KR810001285B1 - Method of preparing anode material for electrolytic cells - Google Patents

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Description

Method for manufacturing anode for electrolytic cell

The present invention relates to a method for producing a non-consumable metal anode for use in a process for performing electrolysis by passing a current from one electrode to the other electrode through a water-soluble electrolyte, more specifically, a salt for producing chlorine and caustic soda. The present invention relates to a method for producing a metal anode that can be used in place of the graphite anode currently widely used in electrolytic solution.

The difficulties associated with graphite anodes commonly used in such chlor-alkali electrolyzers are well known to those skilled in the art. As the graphite is consumed, the distance between the cathode and the anode increases, which in turn causes a decrease in output. Moreover, the unnecessary carbon products arising from the chemical, electrochemical and physical consumption of the graphite anode are sufficient to create the need for treatment.

There are many electrode materials with the required electrical conductivity. The difficulty in the art lies in finding economically viable electrically conductive materials that are resistant to chemical and / or electrochemical intrusions for extended periods of time without compromising the conductivity or size somewhat.

There are electrically conductive materials, for example graphite, which are very sufficiently resistant to high conductivity but which are corroded by chemical or electrochemical interference.

Although supporting protective chemical or electrochemical intrusion by forming a protective oxide film, there are also electrically conductive materials that reduce the electrode's ability to provide an efficient flow of current. Metals forming the protective oxide film are referred to as thin film formers, and prominent among these thin film formers is titanium. These thin film formations are also referred to as valve metals.

There are expensive precious metals (such as platinum) that function well as electrodes, but these are not economically feasible on a large scale. Various attempts have been made to coat these expensive precious metal films on inexpensive substrates to provide electrodes with structurally and electrically suitable surfaces, i.e., free from chemical or electrochemical erosion and without loss of conductivity.

Various methods have been performed to provide a cathode for an electrolytic chlorine bath having a long life and more efficient than graphite in terms of power. For example, electrodes made of titanium, tantalum or tungsten have been coated with a mixture of various metals and metals of the group known as platinum group metals. These platinum group metals have been coated on various conductors in a metallic state and an oxide state. Representative patents using platinum group metals in the oxide state are, for example, US Pat. Nos. 3,632,498, 3,711,385 and 3,687,724. U.S. Patent No. 3,711,382 describes an electrode composed of an electrical conductor with an electrically entangled surface of a bimetallic spinel (calcite) that requires a binder. The required binder is defined as a platinum group metal or compound, and bimetal spinel (calcite) is defined as an oxy compound consisting of two or more metals with unique crystal structures and structural formulas. This patent shows that bimetallic spinels are ineffective in the absence of platinum binders.

US Patent No. 3,399,966 discloses C ₀ Om. nH ₂ O and was described for electrode coating (where, m is 1.4 to 1.7, n is in the range of 0.1 to 1.0 Im). South African Patent No. 71/8558 describes the use of cobalt-tartanate as a coating for electrodes.

U. S. Patent No. 3,632, 498 describes an electrode composed of a conductive, chemically resistant substrate coated with at least one thin film forming metal oxide and at least one platinum group metal oxide.

U.S. Patent No. 3,711,397 describes an electrically conductive substrate, an electrically conductive surface constituting a spinel (calcite), and an electrode which is an intermediate layer between the substrate and the surface, the intermediate layer consisting of an oxygen-containing compound of Ru, Rh or Pd. . The patent points out that the electrode will not work without the precious metal oxide interlayer. This patent also indicates that fabrication temperatures of 750 ° C to 1350 ° C should be used. The calcite represented by the example is C ₀ Al ₂ O ₄ .

According to US Pat. No. 3,528,857, NiC ₂ O ₄ , a bimetallic spinel (calcite), has been proposed as a contact active surface of porous oxide electrodes in fuel cells.

Other patents relating to the coating of various spinel (calcite) or other metal oxide coatings on conductors are described in US Pat. 3,775,284, 3,773,554 and 3,663,280.

