispersed in a base metal oxide is provided (Japanese Patent Application Laid-Open No. 60-1846).
No. 91) and the provision of an intermediate layer composed of a valve metal oxide and a noble metal (JP-A-57-73193) has been proposed, but platinum itself has low corrosion resistance.
When the effect as the intermediate layer is insufficient, and when the valve metal oxide is mixed, the type and the amount of the mixture are naturally limited, and it is difficult to achieve the desired effect.

In addition, there is also known an electrode in which lead dioxide is coated on a conductive metal substrate via an intermediate layer containing iridium oxide and tantalum oxide (JP-A-56-123).
388, JP-A-56-123389), this intermediate layer merely has the effect of improving the adhesion between the metal substrate and the lead dioxide coating and preventing corrosion caused by pinholes and the like. However, when this is used for electrolysis involving the generation of oxygen, the effect of suppressing the formation of titanium oxide is insufficient, and in addition, it is inevitable that lead is unavoidably mixed into the electrolytic solution.

Further, an electrode in which iridium oxide is applied to an upper layer using iridium oxide and tantalum oxide as an intermediate layer on a conductive metal substrate (JP-A-63-235493), and the amount of iridium oxide is set to Increased iridium oxide-tantalum oxide electrodes (JP-A-2-61083, JP-A-3-193889) have also been proposed. However, in this case, the iridium oxide in the upper layer has a higher oxygen overvoltage than the intermediate layer composed of iridium oxide and tantalum oxide, which causes power loss and is satisfactory in terms of the aging of the oxygen overvoltage after electrolysis and the electrode life. However, there is a disadvantage that the adhesion strength decreases after electrolysis.

As an electrode having a low oxygen overvoltage, an electrode containing iridium oxide, tantalum oxide and platinum is known (JP-A-1-301876). However, even in this case, since it is necessary to use iridium or platinum for the underlayer, the cost is unavoidable, and in terms of life and deterioration with time, the length is longer than that of the electrode containing iridium oxide and tantalum oxide. It is not possible. Further, the adhesion strength after electrolysis is insufficient.

Further, there is also known an electrode in which platinum and iridium oxide or a base metal oxide which are dispersedly coated are provided as an intermediate layer, and iridium oxide or platinum and an oxide of a valve metal are provided in an outer layer (Japanese Patent Application Laid-Open No. HEI 9-258572). 2-190491
JP, JP-A-2-200790, JP-A-59-2007
No. 150091). However, the intermediate layer of this electrode is also expensive and cannot be expected to have more durability than expected.

There is also known an intermediate layer of platinum or iridium oxide and an oxide of a valve metal, and an electrode comprising a platinum or lead dioxide layer on the intermediate layer (Japanese Patent Laid-Open No. 2-2 / 1990).
No. 94494) has a high oxygen overvoltage and an insufficient lifetime.

[0014]

SUMMARY OF THE INVENTION The main object of the present invention is to effectively suppress the formation of titanium oxide in the middle of an electrode having a coating mainly composed of iridium oxide on a conductive substrate such as titanium. An object of the present invention is to provide an electrode which can be used for a long time without any trouble when used for electrolysis accompanied by oxygen generation, and which exhibits a low anodic potential even in electrolysis at a high current density. .

[0015]

The present inventors have conducted various studies to develop an electrode for oxygen generation which has excellent durability and can be used for a long period of time. It has been found that by adding platinum metal to a tantalum oxide coating layer on a conductive substrate at a specific ratio, the electrical resistance can be reduced, and the deterioration of the electrode can be suppressed. Further, they found that by providing an iridium oxide-tantalum oxide layer further on the coating layer to which the platinum metal was added, deterioration in the intermediate coating layer portion could be suppressed without an increase in electric resistance. Based on the above, the present invention has been achieved.

That is, the present invention is achieved by the following (1) to (6) of the present invention. (1) On a conductive substrate, an underlayer of platinum metal containing 1 to 20 mol% of platinum and 80 to 99 mol% of tantalum in terms of metal and tantalum oxide is provided. An electrode for oxygen generation provided with an upper layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum.

(2) A first layer of tantalum oxide and platinum metal containing 1 to 20 mol% of platinum and 80 to 99 mol% of tantalum in terms of metal is provided on a conductive substrate, and the first layer is interposed. Then, a second layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum in terms of metal is provided, and further, iridium 40 to 79. An oxygen generating electrode provided with a third layer of iridium oxide and tantalum oxide containing 9 mol% and 60 to 20.1 mol% of tantalum.

