JPH025832B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a manufacturing technology for an electrolytic anode that has low overvoltage and durability.More specifically, the present invention relates to a method for manufacturing an anode for electrolysis that has low overvoltage and durability. The coating layer is formed integrally with three metal oxides selected from ruthenium oxide, palladium oxide, and iridium oxide.
The present invention relates to a method for producing a dimensionally supported electrode for electrolysis. Electrolytic electrodes that are generally widely used include electrolytic electrodes in which various electrochemically active substances are coated and bonded on the surface of a corrosion-resistant conductive substrate.
The basic characteristics required for this are basically 2
The conditions for bonding the coating layer to the substrate are that it has high mechanical bonding strength, strong chemical corrosion resistance, and electrical conductivity; on the other hand, the coating layer itself As such, it has a high mechanical bonding strength between the components constituting the coating layer, has strong chemical corrosion resistance, and of course has a certain electrical conductivity.
In addition, it is desired that the overvoltage during electrode reaction be low. Many common electrodes for electrolysis are known, in which the surface of a corrosion-resistant conductive substrate is coated with an electrochemically active substance having a composition containing a platinum group metal component. Among these electrodes for electrolysis, the coating layer is either made of platinum group metal itself or made of platinum group metal oxide, but the former electrode coated with platinum group metal has been used for a very long time. used,
In particular, many improvements have been made to electrodes coated with platinum metal, and electrodes have been developed that have high bonding strength of the coating layer itself and bonding strength to the substrate, excellent corrosion resistance, and durability. However, although this type of platinum metal-coated layer electrode has many excellent properties, its applications are limited. The main reason for this is that, compared to other electrodes in practical use, the overvoltage characteristics of the electrode with a platinum metal coating layer against chlorine and oxygen are as low as other electrodes in the early stages of electrolysis. However, it increases over time and reaches a high value,
This is because it has the advantage of increasing electrolytic power consumption and increasing costs as a result, and because the increase in overvoltage may cause electrolytic reactions other than the intended purpose, which may impede the stated purpose. It is. Therefore, in order to solve the problem of overvoltage increasing over time in electrodes coated with platinum metal, several methods have been proposed, such as adding various metals to platinum metal using various means. methods of adding and alloying to suppress the increase,
A method has been proposed in which a platinum metal-coated electrode with increased overvoltage is reactivated by cathodic electrolysis. However, electrodes manufactured by such methods have disadvantages such as being difficult to manufacture practically due to complicated processes, resulting in electrodes with poor corrosion resistance, and the duration of the active effect is short. However, it has some drawbacks, such as, so far, it has not been put to practical use. On the other hand, an electrode coated with a platinum group metal oxide whose coating layer component is ruthenium oxide, rhodium oxide, palladium oxide, or iridium oxide has low overvoltage, excellent durability, and stable catalytic function. In addition, a typical method for manufacturing platinum group metal oxide-coated electrodes is to apply a solution containing a compound that forms a platinum group metal oxide by thermal decomposition onto the substrate surface. Since this method is a thermal decomposition method that involves obtaining the platinum group metal oxide using a combination of multiple components, it has many advantages such as being able to easily obtain the platinum group metal oxide even if it is a combination of multiple components. However, if the coating layer is composed only of platinum group metal oxides, the bonding strength between the coating layer and the substrate and the bonding strength of the coating layer itself are extremely low, and there is a drawback that the coating layer may fall off during the electrolytic reaction. There was a problem with the product's lifespan being extremely