KR870001769B1 - Electrodes and method for its manufacture - Google Patents

Abstract

The cathode is made by (a) applying to an electroconductive substrate a coating soln. of metal oxide precursor cpd. (s) and an etchant for the substrate or a previously applied coating; (b) heating to remove volatiles and concentrate and recoat metal deposit from the precursor cpds. and etched from the substrate or prior coating; and (c) heating in the presence of air, 02 or oxidision agent to oxidise the metal deposit. An electrode for use in an electrochemical cell comprises a layer of Ni having a tightly coated heterogeneous metal oxide coating contg. NiO and a Pt gp. metal oxide.

Description

Electrochemical Electrolyzer Electrode and its Manufacturing Method

1 is a graph of the data of some tests.

TECHNICAL FIELD This invention relates to the manufacturing method of an electrode, and its commercial method in an electrolytic cell especially a salt electrolyzer.

There are three electrolytic baths used in the manufacture of chlor-alkali, mercury baths, diaphragm baths and membrane baths. The manipulations of these articles are described in the third edition, KIR-OTHMER ENC YCLOPEDIA OF CHEMICAL TECHNOLOGY, Volume 1, page 799. Other electrolysers using aqueous electrolysis electrodes are called chlorite cells and do not use a divider or separator between the cathode and the anode. In mercury baths, alkali metal precipitates formed by electrolysis of alkali metal salts form amalgams with mercury, which produce NaOH and liberate mercury when reacted with water, which is recovered and recycled to the liquid cathode. Can be.

In the chloro-alkali electrolysis method, a salt solution (electrolyte) is electrolyzed by passing a current through an electrolytic cell having a membrane or a membrane between the cathode and the anode. Chlorine is formed at the positive electrode, and sodium hydroxide (NaOH) and hydrogen (H ₂ ) are formed at the negative electrode. The brine is subsequently supplied to the cell, while Cl ₂ , NaOH and H ₂ continue to exit the cell.

The minimum voltage required to electrolyze an electrolytic salt into Cl ₂ , NaOH and H ₂ can be calculated using thermodynamic data. In practice, however, the theoretical voltage alone makes it difficult to achieve the purpose, and higher voltages must be used to overcome the resistance inherent in various electrolyzers. In order to increase the operating efficiency of the diaphragm or membrane, attempts have been made to reduce the overvoltage of the electrode, the electrical resistance of the diaphragm or membrane, or the electrical resistance of the brine being electrolyzed. The present invention relates to an electrode which is particularly useful as a cathode in the electrolysis of brine, which allows the overvoltage of the cathode to be substantially reduced and the power efficiency is improved.

Since millions of tonnes of electrolysers of alkali metal halides and water each year reduce the operating voltage by only 0.05V, saving enormous energy. Therefore, the industrial sector has devised a means to reduce the required voltage.

As chloro-alkali technology has been developed, several methods have been developed to reduce pre-voltage. Some have tried to reduce the voltage of the cell by changing the physical design of the cell, while others have focused their efforts on reducing the overvoltage at the anode or cathode. The present invention relates to a novel method of making an electrode characterized by very low overvoltage and to the use of the electrode in an electrolytic cell.

It is already known that the overvoltage of an electrode is a function of the current density and its composition. Here, the current density refers to amperes per actual unit surface area of the electrode, and the composition refers to the chemical and physical composition of the electrode. Therefore, in a method of increasing the surface area of an electrode, it is necessary to reduce its overvoltage at a given surface area current density. It is also desirable to use a composition that is a good electrocatalyst, which also reduces overvoltage.

It is well known in the art to coat conductive metals on electrodes using plasma or flame radiation. US Patent No. 1,263, 959 discloses a method of spraying nickel fine particles in a positive electrode, melting the particles, adsorbing by plasma on an iron substrate, and covering the positive electrode.

The cathode was also covered with an electrodeic metal. US Patent No. 3,992,278 discloses a method of coating a cathode with a mixture of particle cobalt and particle zirconium by plasma or flame spinning. Such an electrode is known to reduce hydrogen overvoltage for a long time when used for electrolysis of water or aqueous alkali metal halide solution.

