MX2014007762A

MX2014007762A - Anode for oxygen generation and manufacturing method for the same.

Info

Publication number: MX2014007762A
Application number: MX2014007762A
Authority: MX
Inventors: Yi Cao; Akihiro Kato; Kazuhiro Hirao; Takashi Furusawa
Original assignee: Industrie De Nora Spa
Priority date: 2011-12-26
Filing date: 2012-12-25
Publication date: 2014-09-15
Also published as: WO2013100165A3; CA2859941A1; KR20140101423A; PE20150086A1; US20140353148A1; AU2012361469A1; CN104011263A; CL2014001718A1; WO2013100165A2; JP5686457B2; PH12014501347B1; JP2014526609A; TW201337041A; PH12014501347A1

Abstract

The present invention aims to provide an anode for oxygen generation and a manufacturing method for the same used for industrial electrolyses including manufacturing of electrolytic metal foils such as electrolytic copper foil, aluminum liquid contact and continuously electrogalvanized steel plate, and metal extraction. The present invention features an anode for oxygen generation and a manufacturing method for the same comprising a conductive metal substrate and a catalyst layer containing iridium oxide formed on the conductive metal substrate wherein the coating is baked in a low temperature region of 370Â°C - 400Â°C in an oxidation atmosphere to form the catalyst layer containing amorphous iridium oxide and the catalyst layer containing amorphous iridium oxide is post-baked in a further high temperature region of 520Â°C - 600Â°C in an oxidation atmosphere to crystallize almost all amount of iridium oxide in the catalyst layer.

Description

ANODE FOR THE GENERATION OF OXYGEN AND PROCEDURE OF MANUFACTURE OF THE SAME Field of the Invention The present invention relates to an anode for the generation of oxygen used for various industrial electrolysis and to a manufacturing process thereof; in more detail, it relates to a durable anode with a high charge for the generation of oxygen and a manufacturing process for it, used for industrial electrolysis including the manufacture of electrolytic metallized papers such as electrolytic copper metallized paper, liquid contact aluminum and electrogalvanized steel plate continuously, and metal extraction.

Background of the Invention The mixture of lead ions in electrolytic cells is often observed in several types of industrial electrolysis. The mixture of lead compounds in the production of electrolytic copper metallized paper as a typical example proceeds from the following two points: that is, adhesion, in the form of lead alloy, to scrap copper which is one of the sulphate raw materials of copper in the electrolyte, and before the use of a type of DSE electrode (registered trade name of Permelec Electrode Ltd.), lead-antimony electrodes were used, so that in this case the lead leach ions led to particles of lead sulfate and a residue in the electrolytic cell.

High purity electrolytic copper is the best material premium, but in practice, scrap copper is often used as a recycled product. The copper raw material undergoes leaching in the form of copper ion through the use of concentrated sulfuric acid as the immersion liquid, or the copper raw material is forcibly eluted as an anode for a short period of time. In an anodic solution, the elution is simple from the morphology of the complex of the coating metals and other metal parts. In scrap copper, the adhesion of waxy materials such as lead solder material is produced, and other metals present in the waxy materials are eluted together with the elution of the copper in the sulfuric acid-copper electrolyte, or mixed in shape of floating particles. A coating of water-insoluble lead sulphate is formed on the surface of the metallic lead, and in this way the lead ion has a high resistance to corrosion caused by sulfuric acid, but a small amount of it dissolves in sulfuric acid concentrate, and said lead ion crystallizes in the form of a tiny particle of lead sulfate in the electrolyte and floats under conditions of lower temperature than that of the solution and under conditions of high pH.

Furthermore, lead sulfate, PbS04, is a water-insoluble salt in which the solubility product is 1.06 x 10 ~ 8 mol / l (18 ° C) and is extremely small, being the solubility in sulfuric acid of 10% and 25 ° C of about 7 mg / 1.

By chance, the copper potential of standard electrode is high after the precious metal (Cu2 + + 2e ~ -> Cu: + 0.342V versus SHE) and the potential difference in Comparison with a base metal such as lead and etc. is large (Pb2 + + 2e ~? Pb: -0.126V versus SHE) and the copper overvoltage in the electrodeposition is also low, there is no hydrogen evolution and eutectoid is formed with other base metals. This is the reason why scrap copper is used as raw material.

However, the influence of fine floating particles such as lead ion, Pb2 + or lead compounds, PbS04 versus an electrode for electrolysis and electrolytic copper paper which is an electrolytic product can not be highlighted.

Specifically, in an electrode for electrolysis (anode), if electrolysis takes place, the lead ion, Pb2 +, is oxidized to lead ~ -Pb02 in acid solution, and is electrodeposited on a surface of the electrode catalyst (anode) (Pb2 + / Pb02: pH = almost 0, E0 approximately 1.47 V compared to SHE) (exactly 1,459 + 0.0295p (Pb2 +) - 0.1882 pH). Because lead-p-Pb02 has a small function of electrode catalyst, a total electrode surface is covered by it, although the electrode potential increases, electrolysis takes place continuously and life is extended of the electrode as a coating to protect the electrode, but if partial desquamation occurs, a catalyst layer of the original electrode whose activity is high is exposed, therefore, the electrolysis current of the electrode increases and a lack of uniformity in the electrode is generated. as to the thickness of copper metallized paper that develops on the opposite cathode drum.

