JPH04210488A - Electrolytic electrode - Google Patents

Abstract

PURPOSE:To prolong the service life of an electrolytic electrode and to highly efficiently generate chlorine even under the conditions where the available chlorine content is high by coating a titanium base body with a porous alloy layer and an oxide layer consisting essentially of a rhodium oxide layer and a palladium oxide layer. CONSTITUTION:A thin titanium hydride layer is formed on the surface of an electrode base body consisting of titanium and a titanium-based alloy, and a porous platinum coating layer having 8-19 g/cm<3> apparent density is provided thereon. A rhodium compd. soln. is then applied and heat-treated in an oxygen- contg. atmosphere to form a rhodium oxide layer on the platinum coating layer. A soln. contg. a palladium compd. and a rhodium compd., if necessary, is applied on the rhodium oxide layer and heat-treated to form an oxide coating layer contg. 80-100mol% palladium oxide and 0-20 mol% rhodium oxide on the rhodium oxide layer, and an electrolytic electrode is obtained. This electrode is advantageously used as an electrolytic anode for a dil. aq. chloride soln. such as brine and seawater.

Description

[Detailed description of the invention]

[0001] The present invention relates to a novel electrode for electrolysis, and more specifically, an electrode for electrolysis useful as an anode when generating chlorine at the anode by electrolyzing a dilute aqueous chloride solution such as seawater or saline, and a method for manufacturing the same. Regarding. [0002] Chlorine is generated at the anode by electrolyzing a dilute aqueous chloride solution of seawater or salt water, and the sterilizing properties of hypochlorite ions produced by the reaction between this chlorine and hydroxide ions are utilized by using a bleaching blade. , for example, preventing the attachment of living things to underwater structures.
It is well known that water treatment for swimming pools, water and sewage systems, etc. is performed. When saline is used as the electrolytic solution, the effective chlorine concentration at the outlet of the electrolytic cell is usually around 110,000 pp in order to increase the utilization rate of the saline. [0003] Conventionally, platinum-coated titanium electrodes, platinum-iridium-coated electrodes, platinum-palladium oxide-coated electrodes, and ruthenium oxide-titanium oxide coating layer 1 have been known as anode materials for electrolysis of diluted chloride aqueous solutions. However, these have drawbacks such as low current efficiency and/or lack of sustainability in the electrolytic solution, and high electrode wear. [00043 The present inventors have completed the present invention as a result of intensive research to develop an electrode for electrolysis without the above-mentioned drawbacks. [0005] That is, the present invention provides: (a) an electrode base made of titanium or a titanium-based alloy; and (b) an electrode base provided on the surface of the electrode base via a titanium oxide layer with an apparent density of 8 to 1.9 g/ (c) a rhodium oxide layer covering the surface of the porous platinum coating layer; (d) 80 to 100 mol% palladium oxide and 0 to 20 mol% rhodium oxide. The present invention provides an electrode for electrolysis characterized by comprising an oxide coating layer containing. [0006] According to the present invention, the electrode for electrolysis of the present invention has an apparent density of 8 to 8 on a polar substrate made of titanium or a titanium-based alloy with a thin titanium hydride layer formed on the surface. After providing a porous platinum coating layer within the range of 19 g/cm3 and firing in an oxygen-containing atmosphere if necessary, (i
i) A solution of a rhodium compound that thermally decomposes to produce rhodium oxide in an oxygen-containing atmosphere is applied to the surface of the porous platinum coating layer, and then heat-treated in an oxygen-containing atmosphere to form a rhodium compound on the platinum coating layer. Form a rhodium oxide layer and (t t
i) Further, after applying a solution containing a palladium compound that can thermally decompose in an oxygen-containing atmosphere to produce palladium oxide and optionally a rhodium compound that can thermally decompose in an oxygen-containing atmosphere to produce rhodium oxide, It can be manufactured by heat-treating in an oxygen-containing atmosphere to form an oxide layer containing palladium oxide and optionally rhodium oxide on the rhodium oxide layer. [00073] Hereinafter, the electrode for electrolysis of the present invention will be explained in more detail based on its manufacturing method. [00081 The material of the electrode substrate used in the present invention includes titanium or a titanium-based alloy. As the titanium-based alloy, a corrosion-resistant and conductive alloy mainly composed of titanium is used, such as Ti-Ta-Nb,
Ti-Pd, Ti-Zr, Ti-W,
Examples include Ti-based alloys, which are usually used as electrode materials and consist of combinations such as T1-A1. [0009] These electrode materials are plate-shaped, perforated plate-shaped, rod-shaped,