Various metals and metal mixtures have been used to cover the electrodes with plasma or spark radiation. US Pat. No. 3,630,770 describes the use of lanthanide, while US Pat. No. 3,649,355 describes the use of tungsten or tungsten alloys in US Pat. US Pat. No. 3,945,907 describes the use of rhenium, and US Pat. No. 3,974,058 describes the coating of cobalt and luteum on top of it.

Similarly, methods of coating porous electrodes by selective leaching are also well known. The electrode was coated with particle nickel, followed by calcining nickel according to the methods disclosed in US Pat. Nos. 2,928,783 and 2,969,315, and electroplating the alloy onto a substrate, and then as disclosed in US Pat. No. 3,272,788. Leaching the first component of the alloy and pressing or adhering the two or more components together or on the electrode substrate, and then as disclosed in U.S. Patent Nos. 3,316,159, 3,326,725, 3,427,204, 3,713,891 and 3,802,878 Likewise, one or more of the coating components are selectively leached.

A method of making an electrode through a leaching step after plasma or flame injection of the electrode, and a method of going through a leaching step after an electroplating step have also been disclosed. For example, in US Pat. No. 3,219,730, a method of forming an electrode by coating a substrate with a multiple oxide film coating and then removing the substrate by leaching is disclosed in US Pat. No. 3,403,057. Plasma or flame spray on the substrate and then leave the porous electrode by leaching aluminium from the alloy. In US Pat. No. 3,492,720, tungsten, titanium or its alloys are plasma sprayed onto the substrate together with aluminum, thorium and zirconium oxide. Each method was disclosed. The substrate is then removed, leaving only the porous electrode.

US Patent No. 3,497, 425 discloses a method of making a porous electrode by first coating the substrate with a relatively insoluble metal and then again with a more easily soluble metal. In this case, heat treatment is required to cause mutual diffusion between the two coatings, and each coating must be heat treated separately to obtain an optimal state. After leaching the soluble metal, the porous electrode remains. US Pat. No. 3,618,136 describes a process for forming a porous electrode by coating a second component salt composition on a substrate and leaching solubles from the system.

In this case, the two-component salt mixtures should be co-mixed, and the active and inert salts, for example, silver chloride, the same anion as the best results are obtained.

Dutch Patent Application No. 75-07550 discloses a porous cathode by coating an alloy of at least one non-noble metal selected from nickel, cobalt, chromium, manganese and iron with a second regenerative metal and then removing at least a portion of the sacrificial metal. How to make it public. In particular, the sacrificial metal is selected from zinc, aluminum, magnesium and tin.

The sacrificial metal is removed by leaching with sodium hydroxide solution or acid solution.

Japanese Patent No. 31-6611 discloses a method of making a porous electrode by electroplating a nickel coating on a substrate and then coating zinc or other soluble material that can be dissolved in an alkaline solution. The coated electrode is then immersed in an alkaline solution or subjected to electrochemical anodization to elute remove zinc or other processed material to form a porous electrode. In some embodiments, the coated electrode must be heat treated before immersion.

US Patent No. 4,279,709 discloses a method for manufacturing an electrode including an electrode having reduced overvoltage by coating a mixture of the particle metal and the inorganic particle compound pore-forming agent and then leaching the pore-forming agent to form pores.

Particularly, film-forming metal substrate electrodes coated with titanium oxides of Group 8 metals of the Periodic Table of the Elements are known to be very useful as anodes in the same electrolytic method as in the case of brine electrolysis, especially when titanium electrodes are used in combination with other metal oxides. have. In connection with a variety of other metal oxides, ruthenium oxide, platinum coral and other platinum-based oxides are recognized as being very suitable as a coating for valve metal substrates (particularly Ti) to be used as anodes. Patents relating to such anodes include US Pat. Nos. 3,869,312, 3,632,498 and 3,711,385. Such coating can be carried out in a number of ways, for example, in U.S. Patent No. 3,869,312, the platinum group metal oxides in combination with film forming metal oxides are characterized by thermal decomposition of the platinum group in an organic liquid excipient which optionally includes a reducing agent in the support. A mixture of an organic compound of a compound and a film forming metal is prepared, the organic excipient is evaporated to dry the coating, and the support is then heated to 400 to 550 ° C. to form a coating of the metal oxide. In U.S. Patent No. 3,632,498, a plasma burner is used to heat a substrate coated with a thermally decomposable compound of a platinum group metal and a film forming metal, and the metal is electrically deposited in a galvanic bath, followed by heating in air to form an oxide. It is described that by forming a fine powder oxide coating of the platinum group metal and the coating forming metal can be formed.