There is a need for a cathode coating that is inexpensive, readily applicable, resistant to chemical and electrochemical erosion, and free of conductivity loss over long periods of operation. This need is addressed by the present invention in which the electrical conductor is covered with an effective amount of cobalt oxide with a spinel structure which will be described later. The term "effective amount" of coating on a substrate means (1) when a thin film-forming substrate or a chemically stable substrate is used, the "effective amount" is an amount that provides sufficient current distribution between the electrolyte and the substrate, and (2) If it is not a thin film formation and is not chemically stable, the "effective amount" not only provides sufficient current distribution between the electrolyte and the substrate, but also substantially that the substrate is sufficient to protect chemical and electrochemical erosion.

The present invention provides a highly efficient electrode that does not require expensive metals of the platinum group, which provides economic advantages.

1이다. 이들 족들은 본 명세서에서 M 금속원으로 치칭될 것이다. 주기율표는 Van Nostrand의 과학 백과사전, 5판에서와 같은 종래의 주기율표중 어느것이나 좋다.It was not expected to discover that a highly efficient insoluble electrode was produced by coating a bimetal oxide spinel coating of the structural formula MxC ₃ -xO ₄ formed by thermal co-decomposition of a metal oxide, in particular an oxidic metal compound, onto a suitable conductor. Preferably, the conductor is a kind of thin film forming body found to form a thin protective oxide layer when directly or as an anode is brought into contact with the oxidation system of the electrolytic cell. Conductors other than thin film forming metals may also be used, but are not good because they may be chemically eroded if they come in contact with electrolytes or corrosive substrates. In the formula MxC _03- xO ₄ , M is one of Group IB, Group II A or Group II B metals of the periodic table, and O <x

1 These groups will be referred to herein as M metal sources. The periodic table can be any of the conventional periodic tables as in Van Nostrand's Scientific Encyclopedia, Fifth Edition.

Moreover, it has proven beneficial to coprecipitate “modifiermetal oxide” with metal bimetallic spinels. ＂Modifier metal oxide＂ may be Group II B, IV B, V B, VI B, III A, IV A, V A, tantanide or actinide metals. have. Two or more of these modifier metal oxides may be used.

1이고, M은 원소 주기율표의 제ⅠB족, 제 Ⅱ A족 또는 제 Ⅱ B족에 선정한 금속이다)를 가진 바이메탈 스피넬의 유효량을 피복한 전도체로 구성된다.The present invention relates to a method for producing a cathode for use in an electrolytic cell, the material of which the general formula MxC _03- xO ₄ (where 0 <x

1, and M is a metal selected from Groups IB, IIA, or IIB of the Periodic Table of the Elements).

The present invention also relates to a method for producing an anode material for an electrolytic cell made of a cobalt compound coated on an electric conductor, which provides an electric conductor substantially free of foreign material or oxide thin film, and the conductor Thermally decomposing an oxide inorganic cobalt compound to sinter the coated conductor at a temperature ranging from 200 ° C. to 450 ° C. for 2 to 60 minutes in an oxidizing atmosphere to oxidize the inorganic cobalt compound, but to reduce the firing time above the temperature range, After cooling, the coating and firing steps are repeated until the thickness of the cobalt compound layer on the conductor becomes 0.01 mm to 0.08 mm.

The present invention also relates to a bimetallic spinel of general formula MxC _03- xO ₄ , wherein the value of X is in the range of 0.1 to 1.0, and M is selected from the group IB, IIA or IIB metals. A method for producing an anode for an electrolytic cell comprising a conductor coated with an oxidizing metal compound, comprising: cleaning the conductor to remove surface oxides and contaminants, wherein the molar ratio of M metal to C ₀ based on the metal is 1:29 in the conductor. Applying a coating mixture composed of a thermally decomposable oxidative inorganic cobalt compound and a metal compound having a ratio of 1 to 2, and then firing the coated conductor in a temperature range of 200 ° C to 450 ° C for 1.5 to 60 minutes, In the firing step to shorten the firing time, thereby decomposing the mixture of the cobalt compound and the metal compound to produce a bimetallic spinel of the general formula MxC _03- xO ₄ The step of quenching, cooling the bimetallic spinel coating thus produced, repeating coating, firing and cooling a number of times and final firing of the spinel coating in a temperature range of 350 ° C. to 45 ° C. for 0.5 to 2.0 hours. Characterized in that consisting of steps to perform.

