JP6315983B2 - Constant potential electrolytic gas sensor - Google Patents

Description

  The present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. The present invention relates to a constant potential electrolytic gas sensor provided facing a housing portion.

  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 working electrode for electrochemically reacting gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. A potentiostat circuit for setting the potential is connected. As the material for the three electrodes, a gas-permeable porous PTFE film having water repellency and a noble metal catalyst such as platinum, gold, and palladium are used, and as an electrolyte, sulfuric acid, phosphoric acid, or the like is used. Acidic aqueous solutions, neutral salt aqueous solutions such as lithium bromide and calcium chloride, and the like have been used.

  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 a possibility that precipitates may be deposited on the reference electrode, for example, depending on the combination of the electrode material used and the electrolytic solution. In some cases, the precipitate floats in the electrolyte and may adhere to, for example, the working electrode. When the deposit adheres to the working electrode in this way, the potential of the electrode changes and the indicator current flows excessively. As a result, the concentration of the gas detected by the sensor becomes the actual gas concentration regardless of the presence or absence of the gas. There was a problem that it became larger than the concentration.

  Accordingly, an object of the present invention is to provide a constant potential electrolytic gas sensor capable of accurately detecting the actual gas concentration.

In order to achieve the above object, a constant potential electrolytic gas sensor according to the present invention controls a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode for the working electrode, and a potential of the working electrode. A constant potential electrolytic gas sensor provided with a reference electrode facing an electrolytic solution housing part of an electrolytic cell containing an electrolytic solution, the first characteristic configuration of the working electrode and the reference in the electrolytic solution housing unit Provided with an electrolyte solution permeable filter that does not allow solid suspended matter to permeate between the electrodes but allows the electrolyte solution to permeate, and is configured to protrude into the electrolyte solution storage portion, and to fix the electrolyte solution permeable filter In the point provided with the fixed part .

According to this configuration, even if the deposit deposited on the reference electrode is detached from the reference electrode and floats in the electrolyte, the solid suspension in which the deposit is suspended is applied to the working electrode by the electrolyte permeation filter. Can be prevented from moving to the side. As a result, it is possible to prevent the solid suspended matter from adhering to the surface of the working electrode, so that it is possible to prevent the indicator current from flowing excessively to the working electrode due to the solid suspended matter adhering. Therefore, the constant potential electrolytic gas sensor of the present invention can accurately detect the actual gas concentration.
Moreover, the electrolyte solution permeable filter can be securely fixed by being supported or adhered to the filter fixing part.

  The second characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is such that the working electrode is provided on the side of the gas conduction portion that opens to the side of the electrolytic cell, and the reference electrode is opened to the side of the electrolytic cell. And it is in the point provided in the side of the oxygen gas inlet provided facing the said gas conduction | electrical_connection part.

  According to this configuration, the gas conduction part and the oxygen gas inlet can be formed to face each other, and the working electrode and the reference electrode can be arranged to face each other, so that the constant potential electrolytic gas sensor can be configured in a compact manner. it can.

  The third characteristic configuration of the controlled potential electrolytic gas sensor according to the present invention is that at least one of the working electrode and the counter electrode is a carbon electrode, the reference electrode is a silver electrode, and the electrolytic solution is a lithium bromide solution. It is in.

  According to this configuration, it is possible to accurately detect a toxic gas having toxicity at an extremely low concentration.

  The fourth characteristic configuration of the potentiostatic gas sensor according to the present invention is that the gas to be detected is diborane.

  According to this structure, it can be set as the constant potential electrolytic type gas sensor which detects the diborane which is toxic gas used as semiconductor material gas.

It is sectional drawing which shows the constant potential electrolytic gas sensor of this invention. It is sectional drawing which shows the constant potential electrolytic gas sensor of another embodiment.

