JP2017032427A - Controlled potential electrolysis gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controlled potential electrolysis gas sensor that can suppress formation of air bubbles in a surface of a counter electrode.SOLUTION: A controlled potential electrolysis gas sensor X includes: a reaction electrode 11, which causes a detected gas to make an electrochemical reaction as a gas electrode 10 detecting gas; a counter electrode 12 opposed to the reaction electrode 11; a reference electrode 13 controlling the potential of the reaction electrode 11; and air bubble formation suppressing means 50, which suppresses formation of air bubbles at least on the surface of the counter electrode 12, the electrodes 11, 12, and 13 being in contact with an electrolyte 20 in an electrolytic cell 30.SELECTED DRAWING: Figure 1

Description

  In the present invention, a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell. The present invention relates to a constant potential electrolysis gas sensor.

  A conventional constant potential electrolytic gas sensor is configured such that an electrode is provided facing an electrolytic solution storage part of an electrolytic cell in which an electrolytic solution is densely stored. For example, an electrode is detected as a gas electrode that detects gas. There are provided three electrodes: a reaction electrode for electrochemically reacting gas, a counter electrode for the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode. A potentiostat circuit for setting the potential is connected. As the material of the three electrodes, a gas-permeable porous PTFE film having water repellency is coated with a noble metal catalyst such as platinum, gold, palladium, etc. As an electrolyte, an acidic aqueous solution such as sulfuric acid or phosphoric acid is used. Was used.

  In addition, the constant potential electrolytic gas sensor generates a current corresponding to the change in the surrounding environment between the reaction electrode and the counter electrode by controlling the potential of the reaction electrode to be constant with respect to the change in the surrounding environment. . Then, by utilizing the fact that the potential of the reaction electrode does not change and the oxidation-reduction potential varies depending on the gas type, it becomes possible to selectively detect the gas depending on the set potential of the potentiostat circuit. Further, by changing the catalyst used for the gas electrode, it is possible to have high selectivity for the target gas.

  Note that the above-described constant potential electrolytic gas sensor, which is a conventional technique in the present invention, is a general technique, and therefore does not show any prior art documents such as patent documents.

  In the above-described constant potential electrolytic gas sensor, there is one in which an air layer and an oxygen permeable film that transmits oxygen are provided in the gas ventilation portion formed on the side of the counter electrode and the reference electrode.

  For example, when the temperature suddenly changes from low temperature to high temperature, the air layer may expand and bubbles may enter the sensor through a through hole formed on the gas ventilation part side. If the mixed bubbles reach the surface of the electrode, for example, bubbles are formed on the surface of the counter electrode, the contact area (wetting area) between the electrolyte and the counter electrode may decrease, and the indicated value of the sensor may suddenly increase. is there. In this case, since it takes time until the bubbles formed on the surface of the counter electrode disappear and the sensor output is stabilized, it is inconvenient in the operation of the sensor.

  Accordingly, an object of the present invention is to provide a constant potential electrolytic gas sensor that can suppress the formation of bubbles at least on the surface of the counter electrode.

  In order to achieve the above object, a constant potential electrolytic gas sensor according to the present invention controls a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode for the reaction electrode, and a potential of the reaction electrode. A constant potential electrolytic gas sensor provided with a reference electrode in contact with an electrolyte contained in an electrolytic cell, the first characteristic configuration of which is a bubble that suppresses the formation of bubbles at least on the surface of the counter electrode It is in the point provided with formation suppression means.

  According to this configuration, by providing the bubble formation suppressing means, even when the temperature of the sensor changes suddenly due to the influence of the disturbance, for example, it is difficult for bubbles to be mixed from a through hole formed on the counter electrode side. In addition, even when bubbles are mixed through the through hole, at least the bubbles mixed on the surface of the counter electrode are difficult to reach. Accordingly, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode, and thus it is possible to suppress a sudden change in the indicated value of the sensor.

  The second characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the bubble formation suppressing means is a water retaining member that absorbs and holds the electrolytic solution.

  According to this configuration, if the bubble formation suppressing means is a water retaining member, it is more difficult for bubbles mixed in at least the surface of the counter electrode facing the electrolyte container to reach, and it is ensured that bubbles are formed on the surface of the counter electrode. Can be suppressed.