short, making it impractical. Therefore, in order to increase the life of the platinum group metal oxide coated electrode, a corrosion-resistant oxide such as titanium oxide or a second component such as a platinum group metal was added to the platinum group metal oxide component, and a mixture of these was added. The bonding strength of the coating layer is increased by means such as oxidation, alloying, or mixed crystal formation. The purpose of the present invention is to solve the above-mentioned problems of electrolytic electrodes whose substrates are coated with platinum group metal components, and to provide advantages of both platinum metal and platinum group metal oxide as coating layer components. It is an object of the present invention to provide a method for manufacturing an electrode for electrolysis, which has low overvoltage, excellent durability, and is useful in the field of electrolysis application in the electrochemical industry, while making active use of the above. According to the method of the present invention, a porous platinum layer coated on at least a portion of the surface of a corrosion-resistant conductive substrate;
There is provided an electrode for electrolysis comprising at least one metal oxide selected from ruthenium oxide, palladium oxide, and iridium oxide three-dimensionally supported on the porous platinum layer. The electrolytic electrode of the present invention has a first electrochemically active component coating layer made of porous platinum on the surface of a corrosion-resistant conductive substrate such as titanium, in which ruthenium oxide, palladium oxide, and It is characterized by the fact that the second electrochemically active component made of a metal oxide selected from iridium is supported three-dimensionally, which gives rise to the advantages that both of the above-mentioned electrochemically active components have respectively. While making the most of this, we succeeded in lowering the overvoltage of the electrodes and significantly improving durability. The electrode of the present invention can be widely applied to the electrolysis of various substances by changing the type of metal oxide used as the second electrochemically active component. For example, iridium oxide is a desirable metal oxide for electrolysis in sulfuric acid acidic electrolyte solutions, seawater electrolysis accompanied by generation of sodium hypochlorite, electrolysis in low chlorine ion concentration solutions, etc. Further, in salt electrolysis containing a high concentration of chlorine ions, the metal oxide is preferably ruthenium oxide, palladium oxide, or a combination of these components. As is clear from Examples 4 and 5 below, the life of the electrode of the present invention can be extended by increasing the amount of the porous platinum metal layer covered or the amount of metal oxide supported thereon. . The electrode of the present invention described above has platinum coated in a porous manner on the surface of a corrosion-resistant conductive substrate, and then a metal oxide selected from ruthenium oxide, palladium oxide, and iridium oxide is applied to the porous coating layer. It can be produced by three-dimensionally supporting the substrate, and more specifically, (a) forming a multi-platinum layer on at least a portion of the surface of a corrosion-resistant conductive substrate by electroplating, and then ( b) by infiltrating the porous platinum layer with a solution of at least one metal compound capable of producing a metal oxide selected from ruthenium oxide, palladium oxide, and iridium oxide by thermal decomposition, and then heating it. and convert the metal oxide into a metal oxide, and if necessary, the above-mentioned
It can be manufactured by repeating the operations (a) and (b). Therefore, in order to form a porous platinum metal coating layer on the surface of a corrosion-resistant conductive substrate, there are two methods: forming a porous platinum metal directly on the substrate surface, and forming a porous platinum metal coating layer after forming a platinum metal coating layer. The latter method allows the solution of the metal compound to penetrate sufficiently and support the metal oxide three-dimensionally even if the surface of the platinum metal coating layer is roughened. Obtaining status may be difficult. Therefore, in order to form a porous platinum metal coating layer in the electrolytic electrode of the present invention, it is desirable to adopt the former method, that is, a means to form a porous platinum metal layer directly on the substrate surface. There are electroplating methods, thermal spraying methods, pyrolysis methods, etc.
