JP2020139894A - Constant-potential electrolytic gas sensor - Google Patents

Abstract

To provide a constant-potential electrolytic gas sensor which is compact and capable of detecting inspection object gas even when the same is low in concentration.SOLUTION: A constant-potential electrolytic gas sensor comprises a laminated electrode structure body, having a working electrode, a counter electrode and a reference electrode, arranged inside a casing having an inspection object gas introduction port on an upper wall section. The laminated electrode structure has: the working electrode arranged opposite to the inspection object gas introduction port; an electrode composite body which is arranged below the working electrode and made up of the counter electrode and the reference electrode; and a sheet-like electrolyte holding member arranged between the working electrode and the electrode composite body. The electrode composite body is formed by arranging the counter electrode and the reference electrode with a distance therebetween on a surface of a pressure regulation film made of a hydrophobic porous material. The casing has a ventilation tube section inwardly extended from a lower wall section so as to be brought into contact with a lower surface of the pressure regulation film and an electrolyte chamber storing electrolyte around the ventilation tube section between the laminated electrode structure body and the lower wall section of the casing.SELECTED DRAWING: Figure 1

Description

The present invention relates to a compact and portable constant potential electrolytic gas sensor.

At present, for example, when detecting a toxic gas in a semiconductor manufacturing factory, the gas concentration can be detected with excellent selectivity, high sensitivity, and high accuracy for the target gas to be detected. , A constant potential electrolytic gas sensor using an electrolytic reaction is widely used.

As such a constant potential electrolytic gas sensor, Patent Document 1 describes electrode lamination in which a working electrode, a reference electrode, and a counter electrode are laminated via an electrolytic solution holding member made of a hydrophilic non-woven fabric impregnated with an electrolytic solution. Those provided with a structure are disclosed.

In this constant potential electrolytic gas sensor, the electrode laminated structure is laminated on the working electrode, the reference electrode laminated on the working electrode via the electrolytic solution holding member, and on the reference electrode via the electrolytic solution holding member. It consists of a counter electrode and a pressure adjusting film integrally provided on the counter electrode. A cylindrical partition wall is provided around the electrode laminated structure, and an electrolytic solution chamber for accommodating the electrolytic solution is formed around the partition wall. Further, the electrolytic solution holding member between the reference electrode and the counter electrode and the pressure adjusting film are formed so that four tongue pieces protruding outward in the surface direction are arranged at equal intervals in the circumferential direction. These tongue pieces are provided so as to extend into the electrolyte chamber via the partition wall.

Further, sulfuric acid is generally used as the electrolytic solution. Sulfuric acid absorbs water or evaporates water depending on the humidity of the environment in which the constant potential electrolytic gas sensor is used, and as a result, the amount of the electrolytic solution increases or decreases. Therefore, the electrolytic solution chamber is required to have a volume capable of accommodating the electrolytic solution even when the amount of the electrolytic solution increases.

U.S. Pat. No. 7,608,177

However, the constant potential electrolytic gas sensor having the above configuration has the following problems.
In the constant potential electrolytic gas sensor described in Patent Document 1, since an electrolytic solution holding member is provided between the working electrode and the reference electrode and between the reference electrode and the counter electrode, the reference electrode and the counter electrode can be used. Twice the amount of electrolytic solution is required as compared with the one configured in the same plane. Therefore, twice the volume of the electrolytic solution chamber is required, and therefore, it is difficult to further reduce the size of the constant potential electrolytic gas sensor.
Further, since the electrolytic solution chamber is formed around the electrode laminated structure, it is necessary to considerably reduce the area of the working electrode in order to form a small constant potential electrolytic gas sensor. Therefore, the sensitivity as a sensor is low, and therefore, it is difficult to detect a low-concentration detection target gas.

Therefore, an object of the present invention is to provide a constant potential electrolytic gas sensor capable of detecting a gas to be detected at a low concentration in a small size.

