JPH06229980A - Constant potential electrolyte type gas sensor - Google Patents

Abstract

PURPOSE:To provide a gas sensor which facilitates the drawing of a lead from an electrode without impairing functions of a gas permeable film while eliminating changes in resistance value of the electrode, effect of changes in the temperature and humidity of the environment, hourly changes in the accuracy of the sensor and attitude difference in the accuracy of the sensor concerning a constant potential electrolyte type gas sensor so arranged to separate the gas permeable film from an electrode catalyst. CONSTITUTION:A working pole 21, an opposed pole 23 and a control pole 24 are arranged in a reaction chamber filled with an electrolyte 26 to make a gas to be inspected act on the working pole 21. In a constant potential electrolyte type gas sensor of such a type, the working pole 21 is separated from a gas permeable film 20. Thus, the gas permeable film 20 and the working pole 21 are arranged on one side of the gas sensor through a water permeable porous material 22 while the opposed pole 23 and a control pole 24 on the other side thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a potentiostatic electrolytic gas sensor, and more particularly to a potentiostatic electrolytic gas sensor having a structure in which a gas permeable membrane and a working electrode are separated.

[0002]

2. Description of the Related Art Around the living environment, there are many gasses that are harmful to humans and animals and plants, and gases that have a high risk of igniting and causing an explosion. Occasionally, these highly dangerous gases may be generated at construction sites or workplaces, and among them, carbon monoxide gas or hydrogen sulfide gas, which has a high concentration, even causes lethality. Therefore, in order to accurately detect the concentrations of these gases, a potentiostatic electrolysis gas sensor based on the potentiostatic electrolysis method has been conventionally used.

An example of a conventional potentiostatic electrolysis gas sensor will be described with reference to the drawings. In FIG. 3, 1 is a casing, and this casing 1 is a cylindrical body 2
have. The openings at both ends of the cylindrical body 2 are closed by an oxygen permeable film 3 made of a polymer synthetic resin film which is free of oxygen permeation and a gas permeable film 4 made of a gas permeable polymer synthetic resin film, so that the electrolytic solution is filled inside. A reaction chamber 5 to be filled is formed. The oxygen permeable membrane 3 and the gas permeable membrane 4 are fixed to both ends of the tubular body 2 by means of lids 6 and 7 screwed onto the outer circumferences of both ends of the tubular body 2, respectively. 8 and 9 are opened. The counter electrode 10 and the reference electrode 12 are supported on the inner surface of the reaction chamber 5 of the oxygen permeable membrane 3. In addition, the working electrode 1 is provided on the inner surface of the reaction chamber 5 of the other gas permeable membrane 4.
1 is supported. The working electrode 11 is usually formed by integrally forming a noble metal catalyst such as a palladium-based catalyst or a platinum-based catalyst with the gas permeable membrane. On the other hand, the counter electrode 10 releases oxygen in the air that has permeated the oxygen permeable film 3, so that a cathode reaction occurs due to the electrons and hydrogen ions released from the working electrode 11. Then, this reaction is converted into an electrical output, and the test gas is detected from the result of the output value.

[0004]

The conventional constant potential electrolytic gas sensor as described above has various problems. In particular, the conventional one in which a noble metal catalyst such as a palladium-based or platinum-based catalyst and a gas permeable membrane are integrally formed, is formed integrally by laminating the catalyst on a gas permeable polymer synthetic resin membrane and heat-treating this. However, this treatment impairs various functions such as gas separation function of the membrane, permeation performance, structure, electrical output due to gas reaction, and response speed. In addition, there is a problem in that the lead wire is pulled out from the electrode and the resistance value changes at the electrode. In addition, the three-phase interface between the electrode, gas permeable membrane, and electrolyte is affected by changes in the environment temperature and humidity due to changes in the shape of the membrane material, etc., and the accuracy of the sensor changes over time. There is a difference in accuracy.

The present invention has been made in view of the above problems in the conventional potentiostatic electrolytic gas sensor,
Its purpose is to separate the gas permeable membrane and the electrode catalyst so that (1) the various functions of the gas permeable membrane are not impaired, the lead wire can be easily pulled out from the electrode, and the resistance at the electrode There are no fluctuations in the values, and (2) constants that are not affected by changes in the temperature and humidity of the environment, the accuracy of the sensor does not change over time, and the accuracy of the sensor does not differ in attitude. An object of the present invention is to provide a potential electrolytic gas sensor.