In this way, electrolysis is stopped and an electrode is still immersed in the electrolyte, the lead oxide is easily reduced to lead sulphate, PbS0, which has no catalyst activity so as to correspond to the oxidation reaction of a release trace of oxygen by means of the action of the local battery (PbS04 + 2H20 = Pb02 + HS04"+ 3H + + 2e": at pH = almost 0, E0 = approximately 1.62V vs SHE) (exactly 1.632 -0, 0886 pH - 0, 0295p (HS04 ~)), so that the problem arises that the electrolysis voltage increases after electrolysis.

In the same way, the following problem occurs: the fine particles of PbS0 floating in the electrolyte adhere to the surface of the electrolytic foil and become entangled in a roll of electrolytic copper foil.

In recent years, from the environmental point of view, in all aspects of the raw materials of electrolyte, equipment and waste materials, etc., awareness of materials that do not contain lead is increasing. However, after the lead-free solder has penetrated, there is a period of time to replace the scrap copper from the lead-free part and, from the cost point of view, it can be predicted that the coexistence with the ion Lead continues for a moment. Therefore, for the electrolysis electrode, it is necessary to reduce the influence of the lead ion, such as the previous one, insofar as it is possible.

Also, as an electrode for this type of electrolysis, together with the reduction of the influence of lead ion As much as possible, an electrode with a low oxygen generation potential and a long service life is required. Conventionally, as an electrode of this type, an insoluble electrode comprising a conductive metallic substrate, such as titanium, covered with a catalyst layer containing a precious metal or a precious metal oxide has been applied. For example, PTL 1 discloses an insoluble electrode prepared in such a way that a layer of catalyst containing iridium oxide and a valve metal oxide is coated on a conductive metallic substrate, such as titanium, heated in an oxidizing atmosphere and calcined to a temperature of 650-850 ° C, to partly crystallize the valve metal oxide. However, this electrode has the following drawbacks. Because the electrode is calcined at a temperature of 650 ° C or more, the metal substrate, such as titanium, causes interfacial corrosion and becomes a poor conductor, causing the oxygen overvoltage to increase to a value that leaves the electrode outside. of service. In addition, the diameter of the iridium oxide crystals in the catalyst layer increases, resulting in a lower effective surface area of the catalyst layer on the electrode, which leads to poor catalytic activity.

The document PTL 2 discloses the use of an anode for the copper metallization and the manufacture of metallized copper paper, prepared in such a way that a catalyst layer comprising amorphous iridium oxide and amorphous tantalum oxide is provided, in the form of mixing, on a conductive metallic substrate, such as titanium. However, this electrode is characterized by amorphous iridium oxide, and it is insufficient in terms of durability of the electrode. The reason why the durability decreases when amorphous iridium oxide is applied is that the amorphous iridium oxide shows an unstable union between iridium and oxygen, in comparison with the crystalline iridium oxide.

The PTL 3 document discloses an electrode coated with a catalyst layer comprising a double layer structure by means of a lower layer of crystalline iridium oxide and a top layer of amorphous iridium oxide, in order to avoid consumption of the catalyst layer and improve the durability of the electrode. The electrode disclosed by PTL3 is insufficient in terms of durability of the electrode, since the upper layer of the catalyst layer is amorphous iridium oxide. In addition, the crystalline iridium oxide exists only in the lower layer, is not distributed evenly throughout the catalyst layer, resulting in insufficient electrode durability.

The document PTL 4 discloses an anode for the electrolytic extraction of zinc, wherein a layer of catalyst containing amorphous iridium oxide is provided as a prerequisite and crystalline iridium oxide, in the mixed state, on a conductive metallic substrate such as titanium. The document PTL 5 discloses an anode for the electrolytic extraction of cobalt, wherein a layer of catalyst containing amorphous iridium oxide is provided as a prerequisite and crystalline iridium oxide, in the mixed state, on a conductive metallic substrate such as titanium. However, it is thought that the durability of these two electrodes is not enough, because they contain a large Amount of amorphous iridium oxide, as a prerequisite.

List of Appointments Patent bibliography PTL 1: JP2002 -275697A (JP3654204B) PTL 2: JP2004 -238697A (JP3914162B) PTL 3: JP2007 -146215A PTL 4: JP2009 -2931177A (JP4516617B PTL 5: JP2010 -001556A (JP4516618B) Summary of the Invention In order to solve the aforementioned problems, the present invention aims to provide an anode for the generation of oxygen and a manufacturing process for it, which can reduce the oxygen surplus of the anode for the release of oxygen, for its use in the production an electrode for industrial electrolysis in order to coat the electrolysis active substance layer, in particular the electrolytic copper metallized paper, and extract the metal by means of the electrolytic process and control adhesion, to coat the lead dioxide at the anode and increase the durability.

As a first solution to achieve the aforementioned purposes, the present invention provides an anode for the generation of oxygen comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, wherein the coating is Calcium in a low temperature region of 370-400 ° C in an oxidation atmosphere to form the amorphous iridium oxide containing catalyst layer and the amorphous iridium oxide containing catalyst layer is subsequently calcined in a high temperature region of 520-600 ° C in an oxidation atmosphere to crystallize almost all the amount of iridium oxide in the catalyst layer.