The constant-potential electrolytic gas sensor of the present invention is a constant-potential electrolytic gas sensor in which an electrode laminated structure having a working electrode, a counter electrode, and a reference electrode is arranged in a casing having a test gas introduction port on an upper wall portion. hand,
The electrode laminated structure includes the working electrode arranged to face the test gas introduction port, an electrode composite having the counter electrode and the reference electrode arranged below the working electrode, and the action. It is provided with a sheet-shaped electrolyte holding member impregnated with the electrolyte, which is arranged between the pole and the electrode composite.
The electrode composite is formed by forming the counter electrode and the reference electrode apart from each other on the upper surface of a pressure adjusting film made of a hydrophobic porous material.
The casing has a ventilation pipe portion that forms a ventilation hole and is provided so as to project inward from the lower wall portion and contact the lower surface of the pressure adjusting membrane.
An electrolytic solution chamber for accommodating the electrolytic solution is formed around the ventilation pipe portion between the electrode laminated structure and the lower wall portion of the casing.

The constant potential electrolytic gas sensor of the present invention includes a support plate that supports the electrode composite, and is provided with a support plate.
The pressure adjusting film comprises an electrode forming portion on which the counter electrode and the reference electrode are formed, and at least three or more tongue pieces protruding from the peripheral edge of the electrode forming portion.
The support plate has an electrode forming portion supporting portion that supports the electrode forming portion and a tongue piece portion supporting portion that supports the tongue piece portion formed around the electrode forming portion supporting portion.
The electrode forming portion support portion has a through hole for the ventilation pipe portion into which the tip end portion of the ventilation pipe portion is fitted.
The tongue piece support portion has a plurality of tongue piece through holes formed corresponding to each of the tongue pieces to allow the tongue piece to enter.
It is preferable that the tongue piece portion is formed so as to enter the through hole for the tongue piece portion and the tip portion of the tongue piece portion is located in the electrolytic solution chamber.

Further, in the constant potential electrolytic gas sensor of the present invention, the working electrode comprises a hydrophobic gas permeable film and an electrode catalyst layer formed on the lower surface of the gas permeable film.
The gas permeable film is arranged on the upper wall portion of the casing so as to close the test gas introduction port, and is welded to the upper wall portion so as to surround the test gas introduction port.

It is preferable that the pressure adjusting membrane is welded to the tip surface of the ventilation pipe portion so as to surround the ventilation hole.

Further, in the constant potential electrolytic gas sensor of the present invention, in the electrode laminated structure, a plurality of the working electrodes for detecting different types of detection target gases are arranged in the plane direction of the electrolytic solution holding member. It may be arranged apart.

In the present invention, "upper" and "lower" mean the constant potential when the constant potential electrolytic gas sensor of the present invention is arranged in a posture in which the surface of the casing on which the test gas inlet is formed faces upward. It indicates the direction in the electrolytic gas sensor. Therefore, for example, when the constant potential electrolytic gas sensor is arranged in a position in which the surface of the casing on which the gas inlet to be tested is formed faces downward, the "upper" and "lower" are actually in opposite directions, that is, "lower". When the constant potential electrolytic gas sensor is arranged in a casing in which the surface on which the test gas inlet is formed faces left, the "upper" and "lower" are actually Indicates the "left" and "right" directions, respectively.

In the constant potential electrolytic gas sensor of the present invention, the electrolytic solution holding member needs only be provided between the working electrode and the electrode composite, and thus the amount of the electrolytic solution can be reduced. It is possible to reduce the volume of the electrolyte chamber. Further, since the electrolytic solution chamber is formed between the electrode laminated structure and the lower wall portion of the casing, it is possible to form a working electrode having a sufficiently large area. Further, since the electrode composite is formed by forming a counter electrode and a reference electrode on the pressure adjusting film, it is not necessary to separately provide the pressure adjusting film, the number of parts is small, and the space inside the casing is reduced. It can be used efficiently.
Therefore, according to the present invention, it is possible to provide a constant-potential electrolytic gas sensor that is compact and can detect a low-concentration detection target gas.

