JPS5937754B2 - Structure of water or aqueous electrolyzer - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of a water or aqueous electrolytic cell.

---More specifically, the structure of a water or aqueous electrolytic cell has a structure in which an ion exchange membrane stack in which porous electrode thin films are stacked is sandwiched between current collectors together with an aggregate of conductive fibers entangled with each other. This is related.

A typical example of the aqueous solution is an aqueous alkali metal halide solution such as common salt. Chlorine, hydrogen, and caustic soda are produced by electrolysis of a common salt solution, and hydrogen and oxygen are produced by electrolysis of water.

For example, in the electrolysis of salt water, the general structure of an electrolytic cell using the diaphragm method, which has been widely used in the past, is that there is a considerable distance between the cathode and anode, which are integrated with an asbestos diaphragm, through the electrolyte. It's dark. This is an unavoidable structure as long as the diaphragm method is followed, but the electrical resistance due to the electrolyte between the electrodes is quite large and accounts for a considerable portion of the power loss. Therefore, it is desired to reduce the distance between the electrodes as much as possible, and this also applies to the so-called ion exchange membrane method, which has recently been developed. In recent years, various methods of integrating an ion exchange membrane and an electrode have been proposed as a method of reducing this gap to the utmost, and various methods of electrolysis using the integrated ion exchange membrane stack have been proposed.

For example, JP-A-53-102278, JP-A-54-93690
) 54-97581, 54-112398, 55
-12692, 55-38991, 55-3889
2nd prize.

The methods and products disclosed in these patent applications basically consist of a cation exchange membrane to which electrodes are bonded and a rigid current collector for passing current over a wide area, and the ideal state is In this case, the electrode and the rigid current collector are considered to be in close contact with each other uniformly over the entire surface by tightening the gap between the two current collectors, which is thought to have a large effect on reducing the electrolytic voltage. It is almost impossible to uniformly interpose the ion exchange membrane and electrode thin film in between.

That is, the current collectors that have been proposed so far are rigid porous plates, lattices, expanded wire mesh, etc., and even if a thin layer ion exchange membrane with electrodes made of metal or metal oxide bonded to the surface is sandwiched. Since the surface of the rigid current collector is inherently difficult to smooth, it is difficult to make uniform contact between the current collector and the electrode over the entire surface, so there is a risk that a large current may flow in some areas, so avoid this. Therefore, tightening both current collectors tends to deform or damage the soft ion exchange membrane and the electrodes on its surface. As a result of intensive research into methods for solving the above-mentioned problems, the present inventors were able to easily pass a uniform current through the electrodes bonded to the soft ion exchange membrane, thereby minimizing the risk of damage and deformation of the ion exchange membrane, etc. This led to the invention of a structure for a small electrolytic cell.

Hereinafter, the content of the present invention will be explained in detail, focusing on the electrolysis of a saline solution.

The present invention is an ion exchange membrane, usually a cation exchange membrane,
It is generally made of a fluorine-based polymer or a divinylbenzene-based polymer, but the present invention is not limited thereto.

A water-permeable porous thin film electrode mainly made of metal and/or metal oxide is laminated on one or both sides of the membrane, and the lamination method described in the above-mentioned known document (patent application) is sufficient. As is clear from the manufacturing method, the laminated thin membrane has porous chambers and is permeable to water and ions, so that the ion exchange membrane can easily come into contact with water and ions. Since the thin films mainly composed of metals and/or metal oxides that are laminated as described above are electrodes, they need to have chemical resistance to electrolytes. In the case of a membrane, since the membrane is acidic, it must be acid resistant. Generally, anode materials include iridium, rhodium, platinum, ruthenium, palladium, rhodium-platinum alloy, platinum-ruthenium alloy, etc.
Iridium oxide, ruthenium oxide, palladium oxide, rhodium oxide, etc., alone or in combination, are suitable, and platinum group metals are suitable for the cathode material.

As mentioned above, since the electrodes are as close as possible, power efficiency is very high. However, when sandwiching between rigid current collectors, there is a problem with adhesion as described above, and a large current tends to flow locally, so solving this problem is an important problem in the technical field using the electrolytic method. The present inventors have determined that when the electrodes of the laminated thin film are on both sides of the ion exchange membrane, the electrodes are located between at least one side of the ion exchange membrane and the rigid current collector, and when the electrodes of the laminated membrane are on only one side of the ion exchange membrane, the electrodes are located between the rigid current collector and the ion exchange membrane. The above problem was successfully solved by interposing an aggregate of conductive fibers intertwined with each other between one side or both sides and the respective rigid current collectors.

The mutually entangled fibers are an aggregate of fibrous materials made of a single conductive material that is resistant to corrosion by the electrolyte in contact with it or gas generated by electrolysis, or a composite coated with these materials. The body may be a cotton-like web, felt, a low-density web sintered body, a woven fabric, a net, or other elastic sheet-like material. The web here refers to a non-woven fabric made by cutting fibers into appropriate lengths and making them into a cotton-like fabric using an opening machine, and felt refers to the web made by applying needle punching or the like to strengthen the intertwining. Furthermore, the low-density web sintered body refers to an elastic sintered body in which the web is sintered in a lightly compressed state and fibrous materials are bonded to each other. In this case, the characteristics of the thin layer are governed by the fiber diameter (α), the basis weight (g/(1771)), and the thickness after tightening of the current collector ((11); if the thickness after tightening is small, If the basis weight is too small, uniform adhesion with the ion exchange membrane laminate will be reduced; if it is too large, a large tightening force will be required and the ion exchange membrane laminate will be easily damaged.On the other hand, after tightening If the thickness is too large, it will make it difficult for fluid to pass through, which is undesirable.If the area weight is too small, the adhesion will be poor and there will be problems in uniformly supplying current.However, on the other hand, if it is too thick, it will be difficult both technically and economically. There is no point in this.In other words, the increase in the amount of fibrous material used and the occurrence of gas gaps must be avoided.In the end, the thickness after tightening must be chosen to be appropriate so that it is neither too large nor too small. The thickness after tightening is usually 0.1
~5m1 is suitable. The smaller the fiber diameter of the fibrous material, the better the adhesion with the ion exchange membrane laminate;
~100μ, more preferably 5~50μ. In order to keep the thickness of the fibrous material aggregate constant with good reproducibility, it is convenient to place a spacer made of a corrosion-resistant metal or synthetic resin around the fibrous material aggregate.