As a second solution to achieve the aforementioned purposes, the present invention provides an anode for the generation of oxygen comprising a conductive metallic substrate and a catalyst layer comprising iridium oxide formed on the conductive metallic substrate, wherein the degree of The crystallinity of the iridium oxide in the catalyst layer after post-calcination is 60% or more.

As a third solution to achieve the aforementioned purposes, the present invention provides an anode for the generation of oxygen comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, wherein the diameter of the iridium oxide crystals in the catalyst layer is 8.0 nm or less.

As a fourth solution to achieve the aforementioned purposes, the present invention provides an anode for the generation of oxygen comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, in which a base layer of ionized arc metallization (hereinafter referred to as AIP) containing tantalum and titanium ingredients, by means of an AIP process on the conductive metallic substrate before the formation of the catalyst layer.

As a fifth solution to achieve the aforementioned purposes, the present invention provides a The method of manufacturing an anode for oxygen generation, in which a layer of amorphous iridium oxide-containing catalyst is formed on the surface of the conductive metallic substrate by means of calcination in a region of low temperature of 370-400 ° C in an oxidation atmosphere and the amorphous iridium oxide-containing catalyst layer is subsequently calcined in an elevated temperature region of 520-600 ° C in an oxidation atmosphere to crystallize almost the entire amount of iridium oxide in the catalyst layer .

As a sixth solution to achieve the aforementioned purposes, the present invention provides a method of manufacturing an anode for oxygen generation, in which the amorphous iridium oxide-containing catalyst layer is formed on the surface of the conductive metallic substrate by means of of calcination in a region of low temperature of 370-400 ° C in an oxidation atmosphere and the amorphous iridium oxide-containing catalyst layer is subsequently calcined in a high temperature region of 520-600 ° C in an oxidation atmosphere to cause the degree of crystallinity of the iridium oxide in the catalyst layer to be 60% or more.

As the seventh solution to achieve the aforementioned purposes, the present invention provides a method of manufacturing an anode for the generation of oxygen, in which the catalyst layer containing conductive amorphous iridium oxide is formed by means of calcination in a region of low temperature of 370-400 ° C in an oxidation atmosphere and the catalyst layer containing amorphous iridium oxide is subsequently calcined in a region of elevated temperature of 520-600 ° C in an oxidation atmosphere to cause the diameter of the iridium oxide crystals in the catalyst layer to be 8.0 nm or less.

As the eighth solution to achieve the aforementioned purposes, the present invention provides a method of manufacturing an anode for the generation of oxygen, comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, wherein the AIP base layer containing tantalum and titanium ingredients is made by means of the AIP process on the conductive metal substrate prior to the formation of the catalyst layer.

In the formation of the electrode catalyst layer containing iridium oxide by means of the present invention, calcination is carried out, instead of the conventional repeated calcination operations at 500 ° C or more, which is the temperature of Perfect crystal deposition by means of two stages: calcination in a low temperature region of 370-400 ° C in an oxidation atmosphere to form a catalyst layer containing amorphous iridium oxide and post-calcination in a high temperature region of 520-600 ° C in an oxidation atmosphere to contain the diameter of the iridium oxide crystals of the electrode catalyst layer preferably up to 8.0 nm or less and to crystallize the majority of irido oxide preferably up to 60 % or more in terms of crystallinity. In this way, the growth of the crystalline diameter of iridium oxide and the coexistence of amorphous and crystalline iridium oxides and the effective electrode surface area of the catalyst layer could be increased. Thus, according to the present invention, the diameter growth of iridium oxide crystals can be prevented. As reasons, the following reasons are considered. The calcination is carried out in two stages: the first, the coating and the calcination are repeated in a low temperature region of 370-400 ° C, in an oxidation atmosphere and subsequently calcined | subsequently at a high temperature of 520 -600 ° C in an oxidation atmosphere. In comparison with the high temperature calcination of the beginning of the conventional process, the diameter of the crystals in the present invention does not increase beyond a certain amount. If growth of the diameter of the iridium oxide crystals is avoided, the smaller the diameter of the crystals, the greater the surface area of the electrode of the catalyst layer. Subsequently, the overvoltage of oxygen generation of the electrode can be decreased, the generation of oxygen is favored, and the reaction to form PbC > 2 from a lead ion. In this way, the binding of PbC > 2 and the electrode coating.

In addition, according to the present invention, by increasing the electrode surface area of the catalyst layer, the current distribution is dispersed at the same time and the current concentration is avoided and the rate of wear of the catalyst layer can also be avoided. electrolysis medium, and subsequently the durability of the electrode is improved.

Brief Description of the Drawings Figure 1 is a graph indicating the change in the degree of crystallinity of iridium oxide (Ir02) of the catalyst layer by means of the calcination temperature and the post-calcination temperature.

Figure 2 is a graph indicating the change in diameter of iridium oxide crystallinity (Ir02) of the catalyst layer by means of the calcination temperature and the post-calcination temperature.