The electrical conductor is preferably a thin film forming metal selected from titanium, tantalum, tungsten, zirconium, molybdenum, niobium, hafnium or vanadium. More preferred electrical conductors are titanium, tantalum, or tungsten. Especially titanium is good.

Alloys of the above thin film forming metals may be used, such as titanium containing small amounts of thaldium or aluminum and / or vanadium.

The function of this conductor is to support the electrically conductive thin film of the bimetallic spinel and to conduct current flowing through the spinel film. Thus, it can be seen that there are a number of possibilities for selecting conductors. Thin film substrates are considered the most desirable because the ability of an electrically conductive thin film substrate to form a chemically durable protective oxide layer in a chlorine cell system is important when some of the substrate is exposed to the periphery of the cell. Because.

The modifier metal oxide may be combined with a bimetallic spinel film to form a firm film. The metal of the modifier metal oxide is selected from the following species.

Group III B (Scandium, Yttrium)

Group IV Group B (Titanium, Zirconium, Hafnium)

Group Ⅴ B (Vanadium, Niobium, Tantalum)

Group ⅠB (Chromium, Molybdenum, Dungsten)

Zebu (manganese, technetium, rhenium)

Lanthanides (from lanthanum to rurenium)

Actinides (from actium to uranium)

Group III A metals (aluminum, gallium, indium, thallium)

Group IV metals (germanium, tin, lead)

Ⅴ Group A Metals (Antimon, Bismuth)

The modifier metal oxide is preferably an oxide of cerium, bismuth, lead, vanadium, zirconium, tantalum, niobium, molybdenum, chromium, tin, aluminum, antimony, titanium or tungsten. Mixtures of these modifier metal oxides may also be used.

Most preferred is a modifier oxide selected from zirconium oxide, vanadium oxide, or lead oxide or mixtures thereof, of which zirconium oxide (ZrO ₂ ) is particularly preferred.

In the coating coated on the conductor, the mole fraction based on the metal content of the cobalt metal to the modifier metal oxide or the metal oxide is preferably in the range from 0 to 1: 2, but most preferably 1:20 to 1: 5. to be. The above-mentioned ratio represents the molar ratio with respect to the total cobalt content in the said coating of the modifier oxide metal as a metal. Modifier metal oxides are simply prepared with metal oxides from thermally decomposable metal compounds.

The bimetal oxide spinel of the general formula MxC _03- xO ₄ of the present invention is prepared simply by repeatedly applying a desired mixture of a metal source and an inorganic cobalt compound. The modifier metal oxide or a mixture of modifier metal oxides are simply applied simultaneously so that they can be distributed substantially uniformly through the MxC _03- xO ₄ coating. The M metal compound is selected from Zn, Cu or Mg compounds, wherein the coating mixture preferably contains from about 11: 1 to 2: 1 mole fraction of M-metal to cobalt metal based on the metal. In applying the film, a mixture of the desired decomposable metal compound is applied to the substrate and then thermally oxidized in air or oxygen to produce an oxide. The coating step is repeated as necessary until it reaches a predetermined thickness (preferably 0.01 to 0.08 mm).

The cobalt oxide source may be an inorganic cobalt compound that forms a single metal spinel structure, C ₃ O ₄ , upon formation of a single thermal decomposition, but forms a general formula MxC _03- xO ₄ when properly heated with a M metal source. For example, the inorganic cobalt compound used as a precursor of C ₃ O ₄ may be cobalt carbonate, cobalt chlorate, cobalt chloride, cobalt fluoride, cobalt hydroxide, cobalt nitrate, or a mixture of two or more of these compounds. There is a number. Preferably, the cobalt compound is at least one compound selected from cobalt carbonate, cobalt chloride, cobalt hydroxide and cobalt nitrate. The most preferred among them is cobalt nitrate. The suitability of the inorganic cobalt compound for use in the present invention is readily determined by looking at whether the compound pyrolyzes to form its single metal spinel, C _03- O ₄ .

The M metal source is preferably a metal salt which becomes a metal oxide by pyrolysis in air or oxygen. Most preferred M metals are Mg, Cu and Zn, of which Zn is the best. In the general formula MxC _03- xO ₄ , the value of X is greater than 0 but less than or equal to 1. As for X, it is good that it is 0.1-1.0. Most preferably, when the value of X is 0.25-1.0.