It is explanatory cross-sectional view which shows the outline of the structure in the example of the constant potential electrolysis type gas sensor of this invention. It is an exploded perspective view of the constant potential electrolysis type gas sensor shown in FIG. FIG. 5 is an explanatory cross-sectional view showing an enlarged working electrode in the constant potential electrolytic gas sensor shown in FIG. 1. It is a perspective view of the support plate which supports the electrode composite in the constant potential electrolysis type gas sensor shown in FIG. It is a top view of the support plate which supports the electrode composite in the constant potential electrolysis type gas sensor shown in FIG.

Hereinafter, embodiments of the constant potential electrolytic gas sensor of the present invention will be described.
FIG. 1 is an explanatory sectional view showing an outline of a configuration in an example of a constant potential electrolytic gas sensor of the present invention. FIG. 2 is an exploded perspective view of the constant potential electrolytic gas sensor shown in FIG.
This constant-potential electrolysis gas sensor detects two types of detection target gases, for example, carbon monoxide and hydrogen sulfide, and has two working electrodes 21 and 22 for detecting hydrogen sulfide and carbon monoxide, respectively. It has a casing 10 for accommodating an electrode laminated structure 20 having a counter electrode 26 and a reference electrode 27.

The casing 10 is composed of a cylindrical casing main body 11 whose lower end is closed, and a disc-shaped lid member 12 which closes an opening at the upper end of the casing main body 11 to form an upper wall portion 14. The casing body 11 and the lid member 12 are each made of a thermoplastic resin such as polypropylene. The upper wall portion 14 is formed so that a plurality of test gas introduction ports 13 for introducing the test gas into the casing 10 extend through the upper wall portion 14 in the thickness direction.

At the center position of the bottom wall portion of the casing main body 11, that is, the lower wall portion 15 of the casing 10, a ventilation pipe portion 16 having a circular cross section is provided upward (inward) from the lower wall portion 15 along the axial direction of the casing main body 11. It is formed so as to protrude and come into contact with the lower surface of the pressure adjusting film 28 described later. The ventilation pipe portion 16 forms a ventilation hole V that leads from the outer surface of the lower wall portion 15 to the lower surface of the pressure adjusting film 28.

Two working pole terminals 40 and 41, counter electrode terminals 42 and reference pole terminals 43 are arranged so as to be spaced apart from each other in the circumferential direction around the ventilation pipe portion 16 in the lower wall portion 15 of the casing 10. There is.
An electrolytic solution chamber S for accommodating the electrolytic solution is formed around the ventilation pipe portion 16 between the electrode laminated structure 20 and the lower wall portion 15 of the casing 10. The electrolytic solution chamber S communicates with the space in which the electrode laminated structure 20 is arranged through a gap K between the peripheral wall portion 17 of the casing 10 and the support plate 30 described later.
Further, on the inner surface (upper surface) of the lower wall portion 15, a sealing resin material layer 45 formed by curing an adhesive such as an epoxy resin adhesive is provided on the working electrode terminals 40 and 41, the counter electrode terminals 42 and the reference electrode terminals. It is formed to cover 43. By providing the sealing resin material layer 45, the electrolytic solution chamber S has a liquid-tight sealing structure in which the working electrode terminals 40 and 41, the counter electrode terminals 42 and the reference electrode terminals 43 are not corroded by the electrolytic solution. When the resin material layer 45 for sealing is formed, the casing main body 11 is filled with an adhesive and then covered with a polypropylene film or the like, so that the adhesive rises along the inner wall surface of the casing main body treated with corona. This prevents the adhesive from filling up. If the filling amount of the adhesive is small, the volume of the electrolytic solution chamber S increases relatively, so that it is possible to cope with a wider range of humidity environments.