  A third characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that an oxygen permeable membrane that transmits oxygen is disposed in a gas ventilation portion that discharges gas formed on the counter electrode and the reference electrode. .

  According to this configuration, by providing the oxygen permeable membrane, it is possible to prevent the surrounding interference gas (other than oxygen) from entering the counter electrode and the reference electrode from the gas vent.

  The fourth characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the filling rate of the water retaining member is 90% or more.

  According to this configuration, since the surface of each gas electrode can be reliably covered, it is difficult for the mixed bubbles to reach the surface of each gas electrode, and it is ensured that bubbles are formed on the surface of each gas electrode. Can be suppressed. As a result, when bubbles generated due to electrode reactions or the like in each gas electrode, or air dissolved in the electrolyte solution due to a rapid temperature change, or by intrusion of air in a sudden pressurization state, It can be avoided that the surface of each gas electrode is covered with air, the reaction area of each gas electrode is reduced, and the indication becomes unstable.

The fifth characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the water retention member has a bulk density of 0.05 to 0.30 g / cm ³ .

  According to this configuration, when the water retention member is disposed in the electrolyte container, the water retention member can be disposed so as to press each gas electrode to some extent, so that the contact state between the water retention member and each gas electrode is ensured. Can be secured. Thereby, at least the bubbles mixed on the surface of the counter electrode are more difficult to reach.

It is the schematic which shows the constant potential electrolytic gas sensor of this invention. It is the schematic which shows the constant potential electrolytic gas sensor of another embodiment. 3 is a graph obtained by examining the change in the indicated value in the constant potential electrolytic gas sensor of the present invention in Example 1. 4 is a graph obtained by examining a change in indicated value in a constant potential electrolytic gas sensor of a comparative example in Example 1. 6 is a graph obtained by examining the change in the indicated value in the constant potential electrolytic gas sensor of the present invention in Example 2. 6 is a graph showing a change in indicated value in a constant potential electrolytic gas sensor of a comparative example in Example 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the constant potential electrolytic gas sensor X controls a reaction electrode 11 that causes a gas to be detected to electrochemically react as a gas electrode 10 that detects gas, a counter electrode 12 with respect to the reaction electrode 11, and a potential of the reaction electrode 11. The reference electrode 13 is provided so as to be in contact with the electrolytic solution 20 accommodated in the electrolytic cell 30. This constant potential electrolytic gas sensor X includes a bubble formation suppressing means 50 that suppresses the formation of bubbles on at least the surface of the counter electrode 12.

  The reaction electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying and baking a paste made of a known electrode material on the surface of a porous gas permeable film 14 having water repellency. The gas permeable membrane 14 may be any membrane as long as it is hydrophobic and has a property of transmitting gas. For example, a porous PTFE (polytetrafluoroethylene) membrane having chemical resistance may be used. it can.

  The reaction electrode 11, the counter electrode 12, and the reference electrode 13 are composed of a gas diffusion electrode including a catalyst and a hydrophobic resin (gas permeable membrane 14). As the catalyst, platinum (Pt), gold (Au), ruthenium (Ru), Ruthenium oxide (RuO2), palladium (Pd), platinum-supported carbon (Pt / C), etc. are preferably used.

  The counter electrode 12 and the reference electrode 13 of the present embodiment have a mode in which the counter electrode 12 is formed in the upper half and the reference electrode 13 is formed in the lower half in one gas permeable membrane 14, but is limited to such a mode. It is not something. Between the counter electrode 12 and the reference electrode 13, the slit 14a in which an electrode is not formed is formed.

  The reaction electrode 11 and the reference electrode 13 are disposed to face each other, and the counter electrode 12 and the reference electrode 13 are disposed on the gas ventilation portion 33 side. A space between the reaction electrode 11, the counter electrode 12, and the reference electrode 13 serves as an electrolyte solution storage unit 31 that stores the electrolyte solution 20. The electrolytic solution 20 may be an acidic aqueous solution such as sulfuric acid or phosphoric acid, but is not limited thereto. The gas to be detected is introduced into the sensor from the gas introduction part 32 and reacts on the reaction electrode 11.