(3) A first layer of tantalum oxide and platinum metal containing 1 to 20 mol% of platinum and 80 to 99 mol% of tantalum in terms of metal is provided on the conductive substrate, and the first layer is interposed. A second layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum in terms of metal is further provided thereon, and further has 40 to 79.9 in terms of metal in terms of metal. A third layer of iridium oxide and tantalum oxide containing 50% by mole and 60 to 20.1% by mole of tantalum, and at least one unit obtained by laminating the second layer and the third layer is provided thereon. Electrode for oxygen generation.

(4) First, a solution containing a platinum compound and a tantalum compound is applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 80 mol of tantalum in terms of metal. A first layer of platinum metal containing 99 mol% and tantalum oxide is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, followed by heat treatment in an oxidizing atmosphere to obtain a metal conversion. 80 to 99.9 mol% of iridium and tantalum 20
A method for producing an electrode for generating oxygen, which forms a second layer of iridium oxide and tantalum oxide containing 0.1 mol%.

(5) First, a solution containing a platinum compound and a tantalum compound is applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 80 mol of tantalum in terms of metal. A first layer of platinum metal containing 99 mol% and tantalum oxide is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, and then heat-treated in an oxidizing atmosphere to obtain a metal conversion. 80 to 99.9 mol% of iridium and tantalum 20
After providing a second layer of iridium oxide and tantalum oxide containing ~ 0.1 mol%, and further applying a solution containing an iridium compound and a tantalum compound thereon,
Heat-treated in an oxidizing atmosphere to obtain iridium 4 in metal conversion
A method for producing an electrode for oxygen generation that forms a third layer of iridium oxide and tantalum oxide containing 0 to 79.9 mol% and tantalum 60 to 20.1 mol%.

(6) First, a solution containing a platinum compound and a tantalum compound is applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 80 mol of tantalum in terms of metal. A first layer of platinum metal containing 99 mol% and tantalum oxide is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, followed by heat treatment in an oxidizing atmosphere to obtain a metal conversion. 80 to 99.9 mol% of iridium and tantalum 20
After providing a second layer of iridium oxide and tantalum oxide containing ~ 0.1 mol%, and further applying a solution containing an iridium compound and a tantalum compound thereon,
Heat-treated in an oxidizing atmosphere to obtain iridium 4 in metal conversion
Forming a third layer of iridium oxide and tantalum oxide containing 0 to 79.9 mol% and 60 to 20.1 mol% of tantalum, on which the second layer and the third layer are alternately formed at least. A method for producing an oxygen-generating electrode formed one layer at a time.

[0022]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail. Examples of the conductive substrate used for the electrode of the present invention include valve metals such as titanium, tantalum, zirconium, and niobium, and alloys of two or more metals selected from these valve metals.

In the electrode of the present invention, a layer made of platinum metal and tantalum oxide is provided as an underlayer on these conductive substrates. The ratio of platinum metal and tantalum in the underlayer is 1% in terms of metal.
It is necessary that タ ン 20 mol% and tantalum be in the range of 80-99 mol%. Within this range, good results can be obtained in the region where the proportion of platinum is small, and if the amount of platinum is too large, the cost is increased and the effect of increasing the adhesion strength between the upper layer and the conductive substrate is sufficiently exhibited. Not done. On the other hand, if the amount of platinum is too small, the film resistance of the underlying film is reduced, and the oxygen passing voltage is increased.

In order to sufficiently achieve the desired effect, in the coating layer, the platinum metal in the underlayer should be 0.1 to 3 mg in terms of metal.
/ cm ² is preferably applied. In addition, platinum is contained in the layer in a so-called spillover state,
The peak in X-ray diffraction does not occur or occurs in a broad state.

In the present invention, an upper layer made of iridium oxide and tantalum oxide is provided so as to cover the underlayer. The ratio of iridium and tantalum in terms of metal in the upper cover layer is 80 to 99.000 for iridium.
It is necessary that 9 mol% and tantalum be in the range of 20 to 0.1 mol%. Within this range, a higher percentage of iridium oxide will provide better results, but an excessively high percentage will reduce the adhesion strength and will not provide a sufficient effect. On the other hand, when the amount of iridium oxide is too small, an overvoltage is increased.

In this coating layer, iridium oxide is preferably applied at a rate of 0.01 to 7 mg / cm ^{2 in} terms of iridium. This coating layer has an iridium equivalent of 0.0
If it is less than 1 mg / cm ² , the electrode will consume a large amount during electrolysis and durability will be reduced. If it exceeds 7 mg / cm ² , the adhesion strength will be reduced.

