JPH01139786A - Electrode structure - Google Patents

Abstract

PURPOSE:To provide the title electrolytic electrode structure having prescribed thickness And activity by interposing a deposit layer contg. the fine particles contg. beta-lead dioxide powder between a fluorine-based ion-exchange membrane and a lead dioxide electrodeposition coating layer at the time of forming the coating layer on the membrane. CONSTITUTION:The deposit layer contg. the fine particles contg.-lead dioxide powder is formed on one surface of the fluorine-based ion-exchange membrane as the solid electrolyte. The lead dioxide electrodeposition coating layer is then formed on the surface of the deposit layer, and a solid electrolyte-type electrolytic electrode structure is obtained. Since the deposit layer contg. the fine particles contg. beta-lead dioxide powder is interposed between the ion- exchange membrane and the lead dioxide electrodeposition coating layer, and an active substance is not infiltrated into the ion-exchange membrane. In addition, a side reaction is not caused, the current efficiency can be increased, and further the conventional hot pressing which exercises unfavorable influence on the membrane can be dispensed with.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention generally relates to an electrode structure for electrolysis, and more specifically to ozone production by water electrolysis, peroxide production by aqueous solution electrolysis, organic electrolytic oxidation, etc. In particular, the present invention relates to an electrode structure for electrolysis used in electrolytic oxidation reactions at high potentials.

(Prior art and its problems) In recent years, in the electrolytic industry, instead of soluble electrodes such as carbon, titanium or titanium alloys, which are extremely stable under anodic polarization conditions, are used as base materials and electrode active substances, especially platinum group metals, are used on the surface. Electrodes coated with oxides are used. The electrode is a dimensionally stable anode (DSA) or a dimensionally stable electrode (
Due to its excellent electrolytic properties and durability, it is used in most industrial electrolytic processes, such as the generation of oxygen gas by water electrolysis and the generation of halogens and alkali hydroxides by electrolysis of metal halide aqueous solutions. It is used.

On the other hand, anode materials also play an important role in electrolysis such as ozone gas production, peroxide production, and organic electrolysis that utilize anodic electrolytic oxidation reactions. However, since an electrolytic reaction with a lower potential occurs preferentially, the DSA is not suitable for the electrolytic production of ozone gas, etc., and titanium electrodes slightly coated with platinum are only partially used.

In electrolysis for the production of ozone gas, it is essential to search for anode active materials to replace DSA and to improve operational efficiency. Lead, lead oxide, carbon, etc. are used.

Normally, in such an anodizing process, a diaphragm is used to separate the catholyte and anolyte to prevent reduction at the cathode and perform electrolysis. However, this method has problems such as a voltage loss occurring due to the electrolyte present between the anode and the cathode, and the current density not being able to be increased because it is difficult to provide a sufficiently large electrode area. In order to solve this problem, recently the so-called SPE (Solid Pol
ymerElectrolyte) method is being carried out.

The SPE method can also be applied to the above-mentioned ozone production and peroxide production, and it is possible to produce an spE electrolysis device using the above-mentioned lead, lead oxide, carbon, or the like as an electrode active material. However, if the conventional method for producing SPH is applied as is to producing SPE using lead dioxide or the like as an electrode active material, the following disadvantages will occur. In other words, when fine particles are firmly attached to an ion exchange membrane or the like by a hot press method, a temperature of about 350° C. is required, and at this temperature there is a risk that lead dioxide may partially decompose. A method of electrodepositing particles of an electrode active material is also known, but with this method, it is difficult to obtain a coating of sufficient thickness, and the electrode active material may unevenly enter the inside of the ion exchange membrane, causing side reactions. There are drawbacks such as the possibility that it may become a factor. Furthermore, the electroless plating method has the problem that it is difficult to control the plating itself and that plating takes a long time.

As an improvement to these SPE manufacturing methods, electrodes are manufactured by using a titanium sintered body as a base and coating the surface with lead dioxide.
A method of adhering it to an ion exchange membrane has been proposed (J. Elec, Chew, Sac, No. 13).
2 (1985), p. 367), there remain problems regarding productivity, such as difficulty in obtaining titanium sintered bodies. In addition, U.S. Pat. No. 4,416,747 attempts to solve the above problem by forming a layer consisting of lead dioxide fine particles and an organic binder on a cation exchange membrane, but this method does not require the selection of an organic binder. Although it is effective if the binder is appropriate, there remains the problem that the active substance, lead dioxide fine particles, is blocked and the activity is insufficient, and it is necessary to select a binder with excellent adhesiveness and durability. is also quite difficult.

