SE453203B - ELECTROLYCELL CELL AND PROCEDURE FOR ITS MANUFACTURING - Google Patents

Description

453 203 2 solid polymer electrolyte (SPE) previously known. As an example, from Japanese Patent Publication No. 45557/76 (corresponding to U.S. Patent 3,489,670) and Japanese Patent Application (OPI) 78788/77 (corresponding to U.S. Patent 4,039,409) electrolysis of water, Japanese Patent Application (OPI) 52297/78 electrolysis of Glauber's salt, Japanese Patent Applications (OPI) 95996/79 and 97581/79 Hydrolysis of hydrochloric acid and Japanese Patent Applications (OPI) 102278/78, 93690/79, 107493/79, ll2398 / 79, 115982/80 and 131187/80 hydrolysis of sodium chloride, etc. previously known.

In electrolyzers for the SPE process, an ion exchange membrane such as electrolyte diaphragm is used and stratified cathode and anode catalyst materials are held on both sides of the diaphragm by being directly bonded to it, through which the electrolysis is carried out. In these cases, an electric current is supplied by bringing a feeder into contact with the electrode catalyst layer. They thus cause the distance between the electrodes to be reduced to the thickness of the diaphragm and theoretically the electrolyte solution is not present between the electrodes.

It is thus possible to reduce the size of the apparatus to a great extent. Furthermore, since loss due to electrical resistance due to the electrolyte solution between the electrodes and the formation of bubbles can be disregarded, at least the corresponding value of the electrolysis voltage can be reduced. The SPE process is therefore an excellent electrolytic system for achieving energy economy.

In prior art processes with tight adhesion electrodes and SPE processes, due to gradual appearances or creases at the ion exchange membranes used in continuous electrolysis, gas, such as hydrogen or chlorine, etc., formed due to separation or irregularities at the ion exchange membranes, to accumulate, which results in impaired contact between the feed means and the electrode catalyst layer or * irregular distribution of the electric current on the electrolyte surface. As a result, problems arise because the electrolysis voltage increases rapidly. One method of solving such a problem involves the insertion of metal wires or a mesh or porous plate as reinforcing means in the inner part of the ion exchange membranes and the use of a polytetrafluoroethylene dispersion as a binder (for example as stated in the Japanese patents (OPI) 138088/80, 139842/80 and 141580/80). However, the introduction of a reinforcing member into the thin ion exchange membrane gives rise to manufacturing problems and properties. Furthermore, since the adhesion of the electrode to the ion exchange membranes is insufficient, it is possible that these two are separated by electrolysis for a long time and this causes the resistance due to the binder to increase.

The following is a summary of the invention.

The present invention makes it possible to overcome the above problems.

An object of the invention is to provide an electrolysis cell using an ion exchange membrane, in which the adhesion between the ion exchange membranes and the cathode is very good and the operation can be carried out in a stable manner for a long time without deformation of the ion exchange membranes, and a method for manufacturing the same.

The invention thus relates to an electrolytic cell comprising a cathode and an anode on both sides of an ion exchange membrane with at least one of the cathode and the anode composed of a gas-liquid permeable porous electrode layer tightly bonded to the ion exchange membranes using heat and pressure and with an ion exchange powder powder. an ion exchange capacity of about 0.1 to 3 milliequivalents per gram of dry resin. With such a construction the object described above is achieved: with the invention and very good effects are obtained as described in detail in the following. The present invention is based on the discovery that in the manufacture of an electrolytic cell by bonding a porous layer electrode to an ion exchange membrane as described in Japanese Patent Application 169406/79 by the inventors of the present invention or in Japanese Patent Applications (OPI) 131187/80 and 138088/80, the ion exchange membranes are strongly bonded to the electrode, if a powdered ion exchange resin is used as a binder for the ion exchange membranes and the electrode.

Thus, according to the present invention, the ion exchange membranes are easily and tightly adhered to the porous layer electrode with dimensional stability. This means that separation of the ion exchange membranes does not occur, even if electrolysis is carried out for a long period of time. Furthermore, significant effects are obtained in that the occurrence of bends or creases can be prevented without the use of the reinforcing member described above and because it becomes possible to work in a stable manner at low electrical voltage for a long period of time.

The following is a detailed description of the invention.

The ion exchange resin used as a binder is similar to the resin used for the ion exchange membranes and is one which does not impair the properties of the ion exchange membranes as an electrolyte. It also has the advantage of increasing the electrical resistance to a lesser extent.

The ion exchange membrane used according to the present invention is not limited and it is possible to use different kinds of ion exchange membranes alone or as a combination of such depending on the type of electrolytic reaction.

