JP2836890B2 - Electrode for organic matter electrolysis and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel electrode for organic substance electrolysis which can be suitably used for electrolysis of an electrolyte containing an organic substance, and a method for producing the same. More specifically, the present invention provides an electrode for organic electrolysis having excellent durability and a low oxygen overvoltage, which is preferably used for a reaction for generating oxygen at an anode by electrolyzing an aqueous solution containing a desired organic substance. The present invention relates to a method for easily and efficiently manufacturing this.

2. Description of the Related Art Conventionally, metal electrodes having a conductive substrate made of titanium metal and provided 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 chlorine generation by salt electrolysis (Japanese Patent Publication No. 46-21884, Japanese Patent Publication No. 48-3954, Japanese Patent Publication No. 5
No. 0-11330).

By the way, in the electrolytic industry, in addition to electrolysis accompanied by chlorine generation as in the case of the above-mentioned salt electrolysis, recovery of acids, alkalis or salts, collection of metals such as copper and zinc, plating, metal surface treatment, cathodic protection Electrolytic processes involving oxygen generation, such as wastewater treatment and electrolytic synthesis of organic substances, are also used in many fields.

And, in such electrolysis involving the generation of oxygen, a lead-based electrode is most commonly used. As other insoluble electrodes, an electrode obtained by coating iridium oxide and platinum on a titanium substrate, an iridium oxide-tin oxide electrode, an iridium oxide-tantalum oxide electrode, and other iridium oxide electrodes and a platinum-plated titanium electrode are known. .

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 anode dissolves remarkably, so the distance between the electrodes must be adjusted frequently.If a lead-based insoluble anode is used, it is mixed in the electrolytic solution. Plating defects occur due to the influence of the lead. Further, 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 worn and cannot be used.

Also, the iridium oxide-tantalum oxide-based electrode disclosed in JP-A-63-235493 has practically sufficient durability as a zinc plating anode containing no organic additive in the plating bath. In addition, when used as an anode for zinc plating containing an organic additive in a plating bath, durability is reduced and practicality is lost.

On the other hand, when an organic substance is synthesized by an electrolytic reduction reaction on a cathode, an anodic reaction is often used as a counter electrode reaction in which oxygen is generated by electrolysis of pure sulfuric acid.
Under normal operating conditions, if a platinum-iridium oxide-based anode is used as the anode, the anode has practically sufficient durability and can synthesize a desired organic substance without any problem. However, when organic matter in the cathode chamber is mixed with pure sulfuric acid in the anode chamber due to breakage of the diaphragm or the like, the consumption of the anode becomes extremely severe, and the anode becomes unusable in a short time.

On the other hand, a method for producing an electrode in which an outer surface is subjected to tantalum oxide or titanium oxide is known. For example, an electrode body in which at least a part of the surface of an electrode substrate is made of a thin film-forming metal, A titanium dioxide layer is formed on the surface of the metal, and the surface of the layer is coated with at least one layer of a platinum group metal and / or an oxide thereof and a layer of tantalum oxide in any order to manufacture an electrode for electrolysis. Method (Japanese Patent Publication No. 57-38675), a method of forming a layer of a working electrode material on the surface of a thin film forming metal support, and forming a layer of the working electrode material on the layer from a thermally decomposable organic compound of the thin film forming metal in a liquid vehicle. A method of producing an electrode by applying a coating consisting of
No. 3 specification). However, although the electrodes obtained by these methods are excellent in durability when used in mercury salt electrolysis, the layers of the working electrode material other than the tantalum oxide or titanium oxide layer applied to the outer surface are made of platinum group. Since it is composed of a metal or a platinum group metal oxide alone, it is not practical because it lacks durability as an electrode for organic matter electrolysis.

As described above, although it can be used as an electrode for generating oxygen in an electrolyte containing no organic substance, it does not cause abnormal wear even when the electrolyte contains an organic substance, and has excellent durability. Is eagerly awaited. The cause of abnormal depletion of the oxygen-generating electrode when organic substances are mixed in the electrode solution is complicated and unclear, but it is not clear that the organic substance is adsorbed on the electrode surface, such as a rise in anode potential and a decrease in the effective surface area of the electrode. Is presumed to be caused by

Problems to be Solved by the Invention The present invention provides an electrode for electrolyzing an electrolytic solution containing an organic substance, in which the electrode does not undergo abnormal wear, can be used for a long period of time without any trouble, and has a long life. An object of the present invention is to provide an electrode having excellent durability and exhibiting a low anode potential.