  Two buffer filters 35 are disposed on the gas introduction part 32 side of the reaction electrode 11 and on the gas ventilation part 33 side of the counter electrode 12 and the reference electrode 13, respectively. The buffer filter 35 is a buffer film that prevents deformation of each electrode and prevents leakage of the electrolyte solution 20. For example, a porous Teflon (registered trademark) film having a porosity of about 80% can be used. It is not limited to.

  Each gas electrode 10, gas permeable membrane 14, buffer filter 35, and O-ring 15a are fixed by a lid member 16 (16A, 16B) of the electrolytic cell 30.

  An internal pressure adjusting hole 17 having a small diameter of about 0.5 to 2 mm is formed at one end of the electrolytic cell 30. A porous sheet 18 is disposed on the internal pressure adjusting hole 17 on the side of the electrolytic solution containing portion 31. The electrolyte storage unit 31 has two large-diameter storage units 31b through a small-diameter channel 31a. When the flow path 31a has a small diameter of about 2 to 4 mm, the electrolytic solution 20 is less likely to flow backward from one housing portion 31b to the other housing portion 31b due to the surface tension of the electrolytic solution 20. The electrolytic cell 30 and the lid member 16 constituting the housing may be made of a synthetic resin having corrosion resistance, for example, a metal such as hard vinyl chloride or nickel alloy.

  Through holes 16a and 16b are respectively formed in the lid member 16A formed on the gas introduction part 32 side and the lid member 16B formed on the gas ventilation part 33 side, and gas is introduced through the through hole 16a. The gas is discharged and introduced through the through hole 16b. Since the position where the through hole 16b is formed corresponds to the position of the slit 14a where no electrode is formed, gas can be discharged or introduced through the slit 14a and the through hole 16b.

  An air layer 40 and an oxygen permeable film 41 that allows oxygen to pass through are disposed in the gas ventilation part 33 that discharges the gas formed on the counter electrode 12 and the reference electrode 13 side. The oxygen permeable membrane 41 is not particularly limited as long as it has oxygen permeation performance. For example, tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA). A conventionally well-known thing is applicable.

  By disposing the oxygen permeable membrane 41 as in the present configuration, it is possible to prevent surrounding interference gas (other than oxygen) from entering the counter electrode 12 and the reference electrode 13 from the gas ventilation portion 33.

  The constant potential electrolytic gas sensor X of the present invention includes a bubble formation suppressing means 50 that suppresses formation of bubbles on at least the surface of the counter electrode 12. The bubble formation suppressing means 50 may be configured to suppress the formation of bubbles on the surface of the other gas electrode 10 (reaction electrode 11 and reference electrode 13) in addition to the counter electrode 12.

  For example, when the temperature suddenly changes from low temperature to high temperature, the air layer 40 may expand greatly and bubbles may enter through the through-hole 16b formed on the gas ventilation part 33 side. If the mixed bubbles reach the surface of the electrode and, for example, bubbles are formed on the surface of the counter electrode 12, the contact area between the electrolytic solution 20 and the counter electrode 12 may decrease, and the indicated value of the sensor may suddenly increase. . By providing the bubble formation suppressing means 50 of the present invention, it is difficult for air bubbles to be mixed from the through hole 16b even when the temperature of the sensor is suddenly changed due to the influence of disturbance, and the bubble is prevented from passing through the through hole 16b. Even when the bubbles are mixed, at least the bubbles mixed on the surface of the counter electrode 12 are difficult to reach. Accordingly, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode 12, and thus it is possible to suppress a sudden change in the indicated value of the sensor.

  In the present embodiment, the case where the water retention member 37 that absorbs and holds the electrolytic solution 20 is disposed in the electrolytic solution storage unit 31 as the bubble formation suppressing unit 50 will be described, but is not limited thereto.

  If the bubble formation suppressing means 50 is the water retaining member 37, it is more difficult for bubbles mixed in at least the surface of the counter electrode 12 facing the electrolyte container 31 to reach, and it is ensured that bubbles are formed on the surface of the counter electrode 12. Can be suppressed.

