JPH02163392A - Production of electrode - Google Patents

Abstract

PURPOSE:To produce an electrode having a low hydrogen overvoltage and superior durability by forming an Ni plating layer contg. sulfur on a base material for an electrode with an Ni plating bath of a specified pH contg. an Ni salt and a soluble sulfur-contg. compd. CONSTITUTION:An Ni plating layer contg. sulfur is formed on a base material for an electrode such as an iron base material with an Ni plating bath of pH<=2 contg. an Ni salt such as NiCl2 and a soluble sulfur-contg. compd. such as thiourea. An electrode having a low hydrogen overvoltage of about 100-150mV and superior durability is obtd. This electrode is useful as an electrode for electrolysis on an industrial scale.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an electrode, and more particularly, to a method for manufacturing a nickel-plated electrode containing sulfur L', l. .

These electrodes can be used as electrodes in various electrochemical devices, but are particularly suitable for use as industrial electrolysis electrodes, such as water electrolysis electrodes and salt electrolysis electrodes, and exhibit high durability. [Prior art] In the field of industrial electrolysis such as water electrolysis and salt solution, '
IA electrolytic voltage voltage reduction is an important issue. In particular, in the cation exchange membrane salt electrolysis technology, which is noted as a new process, 64 low hydrogen overvoltage cathodes were developed to reduce the electrolytic voltage and the hydrogen overvoltage of the cathode. has been done.

As one of the manufacturing methods of low hydrogen overvoltage cathode? IS polar group)
A method for manufacturing an electrode in which sulfur-containing nickel is coated on top of nickel by electroplating is already known.
-2305, Japanese Patent Application Laid-Open No. 1983-1980, filed by Fukaiishi et al.
No. 19388, No. 57-114678, etc. have been proposed.

These sulfur-containing nickel platings; Narita-U electricity is an economical way to IR? There are examples that have already been put into practical use. However, these limb-covering electrodes may cause new problems in relation to the metal wire used as the electrode base material.

In other words, it is a well-known phenomenon that if a metal is polarized in the cathodic direction, it will undergo cathodic protection, and the hydrogen overpressure exhibited by a metal will cathodically protect the metal by the positive amount of the overcharge. Therefore, when reducing the hydrogen overvoltage, it is necessary to take into account the corrosion of the metal base material used as the electrode abrasion.

For example, if a test shot made of iron is coated with a corrugated film exhibiting low hydrogen permeation pressure as described above, the problem of melting and corrosion of the iron will occur to the extent that the hydrogen overvoltage is reduced, and the electrodes and electrolytic cell will be damaged. This will cause serious problems such as a shortened service life, a deterioration in the quality of the product 1''lJf alkali, and a deterioration in the performance of the cation exchange membrane.

By the way, in the cation exchange membrane salt electrolysis method, the methods currently in use can be roughly divided into two. One is a new ion exchange membrane electrolysis method in which the electrolytic cells previously used in the mercury method, etc. were discarded and a new one was installed, and the other is the electrolytic cell previously used in the mercury method, asbestos diaphragm method, etc. This is an improved ion exchange membrane electrolysis method that effectively utilizes the

The electrolytic cell using the improved ion exchange desorption method uses a cathode and cathode case made mostly of iron.

Therefore, even in the improved ion-exchange membrane electrolysis method, reducing the electrolysis voltage is an important issue.
The problem arises that the iron that makes up the five bodies melts and corrodes.

[Problems to be Solved by the Present Invention] Aim of the present invention is to provide a method for manufacturing an electrode that exhibits low hydrogen overvoltage characteristics and excellent durability, especially applicable even when using an electrode group made of iron. The goal is to propose a manufacturing method that can produce IJ.

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have conducted intensive studies regarding sulfur-containing nickel plating coated electrodes, particularly regarding the plating conditions and the electrode characteristics of the obtained electrodes, and have found that p.
By applying sulfur-containing nickel plating to the electrode base Murakami using a nickel plating bath containing the following nickel salts and soluble sulfur-containing compounds, it is possible to achieve low hydrogen overvoltage and excellent durability with little deterioration. The present invention was completed based on the discovery that the following can be obtained.