Means for Solving the Problems The present inventors have conducted various studies in order to develop an electrode for organic electrolysis having the above-mentioned preferable properties, and as a result, have found that iridium oxide having a specific composition is formed on a conductive substrate such as titanium.
A tantalum oxide layer is provided, an iridium oxide layer is provided thereon as necessary, and at least one oxide selected from titanium oxide, tantalum oxide, tin oxide, zirconium oxide, niobium oxide and antimony oxide is provided. By providing a layer comprising, it is possible to prevent organic substances in the electrolytic solution from directly adsorbing on the surface of iridium oxide or an iridium oxide-tantalum oxide mixture which is an electrode active material, and furthermore, by exhibiting a new catalytic property, the electrode becomes The present inventors have found that abnormal wear can be suppressed, durability can be improved, and a low anode potential can be achieved, and the present invention has been accomplished based on these findings.

That is, the present invention provides a method for manufacturing a semiconductor device, comprising the steps of: forming an iridium oxide and a tantalum oxide containing 50 to 90 atomic% of iridium and 50 to 10 atomic% of tantalum on a conductive substrate; An electrode for organic electrolysis and a conductive substrate, wherein an upper layer made of at least one oxide selected from tin oxide, zirconium oxide, niobium oxide and antimony oxide is provided. An iridium oxide layer is provided on a layer composed of iridium oxide and tantalum oxide containing 50 to 90 atomic% and tantalum of 50 to 10 atomic%, and further, titanium oxide, tantalum oxide, tin oxide, zirconium oxide, and oxide An electrode for organic electrolysis, comprising an outermost layer comprising at least one oxide selected from niobium and antimony oxide. To provide.

Here, "atomic%" indicates an atomic fraction expressed as a percentage (%).

This electrode for organic substance electrolysis is prepared, for example, by first applying a solution containing an iridium compound and a tantalum compound on a conductive substrate, and then performing a heat treatment in an oxidizing atmosphere to obtain 50 to 90 atomic% of iridium and tantalum in terms of metal. 50 to 10 atomic%
An underlayer made of iridium oxide and tantalum oxide containing is formed, and at least one compound selected from a titanium compound, a tantalum compound, a tin compound, a zirconium compound, a niobium compound and an antimony compound is formed thereon. After applying the contained solution, it is heat-treated in an oxidizing atmosphere to form at least one oxide selected from titanium oxide, tantalum oxide, tin oxide, zirconium oxide, niobium oxide and antimony oxide. A formation layer is formed, or a solution containing an iridium compound and a tantalum compound is first applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 50 to 90 atomic% of iridium and 50 of tantalum in terms of metal. Forming a layer of iridium oxide and tantalum oxide containing about 10 atomic%, After applying a solution containing an iridium compound, a heat treatment is performed in an oxidizing atmosphere to form an iridium oxide layer, and a titanium compound, a tantalum compound, a tin compound, a zirconium compound, a niobium compound, and an antimony compound are further formed thereon. After applying a solution containing at least one selected compound, heat treatment is performed in an oxidizing atmosphere to obtain titanium oxide, tantalum oxide,
It can be produced by forming an outermost layer made of at least one oxide selected from tin oxide, zirconium oxide, niobium oxide and antimony oxide.

 Hereinafter, 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, on these conductive substrates,
A layer composed of iridium oxide and tantalum oxide is provided. The proportion of each component in this layer must be in the range of 50 to 90 atomic% of iridium and 50 to 10 atomic% of tantalum in terms of metal. . If the iridium content is less than 50 atomic%, the durability of the electrode is reduced, and the conductivity of the iridium oxide-tantalum oxide layer itself is reduced.If the iridium content is more than 90 atomic%, the adhesion to the conductive substrate is reduced. The durability of the electrode decreases. Further, in order to sufficiently achieve the intended effect, iridium oxide in the coating layer should be 0.2 m in iridium conversion.
It is preferably applied at a rate of g / cm ² or more.

In the case where the coating layer is used as a base layer and an iridium oxide layer is formed thereon by coating, the coating layer is preferably in an amount of 5 mg / cm ² or less in terms of iridium. If it exceeds 5 mg / cm ² , the adhesion strength of the electrode film and the adhesion strength between the oxide layer provided on the outermost layer and the coating layer will be reduced, the electrode consumption will be increased, and the durability will be reduced.