Among these, the electroplating method is superior in terms of characteristics and economy, and among these electroplating methods, a state in which the electrodeposited platinum metal is formed into porous and spherical aggregates has emerged. It is desirable that the In addition, if you want to obtain platinum metal with higher porousness, after directly forming a porous platinum metal layer,
Furthermore, it is an effective method to perform treatment to increase the porous state by chemical or electrochemical methods. In addition, in the manufacturing process, the platinum metal coating layer is required to have a porous state that allows penetration of a solution containing a metal compound that can generate the metal oxide, and further, in the heating process of pyrolysis, The bonded portion between the substrate and the platinum metal coating layer must be in a bonded state that does not deteriorate due to reaction with oxidizing gas and volatile components in the compound. Therefore, in order for the porous platinum metal coating layer to have sufficient permeability to the solution containing the metal compound, it is preferable that the apparent density of the platinum metal coating layer be 19 g/cm ³ or less. If the condition is increased so that the apparent density becomes 8 g/cm ³ or less, the mechanical strength may decrease and the life of the electrode may be shortened. On the other hand, the pyrolytic metal compound and its solvent used to three-dimensionally precipitate the metal oxide into the porous platinum metal coating layer smoothly penetrate into the platinum metal coating layer. The viscosity of the solution is low,
It is also desirable that the concentration of the metal compound does not become high. Furthermore, it is also effective to apply ultrasonic waves to the substrate in order to improve the penetration of the metal compound. Next, the present invention will be further explained with reference to examples and drawings. Example 1 A titanium metal plate was degreased with a trichlene degreasing solution, and a substrate was prepared by surface treatment with a hydrofluoric acid aqueous solution and concentrated hydrochloric acid, and electroplated using a platinum plating bath in which dinitrodiaminoplatinum was dissolved in a sulfuric acid aqueous solution. A porous platinum metal coating layer having an apparent density of about 16 g/cm ³ and an electrodeposited amount of 4.5 mg/cm ² was formed on the surface of the titanium metal plate substrate. Next, 1.07 g of chloroiridic acid was added to butanol.
After preparing the penetrating solution by dissolving it in 10ml, the amount of iridium oxide is 0.14 in terms of weight of iridium metal.
The penetrating solution was taken with a micropipette to a concentration of mg/cm ² and infiltrated into the platinum metal coating layer, then dried at room temperature for 1 hour by vacuum drying method, and then heated to 500°C.
An electrode for electrolysis was prepared by heating in the atmosphere for 20 minutes. For comparison, an electrode 1-1 was prepared in which a titanium metal plate substrate was coated with 4.5 mg/cm ² of platinum metal using the same process as above. Furthermore, an iridium chloride solution with a concentration three times that of the penetrating solution used above was applied to the surfaces of the titanium metal plate substrate pretreated in the same manner as described above and the rolled bulk platinum metal plate degreased with Triclene degreasing solution. Electrodes 1-2 were coated with iridium metal at an amount of 0.14 mg/cm ² , which is the same amount as the above electrode in terms of weight, and dried and heated in the same manner as above to coat iridium oxide on the titanium metal surface, and Electrodes 1-3 were prepared by coating iridium oxide on the surface of a bulk platinum metal plate. Next, electrolysis was carried out at a current density of 400 A/dm ² using an M/l aqueous sulfuric acid solution with an electrode solution temperature of 55° C., and the electrode potential at a current density of 1 A/dm ² was measured at regular intervals. The results are shown in the graph of FIG. 1, in which time (hr) is plotted on the horizontal axis and electrode potential (V) relative to silver chloride is plotted on the vertical axis. The results of the above electrodes 1-1, 1-2, 1-3 and the electrode of the present invention are curves C ₁ , C ₂ ,
As shown in C ₃ and C ₄ . From Figure 1, the electrode of the present invention, which is composed of a combination of a porous platinum metal coating layer and iridium oxide, maintains a lower electrode potential (lower overvoltage) for a longer time than electrode 1-1, and has a much longer electrode life. It was found that the electrode potential remained low for a long time, similar to that of electrodes 1-2 and 1-3. Furthermore, it can be seen that the electrode of the present invention maintains a low electrode potential under the present electrolytic conditions until most of the electrode covering is consumed. Example 2 After degreasing the titanium metal plate for the substrate and surface treating it with a hydrofluoric acid aqueous solution and a sulfuric acid aqueous solution, the above Example 1 was carried out.
A platinum metal coating layer having an average apparent density of 16 g/cm ³ and an electrodeposition amount of 1.1 mg/cm ² was formed on the surface of a titanium metal plate in the same manner as in . Next, add 0.25 g of ruthenium chloride to 10 ml of butanol.