  The water retaining member 37 may be disposed so as to suppress at least the formation of bubbles on the surface of the counter electrode 12, and preferably suppresses the formation of bubbles on the surfaces of the reaction electrode 11 and the reference electrode 13. What is necessary is just to arrange | position. At this time, the water retention member 37 is preferably disposed so as to cover the entire surface (or most) of each gas electrode 10.

  For example, the water retaining member 37 can be filled in the entire surface (100%) of one accommodating portion 31b (the side where the gas electrode 10 is disposed) in the electrolyte accommodating portion 31 as in the present embodiment. However, the present invention is not limited to such a mode, and the water retaining member 37 is filled with, for example, 90% or more, specifically about 90 to 95% of one housing portion 31b (the side on which the gas electrode 10 is disposed). What is necessary is just to fill so that it may become a rate. By filling the water retaining member 37 at such a ratio, the surface of each gas electrode 10 can be reliably covered, so that the mixed bubbles are less likely to reach the surface of each gas electrode 10. It is possible to reliably suppress the formation of bubbles on the surface. As a result, when bubbles generated by electrode reactions or the like in each gas electrode 10 or air dissolved in the electrolyte solution due to a rapid temperature change occurs, or when air invades rapidly in a pressurized state, It can be avoided that the surface of each gas electrode 10 is covered with air, the reaction area of each gas electrode 10 is reduced, and the indication becomes unstable.

  Since the water retaining member 37 is an embodiment that absorbs and holds the electrolytic solution 20, the water retaining member 37 has a space in which the electrolytic solution 20 can be retained. Therefore, even if it is a case where the water retention member 37 is filled in the whole surface of the accommodating part 31b, the contact state of each gas electrode 10 and the electrolyte solution 20 can be maintained favorable.

The water retaining member 37 is not particularly limited as long as it is a water absorbing member capable of holding the electrolytic solution 20 such as a water retaining fiber (for example, glass fiber, ceramic fiber, etc.) or a water absorbing polymer. The bulk density of the water retaining member 37 is preferably 0.05 to 0.30 g / cm ³ . For example, when the bulk density of the water retaining member 37 is about 0.22 g / cm ³ and the space ratio is about 90%, specifically, MGP (manufactured by Nippon Sheet Glass Co., Ltd.) can be used. When the density is about 0.18 g / cm ³ and the space ratio is about 90%, specifically, MC paper (manufactured by Nippon Sheet Glass Co., Ltd.) can be used, and the bulk density of the water retaining member 37 is 0.08 g. When about / cm ³ and the space ratio are about 90%, specifically, OR-125 (manufactured by Asahi Textile Industry Co., Ltd.) can be used. However, the bulk density of the water retaining member 37 and the actual product are not limited to these. For example, a plurality of such water retaining members 37 may be arranged in the electrolyte solution storage unit 31 in a stacked manner. With the structure of the water retaining member 37 described above, the water retaining member 37 can be pushed to some extent to fill the accommodating portion 31b, and the water retaining member 37 can be arranged to press each gas electrode 10 to some extent. And the contact state between the gas electrodes 10 can be ensured. As a result, at least air bubbles mixed on the surface of the counter electrode 12 are more difficult to reach.

  Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the reaction electrode 11 due to a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the reaction electrode 11. It is used as a gas detection device by connecting to a gas detection circuit (not shown). The constant potential electrolytic gas sensor X of the present invention is used for detecting oxygen gas, hydride gas such as silane, phosphine, germane, arsine and diborane, and detecting toxic gas such as carbon monoxide and hydrogen sulfide.

  On the gas introduction part 32 side, the lid member 16A is provided with filter means 60 for filtering the interference gas. The filter means 60 is disposed on a frame 16c formed on the lid member 16A. Specifically, the filter means 60 has a structure in which a plurality of filter layers 61 including activated carbon and silica gel for filtering interference gas are accommodated in a cylindrical container 60a, and both sides of the filter layers 61 are holding members such as meshes. However, the present invention is not limited to such a mode.

[Another embodiment]
In the above-described embodiment, the aspect in which the gas vent 33 is provided with the air layer 40 and the oxygen permeable membrane 41 that transmits oxygen has been described. However, the present invention is not limited thereto, and the air layer 40 and the oxygen permeable membrane 41 are not provided, and the cylindrical member 34 in which the pinhole 34a is formed is disposed in the through hole 16b on the gas ventilation portion 33 side. You may do it (FIG. 2).