The upper layer or the outermost layer is provided with a layer made of at least one oxide selected from titanium oxide, tantalum oxide, tin oxide, zirconium oxide, niobium oxide and antimony oxide. In order to sufficiently achieve the above, the coating amount of the upper layer or the outermost layer is 0.02 in metal conversion.
It is preferable to select in the range of 33 mg / cm ² . This coating amount is 0.0
If it is less than 2 mg / cm ² , the effect of preventing organic substances from being adsorbed to the iridium oxide-tantalum oxide layer or the iridium oxide layer of the base layer is not sufficient, and the iridium oxide-tantalum oxide layer or the iridium oxide layer of the base layer If, because the catalytic effect caused by the binding of the upper strata or outermost layer is insufficient, to the anode potential also decreases the durability of the elevated electrodes, also the anode potential becomes too high when it exceeds 3 mg / cm ² Therefore, the adhesion strength is inevitably reduced.

Next, a preferred embodiment for producing the electrode for organic electrolysis will be described. First, a solution containing an iridium compound and a tantalum compound is applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere. Then, an underlayer composed of iridium oxide and tantalum oxide containing 50 to 90 atomic% of iridium and 50 to 10 atomic% of tantalum in terms of metal is formed. Coating solution used at this time, compounds to be iridium oxide by pyrolysis, for example, chloride iridium acid _{(H 2 IrCl 6 · 6H 2} O), and iridium compounds such as iridium chloride, compounds comprising tantalum oxide by thermal decomposition,
For example, it can be prepared by dissolving a tantalum compound such as a tantalum halide such as tantalum oxide or a tantalum alkoxide such as ethoxy tantalum in an appropriate solvent at a predetermined ratio. This heat treatment in an oxidizing atmosphere is performed by applying the coating solution on a conductive substrate, drying the coating solution, and then firing the coating solution in the presence of oxygen, preferably 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.

The coating layer made of iridium oxide and tantalum oxide thus produced was placed on a base layer having a desired loading amount, and further, titanium oxide, tantalum oxide,
After applying a coating solution prepared by dissolving at least one compound such as tin oxide, zirconium oxide, niobium oxide, and antimony oxide, for example, a compound such as chloride or alkoxide, in a predetermined solvent in a predetermined ratio, the coating solution is oxidized. An upper layer is formed by heat treatment in a neutral atmosphere. This heat treatment in an oxidizing atmosphere is performed by applying the coating solution on the underlayer, drying, and baking in the presence of oxygen, preferably at a temperature in the range of 400 to 600 ° C. . This operation is repeated a plurality of times until the required load is reached. In this way, the oxide underlayer having a desired amount of support is applied on the underlayer, and the electrode of the present invention is obtained.

Further, a preferred embodiment for producing another electrode for organic substance electrolysis will be described. First, a solution containing an iridium compound and a tantalum compound is applied on a conductive substrate, and then heat-treated in an oxidizing atmosphere. Then, an underlayer composed of iridium oxide and tantalum oxide containing 50 to 90 atomic% of iridium and 50 to 10 atomic% of tantalum in terms of metal is formed. Coating solution used at this time, compounds to be iridium oxide by pyrolysis, for example, iridium oxide acid _{(H 2 IrCl 6 · 6H 2} O), and iridium compounds such as iridium chloride, compounds comprising tantalum oxide by thermal decomposition,
For example, it can be prepared by dissolving a tantalum compound such as a tantalum halide such as tantalum chloride or a tantalum alkoxide such as ethoxy tantalum in an appropriate solvent at a predetermined ratio. This heat treatment in an oxidizing atmosphere is performed by applying the coating solution on a conductive substrate, drying the coating solution, and then firing the coating solution in the presence of oxygen, preferably 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.

On the underlayer with the desired loading of the coating layer composed of iridium oxide and tantalum oxide produced as described above,
By applying a solution containing an iridium compound and then performing a heat treatment in an oxidizing atmosphere, an iridium oxide layer is preferably applied in an amount equivalent to an iridium amount of 5 mg / cm ² or less in terms of metal. The solution containing the time iridium compound used is a compound comprising iridium oxide by pyrolysis, for example, chloride iridium acid (H ₂ IrCl ₆ · 6H ₂
It can be prepared by dissolving an iridium compound such as O) in a suitable solvent.

