KR910002101B1 - Electrolytic metallic electrode and process - Google Patents

Abstract

The metal anode for a electrolytic cell is manufactured by treating titanium substrate with air or moisture-saturated nitrogen at 400-1200 deg.c for 10 secs.-30 mins. to form a thin active layer of TiOy(y=0.1-1.999) and an electrochemical catalytic layer of ruthenium, iridium, titanium or more than one of them. The thickness of active layer is more than 10 micron (preferably 10-100 micron). The anode has a good electric conductivity and durability.

Description

Electrolytic metal anode and its manufacturing method

1 is an enlarged view of the electrode surface structure (X 200) according to the present invention (800 ℃ steam oxide thin film electrode).

2 is an enlarged view of a conventional electrode surface structure (X 200).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-consumable metal anode having a good durability and reducing the overvoltage of gas generated at the anode in the electrochemical process of electrolyzing an aqueous solution. When the product is obtained, the overvoltage is formed due to the oxygen gas generated by the side reaction of the chlorine gas, so that the generation of oxygen can be suppressed to lower the overvoltage, and the durability can be filled to obtain an electrolytic product having a low power ratio. It is about the anode.

The difficulty of non-consumable metal anodes used in the prior art has been fully recognized by those working in this field. It is difficult to apply a standard electrode used in a diaphragm process operated under a low current density to an ion exchange membrane electrolysis process in which a fluorine ion exchange membrane operated under a high current density is used. The reason for this is due to the oxygen gas generated during electrolysis, and the amount of oxygen generated increases with high current operation. The oxygen gas passes through the electrochemical catalyst layer and titanium, which is a base material, reacts to form titanium oxide. In the thus formed insulator film, heat is generated due to resistance, so that the temperature increases, and as the time passes, the insulator film gradually increases, and the electrocatalyst layer is peeled off. As such, the standard electrode has a short durability in high current operation.

Therefore, there have been two methods for solving this difficulty by suppressing the generation of oxygen. Firstly, an electrode catalyst having a high oxygen overvoltage and a low chlorine overvoltage, that is, a platinum group metal oxide is coated on a substrate to suppress the generation of oxygen. Representative electrode catalysts include iridium, palladium, ruthenium, rhodium, nickel oxide, and the like. to be. Methods for manufacturing electrodes for these are well described in US Pat. Nos. 3,632,498, 3,711,385 and 3,678,724.

However, they have a disadvantage in that the expensive platinum group compounds are coated and the manufacturing cost is quite high.

In addition, US Pat. No. 3,711,382 describes an electrode that requires a binder. US Pat. No. 3,528,857 proposes NiCo ₂ O ₄ as a contact active surface of a porous anode in a fuel cell, but these are Ni-based metals. The use of compounds has caused significant problems in durability.

Another method is an electrode having an interlayer between an electroplating surface substrate and the surface, and a representative patent therefor describes an electrode having an interlayer as US Pat. No. 3,711,397. The interlayer is ruthenium, rhodium or par It is comprised as an oxygen containing compound of radium. The patent points out, in particular, that the electrode does not work without an intermediate layer of precious metal oxide.

However, this also has significant problems in manufacturing cost as using the platinum group compound as the active layer.

US Pat. No. 4,140,813 specifically refers to the fabrication of electrodes having a TiO ₂ -x structure for use in high current density mercury-based electrolyzers, in particular to the method of plasma injection. However, this is an electrode suitable for the mercury-based electrolytic method, and it is difficult to use the ion exchange membrane process because the electrolyzer has a different structure.

However, in general, the requirements for the production of electrolytic electrodes are inexpensive, easy to apply, resistant to chemical and electrochemical erosion, and a cathode coating material having no loss of conductivity over a long period of operation is desired.

Therefore, the present invention has been conducted a number of experiments and studies in order to overcome the existing problems of the patents and to meet the requirements, the electrode consisting of a three-layer structure, the substrate, the substrate active layer, the electrocatalyst layer can meet all the above conditions In order to form an active thin film layer, the present invention has been completed by focusing on the fact that the conventional plasma spraying method has a high consumption rate of raw materials, and thus, an amazing effect can be obtained by using air oxidation or steam oxidation. .

It is an object of the present invention to provide a method for producing an electrolytic cell metal anode by forming the active thin film layer on a substrate, and another object of the present invention is to prepare an active thin film layer prepared on a substrate. Another object of the present invention is to provide a method for producing an electrolytic cell metal anode which forms the active thin film layer on a substrate and forms an electrochemical catalyst layer.

Further, another object of the present invention is to provide an electrolytic cell metal anode composed of a substrate, an active thin film layer and an electrochemical catalyst layer.

In order to achieve the above object, the present invention uses titanium as a suitable substrate, and an air oxidation or steam oxidation method is used as a method of forming an active titanium thin film layer between the titanium substrate and the electrocatalyst layer.

