JPH101795A - Low hydrogen overvoltage cathode and its manufacturing method - Google Patents

Abstract

(57) [Summary] The object of the present invention is to provide a method for electrolysis of water or electrolysis of an aqueous solution of an alkali metal chloride such as sodium chloride, which has a sufficiently low hydrogen overpotential and can be used for a long period of time. An object of the present invention is to provide a cathode capable of maintaining hydrogen overvoltage performance and a method for manufacturing the same. An electrode in which an alloy layer comprising at least cobalt and tin is coated on the surface of a conductive base material, wherein the tin content in the alloy layer is 0.01 to 95% by weight. Using a hydrogen overvoltage cathode and a plating bath containing cobalt ions and tin ions and a complexing agent, co-depositing at least cobalt and tin on the surface of the conductive substrate, and a method for producing a low hydrogen overvoltage cathode, A method for using a low hydrogen overvoltage electrode, wherein the hydrogen overvoltage cathode is used for electrolysis of water or aqueous solution electrolysis of an alkali metal chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low hydrogen overvoltage cathode used for electrolysis of water or an aqueous solution of an alkali metal chloride such as sodium chloride, and a method for producing the same.

[0002]

2. Description of the Related Art The water or alkali metal chloride aqueous solution electrolysis industry is a multi-power-consuming industry, and various technologies for energy saving are being developed. The means of energy saving is to substantially reduce the electrolytic voltage consisting of the theoretical decomposition voltage, solution resistance, diaphragm resistance, anode overvoltage, cathode overvoltage, etc. Because of its morphology, it has attracted many researchers and has been developed. In the ion exchange membrane method of salt electrolysis, attention has been focused on reducing anode overvoltage, and as a result of vigorous research and development, an electrode with excellent durability and almost no anode overvoltage problem has been completed. It has been widely used industrially.

On the other hand, many proposals have been made on a so-called low hydrogen overvoltage electrode for reducing a cathode overvoltage. Electrodes capable of reducing the voltage by 200 to 250 mV with respect to an iron cathode having a hydrogen overvoltage of 400 mV, for example, JP-A-59-25940 or JP-A-6-146.
No. 046, a hydrogen storage alloy or a platinum group oxide adhered to the surface of an electrode substrate,
No. 9130 discloses an electrode base material in which an alloy coating layer of a transition metal such as iron, cobalt, nickel or the like and tungsten or molybdenum is electroplated. However, the former electrode, on which a hydrogen storage alloy or platinum group oxide is attached, is relatively expensive, so the production cost is high.The alloy coating according to the latter patent is low in production cost, but the hydrogen overvoltage performance is small. Characteristics are not sufficient, and the performance is deteriorated quickly.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for electrolysis of water or electrolysis of an aqueous solution of an alkali metal chloride such as sodium chloride. An object of the present invention is to provide a cathode capable of maintaining hydrogen overvoltage performance and a method for manufacturing the same.

[0005]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies on plating films of binary alloys. As a result, binary alloys of cobalt and tin in a specific composition region are excellent. It has been found that they exhibit low hydrogen overvoltage characteristics and durability, and have led to the present invention.

That is, the present invention relates to an electrode in which an alloy layer comprising at least cobalt and tin is coated on the surface of a conductive base material, wherein the tin content in the alloy layer is preferably 0.01 to 95% by weight. Is preferably 0.1 to 15% by weight using a cathode having a low hydrogen overpotential and a plating bath containing cobalt ions, tin ions and a complexing agent, preferably cobalt ions, tin ions and a complexing agent. The present invention relates to a method for producing the above-mentioned cathode by co-depositing at least an alloy layer of cobalt and tin on a conductive substrate using a plating bath further containing a protein compound in a plating bath containing

[0007] More specifically, an electrode of an alloy layer containing at least cobalt and tin and having a tin content of 0.01 to 95% by weight in the composition range described in claim 1 of the present invention is used. Thus, for example, 90 ° C.
In a 2.5% aqueous sodium hydroxide solution, 40 A /
A low hydrogen overvoltage performance of 100 to 160 mV is obtained at an electrolysis current density of dm ^{2, and} the composition range according to claim 2, that is, an alloy layer having a tin content of 0.1 to 15% by weight. 100-130 m by using electrodes
Excellent low hydrogen overvoltage performance of V is obtained.

This alloy layer can be obtained by, as one method, using a plating bath containing cobalt ions, tin ions and a complexing agent, and co-depositing at least cobalt and tin on a conductive substrate. , To the plating bath, 0.05
An alloy layer obtained by co-electrodeposition on a conductive substrate from a plating bath to which a protein compound of 1 g / liter was added,
In particular, it has excellent characteristics of maintaining low hydrogen overvoltage performance over a long period of time.