(Object of the Invention) The present invention solves the problem of ridges, particularly when an electrode active material layer mainly composed of lead dioxide is formed on an ion exchange membrane by electrodeposition, the electrode active material flows into the ion exchange membrane. It is an object of the present invention to provide an SPE type electrode structure that solves the problem of non-uniform penetration and has a predetermined thickness of electrode active material and a predetermined activity.

(Means for Solving the Problems) The present invention firstly forms an adhesion layer containing fine particles containing β-lead dioxide powder on one surface of a fluorine-based ion exchange membrane, which is a solid electrolyte, and This is an electrode structure for solid electrolyte electrolysis, characterized in that a lead dioxide electrodeposition layer is formed on the surface of the layer, and secondly, β-lead dioxide powder is formed in the lead dioxide electrodeposition layer in the electrode structure. This is an electrode structure characterized by dispersing fine particles containing.

The present invention will be explained in detail below.

When forming an electrodeposited lead dioxide layer on the surface of an ion exchange membrane, which is a solid electrolyte, the present invention provides an adhesion layer containing fine particles containing β-lead dioxide powder between the ion exchange membrane and the electrodeposited lead dioxide layer. By interposing the layer, it is possible to prevent the active substance from entering the ion-exchange membrane unevenly during electrodeposition, thereby avoiding side reactions and improving current efficiency. It is characterized by eliminating operations that have a negative effect.

A fluorine-based ion exchange membrane is used as the solid electrolyte. The ion exchange membrane is durable and easy to process,
The type of fluorine-based ion exchange membrane is appropriately selected depending on the application. For example, perfluorosulfonic acid type ion exchange membranes are suitable for electrolytic production of ozone.

Next, an adhesive layer containing fine particles containing β-lead dioxide powder is formed on the surface of the ion exchange membrane.In order to improve the adhesion of the adhesive layer to the ion exchange membrane, It is preferable to roughen the surface by performing pretreatment such as sanding or ion sputtering. The method of forming the adhesion layer containing the β-lead dioxide powder is not particularly limited. For example, a slurry containing the β-lead dioxide powder is prepared in advance, the slurry is applied to the pretreated ion exchange membrane surface, and the layer is heated at room temperature. Alternatively, it may be attached by heating and drying, or the β-lead dioxide powder may be fixed on the ion exchange membrane by hot pressing.

The adhesion layer may be formed of β-lead dioxide powder alone, but an electrolytic promoter may be added depending on the application. As the electrolytic cocatalyst, for example, particles of fluororesin, perfluorosulfonic acid type ion exchange resin, or fluorinated carbon are suitable for ozone production, and titanium, zirconium, niobium, tantalum, etc. are suitable for peroxide production. In addition to the above-mentioned substances, carbon is suitable for organic electrolytic oxidation. When the above-mentioned fluororesin or perfluorosulfonic acid ion exchange resin is used as an electrolytic cocatalyst, it not only functions as a cocatalyst but also works to strengthen the bond with the ion exchange membrane.
Furthermore, the resin particles also have the characteristic of promoting gas release.

The particle size of the β-lead dioxide powder used can be selected depending on the application, but it is preferably 100 to 425 mesh; if the particle size is smaller than 425 mesh, gas release from the adhesion layer will be slightly impaired. Also, if the particle size is larger than 100 mesh, the adhesion will decrease.

In order to reinforce the adhesion layer formed in this way and make the electrolytic area larger and have a substantial three-dimensional electrode function, a lead dioxide electrodeposited layer is formed on the adhesion layer by electrolysis. form. The electrodeposition layer mainly contains lead dioxide,
Although the form of the lead dioxide is arbitrary, β-lead dioxide is preferable in consideration of conductivity and durability. The formation of the electrodeposited layer is carried out under acidic conditions using, for example, an aqueous lead nitrate solution as an electrolytic solution, using an ion exchange membrane on which a deposited layer containing the β-lead dioxide powder has been formed as an anode, at 50 to 70°C, 0. ．．
This can be carried out at a current density of 1 to IOA/dn+", whereby a β-lead dioxide layer generated by electrolysis of the lead nitrate is formed on the adhesion layer. In this case, only the part with the adhesion layer is It is desirable to seal the area around it to prevent lead dioxide from precipitating.

β-Lead dioxide particles can be contained in the electrodeposited layer, which is formed by suspending β-lead dioxide powder in the electrolytic solution at the time of forming the electrodeposited layer. The particles in the electrodeposited layer further increase the electrolytic area and make the electrodeposited layer porous to provide an electrode structure with better outgassing. The suspended particles preferably have the same components as those in the adhesion layer, but other components may be used, and the electrolytic promoter fine particles may also be included. Further, the content of these particles in the electrodeposited layer is preferably 60% by volume or less,
Exceeding this may lead to a decrease in physical strength.