The preferable manufacturing method of the bimetal oxide spinel film of this invention is as follows.

(1) removing the oxides and / or surface contaminants by chemical or polishing methods to prepare a substrate,

(2) a predetermined thermally decomposable inorganic cobalt compound (e.g., one or two or more cobalt inorganic acid salts) is coated on the substrate together with a thermally decomposable M metal source,

(3) The mixture is heated to a sufficiently high temperature for a sufficient time to decompose the mixture to produce an MxC _03- xO ₄ coating. Temperatures of 200-450 ° C. and firing times of 1.5-60 minutes are used, generally 250-400 ° C. is preferred.

In some cases, an inorganic cobalt compound, especially its hydrated form, may be applied to the substrate together with the M metal source compound as a molten metal. The mixing of the original inorganic cobalt compound with the M metal source is carried out in an inert and relatively volatile carrier such as water, alcohols, ethers, aldehydes, ketones (eg acetone) or mixtures of two or three thereof. As used herein, the term “inert” is intended to indicate that the carrier or solvent does not inhibit the production of a given MxC _03- xO ₄ , and the term relatively volatile means that the carrier or solvent is used as the MxC _03- xO on the substrate. ₄ means that it is removed during the application process.

If the firing temperature is high, the firing time is shortened and the best result is obtained. If the firing temperature is low, the firing time for converting the inorganic cobalt compound into the metal oxide becomes long. When a high temperature of about 450 ° C. is used, the firing time can be shortened to 1.5 to 2 minutes. When using a low temperature of less than 200 ℃ firing time should be 60 minutes or more. It is recommended to avoid high temperature above 450 ° C.

It is not desirable to limit the invention to the following theoretical description, which is given only as a plausible explanation for the interaction between heating time and heating temperature observed in practicing the invention. It is believed that if the coating substrate is kept at a constant temperature for an unnecessarily long time, oxygen can penetrate into the substrate and reach the substrate, thereby reducing the effect of the coating substrate as an anode. It is also believed that the prolongation of the heating time as allowed by the respective coatings at the time of the next coating causes the densification of the coating or the loss of porosity, thereby increasing the oxygen permeability. However, in the present invention, when the modifier metal oxide is used in a single or bimetal spinel, the bimetal spinel, MxC _03- xO ₄ has been found to be porous.

Considering that heating is to cause oxygen to reach the substrate through such a porous coating, this high porosity will appear detrimental. Surprisingly, the inventors have found that higher porosity is beneficial as long as the initial coating is carried out within the shortest possible time at the decomposition temperature used, thereby forming a porous MxC _03- xO ₄ (with a modifier metal oxide), but substantially Prevents excessive oxygen migration to the substrate and prevents densification of the net mass. When a substantially porous non-dense primary coating is made, more coating material is deposited by secondary application of the metal compound if the primary coating is substantially or completely dense. At this time, when the secondary coating is thermally decomposed to produce more porous MxC _03- xO ₄ , the primary coating, which is the undercoat, is densified by heating, thereby further preventing oxygen migration to the substrate. Therefore, it is preferable to use only a heating time sufficient for the primary coating to sufficiently produce the MxC _03- xO ₄ coating. For this primary coating, it is preferable to use a maximum temperature of about 400 ° C. with a maximum heating time of about 15-20 minutes. If the coating amount is increased, the undercoat becomes dense and a higher temperature (up to about 450 ° C.) or a longer heating time can be used for subsequent coating. Typically at least four MxC _03- xO ₄ coatings are carried out, preferably at least six times. In the final coating, the oxygen permeability is reduced by giving a separate firing time so that it becomes dense and not sticky during handling and operation. The final firing is preferably carried out in a temperature range of 350-450 ° C. for 0.5 to 2.0 hours.

The optimum firing temperature and time can be experimentally determined for a given metal compound or mixture of compounds. The coating and firing steps can be repeated as many times as necessary to obtain the desired film thickness. In general, a film thickness of 0.01 to 0.08 mm is preferred.

As will be readily appreciated by those skilled in the art, the film thickness and depth measurements of these distillations are primarily averages. The thinner the coating, the more likely there is a “pin-hole” or other defect in the coating. The highest quality film (i.e., the film with the least number of pinholes and bonds) is obtained by covering a plurality of layers so as to form a predetermined thickness. Coatings of about 0.01 mm or less will result in defects that will result in limited efficiency. A film of about 0.08 mm or more is practical, but a thickness of more than that is not improved to meet the cost of such a thick film formation.