The electrode laminated structure 20 is arranged below two semi-circular sheet-shaped working electrodes 21 and 22 and the working electrodes 21 and 22 which are arranged so as to face the test gas introduction port 13 and are separated from each other. The electrode composite 25 is composed of a sheet-shaped electrolyte holding member 23 impregnated with the electrolyte, which is arranged between the working electrodes 21 and 22 and the electrode composite 25.

As shown in FIG. 3, the working electrodes 21 and 22 are configured by forming electrode catalyst layers 21b and 22b on gas permeable films 21a and 22a having hydrophobicity, respectively, and electrode catalyst layers 21b and 22b. Is arranged so as to be in contact with the electrolytic solution holding member 23. Further, each of the gas permeable films 21a and 22a at the working electrodes 21 and 22 is arranged so as to close the corresponding test gas introduction port 13. Further, the upper surfaces of the gas permeable films 21a and 22a are heat-welded to the lower surface (inner surface) of the upper wall portion 14 so as to surround the test gas introduction port 13. Since the gas permeable films 21a and 22a are heat-welded to the upper wall portion 14, it is possible to prevent the electrolytic solution from leaking from between the gas permeable films 21a and 22a and the upper wall portion 14. ..

The working poles 21 and 22 are electrically connected to one end of the working pole lead members 46 and 47, and the working pole terminals 40 and 41 are electrically connected to the other end of the working pole lead members 46 and 47. Has been done.
As a material constituting the lead members 46 and 47 for the working electrode, metals such as gold (Au), platinum (Pt), tungsten (W), niobium (Nb) and tantalum (Ta) can be used.
The lead members 46 and 47 for the working electrode may be linear or ribbon-shaped.

As the gas permeable films 21a and 22a, for example, a porous membrane made of a fluororesin such as polytetrafluoroethylene (PTFE) can be used.
The porous membrane preferably has a Garley number of 3 to 3000 seconds. The thickness and porosity of the porous membrane can be set so that the number of Garleys is within the above numerical range. For example, the porosity is 10 to 70% and the thickness is 0.01 to 1 mm. Is preferable.

The electrode catalyst layers 21b and 22b are fine particles of a catalyst metal insoluble in an electrolytic solution, fine particles of an oxide of the catalyst metal, fine particles of an alloy of the catalyst metal, or a mixture of these fine particles, or these fine particles and carbon. It is formed by catalyst fine particles such as a mixture with. As the catalyst metal insoluble in the electrolytic solution, for example, platinum (Pt), gold (Au), ruthenium (Ru), palladium (Pd), iridium (Ir) and the like can be used. Such electrode catalyst layers 21b and 22b are formed by preparing a paste containing catalyst fine particles and a binder, applying the paste to the surfaces of the gas permeable films 21a and 22a by screen printing or the like, and firing the paste. can do.

The electrode composite 25 is composed of a pressure adjusting film 28 made of a hydrophobic porous material, and a counter electrode 26 and a reference electrode 27 made of semicircular catalyst layers formed on the upper surface of the pressure adjusting film 28 so as to be separated from each other. Has been done. The pressure adjusting film 28 in the electrode composite 25 is arranged so as to close the ventilation hole V on the upper end surface of the ventilation pipe portion 16 in the casing 10. As a result, the internal space of the casing 10 is opened to the outside atmosphere through the pressure adjusting membrane 28 and the ventilation holes V. The constant potential electrolytic gas sensor can be used with the ventilation holes V closed. If a high-concentration interfering gas passes through the ventilation hole V and enters the inside of the constant potential electrolytic gas sensor and has an adverse effect, the air permeability of the ventilation hole V is positively lowered or completely blocked. A constant potential electrolytic gas sensor can also be used. Further, the lower surface of the pressure adjusting membrane 28 is heat-welded to the upper end surface of the ventilation pipe portion 16 so as to surround the ventilation hole V. Since the pressure adjusting membrane 28 is heat-welded to the upper end surface of the ventilation pipe portion 16, it is possible to prevent the electrolytic solution from leaking from between the pressure adjusting membrane 28 and the upper end surface of the ventilation pipe portion 16. ..