As a method for incorporating the particles into the lead dioxide electrodeposition layer, in addition to the so-called suspension plating method in which β-lead dioxide powder is suspended in an electrolytic solution and electrodeposited, electrodeposition of lead dioxide can be used. There is a method of alternately repeating application of a paste containing the particles and a paste containing the particles.

In the electrode structure manufactured in this way, the adhesion layer formed on the ion exchange membrane prevents the electrodeposited lead dioxide from infiltrating unevenly into the ion exchange membrane, and also prevents the electrodeposited lead dioxide from infiltrating the ion exchange membrane as a main electrode active material. It is an electrode structure in which a certain electrodeposited layer has three-dimensional spread and has good gas release.

(Example) The electrode structure related to the present invention will be described in detail below using Examples, but the Examples are not intended to limit the present invention.

Example 1 The surface of a commercially available perfluorosulfonic acid type cation exchange membrane (trade name Nafion 117) was roughened with #1000 emery paper, and then immersed in a 5% by weight nitric acid aqueous solution to roughen the surface of the ion exchange membrane. The sulfonic acid group was converted to the H type, and this was incorporated as a diaphragm in a two-chamber electrolytic cell. One side was filled with a 5 g/l chloroplatinic acid aqueous solution and the other side was filled with a 10 g/l hydrazine aqueous solution and left for 24 hours to form a platinum layer on one side of the membrane. On the other hand, β-lead dioxide prepared by a conventional electrolytic method was pulverized in an agate mortar, and the resulting fine particles of 250 mesh were mixed into a PTFE water suspension (30J manufactured by Mitsui Fluorochemical Co., Ltd.) and perfluoro ion exchange resin. The mixture was kneaded together to form a paste, which was applied with a brush to the surface opposite to the platinum-supported surface of the ion exchange membrane, left at room temperature to smooth, and then heated and pressed at a temperature of 160.degree. The thus prepared ion exchange membrane with platinum attached on one side and β-lead dioxide on the other side was assembled again into a two-chamber electrolytic cell, and the chamber on the β-dioxide vessel side was filled with 400 g/l of lead nitrate aqueous solution. , platinum on the ion exchange membrane is used as a cathode, and the β-
Electrolysis was carried out at 60° C. and 2 A/dm for 2 hours using a titanium plate placed in contact with the lead dioxide adhesion layer as an anode.

As current collectors, porous nickel with platinum plating on the surface is used on the cathode side, and titanium mesh coated with β-lead dioxide is used on the anode (lead dioxide) side, and these are installed in close contact with the electrode structure. Then, electrolysis was performed by filling the anode side with deionized water. Oxygen gas containing 14% ozone could be obtained under conditions of 20°C and a current density of 100 A/dm2. The sliding voltage during electrolysis was 3.7■.

Example 2 An ion exchange membrane with platinum attached to one side was prepared in the same manner as in Example 1. After kneading β-lead dioxide of 345 mesh with ethyl alcohol to make a paste, applying the paste to the opposite side of the ion exchange membrane to which the platinum was supported, and leaving it to dry at room temperature to smooth it. 160°
Pressure bonding was carried out at a temperature of C.

Furthermore, a lead dioxide electrodeposition layer was formed by electrolysis in the same manner as in Example 1. The solid electrolyte single electrode structure thus produced was assembled into the same electrolytic cell as in Example 1, and the anode chamber was filled with deionized water to perform electrolysis. 20℃, 100 A/dI
Oxygen gas containing 12% ozone could be obtained under the condition of a current density of 1+''. The sliding voltage during electrolysis was 4.2V.

Example 3 The surface of the ion exchange membrane of Example 1 was activated by sputtering with argon ions. The ion exchange membrane was immersed in a 5% by weight aqueous nitric acid solution to convert it to H type, and this was incorporated as a diaphragm in a two-chamber electrolytic cell, and a platinum coating was formed on one side in the same manner as in Example 1.

A mixture of β-lead dioxide fine particles prepared by electrolysis, titanium oxide, and zirconium oxide particles was treated in vacuum at 1100°C for 6 hours, and the partially reduced fine particles were kneaded with a PTFE water suspension to prepare a paste. An adhesion layer was formed on the ion exchange membrane in the same manner as in Example 1.