In the same manner as in Example 1, using ^a penetrant solution dissolved in
It was carried dimensionally. However, the heating temperature during pyrolysis was 430°C. Next, 0.5 mg/cm ² of electrodeposited platinum metal was further formed on the surface of the electrode formed above, and then 0.01 mg/cm ² of ruthenium oxide was supported in the same manner as above in terms of the weight of ruthenium metal to prepare an electrode. did. For comparison, an electrode 2-1 was prepared in which a platinum metal coating layer was formed on a titanium metal plate using the same process as above, and an electrode 2-1 was fabricated using the same penetrating liquid as used in the above example. After coating the surfaces of both a titanium metal plate and a bulk platinum metal plate that had been pretreated in the same way, the same amount of ruthenium oxide as above was applied to the titanium metal plate by heating at 430°C in the air for 20 minutes. A coated electrode 2-2 and a coated electrode 2-3 on a bulk platinum metal plate were prepared. Next, these electrodes were electrolyzed with 200 g/aqueous sodium chloride solution at a liquid temperature of 45° C. at a current density of 100 A/dm ² , and the electrode potential at a current density of 10 A/dm ² was measured at regular intervals. The results are shown in a graph (FIG. 2) with the same axis index as FIG. 1. Electrode 2-1, 2-2, 2-3
and the results of the electrode of the present invention are curves C ₁ ′,
As shown in C ₂ ′, C ₃ ′, and C ₄ ′. From FIG. 2, it can be seen that the electrode of the present invention, which is composed of a combination of porous platinum metal coating and ruthenium oxide, maintains a lower electrode potential for a longer time than the comparative electrode, and is an electrode with excellent durability. Example 3 After surface treatment of a titanium metal plate substrate in the same manner as in Example 2 above, porous holes were formed on a titanium metal plate plated by electroplating using a platinum plating bath in which dinitrodiaminoplatinum was dissolved in an alkaline aqueous solution. The formed platinum metal coating layer was further treated with a mixed acid aqueous solution of hydrochloric acid and nitric acid to give an apparent density of about 14 g/cm ³ and an electrodeposition amount of 2.3.
A platinum metallization layer of mg/cm ² was formed. Next, add 0.832 g of palladium chloride to an aqueous solution of hydrochloric acid.
Using the penetrating solution dissolved in 10 ml, the same procedure as in Example 1 was carried out to obtain 0.10 mg/weight of palladium metal.
The electrode of the present invention was prepared by three-dimensionally supporting palladium oxide of cm ² . The heating temperature at this time was 60°C. Electrode 3 for comparison, in which a platinum metal coating layer was formed on a titanium metal plate in the same process as the electrode in question.
1 was prepared, and using a coating liquid with twice the concentration of the penetrating liquid used above, 1.0 mg/cm ² of palladium oxide was added to titanium under the same heating conditions as above. Electrode 3-2 was prepared by coating a metal plate, and electrode 3-3 was prepared by coating a bulk platinum metal plate with the same amount of palladium oxide as the electrode of the present invention. These electrodes were then subjected to the same electrolytic test as in Example 2 above. The results are shown in a graph (FIG. 3) with vertical and horizontal axes of indicators similar to FIG. 1. Electrode 3-1, 3-2, 3-
3 and the results of the electrodes of the invention are curves C ₁ ″,
As shown in C ₂ ″, C ₃ ″, and C ₄ ″. As shown in Figure 3, the electrode of the present invention, which is a combination of a porous platinum metal coating layer and palladium oxide, also has a lower electrode potential than the comparative electrode. hold for a long time,
It can be seen that the electrode has excellent durability. Example 4 A platinum metal coating layer with an apparent density of 16 g/cm ³ and an electrodeposition amount of 1.7 mg/cm ² was formed on a base titanium metal plate in the same manner as in Example 1, and the same penetration rate as used in Example 1 was applied. Three types of electrodes of the present invention (three electrodes of sample Nos. 1, 2, and 3) with varying amounts of supported iridium oxide were prepared using a penetrating solution obtained by appropriately diluting the solution with butanol. Next, these electrodes were electrolyzed in a 1M/l sulfuric acid aqueous solution at a temperature of 55°C at a current density of 10A/ ^dm2 .