It can be processed into a desired shape such as a mesh plate and used as an electrode base material. [001ON] It is desirable that the electrode substrate as described above be pretreated in advance and then provided with an intermediate layer, as is usually done. Preferred specific examples of such pretreatment include those described below. [00111 First, the surface of the electrode substrate (hereinafter sometimes referred to as titanium substrate) made of titanium or titanium alloy described above is washed with, for example, 1-lichloroethylene, trichloroethane, etc., or electrolyzed in an alkaline solution. After degreasing with hydrogen fluoride, the surface of the titanium substrate is oxidized by treatment with hydrofluoric acid or a mixed acid of hydrofluoric acid and other acids such as nitric acid and sulfuric acid with a hydrogen fluoride concentration of about 1 to about 20% by weight. The film is removed and the surface of titanium grain boundaries is roughened. The acid treatment can be carried out at a temperature of room temperature to about 40° C. for several minutes to more than ten minutes depending on the surface condition of the titanium substrate. Incidentally, in order to sufficiently roughen the surface, blasting treatment may be used in combination. [0012] The surface of the titanium substrate thus acid-treated is brought into contact with concentrated sulfuric acid to roughen the inner surface of the titanium grain boundaries into protrusions and to form a thin layer of titanium hydride on the surface of the titanium substrate. Form. [0013] The concentrated sulfuric acid used is generally 40 to 80 M%
, preferably at a particle size of 50 to 60% by weight. If necessary, a small amount of sodium sulfate or other sulfate may be added to this concentrated sulfuric acid for the purpose of stabilizing the treatment. The contact with the concentrated sulfuric acid can usually be carried out by immersing the titanium substrate in a bath of concentrated sulfuric acid, and the bath temperature at that time is generally in the range of about 100 to about 150°C, preferably about 110 to about 130°C. The temperature within can be
Further, the immersion time is usually 0.5 to about 10 minutes, preferably about 1 to about 3 minutes. This sulfuric acid treatment makes it possible to roughen the inner surface of the titanium crystal grain boundaries into fine protrusions and form a very thin titanium hydride film on the surface of the titanium substrate. [0014] The sulfuric acid-treated titanium substrate is removed from the sulfuric acid bath and rapidly cooled, preferably in an inert gas atmosphere such as nitrogen or argon, to reduce the surface temperature of the titanium substrate to about 60° C. or less. It is appropriate to use a large amount of cold water for this rapid cooling, which also serves as washing. [0015] The titanium substrate on which a very thin titanium hydride film has been formed is treated by immersion in dilute hydrofluoric acid or dilute fluoride aqueous solution (for example, sodium fluoride, potassium fluoride, etc.) to remove the hydrogen. The titanium oxide film is grown to even out and stabilize the film. The concentration of hydrogen fluoride in the dilute hydrofluoric acid or fluoride aqueous solution that can be used here can generally be in the range of 0.05 to 3% by weight, preferably 0.3 to 1% by weight, and The temperature during the immersion treatment with these solutions is generally in the range of 10 to 40°C, preferably 20 to 30°C. This treatment can be carried out until a uniform titanium hydride film having a thickness of usually 0.5 to 10 microns, preferably 1 to 3 microns, is formed on the surface of the titanium substrate. This titanium hydride (TiHy, where y is a number from 1.5 to 2) exhibits a grayish brown to blackish brown color depending on the degree of hydrogenation, so a titanium hydride film with a thickness within the above range is formed. It is possible to empirically control the change in color tone of the substrate surface by contrasting the brightness with a standard color source. [0016] The titanium substrate whose surface was roughened in this way and a titanium hydride film was formed,
After appropriate treatments such as washing with water, the surface is coated with a porous platinum layer. [00173] Coating with this porous platinum layer can normally be carried out by electroplating. The composition of the plating bath that can be used in this electroplating method is, for example, H2Pt.
C16, <NH4) 2P t Cl 6, K= P
t CI6, Pt(NHl):! (A platinum compound such as NO2h is dissolved in a sulfuric acid solution (pH 4 to 3) or an aqueous ammonia solution to a concentration of about 2 to about 20 g/l in terms of platinum, and if necessary, sulfuric acid is added to stabilize the bath.) Examples include acidic or alkaline plating baths to which small amounts of sodium (for acidic baths), sodium sulfite, sodium sulfate (for alkaline baths) are added.Platinum electroplating using plating baths with such compositions can be applied to titanium substrates. In order to suppress the decomposition of the titanium hydride film formed on the surface as much as possible, it is desirable to use a high-speed plating method such as so-called strike plating at a relatively low temperature within the range of about 30 to about 60°C. [0018] A porous platinum coating layer can be formed on the hydrogenated titanium film of the titanium substrate by electroplating.The apparent density of the platinum coating layer at that time is 8 to 19.
g/crti3, preferably 12-18 g/CIall
