JPS6141785A - Manufacture of active cathode - Google Patents

Abstract

PURPOSE:To stabilize plating operation and to obtain easily a cathode having low hydrogen overvoltage by carrying out electroplating with a plating bath for essentially depositing nickel while supplying fine solid particles having a particle size distribution in which the small particle size part is dense. CONSTITUTION:A plating bath for essentially depositing nickel is prepd. The plating bath contains dispersed fine solid particles having >=10mum width of the particle size distribution. A cathode substrate is electroplated with the plating bath, and in accordance with the progress of plating, fine solid particles having a particle size distribution in which the small particle size part is denser than that in the particle size distribution of said fine solid particles are supplied.

Description

Detailed Description of the Invention (1) Structure of the Invention (Field of Industrial Application) The present invention provides an active cathode with low hydrogen overvoltage characteristics suitable for electrolysis of aqueous alkali chloride solutions or water electrolysis. This relates to a manufacturing method.

[Conventional technology]

Electrolysis of aqueous solutions of alkali metal salts is known, and water electrolysis also falls under this category.

In recent years, from the perspective of energy conservation, there has been a desire to reduce the electrolysis voltage in this food technology.

Various active cathodes have been proposed as a means for reducing the electrolysis voltage.

Such active cathodes are typically made by thermally spraying a layer of an active metal material with low hydrogen overvoltage characteristics onto the surface of an alkali-resistant substrate such as iron, copper, nickel and their alloys, or pulp metal.
It is obtained by coating by means such as pyrolysis, immersion in a melt, electroplating, chemical plating, vapor deposition explosion deposition, etc., and, among other things, forming fine irregularities on the surface of this active metal material layer to create a porous and rough surface. In addition to the inherent electrochemical catalytic action of the active metal material layer, attempts have also been made to create an active surface that is more effective in reducing hydrogen overvoltage by increasing the active surface area.

An active cathode has also been proposed in which a plating bath in which solid fine particles are dispersed is used as the active cathode, and the solid fine particles are plated on the surface of a cathode base material together with an intermediate plating metal component. (For example, Japanese Unexamined Patent Publication No. 57
-35689゜57-89491, 57-945
82, 57-94583, etc.).

[Problems that the invention attempts to resolve]

The performance of the hydrogen generating cathode obtained in this way has shown remarkable progress, but on the other hand, it has been possible to manufacture the cathode more efficiently, at a lower cost, and with excellent long-lasting activity. It is also essential to do so. As a practical matter, when manufacturing electrodes, %<, 2> is efficiently carried out, and 2 is, for example,
This is an important issue that cannot be ignored, as it is reflected in the overall cost required for aqueous alkali electrolysis.

The present invention aims to improve the plating efficiency and reduce the manufacturing cost in the method for manufacturing a cathode using the above-mentioned dispersion plating.

[Means for determining the problem]

The present invention provides an excellent low hydrogen overvoltage cathode that can significantly reduce costs and stabilize the plating operation when producing an active cathode by electroplating using a plating bath in which solid fine particles are dispersed. This is a method that can produce.

The plating bath in the present invention is a plating bath containing a plating component in which the main metal component to be plated is nickel, and in which solid fine particles are dispersed. Electroplating is applied to.

As mentioned above, plating using a plating bath in which solid fine particles are dispersed is generally referred to as dispersion plating.The method of the present invention mainly aims at improving the efficiency of plating by specifying the solid fine particles in such dispersion plating. This is what we do.

As the cathode base material used in the method of the present invention, a corrosion-resistant metal material that does not particularly impede the adhesion of plating is used, specifically iron and copper.

Alkaline earth metal materials such as nickel, alloys containing these, and valve metals are preferably used, and metal materials that have been previously plated with nickel or the like may also be used.

There is no limit to the shape of *, but expanded metal, perforated flat plates made of pressed metal, perforated metal, woven wire mesh, and other perforated plate shapes are preferably used, and their porosity is It is preferably in the range of 1 to 99 inches.

The plating bath used in the present invention deposits a metal mainly composed of nickel on the above-mentioned current-carrying cathode substrate, but it may also contain cobalt, molybdenum, iron, tungsten, aluminum, etc. as components other than nickel. I can do it. However, due to its corrosion resistance, nickel is the main ingredient.

As long as there is no significant effect, a simple method is desired from the viewpoint of plating bath management.

The main component is nickel.For example, nickel sulfate.

Nickel chloride, sulfamic acid dichloride, etc. are added in the form of ammonium or its salt, boric acid or its salt, citric acid or its salt.

Birophosphate, alkali chloride, etc. are added to form the bath. The solid particles to be dispersed include metal powders such as nickel, cobalt, silver, and Raney nickel, nickel oxide, and zirconium oxide.

Oxides such as molybdenum oxide and rhodium oxide.

Examples include carbides such as tungsten carbide and silicon carbide, sulfides such as nickel sulfide and molybdenum sulfide, other nitrides, and carbon. Some of these solid fine particles have a low hydrogen overvoltage by themselves, and some have a lower hydrogen overvoltage when subjected to dispersion plating.

