JPH08101160A - Manufacture of silver/silver chloride electrode - Google Patents

Abstract

PURPOSE: To provide a method for effectively manufacturing a silver/silver chloride electrode by immersing a silver electrode in hydrochloric acid, and making a constant current electrolysis. CONSTITUTION: A silver electrode base board A is provided with a number of lead pieces where silver electrode is laminated partially, and an acting electrode B is equipped with projections in positions corresponding to those parts of leads where no silver electrode is laminated in such an arrangement that the projections are electrically connected with one another. The base board A and acting electrode B are immersed in hydrochloric acid in the state that they are confronting in such an arrangement that those parts of leads with no silver electrode laminated are in point contact with the projections, and a constant current electrolysis is conducted so that a silver/silver chloride electrode is accomplished. It is preferred at this time that the immersion in the hydrochloric acid and electrolysis are conducted in the condition that the surface of each projection of acting electrode and those surfaces of leads with no silver electrode laminated besides the contacting points are coated with an insulative substance capable of being removed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a silver / silver chloride electrode. More specifically, it relates to a method for producing a silver / silver chloride electrode by immersing a silver electrode in hydrochloric acid and subjecting it to constant current electrolysis.

[0002]

2. Description of the Related Art Various sensors such as a glucose biosensor are often provided with a reference electrode in addition to a working electrode and a counter electrode. As a reference electrode, a silver electrode is immersed in hydrochloric acid and subjected to constant current electrolysis. The obtained silver / silver chloride electrode is generally used.

In the production of such a silver / silver chloride electrode, the following steps are taken. First, the silver electrode is connected to a galvanostat as a working electrode. A platinum electrode is generally used as the counter electrode, and a commercially available silver / silver chloride electrode is generally used as the reference electrode. These three electrodes are about 0.05-0.
A 20 M hydrochloric acid aqueous solution is immersed in the cell used as the electrolytic solution. Then, at a temperature of about 20 to 30 ° C., a constant current is passed between the working electrode and the counter electrode to form a silver chloride layer on the surface of silver as the working electrode. The current density at this time is about 0.4 to 1.0 mA / cm
² , the energization time is about 5-30 minutes.

In this case, the silver electrode serving as the working electrode is attached to a lead portion such as a platinum film which is previously formed on the ceramic substrate or the like by the vapor deposition method, the sputtering method, the screen printing method, or the like.
The silver electrode is formed by screen printing and firing of silver paste, cut with a dicing saw,
Each one is individually silver chloride.

Therefore, in such a conventional method for producing a silver / silver chloride electrode, it takes a lot of time to produce a large number of silver / silver chloride electrodes because it is cut and then converted to silver chloride. , Was extremely inefficient.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for producing a silver / silver chloride electrode extremely efficiently when the silver electrode is immersed in hydrochloric acid and subjected to constant current electrolysis to produce a silver / silver chloride electrode. To do.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
(A) A silver electrode substrate on which a large number of lead pieces with silver electrodes partially laminated are formed, and (B) a protrusion is provided at a position corresponding to the non-laminated silver electrode portion of each lead piece. The working electrode, which is conductively connected, is immersed in hydrochloric acid in a state in which the silver electrode substrate and the working electrode are opposed to each other so that the silver electrode non-laminated portion of each lead piece and each protruding portion make point contact with each other, This is achieved by performing a constant current electrolysis to produce silver / silver chloride electrodes.

At this time, preferably, the surface of the non-laminated portion of the silver electrode and the surface of each working electrode projection of each lead piece other than the contact point are coated with a removable insulating substance and immersed in hydrochloric acid and constant current electrolysis. Is done.

In FIG. 1, one mode of the silver electrode substrate A is shown as a plan view. A large number of lead pieces 2, 2 ′, ... Are made of vapor-deposited platinum or the like on a hydrochloric acid resistant substrate 1 such as ceramics or glass, and silver electrodes 3, 3 are formed on a part of them.
´… are stacked. Lead pieces are generally about 1 vertical
It is set to a size of ~ 50mm and a width of about 0.1-5mm.

On the other hand, in FIG. 2, the working electrode B corresponding to this is shown.
Are shown in plan view. On the hydrochloric acid resistant substrate 4 made of ceramics, glass or the like, the protrusions 5, 5 ', ... Are provided at positions corresponding to the non-laminated portions of the silver electrodes of the lead pieces 2, 2' ,. .. is provided, and the protrusions are connected to each other 6 on the substrate by conducting connection. As the material of the working electrode,
Platinum, carbon, or the like is generally used, and the protrusions 5 and their conductive connecting portions 6 are formed by a method such as vapor deposition, sputtering, or screen printing. The shape and size of the protrusion are not particularly limited, but a height larger than the film thickness of the silver electrodes 3, 3 ′, ... Provided on the silver electrode substrate A is required.