The ion exchange membrane was assembled into a two-chamber electrolytic cell again, and the β-lead dioxide layer side was filled with a 400 g/l lead nitrate aqueous solution in which fine particles having the same components as the above paste were suspended, and heated at 65°C for 2 hours.
A/dm” on the surface of the adhesion layer containing β-lead dioxide,
forming an electrodeposited layer of β-lead dioxide containing the fine particles;
It was made into a solid electrolyte type electrode structure.

The electrode structure was assembled into an electrolytic cell in the same manner as in Example 1, and deionized water was electrolyzed. 20”C1100A/dI
Under the condition of a current density of 11", oxygen gas containing 16% ozone could be obtained from the anode chamber. The sliding voltage during electrolysis was 3.6V.

(Effects of the Invention) The present invention forms an adhesion layer containing fine particles including a β-lead dioxide adhesion layer on one surface of a fluorine ion exchange membrane,
A lead dioxide electrodeposition layer, in which fine particles containing β-lead dioxide powder may be further dispersed, is formed on the surface of the adhesion layer to constitute an electrode structure for solid electrolyte electrolysis. The β-
Since lead dioxide powder has a higher overvoltage as an electrode active material than platinum group oxides, etc., the electrode structure related to the present invention
Production of alkali hydroxide by electrolysis of alkali halides, production of ozone with a higher electrolytic voltage than oxygen and hydrogen by water electrolysis, production of peroxide by aqueous solution electrolysis, production of organic electrolytic oxidation, etc. Useful for electrolysis.

Since the present invention has this configuration, firstly, lead dioxide in the electrodeposited layer, which is an electrode active substance, is shielded by the adhesion layer, and it is almost impossible for it to non-uniformly infiltrate into the ion exchange membrane during the electrodeposition operation. It disappears. This improves the adhesion between the electrodeposited layer, the adhesion layer, and the ion exchange groin, suppresses side reactions, and prevents a decrease in current efficiency, making it possible to significantly extend the life of the ion exchange membrane and, ultimately, the entire system. It is.

Second, in manufacturing the electrode structure of the present invention, since the ion exchange membrane is not subjected to high temperature heat treatment, deterioration of the ion exchange membrane due to heat can be prevented and a more robust structure can be provided.

Thirdly, since the electrodeposited layer has a substantially three-dimensional spread, there is an increased chance of contact between the reactant and the electrode active material, contributing to an improvement in current efficiency and a reduction in sliding voltage.

Fourth, since both the adhesion layer and the electrodeposition layer are present, it is easier to make the active material layer more uniform.

Fifth, by incorporating particles into the adhesion layer and/or the electrodeposition layer, the porosity can be adjusted and the degree of outgassing etc. can be controlled, making it possible to easily manufacture a device suited to the application.

Claims (8)

[Claims] (1) An adhesive layer containing fine particles containing β-lead dioxide powder was formed on one surface of a fluorine-based ion exchange membrane, which is a solid electrolyte, and a lead dioxide electrodeposited layer was formed on the surface of the adhesive layer. Characteristic solid electrolyte electrolysis electrode structure. (2) The electrode structure according to claim 1, wherein the fine particles constituting the adhesion layer are a mixture of β-lead dioxide and an electrolytic promoter. (3) The electrolytic promoter is one or two of fluororesin, perfluorosulfonic acid type ion exchange resin, fluorocarbon, carbon, and titanium, zirconium, niobium, and tantalum.
One or two selected from the group consisting of two or more types of dioxide
The electrode structure according to claim 2, which is more than one species. (4) The electrode structure according to claim 2 or 3, wherein the amount of the electrolytic promoter is 0.1 to 20% by weight of β-lead dioxide. (5) An adhesive layer containing fine particles containing β-lead dioxide powder is formed on one surface of the fluorine-based ion exchange membrane, which is a solid electrolyte, and fine particles containing β-lead dioxide powder are formed on the surface of the adhesive layer. An electrode structure comprising a dispersed electrodeposition layer of lead dioxide. (6) The fine particles constituting the adhesion layer and/or electrodeposition layer are β-
The electrode structure according to claim 5, which is a mixture of lead dioxide and an electrolytic promoter. (7) The electrolytic promoter is one or two of fluororesin, perfluorosulfonic acid type ion exchange resin, fluorocarbon, carbon, and titanium, zirconium, niobium, and tantalum.
One or two selected from the group consisting of two or more types of dioxide
The electrode structure according to claim 6, which is more than one species. (8) The electrode structure according to claim 6 or 7, wherein the amount of the electrolytic promoter is 0.1 to 20% by weight of β-lead dioxide.