In the method of the present invention, the particle size of the solid fine particles is 0.01 to
Preferably, the size is 100μ.

It can also be used even if it contains particles with a larger particle size, but
On the other hand, a particle size distribution with a narrow width is not good;
Those with a wide distribution of μ or more are used.

If solid fine particles with a particle size distribution width of less than 10 μm are used, a plated product can be obtained, but the hydrogen overvoltage may deteriorate, the plating may be unevenly adhered, or particles may be too large or too small, so it is difficult to plate. The distribution of solid particles in the bath is lOμ
It is necessary that it is above.

In the present invention, plating is performed using a material having such a distribution of solid fine particles.

At a certain bath volume, the plating area increases (2) For example, when plating a net-shaped base material, as the number of plated sheets increases, the adhesion of the plating becomes worse. Therefore, removing the remaining solid particles from the plating bath and adding new solid particles during the plating bath requires labor and processing of the removed solid particles. By significantly reducing these update frequencies, a significant reduction in system costs is expected.

For this purpose, solid fine particles are added as plating progresses, but if particles with the same particle size distribution as the bath are added, the particle size distribution of the bath will gradually differ, and many of the particles will be added in the same bath. It will no longer be possible to plate it. Surprisingly, problems can be caused by adding solid particles whose particle size distribution is biased toward finer particles than the particle size distribution of the solid particles used at the beginning of the plating bath and proceeding with air plating. I found out that it can be resolved.

In this case, there is no particular limit to the degree of deviation of the particle size distribution, but it is not preferable that the two particle size distributions do not overlap and are completely separated from each other. It is preferable that the solid fine particles are reduced by about 1/2 to 1/10.

In this case, it is preferable to add particles having a finer particle size distribution than that of the solid particles measured by peeling off the plating of the plated object.

By adopting this method, the consumption of solid fine particles is reduced by approximately 1/10 to 1/1000.

The amount of these additions is preferably about 1.5 to 6 times the amount of the plated material deposited, and the reason why the amount is greater than the amount of the plated material is that they simply adhere and come out of the plating bath.

This is because some of the precipitated material is peeled off and deposited in the plating bath.

[Effect]

In the method of the present invention, by using solid fine particles with a particle size distribution width of 10μ or more, and by using solid fine particles whose particle size distribution shifts toward finer particle sizes than the solid fine particles as plating progresses, it is possible to achieve appropriateness. The reason why such dispersion plating can be achieved is clear and unambiguous.

However, the finish of dispersion plating is clearly different between when solid particles are added and when they are not.
In the former case, a plated layer with a dense surface is obtained, whereas in the latter case, a plated product with a rough surface and relatively easy to peel is obtained, which is due to the electrophoretic action of solid particles. It seems to be.

〔Example〕

This will be explained below using Examples and Comparative Examples.

Example l Lath net made of 5U8310S (6swx12Lwx1.5
TX1.8W, unit m; SW is the length of the mesh in the transverse direction, LW is the length of the mesh in the longitudinal direction, thickness, and W is the width of the cut. Base material (1dtlt (100aX100+a+)) 2 with flattened both sides of (same below) by pressing
Plating was performed using the following process using 0 sheets.

■Trichlorethylene cleaning→■Electrolytic etching−■Water washing−■Strike Metkey ■Water washing−■Dispersion Metkey ■Water washing→■Dispersion Metkey ■Water washing The chemicals used and operating conditions for the main parts in this process are as follows.

1) Electrolytic etching (process ■) [Etching solution] Sulfuric acid 3009/surfactant 1-21/ solution -ii 5t [Conditions] Temperature 5-20°C Current density 3 A/d -4 Cathode used
Pb plate (1d, r) Time: 6 minutes 2) Strike plating (process ■) [Plating solution] Nickel chloride 100g/Hydrochloric acid 1001/Liquid amount 5t [Conditions] Temperature 5-20℃ Current density 3A/d Anode Ni plate Time 3 minutes 3) Dispersion plating (processes ■ and ■) [Plating solution] Nickel sulfate 8411/L Nickel chloride 30 l Ammonium chloride 4.51 Potassium chloride 61 Boric acid 30 1 Copper sulfate 0.41 Activated carbon (Initial charge) 15 I liquid amount 5t [Conditions] Temperature 30-60℃ Current density 20 people/ltwt Time 10 minutes Anode Ni plate (liquid stirring performed by pump) [Operation] Using the above plating bath, After plating one screen, add additional activated carbon (same as the initially charged activated carbon) using a ball mill to add 48.
Time-pulverization) 12I was replenished, copper sulfate in the bath was analyzed and the shortage was replenished, and 20 lath nets were plated in this way. In this case, the particle size distribution of the initially charged activated carbon was as shown in FIG. 1, and the particle size distribution of the additional activated carbon was as shown in FIG.