  Examples of the cylindrical member 34 include ceramics such as alumina and zirconia, but are not limited thereto. The long dimension of the cylindrical member is 2.0 mm or more, preferably 2.0 to 6.0 mm. The diameter of the pinhole 34a is preferably about 0.05 mm.

  After the cylindrical member 34 is disposed in the through hole 16b, the gas ventilation part 33 side may be sealed with a sealing means 36 such as an adhesive or packing in order to ensure airtightness other than the pinhole 34a.

  By providing the cylindrical member 34 as in this configuration, the gas flow on the gas ventilation portion 33 side can be made only to the pinhole 34a. Thereby, it is possible to prevent bubbles from entering the inside of the sensor due to the expansion of the air layer 40 when the temperature changes suddenly. In addition, by making the through hole 16b on the gas ventilation portion 33 side small and long, interference gas or the like is less likely to be mixed into the inside of the sensor (electrolyte accommodating portion 31 or the like). Thereby, since it becomes difficult for air bubbles to be mixed from the through hole 16b, the cylindrical member 34 in which the pinhole 34a is formed can be used as the air bubble formation suppressing means 50.

  Therefore, when the cylindrical member 34 in which the pinhole 34a is formed is provided, the water retaining member 37 in the above-described embodiment may be provided, or even if not provided, at least the surface of the counter electrode 12 by the cylindrical member 34. It is possible to suppress the formation of bubbles on the surface, and thus it is possible to suppress a sudden change in the indicated value of the sensor.

  When both the cylindrical member 34 and the water retaining member 37 are provided, it is possible to suppress the formation of bubbles on the surface of the counter electrode 12 more reliably.

  The shape of the cylindrical member 34 is preferably a columnar shape, but is not limited thereto, and may be an aspect such as a prismatic shape.

  One or more pinholes 34a may be provided in the cylindrical member 34. The number of pinholes 34a is not particularly limited. In the present embodiment, a case where one pinhole 34a is formed in each cylindrical member 34 will be described.

  By providing a plurality of pinholes 34a, the amount of gas introduced can be adjusted by the number of pinholes 34a. Even if condensation occurs in the gas introduction part 32, if a plurality of pinholes 34a are formed, all the pinholes 34a are not easily blocked by condensation, and gas discharge or introduction due to gas reaction is hindered. Can be prevented in advance. Since the amount of gas introduced can be adjusted not only by the number of pinholes but also by the length and diameter of the pinholes, it may be set appropriately according to the interference gas to be suppressed.

[Example 1]
Examples of the present invention will be described.
The constant potential electrolytic gas sensor X of the present example was set as the following mode.
That is, in the controlled potential electrolytic gas sensor X of the embodiment of FIG. 1, the buffer filter 35 having a thickness of 1 mm is a porous Teflon (registered trademark) membrane (PTFE membrane), the water retaining member 37 is a glass fiber member, and oxygen permeation is performed. The membrane 41 was made of tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), the filter layer 61 was made of four activated carbon layers, and the holding member 62 was made of SUS mesh. Further, the diameters of the through holes 16a and 16b were 2 mm, and the width of the slit 14a formed between the counter electrode 12 and the reference electrode 13 was 1.5 mm.

  Using such a constant potential electrolytic gas sensor X, how the indicated value of the sensor changes when the temperature of the sensor changes suddenly (from -10 ° C. to 50 ° C.) due to the influence of disturbance, Examined. In addition, the sensor which does not provide the bubble formation suppression means 50 (water retention member 37) was used as the constant potential electrolytic gas sensor of the comparative example.

  As a result, in the constant potential electrolysis gas sensor X (FIG. 3) of the present invention, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode 12 by the water retaining member 37 even when a sudden temperature change is applied. The sensor reading did not show any significant fluctuations and was considered stable.

  On the other hand, in the constant potential electrolysis gas sensor (FIG. 4) of the comparative example, when a sudden temperature change is applied, the water retaining member 37 is not provided, so that bubbles enter the sensor and the bubbles touch the electrode due to the influence of disturbance. It was thought that the sensor output fluctuated greatly because of moving away and away, and the sensor output was unstable.

