JPS6128035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydrogen generating cathode, particularly a hydrogen generating cathode mainly used for electrolysis, which exhibits an excellent low hydrogen overvoltage in alkaline aqueous solutions such as alkali hydroxides, alkali carbonates, and other alkaline aqueous solutions. Conventionally, as a technique for generating hydrogen gas at the cathode, diaphragm (including porous diaphragms such as asbestos diaphragms and tight diaphragms such as ion exchange membranes) method, electrolysis of aqueous alkali metal salt solutions, etc. have been known. This applies. On the other hand, in recent years, particularly in this type of technology, there has been a desire to reduce the electrolysis voltage from the viewpoint of energy saving, and as part of this, it has been proposed to reduce the hydrogen overvoltage of the cathode. Regarding low hydrogen overvoltage cathodes, electrodes made of various materials have been proposed in the past, but the present inventors have developed a cathode whose surface is electroplated with a nickel bath, and in particular, a cathode in which fine particles made of carbonaceous material are dispersed. As a result of numerous studies conducted on cathodes electroplated from nickel baths, the inventors discovered that a low hydrogen overvoltage cathode with excellent durability could be obtained, leading to the completion of the present invention. The gist of the present invention is that carbonaceous fine particles are dispersed as a bath component during plating, and the main component metals are nickel and cobalt, and copper, chromium, aluminum, tin, zinc, barium, silver, The electrode base material is electroplated using a plating bath containing trace amounts of one or more metal ions selected from platinum, rhodium, iridium, and palladium, and a nickel-cobalt alloy mainly composed of nickel is coated on the surface of the base material. This is a method for producing a hydrogen generating cathode characterized by forming a plating layer containing the following. The plating bath used in the present invention contains nickel and cobalt as its component metals, and further contains carbonaceous fine particles dispersed therein, and copper, chromium, aluminum, tin, zinc, barium, and silver. , platinum, rhodium, iridium, and palladium. Using such a bath, the surface of the electrode substrate is electroplated to form a plating layer containing a nickel-cobalt alloy mainly composed of nickel, and the cathode thus obtained is coated on the substrate. It has an active layer, has a long life, and has a significantly reduced hydrogen overvoltage. Furthermore, this method is extremely advantageous in that the electrodes can be manufactured at low cost without requiring particularly complicated man-hours. The electrode base materials used in the present invention include materials that can be plated with nickel, such as iron, stainless steel, copper, nickel, and alloys thereof, iron plated with nickel, copper, etc., and platinum group metals as valve metals. Or other metals or oxides are applied alone or in combination, and copper is added on top of them.
Any material such as iron, nickel, or other plated material can be used as long as it exhibits some degree of corrosion resistance under the conditions of use. On the other hand, fine particles made of carbonaceous material to be dispersed in the plating bath include charcoal,
Examples include carbons such as coal and bone charcoal, and fine particles such as graphite, activated carbon, carbon black, and coke. In particular, activated carbon made from wood, coconut shell, etc. is advantageous in terms of performance and economy. Such fine particles preferably have a size of 100 μm or less. However, since many commercially available fine particles have a fairly wide particle size distribution, as long as about 50% or more of particles of 100 μm or less are contained, there is no particular problem in achieving the object of the present invention. When dispersing such fine particles in the plating bath,
Its concentration is preferably from 0.1 to 100 g/, particularly preferably from 1 to 20 g/. Even if the concentration of these fine particles exceeds a certain level, it will not have much effect on the hydrogen overvoltage of the cathode obtained. However, if the concentration becomes too high, uniform dispersion becomes difficult and motsuki operation becomes troublesome. Become. When it is sufficiently dispersed under conditions suitable for plating, there is no problem even if the concentration exceeds the above-mentioned preferred upper limit. Furthermore, since the above concentration range also affects the particle size distribution of the carbonaceous fine particles to be dispersed, there is no need to be too particular about the concentration itself. On the other hand, if this concentration is too low, it becomes difficult to obtain the desired low hydrogen overvoltage cathode.
The concentration range described above is desirable. Appropriate stirring is required to disperse such fine particles, and specific methods include gas blowing, liquid circulation, or using a stirrer. In this case, a stirring method using a magnetic stirrer is also recommended. If this stirring is insufficient, a uniform plated product cannot be obtained, and on the other hand, if it is too strong, an active plated product cannot be obtained. In addition, if the plating operation continues for a long time, the carbonaceous particles will be consumed, and many fine particles in particular will be reduced, but in this case, all the particles will be removed using a pre-coating device, etc., and new particles will be generated again. The operation may be performed by adding the amount of water consumed, and if the operation is practiced, the amount consumed can be added. On the other hand, many nickel-metallic baths, including typical nickel-metallic baths such as nickel sulfamate, nickel sulfate, and nickel chloride, do not usually contain only nickel; It contains cobalt in addition to nickel, and the amount is 0.01~