The conductive substrate is, for example, nickel, iron,
Copper, titanium, stainless steel alloy, and the like can be used as long as they have excellent corrosion resistance particularly against caustic alkali. The shape of the conductive substrate is not particularly limited, and generally has a shape according to the cathode of the electrolytic cell, for example, a flat plate,
Curved plate shape, expanded metal shape, punched metal shape, net shape, perforated plate shape and the like are used.

Prior to electroplating the alloy layer on the surface of the conductive substrate, it is preferable to perform a general pretreatment such as degreasing or etching in advance. In addition, by performing appropriate nickel plating, cobalt plating or nickel-sulfur plating on the conductive substrate, or by attaching conductive fine particles such as carbon or platinum group metal, the degree of unevenness of the substrate surface is increased, It is also effective to strengthen the adhesion between the base material and the alloy layer.

The counter electrode used for plating is not particularly limited, but insoluble electrodes such as platinum and a titanium plate coated with platinum can be used.

The alloy layer coated on the surface of the conductive substrate according to the present invention is an alloy layer comprising at least cobalt and tin, and has a tin content of 0.01 to 95% by weight in the alloy layer.
Must be controlled in the range. The electrode of the alloy layer which deviates from this condition has a high cathode overvoltage.

The performance of the alloy layer does not depend on the third component added especially for increasing the surface area of the layer or other impurities present in the plating bath and taken into the alloy layer, and the above conditions are satisfied. It is kept by that. If the thickness of the alloy layer is too small, the effect is insufficient due to the influence of the base material. If the thickness is too large, the alloy layer is easily peeled.

There is no particular limitation on the cobalt source and tin source contained in the plating bath, but the former may use a commonly used cobalt salt such as cobalt chloride or cobalt sulfate alone or as a mixture, and the latter may use chloride. Tin salts such as tin and tin sulfate may be used alone or in combination. The complexing agent added in the plating bath is not particularly limited, but a complexing agent that mainly forms a complex with cobalt ions, for example, an α-amino acid such as citrate, tartrate, pyrophosphate or glycine is used. Can be According to our consideration,
Also, the amount of the complexing agent is not particularly limited, but may be generally about 0.5 to 20 times the molar amount of the cobalt ion concentration + the tin ion concentration in the plating bath. Gelatin, peptone, etc. may be used as the protein compound.

Although the pH of the plating bath varies depending on the complexing agent used, it is necessary to select a region which forms a sufficient complex with metal ions and in which the complexing agent can be stably present. For example, in the case of using pyrophosphoric acid as a complexing agent, the plating bath may be selected to have a pH of 8 to 9 at which cobalt ions and pyrophosphate ions form a stable complex and do not cause decomposition of the complexing agent. The pH adjusting agent is not particularly limited, but may be an inorganic acid such as sulfuric acid or hydrochloric acid, or an inorganic base such as sodium hydroxide or aqueous ammonia.

The temperature of the plating bath is from 20 ° C. to 70 ° C.
You just have to select In general, if the temperature is lower than this temperature range, the plating efficiency is low, so that the economy is difficult. If the temperature is higher than this range, the alloy layer coating becomes brittle. The plating current density may be selected in the range of 1 to 50 A / dm ² .

The present inventor also has sufficient knowledge about what is attributable to the excellent low hydrogen overvoltage performance of the alloy layer of the present invention comprising at least cobalt and tin at a tin content of 0.01 to 95% by weight. Although it cannot be explained, when the cobalt-tin alloy layer is co-electrodeposited by the production method according to the present invention, a special metastable crystal not described on a phase diagram or an ASTM card is generated as a whole or a part of the alloy layer. It is believed that the very fine crystallites have an effect. In fact, when this alloy layer was subjected to heat treatment at 200 ° C. or higher, X-ray diffraction measurement revealed that the peak related to the metastable crystal disappeared at all, and a stable crystal peak of an intermetallic compound appeared instead, and the structure was clearly changed. Although it is recognized that the temperature has changed, when the hydrogen overvoltage of the alloy layer after the heat treatment is measured, only an extremely high value of 300 mV or more is shown.

In the present invention, the alloy layer comprising at least cobalt and tin has a tin content of 0.1 to 1 in particular.
The alloy layer at 5% by weight has high hydrogen storage properties in addition to the above-mentioned metastable crystal, and it is considered that this synergistic effect exerts a further excellent low hydrogen overvoltage performance.