By using the above-described coating technique, thin MxCo₃_xO₄ spinel waves with or without mosquito-fired metal oxides can be formed into a convenient shape, such as a mesh, a plate, a sheet, a screen, a rod, a column, or an object. Iii) may be applied to the electrical conductor.

As used herein, in referring to the MxCo₃_xO 'spinel structure, the expression thin film or film indicates that the spinel structure layer is formed on the substrate, even if the spinel structure layer is actually formed by applying a plurality of oxide formers. It means that it is coated and adhered to.

As used herein, the expression “included” when referring to modifier metal oxides in a spinel structure indicates that the modifier metal oxides are mainly homogeneously or uniformly distributed in the spinel structure.

In the following specific example, it is estimated that the thickness of the coated film will be in the range of 0.5 mil to 3 mils (ie, 0.01 mm to 0.08 mm). The reason for estimating the thickness without measuring it directly is that the best measuring methods have to go through the film breaking process. Therefore, it is recommended that the coating technique be first examined for samples to be discarded without testing as electrodes. In view of the number of applied layers, knowing how much the thickness is expected by a given coating method, the coating can be further performed with a reasonable possibility of actually obtaining a coating of the same thickness again.

As in the examples described below, when a plurality of layers were applied to obtain a coating, it was determined that each subsequent layer was not equal to the thickness of the previous coating layer. Therefore, for example, the film formed of 12 layers is not necessarily twice the thickness of the film formed of six layers.

For most coatings in which the electrode of the invention is useful, current densities of about 0.2 to 2.0 amps / in (0.033 to 0.3 amps / cm 2) are typically used. In the examples described below, a current density of 0.5 amps / in &lt; 2 &gt;

(7.62㎝×7.62㎝)이다. 전류는 음극에 연접(鉛接)시킨 황동 및 양극에 용접시킨 티탄봉에 의해 전극에 공급된다. 양극에서 결막간의 거리는 약 1/4인치 (0.635㎝)이다. 전해조의 온도는 양극질 격실에 위치한 열전대 겸 가열기에 의해 제어된다. 일정한 오우버 플루우계를 경유하여 염화나트륨 용약300g/ℓ를 연속적으로 상기 양극질 격실에 공급한다. 염소, 수소 및 수산화나트륨이 전해조로부터 연속회수 된다. 음극질 및 양극질의 수면을 조정하여 음극질내의 NaOH 농도를 1약 110g/ℓ로 유지시킨다. 이전해조에는 정격 전류 전력공급에 의해 전력이 공급된다. 전기 분해는 겉보기 전류밀도를 양극의 단위면적 평방인치(6.54㎠)당 0.5암페어로 하여 수행한다.The kind of test electrolyzer used in Example 1 is a well-known upright diaphragm chlorine electrolyzer. The diaphragm was deposited on a small porosity forced cathode from an asbestos slurry by a known method. Anode and tone are about 3˝ × 3 respectively

(7.62 cm x 7.82 cm). The electric current is supplied to the electrode by brass connected to the cathode and titanium rod welded to the anode. The distance between the conjunctiva and the anode is about 1/4 inch (0.635 cm). The temperature of the electrolyzer is controlled by a thermocouple and heater located in the anode compartment. 300 g / l of sodium chloride solution is continuously fed to the bipolar compartment via a constant overflue system. Chlorine, hydrogen and sodium hydroxide are recovered continuously from the electrolyzer. The surface of the cathode and anode is adjusted to maintain the NaOH concentration in the cathode at about 110 g / l. The transfer bath is powered by the rated current power supply. Electrolysis is carried out with an apparent current density of 0.5 amperes per square inch (6.54 cm 2) of the unit area of the anode.

The etchant used in the following examples is prepared by mixing 25 ml (48 wt% HF) of the assay reagent hydrofluoric acid, 175 ml (70 wt% HNO 3) of the assay reagent gold, and 300 ml of deionized H ₂ O.