Patents relating to electrodes having metal oxide surfaces include US Pat. Nos. 3,616,445, 4,003,817, 4,072,585, 3,977,958, 4,061,549, 4,073,873, and 4,142,005.

The use of platinum group metal oxides, especially ruthenium, in the production of hydrogen in active coatings is also known. Japanese Patent Publications No. 65-9130 and Japanese Patent Application Nos. 76-131474 and 77-11178 disclose a method in which a mixture of platinum group metal oxides with other metal oxides is used as an active cathode coating. U.S. Patent 4,238,311 discloses that a cathode coating consisting of fine particles of platinum group metal and platinum group metal oxide in nickel is useful as a cathode coating.

In general, the use of platinum group metal corals as an active catalyst for hydrogen evolution in modern chloro-alkali electrolyzers using a permionic membrane is common in cases where the concentration of NaOH is above 30% and the temperature exceeds 95 °. However, it is already known that it is difficult to use due to possible extreme NaOH concentrations and temperature conditions. It has been found that the oxide coating made by the conventional method is reduced to the base metal by the use of which the actual coating force with the aging door substrate is lost.

In essence, catalyst coatings made of metals with low hydrogen overvoltage characteristics actually reduce the catalytic activity because, in practice, electrolytic salts and metals such as iron, commonly found in water, are coated on top of metal contaminants. It is also well known. Thus, active coatings that are considered useful for releasing hydrogen in modern electrolytic membrane chlor-alkali electrolysers may have a large surface area of a composition that is somewhat resistant to chemical erosion in such conditions, such as, for example, nickel or various stainless steels. It is limited to porous coatings and the like.

In this case, since the performance of the coating with a large surface area is degraded to the extent that it is characterized by the coating of the same aspect containing the brine used in the electrolytic process and the metal contaminants in water, typically iron (Fe), in practice Low hydrogen overvoltage catalysts do not fully exhibit their catalytic properties. Therefore, the hydrogen overvoltage, as is commonly found in modern membrane chlor-alkali electrolyzers, especially when the current density is 0.23 to 0.54 amp / cm 2 or more, as it changes to the iron's Tafel slope, which characterizes the electrolytic activity of the coating. Will increase. However, it is desirable to maintain the inherent low overvoltage characteristics of materials characterized by low-tape slopes in the Mkchlor alkaline electrolyzer, ie platinum group metal oxides, especially ruthenium coral, during long term operation. According to the present invention, an active coating made of a coral group of a platinum group metal and a second electrocatalyst metal has excellent characteristics such as low hydrogen overvoltage, physical stability and long-term efficiency as a salt electrolytic cathode even under high NaOH concentration, temperature and processing pressure. It turned out. It has also been found that, under some processing conditions, such as temperature, NaOH concentration, pressure, etc., using the electrode according to the invention in the production electrolysis of brine and sodium hydroxide, it is possible to achieve reductions in energy requirements that are not actually achieved by other methods. .

The present invention relates in particular to the preparation of low hydrogen overvoltage cathodes, in which a coating solution of a metal oxide precursor compound and a corrosive agent capable of corroding the surface of a substrate or a previously attached coating is added to a conductive substrate. The coated substrate is heated to remove volatiles from the substrate, and the metal precipitates of the precursor compound and the metal deposits corroded from the substrate or the previous coating are recoated on the substrate or the previously adhered coating, followed by oxygen, It involves oxidizing the metal precipitate by heating it in air or oxidant to a sufficient temperature.

An electrode composed of a conductive or nonconductive substrate coated with a heterogeneous mixed oxide of a white metal and a second electrocatalyst metal attaches the soluble metal compound and the caustic for the substrate to the substrate, and in the case of continuous coating, is already coated on the substrate. The metal oxides are corroded to corrode chemically resistant coatings to make them soluble, and then the substrate is heated to oxidize the metal precipitates to concentrate redeposit the metal precipitates on the substrate, which is then oxidized to form a solid and stable heterogeneous metal. It is made in such a way that a precipitate oxide mixture is obtained.