The present invention will be explained in detail below. The sulfur-containing nickel plating bath used in the present invention includes soluble nickel salts such as nickel chloride, nickel sulfate, and nickel sulfamate; Examples of soluble 1〆ε yellow compounds include:
Examples include thiocyanate, thiourea, and sulfurous acid, bisulfite, thiosulfuric acid, and dithionite oxyacid salts in which the oxidation number of sulfur is 5 or less. Historically, ammonium ions may be added to the nickel plating bath to obtain active nickel plated wave membranes that are strong and exhibit excellent durability.

In the manufacturing method of 1" of the present invention, the pl of the plating bath is
It is necessary to maintain l to 2 or less, and thereby 11) the generated electricity i exhibits a low hydrogen overvoltage and has excellent durability.

For example, an electrode obtained by the method of the present invention using an iron base material as a '; u W )Is shrine has a
00-150mv low hydrogen overvoltage.

As a consideration, FIG. 1 shows the potential dependence of the iron elution rate determined by the present inventor as ΔIII. The system used for the measurement was 32% Na OI, which is used as a general salt electrolysis condition.
f in aqueous solution at 9[1°C]. As shown in FIG. 1, it was found that the iron elution rate showed a clear voltage dependence based on the above 11111 constant. Furthermore, the potential dependence of the iron elution rate has a clear inflection point near -1,Ov, and as the potential decreases from around -1,OV, the iron elution rate J
The amount of U decreased significantly, and it became an amount that hardly caused any problems. Therefore, under the negative salt electrolysis conditions,
Since the potential of the iron cathode is about -1.15 V, iron elution is not a problem, but iron elution can be suppressed even if the potential is further increased in the range of 100 to 150 mV and the overvoltage is lowered. Understood.

That is, compared to the above iron base) A, 100 to L50 m
V low hydrogen overvoltage is one shift in which the hydrogen overvoltage can be lowered without damaging the base material.

On the other hand, if a nickel plating bath containing Ktm is applied to the base material using a plating bath with pl+ exceeding 2, the overvoltage of the i+i' electrode will be lower; for example, if iron is used as the electrode base material, The dissolution of can no longer be ignored.

The pl+ of the plating bath used in the present invention is adjusted once by various methods. For example, if pl+ is large, it can be adjusted by adding an acid such as hydrochloric acid or saccharic acid to the plating bath as appropriate.

Other plating conditions may be selected as appropriate; for example, the plating temperature may range from room temperature to 90° C., and the current density during plating may range from 061^1d112 to 0^/dlI2.

As the electrode base material used in the present invention, metal or conductive material (
-+- Any conductive base material such as resin or ceramics can be used, but the -a effect is particularly applicable to the present invention when iron or an alloy mainly composed of iron is used as the base material. The shape of the electrode base material may be any shape such as a flat plate, mesh shape, porous shape, etc., but when used as a gas generating electrode at +2L current density, expanded metal, punched metal, or wire mesh shape is particularly suitable. These are used.

Furthermore, in the electrode manufacturing method of the present invention, the above-mentioned electrode base material can be used which has been subjected to an appropriate pretreatment. This appropriate pretreatment includes, for example, strike nickel plating treatment using a hydrochloric acid acidic nickel plating bath, which is a known method for removing passive films on stainless steel surfaces;
This includes ordinary nickel plating applied to improve the eating quality of the base material, or base nickel plating that exhibits excellent adhesion to both the base material and sulfur-containing nickel plating.

[Effects of the Invention] As described above, the electrode obtained by the method of the present invention can be applied as an electrode in various electrochemical devices, and is particularly useful as an electrode for industrial electrolysis, such as an electrode for water electrolysis. It can also be used as an electrode for salt electrolysis. In addition, it is particularly effective when using iron or an alloy mainly composed of iron or an iron-based alloy for cathodes, cathode cans, etc.
Give a low hydrogen overvoltage and add 1f to 100 to 50
It becomes possible to give an electrolytic voltage as low as nv. Furthermore, this electrode exhibits high durability, and its industrial value is extremely large.

[Examples] Hereinafter, examples of the present invention will be described, or the present invention will be described below.
XR is not determined.