[0006]

Means and Actions for Solving the Problems The inventors of the present invention have intensively studied to solve the above problems. And
Rather than laminating a palladium-based or platinum-based precious metal catalyst used as an electrode on a gas-permeable polymer synthetic resin membrane and heat-treating this to integrally form it, the catalyst is fixed to a conductor Attention was paid to the fact that the electrode and the gas permeable film were formed as separate members, which were laminated and assembled.

The present invention is based on the above idea,
The gist is (1) a potentiostatic electrolysis gas sensor having a working electrode, a counter electrode, and a reference electrode in a reaction chamber filled with an electrolytic solution, and a test gas acting on the working electrode. And a potentiostatic electrolysis gas sensor characterized by having a structure in which the working electrode is separated, (2) a reaction chamber filled with an electrolytic solution is provided with a working electrode, a counter electrode and a reference electrode, and the working gas is a test gas. In the potentiostatic electrolysis gas sensor configured to operate, the gas permeable membrane and the working electrode are separated from each other, and the gas permeable membrane and the working electrode are formed on one surface and the counter electrode on the other surface through the water-permeable porous material. It is a potentiostatic electrolysis gas sensor characterized by having a structure in which a reference electrode is arranged.

The potentiostatic electrolytic gas sensor according to the present invention comprises:
It is used for quantitative detection of various gases such as carbon monoxide, hydrogen sulfide, ozone and semiconductor manufacturing gas. The structure is roughly composed of a structure in which a working electrode, a counter electrode, and a reference electrode are provided in a reaction chamber filled with a strong acid electrolyte, and a test gas is caused to act on the working electrode to cause a cathode reaction in the electrolyte. Is generated, the reaction is converted into an electrical output, and the test gas is detected by the result of the output value.

The present invention has a structure in which the working electrode is separated from the gas permeable membrane that permeates and introduces the test gas. Here, as the gas permeable film, an ordinary gas permeable polymer synthetic resin film is used. Further, the working electrode is prepared by fixing a noble metal catalyst such as palladium or platinum on a conductive material such as a wire mesh and heat treating this. Therefore, according to the present invention, a catalyst is laminated on a gas-permeable polymer synthetic resin membrane, and the catalyst is not heat-treated to be integrally formed. Since it has a laminated structure, the material and structure of the membrane, the gas separation function of the membrane, the permeation performance, the electrical output due to the gas reaction, the response speed, and other functions are not impeded. Since the working electrode is manufactured by fixing the catalyst to a conductive material and heat-treating it, it is easy to pull out the lead wire from the electrode and there is no fluctuation in the resistance value at the electrode. , Is constant everywhere.

Further, the gas permeable membrane and the working electrode are laminated and arranged on one surface of a water-permeable porous material, and the counter electrode and the reference electrode are arranged on the other surface to be assembled. The water-permeable porous material must be capable of permeating the electrolytic solution so that the solution is always in contact with the working electrode. There are also non-woven fabrics and filter papers, but this is not preferable because the volume changes due to swelling. Therefore, it is preferable to use an inorganic material that is water-permeable and does not change its shape.

[0011]

EXAMPLES The present invention will be described in more detail based on the following examples. FIG. 1 is a layout diagram showing the configuration of a gas permeable membrane, a working electrode, a water-permeable porous material, a counter electrode and a reference electrode of a potentiostatic electrolysis gas sensor according to the present invention. That is, a structure in which a noble metal catalyst is fixed to a gas permeable polymer synthetic resin film 20 and a conductive material such as a wire mesh and the like is heat treated to form a working electrode 21 as separate members, Both of them have a structure in which a water-permeable porous material 22 that does not change in shape is disposed on one surface thereof and a counter electrode 23 and a reference electrode 24 are disposed on the other surface. The reaction chamber formed in the casing 25 is filled with the electrolytic solution 26. With such a configuration, the electrolytic solution can be permeated through the water-permeable porous material so that the electrolytic solution is always in contact with the working electrode or the like.