Fluorine-containing cation exchange membranes with ion exchange groups, such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups or phenolic hydroxyl groups, etc., as described in the aforementioned Japanese Patent Applications (OPI) 131187/80 and 138088/80, are preferred for performing electrolysis solutions of ) and other suitable ion exchange membranes that may be used are described in U.S. Pat. to form part of the present description.

The electrode used according to the invention is constructed with a gas-liquid permeable porous layer, so that it can adhere tightly to the ion exchange membranes. It is suitable that both the cathode and the anode adhere tightly to the ion exchange membranes, but only either of the cathode and the anode must adhere tightly to it. The porous layer electrode can have different shapes.

As examples, nets, woven materials, gratings, perforated sheets, sintered porous materials, spray coated porous materials and porous materials obtained by leaching metal parts can be used as such or as electrode substrates coated with an electrode active substance. It is further preferred that the porous layer electrode have a porosity of about 10 to 99% and an aperture size of about 1 μm to 5 mm, preferably 100 μm to 1 mm, to facilitate passage of the electrolyte solution and removal of gases formed but so that non-deformation of the ion exchange membranes is caused by it extending into the openings.

Suitable porous layer electrodes can be made using different known materials with different known processes depending on the electrolyte reaction for which the electrodes are to be used, and the processes described in the above-mentioned Japanese patent applications (OPI) 131187/80 and 169406/79 (corresponding to the U.S. Patent Application 217,608, filed December 18, 1980), may also be used.

By way of example, in the electrolysis of a saline solution (sodium chloride solution) it is possible to use as cathodes porous layers composed of iron, nickel, titanium, zirconium, niobium or alloys comprising these as a main component, for example Ti-Ta, Ti-Ta -Nb, etc., alloys; platinum metals such as Pt, Ru, Ir, Rh or Pd, or oxides thereof such as RuO2, IrO2, etc .; other metals or metal compounds, such as WO3, MoO2, etc .; and carbon or combinations thereof; or porous layers containing iron, nickel or titanium, etc., which are covered with a cathodic material using known means, such as a thermal decomposition process, powder sintering process, plating process or spray coating process, etc. For example, plasma flame spraying, as indicated in the Japanese Patent Applications (OPI) 40676/73 and 46581/76, may be used.

Furthermore, it is possible to use as anodes porous layers which consist of platinum metals, such as platinum, ruthenium, palladium, iridium, rhodium, etc., or oxides of such, such as Ruoz, PdO, IrO 2, Rh 2 O 3, etc., other metals, such as titanium, tantalum, tin or cobalt, etc., or oxides thereof, such as TiO2, Ta2O5, SnO2, etc., or combinations thereof, such as RuO2-TiO2, RuO2-IrO2-Ta2O5, RuO2-SnO2-TiO2, Pt- SnO2, etc., or porous layers composed of titanium, tantalum, zirconium or electrically conductive oxides thereof, such as TiO2_x, wherein using known means, such as a thermal decomposition process, a sintering process, a plating process or a spray coating process, etc. ., as described in U.S. Patents 3,711,385, 3,632,498, etc.

The resulting porous layer electrode adheres tightly to the ion exchange membrane described above using a powdered ion exchange resin.

Examples of powdered ion exchange resins which may be used include known resins having sulfonic acid groups, sulfonamide groups or carboxylic acid groups, etc., such as ion exchange groups, and the resins used in the preparation of: the membranes of the foregoing publications may be used in powder form. However, it is preferred to use the same ion exchange resin as the ion exchange membrane having an ion exchange capacity of about 0.1 to 3 milliequivalents per gram of dry resin to improve the tight adhesion of the ion exchange membranes to the electrode without impairing its electrolyte properties. For example, when using Nafion # ¶2O or # ¶10 (Nafion is a registered trademark of EI du Pont de Nemours Co., Inc.) as an ion exchange membrane, it is preferred to use a powder of the same resin as described above or available powdered ion exchange resin. , such as Nafion # 501 or # 511. the powdered ion exchange resin can be suitably selected. Although the particle size of the average particle size is equal to or less than the average aperture size of the porous layer electrode. Generally, powdered ion exchange resins having an average particle size of about 0.5 to 1 mm are used. powder with such a particle size is used as a binder. When the ion exchange resin penetrates easily into openings in the porous layer electrode during heat treatment under pressure and becomes impregnated therein or fused therewith, whereby the ion exchange membranes adhere strongly and tightly to the porous layer electrode.