Next, a preferred embodiment for producing this oxygen generating electrode will be described. A solution containing a platinum compound and a tantalum compound is applied on a conductive substrate and then heat-treated in an oxidizing atmosphere. Then, in terms of metal, platinum 1
A coating layer consisting of platinum metal and tantalum oxide is provided, containing 20 mol% and 80-99 mol% of tantalum.

The coating solution used at this time is a compound which becomes platinum metal by thermal decomposition, for example, chloroplatinic acid (H ₂ PtC)
l ₆ · 6H ₂ O), and platinum compounds such as chloroplatinic, compounds comprising tantalum oxide by thermal decomposition, for example, a tantalum compound such as tantalum alkoxides such as tantalum halide or ethoxy tantalum such as tantalum chloride, predetermined Can be adjusted by dissolving in a suitable solvent at the ratio of

In the heat treatment in an oxidizing atmosphere, the coating solution is coated on a conductive substrate, dried, and then, in the presence of oxygen, at an oxygen partial pressure of generally 0.05 atm or more, preferably This is performed by firing at a temperature in the range of 400 to 550 ° C. This operation is repeated a plurality of times until the required carrying amount is reached.

In this manner, the underlayer having a desired amount of support is obtained. In the present invention, a solution containing an iridium compound and a tantalum compound is further applied thereon, followed by heat treatment in an oxidizing atmosphere. 80 to 99.9 mol% of iridium and 20 to 0.1 of tantalum in terms of metal
An overcoat layer consisting of iridium oxide and tantalum oxide containing mol% is formed. Coating liquid compound comprising iridium oxide by thermal decomposition, for example, iridium acid _{(H 2 IrCl 6 · 6H 2} O) chloride compounds such as tantalum chloride becomes tantalum oxide and iridium compound such as iridium chloride by thermal decomposition to be used during this Can be adjusted by dissolving a tantalum compound such as tantalum halide or tantalum alkoxide such as ethoxy tantalum at a predetermined ratio in an appropriate solvent.

The heat treatment in an oxidizing atmosphere is carried out by applying this coating solution on an underlayer, drying it, and then baking it in the presence of oxygen, preferably at a temperature in the range of 400 to 550 ° C. Done. This operation is repeated several times until the required loading is reached. In this manner, the iridium oxide-tantalum oxide upper layer having a desired carrying amount is applied on the underlayer, and the electrode of the present invention is obtained.

If the heat treatment for forming these coating layers, ie, the underlayer and the upper layer, is not carried out in an oxidizing atmosphere, the oxidation becomes insufficient and the electrode is obtained because the metal exists in a free state. The durability is reduced.

Further, in the present invention, the above-mentioned underlayer and upper layer can be used as a first layer and a second layer, and a third layer of iridium oxide-tantalum oxide can be further provided thereon. The composition of the third layer is iridium 40 to
79.9 mol%, tantalum 60 to 20.1 mol%. The third layer further improves the adhesion strength and the mechanical strength during electrolysis.

However, if there is too much iridium in the composition of the third layer, the mechanical strength during electrolysis will decrease,
On the other hand, if the amount is too small, an overvoltage will increase.
The method of forming the third layer is exactly the same as described above.

The loading amount of iridium oxide in the third layer is preferably 0.01 to 7 mg / cm ^{2 in} terms of iridium. If the amount is too small, the adhesion strength is reduced. If the amount is too large, the adhesion strength is reduced.

In such a case, a plurality of second and third layers may be alternately stacked on the first layer. However, if the third layer is present in the uppermost layer, the effect is exhibited.
It is preferable to provide 10 units. By laminating the units of the second layer and the third layer in this manner, the mechanical strength during electrolysis is improved. When the units of the second layer and the third layer are stacked as described above, the amount of the support may be such that the total of the second layer and the third layer is as described above. Further, in the first, second and third layers, platinum group metals such as ruthenium, palladium, rhodium and osmium, and platinum group oxides thereof, and valve metal oxides such as titanium, niobium and zirconium are used. Tin oxide or the like may be contained at 10% by weight or less.