It covers a wide range of 10%. The main component metals in the plating bath used in the present invention are nickel and cobalt, and the cobalt in the conventional nickel plating bath may be used as a component metal, or the cobalt in the conventional nickel plating bath may be used as a component metal. A desired composition ratio can be preferably used by removing cobalt or separately adding cobalt in the form of a water-soluble compound. In addition to the above-mentioned normal nickel plating bath containing cobalt, a plate containing cobalt may be used as a counter electrode during electroplating, and the cobalt dissolved during plating may be used as an alloying component. In this way, the plating bath of the present invention may contain nickel-cobalt as a main component metal at least as a bath component during plating, and the above-mentioned carbonaceous fine particles may be used as the alloy component. Any bath may be used as long as it contains a trace amount of one or more metal ions selected from copper, chromium, aluminum, tin, zinc, barium, silver, platinum, rhodium, iridium, and palladium. The composition ratio of nickel-cobalt is not particularly limited as a plating bath, and in short, the base material is formed by considering plating conditions such as plating temperature, plating current density, counter electrode material, plating liquid PH, and degree of liquid stirring. The bath composition during plating is determined so that nickel is present in a predominant amount as an alloy component on the surface, and the remainder, particularly preferably in the range of 1 to 49% by weight, is cobalt. The composition of the main component metal (nickel-cobalt) on the surface of such a base material can be measured by peeling off and dissolving a part of the plating layer and using a method such as atomic absorption spectrometry. The presence of cobalt in such an alloy has the advantage of providing excellent adhesion of the plating layer to the base material and improving the hardness of the plating layer.
If the amount of cobalt is too small, the above advantages are lost, and if it is too large, the corrosion resistance of nickel tends to decrease, so the above alloy composition range is preferable. In the present invention, it is necessary to further include the following metal ions in the nickel-cobalt bath in which the carbonaceous fine particles are dispersed, namely, copper, chromium, aluminum, tin, zinc, barium, silver, One or more metal ions selected from platinum, rhodium, iridium, and palladium, and by making them present in trace amounts in the entire bath, the activation effect of the obtained cathode is further promoted, This results in a cathode that exhibits a lower hydrogen overvoltage. In this case, the addition of trace metals is preferably 1% by weight or less based on the bath, and the particularly preferred concentration range varies depending on the type of metal, but is generally as follows. Cu〓: 0.5~250ppm, Cr〓 or Cr〓50~2000ppm Al〓: 50~5000ppm, Sn〓: 50~5000ppm Zn〓: 50~5000ppm, Ba〓: 50~5000ppm Ag ⁺ : 50~5000ppm, Pt〓 or Pt〓: 5-3000ppm Rh〓: 5-300ppm, Ir〓 or Ir〓 or Ir〓: 10-3000ppm Pd〓: 1-300ppm, These trace metals should be added in the form of salts to the plating bath. is desirable. These additive metals are generally present in the plating bath in the form of ions, but certain metals may be present in the form of insoluble salts. The plating bath used in the present invention can be based on a normal nickel plating bath as described above. An example of a particularly suitable bath is a bath containing nickel sulfamate or nickel sulfate as a main component.
When carrying out the method of the present invention, plating conditions such as plating bath composition, plating temperature, plating current density, counter electrode plating liquid PH, and stirring of the liquid are related to the plating bath, so a suitable range should be selected. This is desirable. The thickness of the plating is preferably several microns or more, preferably 20 microns or more in terms of cathode life, etc. in terms of pure nickel. In order to further improve the adhesion of these plated materials, the plated surface may be further coated with nickel plating or sulfur-containing nickel plating. Examples of sulfur-containing metals include thiourea, thiocyanate, which precipitates sulfur content in the metal in the nickel metallurgy bath.
Those with added compounds such as thiosulfate and thioglycolic acid, and others can be used. As explained above, according to the method of the present invention, a cathode for hydrogen generation can be manufactured at low cost, and the obtained cathode has a significantly low hydrogen overvoltage cathode and can maintain its activity for a long period of time. Such a cathode is also useful as an electrode for electrolysis of sodium chloride, potassium chloride, etc. using an asbestos diaphragm or ion exchange membrane as a hydrogen generating cathode, and is also sufficiently durable for use in water electrolysis equipment. The present invention will be explained below with reference to Examples. Comparative Example 1 A base material made of a nickel round bar with a diameter of 3 mmφ was
It was etched by immersing it in ~6N HCl at 80°C for 30 minutes. Similarly, a soft iron round bar with a diameter of 3 mm was etched by immersing it in hydrochloric acid of the same concentration at 60°C for 30 minutes. These round bars of the etching solution were electroplated in a plating bath having the composition shown below and under the following conditions. [Metting bath composition] Nickel sulfate 84 g/ Cobalt sulfate 5 g/ Nickel chloride 30 g/ Ammonium chloride 4.5 g/ Potassium chloride 6 g/ Boric acid 30 g/ Fine granular activated carbon (KV-3 100μ manufactured by Futamura Kagaku KK)
Contains 70% or more of the following particles) 5 g/ [Plating conditions] Plating bath PH 3.5 Counter electrode graphite temperature 40℃ Plating current density 2A/dm ² Plating time 2 hours Regarding the plated product obtained as above, 20%
As a result of measuring the hydrogen generation potential with Hg/Hgo electrode reference in KOH solution at 60℃ and 200A/ ^dm2 , Ni round bar -1.14V,
Soft iron round bar −1.15V was obtained. Example 1 Pt, Rh,
Electroplating was performed in the same manner as in Comparative Example 1 using each plating bath to which Ir and Pd were added. The results were as shown in Table 1.