The conductive substrate may be made of a metal structure that maintains its physical integrity during electrode making. Metal laminations such as coating iron-based metals with other metals, such as nickel or film forming metals (known as valve metals), can also be used. The substrate may be a metal such as iron, steel stainless steel, or another alloy based mainly on iron. Substrates also include non-ferrous metals such as film forming metals or metals that do not form films such as nickel, for example. Metals forming the pill include, in particular, titanium, tantalum, zirconium, niobium, tungsten and alloys thereof and alloys with small amounts of other metals. Non-conductive substrates may be used in particular when the metal oxides of the invention are coated on top of the conductive layer.

The board | substrate used by this coating method can be made into various shapes, such as a flat plate and a curved surface. This new coating method is not limited to substrates of any shape because the chemical and heat treatment steps involved can be applied to any shape of substrate that can be used as an electrode material. Many electrolyzers contain perforated plates or plates. In some cases, these plates are bent to form "pocket" electrodes with parallel sides spaced apart.

Preferred substrates include expanded meshes, perforated plates, woven wires, and fired metal plates, but expanded meshes are most commonly used as porous substrates.

Preferred substrate compositions include nickel, iron, copper, steel, stainless steel, or iron based metals laminated with nickel. The substrate on which the metal oxide coating is deposited is supported or reinforced by its lower substrate or by a lower substrate attached with nickel, iron, copper or the like on the substrate. The substrate on which the metal oxide coating is made is an outer layer of its own laminate or coating structure, and may be a non-conductive substrate having a metal oxide coating formed thereon.

Platinum group metals include Ru, Rh, Pd, Os, Ir, Pt, etc. Among them, platinum and ruthenium are used. Soluble platinum metal compounds include halides, sulfates, nitrates, other soluble salts or soluble metal compounds, and halide salts such as RuCl ₃ hydrate, PtCl ₄ hydrate and the like are frequently used.

The second electrocatalyst metal oxide precursor of the present invention is soluble in Ni, Co, Fe, Cu, W, V, Mn, Mo, Nb, Ta, Ti, Zr, Cd, Cr, B, Sn, La, Si, etc. It is preferably at least one kind derived from the compound. Among them, Ni, Zr, Ti and the like are used a lot, and Ni is the best.

In the solution of the present invention, the substrate may be corroded, and the second and subsequent coatings may be used to corrode and dissolve the most sensitive chemically sensitive parts of the previously formed oxide, but in the case of an elevated temperature, At least one chemical activator capable of simultaneously evaporating from the heated mixture simultaneously with the volatile anions or minor valences generated from the platinum group oxide precursor and the second electrocatalyst metal oxide precursor. Preferred chemically active colorants include most acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and hydrazine hydrosulfate, among which hydrochloric acid and hydrazine hydrosulfate are the best.

In general, a good method in the present invention is to apply a solution formed of at least one platinum group metal compound, at least one electrocatalytic metal compound and a chemical caustic and a volatile organic excipient, preferably isopropanol, to a substrate of interest and is volatile After evaporation of the excipients leaving only the caustic and dissolved metal precipitates, the substrate is heated to a temperature sufficient to substantially concentrate the metal precipitates by substantially extracting the volatilized caustic with anion or secondary atom leaving the metal oxide precursor. Heating the substrate to a degree sufficient to thermally oxidize the metal on the substrate in oxygen or air to convert it to a metal oxide.

The steps described above may be repeated several times to increase the thickness of the coating to achieve the maximum effect of the present invention. In addition, it is often advantageous to lay two or more layers of metal oxide precursors between each thermal oxidation step.

In a preferred embodiment of the present invention, the electrode material comprises a heterogeneous metal oxide coating comprising nickel oxide and a platinum group metal oxide (containing any metal oxide, for example ZrO ₂ ), in the following manner: The nickel layer may be formed on the conductive substrate. That is, a coating solution composed of (1) a nickel oxide precursor, a platinum group metal oxide precursor, an optionally modified metal oxide precursor, and a caustic to dissolve the soluble portion of the nickel metal surface is applied to the nickel metal layer, and (2) By evaporating the volatile portion of the dosing solution to deposit a metal oxide precursor on the concentrated corroded nickel metal surface, (3) heating with air, and (4) cooling the electrode material thus made. . In order to increase the thickness of the heterogeneous metal oxide coating made in this way, the second and subsequent coatings may use the same caustic used as the initial coating or may use other caustic agents. Additional coating may be applied in the same manner as described above. In this manner, an electrode material is made of a nickel metal layer firmly attached to an inhomogeneous metal oxide film including a metal oxide for modification that leads to nickel oxide and a platinum group metal oxide. The platinum group metal oxide is preferably ruthenium oxide. The zirconium oxide is preferably used for the optionally modified metal oxide. The economic form of the nickel metal layer is the leaching of the metal to the cheap conductive substrate such as steel or iron alloy. Such an electrode material is particularly useful for the negative electrode of a chlor alkali electrolyzer.