The anode potential is measured in a laboratory electrolytic cell specially designed to facilitate measurements at 3 ″ × 3 ″ (7.62 cm × 7.62 cm) anodes. The electrolytic cell is made of plastic. The anode chamber and the cathode chamber are divided and separated into commercial polytetrafluoroethylene diaphragms. The anode chamber contains a heat insulator, thermocouple, thermometer, stirrer, and a rugin capillary probe connected to a saturated Calomel control electrode placed outside the cell. The cell is covered with a lid to minimize evaporation losses. The electrolyte is 300/1 sodium chloride brine. The potential for saturated caramel is measured at ambient temperature (25 ° -30 ° C.). The low potential means a lower power for the unit amount of chlorine produced is a more economical operation.

Example 1

One ASTM grade 1 titanium sheet piece of about 3 s × 3 s × 0.086 (7.62 cm × 7.62 cm × 0.22 cm) is impregnated with 1,1,1-tricoloethane, air-dried and HF-HNO ₃ etched. The solution was impregnated for about 30 seconds and then washed with deionized water to dry. The sheet is blown together with the A1 ₂ O ₃ granulator to obtain a uniformly rough surface and blow air. The coating solution is prepared by mixing an appropriate amount of reagent gold Co (No ₃ ) ₂ .6H ₂ O and Zn (NO ₃ ) ₂ .6H ₂ O so as to be a solution of 2.66 M of cobalt ions and 1033 M of zinc ions. A coating liquid is applied to one surface of the sheet with a brush. The surface is then placed at a position of about 2 kPa (5.08 cm) from the grid of the gas fired infrared generator and heated for about 1.5 minutes. The average anode temperature measured after this period was 350 ° C. The anode was cooled by forced air for about 2 to 3 minutes, then the secondary coating was applied and fired for about 2.5 minutes in a similar manner. Ten additional layers of coating were similarly applied. After the rupture of the twelfth layer was fired in an infrared generator for about 1.5 minutes, the coated sheet was put into a known convection oven and fired at 400 ° C. for 60 minutes. The anode was placed in the above-described laboratory electrolyzer and its operating potential at 70 ° C. and 4.5 amperes (0.5 amps / in 2 or 0.0775 amps / cm 2) was determined to be 1092 millivolts. The initial electrolyzer voltage at 70 ° C, 0.5 amps / in² was 2.849V. It was found that the potential at 70 ° C. and 0.5 ASI was 1099 mA in 294 general during the anode potential test. The voltage after remounting the anode in the test electrolytic cell was 2.841 V at 0.5 ASI and 70 ° C.

Example 2

Eight ASTM grade 1 titanium sheets of about 3 s x 3 'x 0.086 s (7.62 cm x 7.82 cm x 0.22 cm) were immersed in 1,1,1-trichloroethane, dried with air, and dried by HF-HNO. _It was immersed in ₃ etchant for about 30 seconds and washed with deionized water to dry. The sheets are blown together with the Al ₂ O ₃ granulator to obtain a uniformly rough surface and blow into the air. Eight coating solutions were prepared using reagent grade Co (No ₃ ) _{2 ·} 6H ₂ O, Mg (NO ₃ ) ₂ · 6H ₂ O, Cu (No ₃ ) _{2 ·} 3H ₂ O, Zn (No ₃ ) ₂ · 6H ₂ It is prepared by mixing O, ZrO (NO ₃ ) ₂ .6H ₂ O and deionized H ₂ O in an appropriate amount in the molar ratio shown in Table 1 below. Each sheet was applied with a suitable coating liquid (from sample b), fired in a convection oven at 400 ° C. for about 10 minutes and then taken out and cooled in air for about 10 minutes. In a similar manner, ten more coating layers were applied. The 12th coating layer was apply | coated and baked at 400 degreeC for 60 minutes. The operating potential for each positive electrode was measured using the test electrolytic cell described above.

The nature of the crystal species present was determined by X-gay diffraction analysis. Details of this preferred test method can be found, for example, in John Willy End Sons, New York City, NY, USA, in X-ray diffraction methods H.P.Klug and L.E.Alexander (1954). Several samples of the coating were scraped from the anode surface using a knife of small titanium alloy. X-ray films were photosensitive with Fe-Kαl lines. Shooting with a Guinier refocusing camera using a quartz crystal monochromator resulted in high contrast powdery spots. Aluminum sheet internal standard was used.

