JPS5824932Y2 - Cathode for electrolysis - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of an electrolytic cathode, particularly a cathode that generates hydrogen.

This cathode is used industrially for water electrolysis or alkali chloride electrolysis using a diaphragm method.

= Commonly used cathodes that generate hydrogen include iron,
Available in stainless steel and nickel.

Nickel, cobalt, platinum group metals, and other metals are known as materials with lower hydrogen overvoltage than iron.

There are two ways to reduce the hydrogen overvoltage: one is based on the material, and the other is by changing the structure of the cathode.

In terms of materials, methods such as plating with a specific alloy or adding additives to the plating bath have been proposed.

On the other hand, as a method of changing the structure of the cathode, for example, in a broader sense, it is mainly considered to increase the effective area of the electrolytic surface and improve the gas venting effect.

One way to increase the effective area is to make the electrolytic surface porous.
For example, an alkali-insoluble metal and an alkali-soluble metal are attached to an electrolytic surface, and then the soluble metal is removed from the electrolytic surface to obtain a porous electrolytic surface.

In some cases, wire mesh with small mesh openings was used for chlorinated alkali electrolysis using the diaphragm method.

The purpose of the present invention is to obtain a cathode with low hydrogen overvoltage by changing the structure of the cathode.

According to the present invention, by attaching a second porous cathode on top of the commonly used porous cathode in an appropriate manner, the electrolytic area of the cathode can be greatly increased and the hydrogen overvoltage can be reduced. It's something you're trying to gain.

Furthermore, by selecting a material with a lower hydrogen overvoltage for the second cathode, the entire cathode can have an extremely low hydrogen overvoltage.

Even if the material has a low hydrogen overvoltage, there is no material that can maintain a low hydrogen overvoltage forever, so it must be removed from time to time and replaced with a new one.

Therefore, it is necessary that the second porous cathode can be easily removed or detached.

Examples of attachment methods for this include using an alkali-resistant conductive adhesive, screwing, or spot welding.

Conventionally, it was thought that using a structure in which two cathodes are stacked one on top of the other, as in the present invention, would actually make degassing worse and produce the opposite effect.

However, the above-mentioned adverse effect does not occur when stacking items of the same shape or dimensions, such as netted or lath nets with an aperture ratio of 25 to 70, or round rods, or of different shapes. was discovered.

In particular, it is preferable to use a net made of a material with a low hydrogen overvoltage.

If two punching plates are used, the result will be much worse than the above-mentioned net, lath net, or sagging round bar, and if one of the punching plates is used, the results will be the same.

Here, the term "punching plate" refers to a plate with punched holes in a circular or other shape.

The present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the cathode chamber wall 1 is generally made of iron, stainless steel, nickel, or the like.

2 is a conductive lead for electrical connection.

A rib 3 is welded to the inner wall of the cathode chamber, and a cathode 4 is attached to the rib.

A spacer 7 is inserted between the cathode 4 and the diaphragm 6,
The distance between the diaphragm and the cathode should be equal.

The diaphragm is held in place via a gasket 5.

FIG. 3 explains the structure according to the present invention as a partial sectional view, and shows the main part where a porous second cathode 8 with a low hydrogen overvoltage is attached to the side of the conventional cathode 4 facing the anode. It shows.

Both FIGS. 4 and 5 show an example in which the second cathode 8 is attached to the first cathode 4 according to the present invention.

In FIG. 4, the first cathode 4 is welded to the side surface of the rib 3, the surface of the first cathode 4 facing the anode and the end surface 9 of the rib 3 are on the same plane, and the second cathode 8 is welded to the side surface of the rib 3. Spot welding is performed on the end face 9.

FIG. 5 shows a modification of the attachment method in which the second cathode is attached to the plate-shaped portion 10 of the second cathode with screws 11 instead of spot welding.

The present invention will be explained below with reference to Examples.

A soft iron lath mesh was used as the first porous cathode.

The dimensions of the lath net are 13 x 6 x 1.5 x 1.5 m
/m (longitudinal stitch distance x transverse stitch distance x feed width x board thickness) (Example 1).

The same material was attached as a second cathode on this lath mesh by spot welding (Example 2).

Similarly, a nickel lath mesh (13x6
x1.5 x 1 m/m ) was attached by spot welding (Example 3).

0.05μ of a mixed solution containing ruthenium chloride and nickel sulfate was applied to this nickel lath mesh and heated to 450°C for 1
A cathode fired in air using an electric furnace was attached as a second cathode by spot welding (Example 4).

The dimensions of the above electrodes are all 23 dM2, and using Nafyon 336 (registered trademark) manufactured by DuPont, 20% KOH is supplied to the cathode chamber and brine to the anode chamber.
Electrolysis was carried out at a temperature of 25 A/dM2 at a current density of 25 A/dM2.

A spacer made of polypropylene with a mesh size of 10 m/m and a thickness of 1 m/m was placed on the surface of the cathode, and the anode side was pressurized to 1 M with a water column for operation.

The reason for pressurizing the anode side was to keep the diaphragm and cathode surface constant.

A Luggin tube was then placed on the membrane surface on the anode side, and the potential between the cathodes was measured using the Amagi electrode as a reference.

The potential was measured as follows, and the average value of each of the three locations is shown.

Examples Average potential 1 (control) 2.45V 2 (control) 2.41V 3 (this invention) 2.37V 4 (this invention) 2.27V In case of example 4, tap the spot weld lightly with a chisel to remove it.
New nickel lath mesh (coated with Ru and Ni)
was attached again by spot welding and the potential was measured in the same manner, and it was found to be 2.25.

From the above, if there are two reticular cathodes stacked together, rather than one reticular cathode,
Furthermore, it is clear that if the overlapping second cathode network is made of a material with a low hydrogen overvoltage, the hydrogen overvoltage will further drop.

[Brief explanation of the drawing]

FIG. 1 shows a vertical cylindrical view of the cathode chamber and cathode of a conventional electrolytic cell. FIG. 2 is an enlarged view of section A in FIG. 1. FIG. 3 is a partial sectional view showing the structure of the cathode according to the present invention. FIG. 4 is a horizontal sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a partial sectional view showing a modification of the second cathode mounting method of the present invention. In the figure, 1 is the cathode chamber wall, 2 is the conductive lead, 3 is the lip, and 4
is a cathode, 5 is a packing, 6 is a diaphragm, 7 is a spacer, 8
9 is a second cathode, 9 is an end face of the rib, 10 is a plate-shaped portion of the second cathode, and 11 is a screw.

Claims (1)

[Scope of utility model registration request] In an electrolytic cell in which an electrochemical reaction is carried out between an anode and a cathode, another hydrogen overvoltage is placed on the side of the porous cathode facing the anode. An electrolytic cathode characterized in that it is attached so that it can be attached or detached.