The electrode life was measured until the electrode potential reached 1.7V versus silver chloride, and the results are shown in Table 1 below. From Table 1, it can be seen that by increasing the amount of metal oxide supported on the electrode, the life of the electrode can be effectively increased under the above electrolytic conditions.

[Table] Example 5 Three types of electrodes for electrolysis were prepared in the same manner as in Example 1, with different amounts of the platinum metal coating layer on the base titanium metal plate. The electrodes of Sample Nos. 1', 2' and 3' were subjected to the same electrolytic test as in Example 1, and the life of the electrode was measured until the electrode potential reached 1.7V with respect to the silver chloride electrode potential. The results are shown in Table 2 below. From Table 2, it can be seen that by increasing the amount of platinum metal coating on the electrode, the life of the electrode can be effectively increased under the above electrolytic conditions.

[Table] Example 6 Titanium plate material equivalent to JIS class 2 ( ^t 1× ^w 20× ^l 20
mm) at 20℃ after degreasing and cleaning with Triclean.
Treated with HF aqueous solution for 6 minutes, then 50% at 120℃
It was immersed in a H ₂ SO ₄ aqueous solution for 5 minutes, then rapidly rinsed with water in a N ₂ gas stream while being withdrawn, and then soaked at 20℃ for 0.3 minutes.
% HF aqueous solution for 1 minute, and then immediately and thoroughly washed with water. After washing with water, Pt(NH ₃ ) ₂ (NO ₂ ) ₂ is converted to 10g/Pt.
Add 5g/each of sodium nitrite and ammonium nitrate to the ammonia aqueous solution containing pH≒9.
and in a Pt plating bath added at a concentration of 20 g/
After Pt plating is performed by controlling the specified temperature and current, it is treated with a mixed aqueous solution of hydrochloric acid and nitric acid, and the apparent density is about 14 g/cm ² and the amount of electrodeposition is 2.3 mg/cm on the titanium plate. A porous, high-strength platinum coating layer of ² was formed. Then 0.832 g of palladium chloride in 10 ml of hydrochloric acid
A certain amount of the solution was taken with a micropipette, and it was evenly dropped onto the entire Pt-plated surface of the platinum-plated titanium plate obtained above to allow it to penetrate. After vacuum drying this board at room temperature for 1 hour, it was placed in the atmosphere at 600℃.
Heat for 20 minutes. As a result, an "electrode A" according to the present invention was obtained in which 0.10 mg/cm ² of palladium oxide was three-dimensionally supported as palladium metal in the porous platinum metal layer on the titanium plate. Comparative example 1 Titanium plate equivalent to JIS class 2 ( ^t 1 x ^w 20 x ^l 20mm)
was washed with a hot oxalic acid aqueous solution by the method described in Example 1 of JP-A No. 52-68076, and then thoroughly stirred with a brush containing 20 g of H ₂ PtCl _{6.6H 2} O and 150 ml of butyl alcohol. The applied coating solution was applied, dried, and then heated in air at 500°C for 10 minutes. This operation was repeated 50 times to form the first platinum coating layer. When this first platinum coating layer was observed under an electron microscope, it was found that the surface was smooth and had a dense, not porous structure, although some cracks were observed here and there. Next, palladium chloride 16.7
A coating solution consisting of 200 ml of butyl alcohol and 10 ml of concentrated hydrochloric acid was applied with a brush onto the first coating layer, and after drying, it was heated in the air at 600°C for 10 minutes, and this operation was repeated twice to form the second coating layer. A coating layer was obtained. As a result, "electrode B" having approximately 2.3 mg/cm ² of platinum as the first coating layer and approximately 0.09 mg/cm ² of palladium oxide (calculated as palladium metal) as the second coating layer on the titanium substrate was obtained. I got it. The amounts of platinum and palladium were determined by fluorescent X-ray method (the same applies to the following electrodes). Comparative Example 2 A titanium plate equivalent to JIS Class 2 was pretreated by a method known per se (the method described in Example 1 of Japanese Patent Publication No. 7782/1982 was adopted as the known method).