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 of the present invention includes a working 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 working electrode 11, and a potential of the working electrode 11. Is a constant potential electrolytic gas sensor X provided with a reference electrode 13 that controls the electrolyte solution accommodating portion 31 of the electrolytic cell 30 that accommodates the electrolyte solution 20. Between the electrode 13, an electrolyte permeable filter 50 that does not transmit solid suspended matter but transmits electrolyte 20 is provided.

  The working electrode 11, the counter electrode 12, and the reference electrode 13 are not particularly limited. For example, a paste made of a known electrode material is applied to the surface of a porous gas-permeable film 14 having water repellency and fired. Can be formed. Alternatively, at least one of the working electrode 11 and the counter electrode 12 may be formed of carbon, and the reference electrode 13 may be formed of silver wire. In the present embodiment, the arrangement of the gas electrodes 10 will be described in the case where the working electrode 11, the counter electrode 12, and the reference electrode 13 are arranged to face each other.

  The electrolytic cell 30 forms an opening 32 that opens to the side to form a gas conduction part 33 through which the sample gas is conducted. Two gas permeable membranes 14 are provided. One gas permeable membrane 14 is provided with a working electrode 11, and the other gas permeable membrane 14 is provided with a counter electrode 12 and a reference electrode 13. That is, in this embodiment, the working electrode 11 is provided on the side of the gas conduction part 33 that opens to the side of the electrolytic cell 30, the counter electrode 12 and the reference electrode 13 are opened to the side of the electrolytic cell 30, and the gas conduction. It is provided on the side of the oxygen gas conduction part 35 provided to face the part 33. The oxygen gas conducting part 35 is conducted with an atmosphere gas (oxygen gas).

  The gas permeable membrane 14 disposed on the working electrode 11 side is attached to the electrolytic cell 30 so as to face the opening 32. 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 membrane having chemical resistance can be used. The gas to be detected is introduced from the gas conduction part 33 and reacts on the working electrode 11.

  Each gas permeable membrane 14 is fixed by an O-ring 15 and a lid member 16. An electrolytic solution inlet 34 for performing maintenance such as injection of the electrolytic solution 20 is formed on one surface of the electrolytic bath 30. The electrolytic solution 20 may be an acidic aqueous solution such as sulfuric acid or phosphoric acid, or a neutral salt aqueous solution such as lithium bromide or calcium chloride, but is not limited thereto.

  The electrolyte solution permeable filter 50 is not particularly limited as long as it is disposed between the working electrode 11 and the reference electrode 13 in the electrolyte container 31 and does not transmit solid suspended matter but transmits the electrolyte solution 20. Can be used without The position at which the electrolyte solution permeable filter 50 is disposed may be in any form as long as it is between the working electrode 11 and the reference electrode 13. For example, the electrolyte container 31 may be configured to be separated by the electrolyte permeable filter 50 into a region on the working electrode 11 side and a region on the reference electrode 13 side. Further, the reference electrode 13 may be configured to be covered with the electrolyte solution permeable filter 50.

  As the electrolyte solution permeable filter 50, for example, a semipermeable membrane that allows only molecules or ions having a certain size or less to pass therethrough, a hydrophilic polyethylene-based porous sintered body, or the like can be used. As the polyethylene-based porous sintered body, for example, Sunfine AQ manufactured by Asahi Kasei Chemicals Corporation is suitable.

  In the electrolytic solution storage unit 31, a filter fixing unit 36 for fixing the electrolytic solution permeable filter 50 is provided. The filter fixing portion 36 may be configured to protrude into the electrolyte solution containing portion 31 and be configured to support or adhere and fix the electrolyte solution permeable filter 50 at the protruding portion.

  In the present specification, the term “solid suspended matter” refers to, for example, a precipitate deposited on the gas electrode 10 such as a reference electrode, which is separated from the gas electrode 10 and floats in the electrolyte solution. It shall mean something that may adhere to the surface.

  Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the working electrode 11 by a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the working 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 detection of special material gases for semiconductors such as silane, phosphine, germane, arsine, diborane.

In this embodiment, the working electrode 11 and the counter electrode 12 are carbon electrodes formed of carbon, the reference electrode 13 is a silver electrode formed of silver wire, and the working electrode 11, the counter electrode 12 and the reference electrode 13 are arranged to face each other. The case where the electrolytic solution 20 is a lithium bromide solution (8 mol / L) will be described. With this configuration, for example, diborane, which is used as a semiconductor material gas and has toxicity at an extremely low concentration, can be detected with high accuracy.
In addition, the density | concentration of a lithium bromide solution is not limited to 8 mol / L, What is necessary is just the density | concentration which can detect a desired gas suitably.

  The constant potential electrolytic gas sensor X of the present invention is provided with an electrolyte permeable filter 50 that does not transmit solid suspended matter but transmits electrolyte 20 between the working electrode 11 and the reference electrode 13 in the electrolyte container 31. Therefore, even if the deposit deposited on the reference electrode 13 is detached from the reference electrode 13 and floats in the electrolyte solution 20, the solid suspension in which the deposit floats is removed by the electrolyte permeation filter 50. It is possible to prevent movement to the working electrode 11 side. As a result, since the solid suspended matter can be prevented from adhering to the surface of the working electrode 11, it is possible to prevent the indicator current from flowing excessively to the working electrode 11 due to the solid suspended matter adhering. . Therefore, the constant potential electrolysis gas sensor X of the present invention can accurately detect the actual gas concentration.

[Another embodiment 1]
In the above-described embodiment, the arrangement of the gas electrodes 10 has been described with respect to the case where the working electrode 11, the counter electrode 12 and the reference electrode 13 are arranged to face each other. The counter electrode 12 and the reference electrode 13 may be arranged linearly (FIG. 2).
Also in this case, the electrolytic solution permeable filter 50 is disposed between the working electrode 11 and the reference electrode 13.

[Another embodiment 2]
In the embodiment described above, in order to fix the electrolyte solution permeable filter 50, the filter fixing portion 36 that protrudes inside the electrolyte solution housing portion 31 is provided, but this filter fixing portion 36 protrudes inside the electrolyte solution housing portion 31. It is not necessary to constitute so. In this case, the electrolyte solution permeable filter 50 can be bonded and fixed to the inner wall of the electrolyte container 31.

  The present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. It can utilize for the constant potential electrolytic gas sensor provided facing the accommodating part.

X Constant Potential Electrolytic Gas Sensor 10 Gas Electrode 11 Working Electrode 12 Counter Electrode 13 Reference Electrode 20 Electrolyte 30 Electrolyzer 31 Electrolyte Container 50 Electrolyte Permeation Filter

Claims (4)

As a gas electrode for detecting gas, a working electrode for electrochemically reacting a gas to be detected, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode are faced to an electrolytic solution housing part of an electrolytic cell containing an electrolytic solution. A constant potential electrolytic gas sensor provided in
In the electrolyte container, an electrolyte solution permeable filter that does not transmit solid suspended matter but transmits the electrolyte solution is provided between the working electrode and the reference electrode .
A potentiostatic gas sensor comprising a filter fixing part configured to protrude into the electrolyte container and fixing the electrolyte permeable filter .   The working electrode is provided on the side of the gas conduction part that opens to the side of the electrolytic cell, and the reference electrode is opened to the side of the electrolytic cell and is provided to face the gas conduction part. The constant potential electrolysis gas sensor according to claim 1, which is provided on the introduction port side.   The constant potential electrolytic gas sensor according to claim 1 or 2, wherein at least one of the working electrode and the counter electrode is a carbon electrode, the reference electrode is a silver electrode, and the electrolytic solution is a lithium bromide solution.   The constant potential electrolytic gas sensor according to any one of claims 1 to 3, wherein the gas to be detected is diborane.

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