Figure 3 is a graph indicating the change of the electrostatic capacity of the electrode by means of the calcination temperature and the post-calcining temperature.

Figure 4 is a graph indicating the dependence of the oxygen overvoltage on the calcination conditions.

Detailed description of the invention .

The following explains embodiments of the present invention, in detail, with reference to the figures. In the present invention, it is found that if the effective electrode surface area of the electrode catalyst layer is increased to avoid the adhesive reaction of the lead oxide to the electrode surface, the overvoltage of oxygen generation can be reduced and subsequently , the generation of oxygen is favored and at the same time the adhesive reaction of lead oxide can be avoided. In addition, the present invention has been completed from the idea that it is necessary that the iridium oxide of the catalyst layer be mainly crystalline in order to improve the durability of the electrode at the same time, and the experiments were repeated.

In the present invention, calcination is carried out in two steps, first, a region of low temperature of 370-400 ° C, in an oxidation atmosphere to form a catalyst layer containing amorphous IrÜ2 in the calcination, subsequently, in a region of elevated temperature of 520-600 ° C in an oxidation atmosphere for post-calcining, through which the iridium oxide of the catalyst layer almost crystallizes.

Through the experiments carried out by the inventors of the present invention, it has been found that the amorphous iridium oxide-containing catalyst layer, which can greatly increase the effective surface area of the electrode, consumes amorphous iridium oxide. fast by means of electrolysis and the durability is reduced relatively. In other words, it is considered that it is not possible to improve the durability of the electrode unless the iridium oxide of the catalyst layer is crystallized. Therefore, in order to achieve the purpose of the present invention that the effective electrode surface area of the catalyst layer increases and the electrode overvoltage is reduced, the present invention applies a two-stage calcination: calcination at low temperature further post-calcination at elevated temperature in order to control the diameter of the iridium oxide crystals of the catalyst layer, through which the iridium oxide crystal, of smaller size than the conventional product precipitates, gives as resulting in a greater effective electrode surface area of the electrode catalyst layer and a lower overvoltage. In addition, it was found that in the catalyst layer of the electrode manufactured by means of the - - calcination process of the present invention, there is a small amount of amorphous iridium oxide, but said small amount of amorphous iridium oxide is effective for an effective surface area increase of electrode and does not provide a great influence on the durability of the electrode (by means of the evaluation of electrolysis in pure sulfuric acid).

In the present invention, a catalyst layer containing amorphous iridium oxide is formed on the surface of the conductive metallic substrate by means of calcination in a low temperature region of 370-400 ° C in an oxidation atmosphere; subsequently, the catalyst layer containing amorphous iridium oxide is further calcined in a higher temperature region of 520-600 ° C in an oxidation atmosphere to crystallize almost the iridium oxide in the catalyst layer.

It is preferable that the amount of iridium oxide coating of the present invention is controlled to 2.0 g / m2 or less per time in the metal form. This amount is determined by the electrolytic conditions and normal electrolysis is carried out at a current density of 50 A / dm2-130 A / dm2 and in this case, an amount of iridium oxide coating of 1.0 is used. -2.0 g / m2 per time as metal, and the coating time is normally 10-15 times and the total amount is 10-30 g / m2.

The calcination temperature in the low temperature region of 370-400 ° C in an oxidation atmosphere and the post-calcination temperature in the high temperature region of 520-600 ° C in an oxidation atmosphere are determined by the size of particle crystals and the - 5- degree of crystallinity of iridium oxide forming object in the catalyst layer, and the catalyst layer is formed with a low oxygen overvoltage and a high resistance to corrosion in the aforementioned temperature region.

In the present invention, the degree of crystallinity of iridium oxide of the catalyst layer is preferably up to 60% or more and if it is less than this value, the amorphous iridium oxide of the catalyst layer becomes larger and the Iridium oxide from the catalyst layer becomes more unstable and insufficient durability is obtained. Similarly, preferably the diameter of the iridium oxide crystals of the catalyst layer is equal to or less than 8.0 nm and if it is greater than this value, the effective surface area of the iridium oxide electrode of the The catalyst becomes smaller and the overvoltage of oxygen generation of the electrode increases and a generation reaction of PbO2 from lead ions is not avoided.

Prior to the formation of the catalyst layer, it is preferable to form the AIP base layer comprising a valve metal base alloy containing crystalline tantalum and titanium components by means of an AIP process on the conductive metal substrate. If the AIP base layer is provided on the conductive metallic substrate, it is possible to avoid additional interfacial corrosion of the metallic substrate. The base layer consisting of a TiTaOx oxide layer can be applied instead of the AIP base layer.

The catalyst layer was formed in such a way that the aqueous solution of hydrochloric acid of IrCl3 / Ta2Cls, as Liquid coating is coated on the titanium substrate coated with AIP at 1.1 g-Ir / m2 per step and calcined in a low temperature region of 370 ° C-400 ° C. After repeating the coating and calcination process until the necessary amount of catalyst support was obtained, post-calcination was carried out in a high temperature region of 520-600 ° C. In this way, the electrode sample was prepared. The prepared sample was measured with respect to the Ir02 crystals of the catalyst layer by means of X-ray diffraction, oxygen generation overvoltage, electrostatic capacity of the electrode, etc., and was evaluated in terms of acid electrolysis sulfuric acid and the electrolysis of sulfuric acid with added gelatin and the lead adhesion test.