The counter electrode 26 and the reference pole 27 are electrically connected to one end of the counter electrode lead member 48 and the reference pole lead member 49, and the counter electrode terminal 42 is connected to the other ends of the counter electrode lead member 48 and the reference pole lead member 49. And the reference pole terminal 43 is electrically connected.
As a material constituting the counter electrode lead member 48 and the reference electrode lead member 49, metals such as gold (Au), platinum (Pt), tungsten (W), niobium (Nb) and tantalum (Ta) may be used. it can.

As the pressure adjusting film 28, for example, a porous film made of a fluororesin such as polytetrafluoroethylene (PTFE) can be used.
The porous membrane preferably has a Garley number of 3 to 3000 seconds. The thickness and porosity of the porous membrane can be set so that the number of Garleys is within the above numerical range. For example, the porosity is 10 to 70% and the thickness is 0.01 to 1 mm. Is preferable.

The catalyst layer constituting the counter electrode 26 and the reference electrode 27 is made of fine particles of a catalyst metal insoluble in an electrolytic solution, fine particles of an oxide of the catalyst metal, fine particles of an alloy of the catalyst metal, or a mixture of these fine particles. It is formed by catalyst fine particles. As the catalyst metal insoluble in the electrolytic solution, for example, platinum (Pt), gold (Au), ruthenium (Ru), palladium (Pd), iridium (Ir) and the like can be used. The catalyst layer constituting the counter electrode 16 and the reference electrode 27 is formed by preparing a paste containing catalyst fine particles and a binder, applying this paste to the surface of the pressure adjusting film 28 by screen printing or the like, and firing the paste. be able to.

The catalyst layer forming the counter electrode 26 and the catalyst layer forming the reference electrode 27 may be formed of the same material, but are formed of different types of materials depending on the performance required for each. Is preferable. For example, since the catalyst layer constituting the counter electrode 26 is required to have a high current density and good reactivity, the catalyst layer constituting the counter electrode 26 is formed of platinum (Pt) and iridium oxide (IrO ₂ ). It is preferable that it is. On the other hand, the catalyst layer constituting the reference electrode 27 is required to have low coherence with hydrogen gas (H ₂ ) or the like generated by the reaction and to be difficult to form an oxide film. Therefore, the catalyst constituting the reference electrode 27 is required. The layer is preferably formed of iridium oxide (IrO ₂ ) or platinum (Pt) having high potential stability.

The pressure adjusting film 28 has a circular electrode forming portion 28a on which the counter electrode 26 and the reference electrode 27 are formed, and three or more (4 in the illustrated example) extending radially outward from the outer peripheral edge of the electrode forming portion 28a, respectively. It is composed of a rectangular tongue piece portion 28b. Each of the tongue piece portions 28b is formed so as to be arranged at equal intervals in the circumferential direction of the electrode forming portion 28a.

The electrolyte holding member 23 of this example has, for example, a circular plane and has an area larger than the electrode forming portion 28a in the pressure adjusting membrane 28. As a result, it is possible to ensure a sufficiently high wettability of the electrolytic solution to each electrode.
The thickness of the electrolytic solution holding member 23 is such that the volume of the electrolytic solution holding member 23 can be as small as possible while being able to impregnate a sufficient amount of the electrolytic solution. It is set to 0.1 to 1 mm. With such a configuration, highly reliable gas detection can be performed even in a high humidity environment.
As the electrolytic solution holding member 23, for example, a glass fiber filter paper or a non-woven fabric made of glass fiber, PP fiber, PP / PE composite fiber or ceramic fiber can be used.

A support plate 30 for supporting the composite electrode body 25 is provided at the upper end portion of the ventilation pipe portion 16. A perspective view of the support plate 30 is shown in FIG. 4, and a top view of the support plate 30 is shown in FIG.
The support plate 30 has an electrode forming portion supporting portion 31 that supports the electrode forming portion 28a of the pressure adjusting film 28 and a tongue piece portion 28b of the pressure adjusting film 28 formed around the electrode forming portion supporting portion 31. It has a tongue piece support portion 35 to support.