The temperature at which the metal is thermally coral-corresponds slightly depending on the metal, but is usually 300 to 650 ° C, preferably 350 to 550 ° C.

It is an object of the present invention to make a firmly adherent coating composed of heterogeneous oxides of soluble metals.

It is also within the scope of the present invention to make an oxide mixture that is stabilized and electrocatalytically supplemented by solubilizing and concentrating a previously deposited layer or substrate using a chemical corrosion method and then depositing it in situ. It is a correspondence within.

When explaining the present invention by several embodiments are as follows.

Example 1

The solution consisted of 1 part of RuCl ₃ · 3H ₂ O, 1 part of NiCl ₂ · 6H ₂ O, 3.3 parts of H ₂ NNH ₃ · H ₃ SO ₄ (hydrazine hydrosulfate), 5 parts of H ₂ O and 28 parts of isopropane. The solution was first mixed with all components except isopropanol and stirred for one night, then isopropanol was added and mixing continued for about 6 hours.

The negative electrode was made 40% in the nickel expansion mesh. The cathode was first sprayed with sand and then corroded with 1: 1 HCl. Then it was washed thoroughly, soaked in isopropane and dried in air. The negative electrode was immersed in a coating solution, dried in air, then placed in an oven at 375 ° C. and baked for 20 minutes. The coating was applied six times in the same manner. The negative electrode was immersed in a heating bath at 90 ° C. containing 35% NaOH, passed through a current, and the potential was measured using a standard caramel comparison electrode (SCE) and a lugin probe (Luggin pro be). The cathode potential was measured at -1145 mV for SCE at an electrode density of 2 amps per square inch (0.31 amps / cm 2). The negative electrode was assembled into an experimental membrane chlorine electrolyzer, and operated at an operating current density of 0.31 amp / cm 2 at a NaOH concentration of 31 to 33% at a temperature of 90 ° C., resulting in H ₂ at the positive electrode and Cl ₂ at the negative electrode. The potential of the negative electrode was averaged weekly. The results are shown in Table 1.

Example 2

RuCl ₃ , 3H ₂ O 1 part, NiCl ₂ .

A solution consisting of 1 part 6H ₂ O and 3.3 parts concentrated HCl was made. The solution was mixed overnight and then 33 parts of isopropanolol were added and mixing continued for 2 hours. The negative electrode was prepared according to the procedure of Example 1. The negative electrode was coated in the same manner as in Example 1, but fired at a temperature of 495 to 500 ° C. The coating was formed ten times. The negative electrode potential was measured in the same manner as in Example 1. The potential was -1135 mV relative to SCE. The negative electrode was assembled into a laboratory electrolyzer containing a Nafion polymer membrane, and the electrolyzer was operated at 90 ° C., 31 to 33% NaOH, and a current density of 0.31 amp / cm 2. Cathode potentials were averaged weekly and the results are shown in Table 1.

Example 3

A solution consisting of 1 part of NH ₂ OH.HCl, 5 parts of concentrated HCl, 2 parts of 10% H ₂ PtCl ₆ 6H ₂ O, 1 part of NiCl ₂ 6H ₂ O, and 1 part of RuCl ₃ · 3H ₂ O was prepared. After the solution was mixed for 12 hours, 75 parts of isopropane were added and mixing continued for 2 hours. The negative electrode was prepared in the same manner as in Example 1, and then coated in the same manner as in Example 1, but the coating was applied five times at a firing temperature of 470 to 480 ° C. After the sixth coating was applied, the cathode was calcined for 30 minutes at a temperature of 470 to 480 占 폚. The potential of the negative electrode was measured in the same manner as in Example 1, and was -1108 mV with respect to SCE. The negative electrode was assembled into an experimental membrane chlorine electrolyzer containing the same membrane as Example 2, and the electrolyzer was operated at an electrolysis density of 0.31 amp / cm < 2 > The potential of the negative electrode was averaged weekly, and the results are shown in Table 1.