There was no difference in the appearance of the 20 plated products obtained through the above two-step plating process.

Also, potential measurement (20 cm KOH, room temperature, 'lQA/dtd
(measured by directly contacting the Luggin tube with the back of the lath mesh using Hg/Hg O as the reference electrode) is -1,01 to -1,04.
None showed abnormal potential within the range of V.

Comparative Example 1 A plated product was obtained in the same manner as in Example 1, except that activated carbon was not added.

As a result, a change in appearance was observed from the 5th layer of the lath net, and 1
When the 0th plate was reached, the plated plate was non-uniform with particles of large size partially attached to the surface. The potential is -x, oz-X, o4v for 1st to 2nd sheets, 9 to 10 sheets 1〈06 to 5 os
v was shown.

9 of the 1st and 10th samples in 3Q% NaOH
48H hydrogen generation at 0@c, 50A/dM8.

When I measured the potential again, the first one was & 1.01V.
, the 10th sheet showed -1.11V, and there was a significant difference in performance.

Example 2 Same material and shape as Example 1, one area is 804M” (70
Plating was performed using a lath net of 0x1140+wa) in the following steps. What is the composition of the plating bath?

The same steps are the same as in Example 1.

■Trichlorethylene cleaning → ■Electrolytic etching → ■Water washing → ■Strike Metski ■Water washing → ■Dispersion coating → ■Water washing → ■Nickel sulfur plating → ■Water washing → [Dispersion Metski Co., Ltd.] Dispersion Metski @Water washing -〇Nickel Sulfur Metski ◎Water washing - ■ Perform dispersion key ■ Washing with water, perform ■ electrolytic etching in a 0.3M' plating bath, and after washing with water, ■
Strike plating was performed.

After washing with water, apply dispersion plating at 5 A/d M” x 20
After washing with water, apply 5A/nickel sulfur plating.
dM”X I went for 20 minutes.

Dispersion plating was performed three times as described above, and finally nickel sulfur plating of [phase] was performed for 5 A/aM' x 40 minutes.

The activated carbon used here was the same as in Example 1, and after plating one sheet, copper sulfate was analyzed and the missing amount was added. Also, 100 J' of finely ground activated carbon was added.

In this way, I made 36 pieces of 2-pass netting.

No abnormality was observed in appearance. Then the second and third
5th sheet l) When I cut out the ldMt and analyzed the amount of plating attached, the second sheet was 9.5 ~ 10.31/1M".
The 35th sheet is 9.7 to 10.1 #/dMl, and the analysis result of the carbon content in this plated material is 3.8 to 4.
The 2nd and 35th sheets were 3.9 to 4.3%. The potential is 1
-1.02~-1.04V 35th piece -1.02~
No change was observed at -1.05V. Also attached 2
The results of measuring the particle size distribution of the 35th and 35th sheets are shown in Figure 31 and Figure 4. Looking at this, almost no change in particle size distribution is observed.

Example 3 In the same process as in Example 1, solid particles in the dispersion plating bath were treated with Raney nickel ao y/za (Ntss%At45%
Dispersion plating was performed except for M acid copper.

The particle size of the initially charged Raney nickel was 6-8 microns on average, with the smaller particle size being 1 micron and the larger particle size being 24 microns. Also, the particle size of additional Raney nickel is 3-4 on average.
The smaller particle size was 1 μm or less, and the larger particle size was 12 μm. This additional Raney nickel is 1dMJ
Five sheets were plated with an additional 55 g per sheet. The potential of the first sheet was -1.07V, and the potential of the fifth sheet was -1.08V, and no difference was observed in appearance.

〔Effect of the invention〕

According to the present invention, excellent dispersion plating can be achieved by a simple method of simply adding additional solid particles whose particle size distribution is shifted to a finer particle size side for the particle size distribution of the initially charged solid particles. It is possible to obtain high quality active cathodes,
This makes it possible to save on solid particles and mass-produce active cathodes.

In addition, there is an advantage that an active cathode of constant quality can be manufactured at low cost by this method, and the present invention has no utility value in these respects.

[Brief explanation of the drawing]

Figures 1 and 2 are histograms showing the particle size distribution of the solid fine particles used in Example 1. This shows the case of fine particles. Figures 3 and 4 are histograms showing the particle size distribution of solid fine particles in the plating formed on the dispersion plating active cathode obtained in Example 2. Figure 3 is the second diagram of the cathode manufacturing order. Regarding this, Figure 4 also shows the 35th picture.

Claims (1)

[Claims] 1. Electroplating is performed on the cathode substrate using a plating bath containing a plating component in which the main metal component to be plated is nickel and in which solid fine particles are dispersed, and the width of the particle size distribution is Activation characterized by performing electroplating using the above-mentioned solid fine particles having a diameter of 10μ or more, and adding solid fine particles whose particle size distribution is biased toward a finer particle size side than the particle size distribution of the solid fine particles as plating progresses. Method of manufacturing a cathode.