In order to maintain the excellent low hydrogen overvoltage performance of the present invention, it is important to maintain a metastable crystal having fine crystallites, as is clear from the above description. It is necessary to avoid the above heat treatment.

[0020]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Examples 1-3 Cobalt chloride (hexahydrate) 0.126 mol / l,
Dissolve 0.018 mol / l of tin chloride (dihydrate), 0.3 mol / l of tripotassium citrate (dihydrate), 0.3 mol / l of potassium pyrophosphate and 2 mol / l of glycine A plating bath was prepared. At this time, the bath pH was 8.4, and no pH adjuster was added. A nickel plate (10 mmφ) previously subjected to alcohol degreasing and nitric acid etching was used as an electrode substrate, and a Pt-coated titanium plate was used as a counter electrode material.

While controlling the plating bath at 60 ° C., plating was carried out at a current flow of 144 coulombs while changing the plating current density for each embodiment to produce an electrode having a cobalt-tin alloy layer deposited on the electrode substrate. did. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the initial hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at a current density of 40 A / dm ² . Table 1 shows the results.

[0023]

[Table 1]

Each electrode has a temperature of 90.degree.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage when electrolyzing for 7 hours is 7 to
It only increased by about 12 mV.

Examples 4 to 6 The same procedures as in Examples 1 to 3 were carried out except that the concentration of tin chloride in the plating bath was 0.004 mol / L. Table 2 shows the results.

[0026]

[Table 2]

Comparative Example 1 Example 2 was repeated except that cobalt chloride (hexahydrate) in the plating bath was replaced with ferric chloride (tetrahydrate) and 0.01 mol / l of ascorbic acid was further added to the bath. Plating was performed in the same manner as in No. 2. As a result, a tin content of 7
An iron-tin alloy layer of 5% by weight was deposited, and the initial hydrogen overvoltage at this time was 223 mV.

Comparative Example 2 Plating was carried out in the same manner as in Example 2 except that cobalt chloride (hexahydrate) in the plating bath was replaced with manganese sulfate (pentahydrate). As a result, a manganese-tin alloy layer having a tin content of 93% by weight was deposited on the substrate, and the initial hydrogen overvoltage at this time was 735 mV.

Comparative Example 3 Tin chloride (dihydrate) in a plating bath was replaced with nickel chloride (6).
Hydrate), except that the plating was performed in the same manner as in Example 2. At this time, the initial hydrogen overvoltage was 230 mV.

Examples 7 and 8 Cobalt chloride (hexahydrate) 0.126 mol / l,
A plating bath was prepared by dissolving 0.018 mol / l of tin chloride (dihydrate), 0.6 mol / l of potassium pyrophosphate and 2 mol / l of glycine. Bath at this time
H was 8.4 and no pH adjuster was added. A nickel plate (10 mmφ) previously subjected to alcohol degreasing and nitric acid etching was used as an electrode substrate, and P was used as a counter electrode material.
A t-coated titanium plate was used. While controlling the plating bath at 55 ° C., plating was carried out with a plating current density of 144 coulombs and the plating current density was changed for each example, to produce an electrode having a cobalt-tin alloy layer deposited on an electrode substrate. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the initial hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at a current density of 40 A / dm ² . Table 3 shows the results.

[0031]

[Table 3]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage when electrolyzing for 7 hours is 7 to
It only increased by about 13 mV.

Examples 9 and 10 The same procedures as in Examples 7 and 8 were carried out except that the tin chloride concentration in the plating bath was 0.004 mol / L. Table 4 shows the results.

[0034]

[Table 4]

Examples 11, 12 Cobalt chloride (hexahydrate) 0.126 mol / l,
A plating bath was prepared by dissolving 0.036 mol / l of tin chloride (dihydrate), 0.3 mol / l of trisodium citrate (dihydrate) and 1 mol / l of glycine. 28% aqueous ammonia was added to the bath to adjust the bath pH to 8.0. Nickel plate (10m
mφ), a Pt-coated titanium plate was used as a counter electrode material. While controlling the plating bath to 50 ° C, the amount of electricity 144
Plating was performed with Coulomb while changing the plating current density for each example, to produce an electrode having a cobalt-tin alloy layer deposited on an electrode substrate. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at 40 A / d.
It was measured at a current density of m ² . Table 5 shows the results.

[0036]

[Table 5]

At each electrode, 90 ° C., 3
200 at 40 A / dm ² in 2.5% sodium hydroxide solution
The hydrogen overvoltage when electrolyzing for 0 hours is 6 times higher than the initial hydrogen overvoltage.
It only increased by about 10 mV.