Example 4

A solution consisting of 3 parts of RuCl ₃ 3H ₂ O, 3 parts of NiCl ₂ 6H ₂ O, 1 part of ZrCl ₄ , 5 parts of concentrated HCl, and 42 parts of isopropanol was prepared, and the solution was mixed for 2 hours. The negative electrode was coated in the same manner as in Example 1, but the firing temperature was 495 to 500 ° C. After the eight coatings were applied, the ninth coating was applied, and then the negative electrode was baked for 30 minutes at a temperature of 470 to 480 ° C. The potential of the negative electrode was measured as in Example 1, and was -1146 mV with respect to SCE. The negative electrode was assembled into an experimental membrane chlorine electrolyzer containing the same membrane as in Example 2, and the NaOH, 0.31 amp at 31.degree. It was operated at a current density of / cm 2. The potential of the negative electrode was very flat and the results are shown in Table 1 and FIG.

Example 5

The negative electrode was prepared as in the examples above and then immersed in a solution containing 1 g of tetraisopropyl titanate in 100 ml of isopropanol. The cathode was then sintered for 10 minutes at a temperature of 475-500 ° C. The coating was repeated three times. A solution was prepared as in Example 2, the cathode was immersed in the solution, dried in air, and calcined at a temperature of 475 to 500 ° C. The coating was repeated six times. The potential of the negative electrode was measured in the same manner as in the previous examples, and the potential was -1154 mV with respect to SCE.

The negative electrode was assembled into an experimental membrane chlorine electrolyzer containing the same membrane in Example 2 and operated at a current density of 0.31 amp / cm 2 at 90 ° C. 31 to 33%. The potential of the negative electrode was very average and the results are shown in Table 1 and FIG.

Example 6 (Comparative Example)

A steel electrode was prepared at 40% expansion, not coated, and assembled as a negative electrode in an experimental electrolyzer using a membrane of the same type as Examples 2-5. The potential of the negative electrode was averaged weekly, and the results are shown in Table 1.

Example 7 (Comparative Example)

A nickel electrode was prepared at 40% expansion, uncoated, and assembled as a negative electrode in an experimental electrolyzer using a membrane of the same type as in Examples 2-5. The potential of the negative electrode was averaged weekly, and the results are shown in Table 1 and FIG.

TABLE 1

Weekly negative voltage by electrode (# 1 to # 7) *

* The voltages shown in Table 1 are correlated, although measured slightly in the same way using a lugin probe, although they are slightly lower than the calculated value. The actual voltage by thermodynamic calculation should be about -1.093V for each cell at temperature 90 ℃, 31 ~ 33% NaOH, 0.31 amp / cm2 of current density.

Example 8

The electrolyzers of Examples 2 to 7 were operated at a temperature of 90 ° C. and NaOH 31 to 33% and a current density of 0.31 amp / cm 2 while maintaining the catholyte chamber and the anolyte chamber of the electrolyzer at atmospheric pressure. Sodium chloride and water were supplied to the catholyte chamber and the anolyte chamber, respectively, to maintain the anolyte concentration at NaCl 180 to 200 g / l and NaOH 31 to 33%. Internal mixing of the electrolyzer was performed by spontaneous rise of the gas by generation of hydrogen from the cathode and chlorine gas from the anode. Data including material and energy balance were collected periodically during the operation of the electrolyzer, and energy requirements for generating NaOH were calculated. The results are shown in Table 2.

TABLE 2

Example 9

For large scale experiments, two sets of pressure membrane chlorine electrolyzers were constructed. The configuration and design of the electrolyzer were the same, but series 1 consisted of nickel wall cathode chamber and nickel electrode in catholyte chamber of electrolyzer, and series 2 consisted of steel wall cathode chamber and steel cathode. The electrodes of series 1 were coated according to the method according to the invention, but the electrodes of series 2 were not coated. Both series were equipped with the same cation exchange membrane as in Example 2. The two series were operated simultaneously in a catholyte chamber with a temperature of 90 ° C., a current density of 0.31 amp / cm 2, and NaOH 31 to 33%. The series was operated at a pressure of 101.325 to 202.650 Pa (1 to 2 atmospheres) while circulating the anode and catholytes through the centrifuge in an electrolytic cell. The flow ratio of catholyte to anolyte was maintained at 1 or more. Energy and material equilibrium data were collected over 45 days and the mean performance values were calculated. As a result, it can be seen that the use of the electrode (series 1) of the present invention can achieve an energy saving of 5% or more on average compared to series 2.