[0037]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Examples 1 to 5 and Comparative Examples 1 to 12 As shown in Table 1, a predetermined composition ratio of tantalum oxide of platinum metal, iridium oxide and tantalum oxide or iridium oxide and platinum metal and tantalum oxide was obtained. Chloroplatinic acid (H ₂ PtCl _6.
6H ₂ O) and tantalum ethoxide [Ta (OC ₂ H ₅ )
_5], chloroiridic acid _{(H 2 IrCl 6 · 6H 2} O)
Tantalum ethoxide _{[Ta (OC 2 H 5)} 5], or chloroiridic acid _{(H 2 IrCl 6 · 6H 2} O) and chloroplatinic acid _{(H 2 PtCl 6 · 6H 2} O) and tantalum ethoxide [Ta ( OC ₂ H ₅ ) ₅ ] in butanol and changing the composition ratio of platinum / tantalum, the composition ratio of iridium / tantalum, or the composition ratio of platinum / iridium / tantalum, to a base or upper surface of a metal conversion concentration of 80 g / l. A land coating solution was prepared.

Separately, the base coating solution was applied by a brush onto a titanium substrate etched with hot oxalic acid, dried and then baked in an electric furnace at 500 ° C. while blowing air. This coating, drying, and baking operation was repeated an appropriate number of times until a predetermined carrying amount was reached, thereby producing various coating base layers such as iridium oxide and tantalum oxide shown in Table 1. The amount of platinum carried on the underlayer was 0.3 to 0.7 mg.
/ cm ^2, and the same amount of supported metal was obtained in other underlayers containing no platinum.

Further, the coating solution for upper layer was applied to the underlayer by a brush, dried, and then baked in an electric furnace at 500 ° C. while blowing air. The operations of coating, drying and baking were repeated an appropriate number of times until a predetermined carrying amount was reached, thereby producing an electrode sample in which the underlayer was covered with an upper layer of iridium oxide and tantalum oxide. The loading amount of iridium in the upper formation was 1.3 to 1.7 mg / cm ² .

Next, the oxygen overvoltage was measured for the manufactured electrode. The measuring method was 30 by the potential scanning method.
The value at a current density of 20 A / dm ² in a 1 mol / l sulfuric acid aqueous solution at a temperature of 20 ° C. Table 1 shows the results.

The electrode was heated at 60.degree.
A life test was performed in an aqueous solution of sulfuric acid. Electrolysis was performed at a current density of 200 A / dm ² using platinum as a cathode and this electrode as an anode. The results are also shown in Table 1.

Regarding the change with time of the electrodes, the above life test was performed up to 1000 hours, the test was suspended, and the oxygen overvoltage after 1000 hours was obtained by the above-described method for measuring the oxygen overvoltage. The evaluation was performed in order to determine the difference from the above.

Further, in order to clarify the effect of the electrode provided with the base layer and the upper layer, the mechanical strength of the electrode during electrolysis was tested. As a test method, the above life test was performed up to 1000 hours, and then a vibration peeling test using ultrasonic waves was performed for 5 minutes.

The life of the electrode is indicated by ○: 2,000 hours or more, Δ: 1000 to 2,000 hours, ×: 1000 hours or less, and indicates the electrolyzable time.

The change with time of the oxygen overvoltage was ○: 0.3
V and below, the overvoltages are shown as △: 0.3 to 0.7 V and ×: over 0.7 V.

Further, the peeling of the electrode film thickness was ○: 5% or less,
Δ: 5 to 10%, ×: 10% or more of ultrasonic weight loss.

[0048]

[Table 1]

Examples 21 to 25 and Comparative Examples 21 to 24 In the same manner as in Examples 1 to 5, electrodes having a first layer, a second layer and a third layer shown in Table 2 in this order were produced. Table 2 shows the results. In Examples 21 to 25, the platinum loading of the first layer was 0.3 to 0.7 mg / cm ² , the iridium loading of the second layer was 1.2 to 1.6 mg / cm ² , The amount of iridium supported was 0.3 to 0.7 mg / cm ² , and the comparative examples were equivalent to or equivalent to these.

[0050]

[Table 2]

Examples 31 to 37 and Comparative Example 31 Coatings were formed in the same manner as in Examples 21 to 25 using the coating patterns shown in Table 3. Table 3 shows the results.
The amount of platinum carried on the coating layer of A was 0.3 to 0.7 mg / cm ² in Examples 31 to 37, and 0.8 to 1.2 mg in Comparative Example 31.
/ cm ² , the amount of iridium carried in the coating layer of B
37 to 1.2 to 1.6 mg / cm ² , Comparative Example 31 to 0.7 to 1.6 mg / cm ²
1.1 mg / cm ^2, the iridium loading of C coating layer of, 0.5~0.9mg / cm ² in Example 31, Example 33-3
7 and 0.6 to 1.0 mg / cm ² , and Comparative Example 31 with 1.0 to 1.0 mg / cm ² .
It was 4 mg / cm ² .