As a result, it was found that in the case of iridium oxide the catalyst layer was formed by means of calcination in a region of low temperature of 370-400 ° C and post-calcination in a high temperature region of 520- 600 ° C, the majority of Ir02 of the catalyst layer formed was crystalline, the diameter of the crystals became smaller, and the effective surface area of the electrode increased. Oxygen generation overvoltage was reduced to approximately 50 mV by means of conventional products at the same time, too. After examining lead adhesion, the amount of lead adhesion was 1/10 that of conventional products at the lowest mark, and a suppressive effect of good lead adhesion was recognized. In addition, the electrolysis life of sulfuric acid was of the same kind as that of conventional products, thereby proving the improvement in durability.

The experimental conditions and methods of the present invention are as shown below.

The sample manufacturing procedures were the following: (1) Preparation of the AIP substrate Ultrasonic cleaning: Detergent + alcohol, 15 minutes Drying: 60 ° C, more than 1 hour Chemical attack: HC1 ac. 60%, 20 minutes.

Drying: 60 ° C, more than 1 hour Calcination: 180 ° C, 3 hours (2) AIP coating The clean metallic substrate of the electrode was fixed to the AIP unit by means of the application of target Ti-Ta alloy as a source of steam and a coating of tantalum and titanium alloy was applied as a base coat on the surface of the metal substrate of the electrode. Table 1 shows the coating condition.

[Table 1] Catalyst coating Coating solution: Ir / Ta = 65:35, is a water solution of hydrochloric acid.

Rotating coating: 650 rpm, 1 minute Drying at room temperature: 10 minutes Drying in drying device: 60 ° C, 10 minutes Muffle furnace: 15 minutes Cooling: electric fan, 10 minutes Number of coating times: 12 times After calcination: 1 hour The manufacturing conditions of the samples, degree of crystallinity, diameter of the crystals, electrostatic capacity and overvoltage of oxygen generation are shown in Table 2.

[Table 2] Experimental questions for evaluation (1) Degree of crystallinity and measurement of the diameter of the crystals The crystallinity of Ir02 and the diameter of the crystals were measured by means of X-ray difatometry.

The degree of crystallinity was estimated from the intensity of the diffraction peak. (2) Electrostatic electrode capacity Procedures: Cyclic voltammetry Electrolyte: 150 g / 1 H2S04 aq.

Electrolysis temperature: 60 ° C Electrolysis area: 10 x 10 mm2 Counter electrode: Zr plate (20 mm x 70 mm) Reference Electrode: Mercurous Sulfate Electrode (SSE) (3) Measurement of oxygen overvoltage Procedure: current interruption procedure Electrolyte: 150 g / 1 H2S04 aq.

Electrolysis temperature: 60 ° C Electrolysis area: 10 x 10 mm2 Counter electrode: Zr plate (20 mm x 70 mm) Reference electrode: mercury sulfate electrode (SSE) (4) Evaluation of the lead adhesion test The evaluation was carried out by means of consecutive electrolysis in flow cells Electrolyte: 100 g / 1 H2S04 aq.

Additive: 7 ppm of Pb2 + (PbC03), 150 ppm of Sb3 + (Sb203), 40 ppm of Co2 + (CoS04), 100 ppm of gelatin.

Electrolysis temperature: 60 ° C Current density: 80 A / dm2 Electrolysis area: 20 x 20 mm2 Cathode: Zr plate (20 x 20 mm) Electrolysis time: 130 hours The measurement of the amount of adhesion: an anode was taken regularly and the amount of adhesion was calculated by changing the weight of the anode. (5) Acceleration life evaluation (sulfuric acid solution) An electrolyte: 150 g / 1 of H2SO4 aq.

Electrolysis temperature: 60 ° C Current density: 500 A / dm (in pure sulfuric acid solution) Electrolysis area: 10 x 10 mm2 The results of the previous experiment were as follows.

Figure 1 is a graph showing the degree of crystallinity based on the data in Table 2 and Figure 2 is a graph showing the diameter of the crystals based on the data in Table 2. As is evident from the Table 2 and Figures 1 and 2, the degree of crystallinity of the iridium oxide samples 2-4 and 6-8, by means of the examples of the present invention, once subjected to post-calcination, was of 60%. On the other hand, the existence of a clear peak of IrC > 2 which belongs to an electrode catalyst layer by means of calcination at 370 ° C and 390 ° C without post-calcination (samples 1 and 5), and it is confirmed that the electrode catalysts of these examples formed by amorphous Ir02 are formed . Similarly, the sample 9 which is a conventional product is completely crystallized, the degree of crystallinity of iridium oxide being 100% and the diameter of the crystals became larger and was 10.7 nm.