Various means can be used to bond the porous layer electrode to the ion exchange membranes using the powdered ion exchange resin. The simplest method involves applying a powder of the ion exchange resin to a surface of the porous layer electrode or ion exchange membranes in a uniform thickness and pressing both of these simultaneously with heating the bonding surfaces from, preferably, electrode. It is suitable that the heating temperature is about 80 ° C. to 380 ° C and that the bonding pressure is about 10 to 10 kp / cm 2. the heat treatment under pressure can be carried out in air or, if desired, in a Furthermore, it is the side for melting the ion exchange resin. inert atmosphere, such as nitrogen or argon, etc. It is also possible to use a method which comprises pre-impregnating the surface to be bonded to the porous layer electrode with the powdery ion exchange resin by: mechanical introduction under pressure or by applying a liquid dispersion of a powdery ion exchange resin and, if desired, fusion by heating to form in a binder layer on the surface of the porous layer electrode, and bonding the ion exchange membranes thereto under pressure with 455 205 8 heating. Furthermore, it is possible to use a method which comprises attaching a powdered ion exchange resin as an adhesive to one or both sides of the ion exchange membranes during its manufacture and bonding the porous layer electrode to the ion exchange membranes under pressure heating. The latter method has the advantage that the adhesion of the ion exchange resin to the ion exchange membranes and the adhesion of the ion exchange resin to the porous layer electrode can be achieved under optimal conditions.

If a porous layer electrode covered with an electrode active substance is used as an electrically conductive porous electrode substrate, it is possible to use a method which comprises tightly bonding the ion exchange membranes to the electrically conductive porous electrode substrate using powdered ion exchange resin using the process described above and then coating the electrode substrate with the electroactive substance. In this process, coating with the electrode catalyst substance must be carried out under conditions in which the ion exchange membranes are not broken, for example by using a "sputtering" process (cathodic sputtering process), a plating process or an evaporation process, etc. Furthermore, the process according to the invention can be used not only to provide a porous inert layer between the ion exchange membranes and the electrode, as described in Japanese Patent Applications 169406/79 and (OPI) 75583/81, but also in the manufacture of other analog electrolyte cells.

The present invention is illustrated in the following with reference to the following examples, but the invention is not limited by these examples.

Example 1.

To a nickel mesh with a mesh size of 20 mesh (mesh distance approx. 0.7 mm) with a wire diameter of 0.5 mm and an area of approx. 50 cm 2, a nickel powder with a medium particle size of 100 .mu.m was applied by sintering for 10 minutes. at 900 ° C in an Hz atmosphere to produce a porous layer cathode, in which a porous layer having a thickness of about 200 .mu.m and a porosity of about 80% is provided on a surface to which an ion exchange membrane was adhered. On the other hand, a commercially available ion exchange resin (ion exchange capacity: about 0.8 milliequivalents / 1 g dry resin) (Nafion # 301) was pulverized to an average particle size of 70 .mu.m. The porous cathode layer described above was sufficiently impregnated with the obtained powder and, in addition, a smaller amount, for example about 5 g / m 2, of the same powder was applied thereto. A cation exchange membrane of Nafion ÅHZO was applied to the treated layer and the adhesion of the ion exchange membranes and the porous nickel cathode was achieved by pressing at a temperature of 250 ° C under a pressure of 10 kp / cm 2. Using an expansion mesh 2 mm thick as the anode, an electrolytic cell was fabricated by placing the anode at a distance of 3 mm from the ion exchange membranes. For comparison, an electrolytic cell was used in which the above-described cathode without the ion exchange membranes bonded to the cathode was arranged at a distance of 1.5 mm. In electrolysis at 40 ° C with the addition of a 10% aqueous solution of NaOH to the cathode chamber and the anode chamber, respectively, the electrolysis voltage with the cathode bound to the ion exchange membranes according to the invention was about 200 mV lower than with the cathode not bound to the ion exchange membranes. Furthermore, no separation of the ion exchange membranes from the cathode was observed after electrolysis had been carried out for about 1000 hours and the operation could thus be continued in a stable manner.

Example 2. p To a rolled titanium mesh with a thickness of 0.1 mm and an opening ratio of 60%, titanium powder with an average particle size of about 50 was applied, without formation of a porous layer L and the layer was sintered at 100 ° C for 20 minutes in vacuum (10_5 E Torr), so as to obtain a porous plate having a thickness of about 50 μm and a porosity of about 80 μm. This porous plate was covered with a composite oxide of Ru and Ti in a metal ratio of 60:40 by weight using a conventional thermal decomposition method to produce a porous layer anode.

Then, the surface of the above-described porous anode was impregnated with powdered Nafion. # B00 (ion exchange capacity: about 0.8 milliequivalents / 1 g dry resin) having an average particle size of 20 .mu.m or less, and an ion exchange membrane of Nafion # 315 was bonded to it. surface described above at 250 ° C by pressing at a pressure of 20 kp / cm 2.