Further, according to this structure, since the three-phase interface between the electrodes, the gas permeable membrane and the electrolytic solution is formed through the porous material which does not change its shape, the pressure is constantly applied with a constant tension. Since the gas sensor can be brought into the charged state, it is possible to provide the gas sensor which is less affected by the temperature and humidity of the environment. Since the three-phase interface is always in a fixed place and does not move, the sensor is stable over time. Furthermore, because it is assembled by fixing it through a porous material that does not change its shape, the electrolyte is always supplied to the three-phase interface because it is in contact with the excess electrolyte in any posture. , No attitude difference.

Next, FIG. 2 is an external view of a potentiostatic electrolysis gas sensor according to the present invention, and FIG. 2 (1) is a plan view thereof, showing an electrolyte solution inlet 27, a casing 25, and a casing cover 2.
2 (2) is a side view thereof, which includes an electrolyte injection port 27, a casing cover 29, and a gas sensing port 30.

[0014]

The present invention is a potentiostatic electrolysis gas sensor comprising a working electrode, a counter electrode and a reference electrode in a reaction chamber filled with an electrolytic solution, and a test gas acting on the working electrode. The gas permeable membrane and the working electrode are not integrally formed, but have a structure in which they are laminated as separate members,
Since the gas sensor is a potentiostatic electrolysis type gas sensor having a structure in which a gas permeable film and a working electrode are arranged on one surface through a water-permeable porous material, and a counter electrode and a reference electrode are arranged on the other surface, the present invention provides gas permeation. It does not impair the functions of the membrane. In other words, the material and structure of the membrane, the gas separation function of the membrane, the permeation performance, the electrical output due to the gas reaction, the response speed, and other functions are not impaired. And since the working electrode is manufactured by applying a catalyst to a conductive material and heat-treating it, it is easy to pull out the lead wire from the electrode, and there is no change in the resistance value at the electrode, and it can be used anywhere. It is constant.

Further, according to the present invention, since the three-phase interface between the electrodes, the gas permeable membrane and the electrolytic solution is formed via the porous material which does not change its shape, it is always pressurized with a constant tension. It can be in a state, and even if the temperature or humidity of the environment changes, it is less affected by it. And since the three-phase interface is always in a fixed place and does not move, it is a sensor that is stable over time, and is fixed and assembled through a porous material that does not change shape, so what kind of posture Even in the case, since the electrolyte is in contact with the excess electrolyte, the electrolyte is always supplied to the three-phase interface,
The effect that there is no difference in posture is achieved.

[Brief description of drawings]

FIG. 1 is a layout diagram showing a configuration of a potentiostatic electrolysis gas sensor according to the present invention.

FIG. 2 is an external view of a potentiostatic electrolysis gas sensor according to the present invention, FIG. 2 (1) is a plan view thereof, and FIG. 2 (2) is a side view thereof.

FIG. 3 is a cross-sectional view showing an example of the structure of a conventional potentiostatic electrolysis gas sensor.

[Explanation of symbols]

 1 Casing 2 Cylindrical body 3 Oxygen permeable membrane 4 Gas permeable membrane 5 Reaction chambers 6, 7 Lid 8 Oxygen flow port 9 Gas flow port 10 Counter electrode 11 Working electrode 12 Reference electrode 20 Gas permeable membrane 21 Working electrode 22 Porous material 23 Counter electrode 24 Reference electrode 25 Casing 26 Electrolyte 27 Electrolyte inlet 28, 29 Casing cover 30 Gas sensing port

Claims (2)

[Claims] 1. A potentiostatic electrolysis gas sensor comprising a working electrode, a counter electrode, and a reference electrode in a reaction chamber filled with an electrolytic solution, wherein a working gas is allowed to act on the working electrode. A potentiostatic electrolysis gas sensor characterized by having a separate structure. 2. A potentiostatic electrolysis gas sensor having a working electrode, a counter electrode and a reference electrode in a reaction chamber filled with an electrolytic solution, wherein a working gas is made to act on a working gas, a gas permeable film and a working electrode. A potentiostatic electrolysis gas sensor having a structure in which a gas-permeable membrane and a working electrode are disposed on one surface of the water-permeable porous material, and a counter electrode and a reference electrode are disposed on the other surface via a water-permeable porous material.