In the illustrated example, a step portion is formed on the upper surface of the support plate 30 between the electrode forming portion supporting portion 31 and the tongue piece portion supporting portion 35. As a result, a substantially circular recess R for receiving the electrode forming portion 28a in the pressure adjusting film 28 is formed on the electrode forming portion supporting portion 31. Further, on the upper surface of the tongue piece portion support portion 35, a plurality of grooves G for guiding the tongue piece portion 28b corresponding to each of the tongue piece portions 28b in the pressure adjusting film 28 are formed from the recess R to the support plate 30. It is formed so as to extend in the radial direction toward the outer peripheral surface of the.

At the central position of the electrode forming portion support portion 31, a through hole 32 for the ventilation pipe portion having an inner diameter suitable for the outer diameter of the ventilation pipe portion 16 in the casing 10 is formed. The tip portion of the ventilation pipe portion 16 is fitted into the through hole 32 for the ventilation pipe portion.
Further, the tongue piece support portion 35 is formed with through holes 36 for the tongue piece at each bottom surface position of the groove G. Each of the tongue piece portions 28b in the pressure adjusting membrane 28 enters the tongue piece portion through hole 36, and the tip portion of the tongue piece portion 28b is formed so as to be located in the electrolyte chamber S. According to such a configuration, the internal pressure of the casing 10 can be kept constant by ventilating the outside air to the inside of the casing 10 regardless of the posture of the constant potential electrolytic gas sensor.

In this constant potential electrolytic gas sensor, the working poles 21 and 22 and the reference pole 27 are maintained at a constant potential according to the type of the gas to be detected by, for example, a potentiostat circuit (not shown). Then, when the detection target gas is contained in the test gas introduced from the test gas introduction port 13 of the casing 10, the test gas is the gas permeable film 21a at the working electrodes 21 and 22. When the gas passes through 22a and comes into contact with the electrode catalyst layers 21b and 22b, an oxidation reaction occurs in the electrode catalyst layers 21b and 22b, and a reduction reaction occurs in the counter electrode 26.

For example, when the detection target gas is hydrogen sulfide (H2 S) is, in the electrode catalyst layer 21b of the working electrode _{21, H 2 S + 4H 2} O → H 2 SO 4 + 8H + + 8e - oxidation reaction occurs, the other hand, the counter electrode in ^{_{26, 2O 2 + 8H + +}} 8e - → 4H 2 O reduction reaction occurs.
Further, for example, when the gas to be detected is carbon monoxide (CO), an oxidation reaction of CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻ occurs in the electrode catalyst layer 22b at the working electrode 22, while at the counter electrode 26. ^{_{, 1 / 2O 2 + 2H +}} + 2e - → H 2 O of the reduction reaction.

At this time, since the value of the current generated between the working poles 21 and 22 and the counter electrode 26 is proportional to the concentration of the detection target gas, the current flowing between the working poles 21 and 22 and the counter electrode 26 is measured. , The concentration of the detection target gas in the test gas can be measured.

In the constant potential electrolytic gas sensor of the present invention, the electrolytic solution holding member 23 need only be provided between the working electrodes 21 and 22 and the electrode composite 25, thereby reducing the amount of the electrolytic solution. Therefore, it is possible to reduce the volume of the electrolytic solution chamber S. Further, since the electrolytic solution chamber S is formed between the electrode laminated structure 20 and the lower wall portion of the casing 10, it is possible to form working electrodes 21 and 22 having a sufficiently large area. Further, since the electrode composite 25 is formed by forming the counter electrode 26 and the reference electrode 27 on the pressure adjusting film 28, it is not necessary to separately provide the pressure adjusting film, the number of parts is small, and the casing 10 is used. The space inside the can be used efficiently.
Therefore, according to the present invention, it is possible to provide a constant-potential electrolytic gas sensor that is compact and can detect a low-concentration detection target gas.