It is appropriate that the value be within the range of . If the apparent density of the porous coating layer is less than 8 g/cm 3 , the bonding strength of platinum decreases and it becomes easy to peel off, whereas if it exceeds 19 g/cm 3 , it becomes difficult to stably support palladium oxide, which will be described later. The apparent density of the platinum coating layer can be controlled, for example, by empirically adjusting the bath composition and/or plating conditions (current density, current waveform, etc.) of the platinum plating bath. [0019N Note that if it is desired to obtain a platinum metal coating layer with higher porosity, the porous state can be further increased by a chemical or electrochemical method after forming the porous platinum metal layer. [00201 Furthermore, in the electroplating of platinum, the coating amount of platinum on the substrate is usually at least 0.2 mg/cm2.
Continue until above. Platinum coating amount is 0.2mg/
If it is less than cm 2 , the oxidation of the titanium hydride film portion will proceed too much during the firing process described below, and the conductivity will tend to decrease. Although there is no particular upper limit to the amount of platinum coated, if the amount is increased more than necessary, the corresponding effect will not be obtained and it will be rather uneconomical, so a coating amount of 5 mg/cm2 or less is usually sufficient. The preferred coating amount of platinum is 1 to 3 m.
g/C [112. [00211 Here, the amount of platinum covered in the porous platinum coating layer is the amount determined as follows using fluorescent X-ray analysis. That is, platinum plating is applied to various thicknesses by the method described above on a titanium substrate pretreated as described above,
Quantify the amount of plating using wet analysis and fluorescent X-ray analysis, plot the analytical values from both methods on a graph to create a standard calibration curve, and then subject the actual sample to fluorescent X-ray analysis. Calculate the amount of platinum coating from the value and standard calibration curve. [0022] Also, the apparent density of the platinum coating layer (δg/cm
3) is the platinum coating amount (0g7c) determined as above.
m3) and the thickness (tem) of the platinum coating layer determined by cross-sectional microscopic observation of the sample, as δ=ω/l. [0023] The titanium substrate provided with the porous platinum coating layer is then fired in the air to thermally decompose the titanium hydride film layer below the platinum coating layer, and the titanium hydride film layer under the platinum coating layer is thermally decomposed. Substantially most of the titanium hydride can be returned to titanium metal, and further, the titanium near the boundary with the platinum coating layer can be changed to titanium oxide in a low oxidation state. This firing is generally from about 300°C to about 600°C, preferably from about 300°C to about 4°C.
This can be done by heating at a temperature of 00°C for about 10 minutes to 4 hours. [0024] As a result, a very thin conductive titanium oxide layer is formed on the surface of the titanium substrate. The thickness of this titanium oxide layer is generally 100 to 1,000, preferably 200 to 1,000.
The composition of titanium oxide is preferably within the range of 600 A, and the composition of titanium oxide is generally such that X is 1 < x <
2, particularly preferably in the range 1, 9 < x < 2. [0025] Alternatively, the platinum dispersion coated titanium substrate may be directly subjected to the drilling process without being subjected to the firing process as described above. In this case, during the thermal decomposition treatment in the next step, the titanium hydride film layer on the surface of the titanium substrate is converted into titanium metal and titanium oxide in a low oxidation state. [00261 The surface of the porous platinum coating thus formed on the titanium substrate is then coated with a rhodium oxide layer. [0027] Formation of the acid rhodium oxide coating may include, for example,
A solution containing a rhodium compound that thermally decomposes in an oxygen-containing atmosphere, preferably air, to form rhodium oxide is applied onto the porous platinum coating layer, allowed to penetrate, and after drying as appropriate, heat treatment in an oxygen-containing atmosphere. This can be done by doing. Examples of the rhodium compound that can be used here include rhodium nitrate, rhodium chloride, etc., but rhodium nitrate is generally preferred. (0028) The rhodium compound solution is -
Generally, a solution of a rhodium compound in a lower alcohol (eg, methanol, ethanol, etc.) is suitable. If the rhodium compound is difficult to dissolve in lower alcohols, a solution of the rhodium compound can be prepared by first dissolving the rhodium compound in an aqueous solution of an acid such as nitric acid or hydrochloric acid, and then mixing it with the lower alcohol. The concentration of the rhodium compound in the solution is usually 5 to 100 g/l, particularly 10 to 50 g/l, which easily penetrates into the porous platinum layer in terms of rhodium metal.