Since these conductive fibers can also be used as electrodes, as mentioned above, the ion exchange membrane is laminated with metal, etc. on only one side, and the layer of the fibrous material aggregate is placed on at least the other side. , it is also possible to configure electrodes on both sides of the ion exchange membrane. Note that it is advantageous if the layer of the fibrous material aggregate has a porous or lattice shape to improve fluid flow. The material suitable for the conductive fiber used here generally varies depending on whether it is used for the anode or the cathode. When used as an anode or an inclusion on the anode, platinum group metals or surface Materials such as metals having oxides or carbon are suitable for use.

Further, a known material that is corrosion resistant to the anolyte and has a low chlorine overvoltage may be used by coating or plating the corrosion resistant material. On the other hand, when used as a cathode or an inclusion on the cathode side, a material selected from the group consisting of iron, nickel, a titanium alloy containing at least one of iron and nickel, and a platinum group metal is suitable.

In addition, in the case of water electrolysis using pure water, the cation exchange membrane is acidic, so platinum group metals or corrosion-resistant materials such as titanium, niobium, tantalum, etc. are used on both the anode and cathode sides. Alternatively, one coated with a mixture is preferable. Next, the rigid current collectors disposed on the outermost surfaces will be described.

The current collector is wide enough to conduct electricity over the entire surface of the electrode, and
Of course, the contact surface needs to be smooth and have good conductivity, but it also needs to have many holes and/or grooves to guide the gas generated at the electrode and improve the flow of the electrolyte. It can be either lattice-like or honeycomb-like. In this case, the other effects of the present invention may be reinforced if necessary with a bend-resistant reinforcing material to ensure uniform tightening. In addition, the current collector may have a structure integrated with the end plate of an electrolytic cell, or a partition wall that separates the anode chamber and cathode chamber in a bipolar cell, for example, a structure in which grooves are formed in a grid pattern on the surface of the plate. Good too. The conductivity of the current collector must be at least better than that of the electrode and conductive fibrous material, but the materials used on the anode side include titanium, other valve metals, or platinum based on these materials, Examples include those coated with palladium, rhodium, ruthenium, iridium, or their oxides alone or in mixtures, and in the case of cathodes, iron, nickel, alloys containing at least one of iron and nickel, titanium, and platinum group metals. Examples include metals. Further, in the case of water electrolysis using pure water, since the cation exchange membrane exhibits acidity, it is preferable to use the above-mentioned anode side material for both the anode side and the cathode side. Various methods can be used to integrate the ion exchange membrane, laminated thin film electrode, conductive fibrous material aggregate, and current collector as described above. Although there are methods of tightening the shape, the present invention is not particularly limited to these methods.

The present invention allows the cation exchange membrane to be uniformly and extremely close to the electrode by adopting the configuration described above, and this approach method can be easily implemented, and if an electrolytic cell having the structure according to the present invention is used, It has been found that the final effect is that electrolysis can be carried out at a low electrolysis voltage.

Although the present invention has been described in detail above, the gist of the present invention is that an ion exchange membrane is formed by laminating a water-permeable porous electrode thin film containing metal and/or metal oxide as a main component on one or both sides of an ion exchange membrane. When the electrode thin film of the membrane-electrode assembly is on one side, on the other side or both sides,
Furthermore, when the electrode thin film is on both sides, a thin layer of conductive fibrous aggregates intertwined with each other is disposed on at least one side, and a current collector made of a rigid porous material is disposed on both outer surfaces. The structure consists of water or aqueous electrolytic cells arranged tightly together.

Next, one embodiment of the structure of an electrolytic cell according to the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of the electrolytic cell, in which a water permeable porous metal cell 7 is used as an anode and a porous metal cell 8 is used as a cathode on both sides of a cation exchange membrane 3, which are tightly laminated by a method such as hot pressing.

On the cathode side there is a thin layer 6 of entangled fibrous material, the whole being sandwiched between anode and cathode side current collectors 1 and 2 having outermost water permeable holes 4 and 5. The entire tightening device is omitted because it can be a commonly used one. In the above description, a cation exchange membrane is used as the diaphragm, but it goes without saying that other similar diaphragms such as microbolus membranes can also have the same structure.

[Brief explanation of the drawing]

FIG. 1 conceptually shows a cross-sectional view of the structure of one embodiment of the present invention. The symbols used in the drawings will be briefly explained. 1, 2... Current collector, 3... Cation exchange membrane, 4, 5... Water permeable hole, 6... Intertwined fibers. aggregate of shaped objects, 7, 8...
electrode.

Claims (1)

[Claims] 1. In an ion exchange membrane-electrode assembly in which a water-permeable porous electrode thin film containing a metal and/or metal oxide as a main component is laminated on one or both sides of an ion exchange membrane, when the electrode thin film is on one side, on the side or both sides,
When the electrode thin films are on both sides, a thin film of conductive fibrous aggregates intertwined with each other is disposed on at least one side, and current collectors made of rigid porous bodies are arranged on both outer surfaces of the thin film. A structure of a water or aqueous electrolytic cell, characterized in that it is tightly arranged.