또는 Zn⁺⁺이 Co⁺⁺를 대치할때 결정 격자(結晶格子)가 약간 팽창된다는 것이다. 이러한 팽창은 X-레이 회절 반점내의 어떤 라인들의 약간 넓은 d-행간(行間)으로 이동되는 결과이다.The crystal structure of single metal spinel Co ₃ O ₄ is very similar to that of bimetallic spinel CuCo ₂ O ₄ and ZnCo ₂ O ₄ , with one notable feature being the

Or, when Zn ⁺⁺ replaces Co ⁺⁺ , the crystal lattice expands slightly. This expansion is the result of a shift to the slightly wider d-intersection of certain lines in the X-ray diffraction spot.

This particular shift was observed in all the anodes prepared for use in this example, which shifted more as the amount of “foreign ion” increased. Spots on the stoichiometric coatings of CuCo ₂ O ₄ and ZnCo ₂ O ₄ are the same as reported in the literature for such compounds. Thus, it is concluded that the bimetallic spinel precursors of the present invention form a series of solid solutions with a single metal spinel Co ₃ O ₄ .

TABLE 1

[Comparative Example]

(1) The term "expanded" means that the cobalt spinel has a metal substitution.

(2) The anode potential was accumulated at 70 ° C, 0.5ASI vs. 30 ° C, SCE.

(3) is an approximation of X in structural formula MxCo ₃ -xO ₄ .

One reinforcing mesh made of ASTM grade 1 titanium, which is about 3 s × 3 s × 0.060 sq (7.62 cm × 7.62 cm × 0.15 cm), was coated with a metal oxide with a commercial supplier of a metal chlorine electrolytic cell anode. This coating is supplied for industrial anodes and is probably a representative example composed mainly of ruthenium and titanium oxide. The positive electrode was put into the above-mentioned laboratory electrolytic cell, and the potential difference measurement was performed. The operating potential at 4.5 amps (0.5 amps / in &lt; 2 &gt;) at 70 deg.

A material specimen of about 3 s × 3 s × 11/4 s (7.62 cm × 7.62 cm × 3.18 cm) was cut out from a commercially available graphite chlorine electrolytic cell anode. Two holes were bored to join these anode test pieces. In other words, a graphite rod having a diameter of 1/2 kW (1.2 km) was inserted into one hole, and a 3/8 kW (0.95 cm) graphite bar was inserted into the other hole to connect the potentiometric measuring instrument. Thus, the high resistance metal-graphite phase was avoided, and there was no voltage drop due to the resistance of the current carrying rod as a result of the potential measurement. The sides and back of the anode were covered with an inert, nonconductive polymer. The anode prepared in this way was put in the above-mentioned laboratory electrolytic cell, and the electric potential was measured. The operating potential at 4.5 amps (0.5 amps / in ² ) and 70 ° C. was 1237 mA.

Claims (1)

CLAIMS 1. A method for producing a positive electrode for use in an electrolytic cell having an electrically conductive substrate and containing a water soluble electrolyte, the method comprising: washing the electrically conductive substrate to remove surface oxides and dirt; A mixture of inorganic cobalt compounds that can be thermally decomposed and oxidized with M-metal compounds that can be thermally decomposed and oxidized is applied to the substrate [wherein M-metals are selected from IB, IIA and IIB metals. Wherein the mixture has a molar fraction of the M-metal (based on metal) of 29: 1 to 2: 2 of the cobalt metal] In order to oxidize the metal compound, the substrate is subjected to 200 to 450 캜 for 1.5 to 60 minutes. Or to a temperature higher than the range for a shorter time so that the mixture of cobalt and M-metal compounds decomposes to form a bimetallic spinel film of the structure MxCo _3- xO ₄ (X is 0.1 to 1.0) on the substrate. And then cool the bimetallic spinel-coating agent thus formed: applying a mixture of metal compounds to the substrate, heating the substrate and cooling the bimetallic spinel-coating substrate several times, and impermeability to oxygen and oxygen Final baking of the bimetallic spinel-coated substrate at 350 ° C to 450 ° C for 0.5 to 2.0 hours to form a dense bimetallic spinel coating on the substrate that enhances resistance to migration. A cathode manufacturing method for an electrolytic cell.