Table 1 Nickel plating conditions including sulfur plating bath composition> Nickel chloride 1.2 mol/tothiourea
0.4-〇! /1.Ammonium chloride
1. owol/I plated strip 1 cow> ・Current density IA/(+112 ・Temperature 0
0°C - pH 1,5 - Plating time 211r Example 1, Comparative Examples 1 to 2 As Example 1, on an iron wire mesh electrode base tA with a size of 4 x 7.5 effl and a small pole shape or 6 meshes, Table 1
Nickel plating was performed using the conditions shown in , and a negative electrode was produced. Note that the pH after bath preparation was approximately 4.2, and the pu was lowered to 1.5 by adding hydrochloric acid.

In addition, as Comparative Example 1, an electrode was obtained which was plated under the same conditions as Example 1 except that the plating bath shown in Table 1 was used and the pl+ of the plating bath was not lowered and the plH° was set to 2. A wire mesh electrode made of iron without nickel plating was obtained. These 1 attach the pole to a ferrous can body, use a cation exchange membrane, and as a positive image] 1 on the I? u 0
2-'l'I02Using the membrane I) Saline solution was electrolyzed under the conditions shown in Table 2 using SA type extract band metal.

Table 2 Table 3 Salt electrolysis conditions, cathode chamber N + tCIi agricultural rate 230 g/l, cathode chamber h
lt011iG degree 32vL%Na011・Current l+
i degree 2LIA/ds2 ・/AA degree 90℃ ・Distance between positive and cathode 2I (
Press the cation exchange membrane against the anode chamber side and press firmly.
2) Example 1. Electrolysis voltage of the electrolytic cell using the electrode rubbed in Examples 1 and 2 as the cathode, potential of the cathode (V vs, 5
lIIE), electricity of iron can body (n<V vs, 5IIIE)
Table 3 shows the iron concentration values in caustic soda.

From the table, it can be seen that the electrode obtained by the method of the present invention was in Comparative Example 2.
Compared to the iron cathode obtained in Comparative Example 2-(-
A) It can be seen that the irradiance was suppressed to almost the same level as the iron cathode. On the other hand, j:#1lilffl in Comparative Example 1 showed an extremely low overvoltage as shown in Table 3, and Comparative Example 2
It gave a 250 mV lower voltage than the iron cathode with 117, but the iron concentration in the caustic soda was 7.5 ppm.
This caused problems with iron dissolution and 114 meals.

Example 2. Comparative Example 3 1. A cathode chamber body made of iron and having an internal volume of 1 tn×1.3 m and a height of about 0.8 m was nickel plated by the following method. This electrolytic cell is a so-called improved ion-exchange membrane brine electrolysis cell, which is a conventional asbestos diaphragm salt electrolytic cell converted to an ion-exchange desorption method, and the cathode shape is a wire mesh electrode similar to that of Example 1.

First, the inner surface of the iron cathode chamber was acid-treated with hydrochloric acid, and after washing with water, the base nickel plating was performed under the conditions shown in Table 4.
After that, under the conditions shown in Table 5, sulfur f1? Nickel plating including

Person 4 Base nickel plating conditions Plating bath, t11> ・Nickel chloride 1.2 mol/l ・Ammonium chloride 1. Omol/l plating conditions> Paton flow density 2A/d■ ・Temperature・pH 4.0・Plating time 40℃ 0.511r Table 5 Mesobath composition under sulfur-containing nickel plating conditions> ・Nickel chloride 0.5 parts OI/Tothiourea
0.3mol/1・Ammonium chloride
1. oraol/1 pixel condition> ” ia (AE 't% lx 2A/dm
' Temperature 411 'C+) H1,0・Plating time 2! ! T. In this way, the DSA solar cell was attached to the electrolytic cell having the cathode and the cathode chamber left in 'A', and Example 1
Salt electrolysis was performed under the same conditions. Note that electrolysis was carried out under the same conditions using an iron wire mesh cathode that was not plated with nickel at all for reasons of comparison (Comparative Example 3).

Table 6 shows the changes over time in the electrolytic voltage and iron concentration in caustic soda in the ``--'' cell.

Table 6 The electrolytic voltage and pressure of the electrode remained almost constant for one year, indicating that the electrode had excellent durability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the potential dependence of the iron elution rate in a 32% N1tOII aqueous solution at 90°C.

Claims (1)

[Claims] (1) A method for producing an electrode, which comprises applying nickel plating containing sulfur onto the electrode base H using a nickel plating bath containing a nickel salt and a soluble sulfur-containing compound having a pH of 2 or less.