It is convenient within the range of l. [002930 The application of the dium compound can be carried out by conventional methods such as brushing, spraying, dipping and the like. At this time, in order to promote penetration of the applied solution into the pores of the porous platinum coating layer, high-frequency vibration may be applied to the substrate depending on the case. [00301 The substrate having the porous platinum coated surface coated with the solution of the rhodium compound is optionally dried at a temperature within the range of about 20 to about 150°C and then fired in an oxygen-containing gas atmosphere, such as air. Firing is generally carried out in a suitable heating furnace, such as an electric furnace, a gas furnace, an infrared furnace, etc.
This can be done by heating to a temperature in the range of about 650<0>C, preferably from about 550<0>C to about 600<0>C. The heating time is approximately 3 minutes or more depending on the size of the substrate to be fired.
It can be about 30 minutes. [00311] By this firing, a rhodium oxide coating layer is formed on the surface of the porous platinum coating layer (inner and/or outer surface of the pores), and at the same time, a thin layer of titanium oxide under the platinum coating layer grows. [0032] The coating amount of rhodium oxide does not need to be enough to completely cover the entire surface of the porous platinum coating layer, and is generally 0.1 to 2 mg/cn in terms of rhodium metal.
12, preferably 0, 2-0, 7 mg/cm2
It is convenient to be within the range of . [0033] The surface of the titanium substrate on which the rhodium oxide layer has been formed on the surface of the porous platinum coating layer is further coated with an oxide layer mainly consisting of palladium oxide. [0034] The formation of such an oxide layer is usually carried out by applying a solution containing a palladium compound that can be thermally decomposed to produce palladium oxide in an oxygen-containing gas atmosphere, drying as appropriate, and then applying the solution in an oxygen-containing gas atmosphere. This can be done by heat treatment. Examples of the palladium compound used here include palladium nitrate, palladium chloride, palladium acetate, palladium abietate, dinitrodiammine palladium, and the like, among which palladium nitrate and dinitrodiammine palladium are preferred. [0035] As a solution containing such a palladium compound, a lower alcohol solution such as methanol or ethanol is particularly suitable. However, if the palladium compound to be used is sparingly soluble in lower alcohols, it may be prepared in advance in an aqueous solution of an acid such as nitric acid or hydrochloric acid. A solution containing a palladium compound may be prepared by dissolving the palladium compound in a solution and then mixing it with a lower alcohol. The concentration of the palladium compound in the solution is usually 5 to 100 g/l, especially 10 g/l, which easily penetrates the porous platinum coating layer provided with the rhodium oxide coating layer in terms of palladium metal.
A range of 50 g/l is suitable. [0036] Furthermore, a rhodium compound as described above can be added to the solution. The durability of the electrode formed thereby can be further improved. The amount of rhodium compound used is 20 mol% or less, preferably 2 to 1 mol% of rhodium oxide, based on the total amount of palladium oxide and rhodium oxide in the oxide layer formed using the solution.
The amount can be set within the range of 0 mol%. [0037] Formation of an oxide coating layer mainly consisting of palladium oxide from a solution containing a palladium compound and optionally a rhodium compound prepared as described above (
Coating, drying, and firing of the solution can be performed in the same manner as described above for forming the rhodium oxide layer. [0038] As a result, palladium oxide 80 to 1
An oxide coating layer containing 0.00 mol%, preferably 90-98 mol% and rhodium oxide 0-20 mol%, preferably 2-10 mol% can be provided. [0039] The coating layer of palladium oxide in the oxide layer is generally 0.05 to 2 m in terms of palladium metal.
g/cm", preferably within the range of 0.4 to 1.5 mg/cm". Moreover, the coating layer of rhodium oxide in the oxide layer is usually 0 to 0.0 in terms of rhodium metal.
5 mg/cm2, particularly within the range of 0.01 to 0.4 mg/cm'. [00401 In this specification, rhodium oxide (rhodium equivalent) and palladium oxide ( The coating amount of platinum (converted to platinum) is a value determined as follows using fluorescent X-ray analysis in the same manner as in the case of platinum. [0041ff That is, various amounts of each oxide were supported on the titanium substrate pretreated as described above using the method described above, and the amounts were quantified by wet analysis and fluorescent X-ray analysis, and analyzed by both methods. The values are plotted on a graph to create a standard calibration curve, and then the actual sample is subjected to fluorescent X-ray analysis, and each coating amount is determined from the analytical values and the calibration curve. [00421 The electrode of the present invention has at least three coating layers of a porous platinum layer, a rhodium oxide layer, and an oxide layer mainly composed of palladium oxide on a substrate made of titanium or a titanium-based alloy described above, It has a long electrode life and excellent durability, and also shows high chlorine generation efficiency even under conditions of high concentration of available chlorine, making it advantageous for use as an electrode for electrolysis of dilute chloride aqueous solutions such as salt water and seawater. I can do it. [00431 Next, the present invention will be explained in more detail with reference to Examples. [00441