Examples 13 and 14 Plating was carried out in the same manner as in Examples 11 and 12, except that the concentration of tin chloride in the plating bath was 0.072 mol / L. Table 6 shows the results.

[0039]

[Table 6]

Comparative Example 4 Plating was carried out in the same manner as in Example 10 except that hydrochloric acid was added to the plating bath to adjust the bath pH to 5.0. The tin content of the deposited alloy layer was 95.9% by weight, and the initial hydrogen overvoltage at this time was 396 mV.

Examples 15 to 17 Cobalt chloride (hexahydrate) 0.398 mol / l,
Tin chloride (dihydrate) 0.01 mol / l, triammonium citrate 0.6 mol / l, glycine 1.
58 mol / liter was dissolved, and the pH was adjusted to 7.0 with aqueous ammonia to prepare a plating bath. A nickel mesh (short axis length = 4 mm, long axis length = 8 mm) previously subjected to alcohol degreasing and nitric acid etching was used as an electrode substrate, and a Pt plate was used as a counter electrode material. While controlling the plating bath at 60 ° C., plating was carried out with a plating current density of 144 coulombs and the plating current density was changed for each example, to produce an electrode having a cobalt-tin alloy layer deposited on an electrode substrate. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the initial hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at a current density of 40 A / dm ² . Table 7 shows the results.

[0042]

[Table 7]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage after electrolysis for 10 hours is 10
It only increased by about 15 mV.

Examples 18 to 20 0.398 mol / l of cobalt chloride (hexahydrate)
Tin chloride (dihydrate) 0.01 mol / l, triammonium citrate 0.6 mol / l, glycine 1.
Three 58 mol / liter plating baths were prepared, and each plating bath contained 0.05 g / protein compound as a protein compound.
One liter, 0.5 g / liter and 1 g / liter peptone were added. Then, aqueous ammonia was added to each plating bath to adjust the pH to 7.0. A nickel mesh (short axis length = 4 mm, long axis length = 8 mm) previously subjected to alcohol degreasing and nitric acid etching as an electrode substrate,
A Pt plate was used as a counter electrode material. While controlling the plating bath at 60 ° C., plating was performed at a plating current density of 10 A / dm ^{2 with a} current flow of 144 coulombs to prepare an electrode in which a cobalt-tin alloy layer was deposited on the electrode substrate. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the initial hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at a current density of 40 A / dm ² . Table 8 shows the results.

[0045]

[Table 8]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
The hydrogen overvoltage at the time of electrolysis for only one hour increased only about 4 mV from the initial hydrogen overvoltage.

Examples 21 to 23 Cobalt chloride (hexahydrate) 0.398 mol / l,
Dissolve 0.002 mol / l of tin chloride (dihydrate), 0.6 mol / l of triammonium citrate, 1.58 mol / l of glycine and 0.5 g / l of peptone, and adjust the pH with aqueous ammonia. It adjusted to 7.0 and prepared the plating bath. A nickel mesh (short axis length = 4 mm, long axis length = 8 mm) previously subjected to alcohol degreasing and nitric acid etching was used as an electrode substrate, and a Pt plate was used as a counter electrode material. While controlling the plating bath at 60 ° C., plating was carried out with a plating current density of 144 coulombs and the plating current density was changed for each example, to produce an electrode having a cobalt-tin alloy layer deposited on an electrode substrate. The tin content of this alloy layer was measured with an X-ray microanalyzer, and the initial hydrogen overvoltage of this electrode was measured at 90 ° C. in a 32.5% caustic soda solution at a current density of 40 A / dm ² . Table 9 shows the results.

[0048]

[Table 9]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage when electrolyzing for 3 hours is 3m from initial hydrogen overvoltage
It only increased by about V.

Examples 24 to 26 Plating was carried out in the same manner as in Examples 21 to 23 except that the concentration of tin chloride in the plating bath was 0.0002 mol / L. Table 10 shows the results.

[0051]

[Table 10]

In each electrode, 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage when electrolyzing for 5 hours is 5m from initial hydrogen overvoltage
It only increased by about V.

Examples 27 to 29 Plating was carried out in the same manner as in Examples 18 to 20, except that gelatin was used as the protein compound to be added to the plating bath. Table 11 shows the results.

[0054]

[Table 11]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
The hydrogen overvoltage at the time of electrolysis for only one hour increased only about 4 mV from the initial hydrogen overvoltage.