As for the estimation of the degree of crystallinity, the intensity of the crystal X-ray diffraction peak (2T = 28 degrees) of each sample is expressed as a ratio when compared to the intensity of the crystal diffraction peak (2T = 28 degrees) of the conventional product that is assumed to be 100%. By means of calcination at 370 ° C and 390 ° C without post-calcination, IrC crystal was not formed > 2 and the The degree of crystallinity of the iridium oxide was zero. It was found that an amorphous Ir02 formed by means of calcination at a low temperature of 370 ° C and 390 ° C was converted to crystallize almost the entire amount of iridium oxide by means of post-calcination, but that a small amount of IrÜ2 remained. amorphous in the catalyst layer.

The change in the diameter of the Ir02 crystals by means of the calcination conditions was as shown in Table 2. It was found that the diameter of the crystals of the sample after post calcination did not change due to the increase in temperature of post-calcination and became smaller, compared to conventional products. That is, the amorphous Ir02 of the formed catalyst layer was crystallized at a low temperature calcination by means of post-calcination, but it was not possible to prevent the growth of the diameters of the crystals in comparison with the conventional products. In addition, Figure 2 shows the graph that was created based on the data for the diameter of the crystals shown in Table 2. Amorphous Ir02 was formed by calcination at 370 ° C and 390 ° C without postcalcining and the Diameter of the crystals in "0". It was also found that in the case a calcination at more than 410 ° C without post-calcination, with an increasing calcination temperature, increased the diameter of the Ir02 crystals.

If subjected to post-calcination, the amorphous Ir02 formed by means of calcination at 370 ° C and 390 ° C was tested under crystallization, but it was found that the diameter of the crystals was smaller, with respect to conventional products. However, the diameter change - - of the Ir02 crystals due to an increase in the post-calcination temperature was hardly recognized. As is apparent from Table 2 and Figure 2, the size of the iridium oxide crystals after post-calcination of samples 2-4 and 6-8 according to the examples of the present invention was 8.0 nm or less. On the other hand, clear Ir02 peaks attributable to the electrode catalyst layer were not observed by calcination at 370 ° C and 390 ° C without post-calcination (samples 1 and 5), and it was confirmed that the The sample catalyst was formed by amorphous Ir02. In addition, the diameter of the iridium oxide crystals of sample 9, f which is a conventional product is large, and was 10.7 nm.

Subsequently, the measurements were carried out on the change of the effective surface area of the electrode of the electrode catalyst layer prepared by calcination at a low temperature after post-calcination at an elevated temperature.

The electrostatic capacitance of the electrode calculated by means of the cyclic voltammetric process is shown in Table 2 and in Figure 3. Accordingly, it was found that the electrostatic capacity of the electrode (samples 2-4 and 6-8) formed by means of calcination at low temperature plus post-calcination at elevated temperature increases, compared to the conventional product (sample 9), that is, the effective surface area of the electrode also increases. On the other hand, Table 2 and Figure 3 show that the degree of crystallinity and the diameter of the iridium oxide crystals were not modified with the increase in the post-calcination temperature, but the effective surface area of the electrode decreased with increasing post-calcining temperature. It is considered that the reason is that if a catalytic layer is subjected to post-calcination at elevated temperature, the layer becomes thin.

As shown in Figure 4 and Table 2, according to an increase in the effective electrode surface area, the overvoltage of oxygen generation of the electrode can be reduced, compared to the conventional product (sample 9) and reduced at 50 mV by calcination at low temperature plus post-calcination at elevated temperature. The ratio between the capacitance of the catalyst layer and the calcination conditions is shown in Figure 3, based on the capacitance data of Table 2. Because Ir02 of the catalyst layer formed by means of calcination a 370 ° C and 390 ° C without post-calcination was amorphous, showed a maximum effective electrode surface area. The product in which the calcination was carried out at 370 ° C and 390 ° C and the post-calcination was carried out, showed a reduced effective surface area, due to the crystallization of Ir02, but was higher, compared to the conventional products. The reason is that the diameter of the crystals of the Ir02 deposited was small, in comparison with the conventional products and due to the small amount of residual amorphous Ir02. In other words, the effective electrode surface area of the electrode calcined at 370 ° C and 390 ° C and post-calcined increased, compared to conventional products and found to be desirable for the purpose of lowering the oxygen overvoltage.

In addition, it was found that because the degree of Ir02 crystallinity increased according to an increase in the calcination temperature, in the calcination condition at 410 ° C or higher without a post-calcination, the effective electrode surface area is reduced. In addition, even if subjected to post-calcination, a tendency of the effective surface area of the electrode to be further reduced was found, there was no change in the effective electrode surface area due to an increase in the post-calcining temperature. It is considered that this is because the degree of crystallinity and the diameter of the Ir02 crystals do not change much by means of the increase of the post-calcination temperature as described above. On the other hand, in the case of calcination at 480 ° C, with or without post-calcination, it was found that the effective surface area of the electrode was equivalent to that of conventional products.

The dependence of a calcination condition and an overvoltage of oxygen generation are shown in Table 2 and Figure 4. The dependence of the overvoltage of oxygen generation on the calcination conditions is shown in Figure 4. The tendency to modification in the graph of Figure 4 was inverse to that in Figure 3. With the increase of the effective surface area of the electrode, the overvoltage of oxygen generation of the samples tended to decrease. It was found that the overvoltage of oxygen generation of the products formed by means of calcination at 370 ° C and 390 ° C with post-calcination decreased by 30-50 mV, in comparison with conventional products. It is considered that these low-voltage oxygen generating electrodes have a suppressing effect with respect to the adhesion of Pb.