[Table] Example 2 A base material made of a nickel round bar with a diameter of 3 mmφ was
Etching was performed by immersing in 6H-HCl at 80°C for 30 minutes. Similarly, a 3 mm diameter soft iron round bar was etched by immersing it at 60°C for 30 minutes. After this etching, electroplating was performed under the following plating conditions using a plating solution having the composition shown below and a plating bath in which a trace amount of a metal component was added to the plating bath. <Metting bath composition> Nickel sulfamate 300 g/ Cobalt sulfamate 0.1 g/ Nickel chloride 5 g/ Boric acid 40 g/ Fine granular activated carbon (KV-3 manufactured by Nimura Kagaku KK, containing 70% particles of 100 μ or less) 5 g/ <Plating conditions> Plating bath PH 3.6 Mating electrode plate containing 99.0% Ni and approximately 1% Co Temperature 40℃ Plating current density 2A/dM ² plating time 2H

[Table] Each plated material is 20% KOH 60℃ 20A/dM ² Hg/
Hydrogen evolution potential was measured with a HgO reference electrode. The measured results are shown in Table 2. As is clear from these results, it can be seen that the inclusion of trace components results in a lower overvoltage. The Ni-Co alloy composition on the plated surface is approximately
It was 98.5% Ni and 1.5% Co.

[Table] Example 3 The same material as Comparative Example 1 was used, with the addition of trace metals, and electroplated using the following plating bath and conditions.
Obtained the results in the table. <Plating bath composition> Nickel sulfate 84 g/ Nickel chloride 30 g/ Ammonium chloride 4.5 g/ Potassium chloride 6 g/ Boric acid 30 g/ Fine granular activated carbon (KV-3) 5 g/ <Plating conditions> Plating bath PH 3.5 Plate temperature containing 90% Ni and 10% Co: 40℃ Plating current density: 2A/dM ² plating time: 2H

[Table] The Ni-Co alloy composition on the plated surface is approximately
It was 90% Ni and 10% Co. Example 4 Each plated product obtained by adding trace metals in Example 2 was further electroplated using the following plating bath and conditions. <Plating bath> Nickel sulfate 84 g/ Nickel chloride 30 g/ Ammonium chloride 4.5 g/ Potassium chloride 6 g/ Boric acid 30 g/ Thiourea 5 g/ <Plating conditions> Plating PH 3.5 Counter electrode 99.9% Ni plate temperature 40 Plating electric density 2A/dM ² Plating time 10 minutes The potential after plating of each plated object obtained in this way is
Shown in the table.

[Table] From the above data, the potential hardly changed, and the adhesion strength of the plated material increased. Therefore, it is expected that mechanical peeling of plating materials will be reduced.

Claims (1)

[Claims] 1 As a bath component during plating, carbonaceous fine particles are dispersed, and the main component metals are nickel and cobalt, and copper, chromium,
The electrode base material is electroplated using a plating bath containing a small amount of one or more metal ions selected from aluminum, tin, zinc, barium, silver, platinum, rhodium, iridium, and palladium. A method for manufacturing a cathode for hydrogen generation, characterized by forming a plating layer containing a nickel-cobalt alloy mainly composed of nickel on the surface of the material.