[0052]

[Table 3]

As is clear from these results, the electrode of the present invention shows a low oxygen overvoltage, has a small change over time in the oxygen overvoltage, has a strong mechanical adhesion strength, and has a remarkably long life.

[0054]

When the electrode of the present invention is used as an anode in electrolysis involving oxygen generation, it can withstand long-term use at a low cell voltage and can be electrolyzed at a high current density of 100 A / dm ² or more. It has excellent durability, high mechanical strength, and can be used for a long time. Further, the change of the oxygen overvoltage with time is small. Thus, the electrode of the present invention is suitable as an electrode for oxygen generation.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C25B 11/00-11/20 C25D 17/10

Claims (6)

(57) [Claims] 2. A method according to claim 1, wherein the conductive base is made of platinum and metal.
It has an underlayer of platinum metal and tantalum oxide containing 0 mol% and 80 to 99 mol% of tantalum, and through this underlayer, 80 to 99.9 mol% of iridium and 20 to 0. 0 tantalum in terms of metal. An oxygen generation electrode provided with an overlying layer of iridium oxide and tantalum oxide containing 1 mol%. 2. A method according to claim 1, wherein the conductive substrate has platinum on a metal basis.
A first layer of tantalum oxide and platinum metal containing 0 mol% and 80 to 99 mol% of tantalum is provided, and 80 to 99.9 mol% of iridium and 20 to 0 of tantalum in terms of metal are provided through the first layer. And a second layer of iridium oxide and tantalum oxide containing 0.1 mol% of iridium oxide and 40 to 79.9 mol% of iridium and 60 to 20.1 mol% of tantalum in terms of metal. An oxygen generation electrode provided with a third layer of tantalum oxide. 3. A method according to claim 1, wherein the conductive substrate has platinum on a metal basis.
A first layer of platinum metal containing 0 mol% and 80 to 99 mol% of tantalum and tantalum oxide is provided, and 80 to 99.9 mol% of iridium and 20 to 0. 0. A second layer of iridium oxide and tantalum oxide containing 1 mol% is provided, and iridium oxide and oxidization containing 40 to 79.9 mol% of iridium and 60 to 20.1 mol% of tantalum in terms of metal are further provided thereon. A third layer of tantalum is provided, and the second layer
An oxygen generation electrode provided with at least one unit in which a layer and a third layer are stacked. 4. A solution containing a platinum compound and a tantalum compound is first coated on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 99 of tantalum in terms of metal. A first layer of platinum metal and tantalum oxide containing mol% is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, and then heat-treated in an oxidizing atmosphere to obtain a metal equivalent. A method for producing an electrode for oxygen generation that forms a second layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum. 5. A conductive substrate is first coated with a solution containing a platinum compound and a tantalum compound, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 99 of tantalum in terms of metal. A first layer of platinum metal and tantalum oxide containing mol% is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, and then heat-treated in an oxidizing atmosphere to obtain a metal equivalent. A second layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum was provided, and a solution containing an iridium compound and a tantalum compound was further applied thereon. Thereafter, heat treatment is performed in an oxidizing atmosphere to obtain an iridium oxide containing 40 to 79.9 mol% of iridium and 60 to 20.1 mol% of tantalum in terms of metal. Method for producing oxygen generating electrode forming the third layer of the beam and tantalum oxide. 6. A conductive substrate is first coated with a solution containing a platinum compound and a tantalum compound, and then heat-treated in an oxidizing atmosphere to obtain 1 to 20 mol% of platinum and 80 to 99 of tantalum in terms of metal. A first layer of platinum metal and tantalum oxide containing mol% is formed, and then a solution containing an iridium compound and a tantalum compound is applied thereon, and then heat-treated in an oxidizing atmosphere to obtain a metal equivalent. A second layer of iridium oxide and tantalum oxide containing 80 to 99.9 mol% of iridium and 20 to 0.1 mol% of tantalum was provided, and a solution containing an iridium compound and a tantalum compound was further applied thereon. Thereafter, heat treatment is performed in an oxidizing atmosphere to obtain an iridium oxide containing 40 to 79.9 mol% of iridium and 60 to 20.1 mol% of tantalum in terms of metal. Beam and forming a third layer of tantalum oxide, further on this, the manufacturing method of the second layer and the oxygen generating electrode forming one by at least one layer of the third layer alternately.