That is, after exposing the titanium plate to Triclean vapor to remove oil and fat, it was soaked in an alkaline degreasing solution for 10 minutes.
It was soaked for a minute, thoroughly degreased, and then washed with water. Next, add 7 to a mixture of the following composition heated to 50℃.
Soaked for minutes. 200 ml of 86% phosphoric acid 25 ml of 60% nitric acid 50 ml of 48% hydrofluoric acid A total of 500 ml of water After washing with water, immerse in a 5% aqueous solution of hydrofluoric acid for 3 minutes, and immediately wash with water. . Next, polishing powder (80
Clean the surface by polishing it with a mixture of mesh (passed through mesh) and a neutral detergent, degrease it again in an alkaline degreasing solution for 10 minutes, wash it with water, and then immerse it in a 10% sulfuric acid bath at 30°C for 1 minute and wash it with water. Ivy. Then, immediately follow the usual method [Here, "Precious Metal Metsuki" by Shuntaro Tagawa, published June 15, 1965, 80
81 (Kyoritsu Shuppan Co., Ltd.)], plating was carried out in a diamino dinitroplatinum bath to obtain a gold-plated layer with an electrodeposition amount of 2.1 mg/cm ² . If left as is, the adhesion strength would be low and would easily peel off, so based on the description in the above patent publication, heating was performed at 600° C. for 30 minutes in an argon atmosphere to improve the adhesion strength. The apparent density of this platinum-plated layer was about 20 g/cm ³ , and when observed with an electron microscope, the surface was smooth and non-porous. Next, a second coating layer of palladium oxide was formed on the platinum plating layer in the same manner as in the case of electrode B. As a result, an "electrode C" having approximately 2.1 mg/cm ² of platinum as the first coating layer and approximately 0.1 mg/cm ² of palladium oxide in terms of palladium metal as the second coating layer on the titanium substrate was obtained. I got it. The composition of the bath used to form the platinum plating layer and the plating conditions were as follows. (1) Composition of platinum plating bath Dinitrodiaminoplatinum 16.5g / Ammonium nitrate 100 〃 Sodium nitrite 10 〃 Ammonia water (28%) 50 〃 (2) Plating conditions Bath temperature 95℃ Current density 1A/dm ^2Anode Platinum Comparative Example 3 An electrode was produced as described below in accordance with the method described in Example 1 of JP-A-51-78787. Titanium plate equivalent to JIS class 2 ( ^t 1 x ^w 20 x ^l 20mm)
was washed with a hot oxalic acid aqueous solution, and then a well-stirred coating solution with the following composition: R _u Cl ₃・3H ₂ O 8.4 g butyl titanate 36.8 g butyl alcohol 76.0 g concentrated HCl 10 ml was applied with a brush and dried. death,
Next, thermal decomposition was performed at 500°C for 1 minute in the atmosphere.