[Example] Example I J Titanium plate material equivalent to type 32 (to5xwlOX
1+omIn) was degreased and washed with trichlorethylene, then treated with an 8 wt% aqueous HF solution at 20°C for 2 minutes, and then treated with a 60 wt% H2SO4 solution at 120°C for 3 minutes. The titanium substrate was then removed from the sulfuric acid solution and quenched by spraying with cold water in a nitrogen atmosphere. Furthermore, 0.3 at 20℃
%wt% HF aqueous solution for 2 minutes and then washed with water. (OO45) After washing with water P t (NH3h (NO2)2
was dissolved in a sulfuric acid solution with a PT content of 5 g/l and a pH of 2.
30mA/c in a Pt plating bath adjusted to 50℃
After plating for about 6 minutes at m2, the apparent density was 16g/
A porous platinum coating layer with an electrodeposition amount of 1-7 mg/cm2 was formed on a titanium substrate. [0046] The titanium substrate provided with the porous platinum coating layer in this manner was heat treated in the atmosphere at 400° C. for 1 hour. [0047] Next, a rhodium nitrate aqueous solution adjusted to a rhodium concentration of 50 g/l (metal equivalent) and a nitric acid concentration of 95 g/l was mixed with ethanol, and a rhodium concentration of 25 g was obtained.
A coating solution containing /l (metal equivalent) was prepared. This coating solution was weighed at 2.7 μl per 1 cm2 onto Myflopivera 1, applied to the substrate and permeated into the porous platinum coating layer, dried under reduced pressure at room temperature for 30 minutes, and further in the air at 600°C. It was baked for 10 minutes. This coating-drying-firing process was repeated five times to form a rhodium oxide layer of 0.4 mg/cm 2 in terms of rhodium on the surface of the porous platinum coating layer. [00481 Next, a palladium nitrate aqueous solution adjusted to a palladium concentration of 100 g/l (metal equivalent) and a nitric acid concentration of 445 g/l was mixed with ethanol to give a palladium concentration of 2.
A solution containing 5 g/l (metal equivalent) was prepared, and a rhodium concentration of 50 g/l (metal equivalent) and a nitric acid concentration of 95
g/l of an aqueous rhodium nitrate solution is added and mixed to prepare a coating solution containing palladium nitrate and rhodium nitrate with a molar ratio of palladium to rhodium (metal equivalent) of 20:1. Using this coating solution, the same coating-drying-baking process as described above was repeated 8 times to obtain a coating of 0.6 m/Icm2 in terms of metal.
An oxide coating layer containing g of palladium oxide and 0.03 mg of rhodium oxide was formed. Thus, the example electrode-
1 was produced. For comparison, Comparative Example Electrode-1 was prepared by coating platinum on a titanium substrate in the same manner as in Example-1 above. [00491 FIG. 1 shows the relationship between the effective chlorine concentration and the chlorine generation efficiency when the electrode thus obtained was electrolyzed under the following conditions. [00501 Electrolyte: 3% NaCl Current density: t 5 A/dm2 Counter electrode: Ti From FIG. 1, it can be seen that Example Electrode-1 is an electrode with high chlorine generation efficiency even under a high concentration of available chlorine. [005L] Example 2 A titanium plate was pretreated in the same manner as described in Example 1 above. [00521 Then P t (NH3)2 (NO2
)2 in an ammonia aqueous solution with a pH≠9 containing 10 g/l in terms of Pt, in a Pt plating bath in which thorium nitrite and ammonium nitrate were added at concentrations of 5 g/l and 20 g/l, respectively, at 90°C and 15 mA/cm2. for about 14 minutes
After T-plating, a porous platinum coating layer with an apparent density of 14 g/cm3 and a charge capacity of 2.3 mg/C1112 was formed on the titanium plate by treatment with a mixed aqueous solution of hydrochloric acid and nitric acid. . [00531 Next, a rhodium nitrate aqueous solution adjusted to a rhodium concentration of 50 g/l (metal equivalent) and a nitric acid concentration of 95 g/l was mixed with ethanol, and a rhodium concentration of 25 g/l was mixed.
A coating solution containing /l (metal equivalent) was prepared. This coating solution was weighed at 2.71 zl per 1 cm2 with a micropipette, applied to the substrate, and allowed to penetrate into the porous platinum coating layer, then dried under reduced pressure at room temperature for 30 minutes, and further heated at 600°C.
It was fired for 10 minutes in an atmosphere of By repeating this coating-drying-firing process five times, a rhodium oxide coating layer of 0.4 mg per 1 cm (rhodium equivalent) was formed on the surface of the porous platinum coating layer. In order to support palladium oxide on the porous platinum coating layer, the palladium concentration was 100 g/l (metal equivalent) and the nitric acid concentration was
A palladium nitrate aqueous solution adjusted to 145 g/l and ethanol were mixed to prepare a coating liquid containing a palladium concentration of 25 g/l (metal equivalent), and then this coating liquid was used for coating, drying, and baking in the same manner as above. The process was repeated eight times to form an oxide coating layer of 0.6 mg per Icm2 in terms of palladium. In this way, Example electrode-2 was created. (0.6 mmg supported per 1 cm2 in terms of Pd metal)
For comparison, Comparative Example Electrode-2 was produced in the same manner as Example Electrode-2 except that the intermediate rhodium oxide layer was omitted. FIG. 2 shows the consumption rate of palladium oxide when the '@ electrode thus obtained was electrolyzed under the following conditions. [0056] Electrolyte: 6% NaC1 Current density near 5A/dm' Counter electrode: 1゛i [0057]