The underlayer composed of iridium oxide and tantalum oxide and the coating layer composed of an intermediate layer composed of iridium oxide are formed to a desired carrying amount, and titanium oxide, tantalum oxide, and tin oxide are further thermally decomposed thereon. After applying a coating solution prepared by dissolving at least one compound such as zirconium oxide, niobium oxide, and antimony oxide, for example, a compound such as chloride or alkoxide, in a predetermined ratio in a suitable solvent, An outermost oxide layer is formed by heat treatment in an atmosphere. This heat treatment in an oxidizing atmosphere is performed by applying the coating solution on the coating layer, drying and then firing in the presence of oxygen, preferably at a temperature in the range of 400 to 600 ° C. . This operation is repeated a plurality of times until the required load is reached. In this way, the outermost layer of the oxide having a desired amount of support is applied on the coating layer, and the electrode of the present invention is obtained.

Effect of the Invention When the electrode of the present invention is used as an anode in electrolysis of an organic substance such as electrolysis of an electrolyte containing an organic substance, the anode potential can be lowered, and it can be used for a long time at a low cell voltage, and can be used for a long time. In addition to being excellent in durability, even when electrolysis is performed at a high current density of 100 A / dm ² or more, it has excellent durability and can be used for a long time.

Thus, the electrode of the present invention is suitable as an electrode for organic electrolysis.

Examples Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

Examples 1 to 7 and Comparative Examples 1 to 8 A predetermined ratio of iridium chloride (H ₂₎ corresponding to the composition ratio of iridium oxide to tantalum oxide in the underlayer shown in Table 1 was used.
IrCl ₆ · 6H ₂ O) and tantalum butoxide [Ta (OC
₄ H _{9) 5]} was dissolved in butanol to prepare a iridium / metal varying composition ratio of tantalum concentration in terms of 80 g / underlayer coating liquid for.

Further, a predetermined ratio of titanium butoxide, tantalum butoxide, which corresponds to the composition of the oxide of the upper layer shown in Table 1,
At least one compound selected from tin bitoxide, zirconium butoxide, niobium butoxide, and antimony butoxide was dissolved in butanol to prepare a coating solution for a base material having a concentration of 50 g / metal equivalent.

Separately, on a titanium substrate etched with hot oxalic acid,
The undercoating solution was applied with a brush, dried, and then baked at 500 ° C. in an electric furnace while blowing air. These coating, drying, and baking operations were repeated an appropriate number of times until a predetermined amount was carried, thereby producing each intermediate sample in which the substrate was covered with an underlayer of iridium oxide and tantalum oxide.

Further, the coating solution for upper layer was applied on the base layer of each intermediate sample with a brush, dried, and then baked in an electric furnace at 500 ° C. while blowing air. These coating, drying, and baking operations were repeated to prepare an electrode sample in which the underlayer was covered with the oxide upper layer.

For comparison, electrode samples provided with the coating layers shown in Table 1 were prepared.

Next, the anode potential was measured for these prepared electrodes. The value was measured at a current density of 20 A / dm ² in a 70 g / phenol sulfonic acid aqueous solution at 30 ° C. by a potential scanning method. Table 1 shows the results. Further, a life test was performed on the electrode in a 70 g / phenol sulfonic acid aqueous solution at 50 ° C. Using this electrode as an anode, platinum was used as a cathode, and electrolysis was performed at a current density of 100 A / dm ² . The results are also shown in Table 1.

As is evident from these results, the electrode of the present invention shows a low anodic potential and has a remarkably long life.

The electrode life is as follows: ○: 1000 hours or more, Δ: 500 to 100
0 hours, x: displayed in 500 hours or less, indicating the electrolyzable time.

Examples 8 to 12 and Comparative Examples 9 to 14 In the same manner as in the preparation of the underlayer in the above example, a coating layer of iridium oxide and tantalum oxide having a composition ratio of iridium 70 at.% And tantalum 30 at. As above, so that the metal equivalent concentration of 80g / above,
The coating solution prepared by dissolving iridic acid in butanol was applied with a brush, dried, and baked in an electric furnace at 500 ° C. while blowing air. These coating, drying and baking operations were repeated to coat the iridium oxide layer on the underlayer.

Then, on top of this, so as to have a metal equivalent concentration of 50 g /
After applying a coating solution prepared by dissolving at least one compound selected from titanium butoxide, tantalum butoxide, tin butoxide, zirconium butoxide, niobium butoxide and antimony chloride in butanol with a brush and drying, an electric furnace While blowing in the air
Bake at 500 ° C. These coating, drying and baking operations were repeated to prepare an electrode sample in which the oxide outermost layer was coated on the iridium oxide layer.