Platinum black (specific surface area 30 m2 / g) and a polytetrafluoroethylene dispersion were mixed in a weight ratio of 100:30.

The mixture was applied to the second surface of the above-described ion exchange membrane to form a cathode layer, and an electrolytic cell was constructed using it.

For comparison purposes, an electrolytic cell was used which was constructed in the same manner except that the anode was bonded directly to the ion exchange membranes without the use of ion exchange resin powder.

As a result of electrolysis at 80 ° C with the addition of a 4 N aqueous solution of NaCl to the anode chamber and a 20% aqueous solution of NaOH to the cathode chamber, operation can be carried out in a stable manner according to the invention at an average electrolysis voltage of 3.3 V for 1000 hours or more and separation of the anode from the ion exchange membranes was not observed at all. During the comparison electrolysis, separation of the anode from the ion exchange membranes occurred, which resulted in a rapid increase in the electrolysis voltage by 1.0 V or more after 15; minutes from the start of the electrolysis operation.

Example 3.

A porous nickel sheet having a thickness of about 1 mm (Cermet No. 5, 453 203 μl manufactured by Sumitomo Electric Ind. Ltd.) was rolled to prepare a porous sheet having a thickness of 0.3 mm and a porosity of 90%. . It was coated with platinum to a thickness of about 1. using a thermal decomposition process to prepare a cathode. Thereafter, the surface was impregnated with a powder of an ion exchange resin (Nafion # 501) having an average particle size of 50 .mu.m to a thickness of about 0.2 mm. An aluminum foil was applied to the resulting porous cathode and the unit was pressed at a temperature of 300 ° C under a pressure of 200 kp / m 2 in a nitrogen atmosphere. When the aluminum foil was removed, a uniform layer of the ion exchange resin was formed, which adhered tightly to one side of the porous nickel cathode plate.

Thereafter, an ion exchange membrane (Nafion # 315) was caused to adhere to the resulting membrane layer by pressing at 250 ° C below iso kp / m 2.

A Ti mesh coated with a mixed oxide of RuO 2: TiO 2 - 1: 1 by weight was used as the anode, which was arranged at a distance of 2 mm from the ion exchange membranes in the construction of an electrolytic cell. When electrolysis was performed under the same conditions as in Example 2, operation under stable conditions could be performed at an electrolysis voltage of about 3.3 V for 1000 hours or more and separation of the porous nickel cathode from the ion exchange membranes was not observed.

The invention has been described in detail with reference to specific embodiments thereof, but it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention.

Claims (9)

455 203 12 PATENT REQUIREMENTS An electrolytic cell comprising a cathode and an anode having an ion exchange membrane disposed therebetween, wherein at least one of the cathode and anode comprises a gas-liquid permeable porous thin electrode layer which is tightly bonded to the ion exchange membranes using heat and pressure and a bonding agent, characterized in that the bonding is effected with a powdered ion exchange resin as binder and that the ion exchange resin powder has an ion exchange capacity of about 0.1 to 3 milliequivalents per gram of dry resin. 2. An electrolytic cell according to claim 1, characterized in that the electrode layer constitutes a cathode. 3. An electrolytic cell according to claim 2, characterized in that the cathode layer is a porous layer prepared by (1) sintering a nickel powder or (2) applying a nickel powder to a porous nickel material by sintering. An electrolytic cell according to claim 2, characterized in that the cathode is a porous plate produced by plating (1) a porous nickel material with a platinum group metal or (2) a nickel powder sintered product with a platinum group metal. 5. An electrolytic cell according to claim 1, characterized in that the electrode layer constitutes an anode. 6. An electrolytic cell according to claim 5, characterized in that the anode is a porous layer prepared by sintering a titanium powder or by applying a titanium powder to a porous titanium material by sintering, the porous plate also being coated with a metal oxide electrode catalyst. 'JZI 453 205 13 A method of manufacturing an electrolytic cell having a cathode and an anode having an ion exchange membrane disposed therebetween, wherein a gas-liquid permeable porous electrode layer such as at least one of the cathode and the anode is prepared and under pressure and heat the porous electrode layer binds to ion exchange membranes with a binder, characterized in that a powdered ion exchange resin having an ion exchange capacity of about 0.1 to 3 milliequivalents per gram of dry resin is used as the binder. 8. A method according to claim 7, characterized in that the method comprises bonding an ion exchange membrane to an electrically conductive porous material such as electrode substrate using the powdered ion exchange resin under pressure and with heating and coating the electrode substrate with a gas. liquid-permeable electroactive material. 9. A method according to claim 7 or 8, characterized in that the powdered ion exchange resin is applied to at least one side of the ion exchange membranes during the production of the ion exchange membranes.