And emplos The following describes examples by means of the present invention, provided, however, that the present invention is not limited to these examples. < Example 1 > The surface of a titanium plate (JIS-I) was dry-shot peened with an iron shot (size G120), followed by pickling in an aqueous solution of concentrated hydrochloric acid for 10 minutes at the boiling point for the cleaning treatment of the metallic substrate of the electrode. The clean metallic substrate of the electrode was fixed to the AIP unit by means of the application of an alloy of Ti-Ta target as a source of steam and a coating of tantalum and titanium alloy was applied as the base layer of AIP on the surface of the metallic substrate of the electrode. Table 1 shows the coating condition.

The coated metal substrate was treated at 530 ° C in an electric air circulation type oven for 180 minutes.

Subsequently, the coating solution prepared by dissolving iridium tetrachloride and tantalum pentachloride in concentrated hydrochloric acid on the coated metal substrate is applied. After drying, the coating was carried out by thermolysis for 15 minutes in an electric oven of air circulation type at 370 ° C to form an electrode catalyst layer comprising mixed oxides of iridium oxide and tantalum oxide. The amount of coating solution was determined so that the thickness of coating for each time of coating solution corresponded to approximately 1.1 g / m2, in the form of iridium metal. This post-calcination operation was repeated twelve times to obtain the electrode catalyst layer of approximately 13.2 g / m2, in the form of iridium metal.

X-ray diffraction was carried out for this sample. No clear iridium oxide peak was observed that could be attributed to the electrode catalyst layer, and the catalytic layer of this sample was formed by amorphous Ir02.

Next, an electrode was fabricated in such a way that the sample coated with the catalyst layer is subsequently burned in an electric oven of the air circulation type at 520 ° C for one hour.

X-ray diffraction was carried out for the sample after post-calcination. A clear peak of iridium oxide was observed which could be attributed to the electrode catalyst layer. ? From this, it was found that crystallization of amorphous Ir.sub.2 occurred by post-calcination at elevated temperature. However, the peak intensity was less than that of Comparative Example 1, and it was considered that amorphous Ir02 remained. Similarly, it was found that the diameter of the crystals calculated from the x-ray diffraction peak was less than that of Comparative Example 1.

On the electrolysis electrode prepared in the manner discussed above, the lead adhesion test and the accelerated life evaluation test were carried out. Table 3 shows the results. When compared with Comparative Example 1 of Table 3, the - - The amount of lead adhesion was one tenth and the life of electrolysis was of a similar value and it was later clear that the suppression of lead adhesion to the electrode and durability had improved.

[Table 3] < Example 2 > The electrode was fabricated for evaluation in the same manner as in Example 1 except that post-calcification was carried out in an electric oven of the air circulation type for one hour at 560 ° C and the same evaluation of electrolysis was carried out. .

X-ray diffraction carried out after post-calcification showed that the degree of crystallinity and the diameter of IrÜ2 crystals in the catalyst layer were equivalent to Example 1.

As shown in Table 3, the amount of lead adhesion to the electrode of Example 2 is one quarter with respect to Comparative Example 1, and the effect of suppressing lead adhesion was confirmed. In addition, the life of accelerated electrolysis increased up to 80% and also improved its durability. - 0- < Example 3 > The electrode was fabricated for evaluation in the same manner as in Example 1 except that post-calcification was carried out in an electric air circulation type oven for one hour at 600 ° C and the same electrolysis evaluation was carried out.

X-ray diffraction carried out after post-calcification showed that the degree of crystallinity and the diameter of IrC crystals > 2 in the catalyst layer were equivalent to Example 1.

As a result of electrolysis evaluation, as shown in Table 3, the amount of lead adhesion and the life of electrolysis were equivalent to those of Example 2 and an effect of suppression of lead adhesion was confirmed. < Comparative Example 1 > The coating solution similar to that of Example 1 was coated on a base layer of tantalum and titanium alloy and the thermally treated metal substrate similar to that of Example 1, and after drying, thermal decomposition was carried out at the temperature of calcination in the circulating air-type electric furnace at 520 ° C and the calcination time up to fifteen minutes and subsequently an electrode catalyst layer comprising a mixture of iridium oxide and tantalum oxide was formed. The repeat time and the amount of coating were similar to those of Example 1. The electrode manufactured in this way without post-calcination was subjected to evaluation of electrolysis and X-ray diffraction as in Example 1.

X-ray diffraction was carried out on this sample, from which a clear peak was observed.

Iridium oxide that could be attributed to the electrode catalyst layer, verifying that the IrC > 2 of the catalyst layer is crystalline.

From the result of the lead adhesion test similar to that of Example 1, the amount of lead adhesion was 120 g / m2. From this result, it became apparent that the effect of suppressing lead adhesion was greatly improved by the method of the present invention. < Comparative Example 2 > In the same manner as in Example 1, except that the post-calcination was not carried out, an electrode was made for evaluation and the evaluation of the electrolysis was carried out in the same manner as in Example 1.