Although an example of the embodiment of the constant potential electrolytic gas sensor of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made.
For example, the number of working electrodes may be one or three or more.
Also, the detection target gas is not limited to carbon monoxide and hydrogen sulfide, for example, not limited to hydrogen sulfide (H ₂ S) and carbon monoxide (CO), sulfur dioxide (SO _2), chlorine (Cl ₂₎ , Ammonia (NH ₃ ), nitrogen dioxide (NO ₂ ) and other toxic gases.

10 Casing 11 Case sink body 12 Lid member 13 Test gas inlet 14 Upper wall part 15 Lower wall part 16 Ventilation pipe part 17 Peripheral wall part 20 Electrode laminated structure 21, 22 Working electrode 23 Electrode holding member 25 Electrode composite 26 Counter electrode 27 Reference electrode 28 Pressure adjustment film 28a Electrode forming part 28b Tongue piece part 30 Support plate 31 Electrode forming part support part 32 Through hole for ventilation pipe part 35 Tongue piece support part 36 Through hole for tongue piece 40, 41 Working electrode terminal 42 Counter electrode terminal 43 Reference electrode terminal 45 Sealing resin material layer G Groove K Gap R Recess S Electrolyte chamber V Vent

Claims (4)

A constant-potential electrolytic gas sensor in which an electrode laminated structure having an action electrode, a counter electrode, and a reference electrode is arranged in a casing having a test gas introduction port on an upper wall portion.
The electrode laminated structure includes the working electrode arranged to face the test gas introduction port, an electrode composite having the counter electrode and the reference electrode arranged below the working electrode, and the action. It is provided with a sheet-shaped electrolyte holding member impregnated with the electrolyte, which is arranged between the pole and the electrode composite.
The electrode composite is formed by forming the counter electrode and the reference electrode apart from each other on the upper surface of a pressure adjusting film made of a hydrophobic porous material.
The casing has a ventilation pipe portion that forms a ventilation hole and is provided so as to project inward from the lower wall portion and contact the lower surface of the pressure adjusting membrane.
A constant-potential electrolytic gas sensor characterized in that an electrolytic solution chamber for accommodating an electrolytic solution is formed around the ventilation pipe portion between the electrode laminated structure and the lower wall portion of the casing. A support plate for supporting the electrode composite is provided.
The pressure adjusting film comprises an electrode forming portion on which the counter electrode and the reference electrode are formed, and at least three or more tongue pieces protruding from the peripheral edge of the electrode forming portion.
The support plate has an electrode forming portion supporting portion that supports the electrode forming portion and a tongue piece portion supporting portion that supports the tongue piece portion formed around the electrode forming portion supporting portion.
The electrode forming portion support portion has a through hole for the ventilation pipe portion into which the tip end portion of the ventilation pipe portion is fitted.
The tongue piece support portion has a plurality of tongue piece through holes formed corresponding to each of the tongue pieces to allow the tongue piece to enter.
The constant potential electrolysis according to claim 1, wherein the tongue piece portion enters the through hole for the tongue piece portion, and the tip end portion of the tongue piece portion is formed so as to be located in the electrolytic solution chamber. Type gas sensor. The working electrode includes a gas-permeable film having hydrophobicity and an electrode catalyst layer formed on the lower surface of the gas-permeable film.
The gas permeable film is arranged on the upper wall portion of the casing so as to close the test gas introduction port, and is welded to the upper wall portion so as to surround the test gas introduction port, and the pressure adjusting film is provided. The constant potential electrolytic gas sensor according to claim 1 or 2, wherein the gas sensor is welded to the tip end surface of the ventilation pipe portion so as to surround the ventilation hole. A claim characterized in that, in the electrode laminated structure, a plurality of the working electrodes for detecting different types of detection target gases are arranged so as to be separated from each other in the surface direction of the electrolytic solution holding member. The constant potential electrolytic gas sensor according to any one of items 1 to 3.

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