In addition to the above-described aspect, the protrusion 5 can be provided at the tip of a contact probe, spring contact probe, etc. In this case, a lead wire is soldered to any position of the probe. It is also possible to electrically connect the protrusions to each other, that is, to electrically connect the protrusions to each other without using a substrate.

As shown in FIG. 3, the silver electrode substrate A and the working electrode B were made to face each other so that the silver electrode non-laminated portion of each lead piece and each working electrode protruding portion were in point contact with each other. After being put into a state, it is immersed in hydrochloric acid and subjected to constant current electrolysis to silver chloride the surface of the silver electrode laminated on each lead piece,
A silver / silver chloride electrode is formed there. Constant current electrolysis in hydrochloric acid is carried out according to the general operating conditions described above. Then, the silver electrode substrate is cut into individual lead pieces.

Although the silver / silver chloride electrode can be efficiently manufactured by such a method, leakage from the surface of the non-laminated portion of the silver electrode and the surface of each working electrode projection of each lead piece in contact with hydrochloric acid can be prevented. Occasionally, an electric current is generated. In such a case, a predetermined current density cannot be obtained on the silver electrode, the silver chloride treatment cannot be controlled to produce a stable silver / silver chloride electrode with good reproducibility, and more electric energy is needed than necessary. Will be consumed.

In order to avoid such a situation, it is preferable that the surfaces of the silver electrode non-laminated portions of the lead pieces other than the contact points and the surfaces of the working electrode projections are coated with an insulating substance that can be removed later. .

As the insulating substance, after being converted into silver chloride,
A substance that can be easily removed by means such as dipping in an organic solvent without using a cleaning method such as rubbing or ultrasonic cleaning that may damage the silver electrode, such as grease, silicone oil, or silicone rubber is used. To be

FIG. 5 shows a state in which the silver electrode non-laminated portion of each lead piece whose surface is coated with such an insulating material and each working electrode protrusion are in point contact, except for the contact points. In FIG. 6, the main part (circle part) is shown as an enlarged view. That is, the surface 8 of the used tip portion 5 of the spring contact probe except the contact point 7 is coated with an insulating material 10 for preventing leakage current.
Further, the surface 9 of the non-laminated portion of the silver electrode of each lead piece 2 is also coated with an insulating material 10 'for preventing leakage current except for the contact points 7.

In the constant current electrolysis in hydrochloric acid in such a state, the spring contact probe 11 whose tip is integrally formed as the working electrode projection 5 is fixed to the support plate 12, and silver is partially attached to it. Lead piece 2 with electrode 3 laminated
The silver electrode substrate 1 (FIG. 4) on which a large number of electrodes are formed is fixed by the fixture 13 in a state of being in point contact with each other as described above, and then immersed in hydrochloric acid 19, and the counter electrode 1 similarly immersed in hydrochloric acid 19
Galvanostat 17 connected to 5 and reference pole 16
Is performed by connecting the lead wires 18, 18 ', 18''for electrically connecting the working electrode projections 5 to each other and supplying a constant current thereto.

The removal of the insulating material after the silver chloride conversion by the constant current electrolysis thus performed can be easily carried out by a method of immersing the insulating material in an organic solvent without damaging the silver electrode. it can.

When an insulating material is not used, the electrical resistances of the silver electrode non-laminated portion of each lead piece and each surface of the spring contact probe and the silver electrode surface are different, and the silver electrode is changed in the process of silver chloride formation. Since the electric resistance of the surface is constantly changing, it is not possible to control the current density on the silver electrode by calculation, and it is possible to find out the conditions for silver chloride formation by conducting a conditioning experiment in advance. It is difficult to set general-purpose processing conditions because the leakage current greatly changes depending on the electrode part, the liquid surface height of the hydrochloric acid aqueous solution, etc. However, when an insulating substance is used in such a form, Since the leakage current is prevented, it becomes easy to set a versatile processing condition.

[0020]

According to the method of the present invention, a silver / silver chloride electrode can be efficiently manufactured. At that time, when the silver electrode non-laminated portion surface of each lead piece other than the contact point and each working electrode projection surface are coated with a removable insulating substance, immersion in hydrochloric acid and constant current electrolysis are performed, In addition to preventing leakage current and leading to energy saving, a current flows at a constant current density on the silver electrode, and current electrolysis can be controlled, so silver chloride treatment can be performed with good reproducibility.

[0021]

Next, the present invention will be described by way of examples.

