JPS5967380A - Cathode for generating hydrogen - Google Patents

Abstract

PURPOSE:To provide a titled inexpensive cathode having high adhesion and strength of a melt spraying material and an excellent low hydrogen overvoltage characteristics, by forming an underlying layer by sulfurous nickel plating on a cathode base material, and forming the coating layer of the nickel-contg. melt spraying material thereon. CONSTITUTION:A compd. which codeposits sulfur such as thiourea or the like is added into a nickel plating bath such as nickel sulfate by which the surface of a cathode base material of iron or the like is plated, and the underlying coating by the sulfur-containing nickel plating is thus applied on the surface. A coating layer of a nickel-contg. melt spraying material is formed thereon, whereby the cathode for generating hydrogen having high adhesion and mechanical strength of the melt spraying material, high corrosion resistance, porosity and a low hydrogen overvoltage is inexpensively obtd. A melt spraying material which consists essentially of a nickel metal and/or a nickel compd. of the oxide thereof, etc. and is further added with metals such as Al, Ti, Fe or the like or the compd. thereof is used according to need.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode for hydrogen generation, which has an excellent low hydrogen permeability.
This relates to a cathode mainly used for electrolysis, which has E-pressure characteristics.

Conventionally, diaphragm (
Electrolysis of aqueous solutions of alkali metal salts using porous furnace diaphragms such as asbestos, and tight diaphragms such as ion exchange membranes is known, and water electrolysis also falls under this category.

In recent years, there has been a desire to reduce the electrolysis voltage in this type of technology, mainly from the viewpoint of energy conservation, and various active cathodes have been proposed as a means for reducing the electrolysis voltage.

Such active cathodes are typically made by spraying, pyrolyzing, or melting a layer of an active metal material with a reduced hydrogen overpotential onto the surface of an alkali-resistant substrate such as iron, copper, nickel, and their alloys, or pulp metal. Objects are coated by immersion electroplating, chemical plating, and other methods, and each of these coating methods has advantages and disadvantages. Among these, the formation of a cathode active coating by thermal spraying usually results in a film with a porous structure in which flat particles are deposited in layers, and this is said to contribute effectively to cathode activity, but adhesion to the substrate is not always a concern. It cannot be said that the mechanical strength is sufficiently satisfied.

As a result of various studies regarding the thermal sprayed cathode, the present inventors found that the drawbacks of the thermal spraying method can be corrected by subjecting the base material to a surface treatment prior to thermal spraying.
The cathode of the present invention was completed.

That is, in the present invention, the cathode base material is coated with sulfur-containing nickel plating, and then the nickel-containing thermal spray material is coated with jl'2.
One pole for hydrogen generation formed by the color layer τ is used as an edge.

As mentioned above, it is very advantageous to use a 11" cathode material directly on the base material because it increases the surface area and has a greater effect on lowering the current density. However, from the point of view of adhesion and strength, As a way to prevent this corrosion, after spraying,
There is a method of heat-treating to a high temperature to reduce all the exposed parts (-f), but there is a drawback that heating to a high temperature makes the exposed part a little more porous, resulting in a higher hydrogen overvoltage; If the amount of the substrate is insufficient, the base material (again, Ill-F is good, but this is difficult to adopt from an economic point of view).

Hitoshi and well 1 are used to prepare the surface for nickel plating.
As a result, breaking the F1 coating by electroplating using a sulfur-containing nickel plating bath improves the adhesion of the next nickel sprayed material, which is extremely advantageous as it does not expose the material. We have come to confirm this.

In the present invention, the cathode base materials used include iron, stainless steel, copper, nickel, and composites containing these materials, and the base layer on which the sulfur-containing nickel plating is formed is formed on the base material. Plating is carried out using a nickel plating bath, e.g. @t[Nickel, sulfamine, nickel chloride, etc. Compounds that eutectoid sulfur in general-purpose nickel plating baths, e.g. thiourea, rhodan salts, thiocyanates, thiosulfates. , thioglycolic acid group, etc. can be used (-5 electroplating (C) to easily form the oxidation layer.

The components of the thermal spraying that is carried out next to such a base coat (mainly nickel gold 1 and 4 from the viewpoint of corrosion resistance) are
and/or 1. The nickel compound preferably contains nickel compounds such as oxides, sulfides, carbides, borides, and nitrides.