Hereinafter, the present invention will be described in detail.

That is, the present invention is to prepare an electrode used as an anode in an electrolytic cell containing a water-soluble electrolyte, the TiOy active thin film layer having a y value of at least 0.1 by treating a titanium substrate with air or moisture saturated nitrogen at 400 ~ 1200 ℃ It is related with the manufacturing method of the metal anode for electrolytic cell characterized by forming.

Here, the preferred y value in the titanium active layer TiOy is 0.1 to 1.999. If this value is exceeded, the conductivity is close to 0, which does not satisfy the basic condition of the electrode. The more preferable y value is 1.6 to 1.999 in terms of conductivity. 1.95-1.999.

In addition, since the thickness of the active thin film layer is related to the durability of the electrode, the electrode life is required to be maintained for at least 7 years or more, so it is appropriate that the thickness is at least 10 μm. If it exceeds 100㎛ to exhibit the properties can affect its manufacturing difficulties and the conductivity may adversely affect.

Furthermore, as described above, the electrical conductivity can be controlled by controlling the y value of TiOy, and the lifetime of the electrode can be maintained longer than before by controlling the thickness of the TiOy layer. The closer the y value of TiOy is to 2, the better the manufacturing equipment. The electrode having the same structure as the rutile structure of the electrode catalyst layer (titanium oxide and platinum group oxide) to be described later, and satisfies the conditions of 1.7 ≦ y ≦ 1.8 and thickness of 10 to 100 μm in common, The most preferable result in terms of the conductivity and durability.

The y value and thickness of these active thin film layers vary depending on the firing temperature, the gas inflow amount, the firing time, and the pretreatment. The firing temperature is 400 to 1200 ° C, preferably about 400 ° C, and the gas flow amount is 40 to 90 cc / min. Preferably, it is about 50 cc / min, and baking time is 10 second-30 minutes, Preferably it is about 10 minutes.

If the temperature is above 1200 ℃ the active layer (TiOy) is peeled off the surface of the electrode, if the temperature is too low, the desired value does not come out.

The present invention also relates to a TiOy active thin film layer prepared on a titanium substrate having a y value of 0.1 to 1.999, a thickness of 10 to 100 µm, and a rutile structure.

Once the intermediate layer of the electrode has been formed, a catalytic site should be provided in the electrode to activate the electrochemical reaction. The electrochemical catalyst is preferably a platinum group metal, particularly ruthenium, iridium or an alloy thereof.

These metals, mainly bicomponent or ternary metal compounds, are applied to the electrodes on which the above-described intermediate layer is formed by the known methods described in German Democratic Republic Patent No. 1,671,422 (Beer) and Dens. 53.7 (1985).

That is, the platinum group metal compound is dissolved in an acid such as hydrochloric acid and a solvent (alcohols), and then coated on the active layer of the electrode. Thereafter, heat treatment is performed such that the platinum group compound is formed of an oxide. The electrode catalyst coated on the active electrode during the heat treatment cracks due to thermal expansion, and the cracked portion provides a place for activating a gas (chlorine) generation reaction during electrolysis. Preferable heat treatment temperature is 470-480 degreeC, and the quantity of metal coat | covered is 260 micrometer / cm <2>.

Comparing FIG. 1 and FIG. 2, it can be seen that the electrode catalyst layer having the intermediate thin film layer according to the present invention promotes the generation of chlorine gas at the electrode surface and provides many sites that can be quickly detached from the surface.

The present invention also relates to an electrolytic cell metal anode composed of a titanium base, a TiOy active thin film layer having an y value of at least 0.1 or more, and an electrochemical catalyst layer.

This metal anode is produced by the above-described method so as to be suitable for operation at a high current density of 4 kA / m 2 in the ion exchange membrane process of aqueous alkali metal solution.

The electrode manufactured as described above has the following functions and effects.

That is, first; The activated titanium oxide layer formed by controlling the appropriate conditions is structurally located between the substrate and the electrocatalyst layer to provide a good effect of maintaining good bonding force with the substrate and the electrocatalyst layer. second ; It provides a good bonding force even when the temperature of the electrolyzer changes rapidly, which is very good for the durability of the electrode. third ; The active titanium oxide layer is similar to the thermal conductivity of the electrocatalyst layer, thereby maintaining a good bonding force during heat treatment after applying the electrocatalyst layer. fourth ; The intermediate active titanium oxide layer has very good electrical conductivity.

Hereinafter, the production method and effects thereof of the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples do not limit the scope of the present invention.

Examples 1-5.

Both surfaces of titanium (1 × 1 × 0.1 cm 3) were uniformly blasted on each side for about 2 minutes using α-alumina sand (150-100 μm) by sandblasting. Next, oxalic acid is added to a beaker with an inner volume of 1000 cc, and the sample is added thereto, followed by chemical treatment at 80 ° C for 1 hour. This is to remove the titanium oxide film and impurities formed on the titanium surface.