This operation was repeated four times to form the first coating layer. When this first coating layer was observed under an electron microscope, cracks in the form of cracks were observed on the surface, but it was smooth and no porous structure was observed. Next, a coating solution consisting of the following composition: 16.7 g of PdCl ₂ 200 ml of butyl alcohol and 10 ml of concentrated hydrochloric acid was applied onto the first coating layer using a brush, and after drying, the coating solution was heated in the air at 600°C for 10 minutes. The second coating layer was formed by repeating the process five times. As a result, an oxide layer of 0.29 mg/cm ² of ruthenium oxide in terms of ruthenium metal and 0.46 mg/cm ² of titanium oxide in terms of titanium metal is formed on the titanium substrate as the first coating layer. An "electrode D" having palladium oxide of 0.24 mg/cm ² in terms of palladium metal was obtained as a coating layer. Note that the amount of ruthenium and the amount of palladium were determined by fluorescent X-ray method, and the amount of titanium was calculated from the amount of ruthenium and the component ratio of the solution. Comparative Example 4 According to the method described in Example 1 of JP-A-52-68076, an electrode was produced as follows. Titanium plate equivalent to JIS class 2 ( ^t 1 x ^w 20 x ^l 20mm)
was washed with a hot oxalic acid aqueous solution, and then a well-stirred coating solution with the following composition: 20 g of H ₂ PtCl _{6.6H 2} O and 150 g of butyl alcohol was applied with a brush, dried, and then heated to 500°C in air. Heat for 10 minutes at
This operation was repeated four times to form the first coating layer. When this first coating layer was observed under an electron microscope, although some cracks were observed on the surface, it was smooth overall and no porous structure was observed. Next, on the first coating layer, a well-stirred coating solution consisting of the following composition: PdCl ₂ 0.074 g SuCl _{4.5H 2} O 2.822 g butyl alcohol 20 ml concentrated HCl 2 ml was applied with a brush, and a drying room was prepared. A second coating layer was formed by heating at 600° C. for 10 minutes in air and repeating this operation five times. As a result, "Electrode E" was created, which had approximately 0.20 mg/cm ² of platinum as the first coating layer on a titanium substrate, and palladium oxide and tin of 0.01 mg/cm ² in terms of palladium as the second coating layer. I got it. Electrolytic test (1) Test conditions After electrolyzing a sodium chloride aqueous solution under the conditions described below using electrodes A to E prepared in Example 6 and Comparative Examples 1 to 4, the chlorine overvoltage was measured. Summer. Electrolyte: 200g/NaCl aqueous solution Temperature: 45℃ Electrode size: 1mm x 20mm x 20mm Distance between electrodes: 20mm Cathode: Platinum Current density: 100A/dm ² (2) Results

[Table] As mentioned above, the electrode manufactured by the method of the present invention has a porous platinum metal coating layer as a skeleton component,
At least one metal oxide selected from ruthenium oxide, palladium oxide, and iridium oxide is supported on this in a three-dimensional manner by a thermal decomposition method, and it is a composite of a porous platinum metal coating layer and a metal oxide. The bonding strength between the platinum metal coating layer and the above-mentioned metal oxide supported on the platinum metal coating layer is also high, so it does not separate or fall off, and it also has excellent chemical corrosion resistance. There is an advantage of being there. Furthermore, although the electrode manufactured by the method of the present invention is coated with platinum metal, unlike conventional platinum metal-coated electrodes, the electrode coated with platinum metal remains stable during electrolysis until the electrode coating is almost consumed. The economical increase in overvoltage is extremely small, and the electrode life can be significantly extended. For example, the electrode life can be several to several hundred times longer than conventional electrodes coated only with platinum metal or metal oxide. can have Moreover, in the electrode manufactured by the method of the present invention, the amount of metal oxide consumed is small, and is less than a fraction to a few hundredths of the amount of consumption of an electrode that supports only a metal oxide. This is a low value, and the amount of consumption of the platinum metal coating layer is also small, making it extremely economical.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are graphs showing the results of an experiment to measure the electrode potential of the electrode for electrolysis produced in the example.

Claims (1)

[Claims] 1 At least a portion of the surface of the corrosion-resistant conductive substrate,
(a) A porous platinum layer is formed by electroplating, and (b) a solution of at least one metal compound capable of producing a metal oxide selected from ruthenium oxide, palladium oxide, and iridium oxide by thermal decomposition. is infiltrated into the porous platinum, the metal compound is converted into a metal oxide by heating, and the above operations (a) and (b) are repeated as necessary. Method for manufacturing electrodes for electrolysis.