In addition, as components other than nickel, in order to increase the catalytic performance for reducing the hydrogen JM voltage, and to increase the surface area,
In order to improve the adhesion of the sprayed material, and to improve the strength of the sprayed material, various other metals may be used for various purposes such as adjusting all 41 points of the sprayed material. There are a wide variety of materials used for this purpose, but typical examples include sacrificial metals such as aluminum, zinc, and molybdenum, and pulp gold such as titanium, niobium, and tantalum.・4.Many metals such as iron group metals such as iron and cobalt, as well as sulfides, carbides,
There are borides, male oxides, barium hydroxide, barium hydroxide, etc.
Water f'ff2 compounds and chlorides such as magnesium chloride can also be added.

Generally, the diameter of the sprayed particles is preferably 0.01
~50μ, and a more suitable size is in the range of 1~10μ. In this case, these particles having different particle size distributions can be thermally sprayed in a layered manner, or they can be mixed and thermally sprayed.

Generally speaking, the sulfur-containing nickel plating layer for base treatment is 5
It is preferable to have a thickness of μ or more, but in consideration of cost etc., a range of 10 to 200 μ is more preferable. The thickness of the nickel-containing thermal spray coating to be thermally sprayed onto the surface of the base layer is preferably 10 to 500 .mu.m, and usually about 100 .mu.m is particularly preferably used.

Thermal spraying of these particles is easily accomplished by means such as flame spraying or plasma spraying.

The coating components used in thermal spraying include alloy powders, alloy linear bodies, and mixtures of alloy powders.Flame spraying using these components is performed in the flow of a combustion flame formed by flammable or oxidizing gases. Melt sprayed. Also, plasma spraying uses argon or 9. An inert gas such as LP= is melted and atomized in a plasma stream generated by heating with an all-electric arc at high temperatures.

According to the above research, it is possible to obtain an extremely strong and excellent shade at a low cost by completely forming a coating on the base material by I) predetermined plating and thermal spraying.

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

Examples 1 to 1G and Comparative Examples 1 to 14 Wire diameter 3.2mmφ
The following process was carried out using a round bar made of soft iron and pure nickel.

That is, first, these round bars were sandblasted using 300 mesh passes of sand, and then sandblasted with 20% HC1 at 80%.
After etching at ℃ for 10 minutes, these materials were subjected to a base treatment as shown in Table 1. Except for those that are not treated, base treatment is performed by simple nickel plating or base treatment by sulfur-containing nickel plating,
All of these treated and untreated materials were thermally sprayed using flame spray.

The base treatment with sulfur-containing nickel plating was as follows.

[Plating bath composition]

Nickel sulfate 849/ Nickel chloride 30 z Ammonium chloride 4,5 Potassium chloride
61 boric acid
30 Thiourea 5
N [Plating conditions] Plating bath pH 4 Mating electrode Nickel temperature
40℃ Plating current density 2 A/dtt
t' plating time Z hr
Further, the base treatment by simple nickel plating was carried out under the same plating conditions as above using a bath in which thiourea was removed from the sulfur-containing nickel plating bath composition.

Thermal spraying was performed under conditions of melt spraying using air so that the sprayed material had a predetermined thickness.

All round bars after thermal spraying were immersed in 301 NaOH at a temperature of 80°C for 6 hours, thus obtaining a
Regarding the skin covering, the hydrogen generation potential at the current density of 1f20A/peak in 20% KOH at 60℃ is I-Tg/]
Measured based on TgO. (initial potential), then 80°C,
30% Na0J (current density Iff 100Mdt
r? Hydrogen generation was carried out for 100 hours using a nickel plate as an odor partner, and the hydrogen generation potential was measured again under the same conditions as above.

These are shown in Table 1, and from the results, comparative examples (comparative examples 4t8 to 11.13) in which thermal spraying was directly formed on the soft iron base material
．． 14) showed the greatest performance deterioration compared to the round bars of each example, and the comparative example (comparative example 216) in which the nickel base material was directly sprayed, and the nickel base treatment on the soft iron base material or nickel base Murakami. Comparative example (Comparative example 1.
3. 7°12), it can be seen that the performance of the round bar of the example is excellent.

Claims (1)

[Claims] 1. A cathode for hydrogen generation comprising a base coating of sulfur-containing nickel plating and a coating layer of nickel-containing sprayed material on the cathode base material.