[Example 2]
In the constant potential electrolysis gas sensor X of another embodiment described above, how the indicated value of the sensor changes when the temperature of the sensor changes abruptly (−10 ° C. to 50 ° C.) due to the influence of disturbance, Examined.

  The constant potential electrolysis gas sensor X of the present embodiment is configured such that the water retaining member 37 and the oxygen permeable membrane 41 are not used, and the cylindrical member 34 in which the pinhole 34a is formed is disposed. The long dimension of the said cylindrical member 34 was 3.0 mm, and the diameter of the pinhole 34a was 0.05 mm.

  In addition, the sensor which does not provide a pinhole was used as a constant potential electrolysis type gas sensor of a comparative example. That is, the diameter of the through hole 16b on the gas ventilation part 33 side in this sensor was 2.0 mm, and the long dimension was 2.0 mm.

  As a result, since the same data as in FIG. 3 was obtained in any of the constant potential electrolysis gas sensor X of this example and the constant potential electrolysis gas sensor of the comparative example (data not shown), there was no invasion of bubbles. The sensor reading did not show any significant fluctuations and was considered stable.

  On the other hand, it was examined how the indicated value of the sensor changes when there is an influence of the surrounding interference gas as an influence of the disturbance.

  At this time, the fluctuation of the indicated value when the hydrogen gas of 1000 ppm was changed to the diffusion state in the state where the gas introduction part 32 side was closed in consideration of the influence of the interference gas was examined. The results are shown in FIG. 5 (constant potential electrolytic gas sensor X of the present invention) and FIG. 6 (constant potential electrolytic gas sensor of comparative example). Two sensors were used for each sensor.

  As a result, in the controlled potential electrolysis gas sensor X (FIG. 5) of the present invention, the indicated value of the sensor was not observed to fluctuate greatly and was considered stable. Therefore, it was confirmed that the constant potential electrolysis gas sensor X of the present invention has the same performance as the case where the oxygen permeable membrane is used even if interference gas exists in the surroundings.

  On the other hand, in the constant potential electrolytic gas sensor of the comparative example (FIG. 6), the indicated value of the sensor fluctuated greatly, and the sensor output was considered unstable. For this reason, in the constant potential electrolytic gas sensor of the comparative example, the diameter of the through hole 16b is larger than the pinhole 34a of the constant potential electrolytic gas sensor X of the present invention. It was confirmed that gas could easily enter and the instructions were not stable.

  From this, it was recognized that in the potentiostatic gas sensor X of another embodiment in which the oxygen permeable membrane 41 is not provided, it is necessary to dispose the cylindrical member 34 in which the pinhole 34a having a small diameter is formed.

  In the present invention, a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell. It can utilize for the constant potential electrolytic gas sensor provided.

X Constant Potential Electrolytic Gas Sensor 10 Gas Electrode 11 Reaction Electrode 12 Counter Electrode 13 Reference Electrode 20 Electrolytic Solution 30 Electrolytic Tank 37 Water Retaining Member 41 Oxygen Permeation Membrane 50 Bubble Formation Inhibiting Means

Claims (5)

As a gas electrode for detecting gas, a reaction electrode for electrochemically reacting a gas to be detected, a counter electrode for the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode were provided so as to come into contact with an electrolytic solution contained in an electrolytic cell. A constant potential electrolytic gas sensor,
A constant potential electrolytic gas sensor provided with bubble formation suppressing means for suppressing formation of bubbles on at least the surface of the counter electrode.   The constant potential electrolytic gas sensor according to claim 1, wherein the bubble formation suppressing means is a water retention member that absorbs and holds the electrolytic solution.   The constant potential electrolytic gas sensor according to claim 2, wherein an oxygen permeable film that allows oxygen to pass through is provided in a gas ventilation portion that vents a gas formed on the side of the counter electrode and the reference electrode.   The constant potential electrolytic gas sensor according to claim 2 or 3, wherein a filling rate of the water retaining member is 90% or more. The constant potential electrolytic gas sensor according to any one of claims 2 to 4, wherein the water retention member has a bulk density of 0.05 to 0.30 g / cm ³ .

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