It is also within the scope of the present invention to use the novel electrodes of the present invention in electrolyzers operated at high and low pressures. This electrode is also particularly suitable for use at high temperatures of 85 to 105 ° C. In chlor-alkali thickening, pressures of about 10.325 Pa (1 atm) are typically used, but pressures above about 303.975 Pa (3 atm) can also be used.

The electrode of the present invention is convenient to use in an electrolytic cell in which circulation in the electrolyte chamber is caused by an upward movement (movement) of generated gas in the electrolyte chamber, but in some types of electrolyzers in which electrolyte flows from the electrolytic cell to the electrolytic cell, As an alternative or alternative, there are other pump circulation methods. In some cases, it is desirable to maintain the ratio of the amount of catholyte to at least one relative to the amount of anolyte pumped out.

The electrode of the present invention is useful for chlor-alkali electrolysers having an anolyte with which the pH of the anolyte is maintained or controlled in the range of 1 to 5, such as when an acid such as HCl is added to the anolyte.

Claims (15)

In the electrode manufacturing method for an electrochemical electrolytic cell, Coating the conductive substrate with a coating solvent of the metal oxide precursor compound, a corrosive agent that can corrode the surface of the substrate or other pre-coated coating, Removing the volatiles from the coated substrate, concentrating the metal precipitates of the precursor compound and the corrosive from the substrate or the precoated coating, heating them to recoat over the substrate or the precoated coating, A method of producing an electrode for an electrochemical electrolyzer, characterized by further heating to a temperature sufficient to oxidize the metal in oxygen, air or oxidant. The method of claim 1, A metal oxide precursor compound is selected from metal chlorides, nitrates, sulfates and phosphates. The method according to claim 1 or 2, The metal precursor compound includes at least one metal compound selected from Ru, Rh, Pd, Os, Ir, and Pt, and Ni, CO, Fe, Cu, W, V, Mn, Mo, Nb, Ta, Ti, Zr, An electrode manufacturing method for an electrochemical electrolyzer, comprising at least one metal compound selected from Cd, Cr, B, Sn, La, and Si. The method of claim 1, The caustic is selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and hydrazine hydrosulfate. The method of claim 1, The coating procedure is repeated at least once. The method of claim 1, The temperature at which oxidation of the metal precipitate is carried out is in the range of 300 ℃ to 600 ℃, the heating time of the substrate is 5 to 60 minutes, the electrode manufacturing method for the electrochemical electrolytic bath. An electrochemical electrolytic cell electrode comprising a layer comprising a conductive metal substrate and an electrocatalytic cyclic coating firmly coated on the substrate, And the coating is a heterogeneous metal oxide coating of NiO and d platinum group metal oxides. The method of claim 7, wherein The platinum group metal oxide is at least one metal oxide of a metal among Ru, Rh, Pd, OS, Ir and Pt. Under the seventh or eighth, Platinum group metal oxide is RuO ₂ electrode for an electrochemical electrolytic cell. The method of claim 7 or 8, An electrode for an electrochemical electrolytic cell, wherein the heterogeneous metal oxide coating is a metal oxide for modification. The method of claim 10, An electrode for an electrochemical electrolytic cell, wherein the heterogeneous metal oxide coating is a metal oxide for modification. The method of claim 7 or 8, An electrode for an electrochemical electrolytic cell, characterized in that the heterogeneous metal oxide coating mainly comprises RuO ₂ and NiO together with the metal oxide for modification. The method of claim 7, wherein Electroconductive electrolytic cell electrode, characterized in that the conductive metal substrate is nickel or nickel alloy. The method of claim 7, wherein An electrochemical electrolytic cell electrode comprising a nickel layer between a conductive metal substrate and a heterogeneous metal oxide coating. The method of claim 7, wherein The electrode is an electrochemical electrolytic cell electrode, characterized in that the low hydrogen overvoltage cathode for chlor alkali electrolytic cell.

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