[0058] From FIG. 2, it can be seen that Example Electrode-2 has less palladium oxide consumption and is superior in durability than Comparative Example Electrode 2.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between effective chlorine concentration and chlorine generation efficiency during electrolysis of Example Electrode-1 and Comparative Example Electrode-1 produced in Example 1.

FIG. 2 is a graph showing the consumption rate of palladium oxide during electrolysis of Example @ Electrode-2 prepared in Example 2 and Comparative Example Electrode-2.

[Figure 2]

Claims (2)

[Claims] Claim 1: (a) an electrode base made of titanium or a titanium-based alloy; (b) provided on the surface of the electrode base via a titanium oxide layer with an apparent density within the range of 8 to 19 g/cm^3; (c) a rhodium oxide layer covering the surface of the porous platinum coating layer; and (d) an oxide containing 80 to 100 mol% of palladium oxide and 0 to 20 mol% of rhodium oxide. An electrode for electrolysis characterized by comprising a material coating layer. (i) A porous platinum coating having an apparent density within the range of 8 to 19 g/cm^2 on an electrode base made of titanium or titanium-based alloy with a thin titanium hydride layer formed on the surface. (ii) after coating the surface of the porous platinum coating layer with a solution of a rhodium compound that can be thermally decomposed to produce rhodium oxide in an oxygen-containing atmosphere; , heat treated in an oxygen-containing atmosphere,
forming a rhodium oxide layer on the platinum coating layer; (iii) further comprising a palladium compound that can be thermally decomposed in an oxygen-containing atmosphere to produce palladium oxide; After applying a solution containing a rhodium compound that can be generated, heat treatment is performed in an oxygen-containing atmosphere to form an oxide layer containing palladium oxide and optionally rhodium oxide on the rhodium oxide layer. A method for manufacturing an electrode for electrolysis according to claim 1.