Example 1 On an alumina substrate (Kyocera product A-493, 4-inch square),
Each of the protrusions having the shape shown in (1) and their conductive connecting portions were formed of platinum by a screen printing method to form working electrodes.
Such a working electrode was connected to a galvanostat (HA-501 manufactured by Hokuto Denko) together with a counter electrode (platinum electrode manufactured by BAS) and a reference electrode (silver / silver chloride electrode manufactured by the same).

On the same ceramic substrate, 24 pieces of lead pieces having the shape shown in FIG. 1 were formed by vapor-deposited platinum in a size of 0.5 × 10 mm, and a part of them was screen-printed with silver paste and baked. , Silver electrodes are laminated.

Then, after the silver electrode substrate and the working electrode are made to face each other by a fixture so that the silver electrode non-laminated portion of each lead piece and each protrusion are in point contact, together with the counter electrode and the reference electrode. Immersion in 0.1 M hydrochloric acid, constant current electrolysis under conditions of current density of 0.6 mA / cm ² silver electrode, 25 ° C, 20 minutes, silver chloride is silver chloride on the entire surface of silver electrode at the same time to form silver / silver chloride electrode. We were able to. Then, using a dicing saw, the ceramic was cut into 24 pieces with a size of 20 × 14 mm.

Example 2 On an alumina substrate (Kyocera product A493, 2 inch square),
Six sets of lead pieces and silver electrodes having the shape shown in FIG. That is, a platinum thin film lead piece of 0.5 × 10 mm was formed by a vapor deposition method, and then a silver electrode covering a part thereof was formed in a size of 4 × 3 mm and laminated.

As the working electrode, a spring contact probe having a protruding portion at the tip is used, and the supporting plate is pointed so that the protruding portion makes point contact with the silver electrode non-laminated portion of each lead piece of the silver electrode substrate. Fixed The surface of the used spring contact probe is coated with silicone rubber to prevent leakage current.

On the surface of the non-laminated portion of the silver electrode of each lead piece other than the contact point, vacuum grease (UK APIEZON PRO
(DUCTS product) is applied, and after fixing it with a fixture so that the contact point of each lead piece not coated with this grease and the working electrode projection part make point contact, together with the counter electrode and the reference electrode, It was immersed in 0.1 M hydrochloric acid.

In such a state, the lead wire connecting the upper ends of the spring contact probes to each other and the galvanostat are connected to each other, and the current density on the surface of the silver electrode is 0.
6 mA / cm ^2, under conditions of temperature 25 ℃, 432μA (0.6mA / cm 2 × 0.1
A constant current of 2 cm ² × 6) was passed for 20 minutes, and the entire surface of the silver electrode was silver chloride simultaneously to form a silver / silver chloride electrode.

After that, in order to remove the grease remaining on the alumina substrate, the alumina substrate was immersed in toluene for 5 minutes, then immersed in isopropanol for 3 minutes, washed with running water and air blow dried. After drying, using a dicing saw, it was divided into 6 pieces with a size of ceramics cut out of 20 × 14 mm.

[Brief description of drawings]

1 is a plan view of one embodiment of a silver electrode substrate A. FIG.

FIG. 2 is a plan view of a working electrode B corresponding to a silver electrode substrate A.

FIG. 3 is a side view showing a state where a silver electrode substrate A and a working electrode B are opposed to each other.

FIG. 4 is a plan view of another embodiment of the silver electrode substrate A.

FIG. 5 is a schematic diagram of a state in which constant current electrolysis is performed using a spring contact probe integrally formed with a working electrode protrusion.

FIG. 6 is an enlarged view of a circled portion in FIG.

[Explanation of symbols]

 1,4 Substrate 2 Lead piece 3 Silver electrode 5 Projection part 6 Conductive connection part 7 Contact point 8 Working electrode projecting surface 9 Silver electrode non-laminated part surface 10,10 'Insulating material 18,18', 18 '' Lead wire 19 hydrochloric acid

Claims (2)

[Claims] 1. (A) A silver electrode substrate having a large number of lead pieces formed by laminating silver electrodes on a part thereof, and (B) Protrusions provided at positions corresponding to non-laminated portions of the silver electrodes of each lead piece. , A state in which the silver electrode substrate and the working electrode face each other so that the non-laminated portion of the silver electrode of each lead piece and each working electrode projecting portion make point contact with the working electrode to which the protrusions are conductively connected. A method for producing a silver / silver chloride electrode, which comprises immersing in a hydrochloric acid at a constant temperature and performing constant current electrolysis. 2. Conducting dipping in hydrochloric acid and constant current electrolysis while the surfaces of the non-laminated portions of the silver electrodes and the surfaces of the working electrode projections of each lead piece other than the contact point are coated with a removable insulating substance. The method for producing a silver / silver chloride electrode according to claim 1, wherein