For comparison, an electrode sample provided with a coating layer shown in Table 2 was prepared.

Next, the oxygen overvoltage was measured for these prepared electrodes. The measuring method is 30 ° C, 220g /
Sodium sulfate + 20 g / sodium acetate + sulfuric acid (pH =
1) The value at a current density of 20 A / dm ² in an aqueous solution was determined.
Table 2 shows the results.

A life test was performed on this electrode at 50 ° C. in an aqueous solution of 220 g / sodium sulfate + 20 g / sodium acetate + sulfuric acid (pH = 1). Using this electrode as an anode, platinum was used as a cathode, and electrolysis was performed at a current density of 150 A / dm ² . The results are shown in Table 2.

As is evident from these results, the electrodes of the present invention show a low oxygen overpotential and have a significantly longer life.

The electrode life is as follows: ○: 1000 hours or more, Δ: 500 to 100
0 hours, x: displayed in 500 hours or less, indicating the electrolyzable time.

Example 13 The electrodes obtained in Example 3 and the electrodes obtained in Comparative Examples 3 and 4 were subjected to a life test at 50 ° C. in a 5% by weight aqueous solution of ammonium adipate. In other words, these electrodes were used as anodes and titanium was used as the cathode, and the current density was 20 A /
The electrolysis was carried out in dm ^2.

As a result, the electrodes of Comparative Examples 3 and 4 could not be electrolyzed for 1000 hours or less, but the electrode of Example 3 could be electrolyzed for 1500 hours or more.

From the above results, it is clear that the electrode of the present invention has excellent durability in electrolysis of an electrolytic solution containing an organic substance.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhide Oe 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-2-294494 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C25B 11/00-11/20

Claims (4)

(57) [Claims] 1. The method according to claim 1, wherein iridium 50 is converted into metal on a conductive substrate.
Selected from titanium oxide, tantalum oxide, tin oxide, zirconium oxide, niobium oxide, and antimony oxide on an underlayer consisting of iridium oxide and tantalum oxide containing ~ 90 at% and 50 to 10 at% tantalum An electrode for organic electrolysis, comprising an upper layer made of at least one oxide. 2. The method according to claim 1, wherein the conductive substrate is provided with iridium 50 in terms of metal.
An iridium oxide layer is provided on a layer composed of iridium oxide and tantalum oxide containing 90 to 90 atomic% and tantalum of 50 to 10 atomic%, and titanium oxide, tantalum oxide, tin oxide, zirconium oxide, and niobium oxide are further provided thereon. And an outermost layer comprising at least one oxide selected from the group consisting of antimony oxide and antimony oxide. 3. A solution containing an iridium compound and a tantalum compound is first coated on a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 50 to 90 iridium in terms of metal.
An underlayer consisting of iridium oxide and tantalum oxide containing at least 10 atomic% and 50 to 10 atomic% of tantalum is formed, and then a titanium compound, a tantalum compound, a tin compound, a zirconium compound, a niobium compound and an antimony compound are formed thereon. After applying a solution containing at least one selected compound, heat treatment is performed in an oxidizing atmosphere to at least one selected from titanium oxide, tantalum oxide, tin oxide, zirconium oxide, niobium oxide and antimony oxide. A method for producing an electrode for organic electrolysis, comprising forming an upper layer made of one kind of oxide. 4. A solution containing an iridium compound and a tantalum compound is first applied onto a conductive substrate, and then heat-treated in an oxidizing atmosphere to obtain 50 to 90 iridium in terms of metal.
A layer containing iridium oxide and tantalum oxide containing at least 10 atomic% of tantalum and 50 to 10 atomic% of tantalum is formed, and then a solution containing an iridium compound is applied thereon, and then heat-treated in an oxidizing atmosphere to form iridium oxide. To form a titanium compound, a tantalum compound,
After applying a solution containing at least one compound selected from a tin compound, a zirconium compound, a niobium compound, and an antimony compound, the composition is heat-treated in an oxidizing atmosphere to form titanium oxide, tantalum oxide, tin oxide, and oxide. A method for producing an electrode for organic substance electrolysis, comprising forming an outermost layer made of at least one oxide selected from zirconium, niobium oxide and antimony oxide.