Examples 30 to 34 1.0 mol / l of cobalt chloride (hexahydrate), 0.005 mol / l of tin chloride (dihydrate), 0.6 mol / l of triammonium citrate, glycine 1.6
The plating bath was prepared by dissolving mol / l and peptone 0.5 g / l and adjusting the pH to 5.0 with aqueous ammonia. Nickel mesh preliminarily alcohol-degreased and nitric acid-etched as electrode substrate (short axis length = 4 m
m, major axis length = 8 mm) using a Pt plate as a counter electrode material. While controlling the plating bath at 55 ° C., plating was carried out at a current flow rate of 144 C while changing the plating current density for each example, to produce an electrode having a cobalt-tin alloy layer deposited on an electrode substrate. The initial hydrogen overvoltage of this electrode is 90
40 A / dm ^{2 in} a 32.5% caustic soda solution at 40 ° C.
Was measured at a current density of In addition, the alloy layer of the electrode was dissolved in hydrochloric acid, and the tin concentration in the alloy layer was determined by measuring the cobalt concentration and the tin concentration in the solution with a high-frequency inductively coupled plasma emission spectrometer. Table 12 shows the results.

[0057]

[Table 12]

Further, at 90 ° C., 32.
2000 A at 40 A / dm ² in 5% caustic soda solution
Hydrogen overvoltage when electrolyzing for 5 hours is 5m from initial hydrogen overvoltage
It only increased by about V.

Comparative Example 5 Cobalt chloride (hexahydrate) 0.398 mol / l,
0.6 mol / L of triammonium citrate, 1.58 mol / L of glycine and 0.5 g / L of peptone were dissolved, and the pH was adjusted to 7.0 with aqueous ammonia to prepare a plating bath. Nickel mesh (SW
4, LW8) using a Pt plate as a counter electrode material. While controlling the plating bath at 60 ° C., plating was performed at a plating current density of 10 A / dm ^{2 with a} current flow of 144 coulombs to produce an electrode having a cobalt layer deposited on an electrode substrate. The hydrogen overvoltage of this electrode at a current density of 40 A / dm ² in 90 ° C., 32.5% caustic soda solution was 16
It was 5 mV. This electrode was heated at 90 ° C. and 32.5%
The hydrogen overvoltage after electrolysis at 40 A / dm ² for 64 hours in a caustic soda solution was 210 mV, which markedly deteriorated.

[0060]

The effect of the present invention is that the cathode used for the electrolysis of water or the aqueous solution of an alkali metal chloride is, for example, 40 A / 30 A in a 32.5% sodium hydroxide aqueous solution at 90 ° C. 100 at dm ² electrolysis current density
An object of the present invention is to provide a cathode exhibiting an excellent low hydrogen overvoltage of up to 160 mV and characteristics capable of maintaining the overvoltage for a long period of time, and a method for producing the same. This cathode characteristic is an electrode in which at least an alloy layer composed of cobalt and tin is coated on the surface of the conductive substrate, and the tin content in the alloy layer is 0.01 to 95%.
%, Preferably 0.1 to 15% by weight, and the alloy layer is formed by using a plating bath containing cobalt ions, tin ions and a complexing agent. It is manufactured by co-depositing cobalt and tin on a conductive substrate using a plating bath containing 1 g / liter of a protein compound.

Claims (5)

[Claims] 1. An electrode in which an alloy layer comprising at least cobalt and tin is coated on the surface of a conductive substrate, wherein the tin content in the alloy layer is 0.01 to 95% by weight. Low hydrogen overvoltage cathode. 2. A low hydrogen overvoltage cathode according to claim 1, wherein the electrode comprises an alloy layer comprising at least cobalt and tin coated on the surface of a conductive base material, wherein the tin content in the alloy layer is 0.1%. A low hydrogen overvoltage cathode characterized by being 1 to 15% by weight. 3. A low hydrogen overvoltage cathode according to claim 1, wherein a plating bath containing cobalt ions and tin ions and a complexing agent is used, and at least cobalt and tin are co-deposited on the surface of the conductive substrate. A method for producing a low hydrogen overvoltage cathode. 4. The method for producing a low hydrogen overvoltage cathode according to claim 3, wherein a plating bath containing 0.05 to 1 g / liter of a protein compound is added to a plating bath containing cobalt ions, tin ions and a complexing agent. A method for producing a low hydrogen overvoltage cathode, comprising co-depositing at least cobalt and tin on the surface of a conductive substrate. 5. The low hydrogen overvoltage according to claim 1, wherein the cathode is used for electrolysis of water or an aqueous solution of an alkali metal chloride such as sodium chloride. How to use electrodes.