As shown in Table 3, it was found that the electrolysis life of the calcined electrode at 370 ° C without postcalcination was only 1 hour, and from these results, it was evident that the electrolysis durability of the catalyst layer of Ir02 Amorphous was extremely reduced.

As seen from the experimental results, by means of the present invention, the diameter of the Ir02 crystals of the catalyst layer is small, the electrode surface area increases and the oxygen generation overvoltage decreases, compared to the conventional product, by means of a calcination in a region of relatively low temperature of 370-400 ° C and post-calcination in a region of higher temperature of 520-600 ° C. Therefore, by favoring the oxygen generation reaction, an effect was carried out of suppression of lead adhesion simultaneously. In addition, because there are iridium oxides in the catalyst layer mainly in the form of crystals, the durability of the electrode was achieved.

The present invention relates to an anode for the generation of oxygen used for various industrial electrolysis and to a manufacturing process therefor; more in detail, it is applicable to an anode for oxygen generation used for industrial electrolysis which includes the manufacture of electrolytic metallized papers such as electrolytic copper metallized paper, liquid aluminum contact, electrogalvanized steel plate continuously and metal extraction.

Claims

1. An anode for the generation of oxygen comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, in which the coating layer is calcined in a low temperature region of 370-400 ° C, in an oxidation atmosphere to form the catalyst layer containing amorphous iridium oxide and the amorphous iridium oxide-containing catalyst layer is subsequently calcined in a higher temperature region of 520-600 ° C in an atmosphere of oxidation to crystallize almost all the amount of iridium oxide in the catalyst layer.

2. The anode for oxygen generation of claim 1, comprising the conductive metallic substrate and the iridium oxide-containing catalyst layer formed on the conductive metallic substrate, wherein the degree of crystallinity of iridium oxide in the catalyst layer after post-calcination is 60% or more.

3. The anode for the generation of oxygen, as in claims 1 or 2, comprising the conductive metallic substrate and the catalyst layer containing iridium oxide formed on the conductive metallic substrate, in which the diameter of the crystals is made of iridium oxide in the catalyst layer after post-calcination is 8.0 nm or less.

4. The anode for oxygen generation, as in any one of claims 1-3, comprising the conductive metallic substrate and the iridium oxide-containing catalyst layer formed on the conductive metallic substrate, wherein a base layer of metallized of ion by arc containing tantalum and titanium ingredients is formed by means of an arc ion plating process on the conductive metallic substrate before the formation of the catalyst layer.

5. A method of manufacturing an anode for oxygen generation comprising a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the surface of the metal substrate, wherein the amorphous iridium oxide containing catalyst layer is formed on the surface of the conductive metallic substrate by means of calcination in a region of low temperature of 370 ° C-400 ° C in an oxidation atmosphere and the amorphous iridium oxide-containing catalyst layer is subsequently calcined in a region of elevated temperature of 520 ° C-600 ° C in an oxidation atmosphere to crystallize almost all the amount of iridium oxide in the catalyst layer.

6. The method of manufacturing the anode for oxygen generation, as in claim 5, wherein the amorphous iridium oxide-containing catalyst layer is formed on the surface of the conductive metallic substrate by means of calcination in a low temperature region of 370-400 ° C in an oxidation atmosphere and the layer of The amorphous iridium oxide containing catalyst is subsequently calcined in an elevated temperature region of 520 ° C-600 ° C in an oxidation atmosphere to make the degree of crystallinity of iridium oxide in the catalyst layer 60%. or more.

7. The method of manufacturing the anode for oxygen generation, as in claim 5 or 6, wherein the amorphous iridium oxide-containing catalyst layer is formed on the surface of the conductive metallic substrate by means of calcination in a temperature region low of 370-400 ° C in an oxidation atmosphere and the amorphous iridium oxide-containing catalyst layer is subsequently calcined in a high temperature region of 520-600 ° C in an oxidation atmosphere to make the diameter of the Iridium oxide crystals in the catalyst layer is 8.0 nm or less.

8. The anode manufacturing process for oxygen generation, as in any one of claims 5-7, comprising the conductive metallic substrate and the iridium oxide-containing catalyst layer formed on the conductive metallic substrate, wherein the layer The base metal ion-plating by arc containing tantalum and titanium ingredients is formed by means of an arc ion plating process on the conductive metallic substrate before the formation of the catalyst layer. SUMMARY OF THE INVENTION. The present invention aims to provide an anode for the generation of oxygen and a method of manufacturing thereof, used in industrial electrolysis including the manufacture of electrolytic plated papers such as electrolytic copper metallized paper, steel plate electrogalvanized continuously and with contact of aluminum liquid and metal extraction. The present invention relates to an anode for the generation of oxygen and to a manufacturing process therefor which comprises a conductive metallic substrate and a catalyst layer containing iridium oxide formed on the conductive metallic substrate, wherein the coating is Calcium in a low temperature region of 370 ° C-400 ° C in an oxidation atmosphere to form a catalyst layer containing amorphous iridium oxide, and the amorphous iridium oxide-containing catalyst layer is subjected to post-calcination in a region of higher temperature of 520 ° C-600 ° C in an oxidation atmosphere to crystallize almost all the amount of iridium oxide in the catalyst layer.