Then wash with distilled water. Thereafter, the specimens were placed in an electric furnace at 400 ° C., 600 ° C., 800 ° C., 1000 ° C., and 1200 ° C., and air passed through a CaSO ₄ column was introduced into the electric furnace at 80 cc / min.

The time for the specimen to stall in the furnace is about 10 minutes. In order to have the function of the electrode, an electrochemical catalyst is coated on the substrate with the present TiOy activation layer. In the coating method, a mixed solution of ruthenium chloride, titanium chloride, and hydrochloric acid aqueous solution was applied six times on the base electrode with the composition shown in Table 1 below, and calcined at 475 ° C. in the air to prepare a coated metal electrode. (電氣 化學 53.7 (1985) ))

Examples 6-10

After the pretreatment performed in Example 1, the titanium sheet was made at 400 ° C, 600 ° C, 800 ° C, 1000 ° C, and 1200 ° C, and the water was saturated with nitrogen gas at 50 cc / min for 30 minutes. Put it in the electric furnace.

The furnace is then vacuumed using a vacuum pump. Thereafter, as in Example 1, the electrode was prepared by coating ruthenium and titanium oxide aqueous solution with the composition shown in Table 1 below.

Examples 11-15

After pretreatment of the titanium sheet in the same manner as in Example 1 to form a coating of ruthenium-titanium-iridium oxide in the composition of Table 1 to apply to the electrode six times or more to prepare the electrode.

Examples 16-20

In the same manner as in Example 2, the titanium sheet was pretreated and then coated with a coating of ruthenium-titanium-iridium oxide to the titanium sheet six times or more to prepare an electrode.

Electrode experiments were carried out under the conditions of electrolyte temperature of 25 ° C. and current density of 50 kA / m2 in 1M NaCl and 2M HClO ₄ aqueous solution using each electrode prepared as above as an anode. The potential of the electrode was measured to measure the potential, and is shown in Table 1 below.

Comparative Examples 1 to 3

The electrode without a conventional air oxidized or steam oxidized intermediate active thin film layer was coated with an alloy having the composition as shown in Table 1 below using the same method as in Example, and the performance of the electrode was measured by the same method. As described in Table 1, the electrode having a three-layer structure according to the present invention has a lifespan of two times or more compared with the conventional one, and it can be seen that it is very excellent in electrolysis of the alkali metal solution.

TABLE 1

Claims (16)

In preparing an electrode used as an anode in an electrolytic cell containing a water-soluble electrolyte, a titanium substrate is treated with nitrogen saturated with air or moisture at 400 to 1200 ° C. to form a TiOy active thin film layer having a y value of at least 0.1. Method for producing a metal anode for an electrolytic cell. The method for producing an electrolytic cell metal anode according to claim 1, wherein y is 0.1 to 1.999. The method for producing an electrolytic cell metal anode according to claim 2, wherein the y value is 1.6 to 1.999. The method for producing a metal anode for an electrolytic cell according to claim 3, wherein the y value is 1.95 to 1.999. The method according to claim 1 or 2, wherein the thickness of the active thin film layer is at least 10 µm. The method of manufacturing a metal anode for an electrolytic cell according to claim 5, wherein the thickness of the active thin film layer is 10 to 100 µm. The method of claim 1 or 2, wherein the active thin film layer has a rutile structure. The method of manufacturing a metal anode for an electrolytic cell according to claim 1, which is treated with air or moisture-saturated nitrogen gas for 10 seconds to 30 minutes. A TiOy active thin film layer prepared on a titanium substrate having a y value of 0.1 to 1.999, a thickness of 10 to 100 µm, and a structure of a rutile structure. In preparing an electrode used as an anode in an electrolytic cell containing a water-soluble electrolyte, a titanium substrate is treated with nitrogen saturated with air or moisture at 400 to 1200 ° C. to form a TiOy active thin film layer having a y value of at least 0.1, and A method of producing a metal anode for an electrolytic cell, characterized by forming a chemical catalyst layer. The method of claim 10, wherein the electrochemical catalyst is composed of one or two or more of oxides of ruthenium, iridium, and titanium. The method of claim 10, wherein the electrochemical catalyst layer is an alloy of one or more of IVB-VIB white metal metal on the periodic table. The method for producing an electrolytic cell metal anode according to claim 10, wherein the y value is 0.1 to 1.999. The method for producing an electrolytic cell metal anode according to claim 10 or 13, wherein the thickness of the active thin film layer is 10 to 100 µm. The method for producing an electrolytic cell metal anode according to claim 10 or 13, wherein the structure of the active layer is a rutile structure. An electrolytic cell metal anode comprising a titanium base, a TiOy active thin film layer having an y value of at least 0.1 or more, and an electrochemical catalyst layer.

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